[Sonographic study of the AP translation of the humeral head in the active movement of traumatic anterior shoulder instability].

In a prospective study we evaluated the ap-translation of the humeral head in the glenoid socket during active joint movements. In 150 healthy volunteers we documented normative data for four different joint positions. We compared these results with the data of 36 patients with traumatic anterior shoulder instability. The normal joint in adducted position shows a dorsal overhang of the humeral head in relation to the dorsal brim of the glenoid of 8.9 mm (+/- 3.0) on the dominant and of 9.1 mm (+/- 3.1) on the non dominant side. In the 90 degrees flexion position the dorsal overhang was 7.6 mm (+/- 3.5) on the dominant and 8.0 mm (+/- 2.3) on the non dominant side. In neutral as well as in the flexion position we found no differences between men and women nor between the dominant and non dominant extremity. In 90 degrees abduction and neutral rotation, the dorsal overhang was 1.5 mm (+/- 3.5) on the dominant side and 1.9 mm (+/- 3.4) on the non dominant side in the volunteer group. However, in patients with shoulder instability we found a statistically highly significant difference with a ventral overhang of 3.0 mm (+/- 4.0) on the dominant side. On the non dominant side a dorsal overhang of 0.3 mm (+/- 3.7) still remained in the above mentioned position. The differences between both sides were statistically highly significant. In abduction and external rotation we found a similar relation with a highly significant larger anterior translation of the humeral head in patients with unstable shoulder joints.