Abstract
Objective: The aim of this study was to assess the accuracy and reproducibility of aligning the cup trial with the transverse acetabular ligament (TAL) in total hip arthroplasty (THA) by using computer-assisted navigation and to determine whether the TAL was useful as a landmark in THA.
Methods: Between January 2011 and August 2012, 101 patients (108 hips) underwent primary THA using the posterolateral approach at our hospital. We measured the anatomical TAL anteversion intraoperatively by aligning the inferomedial rim of the cup trial with the TAL using computer-assisted navigation.
Results: The TAL was identified in 81.4% of cases (88 of 108 hips). Intra-observer reliability was high for both the expert surgeon (intraclass correlation coefficient [ICC(1.1)]=0.872) and the non-expert surgeons (ICC(1.1)=0.889). Inter-observer reliability was moderate (ICC(2.1)=0.614). The mean difference in the anatomical TAL anteversion measured by two surgeons was 6.7°±5.1° (range, 0.3°-21.3°). The mean anatomical TAL anteversion was 22.5°±8.5° (range, 7.7°-54.7°).
Conclusion: Some reports have suggested that the TAL can aid in positioning the cup in THA. In this study, we could identify the TAL in more than 80% of cases, and this ligament could be used to determine the anteversion of the cup in THA. Intra-observer reliability was high, and each surgeon was able to align the cup according to the TAL anteversion target. However, inter-observer reliability was only moderate. This is because the TAL is a short ligament with significant thickness, and the methods for aligning the cup trial with the TAL may differ among surgeons. TAL retroversion was not observed in any case. Therefore, the TAL was useful as a landmark for preventing the positioning of the cup in retroversion. However, in some cases with an excessive posterior pelvic tilt, the TAL anteversion may have been excessive and not necessarily optimal.
