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Fragments of the extensor process of the distal phalanx occur infrequently. Their underlying cause is speculative. Fragments can be large or small, with variable levels of coffin joint involvement and clinical lameness.
Arthroscopic removal of small fragments involving the coffin joint is the preferred treatment, but dealing with large fragments is more problematic. In a study just published, researchers at Colorado State University evaluated the outcome of 14 horses that had undergone arthrotomy (surgical incision of the joint) to remove such large fragments from the coffin joint.
Most of the horses were under 5 years old, had chronic lameness and had fragments involving 20 to 45 percent of the joint surface of the distal phalanx. Fragments were removed through a vertical incision made directly over (and through) the common digital extensor tendon, just proximal to the coronary band. A successful outcome (sound and able to be used at a level of performance equal or exceeding that prior to surgery) was achieved in 8 of the 14 horses.
The authors say outcome could be improved by performing surgery on horses with lameness of less than 2 years’ duration and by careful post-operative management. They concluded that a fair prognosis could be anticipated with the procedure.
—Dechant JE, Trotter GW, Stashak TS, Hendrickson DA. Removal Of Large Fragments Of The Extensor Process Of The Distal Phalanx Via Arthrotomy In Horses: 14 Cases (1992-1998). Journal of the American Veterinary Medical Association 2000; 217: 1351-1355.