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Legg-Calvé-Perthes DiseasePart I: Classification of Radiographs with Use of the Modified Lateral Pillar and Stulberg Classifications
John A. Herring, MD1; Hui Taek Kim, MD2; Richard Browne, PhD1
1 Texas Scottish Rite Hospital for Children, 2222 Welborn Street, Dallas, TX 75129. E-mail address for J.A. Herring: tony.herring@tsrh.org
2 Department of Orthopaedic Surgery, Pusan National University Hospital, 1Ga-10, Ami-Dong, Seo-Gu, Pusan 602-739, Korea
View Disclosures and Other Information
In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from the Texas Scottish Rite Hospital Research Fund and the Pediatric Orthopaedic Society of North America Huene Award. None of the authors 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, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Investigation performed at the Texas Scottish Rite Hospital for Children, Dallas, Texas

The Journal of Bone and Joint Surgery, Incorporated
J Bone Joint Surg Am, 2004 Oct 01;86(10):2103-2120
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Abstract

Background: Accurate and reliable radiographic classifications of the relative severity and outcome of Legg-Calvé-Perthes disease are essential in the study of that disease. As part of a prospective multicenter study*, we sought to define more clearly the lateral pillar classification of severity and the Stulberg classification of outcome; we sought especially to define the borderlines between classification groups.

Methods: We performed interobserver and intraobserver trials of the lateral pillar and Stulberg classifications using sets of twenty radiographs chosen from a prospective study of 345 hips. To establish reliable definitions of the lateral pillar classification, we added a new, intermediate group termed the B/C border group, which includes femoral heads with a thin or poorly ossified lateral pillar and those with a loss of exactly 50% of the original height of the lateral pillar. The resulting classification consists of four groups: A, B, B/C border, and C. In our application of the classification system of Stulberg et al., we defined a class-II femoral head as round and fitting within 2 mm of a circle on both anteroposterior and frog-leg lateral radiographs. We defined a Stulberg class-III femoral head as out of round by more than 2 mm on either view and a Stulberg class-IV femoral head as one with at least 1 cm of flattening of the weight-bearing articular surface. To assess interobserver and intraobserver agreement, we performed two trials of each classification with six orthopaedic surgeons reviewing twenty radiographs or pairs of radiographs.

Results: In the first trial of the lateral pillar classification, there was 81% agreement per radiograph and the average weighted kappa was 0.71. In the second trial, there was 85% agreement per radiograph and the weighted kappa averaged 0.79. Intraobserver reliability testing showed a 77% match between Trials 1 and 2, an average weighted kappa of 0.81, and an average generalizability coefficient of 0.91. In Trial 1 of the Stulberg classification, there was 91% agreement per radiograph and an average weighted kappa of 0.82. In Trial 2, there was 92% agreement per radiograph and an average weighted kappa of 0.82. Intraobserver reliability testing showed an 89% match between Trials 1 and 2, an average weighted kappa value of 0.88, and an average generalizability coefficient of 0.92.

Conclusions: The interobserver and intraobserver trials of these classifications produced kappa values and generalizability coefficients in the excellent range. The modified lateral pillar classification and the redefined Stulberg classification are sufficiently reliable and accurate for use in studies of Legg-Calvé-Perthes disease.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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