TO THE EDITOR:
I question the effectiveness of the osteotomy used and the conclusions drawn in "Corrective Osteotomy for Osteonecrosis of the Femoral Head. The Results of a Long-Term Follow-up Study" (78-A: 1032—1038, July 1996), by Mont et al.
It has been well recognized that the location and size of a necrotic lesion are related to the prognosis. The authors stated that the criteria for the operation included an arc of at least 20 degrees on the lateral aspect of the femoral head that was free of any underlying necrotic bone. This means that most of the necrotic lesions included in the study occupied less than the medial two-thirds of the weight-bearing portion (type-I-A or I-B osteonecrosis according to the radiographic classification of the Japanese Investigation Committee8,11 or type-A or B according to the magnetic resonance imaging classification10 or the classification of the Association Research Circulation Osseous3). Such a population would have had good clinical results even without operative intervention8,10,11.
It was odd to see one of the so-called satisfactory results in Figures 1-A, 1-B, and 1-C because the neck-shaft angle was reduced less than 5 degrees postoperatively, even though the authors stated that the amount of varus correction desired ranged from 20 to 42 degrees (mean, 28 degrees). The femoral neck in Figures 1-B and 1-C appears to be in varus. However, judging from the distance between the lateral edge of the femoral head and the acetabular beak, there was no medial shift of the necrotic lesion (or medial rotation of the head itself) against the weight-bearing portion of the acetabulum. Thus, the apparent varus appearance of the femoral neck was due to abduction of the hip and pelvis. This is a good example of a patient who would have had a good prognosis with non-operative management. Additionally, the article lacked the most important information: the preoperative and postoperative location of the lesion.
Finally, the authors concluded that corrective osteotomy, of which the main component is a varus osteotomy, has an important place in the strategy for treatment of osteonecrosis of the femoral head in selected patients. However, as the authors included patients who would have had a good result without an operation, they cannot base their conclusion on the data presented in their paper.
Nobuhiko Sugano, M.D., Ph.D.: Department of Orthopaedic Surgery, Osaka University Medical School, 2-2 Yamadaoka, Suita 565, Japan
Dr. Mont, Dr. Fairbank, Dr. Krackow, and Dr. Hungerford reply:
On the basis of the location, all of the lesions in this study were type III-B or III-C according to the radiographic classification of the Japanese Investigation Committee8,11 or type B or C according to the magnetic resonance imaging classification10. We have encountered type-A lesions in our practice only rarely, and we agree with Dr. Sugano that type-A lesions are expected to collapse.
However, the type-B and C lesions in our study had collapsed. All were stage-III lesions according to the classification of Ficat and Arlet2, stage-IV lesions according to the classification of Marcus et al.5, stage-IV lesions according to the classification of Steinberg et al.9, or stage-IV lesions according to the Association Research Circulation Osseous1. The prognosis for these lesions has been noted by several authors to be abysmal without operative treatment or even after many types of operative treatment, such as core decompression6,7.
The lesions all had a combined necrotic angle4 of more than 150 degrees. We found that the largest lesions (a combined necrotic angle of more than 200 degrees) fared poorly. Lesions of this size would be classified as severe involvement of the head with use of the schema of Steinberg et al.9 (more than 30 per cent involvement) or with use of the multiple classifications schemas from Korea and Japan (more than 60 per cent involvement)8,10,11. The lesions that were slightly smaller (a combined necrotic angle of less than 200 degrees or 15 to 30 per cent involvement of the head) were the ones that did well in this study, and hence our recommendation is to perform a repositioning osteotomy in this group of patients who would have a poor prognosis with other methods of treatment.
Six of our patients had a failed core decompression, and they were all destined for hip replacement (which had been offered to some) unless another reasonable intervention, such as vascularized bone-grafting or osteotomy, was offered. These patients avoided a total hip replacement for the mean follow-up interval of 11.5 years, and the rate of success was close to 90 per cent for the corticosteroid-associated and medium-size lesions. We believe that these results are important in light of the very poor prognosis that these patients have otherwise.
In summary, in his comments concerning non-progression of the lesion in our patients who had osteotomy for osteonecrosis, Dr. Sugano failed to recognize that all of these lesions had already progressed. All of the patients were symptomatic and had various degrees of collapse.
Michael A. Mont, M.D.; David S. Hungerford, M.D.: Good Samaritan Hospital, Professional Office Building, G-1, 5601 Loch Raven Boulevard, Baltimore, Maryland 21239
Adrian C. Fairbank, F.R.C.S.: St. George's Hospital, Blackshaw Road, London SW17 0QT, England
Kenneth A. Krackow, M.D.: Buffalo General Hospital, 100 High Street, Buffalo, New York 14203