We performed THA in the supine position with a G7 OsseoTi cup (Zimmer Biomet, Warsaw, IN) as the trial cup and a femoral rasp for the Wagner cone hip stem (Zimmer Biomet) using an anterolateral approach. We made a skin incision at the anterior border of the gluteus medius muscle and accessed the hip joint through the interval between the tensor fascia lata and gluteus medius. We used a CT-based navigation system (Stryker, Freiburg, Germany) for preoperative planning, implantation, and monitoring of the hip position during examination. We resected the femoral neck based on the position indicated by the navigation system. The acetabulum was then under-reamed by 1 mm and the trial cup was inserted using the press-fit technique. The target cup placement angle was 40° of anatomical inclination. The cup anteversion was adjusted according to the required ACPL. Finally, femoral rasping was performed. The final rasp was used for the examination. Femoral anteversion was matched to the native femoral anteversion using the navigation system. When stem anteversion was changed, it was increased or decreased by 20° with respect to the native femoral anteversion. We used a trial head of 32 mm in diameter, and the neck size was selected so that the postoperative leg-length discrepancy and global offset compared with the contralateral side were almost same in each case according to the navigation system. After THA, a seat-type pressure sensor (I-SCAN, Nitta, Osaka, Japan) for real-time monitoring was placed between the iliopsoas muscle and anterior pelvic wall or anterior cup edge using an ilioinguinal approach (Fig. 1 A,B). We used one sensor seat per sample. The sensor seat for each specimen was calibrated in advance under the same conditions.![]()
Photographs of the seat-type pressure sensor for real-time monitoring of the surface pressure of the iliopsoas muscle (I-SCAN, Nitta, Osaka, Japan). (
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