Commentary & Perspective

Commentary & Perspective on
"Quality-of-Life Outcome Following Hemiarthroplasty or Total Shoulder Arthroplasty in Patients with Osteoarthritis: A Prospective, Randomized Trial"
by Ian K.Y. Lo, MD, FRCSC, et al.

Commentary & Perspective by
Joseph P. Iannotti, MD, PhD, and Boris Bershadsky, PhD*,
The Cleveland Clinic Foundation, Cleveland, Ohio

A fundamental premise in joint replacement surgery is that the pain associated with osteoarthritis is in part due to the loss and destruction of the joint surfaces. If we further assume that joint replacement is successful as a result of resurfacing of the joint surfaces, then it would seem that resurfacing of both surfaces of the joint would yield better results than the resurfacing of only one. This has been the basis for resurfacing both sides of the hip and knee joints in lower-extremity prosthetic arthroplasty. Therefore, why would we consider these same principles to be less valid with regard to shoulder arthroplasty? And, if this assumption is true, then why does the study by Lo et al. demonstrate no significant difference in outcome (pain or function) between the two treatment groups?

Most of the answers have been identified by the authors. First, and most importantly, the sample size was not large enough to demonstrate statistical significance. Although there was a clear trend toward a more favorable result in all parameters after total shoulder arthroplasty, it is likely that a larger number of patients would have demonstrated a significant difference between groups. Gartsman et al. also compared the clinical results of hemiarthroplasty and total shoulder arthroplasty for osteoarthritis1. That study also showed a trend toward a more favorable outcome in total shoulder arthroplasty. The Gartsman study was also a small prospective randomized clinical trial, and their data also suggested that a study with approximately twice the number of patients would have shown statistical significance in favor of total shoulder arthroplasty.

Also suggestive of a more favorable outcome with total shoulder arthroplasty is the presence of three patients who had poor outcomes in the hemiarthroplasty group because of persistent pain associated with glenoid arthrosis. Although two of these three patients underwent revision to a total shoulder arthroplasty, only one improved and the third has not yet had a revision. The failure of hemiarthroplasty is presumed to be secondary to persistent or progressive glenoid disease, but the lack of expected improvement with revision to total shoulder arthroplasty decreases the likelihood of demonstrating significance in favor of glenoid resurfacing when the sample size is too small.

The literature also suggests that there is an increasing incidence of pain due to progressive glenoid arthrosis after hemiarthroplasty within the first five to ten years after arthroplasty2,3. To confound the issue, there is also an increased incidence of glenoid component loosening in patients who have undergone total shoulder arthroplasty4. The fact that both problems increase with time suggests that it is important to know the difference in outcome between total shoulder and hemiarthroplasty with longer term follow-up. On the basis of these data on longer term follow-up of hemiarthroplasty, one could speculate that a difference in outcome between the two treatment groups in this study might be observed with a longer follow-up. We can hope that there will be a sufficient number of patients from this study available and willing to undergo follow-up in a few years.

Glenoid bone loss, eccentric wear, and humeral head subluxation are factors that affect outcome5. Hemiarthroplasty and total shoulder arthroplasty have varying degrees of clinical success depending on the severity of these anatomic factors5. It was assumed, in this study, that these anatomic factors were evenly distributed between the two treatment groups, but their prevalence and severity were not defined in the data presented. When there is a small sample size, small differences in the distribution of patients with anatomic factors that affect the outcome of each treatment group to a variable extent could influence the ability to show a difference between treatment groups.

This study lays a good foundation for subsequent clinical trials. Many highly correlated outcome measures were studied. Appropriate analysis and discussion of the data collected by the authors could help to improve the chances for the success of subsequent clinical trials. We recommend that future such studies (1) select and justify the most appropriate measures of outcomes to overcome the problem of multiple comparison and lower the cost of a larger study, (2) estimate the sample size that is needed to detect a significant difference between the interventions of interest with respect to selected measures, (3) reveal the most important adjustors to support the stratified research design, and (4) utilize the statistical advantages of one-sided null hypotheses.

*The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

References

1. Gartsman GM, Roddey TS, Hammerman SM. Shoulder arthroplasty with or without resurfacing of the glenoid in patients who have osteoarthritis J Bone Joint Surg Am. 2000;82:26-34.
2. Cofield RH, Frankle MA, Zuckerman JD. Humeral head replacement for glenohumeral arthritis. Semin Arthroplasty. 1995;6;214-21.
3. Levine WN, Djurasovic M, Glasson JM, Pollock RG, Flatow EL, Bigliani LU Hemiarthroplasty for glenohumeral arthritis: results correlated to degree of glenoid wear. J. Shoulder Elbow Surg. 1997;6:449-54.
4. Torchia ME, Cofield RH, Settergren CR. Total shoulder arthroplasty with the Neer prosthesis: long-term results J Shoulder Elbow Surg. 1997;6:495-505.
5. Iannotti JP, Norris TR. Influence of preoperative factors on outcome of shoulder arthroplasty for glenohumeral osteoarthritis. J Bone Joint Surg Am. 2003;85:251-8.