Equine Lameness Flashcards

Question

Describe hoof anatomy in relation to laminitis

Answer 1

- Lamellae: 600 primary epidermal lamellae & 150 secondary epidermal lamellae - Hoof-Lamellar Interface: Balances downward wt. bearing force, upward ground reaction force & caudal/proximal pull of the deep digital flexor tendon - Basement Membrane: Location: Lies between 2nd epidermal lamellae (SEL) & 2nd Dermal Lamellae (SDL) Role: Influences GF & nutrient exchange, regulates keratinocyte migration, structural role Connection: Basal cells are anchored to the BM by hemidesmosomes; attach SEL to P3 SDL Normal Growth: Degradation by MMP’s & resynth by basal cells in a normal balance Components: Collagen IV & VII Is coated w/ glycoproteins (Laminin) which has receptors for GF, cytokines & adhesion molecules - Vasculature: P3 Centre: Digital A./V. anastomose in a terminal arch w/ osseous foramen to allow small vessels to enter the sub-lamellar dermis bed. Dorsal Laminae & Solar Plexus: Last to be perfused; ↑ susceptibility due to hypovascularity in dorsal laminae & solar laminae compressed by P3 rotation/sinking Solar P3: No perforating vascular canal (No BV penetrate solar surface of P3); sole is perfused from circumflex & bulbar a. Lamellae: Multiple connecting complex vascular networks

Answer 2

Pathogenesis: - Anabolic < Catabolic processes (MMP 2 & 9 via inflam cells) & glucose deprivation (In-vitro) - Degradation of laminin & Collagen IV - BM detachment and separation from epidermal lamellae → Laminitis *Breakdown of the lamellar basement membrane is a KEY feature of acute laminitis - Laminin (glycoprotein) and collagen IV are degraded – BM progressively loses its attachment to the basal cells and strips away from the epidermal lamellae resulting in failure of the hoof-lamellar Key Alterations of Hoof- P3 Lamellar Interface: - Inflam cell infiltration in ass. w/ disrupted Basement membrane - Lengthening & narrowing of Primary & Secondary epidermal lamellae - Alteration in epidermal & basal cells - ↓ Mechanical properties by 40-60% CS: - Stance: Characteristic sawhorse, rocking back on heels, shifting weight - Lameness/Gait: Debilitating bilateral forelimb lameness, stiff gait or lame on turns - Exam: Flat/convex sole, ↑ digital pulses & heat, reluctant to lift limbs, +ve hoof test at toe - Other: Elevated HR/RR, Sx of endotoxaemia, endocrinology diseases, severe pain, etc.

Answer 3

1. Septic Laminitis: Causes: Grain overload, metritis, retained foetal membranes, Nutri (Se, Oxalates), Toxic (Avo, Walnut), pleuro-pneumonia, Anterior enteritis, LC volvulus, colitis Endotoxic Cause: Gram -ve LPS Stimulate: IL1, IL8, TNF, TBA2, PGF2, PGE2, iNOS, COX2, PMN, MMP Path: Vasoconstriction, vascular leakage, coagulation, hypotension, hypoperfusion Exotoxic Cause: Gram +ve streptococcus faecalis spp. Stimulate: MMP2 & 9, Thermolysin, Strep. Pyrogenic exotoxin B 2. Endocrinopathic Laminitis: Cause: o PPID (pars pituitary intermedia dysfunction) o EMS (Equine Metabolic Syndrome) o Euglycemic hyperinsulinemia: Laminitis <48hrs o Hyperglycaemia (CHO induced): Separation of lamellar dermal/epidermal interface o Hyperinsulinemia: Elongated lamellae & ↓ density of basement membrane hemidesmosomes Associated Drugs: o Corticosteroids: cause BV constriction, inhibit NO synthase, alteres insulin, influences terminal cornification of laminae o Triamcinolone: Causes Prolongerd period (3-4d) of hyperglycemia/insulinaemia/triglyceridaemia. o Dexamethasone Prevention: Avoid use in risky horses with above conditions, under 18-20mg Triamcinolone!! 3. Concussive/Mechanical Overload Laminitis Cause: Contralateral limb overload, over-exercise Timing: Sometimes takes months or days PF: Weak laminar attachment Path: Pain-mediated stress ↑ cortisol/inflam → BM (basement membrane) damage → Exacerbated by MMP release

Answer 4

Stages: 1. Developmental (24-60hrs): Prior to lameness 2. Acute (24-72hrs): Onset of lameness 3. Subacute: No radiographic sins of digital collapse 4. Chronic: Radiographic/Physical Sx of rotation/collapse

Answer 5

- Lameness: 1: Shifting lameness, lifts hooves, lame on trot 2: Stiff gait on walk, lifts hooves 3: Reluctant to move/lift hooves 4: Requires force to move/recumbent - Radiology HLZ: Hoof Lamellar Zone P3: Angle of Rotation Sole Thickness/Sole Depth FD: Founder distance: Distance from extensor process to coronet 1: H-L zone - <20mm, FD - <10-14mm, P3 angle – 5-90, Sole depth – Normal 2: H-L zone – 20-25mm, FD – 15-16mm, P3 angle – 10-140, Sole depth – Decreased 3: H-L zone – 25-30mm, FD – >16mm, P3 angle – >150, Sole depth – Greatly Decreased 4: H-L zone – >30mm, FD – >16mm, P3 angle – >15-2-0, Sole depth – P3 penetrates sole - Chronic Cases o Abnormal growth rings o Closer at toe cf. heel o Excess heel & thick sole o Phalangeal rotation Consequences: - P3 sinking: All lamellae fail simultaneously - P3 (Capsular) Rotation: Dorsal lamellae failure - Digital Ischaemia: Occurs: 8-12hrs in the developmental phase just prior to lameness/acute phase Cause: Blood flow varies, ↑ via AV-shunts but ↓ digital perfusion - Sole Penetration by P3 Tx: Egg-bar shoe, topical management, Tx of septic pedal osteitis, Ab, DDFT tenotomy

