The Journal of Bone and Joint Surgery

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Commentary & Perspective

Commentary & Perspective on
"Treatment for Osteonecrosis of the Femoral Head: Comparison of Extracorporeal Shock Waves with Core Decompression and Bone-Grafting"
by Ching-Jen Wang, MD, et al.

Commentary & Perspective by
Jan D. Rompe, MD, and Nicola Maffulli, MD, MS, PhD, FRCS(Orth)*,
OrthoTrauma Clinic, Gruenstadt, Germany (J.D.R.), and Department of Trauma and Orthopaedic Surgery, Keele University School of Medicine, Stoke-on-Trent, Staffordshire, United Kingdom (N.M.)

Dr. Wang and colleagues have reported a randomized-controlled trial in forty-eight adult patients with stage-I, II, or III osteonecrosis of the hip, comparing noninvasive single-treatment high-energy shock-wave application (a total of 6000 impulses; energy flux density equivalent to 0.62 mJ/mm²) to core decompression and nonvascularized fibular grafting. At a minimum of two years of follow-up, the pain and Harris hip scores were significantly better in the shock-wave group than in the surgical group. Total hip replacement was required in 10% of the shock-wave group, and in 32% of the surgery group.

We compliment the authors for a carefully prepared pilot study that provides new, and most importantly, scientifically tested information about the potential role of shock-wave application in the treatment of early stage osteonecrosis of the adult hip.

There are relatively few reports on shock-wave treatment for osteonecrosis of the hip, and certainly this management modality will remain controversial. Even in experienced hands, reproducible application of high-energy shock-wave treatment to the femoral head is not simple, and the results from subsequent reports might not always be as favorable as this report from Wang and colleagues was. We would also caution that because of the critical neurovascular structures that lie in direct anatomical proximity to the femoral head, it is important that the application of high-energy shock-wave treatment be carried out by experienced physicians in this technique.

The authors correctly state that surgical treatment is usually indicated even for early stage osteonecrosis of the hip. However, the prognosis varies considerably depending on the extent of involvement. ARCO (Association Research Circulation Osseous) involvement is potentially reversible, but the point of no return for almost all patients is when stage-II or greater involvement occurs. The prognosis for further progression for stage I or II depends primarily on the extent and location of the lesion. Only the rare, small-to-medium-sized lesions in the medial or central location may have a good prognosis over the course of five years or more. The much more common large-sized and laterally located lesions will have a probability of about 80% of progressing to femoral collapse within two years¹.

The efficacy of the treatment might have been easier to discern if the authors had concentrated on one subgroup with a sufficient number of patients. The reader cannot deduce whether all of the treated patients were symptomatic (although one presumes so), nor can the reader know the exact localization (medial, central, lateral) and extent of the lesions (mild [<15% of head affected], moderate [15% to 30%], severe [>30%]) regarding the ARCO stages. This is particularly regrettable when the authors report regression of five of thirteen ARCO stage-I or stage-II lesions after shock-wave treatment. It will be necessary for future trials to have more information on this specific subgroup of successfully treated patients.

According to Table V, the size of the lesion was evaluated on plain radiographs and magnetic resonance images before and after treatment. In patients showing a regression from ARCO stage-II lesions (abnormal radiograph and abnormal magnetic resonance image) and ARCO stage-I lesions (normal radiograph, abnormal magnetic resonance image), it is not clear whether the sizes were measured uniformly by magnetic resonance imaging at all follow-ups or whether a mixture of radiographic and magnetic resonance imaging measurements were used.

The authors state that the radiologist involved in the evaluation of the ARCO stages of patients of both groups was blinded to the nature of treatment. This will have been the case before treatment, but as one of the study arms involved core decompression, the "blinded" radiologist might have been subjected to bias during the postoperative evaluation. This may be an additional potential source for bias in this study, as clinical assessment was not reported to have been performed independent of the treating physician.

It is not entirely clear how the authors approached the treatment of patients with bilateral disease in either group. Because core decompression and nonvascularized fibular graft required up to six months of protected weight-bearing after the operation, compared with only four to six weeks after high-energy shock-wave treatment, it might have been necessary to delay surgery on the contralateral hip for quite some time, thereby allowing the condition to progress and adversely affect the outcome.

A weakness of the study is whether the optimal dose of shock waves was delivered to these patients. Recently, the authors had reported an optimal treatment of 500 impulses of shock waves at a low-energy flux density of 0.16 mJ/mm² to stimulate complete bone-healing without complications in both in vivo and in vitro experiments in animals^2-5. But, without any preliminary clinical investigation described in the article, the rationale for the choice of the particular regimen in human application—6000 impulses of a high-energy flux density—is dubious.

Nevertheless, the take-home message from this pilot study is that there may be a promising way to avoid performing major surgery on patients with osteonecrosis, and thus also avoid the potential concomitant morbidity and complications, such as infection, perforation of the articular cartilage of the femoral head, or graft migration. The authors are to be congratulated for providing the data needed to calculate sample size and power for future randomized controlled trials. These data will be indispensable in assessing the efficacy of high-energy shock-wave application as a novel management for osteonecrosis of the femoral head.

*The authors did not receive grants or outside funding in support of their research 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. Lieberman JR, Berry DJ, Mont MA, Aaron RK, Callaghan JJ, Rajadhyaksha A, Urbaniak JR. Osteonecrosis of the hip: management in the 21st century. J Bone Joint Surg Am. 2002;84:834-53.
2. Chen YJ, Kuo YR, Yang KD, Wang CJ, Huang HC, Wang FS. Shock wave application enhances pertussis toxin protein-sensitive bone formation of segmental femoral defect in rats. J Bone Miner Res. 2003;18:2169-79.
3. Chen YJ, Kuo YR, Yang KD, Wang CJ, Sheen Chen SM, Huang HC, Yang YJ, Yi-Chih S, Wang FS. Activation of extracellular signal-regulated kinase (ERK) and p38 kinase in shock wave-promoted bone formation of segmental defect in rats. Bone. 2004;34:466-77.
4. Wang CJ, Wang FS, Yang KD, Weng LH, Sun YC, Yang YJ. The effect of shock wave treatment at the tendon-bone interface—an histomorphological and biomechanical study in rabbits. J Orthop Res. 2005;23:274-80.
5. Wang FS, Wang CJ, Chen YJ, Chang PR, Huang YT, Sun YC, Huang HC, Yang YJ, Yang KD. Ras induction of superoxide activates ERK-dependent angiogenic transcription factor HIF-1alpha and VEGF-A expression in shock wave-stimulated osteoblasts. J Biol Chem. 2004;279:10331-7.