title: Radiographic analysis of the restoration of hip joint center following open reduction and internal fixation of acetabular fractures: a retrospective cohort study.
abstract: BACKGROUND
  Unfavorable reduction is considered one of the key factors leading to joint degeneration and compromised clinical outcome in acetabular fracture patients. Besides the columns, walls, and superior dome, the postoperative position of hip joint center (HJC), which is reported to affect hip biomechanics, should be considered during the assessment of quality of reduction. We aimed to evaluate the radiographic restoration of HJC in acetabular fractures treated with open reduction and internal fixation.
  
  
  METHODS
  Patients with a displaced acetabular fracture that received open reduction and internal fixation in the authors' institution during the past five years were identified from the trauma database. The horizontal and vertical shifts of HJC were measured in the standard anteroposterior view radiographs taken postoperatively. The radiographic quality of fracture reduction was graded according to Matta's criteria. The relationships between the shift of HJC and the other variables were evaluated.
  
  
  RESULTS
  Totally 127 patients with 56 elementary and 71 associated-type acetabular fractures were included, wherein the majority showed a medial (89.0%) and proximal (93.7%) shift of HJC postoperatively. An average of 2.8 mm horizontal and 2.2 mm vertical shift of HJC were observed, which correlated significantly with the quality of fracture reduction (P < 0.001 for both). The horizontal shift of HJC correlated with the fracture type (P = 0.022).
  
  
  CONCLUSIONS
  The restoration of HJC correlates with the quality of reduction in acetabular fractures following open reduction and internal fixation. Further studies are required to address the effects of HJC shift on the biomechanical changes and clinical outcomes of hip joint, especially in poorly reduced acetabular fractures.
authors.forename: Hong-fei
authors.initials: HF
authors.lastname: Shi
authors.forename: Jin
authors.initials: J
authors.lastname: Xiong
authors.affiliation: Department of Orthopaedics, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, No, 321 Zhongshan Road, Nanjing, China. dr.chenyixin@gmail.com.
authors.forename: Yi-xin
authors.initials: YX
authors.lastname: Chen
authors.forename: Jun-Fei
authors.initials: JF
authors.lastname: Wang
authors.forename: Yin-he
authors.initials: YH
authors.lastname: Wang
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000293:injuries / Q000503:physiopathology / Q000601:surgery*; D001696:Biomechanical Phenomena; D005593:Fracture Fixation, Internal; D017102:Fracture Healing; D006620:Hip Fractures / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D011237:Predictive Value of Tests; D011859:Radiography; D016059:Range of Motion, Articular; D020127:Recovery of Function; D012189:Retrospective Studies; D016896:Treatment Outcome