These are depression fractures of the femoral head. They are usually associated with acetabular fractures and should therefore be suspected in every patient with an acetabular fracture. Depression fractures are also associated with anterior hip dislocation.
These are fractures which result of high energy trauma. Combined with a depression fracture of the femoral head there might also be an avulsed fragment. A CT-scan should be obtained to determine the morphology of the fractures. The injury to the femoral head is often not evident until visualization of the head at surgery. Because of the technical surgical difficulties in dealing with these fractures they demand a surgeon with special expertise in pelvic and acetabular trauma.
An MRI may add additional information but is not sufficiently sensitive to diagnose articular cartilage lesions.
For depressed fractures, operative treatment may be necessary if deemed possible. This will depend on the amount of depression, the size of the fractured fragment and the technical difficulty in achieving a reduction which can then be maintained.
Vascularization through ligamentum teres
The ligamentum teres arises from the transverse acetabular ligament and the posterior inferior portion of the acetabular fossa and attaches to the femoral head at the fovea capitis. Lesions of the ligamentum teres may be caused by dislocation or subluxation of the hip as well as acetabular fractures. However, rupture may occur simply from a twisting injury in the absence of major trauma.