Answer 6

1. Treat or Remove Underlying Cause 2. Analgesia Types: NSAIDS (PBZ, Flunixin), A2 agents, Gabapentin, Opiods, Ketamine, Epidural, NB Sources of Pain: Inflam mediators, ↑ submural hoof pressure, ↑ intraoessous P3 pressure, Ischaemic/reperfusion episode, laminar/vascular/neural tearing 3. Hoof Support (Farriery, Surgery, Medical) a) Pharmacological: Acetylpromazine (ACP): Sedative, vasodilator, ↑ blood flow to digit but not dorsal laminae Nitric oxide (NO): NOS & Arginine → vascular smooth mm. → digital vasodilation but unknown laminae flow Polymixin B: Binds to LPS of endotoxin Pentoxyphylline (Rheologic): ↓ TNFa & ↑ RBC deformability, no effect on blood flow Heparin (Anticoagulant): Binds to ATIII to ↓ severity/incidence of laminitis +- haemorrhage Flunixin: Analgesia, ameliorates CS of endotoxaemia Aspirin: Bind platelets & ↓ thrombosis Corticosteroids: ↓ COX & NO & Epidermal cell metabolism is contraindicated Dimethylsulphoxide (DMSO): Free radical scavenger with unknown efficacy MMP Inhibitors: Batimastat, in-vitro efficacy only Local Anaesthetics: ↓ neurogenic vasoconstriction, contribute to mechanical failure → lignocaine may delay CS b) Digital Support Role: Distribute weight evenly between sole + wall & ↓DDFT tension Method: Cut foam pad and achieve a solar angle of 25o taped to sole with Elastoplast Includes: Closed cell foam rubber, Styrofoam, sand bedding (Unloads dorsal laminae) c) Farriery Shoe Type: Heart bar shoe Subacute & Chronic: Grow more heel cf toe and sole thickness o Remove excess heel to re-align P3 with hoof capsule o +- PBZ post trim o Unload dorsal hoof wall via removing excess toe & rolling toe o Improve digital stability with heart bar (Wide webbed +- 3-5o) shoe + sole support 4. Radiographic Assessment Views: Min LM & DP Assess: H-L zone, P3 rotation (Capsular, phalangeal), Sole thickness, Bony modelling, Air/radiolucent lines, P3 sinking relative to coronet Normal H-L Zone: 18-20mm (TB/QH); may be normal in acute laminitis, compare limbs Signs that Laminitis has Stabilised: Increasing sole thickness Gas Line: Type 1 – Acute <24hrs (Coronet separation), Type 2 – Mummified laminae Important: Angles are estimates subject to 1-2o variation each measurement 5. Cryotherapy Indication: Only if caught early (Prior to CS) or if at risk Method: Submerge hooves in 1 degree C 100kg ice/water bath for >48-72hrs till hoof temp <10o Role: ↓ Clinical & histopathology severity, ↓ MMP & blood flow to 10-15% non-iced hooves Pathogenesis: Vasoconstriction ↓ delivery of trigger factors & ↓ laminae cell metabolism Dis: Hard in clinic, risk of reflex vasodilation if not done continuously, ice changed q2hr AVOID: Use of dry ice packs, monitor for thermal skin injury Px: - Determine by: Degree of improvement, rapid stabilisation of P3 rotation, ↑ sole thickness - Return to race, RTR: 25% - Pasture sound: 50% - E&D: 25%

Answer 7

1. Sedation Role: Improve safety for personnel & horse Dose: Enough to reduce stress w/o ataxia Drugs: - Xylazine: Low dose, short acting - Detomidine: Longer acting - ACP: Longer +- hypotension, ↓ sedation - Opioids: Butorphanol & Morphine 2. Analgesia Dose: Not much as makes diagnosis harder Drugs: PBZ, Flunixin 3. Restraint: Sit on horses head if recumbent, nose twitch 4. Limb Immobilisation - Immobilise joint proximal and distal to the limb Role: ↓ mechanical force on limb but horse must still be ambulatory Materials: Cotton wool, gauze bandage, Elastoplast, duct tape, ½ PVC pipe, timber heel elevation Robert Jones RJB Method: Place Elastoplast stirrups medially & laterally from proximal to distal point → place x3 layers of cotton wool → fold stirrups in and apply Elastoplast over entire bandage → tape splint externally ensuring it goes to ground surface at a size of 2-3x diameter of leg Splint devices: Kimzey splint, comppression/ski boot

Answer 8

- Distal limb/Distal Cannon Aim: Align dorsal cortices of the phalanges with the cannon bone Methods: Raised heel with dorsal splint, kimzey splint, compression boot Includes: Phalangeal fractures, Suspensory rupture, biaxial sesamoid fracture, distal sesamoidean ligament rupture, Distal condylar fracture, SDFT/DDFT laceration

Answer 9

P1/P2 & Distal MC/MT3 Fractures Method: Dorsal splint w/ raised heels Aim: Align dorsal cortices of P2/P1/MC3

Answer 10

Sagittal P1 Fracture Origin: At the mid-sagittal groove Dx: lateromedial (LM) views, multiple obliques if non-displaced - Metacarpus Method: RJB, Lateral & palmar splint, dorsal splint, dorsal Kimzey splint Method (Spiral): Lag plate & full limb cast/Kimzey splint - Carpal Fx Complications: May be comminuted, joint instability or collapse Method: Immobilise from proximal radius distally

Answer 11

Location: Includes fractures between the carpus & elbow or between hock & stifle Method: o Just RJB (Safer?) o RJB → Full limb dorsal/palmar splint (From elbow to heels) & lateral splint (Extends proximal from withers along shoulder to the hoof) OR medial splint→ splints should be arranged at 90o to each other Indication: MC3 Fx, Radial Fx, Radial nerve palsy, Olecranon Fx Role: Prevent abduction of limb

