Os carpi intermedium (Ci)
The intermediate carpal bone is the second bone of the proximal carpal row (from medial to lateral: radial, intermediate, ulnar, plus the accessory carpal bone). It articulates proximally with the middle facet of the distal radius, medially with the radial carpal bone, laterally with the ulnar carpal bone, and distally with the third (and often fourth) carpal bone. It is somewhat wedge-shaped, wider dorsally than palmarly, and helps distribute load across the carpus. Chip fractures of the intermediate carpal bone (especially its proximal dorsal margin, in the antebrachiocarpal joint) are common in racehorses, along with chips of the radial and third carpal bones. Most are treated by arthroscopic removal. Slab fractures are less common but more serious.
Carpal chip fractures produce joint effusion and variable lameness. Diagnosis uses multiple radiographic views (including flexed and skyline) and arthroscopy. Prognosis after arthroscopic chip removal is generally good when cartilage damage is limited.
## Overview Chip fractures are small osteochondral fragments that separate from the margin of a joint, most commonly the carpus or fetlock in racehorses. They result from acute overload or from propa
## Overview Slab fractures extend from one articular surface completely through the bone to another articular surface. In the carpus they are most often frontal slabs of the third carpal bone in race
## Overview Osteoarthritis of the middle carpal joint is a frequent cause of knee lameness in performance horses, especially racehorses. Previous chip fractures or chronic synovitis predispose to it.
Sudden forelimb lameness with knee swelling or heat after racing or hard work needs veterinary evaluation and radiographs. Early arthroscopic treatment of chips improves long-term joint health.
## Overview Chip fractures are small osteochondral fragments that separate from the margin of a joint, most commonly the carpus or fetlock in racehorses. They result from acute overload or from propagation of stress-related microdamage. Fragments cause synovitis and, if left in place, progressive cartilage damage. ## Causes High-speed loading, hyperextension, and fatigue failure of subchondral bone. ## Diagnosis Joint effusion, lameness, and radiographic demonstration of the fragment. Arthroscopy assesses associated cartilage injury. ## Treatment Arthroscopic removal is the standard of care for clinically significant chips. ## Recovery and Prognosis Many horses return to athletic use. Extensive cartilage damage lowers the prognosis. ## Prevention Gradual conditioning and attention to racing surfaces may reduce incidence. Signs include: joint effusion; lameness after exercise; pain on flexion; radiographic fragment
## Overview Slab fractures extend from one articular surface completely through the bone to another articular surface. In the carpus they are most often frontal slabs of the third carpal bone in racehorses. They cause acute lameness and joint effusion and require surgical repair. ## Causes High-energy loading. ## Diagnosis Radiographs. ## Treatment Lag-screw fixation. ## Recovery and Prognosis Fair to good with accurate reduction. ## Prevention Monitoring of racehorses. Signs include: acute lameness; joint effusion; radiographic slab extending through the bone
## Overview Osteoarthritis of the middle carpal joint is a frequent cause of knee lameness in performance horses, especially racehorses. Previous chip fractures or chronic synovitis predispose to it. Signs include effusion, reduced flexion, and lameness after work. Radiographs confirm degenerative change. ## Causes Repetitive high-speed loading, prior osteochondral fragmentation, or chronic inflammation. ## Diagnosis Flexion tests, diagnostic analgesia, and radiographs. ## Treatment Intra-articular therapies, anti-inflammatories, and modified training. Arthroscopy if concurrent fragments are present. ## Recovery and Prognosis Fair to good for comfort with management. Advanced disease limits high-speed work. ## Prevention Early removal of clinically significant chips and sensible training schedules. Signs include: middle-carpal effusion; lameness after fast work; positive carpal flexion; radiographic osteoarthritis
Carpal chip fractures produce joint effusion and variable lameness. Diagnosis uses multiple radiographic views (including flexed and skyline) and arthroscopy. Prognosis after arthroscopic chip removal is generally good when cartilage damage is limited.
Sudden forelimb lameness with knee swelling or heat after racing or hard work needs veterinary evaluation and radiographs. Early arthroscopic treatment of chips improves long-term joint health.
See the Intermediate Carpal Bone (Left) on our interactive 3D horse model. Open 3D Model