Capsule
Copyright 2009
Matthew Diltz MD
Definition
The hip has a thick articular capsule that functions to provide additional stability. The capsule surrounds the hip circumferentially attaching to the margin of the acetabulum 5 to 6 mm beyond the glenoid labrum posterior and superior. Anteriorly the capsule coalesces with the outer margin of labrum. The capsule also encompasses the general neck. This becomes an important consideration when dealing with infections of the proximal femur. Retinacula are longitudinal bands of the capsule that travel along the femoral neck. Surrounding the acetabulum it consists of both circumferential as well as longitudinal fibers. The zona orbicularis are the circular fibers that make up the majority of the posterior and inferior portion of the capsule. They form a sling around the neck of femur. Anteriorly the fibers blend with the iliofemoral ligament and attached to the anterior inferior iliac spine.
In femoral neck fractures the intracapsular hematoma may elevate pressure enough to occlude venous drainage. The increased intracapsular pressure may increase the rate of osteonecrosis of the femoral head due to occlusion of local arterials. Extension and internal rotation of the hip also increases the intracapsular pressure and should be avoided in femoral neck fractures. Some surgeons recommend and anterior capsulotomy in order to decrease the risk of ischemia to the femoral head.
References
Grey’s anatomy