Copyright © 2006 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective
Commentary & Perspective by
William J. Maloney, MD
Department of Orthopaedic Surgery, Stanford University, Stanford, California
The number of patients needing revision hip arthroplasty continues to grow in the United States. Despite advances in implant design and surgical technique, the overall revision burden has not decreased substantially. Although revision total hip replacement represents a substantial cost, little has been published with regard to the factors that predict functional outcome following revision hip arthroplasty.
In this study by Davis et al., the authors attempted to identify predictors of pain and physical function at two years following revision total hip arthroplasty. In addition, they attempted to assess whether the waiting time for revision total hip arthroplasty affected the functional outcome. This is an important area of research in countries that have a national health care system and is especially of interest in countries where waiting lists are long for these types of procedures.
The study was done at a high-volume arthroplasty center where the operating surgeons were also experienced arthroplasty surgeons. One hundred and twenty-six patients were followed prospectively and were assessed preoperatively with use of standard outcome measures. Interestingly, postoperative improvement in the Western Ontario and McMaster Universities (WOMAC) pain and function scores plateaued at six months. This is a surprising outcome considering that patients are often required to use walking support for three to six months after revision total hip arthroplasty because of the presence of structural grafts or complex reconstructions. Additionally, data from Europe suggest that maximum functional improvement does not occur for two to five years following primary arthroplasty1; therefore, it is interesting to see the functional scores plateau at only six months postoperatively in a group of revision patients.
The authors further noted that the preoperative pain score and comorbidity were significant predictors of pain at two years (p = 0.002). Comorbidity has long been recognized to be a predictor of functional outcome after total hip replacement but not necessarily a predictor of pain relief. Charnley recognized the importance of functional class as it relates to outcome early in the history of hip replacement surgery and developed his classification system for comorbidities. Davis et al. found that there was a strong trend toward preoperative function predicting postoperative function (p = 0.07). It is likely that, with a larger number of patients, the significance level of p ≤ 0.05 could have been reached. From a clinical standpoint, it is my opinion that one can conclude that preoperative function is an important predictor of postoperative function. The authors weren't able to demonstrate that waiting time had a significant effect on outcome. Twenty-eight of the 126 patients had a complication. Complications were found to be predicative of outcome for both pain and function.
So what's the take-home message? First, revision surgery results in a predictable and significant improvement in both pain and function. Surprisingly, pain and functional improvement plateaued at six months postoperatively. It may be possible that, if the patients had been followed for a longer period, the authors might have seen an incremental improvement between two and four years, reflecting a delay in functional improvement similar to that seen in patients who have undergone primary hip arthroplasty.
Second, preoperative pain and function were predictive of postoperative pain and function. The message is simple. Patients who are in more pain or who are more functionally disabled prior to surgery do not achieve the same results as those who are in less pain or who are in better overall condition. Finally, complications had a definite impact on outcome.
Going forward, it would be interesting and helpful to the revision arthroplasty surgeon to have more detailed information on the preoperative condition of these patients and to analyze the results on the basis of subclasses of patients who require revision surgery. In this paper, sample size dictated that all patients had to be lumped into a single group. However, an experienced arthroplasty surgeon realizes that all revisions are not the same. One would not expect the same outcome in a patient who is undergoing a liner exchange for polyethylene wear and moderate osteolysis—and who is essentially asymptomatic preoperatively—compared with a patient who requires a structural allograft for severe bone loss and has a grossly loose component. Similarly, it would be useful if the complications were analyzed separately. The authors listed the particular complications that occurred in this group of patients who underwent revision hip replacement. However they weren't able to analyze the effect of a given complication on outcome. For example, one would suspect that a deep wound infection might have a very different effect on pain and functional outcome compared with a single postoperative dislocation.
This study is clearly a beginning and not an end. More data of this type are required to enable the revision arthroplasty surgeon to adequately inform the patient as to what to expect after revision hip replacement.
*The author did not receive grants or outside funding in support of his research for or preparation of this manuscript. He 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 author is affiliated or associated.
Reference
1. Roder C, Parvizi J, Eggli S, Berry DJ, Muller ME, Busato A. Demographic factors affecting long-term outcome of total hip arthroplasty. Clin Orthop Relat Res. 2003;417:62-73.
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