Single-incision drilling technique to achieve hemiepiphysiodesis of the distal metacarpus - complications and outcome in 207 foals with metacarpophalangeal varus deformities.

Objective: To report the outcome of foals treated for metacarpophalangeal varus deformity with a single-incision drilling technique for hemiepiphysiodesis of the distal lateral metacarpal physis.

Study Design: Retrospective case-control cohort study.

Animals: Thoroughbred foals (n = 207), 171 age- and sex-matched maternal siblings.

Methods: Medical records (2017-2020) were reviewed for signalment, limb(s) treated, location of the surgery, and any reported complications. Follow-up radiographs obtained for the yearling sale were assessed for abnormalities. Horses were matched to maternal siblings using an online database. Sales and racing performance data were compared between cohorts.

Results: The average age at the time of surgery was 97 days. The treated limb was the left front in 52, right front in 31, both fronts in 119, unknown in 5. Three horses developed calcinosis circumscripta lesions adjacent to the physis, which were removed successfully. No radiographic abnormalities associated with the surgery site were detected on yearling prepurchase radiographs. There were no differences in sales and racing performance data between treated horses and maternal controls.

Conclusion: Hemiepiphysiodesis is a safe and effective treatment for metacarpophalangeal varus deformities in foals. No negative effect on sales or racing performance was identified.

Clinical Significance: This technique avoids risks, costs, and the need for second surgery associated with an orthopedic implant. The surgeon should be aware of the potential for development of a calcinosis circumscripta lesion with this technique.