title: What factors predict the failure of curved intertrochanteric varus osteotomy for the osteonecrosis of the femoral head?
abstract: BACKGROUND
  The purpose of this study was to examine the 10-year survivorship and clinical outcome after curved intertrochanteric varus osteotomy (CVO) for the osteonecrosis of the femoral head (ONFH), and to determine what factors predict the failure of this procedure.
  
  
  METHODS
  We retrospectively reviewed 102 consecutive CVOs in 93 patients diagnosed with ONFH. Mean follow-up duration was 10.1 years (3.0-23.2 years). Factors associated with radiographic failure (secondary collapse and/or osteoarthritic change), conversion to total hip arthroplasty (THA) and low Harris Hip Score (HHS), were assessed. The Kaplan-Meier method was used to estimate survival rate.
  
  
  RESULTS
  Radiographic failure occurred in 27 hips (26.5 %), and 11 hips (10.8 %) were converted to THA. The 10-year survival rate was 91.0 % [95 % confidence interval (CI) 83.4-95.2 %] with conversion to THA as the endpoint and 72.4 % (95 % CI 62.3-80.3 %) with radiographic failure as the endpoint. Mean HHS improved from 70.0 preoperatively to 88.1 at the final follow-up (p < 0.001). Multivariate Cox regression analysis showed that postoperative intact ratio <33.3 % [hazard ratio (HR), 11.17; 95 % CI 4.14-30.14] and center-edge (CE) angle <25° (HR 4.91; 95 % CI 1.92-12.55) were independent factors determining radiographic failure. In addition, the multivariate Cox regression analysis showed that postoperative intact ratio <33.3 % (HR 10.65; 95 % CI 2.24-50.53) and CE angle <25° (HR 7.81; 95 % CI 2.17-28.07) were also factors determining conversion to THA. Worse HHSs of <80 were seen in patients with postoperative intact ratio <33.3 % (p < 0.001), CE angle <25° (p < 0.001), and acetabular head index <75 % (p = 0.006).
  
  
  CONCLUSIONS
  Postoperative intact ratio <33.3 % and CE angle <25° were identified as independent factors determining radiographic failure and conversion to THA. Therefore, these factors must be taken into consideration when selecting patients for CVO.
authors: Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan. okuralyly@med.nagoya-u.ac.jp.
authors: Toshiaki
authors: http://orcid.org/0000-0002-6082-2327
authors: T
authors: Okura
authors: Department of Hip and Knee Reconstructive Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan.
authors: Yukiharu
authors: Y
authors: Hasegawa
authors: Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan.
authors: Daigo
authors: D
authors: Morita
authors: Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan.
authors: Yusuke
authors: Y
authors: Osawa
authors: Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan.
authors: Naoki
authors: N
authors: Ishiguro
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000601:surgery*; D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D005271:Femur Head Necrosis / Q000175:diagnosis / Q000453:epidemiology / Q000601:surgery*; D005544:Forecasting; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D010027:Osteotomy / Q000009:adverse effects*; D011184:Postoperative Period; D011859:Radiography; D012189:Retrospective Studies; D015996:Survival Rate / Q000639:trends; D017211:Treatment Failure; D055815:Young Adult
keywords: Acetabular dysplasia; Curved intertrochanteric varus osteotomy; Joint-preserving surgery; Osteonecrosis of the femoral head; Ratio of intact articular surface of the femoral head to the weight-bearing area of the acetabulum