title: Reliability and validity of measuring acetabular component orientation by plain anteroposterior radiographs.
abstract: BACKGROUND
  Inaccurate placement of an acetabular cup can cause impingement, dislocation, and accelerated wear. However, there is no universally agreed-on approach to measuring cup position using plain radiographs.
  
  
  OBJECTIVE
  Our goal was to evaluate the reliability and validity of measuring the orientation of acetabular components on plain anteroposterior (AP) radiographs.
  
  
  METHODS
  We obtained plain AP radiographs and CT scans for 60 patients who underwent 60 primary total hip arthroplasties (THAs). The method devised by Lewinnek et al. was used to measure the orientation of acetabular components on plain AP radiographs, and three-dimensional (3-D) CT scans were used to measure both the radiographic anteversion angle and the inclination angle. Reliability was evaluated by analysis of the agreement between inter- and intraobserver measurements using plain AP radiographs. Measurements on 3-D CT scans were regarded as the reference standard; validity was assessed by comparing radiographic measurements with the CT scans.
  
  
  RESULTS
  Inter- and intraobserver reliability for measuring component orientation on plain AP radiographs was nearly perfect with intraclass correlation coefficients of 0.896 and 0.969 for anteversion and 0.984 and 0.993 for inclination. Measurement of cup inclination angles differed between plain radiographs and CT scans, but the difference was small, and the difference, although statistically significant, probably was not clinically important (2.3° ± 1.8°, p < 0.001). There was no significant difference between the anteversion as measured on CT scan versus that measured on plain radiographs (p = 0.19).
  
  
  CONCLUSIONS
  Measurement of the orientation of acetabular components on plain AP radiographs is reliable and accurate compared with measurement on CT.
authors: Department of Adult Reconstructive Surgery, Beijing Jishuitan Hospital, Fourth Clinical College of Peking University, Beijing, 100035, China.
authors: Ming
authors: M
authors: Lu
authors: Yi-Xin
authors: YX
authors: Zhou
authors: Hui
authors: H
authors: Du
authors: Ji
authors: J
authors: Zhang
authors: Jian
authors: J
authors: Liu
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging* / Q000601:surgery; D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009949:Orientation; D011859:Radiography; D015203:Reproducibility of Results
references: J Bone Joint Surg Br. 1986 May;68(3):409-13
references: 3733807
references: J Orthop Res. 2009 Dec;27(12):1583-8
references: 19544389
references: Arch Orthop Trauma Surg. 2006 Sep;126(7):487-92
references: 16810554
references: J Arthroplasty. 1998 Aug;13(5):530-4
references: 9726318
references: J Arthroplasty. 2010 Aug;25(5):812-9
references: 19553075
references: J Bone Joint Surg Br. 2012 Jan;94(1):32-6
references: 22219244
references: J Bone Joint Surg Br. 1981;63B(4):556-9
references: 7298684
references: J Bone Joint Surg Am. 1982 Dec;64(9):1295-306
references: 7142237
references: J Bone Joint Surg Br. 1970 Feb;52(1):148-59
references: 5436200
references: J Arthroplasty. 1998 Sep;13(6):621-6
references: 9741436
references: Br J Radiol. 1975 Apr;48(568):259-60
references: 1131483
references: Clin Orthop Relat Res. 2009 Sep;467(9):2362-70
references: 19277802
references: J Arthroplasty. 2002 Apr;17(3):359-64
references: 11938515
references: Orthop Clin North Am. 2001 Oct;32(4):569-77, vii
references: 11689370
references: Clin Orthop Relat Res. 2006 Oct;451:134-9
references: 16721351
references: J Bone Joint Surg Br. 1993 Mar;75(2):228-32
references: 8444942
references: J Arthroplasty. 2002 Apr;17(3):282-8
references: 11938502
references: Clin Biomech (Bristol, Avon). 2008 Oct;23(8):1004-11
references: 18541352
references: J Bone Joint Surg Am. 2011 Sep 21;93(18):1712-9
references: 21938375
references: J Bone Joint Surg Am. 2008 Feb;90(2):357-65
references: 18245596
references: Acta Orthop Scand. 2004 Jun;75(3):252-60
references: 15260415
references: Orthopedics. 2010 Oct;33(10 Suppl):48-51
references: 20954630
references: J Bone Joint Surg Am. 1978 Mar;60(2):217-20
references: 641088
references: Clin Orthop Relat Res. 2009 Jan;467(1):32-42
references: 18979147
references: J Arthroplasty. 1995 Jun;10(3):369-72
references: 7673917
references: Eur J Radiol. 2006 May;58(2):294-300
references: 16289687
references: J Arthroplasty. 2004 Apr;19(3):387-90
references: 15067657
references: J Bone Joint Surg Br. 1999 May;81(3):431-5
references: 10872360
references: J Arthroplasty. 2007 Sep;22(6):812-7
references: 17826270
references: Biometrics. 1977 Mar;33(1):159-74
references: 843571