UK*TE Dec 21 Flashcards

Question

29. A 54 year old man with rheumatoid arthritis undergoes flexion-extension cervical radiographs that show evidence of atlanto-axial subluxation. This is usually related to destruction of which spinal ligament? a. Alar ligament b. Anterior longitudinal ligament c. Apical ligament d. Posterior longitudinal ligament e. Transverse ligament

Answer 1

Answer: E Transverse ligament – due to pannus formation

Answer 2

Answer: A Cavovarus foot is a common condition, seen in both paediatric and adult population, caused by either neurologic (67%( or traumatic disorder, and presents with a cavus arch and hindfoot varus. Deformity is characterised by: - Cavus (elevated longitudinal arch) - Plantarflexion of 1st ray and pronated forefoot - Hindfoot varus - Forefoot adduction Bilateral is most commonly due to Charcot Marie Tooth Disease. Muscle imbalances generate the deformity: - Weak tibialis anterior and peroneus brevis overpowered by strong peroneus longus and posterior tibialis. This results in a plantarflexed 1st ray and forefoot pronation with compensatory hindfoot varus. - With the 1st metatarsal plantarflexed and forefoot pronated, the medial forefoot strikes the ground first. - The subtalar joint supinates to bring the lateral forefoot to the ground and maintain 3-point contact, resulting in hindfoot varus. - While initially flexible, hindfoot varus can become rigid with time. Other conditions that present with a cavovarus foot: Charcot marie Tooth disease, Cerebral Palsy, Friedrich’s ataxia, spinal cord lesions, polio, amniotic band syndrome. History: - Recurrent ankle sprains and lateral ankle pain (peroneal tendon pathology) - Lateral foot pain: excessive weight bearing by the lateral foot due to deformity (can result in 5th MT stress fractures. - Painful plantar calluses under 1st MT head and 5th MT head or base. - Plantar fasciitis (elevated medial arch, forefoot pronation and tight gastrocnemius lead to contracture of plantar fascia Coleman Block Test: Evaluates flexibility of hindfoot deformity. - Place 1inch block under the lateral foot (eliminates contribution of the plantarflexed 1st ray and forefoot pronation to the hindfoot deformity) - A flexible hindfoot will correct to neutral or valgus when block placed under lateral aspect of foot. Rigid hindfoot will not correct to normal. Answer: used to differentiate a flexible from rigid pes cavovalgus deformity – VARUS!!!

Answer 3

Answer: B Nerve root anatomy key differences between cervical and lumbar spine are pedicle/nerve root mismatch cervical spine C6 nerve root travels above C6 pedicle (mismatch) lumbar spine L5 nerve root travels under L5 pedicle (match) extra C8 nerve root (no C8 pedicle) allows transition horizontal (cervical) vs. vertical (lumbar) anatomy of nerve root because of vertical anatomy of lumbar nerve root, a paracentral and foraminal disc will affect different nerve roots, whereas in the cervical spine both foraminifera and central discs will affect the same nerve root C4 radiculopathy scapular winging numbness and pain at the base of the neck C5 radiculopathy deltoid and biceps weakness diminished biceps reflex pain and numbness in the superior shoulder and lateral upper arm C6 radiculopathy brachioradialis and wrist extension weakness diminished brachioradialis reflex paresthesias in the thumb and radial arm C7 radiculopathy triceps and wrist flexion weakness diminished triceps reflex paresthesia in the middle finger most commonly affected nerve root in cervical radiculopathy in several studies C8 radiculopathy weakness to distal phalanx flexion of middle and index finger (difficulty with fine motor function) paresthesias in ring and little finger C8 radiculopathy is extremely rare and often manifests similarly as ulnar neuropathy T1 radiculopathy intrinsic hand muscle weakness axillary numbness ipsilateral Horner's syndrome because of horizontal anatomy of cervical nerve root, a central and foraminal disc will affect the same nerve root

Answer 4

Answer: B Pathological scoliosis is a form of scoliosis resulting from a benign bone tumour, most commonly located in the posterior elements of the spine. Causes: - Osteoid osteomas: occur in the apex of the concavity of the curve, curves are typically rigid, can occur in the vertebral body or posterior elements o XR cortical thickening radiolucent nidus (osteoid osteoma <2cm in diameter, osteoblastoma > 2cm) - Osteoblastomas: larger lesion than osteoid osteoma, pain is usually less severe than osteoid osteoma (less relief with anti-inflammatories) Scoliosis is thought to develop in response to painful paraspinal muscle spasms. Surgical management only indicated in painful, progressive scoliosis. Answer: Anastomosing trabeculae with osteoblastic rimming (osteoid osteoma)

Answer 5

Answer: B A t-test is any statistical hypothesis test in which the test statistic follows a Student's t-distribution under the null hypothesis. It is most commonly applied when the test statistic would follow a normal distribution if the value of a scaling term in the test statistic were known. Two-sample t-test is used when the data of two samples are statistically independent, while the paired t-test is used when data is in the form of matched pairs.

Answer 6

Answer: C Cell differentiation cartilage is formed from mesenchymal stem cells designated towards the cartilagenous lineage multi-step process involving activation and migration of cells to necessary sites SOX-9 is a key transcription factor involved in the differentiation of cells towards the cartilage lineage Cell biology endochondral bone formation occurs with a cartilage model chondrocytes produce cartilage which is absorbed by osteoclasts osteoblasts lay down bone on cartilaginous framework (bone replaces cartilage, cartilage is not converted to bone) forms primary trabecular bone bone deposition occurs on metaphyseal side type X collagen associated with endochondral ossification Molecular biology chondrocytes play a critical role in endochondral bone formation throughout the formation of the cartilage intermediate transcription factors involved in regulation of chondrocytes include Sox-9 considered a major regulator of chondrogenesis, regulates several cartilage-specific genes during endochondral ossification, including collagen types II, IV, and XI and aggrecan PTHrP delays differentiation of chondrocytes in the zone of hypertrophy

Answer 7

Answer: D medial displacement calcaneal osteotomy (MDCO) used in stage IIA (insignificant forefoot abduction) Flexible Pes Planovalgus, also known as Flexible Flatfoot, is a common idiopathic condition, caused by ligamentous laxity that presents with a decrease in the medial longitudinal arch, a valgus hindfoot and forefoot abduction with weight-bearing. Diagnosis can be made clinically with a foot that is flat with standing and reconstitutes with toe walking, hallux dorsiflexion, or foot hanging. Treatment is usually observation, and stretching with majority of cases resolving over time. Rarely, surgical management is indicated for patients with progressive deformities that do not resolve with nonoperative management. Symptoms usually asymptomatic in children may have arch pain or pretibial pain Physical exam inspection: foot is only flat with standing and reconstitutes with toe walking, hallux dorsiflexion, or foot hanging valgus hindfoot deformity forefoot abduction Differential Tarsal coalition Congenital vertical talus Accessory navicular Posterior Tibial Tendon Insufficiency is the most common cause of adult-acquired flatfoot deformity, caused by attenuation and tenosynovitis of the posterior tibial tendon leading to medial arch collapse. Diagnosis can be made clinically with loss of medial arch of the foot which may progress to hindfoot valgus, forefoot abduction and subsequent development of midfoot osteoarthritis. Treatment is nonoperative with orthotics and ankle braces in early stages. A variety of surgical options are available and indicated for progressive and rigid deformities, subtalar or midfoot arthritis, and failure of nonoperative management. Pathoanatomy early disease early tenosynovitis progresses to PTTI leads to loss of medial longitudinal arch dynamic stabilization late disease PTTI contributes to attritional failure of static hindfoot stabilizers and collapse of the medial longitudinal arch spring ligament complex (e.g., superomedial calcaneonavicular ligament) plantar fascia plantar ligaments fixed degenerative joint changes occur at late stages foot deformity pes planus hindfoot valgus forefoot varus forefoot abduction Associated conditions inflammatory arthropathy tarsal coalition young person with rigid pes planus and/or recurrent ankle sprains tibialis posterior originates from posterior fibula, tibia, and interosseous membrane innervated by tibial nerve (L4-5) Tendon posterior tibial tendon (PTT) lies posterior to the medial malleolus before dividing into 3 limbs anterior limb inserts onto navicular tuberosity and first cuneiform middle limb inserts onto second and third cuneiforms, cuboid, and metatarsals 2-4 posterior limb inserts on sustentaculum tali anteriorly Biomechanics PTT lies in an axis posterior to the tibiotalar joint and medial to the axis of the subtalar joint functions as a primary dynamic support for the arch acts as a hindfoot invertor adducts and supinates the forefoot during stance phase of gait acts as secondary plantar flexor of the ankle major antagonist to PTT is peroneus brevis activation of PTT allows locking of the transverse tarsal joints creating a rigid lever arm for the toe-off phase of gait

Answer 8

Answer: E Bone metabolism is a dynamic process that balances bone formation and bone resorption central to this process is the RANK/RANKL/OPG pathway bone formation performed by stimulating osteoblasts and inhibiting osteoclasts bone resorption performed by active osteoclast stimulated by RANKL in normal process stimulated by PTHrP in pathologic process (metastatic disease) Osteoblasts produce RANKL binds RANK and stimulates osteoclastic bone resorption osteoprotegerin (OPG) inhibits osteoclast differentiation, fusion, and activation decoy receptor produced by osteoblasts and stromal cells that binds to and sequesters RANKL alkaline phosphatase Osteoclast Inhibition decreases bone resorption Molecules that inhibit bone resorption osteoprotegerin (OPG) calcitonin interacts directly with the osteoclast via cell-surface receptors estrogen (via decrease in RANKL) stimulates bone production (anabolic) and prevents resorption inhibits activation of adenylyl cyclase transforming growth factor beta (TGF beta) (via increase in OPG) interleukin 10 (IL-10) suppresses osteoclasts Osteoclast activation stimulates bone resorption Molecules that stimulate bone resorption RANKL RANKL (ligand) is secreted by osteoblasts and binds to the RANK receptor on osteoclast precursor and mature osteoclast cells PTH activation of its receptor stimulates adenylyl cyclase binds to cell-surface receptors on osteoblasts to stimulate production of RANKL and M-CSF interleukin 1 (IL-1) stimulates osteoclast differentiation and thus bone resorption 1,25 dihydroxy vitamin D stimulates RANKL expression prostaglandin E2 activates adenylyl cyclase and stimulates resorption IL-6 (myeloma) MIP-1A (myeloma) Osteoporosis can result from loss of function of the OPG gene, leading to constitutive activation of osteoclasts which results in uncontrolled bone resorption and ultimately leads to osteoporosis Osteopetrosis condition caused by a genetic defect resulting in absence of osteoclastic bone resorption a mouse RANKL knockout model creates a osteopetrosis-like condition Paget disease felt to be caused by alterations in cytoplastmic binding to RANK or mutations in the OPG gene Osteolytic bone metastasis found to be mediated by the RANK and RANKL pathway RANKL is produced directly by the cancer cells blocking of RANKL by OPG results in decreased skeletal metastasis in animal models bisphosphonates decrease skeletal events in cancer metastasis Osteolysis following joint arthroplasty polyethylene wear debris is phagocytized by macrophage leads to activation of the macrophage additional macrophages are recruited with release of additional cytokines including RANKL RANKL activates osteoclasts which leads to bone resorption around implants

