Radiological signs of femoroacetabular impingement are linked to pelvic version in asymptomatic subjects.

ABSTRACT

INTRODUCTION: With the recent interest in hip-spine relationship, the link between femoroacetabular impingement (FAI) and the lumbar-pelvic-femoral complex (LPFC) appears decisive. The objectives of this study were (1) to compare the pelvic version, as well as (2) all the parameters of the LPFC between two populations of healthy subjects, comparing those with radiological signs of FAI to those without and finally, (3) to evaluate the LPFC parameters according to the type of FAI. HYPOTHESIS: Asymptomatic subjects with radiological signs of FAI had superior pelvic anteversion. MATERIALS AND METHOD: This retrospective study was based on a prospective cohort of 118 voluntary asymptomatic patients including 62 men (52.5%) with a mean age of 25.6 years±4.4 (19-39). The following parameters pelvic version (PV), pelvic incidence (PI), lumbar lordosis (LL), sacral slope (SS), hip flexion, intrinsic (IER) and extrinsic (EER) extension reserve were measured using EOS imaging™ in the reference standing position and the lunge position. The radiological signs of FAI (cam, pincer, mixed) were identified on these acquisitions then separated into 2 groups. The first was the group presenting with one or more images of FAI (FAI+) and the second group with no images of FAI (FAI-). RESULTS: There were 143 hips in the FAI+ group compared to 93 hips in the FAI- group. There were 36.4% cams and 45% pincers. With an average of 9.08°±7.81 (-11.0; 27.0) versus 12.33°±8.94 (-5.0; 55.0), the PV was significantly lower (p=0.022) in the FAI+ group compared to the FAI- group. A post-hoc power analysis on the primary outcome (PV) confirmed sufficient power (1-ß=0.809). Compared to the FAI- group, the cam group presented a significantly lower IER and EER (respectively p=0.014 and p=0.047). The comparative analysis between the FAI- and pincer groups found a significant difference in PI (p=0.001), PV (p<0.001), IER (p=0.017) and hip flexion (p<0.001), SS in lunge position (p=0.031) and EER (p=0.039). CONCLUSION: Asymptomatic subjects with radiographic signs of FAI present with weak pelvic version when standing. This pelvic hyper-anteversion is mainly found in the event of a radiological pincer sign. LEVEL OF EVIDENCE III, retrospective comparative study.