RADIOLOGICAL SIGNS OF FEMOROACETABULAR IMPINGEMENT AND GLOBAL ACETABULAR RETROVERSION IN SYMPTOMATIC PATIENTS

Femoroacetabular Impingement (FAI) occurs secondary to morphologic abnormalities of the hip joint resulting in abnormal bony contact during functional hip range of motion. It is hypothesized this predisposes the hip joint surface to experience increased stress, load, and increased risk of early osteoarthritis. Longitudinal studies have observed that a significant number of patients with radiographic signs of FAI went on to develop end-stage osteoarthritis or require total hip arthroplasty. There are studies investigating the presence of radiographic features of FAI in asymptomatic patients. However, there is less published literature investigating the presence of radiographic features of FAI in symptomatic patients. The primary objective of this retrospective review is to evaluate the presence of radiographic features of FAI in symptomatic patients and its relationship with global acetabular retroversion (AR) measured on Computed Topography (CT) scan Institutional research ethics board approval was obtained prior to study commencement. A retrospective cohort study was conducted using clinical practice data of a single academic surgeon. Patients who underwent hip arthroscopy for symptomatic FAI between August 2017- August 2024 were screened. Patients with AR, defined as >/= 5 degrees relative to normal published parameters at the 1 o'clock, 2 o'clock and 3 o'clock positions were included. Standard pelvic radiographs were analyzed for radiographic signs of FAI: crossover sign (including crossover percentage), ischial spine sign and empty posterior wall sign. Statistical analysis was performed to determine the sensitivity and specificity of each sign and if there is a relationship between the number of radiographic signs observed on standard pelvic radiographs and acetabular retroversion (AR) measured on CT. Continuous variables were compared using univariate analysis of variance (ANOVA) and linear regression analyses. A total of 200 patients were reviewed and 156 patients were included for analysis. Patients were categorized into globally retroverted (n=48), regionally retroverted (n=64) and normal version (n=44). The presence of 2 radiographic signs in globally retroverted patients were significant for greater acetabular retroversion at the 1- and 2 o'clock positions (p > 0.05), but not at the 3 o'clock position (p = 0.059). A positive crossover sign in isolation was most sensitive at detecting acetabular retroversion at 91.6%. A positive crossover sign percentage greater than 30% was most specific at 86.7%. The presence of three radiographic signs with a crossover percentage greater than 30% increased specificity to 93.3%. Linear regression analysis observed a correlation between crossover percentage and degree of acetabular retroversion at the 1 and 3 o'clock positions (p < 0.05). In this limited retrospective review of patients with symptomatic FAI, radiographic signs of FAI can detect global AR with significant sensitivity and specificity. Our results are comparable to previously described studies investigating their utility in detecting focal retroversion at the 3 o'clock position. Crossover percentage was observed to have a positive association with the extent of AR and may be valuable as a predictive tool. The results of this retrospective review may provide guidance in when to pursue CT imaging in select cases where AR is suspected to inform operative management.