title: Can we predict which dysplastic hips will require acetabular augmentation during total hip arthroplasty based on pre-operative radiographs?
abstract: OBJECTIVE
  The purpose of this study was to evaluate whether an innovative templating technique could predict the need for acetabular augmentation during primary total hip arthroplasty for patients with dysplastic hips.
  
  
  METHODS
  We developed a simple templating technique to estimate acetabular component coverage at total hip arthroplasty, the True Cup: False Cup (TC:FC) ratio. We reviewed all patients with dysplastic hips who underwent primary total hip arthroplasty between 2005 and 2012. Traditional radiological methods of assessing the degree of acetabular dysplasia (Sharp's angle, Tönnis angle, centre-edge angle) as well as the TC:FC ratio were measured from the pre-operative radiographs. A comparison of augmented and non-augmented hips was undertaken to determine any difference in pre-operative radiological indices between the two cohorts. The intra- and inter-observer reliability for all radiological indices used in the study were also calculated.
  
  
  RESULTS
  Of the 128 cases reviewed, 33 (26%) needed acetabular augmentation. We found no difference in the median Sharp's angle (p = 0.10), Tönnis angle (p = 0.28), or centre-edge angle (p = 0.07) between the two groups. A lower TC:FC ratio was observed in the augmented group compared with the non-augmented group (median = 0.66versus0.88, p < 0.001). Intra-observer reliability was found to be high for all radiological indices analysed (interclass correlation coefficient (ICC) > 0.7). However, inter-observer reliability was more variable and was only high for the TC: FC ratio (ICC > 0.7).
  
  
  CONCLUSIONS
  The TC: FC ratio gives an accurate estimate of acetabular component coverage. It can help predict which dysplastic hips are likely to need acetabular augmentation at primary total hip arthroplasty. It has high intra- and inter-observer reliability. Cite this article:Bone Joint J2017;99-B:445-50.
authors.affiliation: Southern General Hospital, Glasgow, G51 4TF, Scotland, UK.
authors.forename: A G
authors.initials: AG
authors.lastname: Marsh
authors.affiliation: Southern General Hospital, Glasgow, G51 4TF, Scotland, UK.
authors.forename: A
authors.initials: A
authors.lastname: Nisar
authors.affiliation: Southern General Hospital, Glasgow, G51 4TF, Scotland, UK.
authors.forename: M
authors.initials: M
authors.lastname: El Refai
authors.affiliation: Southern General Hospital, Glasgow, G51 4TF, Scotland, UK.
authors.forename: S
authors.initials: S
authors.lastname: Patil
authors.affiliation: University of Glasgow, University Avenue, Glasgow, G12 8QQ, Scotland, UK.
authors.forename: R M D
authors.initials: RM
authors.lastname: Meek
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000601:surgery*; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation / Q000379:methods*; D006617:Hip Dislocation / Q000150:complications* / Q000000981:diagnostic imaging; D006622:Hip Prosthesis; D006801:Humans; D015588:Observer Variation; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000209:etiology* / Q000601:surgery*; D011300:Preoperative Care / Q000379:methods; D011474:Prosthesis Design; D011859:Radiography; D015203:Reproducibility of Results
keywords: Acetabular augment; Hip dysplasia; Pre-operative radiograph; Templating; Total hip arthoplasty