Reverse shoulder arthroplasty

Abstract

Reverse polarity total shoulder arthroplasty is an innovation primarily designed to treat the rotator cuff-deficient shoulder by increasing constraint and thereby addressing the challenges of pseudoparalysis. Forward elevation can be regained, pain and quality of life can be improved. Recently, there has been an expansion in both the breadth of indications and the volume of surgeries performed. We aim to review current practice and direction of travel. The impact of rotator cuff tear arthropathy (CTA) is often significant and disabling. This condition is associated with painful arthrosis of the shoulder in conjunction with instability, which allows the humeral head to escape antero-superiorly. The resulting loss of function in the shoulder is aptly described as ‘pseudoparalysis’. Figure 1 shows the normal deltoid function around a shoulder with an intact soft-tissue envelope, and the superior migration that results when the superiorly directed force vector is not neutralised. Conventional anatomical arthroplasty of the shoulder fails to restore function in these patients due to the inadequate stability of the joint around a central point of pivot, combined with an inability of the surrounding muscles to compensate for a weak or torn rotator cuff. Fig. 1 Proximal migration in cuff tear arthropathy with resulting deltoid dysfunction- schematic This combination results in a complex and disabling condition that has vexed shoulder surgeons since the early days of development in shoulder arthroplasty systems. A better understanding of shoulder biomechanics and the mechanisms of failure in total shoulder arthroplasty led to the development of reverse shoulder arthroplasty (RSA) designs. While the original indication was CTA, there has been a rapid expansion of indications to include a spectrum of pathologies: proximal humeral fractures and trauma sequelae; massive cuff tears; tumours; primary glenohumeral osteoarthritis (OA); and the revision of failed shoulder arthroplasties. Themistocles Gluck most likely developed a shoulder arthroplasty in the …