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.

Stress fractures are highly prevalent in ballet dancers and lead to notable time loss from dancing. Nutritional status, body composition, bone mineral density, and rate of increase in activity are among the components that influence risk for stress fractures. Proper evaluation and management of stress fractures is essential including a review of the causative factors involved in each stress injury. The purpose of this article was to summarize current evidence for risk factors involved in dancers' stress fractures to optimize prevention and treatment. Identified associated factors include low energy availability, low bone mineral density, low fat body composition, abnormal lower extremity biomechanics, genetic factors, and high training loads. Ballet dancers participate in rigorous training and conditioning to achieve seemingly effortless, powerful, aesthetic artistic movements. Caring for these performing artists requires attention to their unique injuries and the remarkable volume of activity undertaken in classes, rehearsals, and performances. Stress-related bone injuries are challenging for both dancers and professional companies because treatment often includes prolonged rest from participation. An understanding of the multifactorial, multisystem nature of these injuries is required to properly diagnose, treat, and prevent the spectrum of these injuries. This review summarizes the current best evidence in dance medicine epidemiology, risk factors, and evaluation and provides a stress fracture management and prevention protocol used in elite ballet. Epidemiology of Stress-related Bone Injury in BalletStress fractures may occur secondary to one of the three mechanisms: (1) abnormal stress on normal bone, (2) normal stress on abnormal bone, or (3) abnormal stress on abnormal bone. Ballet dancers may be especially susceptible to the latter. 1 Recent evidence has described a greater incidence of stress injuries in younger, female dancers. [2][3][4][5] In a systematic review by Smith et al, 2 amateur male and female dancers sustained 0.99 and 1.09 injuries for every 1,000 dance hours, respectively, whereas professional male and female dancers sustained a total of 1.06 and 1.46 injuries, respectively, during the same period. In professional female dancers, 64% of injuries were related to