The adult hip: an anatomic study. Part II: the soft-tissue landmarks.

A comprehensive anatomic, pathologic, and radiographic study was undertaken to define reliable soft-tissue landmarks about the hip. Methodology included an analysis of 300 "normal" adult hip radiographs, tissue maceration, cadaveric intra-articular injection studies and review of selected clinical cases. Results, when applied to clinical situations, indicate: (a) The iliopsoas and "capsular" fat planes are poor indicators of small to moderate amounts of intra-articular fluid in the adult. (b) The "capsular" fat plane is not associated with the joint capsule, but in fact is a fat plane between two muscle bundles anterior to the articulation. (c) Distinct soft-tissue planes are available for dissemination of fluid from the hip joint. These include the iliopsoas bursa, which may distend in association with articular disease, and the fat plane of the obturator externus muscle.