title: Does femoral offset recover and affect the functional outcome of patients with displaced femoral neck fracture following hemiarthroplasty?
abstract: BACKGROUND
  Restoring preoperative horizontal femoral offset (FO) promised good functional outcome in patients receiving total hip arthroplasty. However, relatively little was known regarding the clinical relevance of restoring the offset in patients with bipolar hemiarthroplasty to treat displaced femoral neck fracture. Therefore, the objective of this study was to evaluate postoperative FO accurately and verify its relation with functional outcome.
  
  
  METHODS
  One hundred elderly patients who received bipolar hemiarthroplasty to treat displaced femoral neck fracture were identified. Preoperative CT scanning of contralateral hip joint and reconstruction of images led to rotation-free FO. By referencing postoperative implant specification and comparing to measured values in Picture Archive and Communication System, rotation-free postoperative FO and the amount of change were acquired. Postoperative Harris Hip Score (HHS) and Modified Barthel Index (MBI) were evaluated to measure functional outcome at 12-month after the surgery. Patients with significant FO change were identified. Multiple regression analysis was conducted to determine if the FO change might independently affect the outcome regardless of confounding factors.
  
  
  RESULTS
  The mean preoperative offset was 37.4±2.5 increased by 12.7±9.6% after the surgery. Only 25.0% of postoperative offset after hemiarthroplasty was changed within ±5% of preoperative offset. A total of 45.0% of postoperative offset changed within ±10% while 77.0% of postoperative offset changed within ±20%. 23% of patients whose FO changed more than 20% showed significantly worse outcome score than the patients whose FO change remained within ±20% of initial value. Mean MBI and HHS were negatively correlated with FO change. After adjusting for confounding factors, significant correlation remained between modification of FO and MBI, but not between FO change and HHS (B=4.576; β=0.235; 95% confidence interval of B: 0.534 to 8.135).
  
  
  CONCLUSIONS
  FO was not properly restored in 23% of subjects receiving bipolar hemiarthroplasty due to femoral neck fracture. FO restoration independently predicted fair MBI after the surgery. Therefore, surgeons should pay attention to restoring FO with meticulous templating.
authors.affiliation: Siheung 21C Hospital, Republic of Korea.
authors.forename: Hyung-Min
authors.initials: HM
authors.lastname: Ji
authors.affiliation: Department of Orthopaedics, Ajou University School of Medicine, Republic of Korea.
authors.forename: Seok-Hyung
authors.initials: SH
authors.lastname: Won
authors.affiliation: Department of Orthopaedics, Ajou University School of Medicine, Republic of Korea.
authors.forename: Jun
authors.initials: J
authors.lastname: Han
authors.affiliation: Department of Orthopaedics, Ajou University School of Medicine, Republic of Korea. Electronic address: yeyeonwon@gmail.com.
authors.forename: Ye-Yeon
authors.initials: YY
authors.lastname: Won
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D005260:Female; D005265:Femoral Neck Fractures / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D062785:Hemiarthroplasty / Q000009:adverse effects / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D016059:Range of Motion, Articular; D020127:Recovery of Function / Q000502:physiology; D056910:Republic of Korea; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: Aged; Femoral neck fractures; Femur; Hemiarthroplasty; Hip joint; Human; Patient outcome