高リスク患者における後方進入人工股関節全置換術後の脱臼リスク低減における外旋筋温存の有効性：プロペンシティスコアマッチング比較研究

Although multiple studies have examined the efficacy of muscle-sparing techniques in reducing dislocation after posterior approach THA, their findings are limited by small sample sizes and short follow-up durations, and to our knowledge, none have specifically evaluated outcomes in high-risk patients. This study compared the overall and 90-day dislocation risks of the previously described external rotator preservation (ERP) and standard posterior approach THA in high-risk patients.

We retrospectively reviewed patients who underwent THA between January 2008 and December 2022 at three tertiary centers, including those who had osteonecrosis of the femoral head (ONFH), inflammatory arthritis (IA), or a history of lumbar spinal fusion (LSF). Patients who underwent the ERP approach were identified from medical records and matched 1:1 to controls (standard posterior approach) by age, sex, body mass index, American Society of Anesthesiologists score, year of surgery, and surgical indication, yielding 501 patients per group. Binary logistic regressions were used to compare overall and 90-day dislocation risk. Kaplan-Meier analysis evaluated revision due to dislocation and all-cause revision. Surgical complications, the Harris Hip Score (HHS), and postoperative radiographic parameters were compared. Mean follow-up was 10.7 years.

The ERP group showed lower overall (odds ratio [OR], 0.25; P < 0.001) and 90-day dislocation risks (OR, 0.20; P = 0.002). Subgroup analyses revealed reduced dislocation risks in the ONFH and IA patients, with no difference in the LSF subgroup. The estimated 10-year survivorship free from both revision for dislocation (P = 0.302) and any revision (P = 0.739) was similar. Other complications, the latest HHS, and radiographic parameters were comparable.

The ERP approach for THA demonstrated lower overall and 90-day dislocation rates compared to the standard posterior approach in patients at high risk of dislocation without compromising long-term outcomes. The external rotator preservation may serve as an effective option for performing posterior approach THA in ONFH and IA patients.