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

Abstract

PURPOSE: 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. METHODS:

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. RESULTS: 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). CONCLUSIONS: 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.