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Subchondral cystic lesions of the medial femoral condyle in 37 Thoroughbred racehorses: A retrospective study (1995-2002)

Justin S. Harper BS, College of Veterinary Medicine, Texas A&M University,Suite 101 - VMA
College Station, TX 77843-4461

Jonathan M. Lumsden, BVSc, MS, DipCVS, Dip ACVS, Randwick Equine Centre, 3 Jane Street, Randwick NSW 2031, Sydney Australia

Objective: To provide an analysis of the surgical outcome of 37 Thoroughbred racehorses diagnosed and treated with surgical arthroscopy for subchondral cystic lesion (SCL) of the medial femoral condyle (MFC).

Design: Retrospective case series.

Animals or Sample Population: 37 Thoroughbreds (1995-2002) diagnosed with SCL of the MFC.

Procedure: Data gathered from patient records included signalment, history, physical exam, clinical, radiographic, scintigraphic and surgical findings. Post-surgical outcomes were obtained from patient record, follow-up exams, trainer/owner interviews, and analysis of racing records.

Results: Fifty-one SCL of the MFC were radiographically identified in 37 Thoroughbred racehorses. 19 (51%) horses revealed right-sided lesions and 4 (11%) horses were identified with left-sided lesions, while 14 (38%) horses were affected bilaterally. None of the 37 horses diagnosed with SCL of the MFC had started a race prior to diagnosis and surgical correction. The lesion was most commonly identified in 2-year olds (57%). There was a male to female ratio of 1.3:1. Of the 51 SCL of the MFC radiographically identified, 44 (86%) were arthroscopically evaluated and 41 (93%) were surgically curretted. Currently 43% of horses have raced.

Clinical Relevance: SCL of the MFC were commonly seen in unraced 2-year old Thoroughbred, with the lesion occurring more commonly in the right hindlimb. There was no predilection among sex. Flattening of the distal medial femoral condyle on the caudo-to-cranial view was further delineated as a shallow cyst through the use of a flexed lateral view. Treatment arthroscopically with surgical curettage and at least 9 months of rest yields a fair prognosis for return to racing.