The clinical syndrome known as sweeny is characterized by instability of the shoulder joint and atrophy of the supraspinatus and infraspinatus muscles. The condition is reported to be the result of traumainduced SSN dysfunction.1 The development of atrophy of the supraspinatus and infraspinatus muscles as a consequence of denervation supports this concept. It has been reported2 that experimental transection of the SSN in an adult horse caused atrophy of the supraspinatus musculature but no gait abnormality. This implicates brachial plexus dysfunction as a cause of gait abnormality.2 Surgical management of sweeny involves decompression of the SSN by scapular notch resection with or without suprascapular ligament transection and neurolysis.3,4 Results of previous studies3,4 indicate favorable responses to both conservative5 and surgical treatments.
To our knowledge, no scientific study has been performed to define the clinical effects of transitory SSN anesthesia in horses. The purpose of the study reported here was to assess gait abnormalities associated with selective anesthesia of the SSN achieved via perineural catheterization and thereby determine the function of that nerve as it relates to gait in horses. We hypothesized that selective anesthesia of the SSN would result in clinically apparent shoulder joint instability.
Central venous catheterization set, Arrow International Inc, Reading, Pa.
PROC FREQ in SAS, version 8.2, SAS Institute Inc, Cary, NC.
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Schneider JE, Adams OR & Easley KJ, et al. Scapular notch resection for suprascapular nerve decompression in 12 horses. J Am Vet Med Assoc 1985;187:1019–1020.
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