Copyright © 2007 by The Journal of Bone and Joint Surgery, Inc.

Commentary & Perspective

Commentary & Perspective on
"Periacetabular Osteotomy for the Treatment of Acetabular Dysplasia Associated with Major Aspherical Femoral Head Deformities"
by John C. Clohisy, MD, et al.

Commentary & Perspective by
Michael Leunig, MD*,
Schulthess Clinic, Zürich, Switzerland

Posted July 2007

Residual Legg-Calvé-Perthes disease and Perthes-like deformities in adulthood, as described in the paper by Clohisy et al., present a therapeutic challenge to the orthopaedic surgeon. In their paper, the authors describe midterm follow-up of treatment of twenty-four hips in nine male and eleven female patients with a mean age of 22.7 years with a diagnosis of acetabular dysplasia associated with Perthes-like femoral head configuration.

Hip morphologies in Legg-Calvé-Perthes disease and Perthes-like deformities can be quite complex, spanning a wide range of acetabular and femoral alterations. In addition to the insufficient femoral head coverage that is found in hips with acetabular dysplasia secondary to Legg-Calvé-Perthes disease, acetabular retroversion has recently been identified in 42% of hips in patients with Legg-Calvé-Perthes disease1. Another issue increasing the complexity of care is that, in these hips, good femoral cartilage is present only in the peripheral "nonspherical" zone, while the central cartilage is frequently affected by the femoral head necrosis.

In addition to these intra-articular problems of incongruity that lead to instability or impingement, a short femoral neck is associated with a reduced limb length and a high-riding greater trochanter, potentially leading to extra-articular impingement and/or abductor dysfunction. It is becoming evident that these isolated or combined deformities can result in a complex morphology, meaning that the cause of symptoms frequently cannot be attributed to one deformity. As a consequence, the treatment of one problem alone may be insufficient and may even aggravate coexisting pathologies.

Clohisy et al. present a rational treatment strategy for these complex situations. Clinically, the qualifications for surgical treatment were hip flexion of ≥95° and an absence of advanced osteoarthritis. Pelvic anteroposterior, false profile, and lateral radiographs were made. Although its use was not proposed in this paper, magnetic resonance arthrography has been shown to be of value in assessing the coexistence of dysplasia and impingement2. Acetabular and femoral morphologies in Legg-Calvé-Perthes disease and Perthes-like deformities can lead not only to a lateral labral overload due to dysplasia but also to anterior labral destruction by femoroacetabular impingement3. Because the two conditions require different treatment, optimum preoperative workup of these hips is most helpful.

Periacetabular osteotomy was performed in twenty-four hips and was combined with twenty-one concurrent femoral osseous or soft-tissue procedures in fifteen hips (63%). The potential overlap of coexisting acetabular undercoverage (dysplasia) and femoroacetabular impingement, potentially aggravated after periacetabular reorientation, is clearly discussed. At a mean follow-up of 4.5 years, clinical outcome as measured with use of the modified Harris Hip Score was significantly improved (p < 0.0001) and reported as excellent in the majority of patients. The Tönnis osteoarthritis grade remained stable in the majority of hips.

Despite the promising data, enthusiasm should be tempered slightly. One issue is that these hips may improve but frequently may not attain excellent function, even though the result on the modified Harris Hip Score (which was designed for patients who have undergone hip replacement) is excellent. Periacetabular osteotomy in hips with Legg-Calvé-Perthes disease or Perthes-like deformities is technically demanding, which can be evidenced from the high number of required combined procedures. It is not the osteotomy itself, but rather the correction, that can become quite challenging. The acetabular fragment is not positioned on top of a round sphere as it is in hips with classic dysplasia; instead, it is on top of a mushroom-like deformed femoral head, which frequently limits desired maneuvers. It would have been interesting to know the percentage of preoperative and postoperative retroverted acetabuli that were seen in this study, as this malalignment, if unaddressed, can contribute to impingement. Not mentioned was the need to first address the femoral side in hips that have an appreciable pelvic-trochanteric impingement, as that condition does not permit acetabular reorientation prior to femoral treatment.

Taken together, residual Legg-Calvé-Perthes disease and Perthes-like deformities remain a therapeutic challenge. Careful preoperative clinical and radiographic workup is key to the planning of successful management. If a periacetabular osteotomy is considered, substantial experience with this osteotomy technique will help in coping with the potential difficulties that may be encountered during reorientation of the acetabular fragment. As implemented by the authors in the management of their most recent patients, intraoperative capsulotomy must be performed along with the periacetabular osteotomy4 because improved coverage after reorientation enhances the risk of secondary femoroacetabular impingement. Quite frequently, correction-induced intra-articular and extra-articular impingement may be aggravated after reorientation, thus requiring subsequent femoral treatment. Only the adherence to these principles and the individualization of acetabular and eventual femoral treatment will provide the basis for a successful outcome. The authors should be congratulated for their original presentation of this complex topic.

*The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received 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, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.

References

1. Ezoe M, Naito M, Inoue T. The prevalence of acetabular retroversion among various disorders of the hip. J Bone Joint Surg Am. 2006;88:372-9.
2. Eijer H, Podeszwa DA, Ganz R, Leunig M. Evaluation and treatment of young adults with femoro-acetabular impingement secondary to Perthes' disease. Hip International. 2006;16:273-80.
3. Leunig M, Werlen S, Ungersböck A, Ito K, Ganz R. Evaluation of the acetabular labrum by MR arthrography. J Bone Joint Surg Br. 1997;79:230-4.
4. Myers SR, Eijer H, Ganz R. Anterior femoroacetabular impingement after periacetabular osteotomy. Clin Orthop Relat Res. 1999;363:93-9.