Effect of a modular neck hip prosthesis on anteversion and hip rotation in total hip arthroplasty for developmental dysplasia of the hip

概要

〔目的(Purpose)〕
The purposes of the present study were to：1)quantify the pre- and postoperative AA and hip rotation in patients who underwent THA with a straight neck or a retroverted neck, and 2) clarify the effect of a retroverted neck on the postoperative changes in AA and hip rotation.

〔方法ならびに成績(Methods/Results)〕
Patients who underwent THA using a straight neck (ST group) or a 15° retroverted neck (RV group) in a version changeable dual modular system (Mainstay stem, Kyocera, Kyoto, Japan) were retrospectively reviewed. After matching for age, body mass index, and surgical approach, 44 patients were included in each group. The AA and hip rotation (femoral rotational angle： FRA) were measured on CT images acquired preoperatively and 1 month after THA, and were compared between the groups. The mean ± standard deviation preoperative AA of the ST group (26.1±10. 7°) was significantly smaller than that of the RV group (44. 2±7.8°) (p<0. 001).In contrast, the postoperative AA did not significantly differ between the groups (ST group: 27. 5±9.8°, RV group: 25.1±8.3。,p=0. 406), The change in FRA after THA did not significantly differ between the groups (ST group: -3. 8±9. 9。,RV group : -3. 5±9.1。,p=0. 841),

〔総括(Conclusion)〕 .
We confirmed that a small change in AA was observed after THA with a straight neck, while a 15° retroverted neck effectively reduced AA. The magnitude of the change in the FRA after THA was similar between the ST group (-3, 8°) and the RV group (-3. 5°). As the change in the FRA after THA remained similar across the groups, the impact of biomechanical change in the knee is expected to be similar.