Study Design. Method validation and in vivo motion segment study.
Objective. To determine in healthy subjects in vivo intervertebral segmental kinematics and coupled motion behavior in all 3 planes simultaneously for 3 segments and to evaluate whether these results differ from those in the normal population according to the literature.
Summary of Background Data. Few studies have provided a direct invasive approach to investigate segmental kinematics in vivo. Dynamic recordings of 3-dimensional segmental motion patterns of adjacent segments have rarely been reported. To date, no studies have examined the 3-dimensional segmental movements of the thoracolumbar junction in vivo in detail.
Methods. K-wires were inserted into the Th11, Th12, L1, and L2 spinous processes of 21 healthy subjects. Ultrasound markers and sensors were attached to the k-wires. Real-time motion data were recorded during standardized ranging exercises. Errors caused by the k-wires, and the static and dynamic accuracy of the system, were considered.
Results. Large intersubject variation was found in all of the exercises. The average ranges of motion from Th11 to L2 were 18.7° for flexion-extension, 13.5° for one-sided lateral bending, and 1.8° for one-sided axial rotation. Coupled-motion patterns among the subjects showed a coupled flexion in active lateral bending and a coupled extension in active rotation, but the results were inconsistent for active extension and flexion.
Conclusion. This method offered accurate multisegmental dynamic-recording facilities. The dynamic exercises showed high reproducibility. The ranges of motion for extension/flexion and lateral bending differed from those reported in previous studies. The coupling patterns were only partly consistent because of large interindividual variation. The measurement error was comparable with that of other invasive methods.