Loder et al. first pointed out the importance of physeal instability in predicting the risk of osteonecrosis after acute slipped capital femoral epiphysis, noting a 47% rate of osteonecrosis in their series1. Others have emphasized the importance of reduction of the slip, urgent treatment, and capsular decompression in decreasing the rate of osteonecrosis2,3. In 2009, Parsch et al. reported a 4.7% rate of osteonecrosis after open reduction of sixty-four hips with evidence of instability4.
Since the efficacy of the modified Dunn procedure was reported by Ziebarth et al. and echoed by Slongo et al.5,6, substantial interest has been generated in the ability of this procedure to restore anatomy, in an attempt to prevent later problems associated with impingement, and to further reduce the rate of osteonecrosis. Indeed, some have even advocated surgical hip dislocation by means of the modified Dunn procedure as the new gold standard for treatment of unstable slipped capital femoral epiphysis.
The current multicenter study by Sankar et al. presents the initial experience of a group of surgeons who have been trained by those who introduced this procedure in North America. This group performs surgical hip dislocation electively as part of their practice and had been trained specifically in performing the modified Dunn procedure. The authors report a 26% osteonecrosis rate in twenty-seven patients and a 41% overall rate of substantial complications. Each of the surgeons reported at least one case of osteonecrosis. The remaining patients did well, with excellent correction of the deformity and restoration of function.
This study has many of the drawbacks of previous reports: the study is retrospective in nature, details of how the procedure was performed vary slightly, and the patient numbers are small. The disappointing results could potentially be attributed to the learning curve of the surgeons as this report represents their initial efforts to perform the modified Dunn procedure. This is, however, also one of the real strengths of the study, providing insight into the ability of these surgeons to translate this procedure from a few isolated, specialized centers to other institutions.
The authors are to be commended for publishing this study. As surgeons, it is much more rewarding to publish the results of studies that demonstrate our surgical prowess in successfully performing complex procedures that relieve pain and disability. Often, however, the more valuable study is one that points out the problems, pitfalls, and complications that are an inevitable part of any surgical intervention. Surgical hip dislocation and the modified Dunn procedure are extremely complex, and this study points out the difficulty involved with attempting to transfer the skills of a small, highly skilled, and specialized group of surgeons to the next generation—or indeed, with attempting to generalize the excellent results of those who routinely perform these procedures to a wider group of less specialized surgeons. It may be that surgical hip dislocation provides the best ultimate outcome for patients with an unstable slipped capital epiphysis if it is performed by those who are highly skilled in this difficult procedure. Unfortunately, the number of such centers that could potentially be supported in North America is small, and it is unreasonable to expect that all patients with an unstable slipped capital femoral epiphysis could be treated at one of only a few highly specialized centers.
It may be that the best treatment at less specialized centers is a procedure involving either urgent open reduction or closed reduction with capsular decompression. Although this sounds like a double standard, it may be impractical for enough surgeons to perform enough surgical hip dislocations to maintain the expertise necessary to obtain the excellent outcomes reported by Ziebarth et al. and Slongo et al.5,6. The modified Dunn procedure for unstable slipped capital femoral epiphysis may be best performed by surgeons with highly specialized training, above and beyond that obtained during a simple fellowship. To quote Sankar et al.: “our findings warrant attention by surgeons who are considering their first procedure and by those who are eager to promote new standards in the treatment of unstable slipped capital femoral epiphyses.” The orthopaedic community should heed this warning.