Shoulder (question 19): a free FRCS (Tr & Orth) Section 1 question

This is a functional cuff tear, explained by Burkhart's suspension-bridge model. The rotator cable is a thick band of fibres, an extension of the coracohumeral ligament, running perpendicular to the tendon fibres from the anterior supraspinatus insertion to the inferior infraspinatus. It stress-shields the thin, relatively avascular crescent lateral to it. A tear confined to the crescent leaves the cable attachments intact, so cuff force still reaches the tuberosity through the cable, as load passes through the cable of a suspension bridge. Deltoid alone produces superior shear without a centred head. Biceps is at most a weak depressor, a fulcrum on the arch is the mechanism of cuff tear arthropathy, and teres minor does not abduct. Reference: Burkhart SS et al., Arthroscopy 1993; Miller's Review of Orthopaedics 8e.