## Overview Condylar fractures of the third metacarpal or metatarsal bone (cannon bone) are sagittal-plane fractures of the distal condyle, most often the lateral condyle in Thoroughbred racehorses. They result from fatigue failure of subchondral bone under repetitive high-speed loading. Acute lameness and fetlock effusion after exercise are classic. ## Causes Repetitive loading during race training produces microdamage that coalesces into a propagating fracture. Lateral condylar fractures predominate in the forelimb; medial fractures are more likely to spiral proximally. ## Diagnosis Acute lameness after work, marked fetlock effusion, and pain on flexion are typical. Radiographs (including flexed views) confirm the fracture. Standing computed tomography is more sensitive for early stress changes. ## Treatment Lag-screw fixation is the treatment of choice for most lateral condylar fractures. Medial fractures can spiral; fixation may use lag screws or a plate, depending on the fracture. Conservative casting is occasionally used for very short, incomplete fractures. ## Recovery and Prognosis Many horses return to racing after uncomplicated lateral condylar repair, although osteoarthritis can limit performance. Spiral medial fractures and those with significant joint damage have a more guarded outlook. ## Prevention Screening with advanced imaging in high-risk racehorses and careful training management may reduce catastrophic propagation, although evidence is still developing.
acute lameness after exercise; marked fetlock joint effusion; pain on fetlock flexion; swelling of the distal cannon
## Overview Condylar fractures of the third metacarpal or metatarsal bone (cannon bone) are sagittal-plane fractures of the distal condyle, most often the lateral condyle in Thoroughbred racehorses. They result from fatigue failure of subchondral bone under repetitive high-speed loading. Acute lameness and fetlock effusion after exercise are classic. ## Causes Repetitive loading during race training produces microdamage that coalesces into a propagating fracture. Lateral condylar fractures predominate in the forelimb; medial fractures are more likely to spiral proximally. ## Diagnosis Acute lameness after work, marked fetlock effusion, and pain on flexion are typical. Radiographs (including flexed views) confirm the fracture. Standing computed tomography is more sensitive for early stress changes. ## Treatment Lag-screw fixation is the treatment of choice for most lateral condylar fractures. Medial fractures can spiral; fixation may use lag screws or a plate, depending on the fracture. Conservative casting is occasionally used for very short, incomplete fractures. ## Recovery and Prognosis Many horses return to racing after uncomplicated lateral condylar repair, although osteoarthritis can limit performance. Spiral medial fractures and those with significant joint damage have a more guarded outlook. ## Prevention Screening with advanced imaging in high-risk racehorses and careful training management may reduce catastrophic propagation, although evidence is still developing.
acute lameness after exercise; marked fetlock joint effusion; pain on fetlock flexion; swelling of the distal cannon