title: The influence of obesity on primary total hip arthroplasty outcomes: A meta-analysis of prospective cohort studies.
abstract: BACKGROUND
  Whether or not, obesity negatively influencing the outcomes of primary total hip arthroplasty (THA) remains a controversial issue. Though observational studies focused on this topic, the reported conclusions remain inconsistent. Therefore, we performed a meta-analysis of prospective cohort studies to evaluate if obesity negatively affects: (1) the overall complication rate (incidence of dislocation, deep infection and osteolysis); (2) functional outcome; (3) operative time and stay duration in hospital for the primary THA.
  
  
  METHODS
  We searched the PubMed, Embase, Web of Science, and the Cochrane Library until July 2014 to identify the eligible prospective studies. The Newcastle Ottawa Scale (NOS) was used for quality assessment of the included studies. We extracted and pooled the data. As for continuous data, mean difference (MD) was calculated; for dichotomous variables, we calculated a weighted relative risk (RR) with its 95% confidence interval. Heterogeneity was evaluated using I(2) statistics. P ≤ 0.05 was thought to be significant.
  
  
  RESULTS
  Fifteen studies were eligible for data extraction, which involved 11,271 total hip arthroplasties. The pooled data of complication rate demonstrated that obese patients suffered higher rates of complication (RR: 1.68, 95% CI 1.23 to 2.30, P = 0.0004), dislocation (RR: 2.08, 95% CI 1.54 to 2.81, P < 0.0001) and deep infection (RR: 2.92, 95% CI 0.74 to 11.49, P = 0.13). For the functional result, obese patients acquired relatively lower Harris Hip Score than non-obese patients (MD: -2.75, 95% CI -4.77 to -0.6), no difference was found regarding Oxford Hip Score (MD: -0.46, 95% CI -2.18 to 1.26, P = 0.60). Obese patients compared to non-obese patients showed an increase duration of operation (MD: 10.67, 95% CI 3.00 to 18.35, P = 0.006). However, no significant difference was found in the length of stay in hospital between obese and non-obese patients (MD: -0.16, 95% CI -0.34 to 0.02, P = 0.08).
  
  
  CONCLUSIONS
  This meta-analysis of prospective cohort studies demonstrates that obesity negatively influences the overall complication rate, dislocation rate, functional outcome and operative time of primary total hip arthroplasty.
authors.affiliation: Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Yishan Road 600, 200233 Shanghai, China.
authors.forename: W
authors.initials: W
authors.lastname: Liu
authors.affiliation: Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Yishan Road 600, 200233 Shanghai, China.
authors.forename: T
authors.initials: T
authors.lastname: Wahafu
authors.affiliation: Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Yishan Road 600, 200233 Shanghai, China.
authors.forename: M
authors.initials: M
authors.lastname: Cheng
authors.affiliation: Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Yishan Road 600, 200233 Shanghai, China.
authors.forename: T
authors.initials: T
authors.lastname: Cheng
authors.affiliation: Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Yishan Road 600, 200233 Shanghai, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Yishan Road 600, 200233 Shanghai, China. Electronic address: zhangxianlong2013s@163.com.
authors.forename: X
authors.initials: X
authors.lastname: Zhang
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D006617:Hip Dislocation / Q000209:etiology; D006621:Hip Joint / Q000503:physiopathology; D006801:Humans; D007239:Infections / Q000209:etiology; D007902:Length of Stay; D009765:Obesity / Q000150:complications*; D061646:Operative Time; D010014:Osteolysis / Q000209:etiology; D011446:Prospective Studies; D020127:Recovery of Function
keywords: Hip arthroplasty; Meta-analysis; Obesity; Outcome; Prospective studies