Objective: To investigate the direction and magnitude of mechanical shift of the disc at each lumbar segment during left side bending and left side gliding movements.

Design: Cross-over design with random allocation of the order of side bending or side gliding.

Setting: Shinoro Orthopaedic, Japan.

Patients: 20 asymptomatic (10 male, 10 female) subjects, mean age 24.8 years. Inclusion criteria were no lower back pain and no contraindications on MRI. Exclusion criteria were movement loss of the back or lateral deformity of the spine, or Grade III disc degeneration in the lumbar spine in L1-S1 shown on MRI

Intervention: The patient was supine for several MRI images taken in a neutral position. Each subject was then scanned in end-range left side bending (SB) and end-range left side gliding (SG) positions. The MRI images were taken in the sagittal, coronal and axial planes. Left side gliding is defined as a movement of the shoulders to the left relative to the pelvis where a horizontal line is maintained through the shoulders. The order of the two positions was randomized and a 30 minute rest in lying was given between the scans in the two positions. In each testing position, the pelvis was stabilized to the table to prevent any rotation of the pelvis.

For the MRI scan in left SB, the subject performed maximum left SB, then one assistant applied manual overpressure through the shoulders to maintain the end range position. Another assistant held the subject’s knees to minimize any movement.

Each participant performed end range left SG in standing before attempting the same position in lying for the MRI scan. The supine lying left SG position to end range was created with the subject positioned next to a wooden pillar with the right elbow flexed and resting beside their trunk. Folded towels were placed between the wooden pillar and the subjects’ arm to encourage end-range movement of the shoulders to the left. The patient’s pelvis was passively pushed to the pillar on the right and stabilized with a belt. An assistant maintained a line through the shoulders perpendicular to the sagittal plane.

Main Outcome Measures:

Quantification of the segmental lateral flexion angles at end-range left side gliding and side bending at each vertebral level from L1 to the sacrum compared to the images taken with the subject in neutral.
Quantification of the segmental rotation angles at end-range left side gliding and side bending at each vertebral level from L1 to the sacrum compared to the images taken with the subject in neutral.
Comparison between side bending and side gliding at each vertebral level.
Disc hydration shift was assessed as the differences of mid-point values in each plane between the supine position and the SB and SG positions.

Main Results: The segmental lateral flexion angle between L1/2 had a significant difference between SB and SG, with no other segmental lateral flexion or rotation level showing a difference between the two movements. The disc hydration shifted to the right in both SB and SG positions, but showed no significant difference between the two movements.

Conclusions: There is a mechanical shift of the nuclear disc material in the contralateral direction with both side bending and side gliding movements at each disc level in healthy young people.

Comments and implications for the MDT clinician: The author reports that this study is the first to quantify the amount of nuclear shift at each disc level, as well as comparing the degree of movement with both left SG and SB. The results in regards to disc hydration were comparable. They report in the study that the MRI was performed with the subject at the end range of either SB or side gliding, but note that clinically in the MDT system, each patient would likely perform repeated end range movement, which might allow even further nuclear movement. The authors also note that side gliding instead of side bending movements in the MDT system may be preferable due to safety reasons: SG in standing may be more stable than SB, and patients with pain may have difficulty shifting laterally to their end range of SB. Clinically, we can appreciate that examining SG allows us to observe the extent of movement and the effect of the movement that is the same as that adopted when a patient with low back pain +/- sciatica is shifted to one extent or another.

As this study was performed on a small number of young subjects. It would be interesting to examine if subjects older than 40 years demonstrated similar shift in disc hydration, or to examine any changes in pain level of symptomatic subjects.

Lumbar: Anatomical & physiological studies