A novel 3D analyzing system for the relative motions of individual vertebrae using 3D MRI; analyzed 3D in vivo intervertebral motions of the lumbar spine during trunk rotation revealed following data:
3D MRI of the lumbar spine was done in 9 positions with 15 degrees increments during trunk rotation (0 degree, 15 degrees, 30 degrees, 45 degrees, and maximum).
1. The mean axial rotation of ten healthy volunteers of each lumbar spinal segment in 45 degrees trunk rotation to each side ranged from 1.2 degrees to 1.7 degrees.
2. Coupled flexion with axial rotation was observed at the segments from L1/2 to L5/S1.
3. Coupled lateral bending of the segments from L1/2 to L4/5 was in the opposite direction of the trunk rotation, while that of T12/L1 and L5/S1 was in the same direction.
4. The direction of the coupled lateral bending in the present study was different from that in the previous cadaver study only at L4/5.
Clinically, lumbosacral list is a common posture. Range of motion and spinal coupling results have not been reported for the lumbosacral list movement. A study determined lumbar coupling during lateral postural translations (lumbosacral list) of the thoracic cage relative to a fixed pelvis.
Four vertebral body corners, mid narrow-waisted body margins, superior and inferior pedicle margins, and spinous-lamina junction of T12-L5 were digitized on 51 anterior-posterior lumbar radiographs.
Using the orthogonal axes of positive x-direction to the left, vertical as positive y, and anterior as positive z, digitized points were used to measure projected segmental z-axis rotation, y-axis rotation, and segmental lateral translations of each vertebra.
Following key observation was marked using superior endplates to superior sacral base:
1. Lateral flexion was largest at L1 and decreased from L1 to L5,
2. But the segmental rotation angles for lateral flexion were largest at L2-L3 (3.9 degrees), L3-L4 (6.2 degrees) and L4-L5 (5.7 degrees) and were in the same direction as the main motion translation.
3. The relative z-axis rotation of T12 was opposite to the direction of L1-L5.
4. The coupled y-axis rotations were less than 1 degree and coupled segmental lateral translations were averaging less than 1 mm.
Clinical relevance of these studies:
These data may be useful for the optimal orthopaedic management of lumbar spinal disorders such as following:
1. The clinically common posture of lateral translation of the thoracic cage (lumbosacral list) is often associated with disc herniation. Yet normal lumbar coupling patterns and total range of motion of this movement have not been established in the literature.
2. Normal values for lumbar segmental coupling on anterior-posterior lumbo-pelvic radiographs during trunk list might be important for an analysis of segmental instability since segmental translations were determined to be 1 mm or less.