Acetabular Labral Tear

Acetabular Labral Tear of the hip are more common than previously thought. Its Incidence is highest in patients with acetabular dysplasia.

Researchers have attributed the labral injury to a variety of causes. Direct trauma, sporting activities, and certain movements of the hip including torsional or twisting movements have been cited to cause labral tears. However, a large percentage of labral tears are not associated with any known specific event or cause.

Acetabular Labral Anatomy

The acetabular labrum is a fibrocartilaginous structure that surrounds the periphery of the acetabulum and inserts on the transverse acetabular ligament.

Blood supply to the acetabulum is primarily through the obturator artery, superior gluteal artery, and inferior gluteal artery. The periphery of the labrum is more vascularized than the articular region.

The labrum functions to increase the stability of the hip joint and to seal the hip joint and prevent escape of fluid. In the presence of a labral tear, this latter function is lost and may lead to increased contact pressure, which is thought to have a role in the development of degenerative disease of the hip.

See Also: Hip Joint Anatomy

Mechanism of Injury

Two common types of aAcetabular labral tear mechanisms have been recognized:

1. A young person with a twisting injury to the hip, usually an external rotation force in a hyperextended position.
2. An older person with a history of hip and/or acetabular dysplasia, or the result of repeated pivoting and twisting.

Acetabular labral tears represent the most common cause for mechanical hip symptoms – in a recent study, they were found to be the cause of groin pain in more than 20% of athletes presenting with groin pain.

Acetabular Labral Tear Classification

Labral tears can be classified according to location, etiology, and type:

Location:

With respect to location, tears can be:

1. anterior,
2. posterior,
3. superior (lateral).

although anterior and anterosuperior tears appear to be the most common.

Anterior labral tears are also common in patients with degenerative hip disease or acetabular dysplasia. The most likely reason for the prevalence of anterior labral tears is that this region is subjected to higher forces or greater stresses than other regions of the labrum.

Because of the anterior orientation of both the acetabulum and the femoral head, the femoral head has the least bony constraint anteriorly and relies instead on the labrum, joint capsule, and ligaments for stability.

Etiology:

With respect to etiology, tears can be:

1. Degenerative,
2. Dysplastic,
3. Traumatic,
4. Idiopathic.

Degenerative tears can also be seen in association with inflammatory arthropathies.

Type:

Labral tears have been classified into four types:

1. Radial flap (the most common type),
2. Radial fibrillated,
3. Longitudinal peripheral,
4. Abnormally mobile.

Seldes et al. classified acetabular labral tears into type 1 and type 2 on the basis of their anatomical and histological feature:

1. Type 1 tears consist of detachment of the labrum from the articular cartilage surface. These tears tend to occur at the transition zone between the fibrocartilaginous labrum and the articular hyaline cartilage. They are perpendicular to the articular surface and, in some cases, extend to the subchondral bone.
2. Type 2 tears consist of one or more cleavage planes of variable depth within the substance of the labrum.

Both types of tears are associated with chondrocyte proliferation and hyalinization of the labral fibrocartilage along the edges of the defect. All labral tears are associated with increased microvascularity within the substance of the labrum at the base of the tear adjacent to the labrum’s attachment to bone. Osteophyte formation is also sometimes seen within the labral tears.

Labral Tears Diagnosis

Diagnosis can be made on the basis of the history and physical examination. However, it must be remembered that labral tears can have a variety of clinical presentations associated with a wide degree of clinical findings.

History:

Since a labral lesion produces a decrease of pressure within the joint and causes an increase in the laxity of that joint, symptoms of a labral tear are usually mechanical:

1. buckling,
2. twinges,
3. locking,
4. instability,
5. painful clicking.

There may or may not be a history of trauma. In the presence of a recalled incident, the trauma can vary from severe to very mild. The injury is usually caused by the hip joint being stressed while in rotation.

The pain is mainly in the anterior groin (most commonly) but can be in the thigh and/or medial knee, trochanteric, or buttock region. It can have an acute onset or be gradual, and it is common for it to be sharp with a clicking, snapping, catching, or locking sensation.

Activities that involve forced adduction of the hip joint in association with rotation in either direction tend to aggravate the pain.

Physical examination:

On examination, ROM of the hip may not be limited, but there may be pain at the extremes.

There is little information regarding the sensitivity, specificity, or likelihood ratios associated with a single clinical test or a cluster of tests in diagnosing a labral tear.

Generally speaking, the combined movement of flexion and rotation causes pain in the groin.

More precisely, the specific maneuvers that may cause pain in the groin include:

• FADDIR Test: Flexion, adduction, and internal rotation of the hip joint (impingement test / scour test) while it is held in at least 90 degrees of flexion and at least 15 degrees of abduction, positive with anterior superior tears, anterior labral tears, and iliopsoas tendinitis;
• Passive hyperextension, abduction, and external rotation (with posterior tears), with the patient lying supine at the edge of the table; a positive finding with this test is apprehension or exquisite pain and suggests anterior hip instability, an anterior labral tear, or posteroinferior impingement;
• Resisted straight-leg raise test (stinchfield test);
• Flexion of the hip with external rotation and full abduction, followed by extension, abduction, and internal rotation (anterior tears);
• Extension, abduction, and external rotation brought to a flexed, adducted, and internally rotated position (posterior tears).

In general, the clinician should suspect an acetabular labral tear when a patient has the following combination of signs and symptoms:

1. no restrictions in Hip ROM.
2. normal radiographs.
3. complaints of a long duration involving anterior hip or groin pain and clicking.
4. pain with passive hip flexion combined with adduction and internal rotation.
5. pain with an active straight-leg raise.

Imaging Diagnosis

The diagnosis is typically confirmed with arthrography, MRI with intravenous or intra-articular administration of contrast medium, or arthroscopy.

Acetabular Labral Tear Treatment

Conservative Treatment has traditionally included:

1. bed rest with or without traction,
2. followed by a period of protected weight-bearing,
3. use of nonsteroidal anti-inflammatory medication.

Operative treatment of labral tears consists of arthrotomy or arthroscopy with resection of the entire labrum or the portion of the labrum that is torn.

References

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