Copyright © 2006 by The Journal of Bone and Joint Surgery, Inc.

Commentary & Perspective

Commentary & Perspective on
"Influence of Acetabular Coverage on Hip Survival After Free Vascularized Fibular Grafting for Femoral Head Osteonecrosis"
by Thomas F. Roush, MD, et al.

Commentary & Perspective by
David R. Steinberg, MD, and Marvin E. Steinberg, MD*,
Department of Orthopaedic Surgery, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania

Posted October 12, 2006

The treatment of nontraumatic osteonecrosis of the femoral head in adults continues to be both challenging and controversial. Without specific treatment, most lesions will progress and require eventual arthroplasty. In attempts to preserve rather than to replace the femoral head, nonoperative management has included the use of ultrasound, electrical stimulation, marrow injection, anticoagulation, and bisphosphonates. The efficacy of these techniques is currently being evaluated. A number of surgical procedures are in use and include core decompression, vascularized and nonvascularized grafting procedures, and various osteotomies. Opinions differ as to the effectiveness of these procedures, and strict indications and contraindications for each have not been established.

Roush et al. have retrospectively reviewed 200 hips in patients with osteonecrosis, all treated with free vascularized fibular grafting. They have attempted to correlate radiographic outcome with a number of preoperative variables and have focused in particular on the influence of acetabular coverage. They found that 24% of the 200 hips underwent conversion to total hip replacement at a mean of 7.5 years following surgery and that an additional 15% of 91 hips showed radiographic progression at a mean of three years. There was a significant correlation with the extent of acetabular coverage (p < 0.001). In hips with a center-edge angle of ≤30°, 55% demonstrated progressive collapse and 45% required total hip replacement. In contrast, in hips with a center-edge angle of >30%, only 10% underwent collapse and 6% required total hip replacement. They found an association between failure and lesion size, although the correlations were not significant.

The authors are to be congratulated for being the first, to our knowledge, to evaluate acetabular coverage as a separate prognostic factor in determining outcome following surgery for osteonecrosis. Although the study was limited to patients undergoing free vascularized fibular grafting, it raises the question as to whether these observations can also be applied to hips undergoing other types of joint-preserving procedures as well as to hips treated symptomatically. This should be evaluated in subsequent studies.

The authors acknowledge certain limitations of this study. Only ninety-one of 200 hips had sufficient radiographic follow-up, and this was limited to a mean of three years, which makes predicting long-term results difficult. Clinical outcome was determined solely on the basis of whether total hip replacement was required. Outcome instruments such as the Harris hip scores were not employed, as most patients received postoperative follow-up from physicians not involved in this study. Although the authors measured the amount of preoperative femoral head collapse, they did not indicate specifically whether this factor influenced the outcome, nor did they relate this to acetabular coverage. Other authors have noted a distinct correlation between outcome and both lesion size and head collapse1-4.

The authors used a center-edge angle of 30° as a dividing line and found satisfactory outcomes in most hips when the angle was >30° and poor results in most hips when the angle was ≤30°. This marked difference was rather surprising because the mean center-edge angle in hips with satisfactory outcomes was 30° to 32°, and the mean center-edge angle of all hips was 30° (range, −2° to 48°). Considerable overlap was also noted—not all hips with smaller angles did poorly, nor did all hips with larger center-edge angles do well. This raises the question as to what is an abnormal or "suboptimal" center-edge angle. The literature cites a mean of 35° in a Caucasian population, with a "normal" range of 25° to 40°5. The authors reported that sixty of 200 hips (30%) had a center-edge angle that was <25°. This is much higher than in the general population, in which the incidence of dysplasia has been estimated at well under 1%. Why did so many hips in this series seem to have insufficient acetabular coverage? Is it possible that some of the low center-edge angles were in part due to femoral head deformity, since 79% of hips had already undergone some degree of collapse?

The primary purpose of this study was not to define the role of free vascularized fibular grafting in the treatment of osteonecrosis; however, this remains a somewhat controversial topic of interest. Approximately 39% of hips in this series underwent progressive collapse or required total hip replacement. This compares favorably with other modalities of treatment and other reports of free vascularized fibular grafting as all hips treated had radiographic changes and 157 of 200 had some degree of head collapse. It must be noted that the authors have had a great deal of experience with this procedure, which is technically demanding and not without complications and which should be done only by those with appropriate training, experience, and facilities.

In their conclusions, the authors refrained from attempting to set rigid criteria for the performance of free vascularized fibular grafting. Instead, they appropriately suggested that "orientation of the acetabulum and the magnitude of developmental dysplasia of the hip should be included in the preoperative assessment of patients with osteonecrosis of the femoral head." As with all worthwhile studies, this one has given us much to consider and many questions to answer.

*The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. They 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 authors are affiliated or associated.

References

1. Berend KR, Gunneson EE, Urbaniak JR. Free vascularized fibular grafting for the treatment of postcollapse osteonecrosis of the femoral head. J Bone Joint Surg Am. 2003;85:987-93.
2. Sotereanos DG, Plakseychuk AY, Rubash HE. Free vascularized fibula grafting for the treatment of osteonecrosis of the femoral head. Clin Orthop Relat Res. 1997;344:243-56.
3. Soucacos PN, Beris AE, Malizos K, Koropilias A, Zalavras H, Dailiana Z. Treatment of avascular necrosis of the femoral head with vascularized fibular transplant. Clin Orthop Relat Res. 2001;386:120-30.
4. Steinberg ME, Mont MA. Osteonecrosis. In: Chapman MW, editor. Chapman's orthopaedic surgery, 3rd ed. Philadelphia: Lippincott Williams and Wilkins; 2001. p 3263-308.
5. Staheli LT. Acetabular dysplasia: treatment by pelvic osteotomy. In: Steinberg ME, editor. The hip and its disorders. WB Saunders; Philadelphia: 1991. p 335-53.