Capsular ligaments of the hip: anatomic, histologic, and positional study in cadaveric specimens with MR arthrography

Purpose: To demonstrate the anatomy of the capsular ligaments of the hip by using magnetic resonance (MR) arthrography.

Materials and methods: Institutional policies were followed regarding cadaver use. MR arthrographic images of 10 fresh human cadaveric hips were obtained by using a positioning device to arrange the hip joint in different controlled positions. MR appearances of the capsular structures were noted and correlated with those seen on anatomic slices and dissections. Two readers working in consensus graded the visibility of these structures. Tissue samples were collected for histologic analysis. An MR positional study was performed to evaluate the length of these capsular ligaments and the subjective classification of their appearance as either taut or lax in extension, flexion, abduction, adduction, and internal and external rotation.

Results: The hip capsule inserts proximally and continuously to the acetabular rim periosteum. Distally, it has a firm anterior insertion at the femoral intertrochanteric line and no posterior osseous insertion. The inferior band of the iliofemoral ligament was best evaluated in the sagittal, axial, and axial oblique planes, and it serves a restrictive function in extension; the superior band of the iliofemoral ligament was best evaluated in the coronal and axial oblique planes, and it serves a restrictive function in external rotation; the ischiofemoral ligament was best evaluated in the axial and axial oblique planes, and it serves a restrictive role in internal rotation; the pubofemoral ligament was best evaluated in the sagittal plane, and it serves a restrictive function in abduction; and the zona orbicularis could be evaluated equally well in any imaging plane.

Conclusion: MR arthrography enables visualization of the capsular ligaments of the hip.