Long-term athletic performance in sport horses after desmotomy of the accessory ligament of the deep digital flexor tendon.

Abstract

Outcome after desmotomy of the accessory ligament of the deep digital flexor tendon (AL-DDFT) to treat flexural deformity of the distal interphalangeal joint has been reported to be excellent. However, no studies have compared long-term athletic performance of sport horses exposed to desmotomy of the AL-DDFT to that of matched controls. The objective of this study is to compare long-term athletic performance in sports horses subjected to desmotomy of the AL-DDFT with the performance of matched controls. This is an observational multicentre retrospective matched cohort study. Records from horses undergoing desmotomy of the AL-DDFT between 2004 and 2015 were reviewed. Various databases were used to identify age-matched siblings as unexposed controls and data on the horses' athletic careers. Seventy-four exposed and 194 matched unexposed horses were included. Although not significantly different, the proportion of exposed horses entering competition (28%, 95% CI 16%-38%) had a substantial risk difference compared with the proportion of unexposed horses entering competition (38%, 95% CI 26%-44%) (P=.2). Career longevity was significantly better for unexposed (15.6 competitions [95% CI 10.7-22.5] over a median of 570days [IQR 210-1340]) than for exposed horses (9.7 competitions [95% CI 6.4-14.6] over a median of 219days [IQR 2-1159] for horses operated in one limb and 6.1 competitions [95% CI 3.6-9.9] over a median of 446days [IQR 23-603days] for horses operated in two limbs, P<.001). Age at surgery and whether the condition was unilateral or bilateral did not affect chance of competing. Small sample size, varying quality of medical records, stage of contraction not noted in many records and missing information on reasons for not entering into competition. Desmotomy of the AL-DDFT is associated with decreased long-term athletic performance in sport horses compared with matched unexposed horses.