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Anatomical Overview & Clinical Localization:
Anatomical Overview & Clinical Localization:
- Three Primary Articulations: Includes the radiocarpal (antebrachiocarpal), intercarpal (middle carpal), and carpometacarpal joints.
- Joint Communication: The carpometacarpal joint communicates with the middle carpal joint; therefore, injecting the latter provides analgesia for both.
- Indicators of Problems: Issues are localized to this region through lameness, swelling, synovial effusion, pain on flexion, and diagnostic analgesia.
- Swelling Identification: Palpation and visualization are used to determine if fluid is in the joint, the tendon sheath, or the subcutaneous space.
Diagnostic Methodologies:
Diagnostic Methodologies:
- Diagnostic Analgesia: Usually administered intra-articularly; clinicians must note that analgesia can diffuse into the proximal suspensory ligament over time, potentially causing diagnostic confusion.
- Radiography: Critical for specific diagnoses; standard views should include flexed lateral and skyline views of the carpal bones.
- Advanced Visualization: Arthroscopic examination is used to diagnose internal damage like ligament tears or to guide surgical repairs.
Carpal Fractures:
Carpal Fractures:
- Osteochondral (Chip) Fractures:
- Etiology: Common in racehorses, primarily caused by trauma during fast exercise.
- Location: Typically occur on the dorsal aspect of the joint.
- Treatment: Arthroscopic fragment removal is the treatment of choice.
- Slab Fractures:
- Definition: Fractures extending from one articular surface to another.
- Common Site: Frontal slab fracture of the radial facet of the third carpal bone.
- Treatment: Lag screw fixation with arthroscopic guidance (for fractures > 10 mm) or fragment removal.
- Accessory Carpal Bone Fractures:
- Signs: Acute and severe lameness with possible carpal sheath effusion.
- Treatment: Typically managed conservatively, though articular fragmented pieces may be surgically removed.
Osteoarthritis (OA) of the Carpus:
Osteoarthritis (OA) of the Carpus:
- Radiocarpal/Middle Carpal OA: Characterized by chronic joint capsule thickening and decreased range of motion; common in retired Thoroughbred broodmares.
- Carpometacarpal Joint OA:
- Affected Breeds: Spontaneous occurrence mainly in Arabians and Quarter Horses.
- Signs: Firm swelling over the medial aspect of the distal carpus and minimal initial lameness.
- Radiographic Features: Periarticular new bone proliferation over the proximal second or third metacarpal bones.
- General Management: Chondroprotectants, NSAIDs, exercise modification, and intra-articular medication.
Soft Tissue and Developmental Disorders:
Soft Tissue and Developmental Disorders:
- Carpal Hygroma:
- Definition: A subcutaneous, usually aseptic swelling over the dorsal carpus resulting from trauma.
- Nature: Generally a cosmetic blemish that does not cause lameness.
- Treatment: Early stages involve drainage, steroid injections, and bandaging; infected tissue requires surgical resection.
- Intercarpal Ligament Injuries: Most commonly involve the medial palmar intercarpal ligament; identified by synovitis unresponsive to standard therapy.
- Subchondral Bone Damage: Often precedes slab fractures in racehorses; diagnosed via skyline-view radiographs showing lysis and sclerosis.
- Exostoses and Osteochondromas: Arise on the caudal distal radius metaphysis; can cause carpal sheath tenosynovitis and are treated via tenoscopy.
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