Herniation pits as a radiographic indicator of pincer-type femoroacetabular impingement in symptomatic patients

Abstract

The role of herniation pits as a radiographic indicator is still debated. This case-control study was to determine (1) the prevalence and sizes of herniation pits and (2) the relationship between herniation pits and femoral and acetabular bony morphology consistent with femoroacetabular impingement. This comparative study was performed on 151 patients (151 hips; median patient age 46 years; range 16-73 years) with mechanical symptoms, who underwent multi-detector computed tomography (MDCT) arthrography (the symptomatic group), and an age-, gender-, site (left or right)-, and time (at diagnosis)-matched group of control patients that underwent multi-detector computed tomography due to an ureter stone (the asymptomatic group). Two orthopaedic surgeons reviewed images to evaluate the prevalence, sizes of herniation pits, and relationship with morphological abnormality. The prevalences of herniation pits in symptomatic and asymptomatic groups were 23.8 % (36/151) and 3.3 % (5/151), respectively (OR 9.14, 95 % CI 3.47-24.30; p < 0.001). Herniation pits were found to be significantly associated with pincer-type abnormality (p = 0.034), especially central acetabular retroversion (p < 0.001). This study shows that the prevalence of herniation pits is higher in symptomatic patients with femoroacetabular impingement, and herniation pits are associated with central acetabular retroversion. Furthermore, herniation pits were also found to be a useful predictor of pincer-type femoroacetabular impingement.