Overstrain of the superficial digital flexor tendon (SDFT) is a common Thoroughbred racehorse limb injury requiring treatment. Using clinical treatment records with race records, the aim of this retrospective cohort study was to determine whether treatment of SDFT lesions in flat Thoroughbred racehorses with autologous bone marrow-derived mesenchymal stem cells (BM-MSCs) or allogenic adipose-derived mesenchymal stem cells (A-MSCs) is associated with improved likelihood of returning to racing, when compared to racehorses managed with a controlled exercise rehabilitation program alone.
A total of 213 Thoroughbred racehorses with superficial digital flexor tendon injuries were identified. All were prescribed the same 12-month controlled exercise rehabilitation program. Sixty-six also received intralesional BM-MSC, and 17 received A-MSC treatment. Follow-up was a minimum of 2 years after return to full race training. Multivariable logistic regression models were used to investigate associations between the treatments and the likelihood of returning to racing and completing five or more (C5+) races post-injury.
Compared to controlled exercise rehabilitation program alone, BM-MSC treatment was associated with increased odds of returning to racing (OR 3.19; 95% CI 1.55–6.81) and C5+ races post-injury (OR 2.64; 95% CI 1.32–5.33). Older age and increasing lesion length were associated with a reduced likelihood of returning to racing. Male sex and increased number of pre-injury starts were associated with increased odds of returning to racing. There was no observed increased likelihood of return to racing or C5+ races associated with treatment with A-MSCs compared to controlled exercise rehabilitation program alone.
Intralesional BM-MSC treatment was associated with an increased likelihood of returning to racing and C5+ races post-injury compared to controlled exercise rehabilitation program alone. Intralesional A-MSC showed no significant benefit.