Segmental mobility of the lumbar spine during a posterior to anterior mobilization: assessment using dynamic MRI

Objective. To quantify segmental mobility of the lumbar spine during a posterior to anterior spinal mobilization procedure. Design. Descriptive study using dynamic magnetic resonance imaging. Background. The posterior to anterior spinal mobilization procedure is frequently used in the assessment and management of spinal dysfunction. How this procedure influences segmental spinal motion however, is not known. Methods. Eleven asymptomatic subjects were positioned prone within a vertically open double donut design magnetic resonance imaging system. An anteriorly directed force was applied manually at each lumbar spinous process while magnetic resonance images were obtained continuously in the sagittal plane. The intervertebral angle was used to quantify segmental motion. Results. The direction of motion at the tested segment was always extension, with values ranging from 1.2 (SD 2.2) at L2 to 3.0 (SD 2.3) degrees at L5. When the force was applied at L3, L4 and L5, the non-tested (adjacent) segments also were observed to move into extension. However, when the posterior to anterior force was applied at L1 and L2 the three caudal segments moved into flexion. Conclusions. Posterior to anterior spinal mobilization consistently caused extension at the tested segment, while the motion of the collective lumbar spine was either an increase or decrease in lordosis depending on the segment at which the force was applied.