Risk factors for and outcomes of noncatastrophic suspensory apparatus injury in Thoroughbred racehorses

Objective-To evaluate effects of toe grabs, exercise intensity, and distanc e traveled as risk factors for subclinical to mild suspensory apparatus inj ury (SMSAI) in Thoroughbred racehorses and to compare incidence of severe m usculoskeletal injury (MSI) in horses with and without SMSAI. Design-Nested case-control study. Animals-219 Thoroughbred racehorses racing or in race training. Procedure-Racehorses were examined weekly for 90 days to determine incidenc e of suspensory ligament injury and monitor horseshoe characteristics. Ever y horse's exercise speeds and distances were recorded daily. Conditional lo gistic regression was used to compare exposure variables between incident c ase (n = 25) and selected control (125) horses. Survival analysis was used to compare time to MSI for horses with (n = 41) and without (76) SMSAI. Results-The best-fitting logistic model for the data included age (< 5 vs < greater than or equal to> 5 yea rs old), toe grab height the week of injury (none vs very low, low, regular, or Quarter Horse height), and weekly dist ance the week preceding injury (miles). Although the 95% confidence interva ls for all odds ratios included 1, the odds for SMSAI appeared to increase with the presence of a toe grab, higher weekly distance, and age greater th an or equal to 5 years. Horses that had SMSAI were significantly more likel y to have a severe MSI or severe suspensory apparatus injury than were hors es that did not. Conclusions and Clinical Relevance-Results suggest that pre-existing SMSAI is associated with development of severe MSI and severe suspensory apparatu s injury. Modifying training intensity and toe grab height for horses with SMSAI may decrease the incidence of severe MSI.