Abstract
Introduction
Acetabular and spino-pelvic (SP) morphological parameters are important determinants of hip joint dynamics. This study aims to determine whether acetabular and SP morphological differences exist between hips with and without cam morphology and between symptomatic and asymptomatic hips with cam morphology.
Patients/Materials & Methods
A prospective cohort of 67 patients/hips was studied. Hips were either asymptomatic with no cam (Controls, n=18), symptomatic with cam (n=26) or asymptomatic with cam (n=23). CT-based quantitative assessments of femoral, acetabular, pelvic and spino-pelvic parameters were performed. Measurements were compared between controls and those with a cam deformity, as well as between the 3 groups. Morphological parameters that were independent predictors of a symptomatic Cam were determined using a regression analysis.
Results
Hips with cam deformity had slightly smaller subtended angles superior-anteriorly (87° Vs 84°, p=0.04) and greater pelvic incidence (53° Vs 48°, p=0.003) compared to controls. Symptomatic Cams had greater acetabular version (p<0.01), greater subtended angles superiorly and superior-posteriorly (p=0.01), higher pelvic incidence (p=0.02), greater alpha angles and lower femoral neck-shaft angles compared to asymptomatic cams (p<0.01) and controls (p<0.01). The four predictors of symptomatic cam included antero-superior alpha angle, femoral neck-shaft angle, acetabular depth and pelvic incidence.
Discussion
Symptomatic hips had a greater amount of supero-posterior coverage; which would be the contact area between a radial cam and the acetabulum, when the hip is flexed to 90°. Furthermore, individuals with symptomatic cam morphology had greater PI. Acetabular- and SP parameters should be part of the radiological assessment of femoro-acetabular impingement.
Conclusion
Because of the association between a high PI and an increased risk of hip OA (also shown to be increased with c-FAI), the relationship between the PI and FAI should be taken into consideration in prospective longitudinal studies looking at factors influencing the formation of cam morphology as well as those at risk of developing symptoms and degenerative changes.
