The zona orbicularis of the hip joint: anatomical study and review of the literature

Abstract

Objectives: Although it is used as a landmark during various orthopedic procedures of the hip, few studies have focusedon the anatomy of the zona orbicularis. Therefore, the purpose of the present research was to study its morphology toimprove our understanding of its structure and potential variation.Methods: Ten adult cadavers (four males and six females) underwent dissection of the left and right hip joints to observe themorphology and location of the zona orbicularis. A digital caliper was used to measure the length and width of the zona orbicularis.Results: We found a zona orbicularis on all sides and that when present anteriorly, many of the inferior fibers of the zona orbiculariswere confluent with the fibers of the iliofemoral ligament. The mean length for right sides was 35.95 mm and the meanlength for left sides was 43.93 mm. The mean width for right sides was 3.74 mm and the mean width for left sides was 4.4 mm.There were no significant differences between the right and left sides for zona orbicularis length or width. There was no significantassociation between age and sex but a statistically significant correlation (r=0.959) between right and left zona orbicularislengths (p=0.041). However, there was no significant correlation between the right and left zona orbicularis widths (p>0.05). Thefibers of the zona orbicularis were found to be thicker and more visible along the posterior aspect of the femoral neck.Conclusion: Anatomically, the zona orbicularis is a consistent structure of the hip joint capsule. This structure can be seen on highresolution imaging such as MRI and magnetic resonance arthrography. The lengths of this structure may differ between sides,although based on our study, there were no differences between left and right side widths or between sexes or among ages.