The labrum is a thin rim of triangular soft tissue that attaches to the periphery of the acetabulum. It is similar to the labrum in the shoulder, but, unlike in the shoulder, does not encircle the whole acetabulum. Rather, it transitions into the transverse acetabular ligament at the inferior portion of the acetabulum.
Functions of the Labrum
The labrum has several functions including improving hip stability, maintaining joint lubrication (and negative pressure), proprioception, and shock absorption. A labral tear therefore disrupts joint integrity and left untreated, can advance the rate at which arthritis develops.
Labral tears occur more frequently anterosuperiorly due to less bony constraint, labral orientation, and the tenuous blood supply at this location. Causes include trauma, structural abnormalities, capsular laxity, hip hypermobility, and arthritis.
Labral Tears May Be Symptomatic or Asymptomatic
Hip labral tears occur in a fair number of athletes, as well as in patients presenting with groin pain or mechanical symptoms. However, they can also be found in a good number of asymptomatic patients. Therefore, the absence of mechanical symptoms should not be a cause for immediate exclusion of labral tears as an etiology for hip pain. Women tend to get them more than men, and this may be due to pelvic anatomy, greater joint mobility, and a higher incidence of hip dysplasia.
Patients presenting with a labral tear tend to be younger and more active and will complain of pain about the groin and/or anterior hip. This pain may radiate distally into the thigh and be associated with mechanical symptoms of catching or clicking. Patients may describe worsening of their symptoms with loading or rotational activities of the hip.
How Labral Tears Are Diagnosed
The diagnosis can often be made based on characteristic physical exam and imaging findings, but it is important to rule out other, more serious diagnoses that may require more emergent surgical attention. On physical exam, provocative hip maneuvers including FADIR (hip flexion, adduction, internal rotation) and FABER (hip flexion, abduction, external rotation) will elicit sharp groin pain.
While these are more characteristic for anterior labral tears, they may be negative with posterior tears. For the latter,
extension, abduction and external rotation elicit pain in the buttock and/or anterior hip.
Imaging and Treatment
Imaging begins with an AP pelvis and lateral view of the hip, both of which can demonstrate underlying anatomic
derangements whilst also confirming or ruling out other diagnoses for hip pain. MRI is necessary to confirm the diagnosis.
Treatment begins with non-operative interventions including physical therapy, NSAIDs, and activity modification. Patients should be advised that up to three months of physical therapy may be required to improve pain and function. Intra-articular steroid injections can be useful if there is persistent pain and dysfunction. More recently, studies looking at the role of PRP and stem cells suggest a potential future role for these agents, though research is still ongoing. Worse outcomes are found in patients who already exhibit degenerative changes, are obese and/or older.
When performed in the right patient, hip arthroscopy can prolong the time to a hip replacement. The converse is also true, and hip arthroscopy may increase the rate of conversion to a hip replacement when done in the obese, elderly, or patients with preexisting arthritis. Overall, studies demonstrate improved outcome scores when the labrum is repaired or reconstructed instead of debrided. Patient satisfaction scores after hip arthroscopy remain quite variable, ranging from just under 50% to over 90%.