Management of the unstable prosthetic shoulder arthroplasty

Instability is the most common complication of shoulder arthroplasty. An understanding of the predisposing factors for developing instability is critical to the avoidance of this complication. Soft-tissue balance and proper component positioning must be attained during the index procedure to minimize the risk of developing postoperative instability. Once the shoulder does become unstable, the reason for the instability must be determined. Is the instability secondary to soft-tissue imbalance, component malposition, bony deformity, or a combination of these? Next, a decision must be made as to how to treat the instability. Nonsurgical treatment may be tried if no obvious cause is present. However, if the instability fails to resolve or recurs, surgical intervention should be undertaken early. If the instability is not treated, it may result in loosening of the prosthesis and early wear of the components. Once surgical intervention is undertaken, all elements of the instability must be recognized and treated.