TO THE EDITOR:
In the article "Survival Analysis of Hips Treated with Core Decompression or Vascularized Fibular Grafting Because of Avascular Necrosis" (80-A: 1270—1275, Sept. 1998), Scully et al. compared the results of core decompression and vascularized fibular grafting done at two different centers. The conclusions, with the end point of success being avoidance of a total hip arthroplasty, seemed to favor vascularized fibular grafting for Ficat stage-II and III lesions1, with little difference between the results of the two methods when used to treat Ficat stage-I lesions.
It is vital for practitioners who manage patients with avascular necrosis to assess the efficacy of treatment measures. This article, however, still leaves open the question of the efficacy of core decompression and vascularized fibular grafting. I have two major concerns regarding the comparison of these two treatment groups.
My first concern is that the two groups were not treated similarly in the postoperative period. The exact postoperative regimen was not outlined for the patients who had core decompression, but those who had vascularized fibular grafting were managed with protected weight-bearing for six months. The usual course of protected weight-bearing after core decompression is much shorter, typically about six weeks. It is possible that the only difference in the results between core decompression and vascularized fibular grafting was due to the extended period of protected weight-bearing associated with the latter. The avascular bone revascularizes eventually, but the patient may sustain a subchondral fracture either before or during the revascularization process. It is not clear that the presence of a vascularized fibular graft prevents this subchondral collapse, and protected weight-bearing may be the critical factor in allowing the bone to heal before collapse occurs.
There are also serious possibilities for bias in the use of avoidance of total hip arthroplasty as the sole criterion for success of the operation. When a patient has a lengthy, painful, and expensive operation, he or she usually has a strong desire to get better. The surgeon who performs such an operation also has a strong desire for the patient's condition to improve. The decision as to whether to proceed with a total hip arthroplasty can be strongly influenced by the patient's and surgeon's desire to avoid such a procedure and is not necessarily related to the preservation of the femoral head or the prevention of subchondral collapse. I have not performed vascularized fibular grafting, but I followed three patients who had had this procedure performed at a major medical center. When the patients were first seen in my office, all three would have been considered to have a successful result because they had avoided total hip arthroplasty; however, all three had collapse of the femoral head and one of them went on to have a total hip arthroplasty. One patient also had major complications at the donor site. In no patient was the collapse of the head any less severe after the vascularized fibular grafting than it would have been had it not been treated. Some form of radiographic assessment of the sphericity of the femoral head or the prevention of subchondral collapse would be very useful in the comparison of treatment methods.
Random assignment of patients to both groups, use of the same postoperative regimen of protected weight-bearing for each group, and grading of the final result on the basis of radiographic criteria of preservation of the femoral head as assessed by a blinded radiologist are necessary to assess the efficacy of these two procedures. Once such a study is performed, vascularized fibular grafting can be compared with core decompression and it can be decided if the increased morbidity and expense of vascularized fibular grafting justifies its expanded use.
Kim J. Chillag, M.D.: Moore Orthopaedic Clinic, 1 Richland Medical Park, Suite 110, Columbia, South Carolina 29203
Dr. Scully, Dr. Aaron, and Dr. Urbaniak reply:
We appreciate Dr. Chillag's perspective and acknowledge his experience with three patients who had been managed with vascularized fibular grafting for avascular necrosis. Dr. Chillag raises a concern that was also raised by the authors of the other letters, namely, that a potential bias is introduced by the emotional investment of the patient and the surgeon in preserving the femoral head with vascularized fibular grafting. Certainly, a similar bias is seen in the fields of trauma and oncology with regard to limb salvage. We acknowledged this potential bias in the manuscript, and we believe that while it may have influenced the end point of total hip arthroplasty to favor fibular grafting, it does not fully explain the magnitude of the difference found in our study. We see no means of controlling for this potential bias and simply acknowledge that it exists and is of unknown magnitude.
Dr. Chillag also suggests that the difference in postoperative regimen may have contributed to the difference in outcome. As we are all aware, patient compliance with regard to restricted weight-bearing is less than absolute, and this was probably true for both treatment groups. Other investigators have reported on the efficacy of restricted weight-bearing in altering the natural history of the disease process; some studies have demonstrated that the natural history is not altered by this intervention2,4, whereas others have been inconclusive3. The fact that the period of protected weight-bearing only represented a fraction of the fifty-month observation period suggests that, if collapse were to have happened, it would have been observed within this period.
Finally, Dr. Chillag proposes that a prospective, randomized study should be performed in order to demonstrate the efficacy of this procedure definitively. We concur that such a study, stratified according to age, Ficat stage1, and percent involvement of the femoral head and designed to compare functional and radiographic outcomes, would be ideally suited to answer the questions from a scientific standpoint.
Sean P. Scully, M.D., Ph.D.; James R. Urbaniak, M.D.: Duke University Medical Center, Boxes 3312 (S. P. S.) and 2912 (J. R. U.), Durham, North Carolina 27710
Roy K. Aaron, M.D.: Brown University School of Medicine, Southwest Pavilion 524, 593 Eddy Street, Providence, Rhode Island 02903