Glenoid Erosion

Glenoid erosion after hemiarthroplasty is a multifactorial problem.¹ 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).

Figure 35-1 Radiograph demonstrating osseous glenoid erosion after hemiarthroplasty.

Figure 35-2 Severe medialization of the humeral head caused by progressive glenoid erosion.

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).

Figure 35-3 Computed tomogram demonstrating central glenoid erosion after hemiarthroplasty for primary osteoarthritis.

Figure 35-4 Superior glenoid erosion in a patient who has undergone hemiarthroplasty for rotator cuff tear arthropathy.

Figure 35-5 A and B, Anterior superior glenoid erosion in a patient who has undergone hemiarthroplasty for anterior superior rotator cuff insufficiency.

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.

Figure 35-6 A, Pre-revision radiograph. B, Humeral revision in which the humeral stem has been exchanged and the humeral head exchanged for a smaller size.

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. 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. 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 of the revision glenoid component can be firmly seated in native glenoid bone (Fig. 35-10).

Figure 35-7 Radiograph showing loosening of a glenoid component.

Figure 35-8 A and B, Mechanical failure of a glenoid implant.

Figure 35-9 Preoperative radiograph (A) and postoperative radiograph(B) after removal of a loose glenoid component and bone grafting of the residual osseous defect in the glenoid.

Figure 35-10 A, Preoperative radiograph. B, Postoperative radiograph after revision of a failed unconstrained shoulder arthroplasty to a reverse shoulder arthroplasty with bone grafting of the glenoid.

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.