Ultrasound measurements of lumbar spinous process movement during flexion distraction manipulation: a preliminary descriptive cross-sectional study with healthy participants.

Background: Chronic low back pain is a prevalent condition that impairs productivity and quality of life. While spinal manipulative therapy reduces pain and disability, the biomechanical mechanisms underlying these effects remain unclear. This study utilized diagnostic ultrasound to measure lumbo-sacral spinous process movement (L3-S1) during Cox^® Flexion Distraction manipulation, Protocol I, providing insight into spinal intersegmental motion.

Methods: This study analyzed a convenience sample of generally healthy participants, aged 21 years and older, from both sexes and various ethnicities who reported no back pain. Participants were recruited through announcements and flyers posted around the Keiser university campus. Data was collected from June-August 2022. The participants were positioned prone on a specialized flexion distraction chiropractic table. Ultrasound imaging was performed to measure the spinous process distance from L3-S1 before the procedure, during flexion distraction utilizing standard Protocol I, and post-procedure. Ultrasound measurements were recorded by identifying the tips of the spinous processes and distances between L3-L4, L4-L5, and L5-S1, before, during, and after flexion distraction. Statistical analyses included paired t-tests to evaluate spinous process distances pre- and during Cox^® Flexion distraction, independent t-tests for gender differences, and linear regression for body mass index (BMI) and age correlations with changes in separation distance.

Results: Thirty participants (16 male, 14 female) with a mean age of 32.5 years (Standard deviation [SD] 10.4), mean weight of 69.2 Kg (SD 11.8), mean height of 169.0 cm (SD 8.9), and BMI of 23.9 underwent Cox^® Flexion Distraction Protocol I. Spinous process separation increased during treatment: L3-L4 (0.13 mm), L4-L5 (0.13 mm), and L5-S1 (0.16 mm). Paired ttests showed significant pre- and during-treatment changes (p < 0.001), with moderate correlations to BMI (R²=0.61) and age (R²=0.58). Gender differences did not reveal statistical differences in separation distances at all lumbar levels measured (p > 0.1).

Conclusion: Ultrasound imaging revealed significant separation of spinous processes at L3-L4, L4-L5, and L5-S1 during Cox^® Flexion Distraction Protocol I. Statistical analyses showed separation correlated moderately with age and BMI that was unaffected by gender. Future studies should assess this technique's relevance in patients with low back pain.