MSK + Rheum Flashcards
(154 cards)
1
Q
Radiographic findings of osteosarcoma
A
Destruction of normal trabecular bone pattern
Mixed radiodense (sclerotic) and radiolucent (lytic) areas
Periosteal new bone formation with lifting of the periosteum → forming a Codman triangle
“Sunburst” pattern of ossification in adjacent soft tissue
2
Q
What is Paget disease of the bone?
A
3
Q
What are common manifestations of Paget disease of the bone?
A
4
Q
What are the three most common complications of Paget disease of the bone?
A
5
Q
What are the signs and symptoms of an acute gout attack?
A
An acute gout attack typically presents with sudden, intense joint pain, most often affecting the big toe (a condition known as podagra), though other joints such as the ankles, knees, elbows, wrists, and fingers can also be involved. The affected joint becomes swollen, red, warm, and extremely tender, often to the point where even the weight of a bedsheet is intolerable.
These attacks frequently occur at night and reach peak intensity within 12 to 24 hours. Following the acute phase, discomfort may persist for several days to weeks, and subsequent attacks may last longer and affect multiple joints.
Neutrophilic effusion
6
Q
What does negative versus positive birefringence indicate in crystal-induced arthritis?
A
Birefringence refers to the optical property of crystals that causes them to refract light in two different directions under polarized light microscopy.
In the context of crystal-induced arthritis, monosodium urate crystals, which are responsible for gout, exhibit negative birefringence. These needle-shaped crystals appear yellow when aligned parallel to the axis of the red compensator and blue when perpendicular.
Conversely, calcium pyrophosphate dihydrate crystals, associated with pseudogout, show positive birefringence. These rhomboid-shaped crystals appear blue when parallel and yellow when perpendicular to the red compensator axis. Identifying the type of birefringence is crucial for distinguishing between gout and pseudogout
7
Q
Commonly injured neurovascular structure in posterior knee dislocation?
A
Popliteal artery:
8
Q
Draw out the brachial plexus
A
9
Q
What are the 5 terminal branches of the brachial plexus?
A
Musculocutaneous
Axillary
Radial
Medial
Ulnar
10
Q
What injuries can damage the axillary nerve?
A
Fracture of surgical neck of humerus or anterior dislocation of the humerus.
11
Q
What are the spinal levels of the axillary nerve?
A
C5–C6
12
Q
What are the consequences of an axillary nerve injury?
A
Flattened deltoid, loss of arm abduction (>15°), and loss of sensation over deltoid and lateral arm.
13
Q
What is a common cause of musculocutaneous nerve injury?
A
Upper trunk compression.
14
Q
What spinal levels contribute to the musculocutaneous nerve?
A
C5–C7
15
Q
What happens with a musculocutaneous nerve injury?
A
Loss of forearm flexion and supination, decreased biceps reflex (C5–C6), and loss of sensation over lateral forearm.
16
Q
What can cause radial nerve injury?
A
Compression in the axilla (e.g., crutches or “Saturday night palsy”), midshaft humerus fracture, or repetitive pronation/supination (“finger drop”).
17
Q
What are the spinal levels of the radial nerve?
A
C5-T1
18
Q
What results from radial nerve injury?
A
Wrist drop, loss of elbow/wrist/finger extension, decreased grip strength, and sensory loss on posterior arm, forearm, and dorsal hand.
19
Q
What causes proximal vs distal median nerve injuries?
A
Proximal: Supracondylar humerus fracture; Distal: Carpal tunnel syndrome or wrist laceration.
20
Q
What spinal levels are associated with the median nerve?
A
C5–T1
21
Q
What are the effects of median nerve injury?
A
“Hand of benediction” (proximal)
“Median claw” (distal)
loss of LOAF muscles, thenar atrophy, and sensory loss in lateral 3½ fingers (palmar and dorsal tips).
22
Q
What are the LOAF muscles?
A
Lateral two lumbricals, Opponens pollicis, Abductor pollicis brevis, and Flexor pollicis brevis
23
Q
What are the mechanisms of ulnar nerve injury?
