title: Clinico-radiological factors affecting the joint space narrowing after transtrochanteric anterior rotational osteotomy for osteonecrosis of the femoral head.
abstract: OBJECTIVE
  The purpose of this study was to investigate the factors that affect the joint space narrowing after transtrochanteric anterior rotational osteotomy (ARO) for osteonecrosis of the femoral head (ONFH).
  
  
  METHODS
  We reviewed 39 cases (43 hips) of ONFH in patients who underwent ARO between 2000 and 2004. Their mean age was 42 years (23-61) at the time of surgery. The mean follow-up period was 7.3 years (3-10). The following clinical and radiological factors were investigated: the preoperative stage, localization and extent of the necrotic lesion, and the postoperative intact ratio (transposed intact articular surface of the femoral head to the weight-bearing surface of the acetabulum). The 43 hips were divided into two groups: a joint space narrowing (JSN) group and a non-joint space narrowing (non-JSN) group.
  
  
  RESULTS
  Thirty-seven hips (86 %) were categorized as non-JSN and six (14 %) as having JSN. The preoperative Japanese Orthopaedic Association score was significantly higher in the non-JSN group than in the JSN group (P = 0.01). In the non-JSN group, the rate of early stage disease was significantly higher than in the JSN group (P = 0.03). The postoperative intact ratio was significantly higher in the non-JSN group than in the JSN group (P = 0.002). A multivariate analysis revealed that the postoperative intact ratio was an independent predictor of the progression of joint space narrowing after ARO, and the cutoff point was 39.2 %.
  
  
  CONCLUSIONS
  The results of this study suggest that the postoperative intact ratio is one of factors determining the progression of joint space narrowing after ARO and that an approximately 40 % or higher postoperative intact ratio is recommended to prevent joint space narrowing.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Garida
authors.initials: G
authors.lastname: Zhao
authors.forename: Takuaki
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ikemura
authors.forename: Goro
authors.initials: G
authors.lastname: Motomura
authors.forename: Kenyu
authors.initials: K
authors.lastname: Iwasaki
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Yamaguchi
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Nakashima
authors.forename: Taro
authors.initials: T
authors.lastname: Mawatari
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Iwamoto
mesh_terms: D000328:Adult; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D016009:Chi-Square Distribution; D005260:Female; D005271:Femur Head Necrosis / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D005500:Follow-Up Studies; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010027:Osteotomy / Q000379:methods*; D012372:ROC Curve; D011859:Radiography; D012189:Retrospective Studies; D016896:Treatment Outcome