Transections of the C1-C2 joint capsular ligaments in the cadaveric spine.

The purpose of this study was to examine the mechanical function of the C1-C2 capsular ligaments. Physiologic torques of up to 1.5 Nm were applied to human fresh cadaveric specimens (C0-C1-C2-C3) in three dimensions, and the three-dimensional motion of C1 relative to C2 was recorded. Two groups of cadaveric specimens were used to study the effect of two different sequential ligamentous transections. In the first group (n = 4), the transection of the left capsular ligament was followed by transection of the right capsular ligament. In the second group (n = 10), the transection of the left capsular ligament was preceded by transection of the left and right alar and transverse ligaments. The greatest changes in motion occurred in axial rotation to the side opposite the transection. In the first group, left capsular transections resulted in a significant increase in axial rotation range of motion to the right of 1 degree. After the right capsular ligament was transected, there was a further significant increase of 1.8 degrees to the left and 1.0 degree to the right. Lateral bending to the left also increased significantly by 1.5 degrees after both ligaments were cut. In the second group, with the nonfunctional alar and transverse ligaments, transection of the left capsular ligament resulted in greater increases in range of motion: 3.3 degrees to the right and 1.3 degrees to the left. Lateral bending to the right also increased significantly by 4.2 degrees.