Kinematic analysis and simulation of vertebral motion under static load-part I: kinematic analysis.

The paper presents the kinematic analysis of motion segments of ten, humanlumbar spines. In order to achieve this objective, a spine fixture and a linkage transducer were designed. The spine fixture is capable of holding the motion segment in a prescribed plane of loading. With the designed fixture it becomes possible to apply three types of shear loads, and three types of bending loads. In addition, if desired, a compressive preload may be applied to a motion segment. The linkage transducer consists of six rotary potentiometers connected by seven rigid links. The transducer is capable of measuring all possible components of vertebral motion. The motion data in the motion segments of ten lumbar spine were collected under the influence of combined shear and bending loads applied in an incremental manner. Maximum shear load was 35.6 N and maximum bending load was 6780 N. mm. The motion segments did not show any appreciable difference in their motion beyond these loads. The motion segments were not subjected to any compressive preload. The range of motion data were collected in twelve loading planes 15 deg. apart. The characteristic vertebral motion may be described in terms of range of motion, its components, and the parameters associated with the screw motion. The paper presents data in the chart form to describe the kinematic characteristics of the lumbar motion segment.