Timothy R. O'Brien

DISTAL PHALANX FRACTURES IN HORSES

The case records of 274 horses with fractures of the distal phalanx were reviewed. Fifty-two horses had bilateral forelimb fractures, for a total of 326 distal phalanx fractures. The fractures were classified into one of five previously described types, based on the radiographic anatomic configuration of the fracture. Solar margin fractures, which have been briefly described in other reports and previously classified as type V fractures, were identified in 132 horses. This type of fracture is distinct from other distal phalanx fractures. Due to the high incidence of solar margin fractures, these fractures were classified as a separate type (type VI). Follow-up radiographic examinations to assess fracture healing were available for 36 horses. Twenty-two horses with distal phalanx fractures (three type I, nine type II, two type III, one type IV, one type V, and six type VI) had radiographic evidence of complete bony union of the fracture at a mean of 11 months after injury. Eight horses with complete type II fractures involving the articular surface had bony union of the body and solar margin, but not the subchondral bone at the articular surface, a mean of 11 months after injury. Six horses (four type II and two type IV) had little radiographic evidence of bony healing during the follow-up period. All fractures that eventually healed had evidence of progression toward bony union by 6 months after injury.

PUNCTURE WOUNDS INTO THE NAVICULAR BURSA OF THE HORSE

Radiography was used to evaluate 32 horses presented for puncture wounds into the navicular bursa. At the initial radiographic examination, 21 horses had no radiographic signs of osteomyelitis, while 11 did. The mean-time interval between injury and radiographic examination was 20.6 days for horses without evidence of osteomyelitis and 59.3 days for those with evidence of osteomyelitis. Radiographic signs of osteomyelitis of the navicular bone included flexor cortical destruction and irregularity of the flexor surface. Other abnormalities included pathologic fracture of the navicular bone, subluxation of the distal interphalangeal joint, or secondary joint disease. The lateromedial and palmaroproximal-palmarodistal oblique projections were most useful for identifying abnormalities of the navicular bone. There was a high correlation between horses that had positive presurgical radiographic signs and surgical findings. However, approximately 50% of horses that had negative radiographic findings initially had positive surgical findings. Ten of 21 horses with negative radiographic findings on initial examination had evidence of bony lesions when reevaluated from 3 weeks to 6 years later. Nine of 11 horses with radiographic signs of osteomyelitis on initial radiographic examination were euthanatized or had an unsatisfactory outcome. Seven of 10 horses with radiographic signs on reexamination were euthanatized. Thirteen of 20 horses with positive surgical findings for navicular bone infection were euthanatized or had an unsatisfactory outcome.