title: Sagging rope sign in achondroplasia is different from Perthes disease.
abstract: The "sagging rope" sign is a radiopaque line seen on radiographs of hips with Perthes disease. The main purpose of this study was to determine the incidence, cause, and importance of this sign in achondroplasia and to reveal how it differs from in Perthes disease. Serial radiograms, along with two- and three-dimensional CT images were studied in 42 patients with achondroplasia. The sign was observed bilaterally in all patients. Evaluation of CT images revealed spherical heads with the presence of circumferential overhang in all hips. This circumferential overhang seen on three-dimensional CT images corresponded to the sagging rope sign on plain radiographs. The presence of the sagging rope sign in bilateral hips is a characteristic feature of achondroplasia. It usually appears before epiphyseal closure. Its cause, incidence, and nature differ from in Perthes disease, and its presence does not carry a negative prognosis in achondroplasia.
authors.affiliation: Department of Orthopaedic Surgery, Kyungpook National University Hospital, Daegu, Korea.
authors.forename: Chang-Wug
authors.initials: CW
authors.lastname: Oh
authors.forename: Viraj Uttamrao
authors.initials: VU
authors.lastname: Shingade
authors.forename: Hae-Ryong
authors.initials: HR
authors.lastname: Song
authors.forename: Seung-Woo
authors.initials: SW
authors.lastname: Suh
authors.forename: Jun-Seok
authors.initials: JS
authors.lastname: Hong
authors.forename: Seok-Hyun
authors.initials: SH
authors.lastname: Lee
mesh_terms: D000130:Achondroplasia / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006615:Hip / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D007873:Legg-Calve-Perthes Disease / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D008297:Male; D014057:Tomography, X-Ray Computed