Copyright © 2006 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective
Commentary & Perspective by
Michael Leunig, MD*,
Department of Orthopaedic Surgery, Schulthess Clinic, Zürich, Switzerland
The best joint is the natural joint. Thus, mechanically correctable deformities, such as developmental dysplasia of the hip, are ideally corrected before appreciable damage has occurred at the opposing cartilaginous surfaces1,2.
Unfortunately, many patients do not experience symptoms, including pain, before appreciable damage to the labrum and/or cartilage complex has occurred. In addition, the imaging assessment of the hip, even with use of magnetic resonance imaging and magnetic resonance imaging arthrography, generally does not accurately reflect the health of the acetabular cartilage in the critical stages before radiologic changes become visible. The curved surfaces of the femoral head and acetabulum make analysis with magnetic resonance imaging difficult. Moreover, the coaptation of joint surfaces hinders appreciation of so-called cleavage lesions of the articular cartilage. Surgeons now have a better understanding of the importance of labral lesions (tears, degeneration) as harbingers of articular cartilage damage, and, as a result, the identification of these lesions on magnetic resonance imaging will now alert surgeons to investigate the status of the articular cartilage at an earlier stage.
To overcome the current limitations in direct imaging of diseased cartilage, delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC), mainly for use in the knee, has been proposed as a sensitive and specific measure of cartilage glycosaminoglycans, providing previously unavailable information on prognostically and therapeutically important structural alterations of the cartilage. But it was not until recently that Kim et al. explored the possibility of using dGEMRIC to assess early osteoarthritis of the hip3. That initial paper is important, since it demonstrates that, even for the hip, in which cartilage is difficult to assess by standard imaging, a promising technique appears to be available.
The present study by Cunningham et al. was designed to identify radiographic, clinical, and magnetic resonance imaging parameters that predict failure after pelvic osteotomy. Studying forty-seven patients who had undergone a periacetabular osteotomy for hip dysplasia, these authors reported a high correlation among postoperative pain reduction, radiographic signs of osteoarthritis, joint subluxation, and dGEMRIC index. Based on their data, the delayed dGEMRIC index appears to be quite promising for identifying poor candidates for a pelvic osteotomy.
Advocates of dGEMRIC propose that the biochemical information provided by this technique may augment radiography by improving the differentiation of the disease status within a given radiographic grade, especially for the early stages of osteoarthritis. In a subluxed hip, the radiographically visible joint-space loss might not always reflect the actual cartilage loss because the head tends to migrate out of the joint, which also can contribute to a decreased joint space. Therefore, it can be anticipated that dGEMRIC will show even better correlation with joint-space width in well-centered hips that have mechanical abnormalities such as femoroacetabular impingement. Open and arthroscopic treatment of intracapsular pathologic processes in these hips will additionally provide direct information on the integrity of the labrum and/or cartilage in these hips.
Surgeons and patients alike will benefit from a reliable estimate of the expectations of joint-preserving procedures, and dGEMRIC may prove to be an important clinical instrument for providing this information. The surgeon will better appreciate the process of osteoarthrosis and be able to make a more informed recommendation, and the patient will make a more informed decision. I consider the research on this topic to be quite timely, and I hope we will get more information from this group and others in the near future.
*The author did not receive grants or outside funding in support of his research for or preparation of this manuscript. He 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 author is affiliated or associated.
References
1. Siebenrock KA, Scholl E, Lottenbach M, Ganz R. Bernese periacetabular osteotomy. Clin Orthop Relat Res. 1999;363:9-20.
2. Trousdale RT, Ekkernkamp A, Ganz R, Wallrichs SL. Periacetabular and intertrochanteric osteotomy for the treatment of osteoarthrosis in dysplastic hips. J Bone Joint Surg Am. 1995;77:73-85.
3. Kim YJ, Jaramillo D, Millis MB, Gray ML, Burstein D. Assessment of early osteoarthritis in hip dysplasia with delayed gadolinium-enhanced magnetic resonance imaging of cartilage. J Bone Joint Surg Am. 2003;85:1987-92.
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