Answer 9

Answer: D One gait cycle is measured from heel-strike to heel-strike consists of stance phase period of time that the foot is on the ground ~60% of one gait cycle is spent in stance during stance, the leg accepts body weight and provides single limb support swing phase period of time that the foot is off the ground moving forward ~40% of one gait cycle is spent in swing the limb advances Stride is the distance between consecutive inital contacts of the same foot with the ground Step is the distance between initial contacts of the alternating feet Stance phase Initial contact (heel strike) definition occurs when foot contacts the ground muscular contractions hip extensors contract to stabilize the hip quadriceps contract eccentrically tibialis anterior contracts eccentrically Loading response (initial double limb support) marks the beginning of the initial double limb stance definition occurs after initial contact until elevation of opposite limb bodyweight is transferred on to the supporting limb muscular contractions ankle dorsiflexors (tibialis anterior) contract eccentrically to control plantar flexion moment quads contract to stabilize knee and counteract the flexion moment (about the knee) Mid-stance (single limb support) initial period of single leg support definition from elevation of opposite limb until both ankles are aligned in coronal plane muscular contractions gluteus medius and calf muscles undergo eccentric contraction Terminal stance (single limb support) definition begins when the supporting heel rises from the ground and continues until the opposite heel touches the ground muscular contractions toe flexors and tibialis posterior contract and are the most active during this phase Pre-swing (second double limb support) is the start of the second double limb stance in the gait cycle definition from initial contact of opposite limb to just prior to elevation of ipsilateral limb muscular contractions hip flexors contract to propel advancing limb Swing phase Initial swing (toe off) start of single limb support for opposite limb definition from elevation of limb to point of maximal knee flexion muscular contractions hip flexors concentrically contract to advance the swinging leg Mid-swing (foot clearance) definition following knee flexion to point where tibia is vertical muscular contractions ankle dorsiflexors contract to ensure foot clearance Terminal swing (tibia vertical) definition from point where tibia is vertical to just prior to initial contact muscular contractions hamstring muscles decelerate forward motion of thigh Center of gravity (COG) in standing position is 5cm anterior to S2 vertebral body

Answer 10

Answer: E Basic definitions load = a force that acts on a body stress intensity of an internal force calculation force / area units Pascal's (Pa) or N/m2 strain relative measure of the deformation of an object calculation : change in length / original length units none Mechanical property definitions elastic deformation reversible changes in shape to a material due to a load material returns to original shape when load is removed plastic deformation irreversible changes in shape to a material due to a load material DOES NOT return to original shape when load is removed toughness definition amount of energy per volume a material can absorb before failure (fracture) calculation area under the stress/strain curve units joules per meter cubed, J/m3 creep increased load deformation with time under constant load load relaxation decrease in applied stress under conditions of constant strain hysteresis (energy dissipation) characteristic of viseoelastic materials where the loading curve does not follow the unloading curve the difference between the two curves is the energy that is dissipated finite element analysis breaking up a complex shape into triangular or quadrilateral forms and balancing the forces and moments of each form to match it with its neighbor Elastic zone the zone where a material will return to its original shape for a given amount of stress "toe region" applies to a ligaments stress/strain curve represents straightening of the crimped ligament fibrils Yield point the transition point between elastic and plastic deformation Yield strength the amount of stress necessary to produce a specific amount of permanent deformation Plastic zone the zone where a material will not return to its orginal shape for a given amount of stress Breaking point the object fails and breaks Ultimate (Tensile) strength defined as the load to failure Hooke's law when a material is loaded in the elastic zone, the stress is proportional to the strain Young's modulus of elasticity measure of the stiffness (ability to resist deformation) of a material in the elastic zone calculated by measuring the slope of the stress/strain curve in the elastic zone a higher modulus of elasticity indicates a stiffer material Brittle material a material that exhibits linear stress stain relationship up until the point of failure undergoes elastic deformation only, and little to no plastic deformation examples PMMA ceramics Ductile Material undergoes large amount of plastic deformation before failure example metal Viscoelastic material a material that exhibits a stress-strain relationship that is dependent on duration of applied load and the rate by which the load is applied (strain rate) a function of the internal friction of a material examples ligaments bone Isotropic materials possess the same mechanical properties in all directions example golf ball Anisotropic materials possess different mechanical properties depending on the direction of the applied load examples ligaments bone

Answer 11

Answer: D Axonal reaction / central chromatolysis / Wallerian degeneration: When the axon of a neuron is cut or damaged, the axon and its myelin sheath undergo degeneration distal to the lesion (Wallerian degeneration). The sequence of events that takes place in the cell body is known as central chromatolysis or axonal reaction.

Answer 12

Answer: C Becker Muscular Dystrophy - similar to DMD in that sex linked recessive, calf pseudo hypertrophy present, elevated CK, but differs in that dystrophin is decreased rather than absent, later onset in life with a longer life expectancy, more prone to cardiomyopathy. DMD = dystrophin absence, young males only, dystrophin absence leads to poor muscle fibre regeneration and progressive replacement of muscle tissue with fibrous and fatty tissue, therefore skeletal and cardiac muscle lose elasticity and strength. X-linked recessive Xp21.2 dystrophin gene defect (point deletion, third spontaneous mutations) Ortho manifestations: calf pseudo hypertrophy, scoliosis, equinovarus foot deformity, joint contractures. Non-ortho manifestations: cardiomyopathy, static encephalopathy Progressive weakness affecting proximal muscles first (begins with gluteal muscle weakness), gait abnormalities, delayed walking, toe walking, clumsy, waddling gait, difficulty climbing stairs, hopping, jumping, decreased motor skills. Present deep tendon reflexes (unlike SMA), lumbar lordosis (to compensate for gluteal weakness), Gower's sign (rises by walking hands up legs to compensate for gluteus maximus and quads weakness), trendelenberg sign. Muscle biopsy - absent dystrophin, connective tissue infiltration and foci of necrosis. CK leaks across defective cell membrane. DNA testing - absent dystrophin. EMG_ myopathic - decreased amplitude, short duration, polyphasic motor. Differentiation DMD vs SMA: similarities are proximal weakness, but SMA onset earlier in children, deep tendon reflexes and fasciculations are absent. Normal CK levels. No pseudo hypertrophy Differentiation DMD vs Emery-Dreifuss Dystrophy: similar clinical picture but no calf pseudo hypertrophy, Near normal CK levels, early development of elbow and ankle contractures. Friedreichs Ataxia: inherited disorder leading to spinocerebellar degeneration AR mutation in Frataxin gene. Presentation: ataxia, cardiomyopathy, motor weakness, cavovarus foot, scoliosis Dx: genetic testing - absence of frataxin gene (mitochondrial protein GAA repeat at 9q13) Classic triad - ataxia, areflexia, positive plantar response. Nystagmus, cavovarus foot (high arch, rigid deformity, claw toes), scoliosis. Usually wheelchair bound by 30, die from cardiomyopathy by 50. Charcot Marie Tooth - peroneal muscular atrophy AD hereditary motor sensory neuropathy. PMP22 (expressed in Schwann cells) Chr 17 - may also be AR or X-linked. Abnormal peripheral myelin protein - presents with muscle weakness and sensory changes that lead to cavovarus feet, scoliosis and claw foot deformity. Dx: NCS - low velocities , prolonged distal latencies in perineal, ulnar and median nerves. Most common inherited progressive peripheral neuropathy. HMSN Type I: abnormal myelin sheath protein -> combo motor and sensory disturbances. HMSN Type II: ntact myelin sheath with wallerian axonal degeneration that results in mild sensory and motor conduction velocities. Weakness : - profound peroneus brevis first (leading to imbalance and varus deformity) - tib ant (leading to foot drop) - intrinsic muscles hand and foot (wasting 1st dorsal interosseous in hands) - Unopposed pull of peroneus longus and tib post -> plantar flexion first ray and compensatory hind foot varus, initially flexible then becomes rigid. Coleman block test: to determine if hind foot varus is secondary to plantar flexed 1st ray vs independent component - if corrects with coleman block then varus is forefoot driven, if does not correct suggest hind foot driven varus deformity. Rigid hind foot will not correct to neutral.

Answer 13

Answer: C DMD = dystrophin absence, young males only, dystrophin absence leads to poor muscle fibre regeneration and progressive replacement of muscle tissue with fibrous and fatty tissue, therefore skeletal and cardiac muscle lose elasticity and strength. X-linked recessive Xp21.2 dystrophin gene defect (point deletion, third spontaneous mutations) Ortho manifestations: calf pseudo hypertrophy, scoliosis, equinovarus foot deformity, joint contractures. Non-ortho manifestations: cardiomyopathy, static encephalopathy Progressive weakness affecting proximal muscles first (begins with gluteal muscle weakness), gait abnormalities, delayed walking, toe walking, clumsy, waddling gait, difficulty climbing stairs, hopping, jumping, decreased motor skills. Present deep tendon reflexes (unlike SMA), lumbar lordosis (to compensate for gluteal weakness), Gower's sign (rises by walking hands up legs to compensate for gluteus maximus and quads weakness), trendelenberg sign. Muscle biopsy - absent dystrophin, connective tissue infiltration and foci of necrosis. CK leaks across defective cell membrane. DNA testing - absent dystrophin. EMG_ myopathic - decreased amplitude, short duration, polyphasic motor. Differentiation DMD vs SMA: similarities are proximal weakness, but SMA onset earlier in children, deep tendon reflexes and fasciculations are absent. Normal CK levels. No pseudo hypertrophy Differentiation DMD vs Emery-Dreifuss Dystrophy: similar clinical picture but no calf pseudo hypertrophy, Near normal CK levels, early development of elbow and ankle contractures. Friedreichs Ataxia: inherited disorder leading to spinocerebellar degeneration AR mutation in Frataxin gene. Presentation: ataxia, cardiomyopathy, motor weakness, cavovarus foot, scoliosis Dx: genetic testing - absence of frataxin gene (mitochondrial protein GAA repeat at 9q13) Classic triad - ataxia, areflexia, positive plantar response. Nystagmus, cavovarus foot (high arch, rigid deformity, claw toes), scoliosis. Usually wheelchair bound by 30, die from cardiomyopathy by 50. Charcot Marie Tooth - peroneal muscular atrophy AD hereditary motor sensory neuropathy. PMP22 (expressed in Schwann cells) Chr 17 - may also be AR or X-linked. Abnormal peripheral myelin protein - presents with muscle weakness and sensory changes that lead to cavovarus feet, scoliosis and claw foot deformity. Dx: NCS - low velocities , prolonged distal latencies in perineal, ulnar and median nerves. Most common inherited progressive peripheral neuropathy. HMSN Type I: abnormal myelin sheath protein -> combo motor and sensory disturbances. HMSN Type II: ntact myelin sheath with wallerian axonal degeneration that results in mild sensory and motor conduction velocities. Weakness : - profound peroneus brevis first (leading to imbalance and varus deformity) - tib ant (leading to foot drop) - intrinsic muscles hand and foot (wasting 1st dorsal interosseous in hands) - Unopposed pull of peroneus longus and tib post -> plantar flexion first ray and compensatory hind foot varus, initially flexible then becomes rigid. Coleman block test: to determine if hind foot varus is secondary to plantar flexed 1st ray vs independent component - if corrects with coleman block then varus is forefoot driven, if does not correct suggest hind foot driven varus deformity. Rigid hind foot will not correct to neutral.

Answer 14

Answer: B Osteochondral Lesions of the Talus are focal injuries to the talar dome with variable involvement of the subchondral bone and cartilage which may be caused by a traumatic event or repetitive microtrauma. Diagnosis can be made with plain ankle radiographs. MRI studies are helpful in determining the size of the lesion, the extent of bony edema, and identify unstable lesions. Treatment can be nonoperative or operative depending on patient age, patient activity demands, lesion size, and stability of lesion. mechanism of injury ankle inversion and dorsiflexion during axial load creates shearing of lateral talar dome and lateral OLT ankle inversion, external rotation, and plantarflexion during axial load creates shearing of medial talar dome and medial OLT pathophysiology possible repeitive microtrauma creates ischemic environment and loss of integrity of subchondral bone leads to softening and disruption of overlying cartilage Associated conditions cavus hindfoot alignment Relies on extra-osseous blood supply: deltoid artery supplies majority of talar body and dome Typical history: inversion ankle sprain Causes pain centred over ankle joint, joint effusion, mechanical; symptoms (catching or locking). Motion is often limited due to pain or effusion. XRs: often normal, sometimes subtle lucency or bone fragmentation. Non-op: acute injury, non-displaced fragment with incomplete fracture. Arthroscopy, removal fragment, debridement & marrow stimulation: chronic lesions, size <1cm, displaced small fragment with minimal bone on the osteochondral fragement (poor healing potential) Retrograde drilling and/or bone grafting: size >1cm with intact cartilage cap Osteochondral grafting (autograft transplant, autologous chondrocyte implantation, bulk allograft): size >1cm, displaced lesions, shoulder lesions, salvage for failed marrow stimulation or drilling. CI in diffuse ankle arthritis, bipolar kissing lesions, advanced osteonecrosis of taller dome.

