• Junichi Nakamura, Makoto Kamegaya, Takashi Saisu, Tomonori Kenmoku, Kazuhisa Takahashi, and Yoshitada Harada.
• Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan. njonedr@yahoo.co.jp
• J Pediatr Orthop. 2008 Sep 1;28(6):614-8.

BackgroundHinge abduction is widely accepted as a poor prognostic factor in Legg-Calvé-Perthes disease (LCPD), whereas the exact definition of hinge abduction remains ill defined. The purpose of this diagnostic study was to refine the definition of hinge abduction in LCPD using conventional hip arthrography under general anesthesia.MethodsAmong 350 hips in 332 LCPD patients, we reviewed 92 hips in 90 patients (75 boys and 15 girls) who consecutively underwent arthrography under general anesthesia because of an expected poor prognosis. The mean age at LCPD onset was 8.2 years (range, 4-13 years). With respect to lateral pillar classification, 25 hips were classified as group B, 27 as B/C border, and 40 as C. Subluxation (>or=3-mm difference from unaffected side) was present in 81 (88%) of the 92 hips. The modified Waldenström classification was used for evaluating the radiographic stage of disease at the time of arthrography: 80 hips were classified as fragmentation stage and 12 as reossification stage. Hinge abduction was defined as an increased subluxation index in maximum abduction and/or a positive impingement sign.ResultsUnder this definition, 11% (10 hips) of the study group had hinge abduction. The range of abduction under general anesthesia (40 degrees) was significantly greater than in the awake condition (24 degrees, P < 0.0001).ConclusionsThe subluxation index and the impingement sign proved to be reliable indicators for diagnosing hinge abduction. Conventional arthrography remains useful. General anesthesia provided an analgesic effect and muscle relaxation.Level Of EvidenceLevel II (diagnostic study, development of diagnostic criteria on the basis of consecutive patients).

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