Abstract. Background. Femoroacetabular impingement (FAI) has been extensively investigated and is strongly associated with athletic participation. The aim of this systematic review is to assess: the prevalence of cam-type FAI across various sports, whether kinematic variation between sports influences hip morphology, and whether performance level, duration and frequency of participation or other factors influence hip morphology in a sporting population. Methods. A systematic search of Embase, PubMed and the Cochrane Library was undertaken following PRISMA guidelines. The study was registered on the PROSPERO database (CRD4202018001). Prospective and retrospective case series, case reports and review articles published after 1999 were screened and those which met the inclusion criteria decided a priori were included for analysis. Results. The literature search identified 58 relevant articles involving 5,683 participants. Forty-nine articles described a higher prevalence of FAI across various ‘hip-heavy’ sports, including soccer, basketball, baseball, ice hockey, skiing, golf and ballet. In studies including non-athlete controls, a greater prevalence of FAI was reported in 66.7% of studies (n=8/12). The highest alpha angle was identified at the 1 o'clock position (n=9/9) in football, skiing, golf, ice hockey and basketball. Maximal alpha angle was found to be located in a more lateral position in goalkeepers versus positional players in ice hockey (1 o'clock vs 1.45 o'clock). A positive correlation was also identified between the alpha angle and both age and activity level (n=5/8 and n=2/3, respectively) and also between prevalence of FAI and both age and activity level (n=2/2 and n=4/5), respectively. Conclusions. Hip-heavy sports show an increased prevalence of FAI, with specific sporting activities influencing hip morphology. Both a longer duration and increased level of training also resulted in an increased prevalence of FAI

Cam-type femoroacetabular impingement is caused by bone excess on the femoral neck abutting the acetabular rim. This can cause cartilage and labral damage due to increased contact pressure as the cam moves into the acetabulum. However, the damage mechanism and the influence of individual mechanical factors (such as sliding distance) are poorly understood. The aim of this study was to identify the cam sliding distance during impingement for different activities in the hip joint. Motion data for 12 different motion activities from 18 subjects, were applied to a hip shape model (selected as most likely to cause damage, anteriorly positioned with a maximum alpha angle of 80°). The model comprised of a pointwise representation of the acetabular rim and points on the femoral head and neck where the shape deviated from a sphere (software:Matlab). The movement of each femoral point was tracked in 3D while an activity motion was applied, and impingement recorded when overlap between a cam point and the acetabular rim occurred. Sliding distance was recorded during impingement for each relevant femoral point. Angular sliding distances varied for different activities. The highest mean (±SD) sliding distance was for leg-crossing (42.62±17.96mm) and lowest the trailing hip in golf swing (2.17±1.11mm). The high standard deviation in the leg crossing sliding distances, indicates subjects may perform this activity in a different manner. This study quantified sliding distance during cam impingement for different activities. This is an important parameter for determining how much the hip moves during activities that may cause damage and will provide information for future experimental studies

Patients undergoing hip resurfacing arthroplasty (HRA) is typically reserved for highly active patients. Patient Reported Outcome Measures (PROMs) such as the Oxford Hip Score (OHS) are reported to have ceiling effects, which may limit physicians' ability to measure health gain in these patients. The Metabolic Equivalent of Task (MET) index is a validated compendium assigning energy expenditure to a wide range of activities; for example, a slow walk expends 2.9 kcal/kg/hour, golf expends 4.0 kcal/kg/hour, while moderate lacrosse typically expends 8.1 kcal/kg/hour. We hypothesized that for patients with high OHS (47–48) after HRA, the MET index could better discriminate between high-performing individuals. We evaluated 97 consecutive HRA patients performed by a single surgeon. They prospectively completed an online Oxford Hip Score. They also listed three activities which they had performed independently in the preceding 2 weeks with a Likert-scale slider denoting intensity of effort. Matched data-sets were obtained from 51 patients, from which 23 had OHS of 47–48 at 6-months. Their activity with the highest MET index was selected for analysis. The 23 patients' OHS improved from 29.3 ± 7.0 preoperatively to 47.6 ± 0.5 after 6-months, while their MET indices improved from 8.5 ± 3.7 to 12.9 ± 3.5 kcal/kg/hr. The activities performed by these high-performance individuals ranged from the lowest, pilates (8.05 kcal/kg/hour), to highest, running at 22km/hr (23 kcal/kg/hour). 45% of patients undergoing HRA in this cohort had OHS of 47 and 48 at 6-months after surgery. Unlike the OHS, the MET index described variation in physical activity in these high-performance individuals, and did so on an objective measurable scale