title: No benefit on functional outcomes and dislocation rates by increasing head size to 36 mm in ceramic-on-ceramic total hip arthroplasty.
abstract: BACKGROUND
  Ceramic-on-ceramic (COC) total hip arthroplasty (THA) has gained popularity since improvements in wear characteristics and longevity. Whether large ceramic femoral heads (≥36 mm) have increased postoperative range of motion (ROM) and a lower dislocation rate is not clear. This study aimed to compare functional outcomes and early complications between large-head (≥36 mm) and smaller-head (≤32 mm) COC prostheses with a minimum follow-up of 12 months.
  
  
  METHODS
  A total of 95 consecutive uncemented COC THAs were performed in 90 patients between January 2012 and July 2013. Of these, 49 patients (smaller-head group) received third generation and 41 patients (large-head group) received fourth generation COC prostheses. Harris hip score (HHS), Western Ontario and McMaster Universities Arthritis index (WOMAC), and ROM of the hip pre- and post-operatively were compared, as well as the presence of early complications.
  
  
  RESULTS
  Postoperative HHSs (88.4 vs. 89.3, p = 0.34) and WOMAC scores (12.0 vs. 11.0, p = 0.111) were not different between the groups. Postoperative flexion ROM was lower in the smaller-head group (98.8° vs. 106.1°, p < 0.001), but there were no differences in extension, abduction, adduction, internal rotation, and external rotation. One patient in each group reported a grinding noise. There was one dislocation (1.9%) in the smaller-head group, and none in the large-head group (p = 0.371). No infections or loosening of the components occurred.
  
  
  CONCLUSIONS
  Large-head COC articulation provided better flexion, but functional outcomes and early complications are similar to the smaller-head COC.
authors.affiliation: Department of Orthopaedic Surgery, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Taoyuan, Taiwan.
authors.forename: Yu-Der
authors.initials: YD
authors.lastname: Lu
authors.affiliation: Department of Orthopaedic Surgery, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Taoyuan, Taiwan.
authors.forename: Shih-Hsiang
authors.initials: SH
authors.lastname: Yen
authors.affiliation: Department of Orthopaedic Surgery, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Taoyuan, Taiwan.
authors.forename: Feng-Chih
authors.initials: FC
authors.lastname: Kuo
authors.affiliation: Department of Orthopaedic Surgery, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Taoyuan, Taiwan. Electronic address: wangjw@adm.cgmh.org.tw.
authors.forename: Jun-Wen
authors.initials: JW
authors.lastname: Wang
authors.affiliation: Department of Orthopaedic Surgery, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Taoyuan, Taiwan.
authors.forename: Ching-Jen
authors.initials: CJ
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects; D002516:Ceramics; D005260:Female; D000072039:Fracture Dislocation / Q000453:epidemiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular
keywords: Ceramic-on-ceramic bearing; Early complications; Functional outcome; Large-diameter femoral head; Total hip arthroplasty