title: Changes in Intra-pelvic Obliquity Angle 0-2 Years After Total Hip Arthroplasty and Its Effects on Leg Length Discrepancy: A Retrospective Study.
abstract: BACKGROUND
  Total hip arthroplasty (THA) is one of the most effective treatments for phase III and IV hip arthrosis. Lower limb length balancing is one of the determining factors of a successful surgery, particularly in patients with developmental dysplasia of the hip (DDH). The purpose of this study was to evaluate the postoperative change in intra-pelvic obliquity (intra-PO) angle in the coronal plane and its effects on leg length discrepancy (LLD) within 2 years.
  
  
  METHODS
  A total of 78 patients (70 females, 8 males) were enrolled in this study. All patients were suffering from DDH with varying degrees of LLD. Pelvic plain radiographs were collected before and after the operation. The intra-PO angles were measured 0, 0.5, 1 and 2 years after THA. At the same time, postoperative LLD was measured with blocking test.
  
  
  RESULTS
  PO changed significantly in the first year after THA surgery (0 year vs. 0.5 year, P < 0.01; 0.5 year vs. 1 year, P < 0.01), and the changing value of intra-PO angle (ΔPO) slowed down substantially during the first 2 years after THA (0.5 year vs. 0.5-1 year, P < 0.01; 0.5-1 year vs. 1-2 years, P < 0.01). With the change in intra-PO angle, LLD also got narrow within the 1st year (0 year vs. 0.5 year, P < 0.01; 0.5 year vs. 1 year, P < 0.01). Elderly patients had a smaller intra-PO angle reduction (Group A vs. Group B, P = 0.01; Group B vs. Group C, P < 0.01).
  
  
  CONCLUSIONS
  Intra-PO angle and LLD gap narrowed with time after THA surgery. In particular, elderly patients had smaller change in intra-PO angle.
authors.forename: Yin
authors.initials: Y
authors.lastname: Zhang
authors.forename: Tao
authors.initials: T
authors.lastname: Cheng
authors.affiliation: Department of Orthopaedics, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China.
authors.forename: Xian-Long
authors.initials: XL
authors.lastname: Zhang
mesh_terms: D000367:Age Factors; D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D005260:Female; D006621:Hip Joint / Q000601:surgery; D006801:Humans; D007870:Leg Length Inequality / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies