Intralesional injection of insulin-like growth factor-I for treatment of superficial digital flexor tendonitis in Thoroughbred racehorses: 40 cases (2000-2004).

OBJECTIVE-To evaluate outcome after intralesional injection of insulin-like growth factor-I (IGF-I) for treatment of superficial digital flexor (SDF) tendonitis in Thoroughbred racehorses. DESIGN-Retrospective case series. ANIMALS-40 Thoroughbred racehorses. PROCEDURES-Medical records of racehorses with SDF tendonitis treated within 13 weeks after injury by intralesional injection of IGF-I (25 or 50 μg every other day for 4 or 5 treatments) were reviewed. Outcome was determined via analysis of race records, owner follow-up, and examination. RESULTS-Mean age of the horses was 3.1 years (range, 2 to 7 years), and time from injury to treatment ranged from 8 to 90 days. Mean ± SD approximate lesion length on admission was 15.6 ± 6.0 cm, and mean percentage cross-sectional area of the tendon affected was 26 ± 18%. Twenty-six of the 40 horses underwent desmotomy of the accessory ligament of the SDF tendon. Echolucency was reduced in 23 of 26 horses by the end of the treatment period. Twenty-one of 34 (62%) horses for which race data were available raced at least once after treatment, including 10 (30%) horses that raced between 1 and 4 times and 11 horses (32%) that raced ≥ 5 times. Thirteen of 28 (46%) horses had a recurrence of tendonitis or developed tendonitis elsewhere. CONCLUSIONS AND CLINICAL RELEVANCE-Results suggested that in Thoroughbred racehorses with SDF tendonitis, intralesional injection of IGF-I led to a decrease in ultrasonographic lesion severity, but treated horses had only a moderate prognosis for return to racing.