A
Proximal: Medial epicondyle fracture; Distal: Hook of hamate fracture; also compression from handlebar use.
24
Q
What spinal levels contribute to the ulnar nerve?
A
C8–T1
25
What are signs of ulnar nerve injury?
“Ulnar claw,” radial deviation on wrist flexion (proximal), sensory loss on medial 1½ fingers, and impaired finger abduction/adduction.
26
What causes injury to the recurrent branch of the median nerve?
Superficial laceration of the palm.
27
What results from injury to the recurrent branch of the median nerve?
“Ape hand,” loss of thenar muscle function (opposition, abduction, flexion of thumb), but no sensory loss.
28
What is the mnemonic to remember which nerves are affected by humerus fractures from proximal to distal?
Use the mnemonic ARM:
Axillary nerve → injured with proximal (surgical neck) fractures
Radial nerve → injured with midshaft fractures
Median nerve → injured with distal (supracondylar) fractures
"Humerus fractures, proximally to distally, follow the ARM (Axillary → Radial → Median) nerves.
29
Mnemonic for segments of the brachial plexus
30
What is the injury and cause of Erb palsy?
Traction or tear of the upper trunk (C5–C6).
Caused by lateral neck traction during delivery (infants) or trauma such as falling on head and shoulder (adults).
31
What muscles and functions are affected in Erb palsy?
Muscle deficit: Deltoid, supraspinatus, infraspinatus, biceps brachii
Functional deficit: Loss of abduction (arm hangs by side), lateral rotation (arm medially rotated), and supination/flexion (arm extended and pronated)
32
What is the injury and cause of Klumpke palsy?
Traction or tear of the lower trunk (C8–T1).
Caused by upward force on the arm during delivery (infants) or grabbing something to break a fall (adults).
33
What muscles and functions are affected in Klumpke palsy?
Muscle deficit: Intrinsic hand muscles – lumbricals, interossei, thenar, hypothenar
Functional deficit: Claw hand – loss of lumbrical function (MCP flexion + DIP/PIP extension)
34
What is the injury and cause of thoracic outlet syndrome?
Compression of the lower trunk and subclavian vessels, often in the scalene triangle.
Causes include cervical rib, anomalous first rib, or Pancoast tumor.
35
What muscles and functions are affected in thoracic outlet syndrome?
Muscle deficit: Same as Klumpke palsy (intrinsic hand muscles)
Functional deficit: Muscle atrophy, pain, ischemia, edema due to vascular compression
36
What is the injury and cause of winged scapula?
Lesion of the long thoracic nerve (C5–C7)
Caused by axillary node dissection (e.g., post-mastectomy) or stab wounds
37
What muscles and functions are affected in winged scapula?
Muscle deficit: Serratus anterior
Functional deficit: Inability to anchor scapula to thoracic cage, leading to winging and inability to abduct arm above horizontal
38
What are the 8 carpal bones and how can you remember their order?
Proximal row: Scaphoid, Lunate, Triquetrum, Pisiform
Distal row: Trapezium, Trapezoid, Capitate, Hamate
“So Long To Pinky, Here Comes The Thumb”
39
What is the most commonly fractured carpal bone and how does it happen?
The scaphoid is the most commonly fractured carpal bone, usually due to a fall on an outstretched hand (FOOSH).
📍 It is palpated in the anatomic snuff box.
🩸 Risk: Avascular necrosis and nonunion due to retrograde blood supply from a branch of the radial artery.
40
What complication can result from dislocation of the lunate bone?
Dislocation of the lunate can compress the median nerve, leading to carpal tunnel syndrome.
41
What is Guyon canal syndrome and what causes it?
Guyon canal syndrome is ulnar nerve compression caused by a fracture of the hook of the hamate.
Symptoms may include sensory and motor loss in the ulnar distribution of the hand.
42
What are the muscles of the thenar eminence, and what nerve innervates them?
