Gait Abnormalities Caused by Selective Anesthesia of the Suprascapular Nerve in Horses

Abstract

It is generally accepted that sweeny, (atrophy of the supraspinatus and infraspinatus muscles with an attendant gait abnormality), is due to traumatically induced dysfunction of the suprascapular nerve (SSN). However to this date, no scientific study has been performed to define the clinical effects of transitory SSN anesthesia. This thesis describes the methodology and clinical effects of specific SSN chemical denervation in three adult horses. Chemical denervation of the SSN was achieved using 1 ml of 2% mepivacaine hydrochloride delivered via perineural catheterization. Statistically significant scapulohumeral instability as evidenced by consistent lateral excursion at the walk during the weight-bearing stride phase occurred in three subjects. These data support the role of the SSN in provision of shoulder stability and define the role of the SSN in the etiopathogenesis of the clinical syndrome referred to as sweeny.