TO THE EDITOR:
It was with great interest that I read "Survival Analysis of Hips Treated with Core Decompression or Vascularized Fibular Grafting Because of Avascular Necrosis" (80-A: 1270—1275, Sept. 1998), by Scully et al. The authors compared vascularized fibular grafting performed at Duke University Medical Center with core decompression performed at Brown University School of Medicine. Among the hips that had Ficat stage-II or III disease1, the rate of eventual total joint arthroplasty after vascularized fibular grafting was significantly lower than that after core decompression (p < 0.0001).
While reviewing this article, I noted several potential biases that warrant further comment from the authors. First, on page 1271, column 2, paragraph 3, the authors state: "Survival, with total hip arthroplasty as the end point, was compared between the groups." Core decompression, if performed properly, is a relatively quick operation with low morbidity. In contrast, vascularized fibular grafting is associated with a much longer operative time as well as with increased morbidity. Conversion of a core decompression to a total hip arthroplasty is a relatively straightforward procedure that usually is very similar to a primary total hip arthroplasty. Conversion of a vascularized fibular grafting procedure to a total hip arthroplasty is probably much more difficult because the hole in the lateral femoral cortex is much larger than that used for core decompression and there may be extensive remodeling changes in the intertrochanteric area, similar to those seen after conversion of a failed screw-plate device to a total hip replacement. Thus, the surgeon might be more inclined to perform a total hip arthroplasty after a failed core decompression than after a failed vascularized fibular grafting procedure. Alternatively, the surgeon may be more willing to take a wait-and-see approach after vascularized fibular grafting because it is a more debilitating operative procedure that involves autogenous tissue transfer, it is associated with a longer procedural time and rehabilitation period, and it is more difficult to convert to a total hip arthroplasty.
The period of protected weight-bearing after vascularized fibular grafting is different from that after core decompression. The authors recommended protected weight-bearing for six months after vascularized fibular grafting, whereas most surgeons advise protected weight-bearing for only six weeks after core decompression. Although protected weight-bearing has not been shown to change the natural history of avascular necrosis2, the unloading effect on the hip for an additional four and a half months, combined with a reluctance to operate within the first year after an involved procedure that is associated with increased morbidity, might have decreased the number of patients who went on to early conversion to a total hip arthroplasty after vascularized fibular grafting.
At my institution, both core decompression and vascularized fibular grafting are performed for the indications that were described in the article by Scully et al. My experience with vascularized fibular grafting is not as extensive as that of the surgeons from Duke. In the ideal study, core decompression and vascularized fibular grafting would be performed at the same institution and specific, uniform, prospectively determined clinical and radiographic outcome variables would be used to decide when to perform a total hip arthroplasty because of failure of the index operation.
Stuart B. Goodman, M.D., Ph.D.: Division of Orthopaedic Surgery, Stanford University Medical Center, Stanford University School of Medicine, 300 Pasteur Drive, Room R-144, Stanford, California 94305-5341
Dr. Scully, Dr. Aaron, and Dr. Urbaniak reply:
Dr. Goodman points out that the two procedures that we discussed differ dramatically in terms of the operative time, the complexity of the procedure, and the psychological investment by the patient and the physician. We agree wholeheartedly and acknowledge that a potential bias is introduced when conversion to total hip arthroplasty is used as an end point.
Dr. Goodman also makes the point that subsequent conversion to total hip arthroplasty is more difficult after free vascularized fibular grafting. This has not been our experience. The hole that is made in the lateral femoral cortex to introduce the fibular graft does not often create difficulties. Although burring of the lateral femoral cortex is necessary in order to remove fibular remnants before a total hip arthroplasty is perfomed, this only slightly increases the complexity of the procedure. We do not believe that this introduces any substantial bias to the management of these patients.
It should be emphasized that most of our patients are referred to us for free vascularized fibular grafting by other orthopaedic surgeons who believe that core decompression is not indicated. Frequently, these patients have had a core decompression that has failed.
Finally, we concur with Dr. Goodman that a prospective, randomized study is ideally suited to compare the two procedures. However, since such data are not available at the current time, we sought to perform this comparison with existing data. Despite the biases that are inherent in such an approach, we believe that the strength of the data speaks to the outcomes of these two treatments for avascular necrosis of the femoral head.
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