Computed tomographic guidance for internal fixation of type II distal phalangeal fractures in 51 horses

Type II distal phalanx (P3) fractures are a well-described cause of lameness in horses. Reports on outcome following internal fixation of type II P3 fractures are lacking, and with little emphasis on complications.

To describe a technique for internal fixation of type II P3 fractures, and evaluate whether specific variables influenced post-operative complications or a horse's ability to return to work.

Retrospective case series.

Medical records of 51 horses with CT-guided internal fixation of type II P3 fractures were reviewed. Outcome data were acquired from race records and telephone interviews. Associations between independent variables and outcome were analysed using multivariable logistic regression.

Eighty-six per cent (95% CI 74%-94%; n = 44) successfully returned to work. Implant infection (n = 15) and distal interphalangeal joint osteoarthritis (n = 9) were the most common complications, with the latter reducing the likelihood of success (OR = 0.09, 95% CI 0.01-0.7, P = .02). Implant infection increased the time to return to work (HR = 0.5, 95% CI 0.2-0.9, P = .03). The odds of delayed infection decreased by filling the hoof defect with acrylic hoof adhesive rather than poly(methyl methacrylate) and deeply countersinking the screw head (OR = 0.08, 95% CI 0.02-0.38, P = .001); the individual effect of each treatment is unknown. Radiographic healing was not associated with likelihood of success.

Study limitations included variation in follow-up methods, lack of control population for comparison and lack of randomisation of treatment protocols.

Internal fixation of type II P3 fractures is an effective treatment that allows horses to return to athletic use, with similar improved success rates as those reported for conservative management. Infection rates were reduced by deeply countersinking the screw head and filling the hoof defect with an acrylic that mimics hoof wall flexibility and provides a secure seal. Recommencement of training should be based on clinical rather than strictly radiographic findings.