Muscles:
Opponens pollicis
Abductor pollicis brevis
Flexor pollicis brevis (superficial head by median nerve, deep head by ulnar nerve)
Nerve: Mainly median nerve
Function mnemonic: OAF = Oppose, Abduct, Flex
43
What are the muscles of the hypothenar eminence, and what nerve innervates them?
Muscles:
Opponens digiti minimi
Abductor digiti minimi
Flexor digiti minimi brevis
Nerve: Ulnar nerve
Function mnemonic: Same as thenar – OAF = Oppose, Abduct, Flex
44
What is the function and innervation of the dorsal vs palmar interossei
Dorsal interossei (DAB): Dorsals ABduct fingers
Palmar interossei (PAD): Palmars ADduct fingers
Nerve: Both are innervated by the ulnar nerve
45
What nerve lesions are associated with atrophy of the thenar vs hypothenar eminence?
Thenar eminence atrophy → seen in median nerve lesions
Hypothenar eminence atrophy → seen in ulnar nerve lesions
46
ID the ligaments of the knee
47
What is the difference between the Lachman test and the Anterior Drawer test for ACL injury?
48
What does a positive Valgus stress test indicate and how is it performed?
Apply a lateral (valgus) force to the knee at ~30° flexion or full extension
Positive test = medial tibial space widening
Indicates injury to the MCL (Medial Collateral Ligament)
49
What does a positive Varus stress test indicate and how is it performed?
Apply a medial (varus) force to the knee at ~30° flexion or full extension
Positive test = lateral tibial space widening
Indicates injury to the LCL (Lateral Collateral Ligament)
50
What does a positive McMurray test indicate, and how do you differentiate between a lateral and medial meniscal tear?
51
What is the cremasteric reflex?
The cremasteric reflex is a superficial reflex observed in males, in which stroking the inner thigh causes contraction of the cremaster muscle, resulting in elevation of the ipsilateral testis.
52
What nerve fibers are involved in the cremasteric reflex?
Afferent limb: Ilioinguinal nerve (L1)
Efferent limb: Genital branch of the genitofemoral nerve (L1–L2)
53
What clinical conditions may cause an absent cremasteric reflex?
Testicular torsion (often absent on the affected side)
Upper and lower motor neuron lesions affecting L1–L2
Spinal cord injury at L1–L2 level
54
What region of the body does the **Iliohypogastric (T12-L1)** nerve innervate?
Sensory—suprapubic region;
Motor—transversus abdominis and internal oblique
55
What is a common cause of **Iliohypogastric (T12-L1)** nerve injury?
Abdominal surgery (commonly inguinal hernia repair)
56
What are typical symptoms of **Iliohypogastric (T12-L1)** nerve injury?
Neuropathic pain in surgical site radiating to inguinal and suprapubic region
57
What region of the body does the **Genitofemoral (L1-L2)** nerve innervate?
Sensory—scrotum/labia majora, medial thigh;
Motor—cremaster (efferent limb)
58
What is a common cause of **Genitofemoral (L1-L2)** nerve injury?
Laparoscopic surgery
59
What are typical symptoms of **Genitofemoral (L1-L2)** nerve injury?
↓ sensation upper medial thigh and anterior thigh
absent cremasteric reflex
60
What region of the body does the **Lateral femoral cutaneous (L2-L3)** nerve innervate?
Sensory—anterior and lateral thigh
61
What is a common cause of **Lateral femoral cutaneous (L2-L3)** nerve injury?
Tight clothing, obesity, pregnancy, pelvic procedures
62
What are typical symptoms of **Lateral femoral cutaneous (L2-L3)** nerve injury?
Meralgia paresthetica: tingling, numbness, burning in anterolateral thigh due to compression of hte lateral femoral cutaneous
63
What region of the body does the **Obturator (L2-L4)** nerve innervate?
Sensory—medial thigh;
Motor—hip adductors (obturator externus, etc.)
64
What is a common cause of **Obturator (L2-L4)** nerve injury?
Pelvic operation
65
What are typical symptoms of **Obturator (L2-L4)** nerve injury?
↓ medial thigh sensation and adduction
66
What region of the body does the **Femoral (L2-L4)** nerve innervate?
