A 56-yr-old white man presented with complaints of right groin pain. He demonstrated an antalgic gait pattern, a loss of right hip internal rotation, and a positive Patrick's sign. The neurologic examination was normal except for loss of the left Achilles reflex associated with a previous lumbar laminectomy for a disc herniation; however, straight leg raising was unrestricted and pain free. Plain radiographs revealed low-grade osteoarthritis of the right hip with an os acetabuli. Magnetic resonance imaging demonstrated a tear of the hip labrum with an acetabular labral cyst (Fig. 1).
The anterior labrum of the hip joint is a rim of avascular fibrocartilaginous tissue that surrounds the femoral head lying within the acetabulum. In this anatomical relationship, the labrum serves two functions. By sealing fluid within the hip joint, it limits displacement of the synovial fluid, thereby reducing soft tissue loading, especially at heel impact during initial weight bearing. It also limits joint range of motion at the extremes of motion. Disruption of the labrum may destabilize the hip joint and thereby accelerate degenerative changes.1
Although anterior hip and groin pain may be due to a number of neuromusculoskeletal and systemic pathologies, anterior labral tears among others are more common than previously suspected. In one report, 22% of athletes with groin pain and 85% of all patients with mechanical hip pain were identified as having a labral tear. Postmortem studies have also demonstrated that in the elderly (averaging 78 yrs), 93% had at least one labral lesion. Anteriorly, the labra, although wider, are also thinner, predisposing them to tearing as induced by a pivoting, twisting maneuver.2
Other skeletal risk factors may include the natural aging process and other disorders that decrease the clearance between the femur and the acetabulum, that is, hip dysplasia, a decrease in femoral head-neck offset, and a reduction in acetabular and femoral anteversion.3 Conservative treatment of each includes reduced weight bearing, nonsteroidal antiinflammatory drugs, and, with limited success, physical therapy. Excision and debridement is the most common surgical intervention. When hip osteoarthritis is coexistent, the prognosis for a full recovery is less favorable.
Cystic lesions of the hip joint are also well documented. Based on their anatomic relationship with the hip joint itself, they are defined as either acetabular labral cysts, that is, those that communicate directly with the hip joint and those that do not, or paralabral cysts.
Although in this case there was no clinical evidence of neurologic compromise, acetabular labral cysts have been reported to produce sciatic and femoral as well as obturator neuropathy.4 Although the preferred initial treatment of these cysts is aspiration, the rate of recurrence remains high. Definitive treatment, therefore, is surgical repair of the torn labrum.
1. Lewis CL, Sahrmann SA: Acetabular labral tears. Phys Ther
2. McCarthy J, Noble P, Aluisio FA, et al: Anatomy, pathologic features and treatment of acetabular labral tears. Clin Orthrop
3. Ganz R, Parvizi J, Beck M, et al: Femoroacetabular impingement. Clin Orthrop
4. Yukata K, Arai K, Yoshizumi Y, et al: Obturator neuropathy caused by an acetabular labral cyst: MRI findings. AJR Am J Roentgenol