Abstract
Introduction: Iliocapsularis is a small muscle that covers the anterior hip joint capsule. It has been implicated in hip dysfunction yet little is known about its detailed anatomy and it remains unclear whether it is separate to, or part of, iliacus. The aim of this study was to examine the morphology of iliocapsularis using macro- and microscopic anatomical approaches.
Materials and Methods: Twelve specimens (six embalmed cadavers, three females; mean age 70 ± 11.3 years) were examined using fascicular dissection. Footprint areas of attachment were quantified by 3D scanning technol-ogy. The nature of the capsular insertion was examined histologically and fiber type composition was determined using immunohistochemistry and stereology.
Results: No distinct fascial plane existed between iliocapsularis and iliacus. Mean total PCSA and fascicular length of iliocapsularis were 0.7 ± 0.2 cm2 and 10.4 ± 1.0 cm, respectively. Its capsular attachment (2.9 ± 1.1 cm2) was approximately three times larger than its bony footprints (proximal 1.2 ± 0.5 cm2; distal 1.3 ± 0.7 cm2), and 50% of the total length of the deep fascicles attached either directly to the capsule or via a layer of loose connective tissue. The innervation pattern of iliocapsularis was variable. The proportion of Type I to II fibers was similar within iliocapsularis (approximately 50% of each) and no different to iliacus.
Conclusion: Although iliocapsularis has distinct attachment sites, it may be best defined as a part of iliacus given the lack of a separating fascial plane and similarities in fascicle length and fibre type.