GRACILIS OR SEMITENDINOSUS MYOPATHY IN 18 DOGS

The clinical findings in 18 dogs with gracilis (n=17) or semitendinosu s (n=1) myopathy are described. Each dog had a similar hind-limb gait abnormality characterized by a shortened stride with a rapid, elastic medial rotation of the pa external rotation of the hock, and internal rotation of the stifle during the mid-to-late swing phase of the strid e. Medical management prior to or in lieu of surgery was attempted (n= 8) with no apparent response. Fifteen dogs had one or multiple surgica l procedures. Although transection, partial excision, or complete rese ction of the affected muscle resulted in resolution of lameness follow ing surgery, lameness recurred six weeks to five months (mean, 2.5 mon ths; median, two months) following surgery. Adjunctive medical treatme nt did not prevent recurrence. Variable replacement of the affected mu scle with fibrous connective tissue (predominantly along the caudolate ral border of the muscle) was evident grossly and replacement of myofi bers with fibrous connective tissue was confirmed histologically. A de finitive etiology could not be established.