Labral Injuries Clinical Correlations Etiology and Classification

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As noted above, the acetabular labrum is a fibrocartilaginous structure attached to the rim of the acetabulum that provides additional surface area for the articulation with the femoral head. The labrum exists at the anterior, superior (lateral), and posterior margins of the acetabulum and is absent inferiorly in the cotyloid fossa, at which point it attaches to the transverse acetabular ligament. Pathology of the labrum including tears, hypertrophy, and instability is perhaps the most common finding on arthroscopic evaluation of the hip joint.

Labral tears represent the most common cause for mechanical hip symptoms. They can be classified according to location, etiology, and morphology. With respect to location, tears can be anterior, posterior, or superior (lateral). Tears most commonly occur anteriorly in most reported series, especially in patients who have sustained occult trauma or have intractable hip pain related to athletic participation. Fitzgerald reported that 92% of labral tears were anterior in a series of patients who sustained minor trauma with associated intractable hip pain. Lage et al found 62% of their labral tears to occur anteriorly, while McCarthy noted 98% anterior tears in his series.15,36

Figure 12.5 demonstrates the typical appearance of an anterior labral tear (after minor trauma) with an associated an terior acetabular chondral injury. This pattern has been frequently demonstrated in the above-mentioned populations (occult trauma, sports) and represents an area in the labrum and acetabulum prone to injury. We have termed this junc-tional injury pattern the "watershed lesion."

Anterior labral tears are also common in patients with degenerative hip disease or acetabular dysplasia. In advanced forms of both diseases, the labral pathology can be rather diffuse and can also involve the lateral and posterior labrum.

Isolated posterior labral tears are most frequently seen after a posterior hip dislocation or with dysplasia, but are not commonly seen in other populations undergoing hip arthroscopy.

Lateral labral tears are infrequently encountered in arthro-scopic evaluation, even with excellent visualization of this structure. When lateral tears occur, they are invariably associated with additional labral and acetabular pathology.

Labral tears can also be classified with respect to etiology. Tears can be degenerative, dysplastic, traumatic, or idiopathic. Degenerative tears can be seen in inflammatory arthropathies. The extent of the tear is related to the degree of degenerative changes present in the joint. Stage I degenerative tears are localized to one segment of an anatomic region (anterior or posterior), while Stage II tears can involve an entire anatomic region, and Stage III tears are diffuse and involve greater than one anatomic region. Higher-stage tears are associated with more pronounced degenerative changes in the acetabulum and femoral head.

Tears associated with dysplasia generally occur most frequently anteriorly, but can also be isolated posteriorly, or diffuse. A common finding in acetabular dysplasia is hypertrophy of the anterior labrum with associated infringement upon the anterior acetabulum. (Figure 12.6.) The hypertrophy and tearing most likely cause impingement of the labrum between

Figure 12.5. The typical appearance of an anterior labral tear (after minor trauma) with an associated anterior acetabular chondral injury.

Figure 12.5. The typical appearance of an anterior labral tear (after minor trauma) with an associated anterior acetabular chondral injury.

Acetabular Trauma

the acetabulum and femoral head, accounting for the mechanical symptoms frequently present in this population.

Labral tears secondary to trauma are generally isolated to a particular region, depending on the direction and extent of trauma. Patients with known posterior subluxation or dislocation most frequently have posterior labral tears. The magnitude of force will determine whether the tear is initiated on the articular or acetabular side of the joint. If a bone fragment is avulsed as seen by x-ray or CT scan, the labral injury is most likely to occur on the capsular side and should be treated accordingly. Those with minor trauma without dislocation al most invariably have anterior tears. These tears occur in the same region as those secondary to minor dysplasia and in the athletic population with intractable pain, which led us to believe that this area is developmentally weakened and susceptible to injury, and/or that it is preferentially exposed to high shear forces leading to injury from overload.

Idiopathic labral tears do not fall into any of the above categories and were found most commonly in athletes with intractable hip pain, and in occupational-related hip pain with no evident trauma. These tears follow the pattern of the watershed lesion.

Labral Tear Classification

Figure 12.7. Labral tears are often fibrillated.

Interstitial Tearing The Junction

Figure 12.7. Labral tears are often fibrillated.

Lage et al15 have created a classification of labral tears based on morphology, with the types being radial fibrillated, radial flap, unstable, and longitudinal peripheral. Radial flap and fibrillated tears involve the free edge of the acetabulum, while longitudinal peripheral tears involve the acetabular-labral junction. Unstable tears do not follow a specific morphologic pattern, but are termed unstable if they cause mechanical impingement. Flap and fibrillated tears tend to be unstable. Additional morphologies in our experience include interstitial tears and synovial side tears. The most commonly encountered tears in both series are radial fibrillated and radial flap tears. (Figure 12.7.)

Arthroscopic treatment of these tears involves debridement back to a stable base and to healthy-appearing tissue. This will eliminate the source of mechanical symptoms secondary to labral pathology. If there is no associated articular cartilage injury or extra-articular pathology, this debridement should alleviate the patient's discomfort. If there is associated focal

Acetabular Chondral Lesion
Figure 12.8. A subchondral acetabular cyst shown with an associated chondral flap lesion.