Answer 15

Answer: D Peroneal Tendon Tears and Instability represent a spectrum of traumatic injuries to the lateral ankle that include tenosynovitis, tendinopathy, tendon tears and/or tendon instability. Diagnosis is made clinically with subfibular ankle pain with the sensation of apprehension or subluxation with active dorsiflexion and eversion against resistance. MRI studies can help identify the size of peroneal tendon tear and identify concomitant injuries to nearby structures. Treatment may be nonoperative or operative depending on patient activity demands, chronicity of injury, and peroneal instability. mechanism of injury rapid forced dorsiflexion of the inverted foot will cause strain through the contracted peroneal muscles, leading to superior peroneal retinaculum (SPR) tear - (most common pattern is longitudinal split tear in the PB) If superior peroneal retinaculum tears, tendons will become unstable and subluxate or completely dislocate. Peroneus brevis (PB) innervated by the superficial peroneal nerve, S1 acts as primary evertor of the foot tendinous about 2-4cm proximal to the tip of the fibula lies anterior and medial to the peroneus longus at the level of the lateral malleolus Peroneus longus (PL) innervated by superficial peroneal nerve, S1 primarily a plantar flexor and foot and first metatarsal can have an ossicle (os peroneum) located within the tendon body near the calcaneocuboid joint Peroneal tendons contained within a common synovial sheath that splits at the level of the peroneal tubercle. The sheath runs in the retromalleolar groove on the fibula. Peroneus brevis is directly posterior to the fibula at the level of the groove. Peroneus longus is directly posterior to peroneus brevis at the level of the groove, which is deepened by a fibrocartilaginous rim (still only about 5 millimeters deep) and covered by superior peroneal retinaculum (SPR). SPR originates from the posterolateral ridge of the fibula and inserts onto the lateral calcaneus (peroneal tubercle). The inferior aspect of the SPR blends with the inferior peroneal retinaculum and is the primary restraint of the peroneal tendons within the retromalleolar sulcus At the level of the peroneal tubercle of the calcaneus: peroneus longus is inferior & peroneus brevis is superior Both tendons covered by inferior peroneal retinaculum Blood supply: supplied by branches of the anterior and posterior tibial arteries via vincula system - entirety of both tendons are vascularized History: feeling a pop with a distinct dorsiflexion ankle injury, feelings of instability in lateral ankle, lateral or posterolateral ankle pain. Swelling posterior to lateral malleolus, cavovarus hind foot alignment, voluntary subluxation of tendons and a 'popping' sound. XR: "Fleck sign' cortical avulsion of the SPR off the distal tip of the lateral malleolus. Plantarflexed first metatarsal and high Meary's angle, indicating cavovarus deformity. Proximal migration of the os peroneum is indicative of peroneus longus rupture. Non-op: all acute PB/PL instability in non-profession athletes. Repair of SPR and deepening retromalleolar groove: acute tendon dislocations in high level athletes who desire a quick return to sport/presence of a longitudinal tear. Groove deepening with soft tissue transfer and/or osteotomy: chronic dislocations with bony abnormalities or incompetent SPR - generally a salvage procedure. Tenosynovectomy and tendon debridement with tubularization: recalcitrant and symptomatic PB/PL tears less than 50-60% of the tendon width Tenodesis of distal and proximal ends of the brevis tendon to the peroneus longus: complex tears of the brevis tendon with multiple longitudinal tears and significant tendinosis (> 50% of the tendon involved) Debridement of both tendons with FHL/FDL transfer: complex tears of both tendons (involving over 50% of tendon substance) with no muscle excursion

Answer 16

Answer: D Sonic Hedgehog (Shh) genes secreted by ZPA, involved with HOX gene expression - anterior-posterior: (radioulnar) growth: anterior (radial) mesoderm expresses ALX4, posterior (ulnar) mesoderm expresses Hox8 the appendicular system forms between the 4-8 weeks of gestation limb bud development - appears to be under the control of fibroblast growth factors (FGF) - enlargement of the limb bud is due to the interaction between the apical ectodermal ridge (AER) and the mesodermal cells in the progress zone. - first identifiable by transvaginal ultrasound at 8 weeks Steps of limb development: - notochord expresses Shh - Shh regulates limb bud formation: limb bud is combination of lateral plate mesoderm and somatic mesoderm growing outwards into ectoderm (called apical ectodermal ridge). Limb bud formed at embryonic stage 12 (26 days after fertilization) - Mesenchyme condenses into preskeletal blastemal at core of limb bud - Chondrification occurs where mesenchyme differentiates into chondrocytes. All upper limb bones are endochondral except distal parts of distal phalanges (membranous). From proximal (humerus, 36 days after fertilization) to distal (distal phalanges, 50 days) Factors required for chondrification: transcription factors – Sox-5, Sox-6, Sox-9 transforming growth factor superfamily – TGF-b, BMP-2 FGF family (receptor mutation leads to acrocephalosyndactyly (Apert syndrome), retinoids, hedgehog gene products, PTHrP, cadherins, WNT5a and WNT7a - Formation of joints requires repression of chondrogenesis at sites of future joints proteins involved – WNT4, WNT14, growth and differentiation factor 5 (also known as cartilage-derived morphogenetic protein 1) shoulder interzone appears at 36 days, hand interzones appear at 47 days Limb patterning Proximodistal : first signaling center to appear is AER controls proximal to distal growth. forms under FGF10 stimulation Removal /defect in AER results in proximal limb truncation - example is central deficiency (cleft hand), another example is radial clubhand (radial dysplasia, absence of radius) FGFs are the signaling molecule. FGFs expressed in AER include FGF4, FGF8, FGF9, and FGF 17 FGF8 expressed earliest and is obligatory for normal limb development FGF4, 9 and 17 are redundant disrupted FGF signalling leads to arrested limb development Anteroposterior second signaling center to appear is ZPA (zone of polarizing activity), along posterior limb bud controls anteroposterior (radioulnar) limb growth signaling molecule is Shh compound (dose dependent) - normal: high concentration of Shh on posterior (ulnar) side for small finger development and low concentration of Shh on anterior (radial) side for thumb development posterior/ulnar side abnormalities - abnormal upregulation of Shh in the ZPA results in polydactly on the ulnar (posterior) side- extent of duplication is dose dependent (higher dose = more replication) - downregulation of Shh (on the posterior/ulnar side) leads to loss of ulnar digits anterior/radial side abnormalities - abnormal upregulation of Shh in the anterior aspect of the limb bud (where Shh concentration is supposed to be low) leads to loss of thumb timing posterior elements (little finger/ulna) are formed EARLY prior to anterior elements which are formed LATE (radius/thumb) disruption of AP patterning will result in loss of later forming elements (radius/thumb) Dorsoventral axis - third signaling center is non-AER limb ectoderm /Wnt signalling center (progress zone, PZ) - dorsal limb ectoderm expresses WNT7a activates Lmx1b (LIM-homeodomain factor) to regulate dorsal patterning WNT7a is responsible for all dorsal features (including nails) ventral ectoderm expresses en-1 (engrailed-1 protein, antagonistic to WNT7a) inhibits WNT7a (and restricts it to dorsal ectoderm) allows ventral limb development

Answer 17

Answer: C Ewing's Sarcoma is a malignant, distinctive small round cell sarcoma associated with a t(11:22) translocation which most commonly occurs in the diaphysis of long bones in patients <25 with regional pain, swelling and fevers. Diagnosis is made with a biopsy showing sheets of monotonous small round blue cells with prominent nuclei and minimal cytoplasm and immunostaining positive for CD99. Treatment is usually neo-adjuvant chemotherapy and limb salvage surgical resection, followed by adjuvant chemotherapy +/- radiation. t(11:22) translocation found in 85-95% of cases leads to the formation of a fusion protein (EWS-FLI1) XR: large distractive lesion in diaphysis or metaphysics with ill-defined, permeative, moth-eaten appearance. Lytic lesion often with variable amounts of new bone formation. Periosteal reaction may give onion skin or sunburst appearance. Large associated soft tissue mass in >80% cases. Elevated ESR, WCC & LDH Histology: monotonous small round blue cells, high nuclei: cytoplasm ratio. May have pseudo-rosettes (circles of cells with necrosis in centre). Immunistaining: CD99 (+ve in 95%), Standard of care: - Chemo (neoadjuvant (8-12 weeks) + adjuvant (6-12 months)) -> surgery - goal is to obtain local control and prevent late recurrence of chemoresistant cells. Wide margins -> improved 5 year survival. +/- adjuvant radioTx - not necessary if margins are adequate and there is a good response to chemo. Indicated if positive post- surgical resection margins or presence of pulmonary mets.

Answer 18

Answer: B Incidence - Primary joint replacement: 1-2% TKA vs. 0.3-1.3% THA - Revision joint replacement: 5-6% TKA vs. 3-4% THA Risk factors: - Immunosuppressant drugs or conditions - Inflammatory arthropathy Lifestyle: morbid obesity, smoking, EtOH, IVDU, poor oral hygiene most common bacterial organism include staphylococcus aureus staphylococcus epidermidis Coagulase-negative Staphylococcus (chronic infections) most common fungal pathogen Candida species (e.g. Candida albicans) Major criteria (diagnosis can be made when 1 major criteria exist) sinus tract communicating with prosthesis pathogen isolated by culture from 2 separate tissue/fluid samples from the affected joint Minor criteria (preoperative diagnosis) The below scores are added together to determine: ≥6 = infected; 2-5= inconclusive; 0-1=not infected Serum Labs Elevated CRP (>10mg/L) or D-dimer (>860ng/mL) - 2 points Elevated ESR (>30mm/h) - 1 point Synovial Fluid Analysis Elevated synovial WBC (>3,000 cells/µl) or Leukocyte Esterase - 3 points Positive alpha-defensin - 3 points most sensitive and specific marker for PJI Elevated synovial PMN (>80%) - 2 points Elevated synovial CRP (>6.9mg/L) - 1 point Inconclusive (inconclusive preop score (2-5) or dry aspiration) Positive histology (>5 PMN per hpf in 5 hpf at x400 magnification (intraoperative frozen section of periprostehtic tissue) - 3 points Purulence in affected joint - 3 points Single positive culture - 2 points Preoperative score + intraoperative score combined Combined score ≥6 = infected; 4-5= inconclusive; 0-3= not infected Nonoperative chronic suppressive antibiotic therapy indications unfit for surgery refuse surgery systemic spread and maintain joint motion with symptomatic relief outcomes 10% to 25% success rate of eradication 8% to 21% complication rate polyethylene exchange with component retention, IV abx for 4-6 weeks indications acute infection (<3 weeks after surgery) acute hematogenous infection (weak literature, ideally <48-72hrs from symptom onset) techniques thorough tissue debridement and irrigation with large-volume of irrigant outcomes 50% to 55% success rate implants must be removed if reinfection documented Dependant of bacteria speciation one-stage replacement arthroplasty indications used more commonly in Europe for infected THA no sinus tract, healthy patient and soft tissue, no prolonged antibiotic use, no bone graft low-virulence organism with good antibiotic sensitivity technique use antibiotic-impregnated cement advantages lower cost and convenience with single procedure earlier mobility disadvantages higher risk of continued infection from residual microorganisms outcomes variable success of 75-100% two-stage replacement arthroplasty indications gold standard for an infected joint >4 weeks after arthroplasty must be medically fit for multiple surgeries requires adequate bone stock requires confirmation of microbial eradication benign clinical exam normal labs (WBC, ESR, and CRP) negative aspiration cultures obtain repeat cultures at least two weeks after planned antibiotic course has been completed techniques (see section below) prosthesis removal, antibiotic spacer, IV antibiotics for 4-6 weeks and delayed reconstruction outcomes bilateral TKA resection arthroplasty followed by 6 weeks of antibiotics and bilateral reimplantation has excellent results at 2-year follow-up early reimplantation within 2 weeks has 35% success rate delayed reimplantation >6 weeks has a 70-90% success rate cementless reimplantation in the hip has better outcomes than cemented resection arthroplasty indications poor bone and soft tissue quality recurrent infections with multi-drug resistant organisms medically unfit for multiple surgeries failure of multiple previous reimplantations elderly nonambulatory patients disadvantages short limb, poor function, and patient dissatisfaction technique remove all infected tissue and components with no subsequent reimplantation outcomes total knee success rate is 50% to 89% total hip success rate is 60% to 100% arthrodesis indications reimplantation is not feasible due to poor bone stock recurrent infections with virulent organisms outcomes 71% to 95% success rate with bony fusion and infection eradication Amputation total knee infections recalcitrant to other options severe pain, soft tissue compromise, severe bone loss, or vascular damaged AKA

Answer 19

Answer: B Scaphoid Lunate Advanced Collapse (SLAC) describes the specific pattern of degenerative arthritis seen in chronic dissociation between the scaphoid and lunate. chronic SL ligament injury creates a DISI deformity scaphoid is flexed and lunate is extended as scapholunate ligament no longer restrains this articulation scapholunate angle > 70 degrees lunate extended > 10 degrees past neutral resultant scaphoid flexion and lunate extension creates abnormal distribution of forces across midcarpal and radiocarpal joints malalignment of concentric joint surfaces initially affects the radioscaphoid joint and progresses to capitolunate joint notably the radiolunate joint is spared Watson Classification: I: Arthritis between scaphoid and radial styloid -> Radial styloidectomy // PIN, AIN denervation (can be combined with any treatments for II or III) II: Arthritis between scaphoid and entire scaphoid facet of the radius --> proximal row carpectomy (CI if caputolunate arthritis or incompetent radioscapholunate ligament) then scaphoid excision & 4-corner fusion III: Arthritis between capitate and lunate --> 4-corner fusion or wrist fusion (any form of pan carpal arthritis). N.B. Radiolunate joint is spared. Theoretical Type IV in which there is pan carpal arthritis with radiolunate joint affected.

