Abstract
The hip labrum is a triangular fibrocartilage structure that attaches to the rim of the acetabulum. The hip labrum assists with joint stability and function. The labrum can be torn due to hip instability, femoroacetabular impingement, iliopsoas impingement, and osteoarthritis. Patients with labral tears usually present with groin pain that may be associated with mechanical symptoms of painful clicking or locking. Several physical examination maneuvers assist with identifying intra-articular hip pathology, but none are specific for labral tears. Magnetic resonance arthrography is the gold standard imaging modality for labral tears. Labral tears are usually treated initially with a trial of conservative measures, but frequently require surgical intervention for symptom resolution and joint preservation. Left untreated, labral tears can cause persistent pain, functional limitations, and osteoarthritis.
Keywords
Acetabular, Arthroscopy, Femoroacetabular impingement, Hip, Labral, Labrum
| Synonyms | |
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| ICD-10 Codes | |
| M24.859 | Other specific joint derangements of unspecified hip, not elsewhere classified |
| M24.851 | Other specific joint derangements of right hip, not elsewhere classified |
| M24.852 | Other specific joint derangements of left hip, not elsewhere classified |
Definition
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 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 by up to 20%, 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. Innervation of the acetabular labrum is richest at the anterior-superior and posterior-superior zones.
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. 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.
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, as well as 38.6% of asymptomatic individuals. 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). FAI is characterized by abnormal contact between the femoral head-neck junction and the acetabular rim caused by abnormal bony morphology. Three types of FAI have been identified: pincer, cam, and mixed. 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 (see Fig. 56.1 ). Pincer type FAI typically occurs in middle-aged women, whereas cam type FAI is more common in men in their fourth decade. A majority of cases of FAI have components of both pincer and cam types.
Whereas labral tears associated with both types of FAI tend to occur in the anterosuperior region, the bony abnormalities in cam 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. The labral tears tend to occur on the articular rather than capsular surface. In individuals without osseous abnormalities, tears in the labrum may be the result of repetitive stress at the end range of motion, such as those seen in dancers.
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. Occasionally, the labral tear is due to trauma, with males more likely than females to have an identifiable acute injury. Mechanical symptoms of clicking, locking, and instability are highly variable and not always indicative of intra-articular pathology. A thorough history is critical, including inquiring about childhood diseases such as hip dysplasia, Legg-Calve-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 ). This test is considered positive if it elicits anterior groin pain. This test demonstrates 94% to 99% sensitivity for FAI and labral tears. Flexion-internal rotation test, where the hip is flexed to 90 degrees and internally rotated, also demonstrates excellent sensitivity at 96%. 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 posterior 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 of four position. This test is referred to as the Patrick test or FABER test since 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. This is commonly referred to as Stinchfield’s test. Although a detailed physical examination assists the clinician in determining that the patient’s pain is coming from their hip joint, it is nonspecific and cannot differentiate between the various etiologies of hip pain.
Functional Limitations
Although uncommon, a patient with a labral tear may have a limp or a drop in their hip on the ipsilateral side during stance phase of gait (similar to an uncompensated Trendelenburg gait) and, rarely, may require an assistive device to walk. A labral tear may also cause pain that limits activities, such as gymnastics or construction work, which involve repetitive hip loading, pivoting, and deep flexion.
Diagnostic Studies
Plain radiographs remain the mainstay in evaluating hip pain. A minimum of two radiographic views must be obtained. Proper patient positioning is critical to correctly assess the osseous anatomy. Commonly, an anteroposterior pelvis view and a cross-table (false profile) lateral view of the affected hip are utilized. In individuals with groin pain or acetabular labral tears, at least one bony abnormality consistent with FAI is present in 94.3% and 87% of these groups, respectively. In males, an increased alpha angle and in females, an increased Tonnis grade or decreased neck-shaft angles are associated with larger labral tears.
Pincer type FAI may be due to generalized over-coverage of the femoral head due to an excessively deep acetabulum, or from focal over-coverage related to acetabular retroversion. On the anterior-posterior radiograph of the pelvis, the normal acetabulum should cover at least 75% of the femoral head. A deep acetabulum is present if the acetabular fossa or the femoral head projects medial to the ilioischial line. Focal acetabular retroversion is suggested by the cross over sign ( Fig. 56.3 ), in which the cephalad portion of the anterior acetabular wall is lateral to the posterior acetabular wall. The cross-table lateral radiograph may demonstrate posteroinferior joint space narrowing.
Cam type FAI can be evaluated with anterior-posterior pelvis and cross-table lateral radiographs. The primary radiologic finding of cam type FAI is a decrease in the anterior or superior femoral head-neck offset distance, which causes the femoral head neck junction to appear flattened or convex rather than concave. The asphericity of the femoral head-neck junction caused by cam type FAI is commonly referred to as a pistol grip deformity ( Fig. 56.4 ).
