Purpose To perform a systematic review of biomechanical and clinical studies to determine whether the iliopsoas is a femoral head stabilizer. Methods A systematic review was conducted using Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Inclusion criteria were any human clinical (Levels I-IV evidence) or laboratory studies that investigated the role of the iliopsoas as a stabilizer of the hip. Exclusion criteria included studies that investigated patients undergoing spine surgery or those with a total hip arthroplasty or hip hemiarthroplasty. Study methodologic quality for clinical-outcomes studies were analyzed using the Modified Coleman Methodology Score. Because of the heterogeneity in the participants and interventions, no quantitative assimilative meta-analysis was performed. Results Eight articles were analyzed (3 biomechanical [35 cadavers and 18 healthy subjects]; 5 clinical outcomes studies [537 subjects, 207 arthroscopic iliopsoas tenotomies]). Two in vivo biomechanical studies identified the iliopsoas as an anterior hip stabilizer. One cadaveric study identified the iliopsoas as a femoral head stabilizer at 0 o -15 o of hip flexion. Two clinical studies demonstrated the role of the iliopsoas as a dynamic hip stabilizer, particularly in patients with increased femoral version (greater than 15˚-25˚). Two studies reported cases of atraumatic anterior hip dislocations after arthroscopic iliopsoas tenotomies. Conclusions Evidence from biomechanical and clinical studies may suggest that the iliopsoas is a dynamic anterior femoral head stabilizer. Level of Evidence Level IV, systematic review of Level III and IV plus biomechanical studies.

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a b s t r a c tWe encountered a patient who experienced incomplete atrioventricular (A-V) dissociation and isorhythmic A-V dissociation during general anesthesia with desflurane and remifentanil. A 38-year-old man was scheduled to undergo extraction of both the upper and the right lower impacted wisdom teeth under general anesthesia. After anesthesia induction, we maintained anesthesia with desflurane and remifentanil. After 15 min, incomplete A-V dissociation was observed on electrocardiography (ECG). After atropine sulfate 0.3 mg was administered intravenously, isorhythmic A-V dissociation was observed. Atropine sulfate 0.2 mg was administered intravenously, and we observed normal ECG findings. Subsequently, no abnormal ECG findings were observed.