Sequential Intraoperative Evaluation of Rotational Stability of Cementless Stem in Total Hip Arthroplasty: A Broach-Based Study.

In cementless total hip arthroplasty, the rotational stability of the stem is generally confirmed in a one-time manual evaluation by the surgeon. This study was performed to evaluate the sequential intraoperative changes in rotational stability using a torque wrench. Primary total hip arthroplasty was performed on 52 consecutive hips using a single wedge stem design. Intraoperative evaluation of rotational stability was uniformly performed using a torque wrench. Evaluations were performed immediately after broach insertion and immediately before the final insertion of the stem (after placement of the acetabular cup). Immediately after the insertion of the broach, rotational stability was checked and confirmed to be fully stabilized using a torque wrench in all cases, and the stability was maintained in 17 of 52 (33%) hips immediately before the final insertion of the stem. Among the hips showing instability, 11 of 35 (31%) broaches were upsized, while the remaining 24 hips achieved stabilization through deeper insertion of the broach. In conclusion, the rotational stability achieved immediately after the insertion of the broach was not necessarily maintained during surgery, indicating that rotational stability may need to be checked at multiple time points intraoperatively.

Femoral nerve status during the anterolateral approach for total hip arthroplasty: Motor-evoked potential analysis and an influencing factor.

BACKGROUND: Femoral nerve palsy is an uncommon but serious complication during the anterolateral approach for total hip arthroplasty. One of the reported reasons for femoral nerve palsy is retractor-induced intraoperative damage after retractor placement on the anterior wall of the acetabulum. The present study aimed to clarify the femoral nerve status during anterolateral approach total hip arthroplasty using motor-evoked potential analysis and to identify risk factors influencing the nerve status. METHODS: From June 2019 to September 2020, 32 hips in 31 patients underwent primary total hip arthroplasty via the anterolateral approach. The integrity of the femoral nerve was tested by the motor-evoked potential at three time points: preoperatively as a control (first period), immediately after retractor placement on the anterior wall of the acetabulum (second period), and after the procedure (third period). In the second period, the hips were divided into the following two groups: a <50% femoral nerve amplitude group and a ≥50% group. The iliopsoas muscle volume was evaluated by measuring the muscle cross-sectional area on preoperative computed tomography images, and compared between the two groups. RESULTS: The mean amplitude of the femoral nerve was significantly reduced from 100% in the first period to 35% in the second period (p < 0.01), but then significantly recovered to 54% in the third period (p < 0.01). In 26 (81%) hips, the femoral nerve amplitude was <50% in the second period. The muscle cross-sectional area of the iliopsoas muscle in the <50% group was significantly smaller than that in the ≥50% group (p < 0.05). CONCLUSIONS: The mean amplitude of the femoral nerve was significantly reduced to 35% in the second period, and the iliopsoas muscle volume was considered to influence this femoral nerve status.

Utility of anterior wall of greater trochanter in predicting femoral anteversion angle: a three-dimensional computed tomography-based simulation study.

BACKGROUND: The femoral anteversion angle is an important factor in performing surgery in the proximal part of the femur. Predicting the femoral anteversion angle based on the morphology of the proximal femur is clinically useful. The purpose of this study was to investigate whether an anatomical landmark can be used to predict the femoral anteversion angle intraoperatively. MATERIALS AND METHODS: We analysed CT data obtained from 100 hips in 69 patients with osteonecrosis of the femoral head with no more than 2 mm collapse and no evidence of osteoarthritic changes. The measured variables were the femoral anteversion angle, the femoral neck-shaft angle, and the AW angle (defined as the angle between the femoral shaft axis and the tangential line of the anterior wall of the greater trochanter). The correlations between variables were also investigated. Multiple regression analysis by the forced input method was performed for the degree of femoral anteversion angle, using sex and the AW angle as explanatory variables. RESULTS: On CT, the mean femoral anteversion angle was 14.8° ± 10.8°, the mean AW angle was 17.5° ± 8.0°, and the mean femoral neck-shaft angle was 127.3° ± 5.4°. There was a positive correlation between the femoral anteversion angle and the AW angle. The approximation equations based on the multiple regression analysis were as follows: male femoral anteversion angle = AW angle × 0.7 - 0.7 and female femoral anteversion angle = AW angle × 0.7 + 4.3. CONCLUSIONS: Femoral anteversion angle can be predicted based on the AW angle of the greater trochanter.

Leg Length Change After Curved Periacetabular Osteotomy and Its Impact on the Clinical Outcomes.

BACKGROUND: Curved periacetabular osteotomy (CPO) is one of the periacetabular osteotomies for the treatment of acetabular dysplasia. Several complications have been described after CPO, however, there have been no reports on the leg length change (LLC). This study aimed to investigate the LLC after CPO and its impact on the clinical outcomes. METHODS: This study was a retrospective review of 70 consecutive hips in 67 patients with symptomatic acetabular dysplasia who underwent CPO between March 2016 and April 2019. Preoperative and postoperative leg lengths were measured using anteroposterior radiographs, and the clinical outcomes were evaluated based on the Harris hip score (HHS) and Medical Outcomes Survey 36-item Short Form Health Survey (SF-36). RESULTS: The mean LLC (and standard deviation) after CPO was -0.08 ± 3.10 mm. The mean HHS significantly improved from 73.5 points to 91.9 points (P < .001). The physical component and role component scores of SF-36 significantly improved from 35.1 to 46.1 (P < .001) and from 39.5 to 47.0 (P < .001), respectively. No significant differences were found between the preoperative and postoperative mental component scores of SF-36. In addition, among 70 hips, 35 hips exhibited leg length elongation (0 to plus 6.82 mm) after CPO, whereas 35 hips exhibited leg length shortening (0 to minus 6.23 mm). No significant differences were found in HHS and SF-36 between the leg elongation group and leg shortening group. CONCLUSION: The mean LLC after CPO was -0.08 ± 3.10 mm, and this change does not affect the postoperative clinical outcomes.