Sensory—anterior thigh, medial leg; Motor—quadriceps, iliacus, pectineus, sartorius
67
What is a common cause of **Femoral (L2-L4)** nerve injury?
Pelvic fracture, hematoma, psoas abscess
68
What are typical symptoms of **Femoral (L2-L4)** nerve injury?
↓ leg extension, ↓ patellar reflex
69
What region of the body does the **Sciatic (L4-S3)** nerve innervate?
Sensory—posterior thigh and leg (except medial leg band);
Motor—posterior thigh and leg muscles
70
What is a common cause of **Sciatic (L4-S3)** nerve injury?
Herniated disc, posterior hip dislocation, piriformis syndrome
71
How dos the sciatic nerve divide?
Splits into tibial and common peroneal nerves at the popliteal fossa.
72
What region of the body does the **Common peroneal (fibular) (L4-S2)** nerve innervate?
Sensory—dorsum of foot except webspace between haallux and 2nd digit;
Motor—peroneus longus/brevis, tibialis anterior
73
What is a common cause of **Common peroneal (L4-S2)** nerve injury?
Trauma or compression of fibular neck
74
What are typical symptoms of **Common peroneal (L4-S2)** nerve injury?
Foot drop, steppage gait, ↓ dorsum sensation
75
What region of the body does the **Tibial (L4-S3)** nerve innervate?
Sensory—sole of foot;
Motor—posterior leg muscles, foot flexors
76
What is a common cause of **Tibial (L4-S3)** nerve injury?
Knee trauma, Baker cyst (in the popliteal fossa - proximal lesion), tarsal tunnel syndrome (distal lesion)
77
What are typical symptoms of **Tibial (L4-S3)** nerve injury?
TIP: Tibial Inverts and Plantarflexes; can't stand on TIPtoes
Inability to curl toes and loss of sensation on the sole
78
What region of the body does the **Superior gluteal (L4-S1)** nerve innervate?
Motor—gluteus medius/minimus, tensor fascia latae
79
What is a common cause of **Superior gluteal (L4-S1)** nerve injury?
Iatrogenic injection to superomedial gluteal region during intramuscular injection
80
What are typical symptoms of **Superior gluteal (L4-S1)** nerve injury?
Trendelenburg sign/gait - pelvis tilts because the weight-bearing leg cannot maintain the alignment of the pelvis through hip abduction.
81
What region of the body does the **Inferior gluteal (L5-S2)** nerve innervate?
Motor—gluteus maximus
82
What is a common cause of **Inferior gluteal (L5-S2)** nerve injury?
Posterior hip dislocation
83
What are typical symptoms of **Inferior gluteal (L5-S2)** nerve injury?
Difficulty climbing stairs/rising from seated. Normally responsible for hip extension.
84
What region of the body does the **Pudendal (S2-S4)** nerve innervate?
Sensory—perineum;
Motor—external urethral and anal sphincters
85
What is a common cause of **Pudendal (S2-S4)** nerve injury?
Stretch injury (childbirth, cycling, horseback riding)
86
What are typical symptoms of **Pudendal (S2-S4)** nerve injury?
↓ perineal/genital sensation, fecal/urinary incontinence
87
Which side is affected in Trendelenburg gait?
Lesion is located on the side of the raised hip because of the bearing leg cannot maintain the alignment of the pelvis due to impaired abduction.
88
What is the most common ankle sprain overall?
Sprain of the anterior talofibular ligament, classified as a low ankle sprain.
89
What typically causes an anterior talofibular ligament sprain?
Overinversion of the foot.
90
What is the most common high ankle sprain?
Sprain of the anterior inferior tibiofibular ligament.
91
What is the pathophysiology of intervertebral disc herniation?
The nucleus pulposus herniates posterolaterally through the annulus fibrosus into the spinal canal due to a thin posterior longitudinal ligament and thicker anterior ligament.
92
Which nerve root is affected in a disc herniation?
The nerve root affected is usually the one **below** the level of herniation (e.g., L4-L5 herniation affects L5 nerve root).
