Infraspinatus Muscle-splitting Incision in Posterior Shoulder Surgery

Abstract

Standard posterior shoulder surgical approaches include infraspinatus tendon detachment and infraspinatus-teres minor interval development. Cadav eric and clinical investigation of a new infraspinatus- splitting approach to the posterior glenohumeral joint was undertaken to assess efficacy in providing expo sure, preserving tendon attachment, and avoiding neu rologic compromise. Infraspinatus musculotendinous and neural anatomy was examined in 20 cadavers. Four patients with posterior shoulder instability underwent posterior capsulorrhaphy through this infraspinatus- splitting approach, followed by electrodiagnostic test ing. Infraspinatus muscle was bipennate in all speci mens, the tendinous interval an average 14 mm inferior to the scapular spine at the glenoid rim. The infraspinatus-splitting interval bisected the posterior glenoid rim at its midpoint, whereas the infraspinatus- teres minor interval crossed the glenoid rim's lower quarter. The suprascapular nerve provided sole inner vation to the infraspinatus muscle in all specimens, en tering the infraspinous fossa at the notch as a single trunk 22 mm medial to the glenoid rim. Minimum branch ing variability was observed. Electrodiagnostic testing showed no evidence of axonal damage or muscle de nervation in either infraspinatus pennate bundle. Lim iting infraspinatus-splitting dissection medially to 1.5 cm from the posterior glenoid rim prevents damage to any interval-crossing suprascapular nerve branches. Pos terior shoulder surgery through a horizontal, longitudi nal infraspinatus tendon-splitting approach provides ex cellent exposure of posterior capsule, labrum, and glenoid, without requiring tendon detachment or caus ing neurologic compromise.