The Journal of Bone and Joint Surgery

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Commentary & Perspective

Commentary & Perspective on
"The Reverse Shoulder Prosthesis for Glenohumeral Arthritis Associated with Severe Rotator Cuff Deficiency: A Minimum Two-Year Follow-up Study of Sixty Patients"
by Mark Frankle, MD, et al.

Commentary & Perspective by
Frederick A. Matsen, MD*,
University of Washington, Seattle, Washington

We are indebted to Dr Frankle and his coauthors for a provocative article on one of the most exciting (and anxiety-provoking) topics in shoulder surgery: the reverse shoulder prosthesis. I have recently returned from the Third International Conference on Shoulder Arthroplasty organized by Dominique Gazielly in Paris (April 2005), where I had the opportunity to hear of the intermediate-term results from proponents of this procedure from around the world. The conclusions drawn from that conference are applicable to this paper: (1) the reverse prosthesis can lead to dramatic improvements in comfort and function in patients with the "terrible triad" of cuff deficiency, glenohumeral arthritis, and anterosuperior instability—a triad for which no other solution is as effective; (2) the procedure is technically demanding, so that even the experts experience difficulties with exposure, screw placement, and stability; (3) the major complication rate (infection, fracture, loosening, hardware failure) is higher than that of any other type of shoulder arthroplasty, increases with time, and is much greater for revision surgery than for primary arthroplasty; (4) the indications for this procedure have a strong tendency to "creep" to cuff tear arthropathy without instability and even to cuff tears without arthropathy; (5) many of the indications for a reverse prosthesis result from previous surgery in which the coracoacromial arch has been violated by acromioplasty; and (6) the cost versus the effectiveness of this procedure has yet to be determined, especially when the complications are included in the analysis.

In relating these ideas to the manuscript "The Reverse Shoulder Prosthesis for Glenohumeral Arthritis Associated with Severe Rotator Cuff Deficiency," I have grouped my comments in terms of indications, mechanics, and evaluation. Necessarily, I am presenting my interpretation of the prevailing wisdom from many presentations and discussions rather than from peer-reviewed publications, as the latter are lagging behind in this rapidly moving experiment.

Indications

Patients with the triad of cuff deficiency, arthritis, and superior instability are typically elderly, frail, at risk for falls, and beset by complexities related to their health and social support. By definition, the goals in treating these patients are limited. This means that the prospect of any surgical procedure, particularly one as aggressive as a reversed shoulder, needs to be considered with great conservatism and in light of the options of nonoperative management or less aggressive surgical approaches. While the authors point out that the results of hemiarthroplasty for cuff tear arthropathy "have not been uniform," this is in large part due to an inability to deal with instability when present. In the absence of instability, humeral hemiarthroplasty appears to have a more favorable risk-to-benefit ratio than does a reverse prosthesis in the treatment of cuff tear arthropathy. This is particularly the case in the common form of cuff tear arthropathy in which there is femoralization of the proximal humerus and acetabularization of the glenoid-coracoacromial arch.

In this paper, diagnoses included primary cuff tear arthropathy with collapse of the humeral head, primary cuff tear arthropathy without collapse of the humeral head, failed rotator cuff surgery, massive rotator cuff tear, posttraumatic arthritis, and rheumatoid arthritis. The degree of instability presented by these shoulders (and thus the rationale for a reverse prosthesis) was not clear.

Mechanics

While the authors describe their prosthesis as "semiconstrained," the fact of the matter is that the fulcrum is fixed. This means that forces applied to the humerus, for example, from a fall or from repeated use, may cause humeral or scapular fracture and prosthesis failure by fatigue, or may result in dislocation.

The reverse prosthesis described by Frankle et al. differs from the Delta-III prosthesis in a number of ways, but perhaps the most important difference is the location of the center of rotation of the glenoid sphere. Here the center is lateralized; with the Delta-III, the center is located on the surface of the glenoid bone. The advantage of lateralization may be protection of the scapular from notching. The disadvantages include a reduced deltoid moment arm and an increased moment on the glenoid fixation. Substantial follow-up of carefully characterized cases will be required to evaluate the relative advantages of these two approaches.

Evaluation

It is my sense that a two-year follow-up is likely to reveal the best results we will see after a reverse shoulder prosthesis—long enough for muscle recovery, but not long enough for most of the complications that will ensue with time. Although we view these patients as elderly (the average age of patients in this series was seventy-one years), the life expectancy in the United States is now seventy-seven years, and the life expectancy of a seventy-five-year-old woman is twelve more years! In this series, as in those of other reverse prostheses, complications increase with time. Seven of the sixty patients in this series required revision surgery at an average of twenty-one months after surgery. It remains to be seen whether another seven will require revision every two years, but if this rate continues, most prostheses would need revision within the expected life of the patient.

With respect to methods of evaluation, my bias has always been to determine the ability of patients to do standardized functions before and after a surgical procedure so that everyone can easily understand the functional benefit. Without this degree of rigor, we find ourselves with statements such as "The two patients whose shoulders were converted to a hemiarthroplasty rated the outcome as good and satisfactory at the most recent follow-up examination." This begs the question, if hemiarthroplasty can give good and satisfactory results when used as a revision of a reversed prosthesis, what might the results have been if a hemiarthroplasty had been used primarily?

Again, I thank Dr Frankle for his stimulating article. None of my comments are intended to be critical of his work, but rather to encourage us all to be rigorous in our approach to these challenging shoulder problems. We owe our patients nothing less.

In conclusion, my current thoughts on the reverse prosthesis recall Bob Dylan's lyric "go lightly from the ledge, babe."

*The author did not receive grants or outside funding in support of his research or preparation of this manuscript. The author received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity (DePuy). A commercial entity (DePuy) paid or directed, or agreed to pay or direct, benefits to a research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.