A hip labral tear is a tear of the fibrocartilaginous labrum that attaches to the periphery of the acetabulum. The acetabular labrum is a horseshoe-shaped fibrocartilaginous structure that attaches to the peripheral rim of the acetabulum, contacts the articular surface of the femoral head, and blends inferiorly with the transverse acetabular ligament. The labrum plays a major biomechanical role in hip joint stabilization and function. It increases the effective depth of the acetabulum, increasing static stability; it contributes to hydrostatic pressurization of the intra-articular space, joint lubrication, and load distribution; and it has proprioceptive and nociceptive nerve function [1].

The labrum can be divided into two distinct zones: the well-vascularized extra-articular side consisting of dense connective tissue; and the intra-articular side, which is largely avascular [2]. The chondrolabral junction is not uniform and has lower biomechanical strength at its anterosuperior acetabular attachment, which contributes to the higher incidence of labral tears in this area [3,4].

Hip injuries account for 3.1% to 8.4% of sports injuries, and labral tears are present in 22% to 55% of athletes with hip complaints [3,4]. Labral tears may be due to hip instability, iliopsoas impingement, trauma, and osteoarthritis. Many labral tears are associated with a condition called femoroacetabular impingement (FAI) [5,6]. FAI is characterized by abnormal contact between the femoral head-neck junction and the acetabular rim caused by abnormal bone morphology. Ganz and colleagues [7] described two types of FAI: pincer and cam. Pincer-type FAI is due to excessive femoral head coverage by the acetabulum (Fig. 56.1), whereas cam-type FAI results from a decrease in the femoral head-neck offset distance (Fig. 56.1). Pincer-type FAI typically occurs in middle-aged women; cam-type FAI is more common in men in their fourth decade. Most cases of FAI have components of both pincer and cam types.

f56-01-9781455775774 — FIGURE 56.1 A, Normal hip joint, which allows unrestricted hip motion. B, Pincer-type femoroacetabular impingement due to excessive coverage of the femoral head by the acetabulum. C, Cam-type femoroacetabular impingement secondary to a decreased femoral head-neck offset distance. (Modified from Tannast M, Siebenrock KA, Anderson SE. Femoroacetabular impingement: radiographic diagnosis—what the radiologist should know. AJR Am J Roentgenol 2007;188:1540-1552.)

Whereas labral tears associated with both types of FAI tend to occur in the anterosuperior region, the bone abnormalities in cam-type and pincer-type FAI cause different patterns of labral tears. In pincer-type impingement, repeated contact between the femoral neck and the prominent anterior aspect of the acetabular rim leads to labral degeneration, tears, intrasubstance ganglion formation, and, occasionally, labral ossification. In cam-type impingement, abnormal contact between the femoral head-neck junction and the acetabulum produces an outside-in abrasion of the acetabular cartilage and delamination between the acetabular cartilage and the adjacent labrum and subchondral bone [2]. The labral tears tend to occur on the articular rather than on the capsular surface. Although the bone patterns of FAI may differ, more commonly the osseous dysmorphism is a combined pattern.

Symptoms

Patients with labral tears complain of anterior groin pain made worse by long periods of standing, sitting, or walking. The pain can also be referred to the gluteal area or the trochanteric region. The onset of pain is usually insidious, with the patient often unable to recall a specific inciting event [2]. On occasion, the labral tear is due to trauma. Mechanical symptoms of clicking, locking, and instability are highly variable and not always indicative of intra-articular disease. A thorough history is critical, including inquiry about childhood diseases such as hip dysplasia, Legg-Calvé-Perthes disease, and slipped capital femoral epiphysis.

Physical Examination

The hip examination should begin by observing the patient’s gait for antalgia. Palpation of the hip girdle may reveal some tenderness in the groin region, but this is a nonspecific finding. Lumbar spine, hip, and knee range of motion should be assessed. Frequently, pain will be provoked with hip internal rotation during the hip range of motion assessment. A neurologic examination of the lower extremities should be completed, including evaluation of strength, sensation, and reflexes. The neurologic examination findings are typically normal. The most reliable test for FAI and a labral tear is the anterior hip impingement test, which is done by flexing the hip beyond 90 degrees, then adducting and internally rotating the hip (Fig. 56.2). The result is considered positive if the test elicits anterior groin pain [8]. A hip scouring maneuver, in which the hip is taken from an abducted and externally rotated position, through a flexed and neutral rotation position, and finally into adduction and internal rotation, may produce pain and possibly a “click” if a labral tear is present. Passive hip extension and external rotation may cause pain if a labral tear is present. This is commonly referred to as the posterior impingement test. Hip disease can also be provoked by placing the patient’s leg in a figure four position. This test is referred to as the Patrick test or FABER test because the hip is in a flexed, abducted, and externally rotated position. Intra-articular hip disease can also be elicited by a resisted straight-leg raise in the supine position. Although a detailed physical examination assists the clinician in determining that the patient’s pain is coming from the hip joint, it is nonspecific and cannot differentiate between the various causes of hip pain.