Answer 20

Answer: B Percutaneous release of A1 pulley has >90% success rate Trigger Finger (trigger thumb when involving the thumb) is the inhibition of smooth tendon gliding due to mechanical impingement at the level of the A1 pulley that causes progressive pain, clicking, catching, and locking of the digit. Diagnosis is made by physical examination with presence of active triggering and tenderness at the A1 pulley. Treatment consists of splinting, anti-inflammatory medications, steroid injections, and surgical release. Risk factor: diabetes. Associated with carpal tunnel syndrome (>60% patients), RA, calcific tendinitis, septic tenosynovitis, amyloidosis, hypothyroidism, sarcoidosis, gout, pseudo gout Ring and long fingers most commonly involved in adults. Occurs due to stenosing tenosynovitis at the A1 pulley. Fibrocartilaginous metaplasia of tendon and/or pulley, proliferation chondrocytes, increased type III collagen, chronic hyperglycaemia creates collagen cross-links and impairs collagen degradation. Occasional pathologic nodule of FDP tendon, FDS often unaffected, trigger thumb may have a 4th pulley (variable annular pulley) causing stenosis in up to 75% patients. release of A1 pulley and 1 slip of FDS (usually ulnar slip) indications: persistent/recurrent triggering after A1 pulley release rheumatoid arthritis patients may benefit from FDS slip excision without A1 pulley release pediatric trigger finger presents with Notta's node (proximal to A1 pulley), flexion contracture and triggering surgical treatment at 2-4 years of age to prevent interphalangeal joint contracture may need to release remaining FDS slip and A3 pulley Radial digital nerve injury risk factors - trigger thumb release due to superficial location and oblique orientation treatment: may require digital nerve and artery repair

Answer 21

Answer: C Synovium mediates nutrient exchange between blood and joint fluid - made from a ultrafiltrate of blood plasma synovial fluid exhibits non-Newtonian flow characteristics - the viscosity coefficient is not a constant. The fluid is not linearly viscous viscosity increases as the shear rate decreases Composition vascularized connective tissue is porous and lacks basement membrane cell types type A cells: derived from macrophages, non-fixed cells with antigen presenting ability located in superficial layer and important in phagocytosis type B cells fibroblast like cells rich rough endoplasmic reticulum and dendritic processes that reach out to the joint surface located at various depths, frequently in deeper layer produce synovial fluid (produce hyaluronic acid, fibronectin, collagen) type C cells intermediate cell type unknown function and origin may serve as multi-potent precursor to either type A or B synovial cells

Answer 22

Answer: A Female sex, obesity, and neurological conditions represent patient-related risk factors for dislocation.4-8 Small-sized femoral head components, (28 mm or less) are known to have a higher risk of dislocation compared to THAs using larger femoral heads (32 mm or greater). Incidence 1-3% 70% occur within first month 75-90% posterior Mechanism - anterior: extension and external rotation of hip - posterior: flexion, internal rotation, adduction of hip Risk factors - Prior hip surgery (greatest risk factor) - obesity >70-80 years of age posterior surgical approach repairing capsule and reconstructing external rotators brings dislocation rate close to anterior approach malpositioning of components ideal positioning of acetabular component is 40 degrees of abduction and 15 degrees anteversion in general, excessive anteversion increases risk of anterior hip dislocation; excessive retroversion increases risk of posterior hip dislocation spastic or neuromuscular disease (Parkinson's) drug or alcohol abuse decreased femoral offset (decreases tissue tension and stability) decreased femoral head to neck ratio prior spinal fusion or fixed spinopelvic alignment polyethylene wear common cause of late instability occuring >5 years after procedure Dislocation is one of the most common causes of patient and surgeon dissatisfaction following hip replacement and to treat it, the causes must first be understood. Patient factors include age greater than 70 years, medical comorbidities, female gender, ligamentous laxity, revision surgery, issues with the abductors, and patient education. Surgeon factors include the annual quantity of procedures and experience, the surgical approach, adequate restoration of femoral offset and leg length, component position, and soft-tissue or bony impingement. Implant factors include the design of the head and neck region, and so-called skirts on longer neck lengths. There should be offset choices available in order to restore soft-tissue tension. Lipped liners aid in gaining stability, yet if improperly placed may result in impingement and dislocation. Late dislocation may result from polyethylene wear, soft-tissue destruction, trochanteric or abductor disruption and weakness, or infection. Understanding the causes of hip dislocation facilitates prevention in a majority of instances. Proper pre-operative planning includes the identification of patients with a high offset in whom inadequate restoration of offset will reduce soft-tissue tension and abductor efficiency. Component position must be accurate to achieve stability without impingement. Finally, patient education cannot be over-emphasised, as most dislocations occur early, and are preventable with proper instructions. Cite this article: Bone Joint J 2013;95-B, Supple A:67–9. A history of spinal fusion was the strongest independent predictor of dislocation (odds ratio [OR], 2.45; 95% confidence interval [CI], 1.97-3.04; P < .0001). Parkinson's disease was also significantly associated with dislocation (OR, 1.63; 95% CI, 1.05-2.51; P = .03), as well as dementia (OR, 1.96; 95% CI, 1.13-3.39; P = .02), depression (OR, 1.28; 95% CI, 1.13-1.43; P < .0001), and chronic lung disease (OR, 1.2; 95% CI, 1.07-1.33; P = .001). Inflammatory arthritis and avascular necrosis were independent risk factors for dislocation (OR, 1.56; 95% CI, 1.25-1.97; P < .0001; OR, 1.67; 95% CI, 1.45-1.93; P < .0001).

Answer 23

Answer: E - Osteopetrosis is either AD (1/20,000) or AR (1/200,000) Benign AD is commonest form - usually asymptomatic AR forms - frequent fractures, progressive deafness and blindness, severe anaemia, bleeding risk, frequent infections. OM of mandible, dental abscesses, hepatosplenomegaly. Osteopetrosis is a congenital metabolic bone disease caused by defective osteoclastic resorption of immature bone that presents with increased frequency of long bone fractures, cranial nerve palsies, and low back pain. Diagnosis is made radiographically with increased cortical thickening, increased overall bone density, and loss of medullary canal diameter. Treatment is multidisciplinary approach to address fracture management, and cranial nerve abnormalities. Caused by osteoclast inability to acidify Howships lacuna (defective carbonic anhydrase II or chloride channel dysfunction) - leads to predisposition to fracture (lower>>upper>>axial skeleton) lack ruffled border and clear zone, islands of calcified cartilage with mature trabeculae Associated with: - CN palsies (overgrowth of skull foramina) optic n> auditory n> trigeminal n> facial n. - osteomyelitis (lack of marrow vascularity -> impaired WBC function) - Increased prevalence spondylolysis - Coxa vara - often due to fem neck fracture non-union or repeated stress fractures. - Carpal tunnel syndrome

Answer 24

Answer: C Damage control orthopaedics: definitive treatment delayed until physiology has improved Parameters that help decide who should be treated with DCO ISS >40 (without thoracic trauma) ISS >20 with thoracic trauma GCS of 8 or below lactate >4 multiple injuries with severe pelvic/abdominal trauma and hemorrhagic shock bilateral femoral fractures pulmonary contusion noted on radiographs hypothermia <35 degrees C head injury with AIS of 3 or greater IL-6 values above 500pg/dL Optimal time of surgery patients are at increased risk of ARDS and multisystem failure during the acute inflammatory window (period from 2 to 5 days characterized by a surge in inflammatory markers) therefore only potentially life-threatening injuries should be treated in this period including unstable pelvic fracture compartment syndrome fractures with vascular injuries unreduced dislocations traumatic amputations unstable spine fractures cauda equina syndrome open fractures Trauma is a major public health problem with high disability, death, and societal cost Three peak times of death after trauma 50% within the first minutes of sustaining the injury caused by massive blood loss or neurologic injury 30% within hours of arrival to hospital most commonly from shock, hypoxia, or neurologic injury 20% within days to weeks following injury multi system organ failure and infection are leading causes Golden Hour period of time when life threating and limb threatening injuries should be treated in order to decrease mortality estimated 60% of preventable deaths can occur during this time ranging from minutes to hours

Answer 25

Answer: D XR: double density sign (represents subtalar incongruity), calcaneal shortening, varus tuberosity deformity, decreased Bohlers angle (initial Böhler's angle <0° (these injuries do poorly regardless of treatment) lower Böhler angles suggest greater energy absorbed), increased angle of Gissane Calcaneus fractures are the most common fractured tarsal bone and are associated with a high degree of morbidity and disability. Diagnosis is made radiographically with foot radiographs with CT scan often being required for surgical planning. Treatment is nonoperative versus operative based on fracture displacement and alignment, associated soft tissue injury, and patient risk factors. 17% are open fractures intra-articular fractures traumatic axial loading is the primary mechanism of injury fall from height motor-vehicle accidents calcaneal tuberosity fractures poor bone quality/osteoporosis violent contaction of the triceps surae with forced dorsiflexion strong concentric contaction of the triceps surae with knee in full extension intrinsic tightness of the gastrocnemius and achilles tendon peripheral neuropathy leading to decreased pain sensation and proprioception resulting in recurrent microtrauma calcaneal stress fractures increased physical activity in the setting of relative energy deficiency anterior process fractures twisting injury mechanism avulsion injury of the bifurcate ligament intra-articular fractures primary fracture line results from oblique shear and leads to the following two primary fragments superomedial fragment (constant fragment) includes the sustentaculum tali and is stabilized by strong ligamentous and capsular attachments superolateral fragment includes an intra-articular aspect through the posterior facet secondary fracture lines dictate whether there is joint depression or tongue-type fracture Intra-articular (75%) Essex-Lopresti classification the primary fracture line runs obliquely through the posterior facet forming two fragments the secondary fracture line runs in one of two planes the axial plane beneath the facet exiting posteriorly in tongue-type fractures when the superolateral fragment and posterior facet remain attached to the tuberosity posteriorly behind the posterior facet in joint depression fractures Sanders classification based on the number of articular fragments seen on the coronal CT image at the widest point of the posterior facet extra-articular fractures strong contraction of gastrocnemius-soleus with concomitant avulsion at its insertion site on calcaneus more common in osteopenic/osteoporotic bone. Extra-articular (25%) avulsion injury of anterior process by bifurcate ligament sustentaculum tali calcaneal tuberosity (Achilles tendon avulsion) Surgical management has high risk of wound complications (extensile lateral L-shaped incision is commonest). Lateral calcaneal branch of peroneal artery supplies the full thickness skin, soft tissue and periostea flaps that are developed. Complications: (40% rate) - wound complication - subtalar arthritis - lateral impingement with peroneal irritation - sural nerve neuroma - Damaged FHL - compartment syndrome - malunion