Answer 12

Ulna/Olecranon: --> Disruption to triceps apparatus so horse unable to fix carpus Full limb RJ bandage Palmar splint from elbow to heel CS: Present with dropped elbow DDx: Radial nerve palsy Other treatment: - Foals: Apophyseal Fx – Sx repair - Adults: Displaced/articular – Sx repair, non-displaced/articular – Conservative Humeral/Scapula: - Unable to immobilise - Rely on musculature Greater tubercule fracture: - Large: Lag screw - Small: remove Diaphyseal fracture: - Marked local swelling/haematoma often seen - <150kg: Plate fixation/stack pin/IM Nail - Conservative if non-displaced/incomplete Scapula Fx Locations: Supraglenoid, scapula neck Tx: Unable to immobilise, rely on musculature – depends on type but conservative vs Sx - Supraglenoid: Inability to advance limb, Tx via lag scew if articular/large or remove if small/non-articular, 30-50% RTF Dx: Hard as can obtain standing humerus radiographs but scapula is difficult

Answer 13

- Hindlimb Phalanges Method: RJB & Dorsal Kimzey splint Or plantar splint (Better dorsal cortical alignment) - Metatarsus/Tarsus Method: RJB +- Lateral splint extending proximally along thigh Dis: Horses hate inability to flex hock, splints can slip/break (Maybe better just RJB) - Tarsus/Tibia Method: RJB & Lateral splint from tuber coxae to hoof Dis: Slip often due to stifle flexion & reciprocal apparatus, not always tolerated

Answer 14

- Secondary to fall or propagation stress fracture - Acute/severe lameness - Pelvic asymmetry - Unable to immobilise Diagnosis: - Radiography - GA vs standing VD - Ultrasound - Transrectal/transvaginal exam --> palpation/u/sound Treatment: Conservative, confine, risk of contralateral limb laminitis

Answer 15

SDFT and DDFT originate from caudal humerus or femur. This means it is impossible to immobilise the origins of these tendons with splints/casts SDFT rupture: - Fetlock drops SDFT & DDFT: Rupture: Fetlock drops & Toe flips up SDFT, DDFT & SL rupture: Fetlock on ground & Toe flips up. Flexor tendon lacerations: Acute: Wound management, splint, surgical repair Assess vascular injury to limb: Doppler ultrasound Cast: 4-6 weeks Reduction in support 4-6 months 12 months rehabilitation Extensor tendon lacerations: - Suture and cast application but not necessary - Often not suturable due to trauma to tendon ends - RJ Bandage + Dorsal splint initially until horse learns how to place limb Suspensory ligament disruption: - Dropped fetlock appearance - Chronic progressive suspensory degeneration. Rupture/acute disruption during race/exercise Treatment: Splinting: Months to fibrose, surgical fetlock arthrodesis, salvage procedures

Answer 16

Cause: Non-adaptive excercise bone remodelling Hosts: 2-3 year old TB/SB often unraced CS: Acute lameness grade 4/5 post gallop/race → often improve <2wks → galloping again progresses Fx Locations: Caudoproximal/distal humerus, mid/caudoproximal tibia, scapulal Dx: Scintigraphy, radiography (Often -ve except in tibia Fx) Tx: 2m box rest & 2m in a small yard Px: Great

Answer 17

Tx: - <250kg - Sx repair via double plate fixation - Comminuted or open - E&D - Non-displaced – Conservative Tx, box rest for 3-6m (Fair Px)

Answer 18

Scapulohumeral Joint OC: Varied lameness, usually <1yo, Tx via arthroscopic removal, Px – 50% RTR better w/ small lesions Dysplasia Scaulohumeral joint: Usually in Shetlands with joint instability, Tx via arthrodesis, Px - Poor

Answer 19

Anatomy - Joints: Femoropatella (FP), Medial & lateral femerotibial (Cr. & Cd. Pouches) (MFT) - Communications: 60% FP & MFT, 25% FP & LFT communicate CS: Medial FT joint effusion, FP joint effusion

Answer 20

Cause: Related to Osteochondrosis, trauma leading to full thickness cartilage lesions may cause SCBC CS: Marked 3/5 acute lameness, +ve spavin test Local: Blocks to MFT or FP IA joint Location: Medial femoral condyle, 65% are bilateral Dx: Cr-Cd or CdLat-CrMed radiographs Tx: Re-establish subchondral bone plate - Small Cysts/Cloaca: Intra-lesional CCsteroids via arthroscopy, RTR 55% - Larger Cysts/Cloaca: Debride & use platelet rich plasma, bone marrow supernatant, culture chondrocytes, 50-70% RTF - Lag screw across cyst - Conservative: 64% RTR

Answer 21

Hosts: Young horses with straight/upright hindlimb conformation +- -ve plantar angle of hoof/P3 Limb locked in rigid extension with toe drag Cs: New to work, locking in the morning, drag toe, weak quads & snapping w/ exaggerated flexion Pathogenesis: Patella catches over the medial femoral trochlear Medial patella ligament catches over medial femoral trochlear. Dx: - Radiology - Assess conformation - Conservative Tx: - Graded exercise of straight trots 4-6wks, PBZ PRN, stable - Medial patella lig. Fenestration: Needle stabs in lig., maybe better for primary Desmitis - Medial patella desmotomy surgery: Pre-Op: Standing sedation & Local Location: Transect near tibia attachment; palpate medial patella ligament. Use Kelly’s behind ligament & avoid the Collaterals lig (Cd.) Don't go too caudal as it can damage medial collateral ligament --> Joint instability and persistent lameness Post-op: Close skin only, 8wks rest before gradual work Px: 90% RTR Risks: Joint instability, distal patella fragmentation (Due to transecting medial collateral) Tx: Back horse up & push up + medially on patella

Answer 22

Cause: Congenital conformation fault Hosts: Mini’s & Shetlands Ddx: UFP --> Upward fixation patella Type: Usually lateral luxation Dx: Palpate lateral patella in walk, manual reduction, CdCr view radiograph Tx: Sx repair – medial imbrication of para-patella fascia & sartorius m.