Figure 12.9. Stage 0: Contusion of the labrum with adjacent synovitis.

Figure 12.9. Stage 0: Contusion of the labrum with adjacent synovitis.

Femoral Head With Arthritis

chondral defect, the subchondral bone is drilled or treated with a microfracture technique to enhance fibrocartilage formation.

Labral tears can also be associated with other intra-articular pathology. Degenerative labral tears, as already mentioned, are seen with degenerative changes in the acetabulum and/or femoral head. Anterior acetabular chondral injuries are frequently seen with anterior labral tears. These most frequently occur in an anteroinferior position and represent the "watershed lesion" demonstrated in several patient populations. Ac-etabular cysts have also been demonstrated in association with labral tears and chondral injuries, especially in those with advanced dysplasia and degenerative joint disease. (Figure 12.8.) In these situations the cyst is most often the result, and not the cause of the patient's mechanical symptoms. Thus, as in a Baker's cyst in the knee, treatment should be directed at the intra-articular chondral abnormality.

Most important, labral tears have now been classified with relationship to outcome. McCarthy et al reviewed 62 hip arthroscopies.36

Hip pathology in association with acetabular labral injuries demonstrated arthroscopically has been incrementally classified and correlated with severity and prognosis. Stage 0 (Figure 12.9), as compared to a normal acetabular labrum, constitutes a contusion of the labrum with adjacent synovitis (1 hip). Stage 1 (Figure 12.10) is a discrete labral free margin tear with intact femoral articular and acetabular articular car

Figure 12.10. Stage 1: Discrete labral free margin tear with intact femoral and acetabular articular cartilage.

Figure 12.10. Stage 1: Discrete labral free margin tear with intact femoral and acetabular articular cartilage.

Femoral AcetabularHypertrophic Acetabular

tilage (10 hips). Stage 2 (Figure 12.11) is a labral tear with focal articular damage to the subjacent femoral head, but with intact acetabular articular cartilage (11 hips). Stage 3 is a labral tear with adjacent focal acetabular articular cartilage lesion, with or without femoral head articular cartilage chondromalacia. Stage 3 labral tears are further subclassified depending on the acetabular cartilage defect. Stage 3A (Figure 12.12) lesions involve less than 1 cm of acetabular articular cartilage (21 hips) and Stage 3B (Figure 12.13) lesions involve greater than 1 cm of acetabular cartilage (10 hips). Stage 4 (Figure 12.14) constitutes a diffuse acetabular labral tear with associated diffuse, arthritic articular cartilage changes in the joint (9 hips). Ninety-five percent (59/62 hips) of the time the labral injury involved the anterior half of the joint. Two patients had a traumatic tear posteriorly associated with an MVA dashboard injury. All patients who had combined anterior and lateral labral injury had associated degenerative arthritis in the joint.

At a minimum of 2 years from hip arthroscopy, patient results were directly correlated with the stage of labral injury. There was one stage 0 lesion and 10 stage 1 labral lesions. All but one of these patients had a good to excellent result (91%). This single patient required an iliopsoas release with V-Y lengthening of the iliotibial band 9 months after ar-

Labral Tear Classification
Figure 12.12. Stage 3A: Lesion involving less than 1 cm of acetabular articular cartilage.

Figure 12.13. Stage 3B: Lesion involving greater than 1 cm of acetabular cartilage.

Figure 12.13. Stage 3B: Lesion involving greater than 1 cm of acetabular cartilage.

Acetebelar Cartilage

throscopy for recurrent painful snapping hip. In addition, there were 11 patients with stage 2 labral tears. Two patients (18%) required further surgical intervention secondary to a poor result, including open synovectomy, capsulectomy, and release of the reflected rectus femoris tendon. There was an 82% good to excellent outcome (9/11 hips) when the tear was resected in stage 2 labral lesions.

Stage 3 labral tears did not fare nearly as well, and the extent of the acetabular cartilage erosion directly impacted the result. Stage 3A labral tears (21 hips) were associated with a good to excellent result in 15 cases (71%), and 2 patients un derwent open synovectomy, anterior capsulectomy, and rec-tus femoris release. Within the Stage 3B group (10 hips) there were 40% good to excellent (4/10 hips), 30% fair (3/10 hips), and 22% poor (2/10 hips). Two patients (20%) underwent further surgical intervention.

Stage 4 labral tear (9 hips) results directly correlated with the extent of hip joint degenerative arthritis. If the articular cartilage involvement was diffuse on the femoral head and acetabulum, regardless of the plain radiographic appearance, the symptomatic improvement post arthroscopy was transient. Seven patients (78%) were associated with a poor result in

Figure 12.14. Stage 4: Diffuse acetabular labral tear with associated diffuse arthritic articular cartilage changes.

Femoral Head Contusion

follow-up and 43% (3/7 hips) eventually went on to total joint arthroplasty within 2 years of arthroscopy.

Complications included a single transient lateral femoral nerve palsy, which resolved within 2 weeks of arthroscopy, and there were no cases of wound infection, deep vein thrombophlebitis, neurovascular injury, or osteonecrosis of the femoral head. Furthermore, all hips were well visualized at surgery.

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