Answer 26

Answer: E Talar neck fractures are high energy injuries to the hindfoot that are associated with a high incidence of talus avascular necrosis. Most common fracture of the talus (50%). Foot is forced dorsiflexed with axial load. Ipsilateral lower extremity fractures are common. Inferior surface articulates with posterior facet of calcaneus. Talar head articulates with navicular bone, sustenaculum tali, navicular bone, sustentaculum tali. Lateral process articulates with posterior facet of calcaneus and lateral malleolus of fibula. Posterior process consists of medial and lateral tubercles separated by groove for FHL. Blood supply - talar neck receives blood supply via 3 sources: - Posterior tibial artery: via artery of tarsal canal (dominant supply - majority of talar body) and by the deltoid branch of PTA (supplies medial portion of talar body - and may be only remaining blood supply with a displaced fracture) - Anterior tibial artery: supplies head and neck - Perforating peroneal artery via artery of tarsal sinus: supplies head and neck Hawkins Classification correlates degree of displacement to AVN risk. I : Non-displaced 0-13% II: Subtalar dislocation 20-50% III: Subtalar and tibiotalar dislocation 20-100% IV: Subtalar, tibiotalar & talonavicular dislocation (70-100%) CT best Ix to determine degree of displacement, comminution and articular congruity. Will also show ipsilateral foot injuries (up to 89% incidence). 'All' cases require emergent closed reduction in ER. ORIF: 2 approaches are recommended to visualise medial and lateral neck to assess reduction - typical areas of comminution are dorsal and medial - Anteromedial: between tib an and posterior tibialis. Preserves soft tissue attachments, especially deep deltoid ligament (blood supply). Medial malleolar osteotomy also preserves deltoid ligament. - Anterolateral: between tibia and fibula proximally, in line with 4th ray - elevate extensor digitorum breves and remove debris from subtalar joint. Anatomic reduction is essential. Consider mini frag plate in comminuted fractures to buttress against varus collapse. Complications: - Osteonecrrosis: 31% overall (including all subtypes) - Hawkins sign is subchondral lucency best seen on mortise Xray at 6-8 weeks and indicates intact vascularity with resorption of subchondral bone - associated with talar neck comminution and open fractures Delayed internal fixation is not associated with avascular necrosis Post traumatic arthritis: subtalar (50%) and tibiotalar (33%) Varus mal-union (25-30%) - can be prevented by anatomic reduction. Leads to decreased subtalar eversion (decreased motion with locked mid foot and hind foot). Weight bearing on the lateral border of the foot. Treatment includes medial opening wedge osteotomy of talar neck.

Answer 27

Answer: D Local recurrence significantly affects the overall survival in patients with a Ewing’s sarcoma. For those with a tumour in a limb, radiotherapy reduced the risk of local recurrence, especially in those with a marginal margin of excision, but the effect in central tumours was less clear. Radiotherapy for those who have had a wide margin of resection does not reduce the risk of local recurrence, regardless of the histological response to chemotherapy. A Ewing’s sarcoma is a small round cell neuro-ectodermal neoplasm. It is the second most common primary bone tumour in children after osteosarcoma.1-3 The combination of neo-adjuvant chemotherapy and excision and/or radiotherapy for local primary control has become the mainstay of treatment for these tumours.4As a result of advances in surgical techniques, limb-salvage surgery is possible for most patients with a Ewing’s sarcoma following resection where appropriate.5,6 However, approximately 10% of patients suffer a local recurrence and the long-term survival for this group of patients remains less than 30%.7-10 There is evidence that surgical margins and the site of the tumour are significant prognostic factors for local recurrence, and the benefits of radiotherapy for reducing local recurrence have been described.11,12 However, the relationship between local recurrence and the response to chemotherapy has not been clearly documented and the role of adjuvant radiotherapy remain less clear. In a recent large multicentre study, postoperative radiotherapy significantly reduced the rate of local recurrence compared with patients not receiving this treatment, and postoperative radiotherapy was recommended in patients with incomplete removal of the tissue as assessed by its volume before chemotherapy

Answer 28

Answer: E Monoclonal Ig2 against RANKL (inhibits binding of RANKL to RANK, like osteoprotegerin) Bone metabolism is a dynamic process that balances bone formation and bone resorption. - Central to this process is the RANK/RANKL/OPG pathway Bone formation: stimulating osteoblasts and inhibiting osteoclasts Bone resorption: performed by active osteoclast - stimulated by RANKL in normal process - stimulated by PTHrP in pathologic process (metastatic disease) Osteoblasts produce: - RANKL: which binds RANK and stimulates osteoclastic bone resorption. - OPG: inhibits osteoclast differentiation, fusion and activation. Acts as a decoy receptor (is a competitive inhibitor of RANKL, and thus blocks it from activating osteoclasts) Osteoclast inhibition decreases bone resorption. Molecules that inhibit bone resorption: - OPG - Calcitonin : interacts directly with osteoclast via cell-surface receptors - Estrogen (via decrease in RANK-L) - stimulates bone production (anabolic) and prevents resorption. Inhibits activation of adenylyl cyclase. - TGF-beta (via increase in OPG) - IL-10: suppresses osteoblasts Osteoclast activation stimulates bone resorption. Molecules that stimulate bone resorption: - RANKL: secreted by osteoblasts and binds to the RANK receptor on osteoclast precursor and mature osteoclast cells. - PTH: activation of its receptor stimulates adenylyl cyclase - binds to cell-surface receptors on osteoblasts to stimulate production of RANKL and M-CSF - IL-1: stimulate osteoclast differention and thus bone resorption. - 1,25 dihydroxy vit D: stimulates RANKL expression - PGE2: activates adenylyl cyclase and stimulates resorption - IL- 6 (myeloma) - MIP-1A (myeloma) Giant Cell Tumors are benign, aggressive tumors typically found in the epiphysis of long bones, most commonly at the distal femur and proximal tibia. Patients typically present between ages 30 and 50 with insidious onset of pain of the involved extremity with activity, at night, or at rest. Diagnosis is made with a biopsy showing mononuclear stromal cells that resemble interstitial fibroblasts with numerous giant cells dispersed throughout. Metastases to lungs in 2-4% cases (wrist and hand lesions have greater chance of mets). XR: eccentric lytic epiphyseal/metaphyseal lesion that often extends into the distal epiphysis and borders subchondral bone "neo-cortex" is characteristic of benign aggressive lesions, and not unique to GCT Medical management - Bisphosphonates: osteclast inhibitors which may decrease the size of the defect in giant cell tumors and help prevent post-surgical recurrence - Denosumab: monoclonal antibody against RANK-ligand recent clinical trials suggest denosumab can decrease the size of the bone defect in giant cell tumor - 85-90% tumor necrosis Shows dramatic sclerosis and reconstitution of cortical bone after treatment. Complications bisphosphonates: esophagitis, gastritis, long term use can lead to atypical subtrochanteric femur fractures denosumb: may cause nasopharyngitis, arthralgias. contraindications: severe hypocalcemia

Answer 29

Answer: C Used in reconstruction of PIPJ pilon fractures

Answer 30

Answer: C Also known as transverse ligament of the palmar aponeurosis - thin band of transverse fibres of the distal portion of the palmar aponeurosis. It runs deep and transverse to the longitudinally oriented pretendinous bands of the palmar fascial complex oblique band (oblique retinacular ligament of Landsmeer) function links motion of DIP and PIP lies volar to axis of PIP, but dorsal to axis of DIP anatomy origin: from lateral volar aspect of proximal phalanx, insertion: to lateral terminal extensor dorsally (crosses collateral ligaments) biomechanics with PIP flexion, ligament relaxes to allow DIP flexion with PIP extension, ligament tights to facilitate DIP extension pathology contracture causes volar displacement of lateral bands and a resulting Boutonniere Deformity reconstruction of oblique retinacular ligament used to treat swan neck deformity if ORL is tight, resting finger position is DIP extended, PIP flexed unable to flex DIP if PIP is extended able to flex DIP only after PIP is flexed contrast this with intrinsic tightness, where there is decreased PIP flexion when the MCP is extended, and improved PIP flexion when the MCP is flexed contrast this with extrinsic tightnes (extensor tendon tightness), where there is increased PIP flexion when MCP is extended, and decreased PIP flexion when MCP is flexed Digital cutaneous ligaments Function tether skin to deeper layers of fascia and bone to prevent excessive mobility of skin and improve grip stabilize the digital neurovascular bundle with finger flexion and extension Anatomic Components Cleland's ligaments (remember "C" for ceiling) dorsal to digital nerves not involved in Dupuytren's disease Grayson's ligament (remember "G" for ground) volar to digital nerves Triangular ligament Function counteracts pull of oblique retinacular ligament, preventing lateral subluxation of the common extensor mechanism Anatomy triangular in shape located on dorsal side of extensor mechanism, distal to PIP joint Pathology contracture leads to swan neck deformity

Answer 31

Answer: D Central slip rupture – Elsons test The common extensor divides at the PIP into a central slip and two lateral bands. If the central slip is avulsed, the lateral bands will be freed, and may migrate volarly to actually become flexors of the finger. This leads to an odd appearance of the finger known as the Boutenniere deformity. Elson’s test is the most well known test to diagnose an injury to the central slip before complications occur. Here’s how it’s done: The patient bends the PIP 90° over the edge of a table and extends the middle phalanx against resistance. In the absence of central slip injury (negative test), extension is strong AND the DIP remains floppy because the extension force is now placed entirely on maintaining extension of the PIP joint, so the lateral bands are not activated. In the presence of central slip injury (positive test) there will be weak PIP extension, AND the DIP will extend abnormally and become rigid.

Answer 32

Answer: C Q angle - line drawn from ASIS through middle of patella to tibial tuberosity. Males: 13 deg Females : 18 deg In flexion: 8 deg Sagittal ROM: 3 deg hyperextension to 155 deg flexion. Normal gait requires ROM 0-70 deg Instant centre of rotation = point at which the joint surfaces are in contact. Posterior rollback - as the knee flexes, the instant centre of rotation on the femur moves posteriorly - allows for increased knee flexion by avoiding impingement. Screw home mechanism: tibial ER 5deg in the last 15deg of extension. Occurs as medial tibial plateau articular surface is longer than lateral tibial plateau. This locks the knee, decreasing the work performed by the quadriceps while standing. Normal anatomy: Distal femur in ~9 degrees of valgus (anatomic axis compared to joint line) 5-7 deg valgus of femur refers to difference of anatomic axis to mechanical axis proximal tibia is 2-3 degrees of varus (anatomic axis to joint line) Technical goals - restore mechanical alignment (mechanical alignment of 0°) - restore joint line ( allows proper function of preserved ligaments. e.g., pcl) - balanced ligaments (correct flexion and extension gaps) - maintain normal Q angle (ensures proper patellar femoral tacking) Mechanical axis of Limb = axis from centre of femoral head to centre of ankle Anatomical axis femur: line that bisects medullary canal femur - determines entry point of femoral medullary guide rod. Femoral Alignment: Mechanical axis femur: line connecting centre of femoral head to point where anatomic axis meets intercondylar notch. Obtaining neutral mechanical axis allows even load sharing between medial and lateral condyles of knee prosthesis. Valgus cut angles: (~5-7° from AAF ) difference between AAF and MAF. Perpendicular to mechanical axis - jig measures 6 deg from femoral guide (anatomic axis) - will vary if people very tall (<5deg) or very short (>7deg). Tibial Alignment: Anatomic axis tibia: line that bisects medullary canal, tibial medullary guide (internal or external) runs parallel to it. Determines entry point for tibial medullary guide rod. Mechanical axis tibia: line from centre of proximal tibia to centre of talus. Proximal tibia is cut perpendicular to mechanical axis of tibia. Usually mechanical axis and anatomic axis of tibia are coincident, and therefore can usually cut the proximal tibia perpendicular to the anatomic axis (determined by intramedullary jig) - If there is tibia deformity and the mechanical and anatomic axis are not the same, then the proximal tibia must be cut perpendicular to the mechanical axis (i.e. use extramedullary tibial guide).