Answer 23

- Ruptured Peroneus Tertius Cause: Traumatic rupture Location: Distal femur → dorsal tibia → prox. MT3 & tarsals CS: Varied lameness, soft tissue swelling of tibia, *Characteristic finding: Can flex and extend hock without flexing extending stifle and lax SDFT Tx: Box rest 4wks, hand walk, 3m spell Px: Good if no avulsion fracture of femoral origin

Answer 24

Cause: Proximal femoral Fx or acetabular fx CS: Hip luxation with severe lameness, stand w/ distal limb externally rotated Tx: Femoral head ostectomy (<100kg), open reduction & toggle pin repair (Mini’s/Shetlands)

Answer 25

Cause: a) 40% Vertebral lesions: o Performance Horses: Impinging dorsal spinous process (85%) CS: May block to local infiltration Location: T15-17 Tx: Intralesional CCsteroid (6wks), Sx resection + 12m rehab (70% RTF) o Fx of thoracic spinous processes; Tx: Conservative Tx or Sx remval if open/displaced o Young TB: Caudal thoracic & lumbar stress b) 40% Soft tissue problems: Rhabdomyolysis, M. pain, supraspinous lig. c) 20% No primary pathology; 2nd to hind limb lameness CS: Poor performance, behaviour change Dx: Rule out others, scintigraphy

Answer 26

Cause: Rupture of ventral ligament attachments CS: Affected side is higher, acute severe lameness, painful palpation Tx: 6-12m spell Px: May develop persistent pain, 70% RTF

Answer 27

CS: Characteristic hindlimb adduction & raising Peripheral Neuropathy Cause: 2nd to unidentified toxin via hypochoeris radiacata (Dandelion) Pathogenesis: ↓ Electromyographic activity in deep peroneal n. & lateral DE & ↑ in long DE (Digital extensor tendon) Px: 80% recover within 18m of removal Tx: Sx transection of lateral DE Traumatic Cause: 2nd to proximal MT3 transection of extensor tendons → adherence of DE MT3 causes feedback to lateral DE via stretch receptors (Golgi apparatus) Tx: Sx transection of lateral DE] Px: Varied, improves over wks, better cf. peripheral

Answer 28

Cause: Trauma (Sliding stops, falling back) → fibrosis/ossification of the semimembranosus/tendinosis (Hamstring m.) muscle bellies CS: Goose stepping T' x: Sx transection of belly & fibrotic mass +- Penrose 6-8wks Px: Good, 70-80% RTR

Answer 29

Capped Elbow AKA Shoe Boil Is an inflammatory swelling of the subcutaneous bursa over the olecranon process Cause: Trauma – lying on hard floors, falling, shoe’s projecting beyond heels Cs: Variable lameness, painful to palpate, fluctuating & soft → firm & fibrous +- Abscess (Cr.) Tx: o Acute cases: Topical DMSO +- Aseptic drainage & CCsteroid injection + Antibiotics o Chronic: Surgical drainage & pack with iodine gauze +- drain

Answer 30

CS: Muscle atrophy of affected regions Radial: Includes the Triceps (Elbow extensor), Forearm extensor tendons → dropped elbow appearance Brachial Plexus: More severe gait abnormality Suprascapular n. (Sweeny): Incl. infraspinatus (Shoulder stabiliser) & supraspinatus mm. → lateral shoulder subluxation during weight bearing Method: o Nerve regrowth is at 1mm/d but m. mass is slower to return o Confinement & assisted weight bearing Px: 6-12m return to normal gait, Sweeney – 50% RTR

Answer 31

Bicipital Tendonitis/Bursitis CS: Acute or chronic, Lameness 3-4/5, varied local Sx Local: Bicipital bursa Dx: US - ↑ CSA, fibre disruption Tx: Intra thecal CCsteroids & HA, Tenoscopic debridement & transection of tendonous band from asc. Pectoral m. & lesser tubercle Px: Guarded if Chronic

Answer 32

CS: Acute lameness, joint effusion, pain on fetlock flexion Dx: Radiography Local: IA fetlock joint block, Low 4/6 point nerve block Tx: Arthroscopic removal/internal fixation

Answer 33

Location: Usually dorsomedial proximal P1, 30% are bilateral Tx: - Acute: Arthroscopic removal; 70-80% RTR, poorer Px If cartilage score lines - Chronic: Questionable if removal is worth it Palmar/Planter Proximal P1 Type 1: - Location: Hindlimb > forelimb, axial intra-articular fragments of a small size - Cause: Fracture > OCD (Osteochondritis dissecans) - Px: 60-90% RTR - Tx: Arthroscopic removal - Dx: 20 degree PrDiOblque Type 2: - Location: Abaxial partially articular fragments of a larger size - Tx: May heal on own, if persists remove via scope +- cut down, if large – lag screw

Answer 34

Pathogenesis: increased pull from SL & distal sesamoidean ligaments induces bone modelling responses and subsequent lysis, widening the vascular channels of the PSB --> PSB Fractures CS: Lameness, pain on fetlock flexion & palpation of PSB, SL branch enlargement & pain on palpation Local: Blocks to low 4/6 point NB Dx: - Radiography: 4 views (obliques!), see >2x vascular channels or 1x over >2mm - US: Suspensory ligament branches Tx: Rest for 2-6m and Rx radiographs prior to return to exercise

Answer 35

Pathogenesis: Increased pull from SL & DSL induces bone modelling responses and subsequent lysis Location: Apical fractures are the most common – involve the proximal 1/3rd of PSB (proximal sesamoid bone) CS: Acute severe lameness +- SL swelling & pain Tx: - Apical: Are articular, require arthroscopic/arthrotomy removal, 70% RTR - Midbody, basal & comminuted: Worse px, may require internal fixation - Bilateral Fx: Fetlock arthrodesis due to disruption of suspensory apparatus - Untreated: Heal with fibrous union → refracture or disrupt suspensory apparatus

Answer 36

Incidence: Most common cause of lameness CS: - Lameness: Insidious and progressive, varied but usually affects multiple limbs +- severe - Exam: +ve joint flexion, joint effusion, fetlock capsular fibrosis, reduced range of motion - Local: IA fetlock, Low 4/6 point block, biaxial palmar/plantar MC3/MT3 Nerve block Dx: Radiography +- MRI & Scinitgraphy useful in earlier stage of disease when changes are subtle

