Can we predict which dysplastic hips will require acetabular augmentation during total hip arthroplasty based on pre-operative radiographs?
2017
Aims 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. Patients and 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, Tonnis 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), Tonnis
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 = 0.66 versus 0.88, 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). Conclusion 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 J 2017;99-B:445–50.
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