Answer 33

Answer: D <6 months any fracture pattern -> pavlik harness (caution compression of femoral nerve if XS flexion - decreased quadriceps function) or early spica Spica - flex hip 60-90deg and 30 abduction, ER needed to correct a rotational deformity. Mould into recurvatum and valgus as muscular forces typically pull fracture into procurvatum and varus. Goal of reduction: <10deg coronal plane and 20deg sagittal plane deformity, with no more than 2cm shortening or 10 deg rotational malalignment. 6 months - 5 years: traction +/- spica casting - relative contraindication in polytrauma, open fractures TENS: 5-11 years, length stable, <49kgs. Nail size by multiplying width of the isthmus femoral canal by 0.4 (80% canal fill). Entry site 2cm medially and laterally at level of distal physis, starting point 2cm proximal to physis. Pain at insertion site nearest knee is commonest complication. Submuscular plating: If length unstable fracture, >5years, >49kgs, very proximal or distal fractures, severe comminution. Laterally based incision and plating with minimal disruption of soft tissue envelope. Small proximal and distal incisions - plate is placed between periosteum and vastus lateralis on the lateral side of the femur. Typically 12-16 hole 4.5mm narrow LC-DC plate, 3 screw proximal and 3 distal to the fracture - may need contouring. Antegrade rigid intramedullary nail: >11 years, unstable fractures, >49kgs Trochanter or lateral entry nail - avoid piriformis entry due to risk of injury to vascularity of femoral head (1-2% osteonecrosis) External fixator: damage control orthopaedics in polytrauma, open fracture, associated vascular injuries requiring revascularization, segmental or significantly comminuted fractures. Osteology anterior bow to femur isthmus is the narrowest portion of the femur Muscles iliopsoas creates a flexion and external rotation force on the proximal fragment adductors create a shortening and varus force on the distal fragment Biomechanics femoral shaft cortical diameter and cortical thickness increase with age

Answer 34

Answer: D DHS is biomechanically superior to cannulated screws when vertical fracture pattern in a young patient. Has a lower re-operation rate vs cannulated screws in displaced femoral neck fractures, basic-cervical femoral neck fractures and current smokers. Osteology - normal neck shaft-angle 130 +/- 7 degrees - normal anteversion 10 +/- 7 degrees Blood supply to femoral head: major contributor is medial femoral circumflex (lateral epiphyseal artery) - some contribution to anterior and inferior head from lateral femoral circumflex. Also some contribution from inferior gluteal artery. Small and insignificant supply from artery of ligamentum teres Displacement of femoral neck fracture will disrupt the blood supply and cause an intracapsular hematoma. Pauwels Classification: (based on vertical orientation of fracture line) Type I: <30 deg from horizontal Type II: 30-50 deg from horizontal Type III: >50deg from horizontal (most unstable with highest risk of non-union/AVN) Cannulated screw fixation: - Non displaced transcervical fractures - Garden I or II in physiologically elderly - Displaced transcervical fracture in younger patient (achieve reduction to limit vascular insult, must be anatomic so open if necessary) - 3 screws - inverted triangle along calcar configuration shown to be superior to 2 screws - has a stronger fixation and a higher load to failure. Obtain as much screw spread as possible in femoral neck. DHS: - Basi-cervical fracture - Vertical fracture pattern in a younger patient - biomechanically superior to cannulated screws. Consider use of anti-rotation screw. FAITH study. Non-union 5-30% - increased incidence in displaced fractures. No correlation between age, gender and rate of non-union. Varus malreduction most closely correlates with failure of fixation after reduction and cannulated screw fixation. Tx: Valgus intertrochanteric osteotomy - turns vertical fracture line into horizontal fracture line, therefore decreases the shear forces across the fracture. Can be done even in presence of AVN as long as not several collapsed. Free vascularised fibula graft - young patients with a viable femoral head. Arthroplasty: older patients or when femoral head not viable.

Answer 35

Answer: C The obturator nerve was likely to be injured during unprotected osteotomy of the pubis if the far cortex was penetrated by > 5 mm. This could be avoided by inclining the osteotome 45° medially and performing the osteotomy at least 2 cm medial to the iliopectineal eminence. Nerve roots: L2-L4 Motor functions: Innervates the muscles of the medial compartment of the thigh (obturator externus, adductor longus, adductor brevis, adductor magnus and gracilis). Sensory functions: Cutaneous branches of the obturator nerve innervate the skin of the medial thigh. The obturator nerve is formed from the lumbar plexus. It receives fibres from the anterior divisions of L2, L3 and L4. After its formation, the obturator nerve descends through the fibres of the psoas major and emerges from its medial border. It then travels posteriorly to the common iliac arteries and laterally along the pelvic wall – towards the obturator foramen of the pelvis. The obturator nerve enters the medial thigh via the obturator canal (formed within the obturator foramen by the obturator membrane). It then divides into anterior and posterior branches: Anterior division (anterior to the adductor brevis): Descends in a plane between the adductor longus and adductor brevis (towards the femoral artery). Here, it supplies motor fibres to the adductor longus, adductor brevis and gracilis. It can also supply the pectineus muscle. It then pierces the fascia lata to become the cutaneous branch of the obturator nerve. Posterior division (posterior to the adductor brevis): Pierces the obturator externus muscle, and then descends in a plane between the adductor brevis and adductor magnus. Innervates the obturator externus and adductor magnus muscles. Reducing the risk of nerve injury during Bernese periacetabular osteotomy: a cadaveric study The modified Smith-Petersen and Kocher-Langenbeck approaches were used to expose the lateral cutaneous nerve of the thigh and the femoral, obturator and sciatic nerves in order to study the risk of injury to these structures during the dissection, osteotomy, and acetabular reorientation stages of a Bernese peri-acetabular osteotomy. Injury of the lateral cutaneous nerve of thigh was less likely to occur if an osteotomy of the anterior superior iliac spine had been carried out before exposing the hip. The obturator nerve was likely to be injured during unprotected osteotomy of the pubis if the far cortex was penetrated by > 5 mm. This could be avoided by inclining the osteotome 45° medially and performing the osteotomy at least 2 cm medial to the iliopectineal eminence. The sciatic nerve could be injured during the first and last stages of the osteotomy if the osteotome perforated the lateral cortex of ischium and the ilio-ischial junction by > 10 mm. The femoral nerve could be stretched or entrapped during osteotomy of the pubis if there was significant rotational or linear displacement of the acetabulum. Anterior or medial displacement of < 2 cm and lateral tilt (retroversion) of < 30° were safe margins. The combination of retroversion and anterior displacement could increase tension on the nerve. Strict observation of anatomical details, proper handling of the osteotomes and careful manipulation of the acetabular fragment reduce the neurological complications of Bernese peri-acetabular osteotomy. Malfunction of 1 of the 3 major nerves around the hip is a severe surgical complication of periacetabular osteotomy (PAO), and an understanding of the possible impacts of the different steps of the procedure on the nerves in their anatomic vicinity is essential to decrease the risk of these devastating injuries. Step 1: Make a C-Shaped Skin Incision and Osteotomize the Anterior Superior Iliac Spine (ASIS) to Best Protect the LFCN Step 2: Do Not Transect the Psoas Tendon to Enable an Easier Approach to the Ischium and Pubis as It Protects the Femoral Nerve from Being Overstretched. Sectioning the psoas tendon can result in potentially damaging tensioning of the femoral nerve. Step 3: Prevent Injury to the Sciatic Nerve While the Osteotomy of the Ischium Is Being Performed from Anterior. We perform the first ischial cut without direct visual control; fluoroscopy can be used to visualize the position of the osteotomy, but it will not completely eliminate the risk of sciatic nerve injury. Step 4: Protect the Obturator Nerve During Osteotomy of the Pubis The obturator nerve and vessels cross through the obturator foramen inferior to the superior pubic ramus close to the level of the pubic osteotomy; as the nerve is fixed by a membrane in close vicinity to the undersurface of the pubic bone, it may become injured during pubic osteotomy. Step 5: Prevent Injury to the Sciatic Nerve During Supra-Acetabular and Posterior Column (Inside-Out Osteotomy) for Complete Ischial Separation. When performing the supra-acetabular osteotomy, the abductors should be tunneled on the lateral aspect of the pelvis, retracted, and protected by a blunt Hohmann retractor. Step 6: Prevent Femoral Nerve Injuries Resulting from Acetabular Reorientation Most femoral nerve lesions are caused by kinking and overstretching during large acetabular fragment displacement. Step 7: Avoid Sciatic Nerve Injury During Fragment Reorientation Similar to the femoral nerve, the sciatic nerve can potentially be kinked and/or stretched during large displacement of the acetabular fragment; it can also be lanced by a bone spike on the fragment.

Answer 36

Answer: D - the femoral prosthesis should be externally rotated 3 degrees from this axis to produce a rectangular flexion gap Femoral prosthesis There are three reference axis that one may use: - Anteroposterior axis: defined as a line running from the centre of the trochlear groove to the top of the intercondylar notch. A line perpendicular to this defines the neutral rotational axis - Transepicondylar axis: defined as a line running from the medial and lateral epicondyles - the epicondylar axis is parallel to the cut tibial surface. A posterior femoral cut parallel to the epicondylar axis will create the appropriate rectangular flexion gap - Posterior condylar axis: defined as a line running across the tips of the two posterior condyles. This line is in ~ 3 degrees of internal rotation from the transepicondylar axis, the femoral prosthesis should be externally rotated 3 degrees from this axis to produce a rectangular flexion gap. If the lateral femoral condyle is hypoplastic, use of the posterior condylar axis may lead to internal rotation of the femoral component WARNING: the average posterior condylar twist angle is 3º but the range is 1-10º. Therefore vary angle of femoral rotation based on variances in femoral anatomy. Internal Rotation of Femoral Prosthesis will Increase Q angle: by internally rotating the femoral prosthesis, you are effectively bringing the groove and the patella medially. This will increase the Q angle to the tibial tubercle will also make the medial compartment tight in flexion with subsequent TKA stiffness Medialization of the Femoral Prosthesis will Increase Q angle: a medialized femoral prosthesis will bring the trochlear groove to a more medial position, and thus bring the patella medial with it, thus increasing the Q angle therefore, you want the femoral component to be slighly lateral if anything

Answer 37

Answer: D As the Q angle increases from flexion to extension, the tension in the quadriceps and patellar tendons decreases. This occurs because the tibia rotates externally, thus moving the tibial tubercle laterally, in a mechanism known as screw-home. This relationship contributes to greater patellar instability in extension and in small degrees of flexion, causing patellar dislocation. The vastus medialis oblique (VMO) muscle actively acts as a stabilizer, while the medial patellofemoral ligament (MPFL) and the lateral retinaculum are passive stabilizers. Imbalances may occur due to VMO muscle weakening or increased tension in the lateral retinaculum. Although the lateral retinaculum contributes to only 10% of the lateral stability of the patella,12 when under excessive stress it often leads to abnormal contact of the lateral surface against the trochlea, increased lateral inclination of the patella (tilt), and pathological changes of the patellar tracking (maltracking). Patellar prosthesis The preferred position is either centered over the patella or medialized: - medializing the patellar component is one strategy to decrease the Q angle. Results in uncoverage of lateral facet. Consider removing to lessen risk of lateral facet syndrome. - Another alternative is use of an oval shaped patella with the apex medialized. Lateralization of the patellar prosthesis will increase the Q angle and increase maltracking Intraoperative lateral subluxation of the patella: if patella laterally subluxes intraoperatively during trialing, deflate tourniquet and recheck before performing a lateral release Indications for resurfacing absolute: inflammatory arthritis, patella maltracking, patellofemoral arthritis as the main indication for TKA Internal rotation of the tibial component effectively results in relative external rotation of the tibial tubercle and an increase in the Q angle it is critical to avoid techniques that lead to increase Q angle. Common errors include: - Internal rotation of the femoral prosthesis - Medialization of the femoral component - Internal rotation or medialization of the tibial prosthesis - Placing the patellar prosthesis lateral on the patella

Answer 38

Answer: C Mirels' criteria: 1//2//3 Site: upper limb // lower limb // peritrochanteric Pain: mild // moderate // functional Lesion: Blastic // mixed // lytic Size: <1/3 // 1/3 to 2/3 // > 2/3 Score > 8 suggests prophylactic fixation. do not proceed with fixation until primary neoplasm of bone has been ruled out with biopsy goals of fixation maximize ability for immediate mobilization and weight-bearing protect the entire bone in setting of systemic or metastatic disease optimize implant choice in the context of the patient's overall prognosis. following surgery refer the patient to radiation oncology for post-operative radiotherapy treatment to: - decrease pain - slow progression - treat remaining tumor burden not removed at surgery

Answer 39

Answer: C A superscan is an imaging appearance on a Tc-99m diphosphonate bone scan which occurs as a result of a high ratio of bone to soft tissue tracer accumulation. Intense osteoblastic activity in the bones causes diminished renal and background soft tissue uptake. This appearance can result from a range of causes: diffuse metastatic disease prostatic carcinoma breast cancer transitional cell carcinoma (TCC) multiple myeloma (some difference in opinion) lymphoma patchy uptake nonetheless: look at skull and ribs tends to somewhat spare the distal skeleton metabolic bone diseases renal osteodystrophy hyperparathyroidism 1 (often secondary hyperparathyroidism) osteomalacia will involve distal skeleton smoother uptake myelofibrosis/myelosclerosis mastocytosis widespread Paget disease Radiographic appearance A metastatic superscan tends to have uptake throughout the axial skeleton and proximal appendicular skeleton, often somewhat heterogeneous. In contrast, a metabolic superscan tends to be more uniform and involve both the axial and more peripheral skeleton, including the distal extremities, calvarium, and mandible. Little/no activity is seen within the urinary tract or soft tissues, as most of the tracer is concentrated within the bones.

