FEMORAL NECK IRREGULARITIES IN YOUNG ADULTS - A COMMON FINDING. PRELIMINARY RESULTS

Purpose To determine whether radiographically demonstrated femoral neck irregularities (pistolgrip-deformity, focal prominences or lytic defects) are associated with positive clinical impingement tests. Methods The 1989 Bergen birth cohort (n=4004) was invited to a population-based follow-up including clinical examination and two pelvic radiographs. 2081 (52%) were enrolled. Associations between clinical and radiographic findings were examined using chi-squared or Fischer9s exact test. Results Radiographs from 1193, 18-19 year olds, (42% males) have been analysed. For males, irregularities were seen in 128/501 (15.5%) right and 149/501 (19.7%) left hips, of which 13 (10.2%) and 12 (8.1%) had a positive impingement-test respectively (p-values 0.06 and 0.04). The pistolgrip-deformity was seen in 15.8% of right and 19.4% of left hips, of which 6.3% and 7.2% had a positive impingement-test, respectively (p-values 0.6 and 0.3); the focal prominence in 9.2% right and 10% left hips, of which 15.2% and 4% had a positive impingement-test (p-values 0.008 and 0.74) and the lytic defect in 7% right and 8.8% left hips, of which 14.3% and 9.1% had a positive impingement-test (p-values 0.053 and 0.19). For females, irregularities were seen in 34/692 (4.9%) right hips and 46/692 (6.6%) left hips, of which 0 and 2 (4.3%) had a positive impingement-test (p-values 1 and 0.65). Each irregularity was seen in 2-3% of both right and left hips, with no positive impingement tests on the right side and one positive test for each left side, yielding p-values from 0.45 to 1. Conclusion Femoral neck irregularities are common and symmetrical findings in young males, and are associated with a positive impingement-test. A focal right-sided prominence is associated with a positive test. These radiological findings seem to be less common, but symmetrical, in young females, but without any association with a positive impingement-test.