What Is the Influence of Femoral Version on Size, Tear Location, and Tear Pattern of the Acetabular Labrum in Patients With FAI?

Background: Femoral version deformities have recently been identified as a major contributor to femoroacetabular impingement (FAI). An in-depth understanding of the specific labral damage patterns caused by femoral version deformities may help to understand the underlying pathomorphologies in symptomatic patients and select the appropriate surgical treatment.

Questions/purposes: We asked: (1) Is there a correlation between femoral version and the mean cross-sectional area of the acetabular labrum? (2) Is there a difference in the location of lesions of the acetabular labrum between hips with increased femoral version and hips with decreased femoral version? (3) Is there a difference in the pattern of lesions of the acetabular labrum between hips with increased femoral version and hips with decreased femoral version?

Methods: This was a retrospective, comparative study. Between November 2009 and September 2016, we evaluated 640 hips with FAI. We considered patients with complete diagnostic imaging including magnetic resonance arthrography (MRA) of the affected hip with radial slices of the proximal femur and axial imaging of the distal femoral condyles (allowing for calculation of femoral version) as eligible. Based on that, 97% (620 of 640 hips) were eligible; a further 77% (491 of 640 hips) were excluded because they had either normal femoral version (384 hips), incomplete imaging (20 hips), a lateral center-edge angle < 22° (43 hips) or > 39° (16 hips), age > 50 years (8 hips), or a history of pediatric hip disease (20 hips), leaving 20% (129 of 640 hips) of patients with a mean age of 27 ± 9 years for analysis, and 61% (79 of 129 hips) were female. Patients were assigned to either the increased (> 30°) or decreased (< 5°) femoral version group. The labral cross-sectional area was measured on radial MR images in all patients. The location-dependent labral cross-sectional area, presence of labral tears, and labral tear patterns were assessed using the acetabular clockface system and compared among groups.

Results: In hips with increased femoral version, the labrum was normal in size (21 ± 6 mm 2 [95% confidence interval 20 to 23 mm 2 ]), whereas hips with decreased femoral version showed labral hypotrophy (14 ± 4 mm 2 [95% CI 13 to 15 mm 2 ]; p < 0.01). In hips with increased femoral version, labral tears were located more anteriorly (median 1:30 versus 12:00; p < 0.01). Hips with increased femoral version exhibited damage of the anterior labrum with more intrasubstance tears anterosuperiorly (17% [222 of 1322] versus 9% [93 of 1084]; p < 0.01) and partial tears anteroinferiorly (22% [36 of 165] versus 6% [8 of 126]; p < 0.01). Hips with decreased femoral version showed superior labral damage consisting primarily of partial labral tears.

Conclusion: In the evaluation of patients with FAI, the term "labral tear" is not accurate enough to describe labral pathology. Based on high-quality radial MR images, surgeons should always evaluate the combination of labral tear location and labral tear pattern, because these may provide insight into associated femoral version abnormalities, which can inform appropriate surgical treatment. Future studies should examine symptomatic patients with normal femoral version, as well as an asymptomatic control group, to describe the effect of femoral version on labral morphology across the entire spectrum of pathomorphologies.

Level Of Evidence: Level III, prognostic study.