Indications and contraindications

Glenoid Erosion

Glenoid erosion after hemiarthroplasty is a multifactorial problem. It may occur early or late and does not seem to be related to any readily identifiable risk factor. This problem occurs when the metallic prosthetic humeral head erodes into the softer glenoid bone ( Fig. 35.1 ). Initially, pain may be the sole manifestation of this problem. As the erosion progresses medially, the normal length-tension relationships of the rotator cuff may become compromised and result in substantial weakness ( Fig. 35.2 ).

Glenoid erosion may be central or peripheral. If the rotator cuff is intact, as in primary osteoarthritis, the erosion is usually central or, less commonly, posterior ( Fig. 35.3 ). If the rotator cuff is deficient, the erosion is generally superior ( Fig. 35.4 ) or, less commonly, anterior (if the subscapularis is deficient; Fig. 35.5 ).

Glenoid erosion is best treated by resurfacing of the glenoid if sufficient native glenoid bone is available for implantation of a glenoid component (see Chapter 36 ). Frequently, the humeral component will require revision for glenoid exposure, and two options are available to the surgeon. We may exchange the component for a smaller head size in an unconstrained arthroplasty ( Fig. 35.6 ) or change to a reverse-design arthroplasty. In general, with a functioning rotator cuff, an unconstrained arthroplasty is performed for revision arthroplasty. If rotator cuff function is significantly compromised, revision to a reverse prosthesis is performed.

Glenoid Component Failure

Glenoid component failure can vary from subtle loosening to migration of the component with severe glenoid bone loss ( Fig. 35.7 ). Additionally, mechanical failure of the implant can necessitate revision surgery ( Fig. 35.8 ). When considering revision surgery for failure of a glenoid component, the surgeon must first decide whether to simply remove the failed glenoid component or to remove the failed glenoid component and reconstruct the osseous glenoid. In debilitated patients seeking mainly pain relief without significant concern for function, isolated removal of the glenoid component is usually the best treatment option. Isolated removal of the glenoid component can be completed arthroscopically or with an open procedure. In other patients, glenoid reconstruction with iliac crest bone graft is indicated. For patients undergoing revision with an unconstrained prosthesis, we reconstruct the glenoid with an iliac crest bone graft as the first stage. Four to six months later, after complete incorporation of the bone graft, if the shoulder is still painful, we perform the second stage, which consists of placement of a new glenoid component ( Fig. 35.9 ). When performing revision surgery with a reverse-design prosthesis, glenoid reconstruction and revision can often be performed as a single stage, provided that the central post or screw of the revision glenoid component can be firmly fixed in native glenoid bone ( Fig. 35.10 ).

Just as in cases of glenoid erosion, patients requiring revision surgery for a problem with the glenoid component often require revision of the humeral component for glenoid exposure, and the surgeon can exchange the component for a smaller head size in an unconstrained arthroplasty or change to a reverse-design arthroplasty. As previously mentioned, in a patient with a functioning rotator cuff, an unconstrained arthroplasty is used for revision arthroplasty. If rotator cuff function is significantly compromised, revision to a reverse prosthesis is performed.

Reverse Glenoid Component

In our experience, failure of the glenoid component of a reverse prosthesis is far less common than failure of the glenoid component of an unconstrained shoulder arthroplasty. The most common problem that we observe is inadvertent placement of the glenoid component in a superiorly oriented position ( Fig. 35.11 ). This usually occurs when a superior surgical approach has been used to place the reverse prosthesis. Although this radiographic finding does not merit revision surgery in and of itself, revision is indicated if this problem evolves into early glenoid loosening ( Fig. 35.12 ).

Another radiographic finding related to a reverse glenoid component is inferior scapular notching. This finding can be related to excessive superior placement of the reverse glenoid component ( Fig. 35.13 ). Notching, even when it is severe, has not been shown to cause loosening of the glenoid component, and revision surgery is unnecessary in the absence of glenoid loosening.

Rarely, a traumatic injury can result in mechanical failure of the glenoid component of the reverse prosthesis ( Fig. 35.14 ). In these cases, revision is indicated to resolve the problem.