Answer 37

Radiographic changes: - Subchondral modelling (Lysis/Sclerosis) - Dorsal synovial pad enlargement - Narrowing of joint space - Palmar condylar flattening of MC3 - Bone spur/osteophyte (P1, MC/MT3 & PSB) - Supracondylar lysis: Measure via LM view → 10cm prox. thickness of cannon cf. prox. condyles. >4mm is significant - Synovial pad proliferation/Villonodular synovitis: Cause: Chronic synovitis Sx: Proliferation of dorsal synovial pad & supracondylar lysis +- ossified pad/OC fragments Tx: Arthroscopic resection of synovial pad & IA medication

Answer 38

Location: Affects palmar/Plantar MC3/MT3 Hosts: Racing TB & SB CS: Poor performance, behaviours change, progression to lameness usually bilateral/multi limbed Local: Varied response +- Palmar/plantar MC/MT block Dx: Flexed DP radiography, scintigraphy more sensitive (Subchondral lysis/condylar lysis) Tx: IA medication (Varied response), 3m spell, allow yard/paddock exercise

Answer 39

Cause: Developmental Path: - Subchondral Lucency Tx: Arthroscopic debridement & intralesional Tx Px: 45-50% dep. Same as below - Subchondral Bone Cysts Location: MC3, typically medial condyle Complication: Progress to bone cyst in young Tx: Arthroscopic debridement & intralesional CCsteroids/biologics Dx: Not always obvious on flexed LM, require DP angle Px: 40-50% RTF depending on lesion size, location & OA fetlock - Sagittal Ridge OCD’s & Fragments Type 1: Is Lucency of the sagittal ridge w/ defect or flattening Hosts: Yearlings Location: 30% forelimbs CS: Asymptomatic Dx: Monitor for filling in Type 2: Is a non-displaced fragment within the Lucency (OCD) CS: Fetlock effusion, varied lameness, +ve fetlock flexion Type 3: Is a displaced fragment (OCD) CS: Same as type 2 but more severe Tx: Arthroscopic debridement – rarely fills in so many managed conservatively (IA meds)

Answer 40

Pathogenesis: Start as microfractures that extend through subchondral bone trabeculae proximal/distal CS: - Lameness: Acute severe after exercise, general swelling of fetlock, cannon, pastern - Exam: Pain on palpation, marked + flexion response (DON’T do if suspected) - Local: DON’T do if suspected Dx: Support limb & radiograph (Multi obliques, check condyle for communication via Flex/125 DP) Locations: Hindlimb – Lateral condyle, Forelimb – Medial condyle Type: Usually non-displaced, spiral proximally Lateral Condylar Fx: Tx: - Incomplete: Conservative Tx for economics → monitor carefully to avoid propagation - Ideal: Lag screw fixation (3 x 4.5mm cortical screws) & limb cast + 4-6m rehab Px: 70% RTR but is affected by comminution & fetlock OA Sagittal P1 Fx Originate at mid sagittal groove of P1 CS: Acute severe lameness after exercise, chronic may cause intermittent lameness +- propagation Classifications: - Incomplete – short - Complete – exit at lateral cortex - Cr. – Periosteal bone formation dorsal proximal P1 (LM view) Tx: Lag screw repair & distal limb cast P2 Fx Cause: Axial torsional forces in exercise CS: Acute severe lameness, ‘crack’ at time of Fx Dx: Multiple oblique views (Comminuted) Tx: - Internal Fixation: Optimal, double plate & lag screw + distal limb cast, Px: 40% RTF - Conservative: Risk of further displacement and contralateral laminitis → dorsal splint & heel

Answer 41

CS: Lameness varies but is progresses, firm swelling around pastern joint, +ve distal limb flexion Local: ABSANB, IA Pastern joint Dx: Radiography – Osteophytes/spurs, capsule enthesophytes, cartilage thinning, SC lysis & collapse Consequences: Many progress to high ringbone aka severe irreversible OA Tx: IA medication, farriery (Rocker shoe), Sx arthrodesis (3 lag screws), Distal limb cast 2-4wks Px: Takes 12m for remodelling, 50% RTF forelimb, 70% RTF Hindlimb

Answer 42

Location: - Distal P1 Axial: Common and rarely cause lameness - Distal P1Abaxial/Condylar: More concerning and may cause OA - Proximal P2: May cause lameness and OA if they become articular Tx: Forage/curettage, conservative, monitor Px: Fair with no OA

Answer 43

Pathogenesis: Thickened PAL (>2mm) constricts the flexor tendons in the DDFT causing lameness CS: - Effusion of DDFT - Pain on palpation of PAL +- Flexor tendon - +ve distal limb flexion tests - Local: Low 4/6 point, IA DDFT Dx: US (SDDFT, DDFT) Px: 70-80% RTF Tx: Early stages - rest & graded exercise, Tenoscopic Sx transection of annular ligament

Answer 44

Risk Factors: - Conformation: o Long toe & underslung heels → increase effusion & Fx risks o Longer scapular & slight carpal valgus → reduced risk of carpal injury - Type of Exercise: Racehorses, reining/roping CS: - Lameness: Often bilateral, stiff & shuffling gait, ↓ carpal flexion during anterior stride - Visual: Joint effusion/distension either in the radiocarpal or middle carpal (Communicates with carpometacarpal but has a tight capsule so effusion is not obvious) - Exam: View from a 450 DLPM (dorsolateral to palmaromedial) aspect, palpate for effusion & bone, +ve carpal flexion - Local: Radiocarpal/Middle joint → block Sound within <15m, if >30m suspect outer injury, e.g., PSL Desmitis. Lameness outside of carpus due to diffusion of local anaesthetic agent. Common sites of carpal injury: Dorsomedial joint aspect, middle carpal, radiocarpal joint

