Abstract
Purpose: The purpose of this study was to asses the usefulness of the obturator externus tendon (OE) as landmark and the correlation of the femoral stem position in relation to the OE and its effect on postoperative leg length difference (LLD) after direct anterior approach-total hip replacement (DAA-THR). Patients and Methods: A retrospective radiographic analysis of 85 patients undergoing THR was performed. Postoperative leg length was determined using the center of femoral rotation to tear drop line and lesser trochanter method. Relative distance of the femoral component to the insertion of the OE was determined (OE-SH). The intraclass correlation coefficient (ICC) was performed for intra- and inter-reliability ratings. Regression analysis was performed. Discriminant analysis was performed to define a possible critical cutoff of OE-SH with regard to defining groups based on LLD. Risk analysis with regard to OE-SH ><6 mm and difference in distance between teardrop and lesser trochanter before and after implantation of THR (ΔTDLT) ><5 or 10 mm was performed. Results: Seventeen cases (21%) had lengthening (ΔTDLT) >5 mm and 7 cases (8%) had ΔTDLT >10 mm, with a mean ΔTDLT of 1.61 ± 4.92 mm SD. ICC values for intra- and interobserver reliability were rated as excellent. Regression analysis showed a clear correlation between ΔTDLT and OE-SH (ΔTDLT = −1.076 + 0.60176*OE-SH). Risk analysis showed a relative risk (RR) of 11.20 (confidence interval [CI] 3.52–35.60, power 1) for 5 mm ΔTDLT when OE-SH >6 mm and a RR 14.4 (CI 1.83–113.54, power 0.86) for 10 mm ΔTDLT when OE-SH >6 mm. Conclusion: OE-SH is a reliable measurement and a reliable predictor of LLD after THR. The radiographic cutoffs of OE-SH correlate well with the average size of the OE tendon, further underlining its clinical value in DAA THR. Intraoperative significant OE-SH warrants a critical review and correlation to preoperative planning.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