93
What tests are used to evaluate lumbosacral radiculopathy?
⊕ Straight leg raise test for L5/S1 radiculopathy; ⊕ Reverse straight leg raise (femoral stretch) for L3/L4.
94
What are the symptoms of L3-L4 disc herniation (affecting L4 nerve)?
Dermatome: anterior lateral thigh and medial leg; Weakness in knee extension, ↓ patellar reflex.
95
What are the symptoms of L4-L5 disc herniation (affecting L5 nerve)?
Dermatome: lateral leg and dorsum of foot; Weakness in dorsiflexion, difficulty heel walking.
96
What are the symptoms of L5-S1 disc herniation (affecting S1 nerve)?
Dermatome: posterior leg and lateral foot; Weakness in plantar flexion, difficulty toe walking, ↓ Achilles reflex.
97
When is the contralateral straight leg raise test positive, and what does it indicate?
The contralateral straight leg raise is positive when lifting the unaffected leg reproduces radicular pain in the affected leg. This suggests a large disc herniation compressing the nerve root, often indicating lumbosacral radiculopathy (commonly L5 or S1 nerve root involvement).
98
Muscule contraction - first step: What happens when ACh binds postsynaptically at the motor end plate?
Postsynaptic ACh binding causes muscle cell depolarization at the motor end plate.
99
Muscle contraction - How does the depolarization spread through the muscle fiber?
The depolarization spreads across the entire muscle cell and deep into it via T-tubules.
100
Muscle contraction - How is Ca²⁺ released from the sarcoplasmic reticulum?
Membrane depolarization alters dihydropyridine receptor (DHPR), triggering ryanodine receptor (RR) to release Ca²⁺ into cytoplasm.
101
Muscle contraction - What role does troponin and tropomyosin play in contraction?
Ca²⁺ binds troponin C (TnC), shifting tropomyosin to expose myosin-binding sites on actin.
102
Muscle contraction - What initiates the power stroke?
Myosin head binds actin (forming crossbridge), and Pi is released to initiate the power stroke.
103
Step 7: What happens during the power stroke? Which bands of the sarcomere are shortened?
Myosin pulls the thin filament, shortening H and I bands and Z lines; A band stays the same; ADP is released.
104
What causes myosin head detachment from actin?
Binding of a new ATP molecule causes myosin to detach from actin; Ca²⁺ is re-sequestered.
105
How does the myosin head reset?
ATP hydrolysis re-cocks the myosin head; it can bind a new actin site if Ca²⁺ is still present.
106
How is muscle relaxation achieved in striated muscle cells?
Calcium is actively pumped back into the sarcoplasmic reticulum via SERCA (Ca²⁺-ATPase), leading to muscle relaxation.
107
What are the differences in contraction velocity and fiber color between Type I and Type II muscle fibers?
Type I: Slow contraction, red fibers
Type II: Fast contraction, white fibers
108
What are the differences in metabolism and endurance between Type I and Type II muscle fibers?
Type I: Oxidative phosphorylation → sustained contraction
Type II: Anaerobic glycolysis → quick, powerful bursts
109
How do mitochondria, myoglobin content, and training types differ between Type I and Type II fibers?
Type I: High mitochondria and myoglobin; used in endurance training
Type II: Low mitochondria and myoglobin; used in sprinting/weight training
110
What happens during skeletal muscle atrophy?
↓ Myofibrils via the ubiquitin-proteasome system
↓ Myonuclei due to selective apoptosis
111
What happens during skeletal muscle hypertrophy?
↑ Myofibrils through addition of sarcomeres in parallel
↑ Myonuclei from fusion of satellite cells, which repair damaged myofibrils (not seen in cardiac muscle)
112
What receptor is responsible for the deep tendon reflexes?
The muscle stretch receptor (muscle spindle) is responsible for the deep tendon reflex, activated by increased muscle stretch.
113
Where are muscle stretch receptors located and what sensory axons do they use?
Located in the muscle body, they use type Ia and II sensory axons.
114
What activates the Golgi tendon organ and what is its function?