Answer 45

Location: Dorsomedial joint aspect, Middle carpal > Radiocarpal joint, e.g., OC Fragmentation Distal RC > Proximal C3 > Distal IC > Distal lateral radius (SB have similar C3 & RC incidence) Dx: Palpate individual bones Distal Radiocarpal OC Fx Px: Acute – Good for RTR with arthroscopic removal, Chronic . – Depend on cartilage and subchondral bone malacia Dx: Best views DLPMO & FLM Ddx: Osteophyte – Aren’t detached C3 Slab Fx - Frontal Slab Dx: Skyline distal row view, Standing LM view Px: 60-70% RTR Incomplete: One articular surface, Tx – Arthroscopic removal Complete: Both articular surface, Tx – Lag screw fixation >10mm thickness - Sagittal Slab Location: Radial or intermediate slab Dx: Skyline distal row view Type: Often chronic Tx: Lag screw fixation, arthroscopic debridement, conservative Px: 60-70% RTR, has inherent stability Palmar Carpal Fx PX: Small – Fair, Large/Comminuted – Poor Tx: Arthroscopic removal Accessory Carpal Bone Fx Location: Mainly frontal plane Px: Varied Sx success, Comminuted has poorer Px Cause: Avulsion of palmar attachment, crushed between carpal bones, Trauma (Kick) Tx: Conservative 3-6m confinement heals with fibrous union, Sx fixation

Answer 46

Severity of Lesions: Synovitis/capsulitis → Score lines → Cartilage ulceration → SC bone erosion/Fx Cartilage & SC Bone Injury - Grade 1: <5mm Cartilage loss - Grade 2: <30% CL - Grade 3: 30-50% CL - Grade 4: >50% CLS & SCBone loss subchondral bone loss - Px: Grade 1-2 – 70-80% RTR, > Grade 3 – 50-60% RTR Medial Intercarpal Ligament Injury - Grade 1: Few torn fibres - Grade 2: <1/3rd torn fibres - Grade 3: <2/3rd torn fibres - Grade 4: 100% torn fibres - Px: Grades 2-4 have -ve effect on RTR, Cartilage & SCB loss

Answer 47

- Dorsomedial Carpal Disease: Cause: Exercise induced bone modelling response of dorsal cortical radiocarpal bone via body weight of horse and upward ground reaction force Dx: 300 DLPMO Px: Poor Px indicator in young horses for athletic soundness - 3rd Carpal Bone Dz Dx: 300 DPrDiO (Skyline) Cause: Subchondral bone failure → Lucency & sclerosis of radial facet Consequence: May cause slab Fx - Physitis Hosts: Fast growing weanlings-yearling Path: Lysis, sclerosis, widening of physis Tx: Rest if painful, dietary restriction, PBZ if lame, monitor for Flexor tendon contraction - Carpal Bone Cyst Incidence: Rare <1% Locations: Distal radius > Ulna, RC CS: Lamer if articular Cause: Developmental/OCD, Traumatic Tx: Sx curettage, IA (Intalesional) CCsteroids -Other Carpal Fx Location: Often multiple carpal bones Cause: Trauma Tx: Selective lag screw fixation, partial/pan carpal arthrodesis (Salvage) - Synovitis/Capsulitis CS: +ve flexion, synovial effusion, NO radiographic evidence Local: IA Carpal Tx: 6-8wk spell, IA meds, systemic pentosan polysulphate or oral joint medication

Answer 48

Are enlargements of the splint bones that may cause lameness → may go unnoticed & callous ↑ Pathogenesis: 1. Mild Trauma Concussion a) Sub-periosteal haematoma, periosteal reaction & thickening → Remodels w/o callus b) Peri-osteal Callous, models overtime 2. Severe Trauma/Stress/Microfracture a) Bony reaction/callous → Horse rested (Heals/models) or Sx removal +- Stabilised b) Oblique Fx forms large callous → Sx removal +- Stabilised Reasons for Sx Removal: - Comminuted Fx - Cosmetic - Septic osteitis/Sequestrum - Functional: Callus impinging on SL causing Desmitis (Esp. Proximal MC2 splints)

Answer 49

Role: Important weight bearing articulation with C2 Px: Good Tx: Can only remove distal 2/3rd w/o internal fixation of remaining MC2, 3-4m spell Hindlimb Lateral Splint – MT4 Cause: Fracture common with trauma Type: Often open & comminuted Complication: Risk of sepsis (TMTj) Tx: 3-4m spell, can remove entire MT4 Px: Good

Answer 50

Hosts: Young TB/SB Cause: After 1st gallop or trial – cyclic loading of MC3 Path: Stress-modelling of the dorsomedial MC3 cortex Pathogenesis: High strain cyclic fatigue → ↓ Bone stiffness via remodelling BUT shin soreness if cyclic fatigue excess modelling response → Fatigued bone Radiograph: - Microfractures in the middle/distal 1/3rd of MC3 are not seen - Instead see periosteal new bone callous at the dorsomedial cortex Tx: Spell 3m, modify training w/ short fast runs 2x/wk, ↓ canter (Compression), ↑ gallop (Tension) Px: bone modelling cycle takes 110d for replacement

Answer 51

- Caudal Radius Osteochondroma Is a bony exostosis covered in hyaline cartilage arising from distal radial physis Consequence: Impinge into carpal sheath & DDFT → Carpal sheath effusion/haemorrhage Tx: Surgical removal via direct approach or tenoscopy Px: Good if Dx early - Stress Fractures Complication: 12% horses develop saucer Fx at dorsolateral cortex of MC3 Dx: Periosteal callous at dorsomedial MC3 cortex, scintigraphy detects sooner Tx: Cortical bone screw removed at 60d, 2-3m rest before training - Proximal Palmar MC3/MT3 Stress or Avulsion Fx Cause: Associated with proximal suspensory ligament Desmitis Dx: Radiography & scintigraphy Tx: Osteostixis if no response to conservative - Septic Osteitis/Sequestration Location: MC/MT3 prone to sequestration Cause: 2nd to trauma due to minimal soft tissue protection & perisoteal BV’s easily damaged (Outer 1/3rd cortex & subperiosteal venous drainage) Dx: Radiography – only at 10-14d Tx: Sx removal - MC3/MT3 Condylar Fracture Cause: Post gallop/race CS: Non wt. bearing lameness Location: Lateral or medial condyle, Sagittal ridge (All Non-displaced spiral) Type: Typically non-displaced spiral, medial condyle may be Y-shaped Radiographic Condylar Dx: o If non-displaced take full cannon with multiple views o If evidence of spiral take obliques around the limb o Always check for palmar condyle comminution via FDP/125o DPview Tx: Lag screw fixation & full limb cast/Kimzey splint, RTF ~3-4m Px: 40-70% RTR depending on degree of Fx & articular comminution, OA of fetlock