Answer 40

Answer: C Ewing's Sarcoma is a malignant, distinctive small round cell sarcoma associated with a t(11:22) translocation which most commonly occurs in the diaphysis of long bones in patients <25 with regional pain, swelling and fevers. Diagnosis is made with a biopsy showing sheets of monotonous small round blue cells with prominent nuclei and minimal cytoplasm and immunostaining positive for CD99. Treatment is usually neo-adjuvant chemotherapy and limb salvage surgical resection, followed by adjuvant chemotherapy +/- radiation. t(11:22) translocation found in 85-95% of cases leads to the formation of a fusion protein (EWS-FLI1) XR: large distractive lesion in diaphysis or metaphysics with ill-defined, permeative, moth-eaten appearance. Lytic lesion often with variable amounts of new bone formation. Periosteal reaction may give onion skin or sunburst appearance. Large associated soft tissue mass in >80% cases. Elevated ESR, WCC & LDH Histology: monotonous small round blue cells, high nuclei: cytoplasm ratio. May have pseudo-rosettes (circles of cells with necrosis in centre). Immunistaining: CD99 (+ve in 95%), Standard of care: - Chemo (neoadjuvant (8-12 weeks) + adjuvant (6-12 months)) -> surgery - goal is to obtain local control and prevent late recurrence of chemoresistant cells. Wide margins -> improved 5 year survival. +/- adjuvant radioTx - not necessary if margins are adequate and there is a good response to chemo. Indicated if positive post- surgical resection margins or presence of pulmonary mets.

Answer 41

Answer: E Knee dislocations are high energy traumatic injuries characterized by a high rate of neurovascular injury. Diagnosis is made clinically with careful assessment of limb neurovascular status. Radiographs should be obtained to document reduction. Treatment is generally emergent reduction and stabilization with assessment of limb perfusion followed by delayed ligamentous reconstruction. Associated injuries - vascular injury - nerve injury: usually common peroneal nerve injury (25% incidence), tibial nerve injury is less common - fractures: present in 60% of dislocations - soft tissue injuries: patellar tendon rupture, periarticular avulsion, displaced menisci the knee is a ginglymoid joint and consists of tibiofemoral, patellofemoral and tibiofibular articulations Ligaments: PCL, ACL, LCL, MCL, and PLC are all at risk for injury. Main stabilizers of the knee given the limited stability afforded by the bony articulation. Blood supply: popliteal artery injuries occur often due to tethering at the popliteal fossa: proximal - fibrous tunnel at the adductor hiatus distal - fibrous tunnel at soleus muscle N.B. geniculate arteries may provide collateral flow and palpable pulses masking a limb-threatening vascular injury Biomechanics: the normal range of motion of 0-140 degrees with 8-12 degrees of rotation during flexion/extension Kennedy classification based on the direction of displacement of the tibia: Anterior (30-50%) = commonest. Hyperextension injury, usually involves PCL tear. Highest rate peroneal nerve injury, arterial injury generally intimal tear due to traction. Posterior (30-40%): 2nd commonest, axial load to the flexed knee (dashboard injury), highest rate of vascular injury and highest incidence of complete tear of popliteal artery. Lateral (13%) : varus or valgus force, usually tears of both ACL and PCL Medial (3%): varus or valgus force, usually disrupted PLC & PCL Rotational (4%): usually irreducible, posterolateral is commonest rotational dislocation, button holing (dimple sign) of femoral condyle through capsule. Is a contraindication to closed reduction due to risks of skin necrosis. 50% spontaneously reduced before arrival to ED. Vascular exam priority - serial examinations, ABI. If ABI >0.9 monitor with serial Ex If ABI <0.9 perform arterial duplex USS or CT angiography If pulses are absent or diminished: - confirm that the knee joint is reduced or perform immediate reduction and reassessment - immediate surgical exploration if pulses are still absent following reduction: ischemia time >8 hours has amputation rates as high as 86% imaging contraindicated if it will delay surgical revascularization

Answer 42

Answer: D hip dysplasia acetabular index (AI) : angle formed by Hilgenreiner's line (horizontal line through the right and left triradiate cartilage) and a line from a point on the lateral triradiate cartilage to a point on lateral margin of acetabulum - should be < 25° in patients older than 6 months center-edge angle (CEA) of Wiberg : assesses superolateral coverage of the femoral head on the AP view. angle between a verticle line through the center of the femoral head and the acetabular edge : < 20° is considered abnormal only reliable in patients > 5 years old periacetabular osteotomy (PAO) for symptomatic dysplasia in an adolescent or adult with a concentrically reduced hip and congruous joint space with a preserved range of motion. Triradiate cartilage must be closed. Intraoperative dynamic testing of hip motion is needed to determine the need for femoral osteotomy (minimum of 90° flexion and 15° internal rotation to prevent FAI) Multiple osteomies in pubis, ilium and ischium near the acetabulum, technically most challenging. Advantages: provides hyaline cartilage coverage preserved integrity of the posterior column, which allows patients to weight bear as tolerated postoperatively (posterior column and pelvic ring remain intact). large multidirectional corrections preserves external rotators delays need for arthroplasty outcomes reliably improves radiographic parameters and symptomatology 92% survivorship at 15 years in avoiding THA Chiari = salvage osteotomy for unreduced hip - recommended for patients with inadequate femoral head coverage and incongruous joint (concentric reduction cannot be obtained) - Osteotomy starts above the acetabulum to the sciatic notch and ileum is shifted lateral beyond the edge of the acetabulum. Depends on fibrocartilage metaplasia for successful results. Medializes the acetabulum via iliac osteotomy Shelf: salvage in patients >8 years, add bone to the lateral weight bearing aspect of the acetabulum by placing extra-articular buttress of bone over the subluxed femoral head. Depends of fibrocartilage metaplasia for successful results. Salter - redirectional: younger patient with open triradiate cartilage - single transverse cut above the acetabulum through the ilium to sciatic notch. Acetabulum then hinges through pubis symphysis - improves anterolateral coverage (may length leg up to 1cm) Triple (Steele) is Salter with additional cuts through superior and inferior rami - redirectional for anterolateral coverage) Dega - volume reducing. favoured in neuromuscular dislocation and patients with posterior acetabular deficiency - for severe cases. Osteotomy from acetabular roof to triradiate cartilage (incomplete cuts through peri-capsular of the innominate bone). Acetabulum hinges through the triradiate cartilage. Does not enter the sciatic notch and is therefore stable and does not require internal fixation. Improves anterior, central or posterior coverage. Pemberton = volume reducing, moderate to severe. Triradiate cartilage must be open. stable as osteotomy does not enter sciatic notch.

Answer 43

Answer: A Conservative management for PCL avulsion -> early degenerative changes, meniscal tears and chondral damage. Poor functional outcomes. The open posteromedial approach, which avoids nerves and blood vessels, has the potential to provide a clearer view of the broken ends of the fractured bone, and allows for complete fracture reduction and successful fixation of the bone fracture fragments. Arthroscopic reduction is difficult to achieve. PCL injuries are traumatic knee injuries that may lead to posterior knee instability and often present in combination with other ipsilateral ligamentous knee injuries. PCL is the primary restraint to posterior tibial translation and functions to prevent hyperflexion/sliding. Isolated injuries cause the greatest instability at 90° of flexion. Associated conditions - combined PCL and posterolateral corner (PLC) injuries - multiligamentous knee injuries - knee dislocation PCL origin: posterior tibial sulcus below the articular surface insertion: anterolateral medial femoral condyle broad, crescent-shaped footprint 38 mm in length x 13 mm in diameter - PCL is 30% larger than the ACL PCL has two bundles: - Anterolateral bundle: tight in flexion. Strongest and most important for posterior stability at 90° of flexion mnemonic "PAL" - PCL has an AnteroLateral bundle (N.B. ACL is AM & PL bundle) - Posteromedial bundle: tight in extension - reciprocal function to the anterolateral bundle PCL lies between the meniscofemoral ligaments: ligament of Humphrey (anterior) and ligament of Wrisberg (posterior) - originate from the posterior horn of the lateral meniscus and insert into PCL substance Blood supply by branches of the middle geniculate artery and fat pad PCL injury Classification:(based on posterior subluxation of tibia relative to femoral condyles with knee in 90° of flexion) Grade I: partial tear, 1-5mm posterior tibial translation, tibia remains anterior to the femoral condyles. Grade II: complete isolate tear, 6-10mm posterior tibial translation. Complete injury in which the anterior tibia is flush with the femoral condyles. Grade III: combined PCL & capsuloligamentous injury, Ex >10mm posterior tibial translation. Tibia is posterior to the femoral condyles and often indicates an associated ACL and or PLC injury. PCL repair of bony avulsion fractures or reconstruction

Answer 44

Answer: B Portals: - Anteromedial: primary viewing portal (typically established first) and gives access to anteromedial joint.  Medial to tibialis anterior  Lateral to medial malleolus  Make portal between tibialis anterior and saphenous vein • Anterolateral: gives access to anterolateral joint  Just lateral to peroneus tertius and superficial peroneal nerve  Medial to lateral malleolus  can trace out superficial peroneal nerve prior to incision

Answer 45

Answer: C Femoral Anteversion is a common congenital condition caused by intrauterine positioning which lead to increased anteversion of the femoral neck relative to the femur with compensatory internal rotation of the femur. Diagnosis is made clinically with the presence of intoeing combined with an increase in internal rotation of the hip of greater than 70° (normal is 20-60°) with an accompanying decrease in external rotation of the hip of less than 20° (normal is 30-60°). Femoral anteversion is characterized by increased anteversion of the femoral neck relative to the femur compensatory internal rotation of the femur lower extremity intoeing In younger children : observation and parental reassurance - most cases spontaneously resolve by age 10. Operative Mx with femoral de-rotation osteotomy - for >§0years with <10 degrees eexternal rotation, typically performed at the intertroch level

Answer 46

Answer: A Posterolateral plate placement: - Safe zone (non-articular area) consists of 90-110º arc defined by the projections of the radial styloid and Lister's tubercle This zone is straight lateral with arm in neutral rotation to avoid impingement of ulna with forearm rotation Bicipital tuberosity is the distal limit of plate placement - anything distal to that will endanger PIN Countersink implants on articular surface Plate removal relatively common in order to restore forearm rotation Complications - PIN injury - destabilization of -lateral ligament complex - articular surface penetration with screws - mechanical block to motion by hardware

Answer 47

Answer: D Pigmented Villonodular Synovitis is a locally aggressive neoplastic synovial disease (not a true neoplasm) characterized by joint effusions, expansion of the synovium, and bony erosions. The condition usually presents in patients between 30 and 40 years old with recurrent atraumatic knee hemarthrosis. Diagnosis is multifaceted with clinical assessment for joint effusion (most commonly the knee), MRI studies showing synovial expansion, arthrocentesis revealing a brown fluid, and biopsy revealing hemosiderin-stained multinucleated giant cells. Treatment generally consists of partial or total surgical synovectomy depending on presence of localized or diffuse PVNS. PVNS is associated with a high rate of recurrence and accelerated degenerative changes of the knee ultimately requiring arthroplasty TKA in patients with PVNS is associated with complication rates Pathobiology: caused by an overexpression of CSF1 gene. Overexpression leads to clusters of aberrant cells creating focal areas of soft tissue hyperplasia in the synovial cells lining joints. A locally aggressive neoplastic synovial disease (not a true neoplasm). Mutation Chr 1p13 in majority cases. Recurrence is the most frequent complication for both intra-articular and extra-articular disease: 30%-50% recurrence rate despite complete synovectomy - same rates for complete open vs open+arthroscopic. Synovial Chondromatosis is a proliferative disease of the synovium associated with cartilage metaplasia that results in multiple intra-articular loose bodies. The condition usually presents in patients between 30 and 50 years of age with localized joint pain, stiffness, and swelling. Diagnosis is made on radiographs in late disease but MRI studies may be required in early disease to show cartilage nodules throughout the joint space.