Activated by ↑ muscle tension; it activates inhibitory interneurons, which inhibit the agonist muscle, reducing muscle and tendon tension.
115
Where is the Golgi tendon organ located and what type of axons does it use?
Located in tendons, it uses type Ib sensory axons to monitor and respond to muscle tension.
116
What is the RANKL–RANK pathway and how does it affect bone?
RANKL, produced by osteoblasts, binds RANK on osteoclast precursors.
This promotes osteoclast formation, activation, and survival, leading to bone resorption.
117
What is the function of osteoprotegerin (OPG) in bone remodeling?
OPG is a decoy receptor secreted by osteoblasts that binds to RANKL, preventing it from interacting with RANK on osteoclast precursors. This inhibits osteoclast formation and activity, reducing bone resorption and helping maintain bone density.
118
What cell type do osteoclasts differentiate from?
Osteoclasts originate from monocyte/macrophage lineage of hematopoietic stem cells (same lineage as immune cells).
119
What cell type do osteoblasts differentiate from?
Osteoblasts differentiate from mesenchymal stem cells, which can also give rise to chondrocytes, adipocytes, and myocytes.
120
What effect does low, intermittent PTH have on bone?
It exerts anabolic (bone-building) effects by stimulating osteoblasts and indirectly influencing osteoclasts.
121
What effect does chronically elevated PTH (e.g., in primary hyperparathyroidism) have on bone?
It causes catabolic effects, increasing bone resorption and leading to osteitis fibrosa cystica.
122
How does estrogen help maintain bone density?
Estrogen inhibits apoptosis in osteoblasts (bone-forming) and promotes apoptosis in osteoclasts (bone-resorbing), preserving bone mass.
123
What are the effects of estrogen deficiency (e.g., menopause) on bone?
It leads to increased bone remodeling and resorption, increasing the risk of osteoporosis.
124
What is the role of calcitonin in bone metabolism?
Calcitonin is released by parafollicular C cells of the thyroid and inhibits osteoclast activity, thereby reducing bone resorption.
125
How is calcitonin used clinically?
Used in conditions like Paget disease of bone, osteoporosis, and hypercalcemia to decrease serum calcium by inhibiting bone breakdown.
126
How does vitamin D support bone health?
Vitamin D increases intestinal absorption of calcium and phosphate, promoting bone mineralization.
127
What happens in vitamin D deficiency?
Leads to hypocalcemia, resulting in rickets in children and osteomalacia in adults due to impaired bone mineralization.
128
What is the difference between tennis elbow and golfer’s elbow?
Tennis elbow (lateral epicondylitis): Due to repetitive wrist extension → pain near the lateral epicondyle
Golfer’s elbow (medial epicondylitis): Due to repetitive wrist flexion → pain near the medial epicondyle
129
What causes a psoas abscess, and who is at risk?
Caused by hematogenous spread or extension from adjacent structures (e.g., osteomyelitis, tuberculosis/Pott disease, pyelonephritis).
Associated with Crohn disease, diabetes, and immunocompromised states.
Staphylococcus aureus is the most common organism.
130
What are the symptoms and diagnostic findings in psoas abscess?
Symptoms: Flank pain, fever, inguinal mass, positive psoas sign (pain on hip extension).
Labs: Leukocytosis
Imaging (CT/MRI): Focal hypodense lesion in the iliopsoas muscle plane.
131
How is a psoas abscess treated?
Treatment involves abscess drainage and antibiotic therapy.
132
What structures are typically damaged in the unhappy triad knee injury?
Anterior cruciate ligament (ACL)
Medial collateral ligament (MCL)
Medial meniscus (though lateral meniscus is actually more commonly involved)
133
Valgus vs varus
134
What is developmental dysplasia of the hip, and what is a major risk factor?
It’s a condition of abnormal acetabulum development in newborns, leading to hip instability or dislocation.
A major risk factor is breech presentation.
135
How is developmental dysplasia of the hip diagnosed?
Screened using Ortolani and Barlow maneuvers (detecting a “clunk” from dislocation/reduction).