Answer 52

- Communications: 5 joints; o Tarsocrural (Tibiotarsal) & proximal intertarsal ALWAYS communicate o Proximal intertarsal and distal intertarsal RARELY communicate o Distal intertarsal and tarsal-metatarsal SOMETIMES communicate - Articulation: Tarsocrural has an articulation of 12-15 degrees dorsolateral to the sagittal plane - Capacity: Proximal, distal & tarsometatarsal are high load, low motion - Imaging: LM (lateromedial) with a 5o angle & DP 10o distal due to proximodistal sloping from lateral-medial

Answer 53

- Lateromedial (lateral) * Dorsoplantar (DP) * Oblique (Lateral and medial) * Flexed (lateral and dorsoplantar)

Answer 54

Radiographic Sx: OCD, Subchondral bone cysts (MC in stifle), Physeal dysplasia Host: 6m-3yrs Location: Frequently bilateral (Always radiograph pairs) Distal intermediate ridge of the tibia (DIRT) Incidence: Most common OCD Hosts: Common in SB, WB, TB CS: Effusion once commencing work, often bilateral, 50% are lame Dx: DMPLO Tx: Arthroscopic removal Px: Good (80%), early removal ↓ risk of persistent effusion Lateral trochlear ridge of the talus Incidence: 2nd Most common OCD Dx: DMPLO Tx: Arthroscopic removal Px: Fair (70%) depending on lesion size & location Medial malleolus of the tibia Dx: 15 degree DLPMO CS: Usually lucent instead of OC Fragment Tx: Arthroscopic Px: Fair Medial trochlear ridge of the talus CS: Lucency instead of Oc fragment Dx: DLPMO Px: Depends on size/location

Answer 55

Incidence: ‘Bone Spavin’ is the most common cause of hindlimb lameness in performance horses, lameness associated with the distal tarsus is reported in 70% of hindlimb lameness Host: Higher in straight hindlimb breeds & mature horses CS: - Lumbar/back muscle pain - Stiff exiting stall - Resent stopping/working - Bony swelling medial-distal joint - Intermittent, becomes better after spelling but ↑ again when at work - Back/Gluteal pain - Bilateral hind limb lameness - Plaiting gait Dx: - Flexion tests & Palpation of glute/lumbar +ve spavin tests - IA anaesthesia of TMT and DIT Joints - Radiography: Lesion locations: Distal intertarsal, tarsometatarsal Path: Osteophytes, SC bone lysis, narrowing or loss of joint space! Periosteal bone, sclerosis, ↓ corticomedullary demarcation Dis: ?? Some believe poor correlation between lameness and should rule out other causes Tx - IA Cortisone/HA injection +- pentosan (Bilateral) - Disruption of SC bone plate & Joint Fusion (Ideal Goal): a) Surgical Arthrodesis: 2-3 3.5mm holes across DIT & TMT joints OR diode laser ablation Post-op: Graded exercise 4-6wks post Px: 60-80% sound at 12m Dis: More expensive cf. chemical, requires GA b) Chemical arthrodesis: Na monoiodoacetate, 70% ethanol – NOT registered

Answer 56

- Collateral Ligament Injury Location: Collateral ligament of the tarsocrural joint CS: Initial 4/5 lameness → improves quickly to 2-3/5 lameness for a few months, diffuse medial swelling +- Joint effusion (Articular haemorrhage) Tx: Confine for 3m & Rx radiograph (Enthesophytes) Px: Good - Bog Spavin Location: Tarsocrural/tibiotarsal effusion – is the only hock joint that joint effusion effusion can be appreciated in Cause: Associated with osteochondrosis in young horses - Osseous Cyst-Like Lesions Locations: Distal tibia, talus, calcaneus, MT3 Dx: CT or nuclear scintigraphy Cause: Associated with DJD of the central tarsal & 3rd tarsal bone - Tibial Physitis Path: Enlargement of distal tibia, metaphysis is broad, asymmetric & has irregular sclerosis Tx: Resolves spontaneously, diet management Consequences: Angular Limb Deformity - Tarsal Slab Fx CS: Variable lameness, seen 7-10d post-injury +- bilateral Hosts: SB & TB Dx: Detection is difficult, requires several oblique views Location: Ventral & 3rd tarsal Tx: Lag screw, arthrodesis, conservative Px: 50% RTF - Malleolus Fx Location: Involve collateral ligament insertion Px: Good Tx: Small/Comminuted - Cut down arthrotomy/remove, Large – Lag screw Other Fx Locations: Talus, small tarsal bones, calcaneus - Osteomyelitis Cause: 2nd to wounds or haematogenous (Foals) Tx: Sx debridement, AMC - Calcaneal Osteomyelitis Cause: 2nd to trauma (Kicking out) CS: Usually wounded, 4-5/5 Lameness Dx: +- Absent on radiograph for several weeks Tx: Curettage, raised heel shoe - Collapsed Tarsal Bones Cause: Incomplete ossification Hosts: Neonates, older foals, young adults Normal Development: Ossification occurs in the last 60d gestation & 1stm of life CS: Often bilateral, bunny-hop gait, present with curb Dx: Radiograph - Bones appear wedge shaped and fragmented +- 2nd joint disease Tx: Arthrodesis – varied success, confinement & regular radiology Type 1: <30% dorsal compression (70% RTF) Type 2: >30% Dorsal compression (30% RTF) - Tarsal Luxations Location: TMT/PIT joints, tarsocrural, SDFT lateral luxation

