gms | German Medical Science

Objectives: Torsional deformities are increasingly recognized as an additional factor in young patients with hip pain resulting from pincer- and cam-deformities. For example, decreased femoral torsion can worsen an anterior femoro-acetabular impingement (FAI) conflict while an increased torsion can be beneficial with the same configuration.

It is unknown how often torsional deformities are present in young patients presenting with hip pain that are eligible for joint preserving surgery.

Questions: We questioned (1) what is the prevalence of a pathological femoral torsion in hips with FAI or hip dysplasia? (2) which hip disorders are associated with an abnormal torsion?

Methods: An IRB-approved retrospective study of 463 consecutive symptomatic FAI patients (539 hips) and a MRI or CT scan on which femoral torsion could be measured was performed ('study group'). Out of 915 MRI we excluded 376 hips.

The study group was divided into 10 groups: Dysplasia (< 20° LCE), retroversion, anteverted hips, overcoverage (LCE angle 36-39°), severe overcoverage (LCE >39°), cam (>50° alpha angle), mixed FAI, varus- (< 125° CCD angle), valgus- ( >139° CCD) and Perthes-hips.

The 'control group' of normal hips consisted of 35 patients (35 hips) without radiographic signs of osteoarthritis or hip pain wich was used for a previous study.

Femoral antetorsion was measured according to Tönnis et al. as the angle between the axis of the femoral neck and the posterior axis of the femoral condyles. Normal femoral torsion was defined by Tönnis et al. as angles 10-25° while decreased resp. increased torsion was defined as < 5° and >25°.

Statistical analysis was performed using analysis of variances (ANOVA).

Results:

1.

Fifty-one percent of the patients of the study group presented with abnormal values for femoral torsion. Torsional deformities (< 10° or >25°) were measured in 51.0% of all 539 hips eligible for joint preserving surgery.

2.

Torsional deformities were present in 86.6% of Perthes hips, in 60.9% of dysplastic hips, 52.3 % of hips with overcoverage, in 51.0 % of mixed FAI, in 49.5% of varus hips, in 45.2% of valgus hips, in 45.2% of retroverted hips, in 46.6 % of anteverted hips, in 43.0% of cam FAI, 34.8 % of hips with severe overcoverage.
Analysis of Variances (ANOVA) revealed significant differences (p<0.001) of torsion between normal hips (mean 16.8) and hips with dysplasia (26.1), valgus hips (27.3) and Perthes hips (32.1). Mean femoral torsion was in the normal range in the other groups.

Conclusion: More than half of the patients wich are eligible for joint preserving surgery of the hip present with abnormal femoral torsion. In particular dysplastic-, valgus- and Perthes hips had a significantly altered femoral torsion compared to normal hips.

Femoral antetorsion should be measured in every patient eligible for hip-preserving surgery.