Answer 48

Answer: A The most common bacterial etiologic agent following varicella is group A beta-hemolytic streptococcus. The other organisms are much less common. Staphylococcus aureus is the most common bone infection organism. Staphylococcus epidermidis is increasingly a bone infection organism. Group B streptococcus occurs more commonly in newborns. Kingella kingae is a common joint pathogen but is not as common following varicella. a subperiosteal abscess develops when the purulence breaks through the metaphyseal cortex septic arthritis develops when the purulence breaks through an intra-articular metaphyseal cortex (hip, shoulder, elbow, and ankle) (NOT KNEE) Staph aureus is the most common organism in all children strains of community-acquired (CA) MRSA have genes encoding for Panton-Valentine leukocidin (PVL) cytotoxin PVL-positive strains are more associated with complex infections, multifocal infections, prolonged fever, abscess, DVT, and sepsis MRSA is associated with increased risk of DVT and septic emboli Group B Strep: is most common organism in neonates Kingella kingae: becoming more common in younger age groups Pseudomonas: is associated with direct puncture wounds to the foot H. influenza: has become much less common with the advent of the Haemophilus influenza vaccine Mycobacteria tuberculosis: children are more likely to have extrapulmonary involvement biopsy with stains and culture for acid-fast bacilli is diagnostic Salmonella: more common in sickle cell patients

Answer 49

Answer: B Kochers criteria Original Kocher Criteria four criteria WBC > 12,000 cells/µl of serum inability to bear weight fever > 101.3° F (38.5° C) ESR > 40 mm/h algorithm probability of septic arthritis may be as high as 99.6% when all four criteria above are present if none of the above predictors are present, probability of having septic arthritis is <0.2% 3% incidence of septic arthritis if 1/4 criteria present, 40% incidence if 2/4 criteria present, 93% incidence if 3/4 criteria present Modified Kocher Criteria additional criteria CRP

Answer 50

Answer: B ACL -> anterior and lateral rotatory instability of the knee. Females tend to sustain ACL injuries at a younger age than males, and more frequently on the supporting leg (vs males on kicking leg). Preponderance for females due to landing biomechanics and neuromuscular activation patterns (quadriceps dominant) play the biggest role. - Valgus moment at knee and adduction moment at hip upon landing. Pathoanatomy: - Non-contact pivoting injury - tibia translates anteriorly while knee is in slight flexion and valgus. - Blow to the lateral aspect of the knee Associated injuries: - Lateral meniscal tears in 54% of acute ACL tears, medial in chronic causes. - PCL, LCL/PLC injuries - Chronic ACL deficient knees associated with chondral injuries and complex unrepairable meniscal tears and bucket handle medial meniscus tears. 2 bundles: combined 32mm length x 7-12 mm width. Bundles named for tibial attachment. - Anteromedial bundle: more isometric, tightest in flexion, primarily responsible for restraining anterior tibial translation (anterior drawer test) - Posterolateral bundle: greater length changes, tightest in extension, primarily responsible for rotational stability (pivot shift test) Femoral attachment - Lateral intercondylar ridge demarcates the anterior edge of the ACL - Bifurcate ridge separates the anteromedial and posterolateral bundle attachment Tibial attachment: anterior tibia, between intercondylar eminences. 90% Type I collagen, 10% type II collagen. Blood supply = middle geniculate artery Innervation: Posterior articular nerve (branch of tibial nerve) Provides 85% stability to prevent anterior translation of the tibia relative to the femur and acts as a secondary restraint to tibial rotation and varus/valgus rotation. 2200N strength (anterior). ACL rupture: pop, deep knee pain, immediate swelling (70%), haemarthrosis. Quadriceps avoidance gait (does not actively extend knee). Coronal or sagittal plane deformity - varus deformity increases risk for SCL re-rupture.. Lacman's test: most sensitive exam test - Grading A= firm end point, B = no end point. 1: 3-5mm translation 2 A/B: 5-10mm translation 3 A/B: > 10mm translation PCL tear may give a false positive Lacman due to posterior subluxation. Pivot Shift: knee brought from extension (anteriorly subluxated) to flexion (reduced) with valgus and internal rotation of the tibia - reduces at 20-30 deg flexion due it IT band tension - must be completely relaxed patient (/anaesthetised) and mimics actual giving way event. Segond fracture: avulsion fracture of the proximal lateral tibia - pathognomonic for ACL tear Deep Sulcus (terminalis) sign: depression on the lateral femoral condyle at the terminal sulcus, a junction between the weight bearing tibial articular surface and the patellar articular surface of the femoral condyle. Treatment: physio, lifestyle modifications in low demand patients and recreational athletes not participating in cutting/pivoting activities, BUT linked to increased meniscal & cartilage damage - loss of meniscal integrity, more frequent buckling episodes. ACL reconstruction: must have full ROM restored following injury (unless meniscal tear causing mechanical block) - lack of pre-op ROM risk factor for post-op arthrofibrosis. Indicated in younger more active patients, children, older active patients, partial/single bundle tears with clinical and functional instability. Goal: anatomically reconstruct ligament to restore anterior and rotational stability. Femoral tunnel: - Sagittal plane: 1-2mm rim of bone between the tunnel and posterior cortex of the femur. - Coronal plane: lateral wall at 2 o'clock (L) or 10 o'clock (R) - creates a more horizontal graft (and reduces rotational laxity). Tibial Tunnel: - Sagittal plane: centre of tunnel entrance into joint should be 10-11mm in front of the anterior border of PCL insertion, 6mm anterior to the median emminence, 9mm posterior to the inter meniscal ligament. - Coronal plane: tunnel trajectory of <75deg from horizontal (obtain by moving tibial starting point halfway between tibial tubercle and posterior medial edge of tibia.) Graft failure rate approx 5% - tunnel malpoisiton is commonest cause (70%). Graft pre-conditioning can reduce stress relaxation up to 50%. Quadrupled hamstring autograft: small incision, less peri-op and anterior knee pain. Max load to failure 4000N. Decreased peak flexion strength at 3 years compared to BPTB - concern about hamstring weakness in female athletes leading to increased risk of re-rupture. Risk saphenous nerve branches during harvest. Concurrent pathology: - MCL: if low grade MCL injury amenable to non-operative treatment, allow MCL to heal prior to ACL reconstruction. If high grade MCL injury necessitating repair/reconstruction, may be done concurrently with ACL. Failure to address valgus instability can jeopardise ACL graft with higher re-rupture rates. - Meniscal tears: perform repair or meniscectomy at time of ACL recon - increased meniscal healing rate when repaired at the same time as ACL. - Chondral injuries: Presence of chondral defects consistently lowers long term PROMs following ACL recon. - PCL and PLC injuries: concurrent reconstruction or staged procedure - failure to address will lead to varus instability and ACL graft overload.

Answer 51

Answer: B Pemberton = volume reducing, moderate to severe. Triradiate cartilage must be open. stable as osteotomy does not enter sciatic notch. Osteotomy starts approximately 10-15mm above the AIIS and proceeds posteriorly to end at the level of the ilioischial limb of the triradiate cartilage (halfway between the sciatic notch and the posterior acetabular rim). Acetabulum hinges at the triradiate cartilage posteriorly and the symphysis pubis anteriorly. Does not enter the sciatic notch and is therefore stable and does not need internal fixation. Improves anterolateral coverage. periacetabular osteotomy Ganz (PAO) for symptomatic dysplasia in an adolescent or adult with a concentrically reduced hip and congruous joint space with a preserved range of motion. Triradiate cartilage must be closed. Intraoperative dynamic testing of hip motion is needed to determine the need for femoral osteotomy (minimum of 90° flexion and 15° internal rotation to prevent FAI) Multiple osteomies in pubis, ilium and ischium near the acetabulum, technically most challenging. Advantages: provides hyaline cartilage coverage preserved integrity of the posterior column, which allows patients to weight bear as tolerated postoperatively (posterior column and pelvic ring remain intact). large multidirectional corrections preserves external rotators delays need for arthroplasty outcomes reliably improves radiographic parameters and symptomatology 92% survivorship at 15 years in avoiding THA Chiari = salvage osteotomy for unreduced hip - recommended for patients with inadequate femoral head coverage and incongruous joint (concentric reduction cannot be obtained) - Osteotomy starts above the acetabulum to the sciatic notch and ileum is shifted lateral beyond the edge of the acetabulum. Depends on fibrocartilage metaplasia for successful results. Medializes the acetabulum via iliac osteotomy Shelf: salvage in patients >8 years, add bone to the lateral weight bearing aspect of the acetabulum by placing extra-articular buttress of bone over the subluxed femoral head. Depends of fibrocartilage metaplasia for successful results. Salter - redirectional: younger patient with open triradiate cartilage - single transverse cut above the acetabulum through the ilium to sciatic notch. Acetabulum then hinges through pubis symphysis - improves anterolateral coverage (may length leg up to 1cm) Triple (Steele) is Salter with additional cuts through superior and inferior rami - redirectional for anterolateral coverage) Dega - volume reducing. favoured in neuromuscular dislocation and patients with posterior acetabular deficiency - for severe cases. Osteotomy from acetabular roof to triradiate cartilage (incomplete cuts through peri-capsular of the innominate bone). Acetabulum hinges through the triradiate cartilage. Does not enter the sciatic notch and is therefore stable and does not require internal fixation. Improves anterior, central or posterior coverage. hip dysplasia acetabular index (AI) : angle formed by Hilgenreiner's line (horizontal line through the right and left triradiate cartilage) and a line from a point on the lateral triradiate cartilage to a point on lateral margin of acetabulum - should be < 25° in patients older than 6 months center-edge angle (CEA) of Wiberg : assesses superolateral coverage of the femoral head on the AP view. angle between a verticle line through the center of the femoral head and the acetabular edge : < 20° is considered abnormal only reliable in patients > 5 years old

Answer 52

Answer: A CAVE Clubfoot, also known as congenital talipes equinovarus, is a common idiopathic deformity of the foot that presents in neonates. Diagnosis is made clinically with a resting equinovarus deformity of the foot. Half of cases are bilateral and in 80%, clubfoot is an isolated deformity. Genetic component is strongly suggested - recent link to PITX1. Associated with arthrogryposis. Pathophysiology Muscle contractures contribute to the characteristic deformity that includes (CAVE): - Cavus (tight intrinsics, FHL, FDL) - Adductus of forefoot (tight tibialis posterior) - Varus (tight tendoachilles, tibialis posterior, tibialis anterior) - Equinus (tight tendoachilles) Bony deformity consists of medial spin of the midfoot and forefoot relative to the hindfoot - talar neck is medially and plantarly deviated - calcaneus is in varus and rotated medially around talus - navicular and cuboid are displaced medially

UK*TE Dec 21 Flashcards

(126 cards)