TO THE EDITOR:
In “The Natural History of Untreated Asymptomatic Hips in Patients Who Have Non-Traumatic Osteonecrosis” (79-A: 359–363, March 1997), Jergesen and Khan made a valiant attempt to sort out meaningful clinical data related to a disease entity that continues to be a source of considerable controversy. The authors are to be commended on the completeness of the follow-up for most of their study group. However, since they cited the work of both Kerboul et al.2 and Ohzono et al.3, who delineated size and location factors that have an impact on the progression of the disease, it is surprising that Jergesen and Khan did not include an evaluation of these factors in their analysis. The combined angle described by Kerboul et al. and the locations described by Ohzono et al. can be determined for all stage-II and stage-III lesions. Both Kerboul et al. and Ohzono et al. used radiographic methods to demarcate the extent and location of a lesion although they are not as accurate as localization with magnetic resonance imaging.
In contradistinction to many other authors, Jergesen and Khan concluded that most asymptomatic radiographically evident lesions (ten of nineteen in their study) in patients who have a symptomatic contralateral hip will not progress to collapse within five years. The authors would have done the readership a considerable service if they had measured the combined angle, as described by Kerboul et al.2, and determined the location of the lesion, as described by Ohzono et al.3, for these nineteen hips. Since symptoms developed within thirty-six months in six of the nineteen patients, it is important to identify patients who are at risk for symptoms before those symptoms develop. We agree that asymptomatic patients should be followed without operative treatment, but we believe that a disease that leads to destruction of the femoral head and total joint replacement in nearly 50 per cent of patients should not be viewed as a somewhat benign process. It is instead one that necessitates careful follow-up. Although we also do not manage patients who are initially asymptomatic, an argument could be made that such a disease should be treated operatively, especially when we do not know the ultimate fate a priori.
We agree that osteonecrosis never developed in most of the asymptomatic radiographically normal hips. Of the seventy-five patients who were seen between 1978 and 1987, twenty-nine (39 per cent) had symptoms bilaterally and an additional twenty-two (29 per cent) had radiographic evidence of involvement. Radiographic evidence of osteonecrosis developed in three of the twenty-three initially asymptomatic radiographically normal hips (excluding the hip that had a core decompression). Thus, evidence of bilateral disease eventually developed in 72 per cent (fifty-four) of the seventy-five patients in the series, which is at the high end of expected bilaterality.
The overall effect of this article is to suggest a wait-and-see attitude toward the radiographically evident asymptomatic osteonecrotic lesion. However, the stakes are high because progression usually leads to a total hip arthroplasty. Before this approach is accepted, an exhaustive attempt to elucidate the characteristics of patients who will have progression is warranted.
David S. Hungerford, M.D.; Michael A. Mont, M.D.: Department of Orthopaedic Surgery, The Johns Hopkins University at Good Samaritan Hospital, Professional Office Building, Suite G-1, 5601 Loch Raven Boulevard, Baltimore, Maryland 21239
Dr. Jergesen and Dr. Khan reply:
We would like to respond to the two most important points raised by Hungerford and Mont. The first concerns the issue of image analysis in determining the prognosis for asymptomatic hips with radiographic evidence of osteonecrosis. As stated in our article, we strongly advocate additional investigation into the use of modern imaging techniques, such as high-resolution computerized tomography and magnetic resonance imaging, to delineate the characteristics of the lesion in such hips. Like other investigators1,4, we have found plain radiography to be of limited use both because of interobserver and intraobserver variability and because of the inherent drawbacks of defining a complex three-dimensional process with a planar imaging technique. Of note is that we tried the radiographic classification technique advocated by Ohzono et al.3 during our study but we abandoned it because we had difficulty clearly differentiating stage-IB from stage-IC lesions, a distinction that is based on the lateral extent of the involvement of the femoral head. In our view, the prognosis for such hips is best determined by techniques that detect occult fractures, accurately define the volume and location of the necrotic lesion, and accurately define the volume and location of the reactive and reparative response adjacent to the necrotic lesion.
The second point raised by Hungerford and Mont focuses on the issue of treatment. In our article, we were careful not to take a position regarding treatment of asymptomatic hips that had radiographic evidence of osteonecrosis. We have shown that while the disease appears to progress more slowly in such hips, the outcome is not always benign, as evidenced by the fact that an arthroplasty was eventually performed for seven of nineteen hips. The approach of treating all such hips as soon as they are diagnosed can be convincingly shown to be efficacious only if the outcome in treated hips is better than that in untreated hips. Most retrospective studies on joint-preserving treatments for osteonecrosis have failed to shed light on this question; either the initial pain status of the treated hips was not specifically defined or the duration of follow-up was too short. A prospective, randomized study with a minimum duration of follow-up of five years would provide valuable information; such a study should include sophisticated imaging data to adequately define characteristics of the lesion that may be of prognostic importance. To date, we know of no such studies. Given this current state of knowledge, we believe that the optimum treatment of asymptomatic, radiographically involved hips remains an open question and, therefore, recommendations for treatment should be made on a case-by-case basis.
Harry E. Jergesen, M.D.: Department of Orthopaedic Surgery, University of California at San Francisco Medical Center, 500 Parnassus Avenue (MU-320W), San Francisco, California 94143-0728
A. Shabi Khan, M.D.: Division of Orthopaedic Surgery, Stanford University Medical Center, 300 Pasteur Drive, Room R-171, Stanford, California 94305
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