Confirmed by ultrasound (x-ray is avoided until ~4–6 months due to unossified cartilage).
136
What is the most common cause of short-limbed dwarfism?
Achondroplasia, characterized by failure of longitudinal bone growth (endochondral ossification), resulting in short limbs with a relatively large head.
137
What are the risk factors and inheritance pattern of achondroplasia?
Associated with increased paternal age
Inherited in an autosomal dominant manner with full penetrance
Homozygosity is lethal
85% of cases are sporadic mutations
138
What is osteoporosis and what causes it?
Osteoporosis is the loss of trabecular and cortical bone mass with normal bone mineralization and labs. It is due to ↑ bone resorption, often from ↑ osteoclast activity.
139
What are common risk factors for osteoporosis?
↓ Estrogen levels
Advanced age
Cigarette smoking
Low BMI
Chronic steroid use
Prolonged immobility or microgravity exposure
140
What medical conditions are associated with secondary osteoporosis?
Hyperparathyroidism
Hyperthyroidism
Multiple myeloma
Malabsorption syndromes
Anorexia
Chronic alcohol or anticonvulsant use
141
How is osteoporosis diagnosed?
By bone mineral density (DEXA scan) with a T-score ≤ –2.5, or by a fragility fracture (e.g., from standing height) at the hip or vertebra.
142
When is screening for osteoporosis recommended?
One-time DEXA scan is recommended for females ≥ 65 years old.
143
What are vertebral compression fractures, and how do they present?
Vertebral compression fractures occur when the vertebral body collapses, often due to osteoporosis.
They typically present with:
Acute back pain
Loss of height
Kyphosis (forward spine curvature)
The most common type is a compression wedge fracture, where the front of the vertebra collapses more than the back.
144
What is the underlying defect in osteopetrosis?
It’s caused by defective osteoclasts, often due to carbonic anhydrase II mutations, which impair the ability to create the acidic environment necessary for bone resorption. This leads to thickened, dense, but brittle bones.
145
What are the clinical features and complications of osteopetrosis?
Bone marrow space is filled with overgrown bone → pancytopenia and extramedullary hematopoiesis
Can cause cranial nerve impingement and palsies due to narrowed foramina
X-ray shows diffuse symmetric sclerosis ("stone bone")
146
What is a potentially curative treatment for osteopetrosis?
Bone marrow transplant, since osteoclasts are derived from monocytes, can restore bone resorption function.
147
What causes osteomalacia and rickets, and what is the underlying mechanism?
Most commonly caused by vitamin D deficiency, leading to defective mineralization of osteoid in adults (osteomalacia) and growth plates in children (rickets).
↓ Vitamin D → ↓ serum Ca²⁺ → ↑ PTH → **↓ serum phosphate** → defective bone mineralization.
148
What lab findings are seen in rickets/osteomalacia?
↓ Serum calcium
↓ Serum phosphate
↑ PTH
↑ Alkaline phosphatase (ALP) due to osteoblast hyperactivity
149
What causes Paget disease of bone (osteitis deformans)?
It results from ↑ osteoclastic activity, followed by ↑ osteoblastic activity that produces disorganized, poor-quality bone.
150
What are two classic physical findings in Paget disease of the bone?
Increased hat size due to skull thickening
Hearing loss due to skull bone deformity
151
What are the stages of Paget disease and the predominant cells in each?
Lytic (early): osteoclasts
Mixed (intermediate): osteoclasts + osteoblasts
Sclerotic/blastic (late): osteoblasts
152
What does elevated alkaline phosphatase (ALP) indicate in the musculoskeletal system?
ALP is a marker of osteoblastic activity. Elevated ALP suggests increased bone formation or remodeling, seen in conditions like:
Paget disease
Healing fractures
Osteomalacia/rickets
Bone metastases with osteoblastic activity
153
What are the characteristic lab findings in Paget disease of bone?
↑ Alkaline phosphatase (ALP) – due to increased osteoblastic activity
Normal serum calcium
Normal serum phosphate
Normal parathyroid hormone (PTH)
154