Answer 57

- Water: 70% - Proteoglycans: 5% Dry - Elastin: 1-2% - Collagen: 80%, Type 1 – Most common & Tendon strength, Type 3 – In healing tendons & weaker - Non-Collagenous Matrix: Fibroblasts, structural proteins Effects of Age & Exercise on SDFT: - SDFT matures at 2yo → less elastic, ↓ tenocytes, changes in collagen & fibril size makes tendon more susceptible to injury - SDFT operates close to functional limit during high intensity → injury is frequent

Answer 58

- Mechanical overload due to change in tendon structure & function - Muscle fatigue, poor conformation, fitness, DDFT fatigue - Hyperthermia: 45 degrees causes collagen & protein damage via ↑ collagenase - Hypoxia/free radical production in exercise? CS: Sub-clinical injury proceeds overt clinical tendonitis – must monitor closely Pathogenesis: Rupture → haemorrhage/inflammation → Granulation tissue → collagen production → remodelling → reinjury

Answer 59

CS: - SDFT: Swelling on palmar Metacarpus, low grade lameness - DDFT: Swelling lateral-medial palmar MC, lamer cf. SDFT - SL: Similar to DDFT but only MC3 & check proximal sesamoids, lamer cf. SDFT - Other: Pain & Heat on palpation US Indication: Acute 48-72 hrs post injury, <2wks of injury, 2-3m During rehab; Useful: - Tendon cross- sectional area (CSA): Most sensitive indicator of damage - Fibre alignment score: At 4m to predict outcome, if <0.5 at 4m or improvement of >75% are ↑ likely to RTR - SDFT Cross-sectional area: Males > Females

Answer 60

Issues with Treating: - Permanent alteration in biochemical properties: Low/wrong cells, repair tissue (Cf. Regen) - Re-injury is Common: Due to altered functional characteristics & slow rate of healing - Little Evidence of Treatments: Many are advocated with little consistent effects Tx Aims of Tendonitis/Desmitis: - Acute: – Inflammatory: 0-7d aim to limit inflammatory disease - Repair/Proliferative: 2-30d, aim to limit further damage and influence fibroplasia - Remodelling: >30d, promote collagen maturation; monitor & controlled gradual exercise Tx: Therapy type 1. Physical a) Bandaging, ice & box rest for 1-2 weeks b) Rehabilitation NOT PROVEN: o Cold Therapy: No reduction in core SDFT but no detrimental tenocyte effect o Heel Elevation: Not beneficial, increases SDFT strainat trot; may predispose to injury o Elastoplast Taping: Reducing fetlock flexion during swing phase & peak force at trot o Support boots: Reduce fetlock extension by 1.50 at trot; unknow effect 2. Surgical a) Tendon Stab: Needle through core lesion to evacuate intra-tendinous blood clot to allow in-growth of new vessels & improve fibril orientation b) Superior Check Ligament Desmotomy: Aim to length SDFT length; 1.3x more likely to RTR but increased risk of re-injury & 6-fold risk of SL injury c) Palmar/plantar annular transection for low SDFT lesions 3. Anti-Inflammatory: PBZ (Early) ONLY NOT USED: o Methylprednisolone (Cortisone) – IT causes collagen necrosis o DSMO – weakens healing tendons 4. Intra-tendinous Method: Done under high 2 point Nerve block → aseptic prep w/ US guided injection a) Stem Cells: MOA: Stem cells or progenitor differentiate into specific fibroblasts → matrix Duration: Last for 2wks Bone marrow Stem cells: From sternum or tuber coxae for 4wks, 80% RTR Adipose SC: Harvest from fat pad near tail & injected into tendon b) Platelet Rich Plasma (PRP): Contains growth factors → ↑ neovascularisation, quality repair, 100% RTF 10-13m c) IGF-1 d) A-Cell Vet e) Bone marrow: Straight: From sternum (25% cells) or tuber coxae (100%), source of MSC or growth factors Supernatant: High Growth factor’s to increase fibroblast protein & COMP synthesis

Answer 61

Local Anaesthesia of SL Origin/Proximal MC3: - Forelimb: High 2 point: Deep branch of the lateral palmar n. & medial palmar n. - Hindlimb: Deep branch of lateral plantar n. → ↓ risk of desensitising TMTJ & tarsal sheath Acute/Sub-Acute Over-Straining Location: Forelimb/hindlimb/branches often distal medial branches in the forelimb or mid-body CS: Swelling & pain on palpation Px: 40% racehorses RTR without re-injury Tx: Rest & controlled rehab +- Intralesional injection w/ stem cells or PRP Px: Usually recurs & progresses Chronic Progressive Degeneration Location: Forelimb & hindlimb Ddx: Primary Ddx in hindlimb lameness w/ OA (osteoarthritis) CS: Bilateral insidious lameness Local: Blocks to Proximal suspensory NB Dx: US - ↑ CSA (60% of site) & poor fibre pattern Tx: Shock wave therapy (Temporary 20-40% RTF), Sx fasciotomy & neurectomy of plantar n. (90%)

Answer 62

- Egg-Bar Shoe: Role: ↑ contact surface area of hoof Adv: Spreads force evenly on hoof, provides caudal shift of pressure, small ↓ of NB pressure Dis: Extends beyond heels which increases heel pressure - Raised Heel Role: Reduces DDFT strain by 27% & ↓ torque on DIPJ Adv: Max force on NB was ↓ by 24% Dis: Prolonged use PF to crushed heels - Natural Balance Role: Heel lands first to select optimal breakover point corrects phalangeal alignment Adv: Reduces strain on DDFT Dis: Doesn’t ↓ NV pressure or peak DIPJ movement - Rolled Toe Role: Lowers peak hoof loading during breakover to smooth it out Dis: Some found no effect on DIPJ force or NB load - Heart Bar Shoe Role: ↓ Heel expansion & provide frog + digital cushion support Adv: Prevents palmar P3 displacement due to ↑ frog pressure/↓ wall wt. bearing

Equine Lameness Flashcards

Brad (86 cards)