FEMOROACETABULAR IMPINGEMENT/HIP LABRAL TEARS
The recognition and diagnosis of hip pain in the non-arthritic state has been an evolving process over the past 15 years. Patient complaints often include insidious onset of deep nonpalpable pain. This may be described as deep in the groin or, less commonly, in the buttock area. Activity-related hip pain is the norm, because this is believed to be a condition of the active population. The most common offending activities include but are not limited to running and sitting for long periods of time, with the common mechanism being hip flexion past 90 degrees with some rotation. Patients will often commonly complain of laterally based pain as well, making a true diagnosis difficult to make.
The causes of hip labral tears are believed to be a subtle abnormality of the bony anatomy of the hip joint, resulting in the so-called impingement, which leads to tearing of the labrum and possibly cartilage defects. The bony changes may exist on the femoral or acetabular in origin. Femoral (cam) impingement is the result of the loss of femoral head-neck offset, resulting in early contact of the cam with the labrum. Acetabular (pincer) impingement is the result of acetabular overcoverage. This may result from acetabular retroversion, a deep acetabular socket (coxa profunda).
A general hip examination is performed as discussed previously, with focus on hip range of motion and hip abduction strength (Trendelenburg test), as well as a gait examination. Palpation of the lateral hip should help guide the cause of pain. Palpation must take place over the greater trochanter, gluteus medius tendon, and piriformis, because they all may contribute to this syndrome. The Ober test is also performed to determine if the iliotibial band is contracted.
Tests specific to hip impingement and labral tears include the anterior impingement test (also called the McCarthy test/FADIR [Flexion, ADduction, Internal Rotation]. This test re-creates the pinching of the anterior/anterosuperior labrum. Also, FABER (Flexion, ABduction, External Rotation), a dynamic labral stress test, and a posterior impingement test may be performed. Straight-leg raising strength and iliopsoas isolation strength (hip flexion in upright seated position) should also be used to help distinguish a possible hip flexor pathologic process.
Standard radiographs include anteroposterior pelvis and shoot-through lateral views of the affected hip. These should be examined for joint space narrowing to help determine if osteoarthritis may be pain generator. To evaluate the hip labrum, MRI is the modality of choice. Adding an arthrogram to the study will help increase the sensitivity of the study. Also included in the arthrogram can be local anesthetic, so the injection may serve diagnostic purposes as well.
Differential diagnosis includes hip flexor strain, piriformis syndrome, hernia/sports hernia, adductor strain, osteoarthritis of the hip, avascular necrosis, lumbar radiculopathy, or trochanteric bursitis.
Appropriate diagnosis is essential to the treatment of hip impingement and labral tears. If a labral tear is suspected, this should be confirmed with small field-of-view MRI of the affected hip with appropriate radiographs. If a labral tear is identified without any significant hip osteoarthrosis, treatment is often surgical. The mainstay of nonoperative management is activity modification and NSAIDs. Physical therapy may be employed for muscle weakness/tendinopathy. However, pushing more motion is not recommended because labral tears are believed to be a consequence of bony impingement, and, theoretically, forcing motion means continual engagement of the offending lesion.
Once nonoperative modalities have been exhausted, or if activity modification is not an option, surgical intervention is chosen. Two options exist for the treatment of labral tears with hip impingement: open surgical dislocation or hip arthroscopy. Both treat any labral or articular cartilage pathologic processes in addition to the bony impinging lesion.