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, 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 = 0.66 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.
A. G. Marsh: Devised the templating technique to calculate the TC: FC surface area ratio, Conceived idea of the study, Helped design study, Data collection, Data analysis, Wrote and revised the manuscript.
A. Nisar: Devised the templating technique to calculate the TC: FC surface area ratio, Conceived idea of the study, Helped design study, Data collection, Data analysis , Wrote and revised the manuscript.
M. E. Refai: Data collection, Data analysis, Wrote and revised the manuscript.
S. Patil: Helped design study, Data analysis, Wrote and revised the manuscript, Guarantor for the study.
R. M. D. Meek: Helped design study, Data analysis, Wrote and revised the manuscript, Guarantor for the study.
We also thank H. Murray and F. Nicol (Arthroplasty Specialist Nurses) for their help with data collection related to this study.
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
This article was primary edited by A. C. Ross.
Supplementary material. Graphs showing the angles/ratio for non-augmented and augmented hips can be found alongside the online version of this article at www.bjj.boneandjoint.org.uk
- Received March 2, 2016.
- Accepted December 13, 2016.
- ©2017 The British Editorial Society of Bone & Joint Surgery