Purpose & Background: Posteroanterior mobilisation (PA) is a manual physiotherapy technique that is commonly used as an examination tool and a form of conservative treatment for spinal complaints. The efficacy of this technique is controversial and this may be in part due to a limited knowledge of the mechanical and physiological mechanisms underlying this technique. This study aims to evaluate the ability of interventional MRI to image the mechanics of mobilisation in terms of spinal movement and soft tissue deformation during a PA mobilisation.

Methods: 5 normal subjects (4 female, 1 male, mean age 29.6 ± 3.9 years) with no current or history of neck pain requiring intervention were recruited into this study, and written informed consent obtained. Subjects were scanned using a General Electric Signa SP10 Interventional MRI scanner (iMR). This is an open MRI scanner consisting of 2 connected but opposing ring “doughnut” magnets. The gap between these magnets is 56 cm generating a uniform field of 0.5Tesla. Subjects were scanned in the prone position with their necks in either a neutral or flexed position. In each position, subjects underwent a PA mobilisation to the 2nd and 6th cervical vertebrae. Sagittal and axial images of the spine were obtained prior to, during and following the mobilisation. Measurements of intervertebral rotation and translation were obtained from the sagittal images, and measures of soft tissue compression with respect to the spinous process were obtained from the axial images. Paired analysis of variance was used to investigate the impact of the mobilisations in each position.

Results: Clear images of vertebral position could be obtained if the mobilisation was sustained once the appropriate force had been delivered. From these images, it is possible to measure vertebral angulation, translation and soft tissue compression. From these measures, it became clear that intersegmental vertebral angulation and translation did not alter as a result of the force applied regardless of cervical position. However, marked and significant changes were seen in terms of soft tissue compression and in some instances overall angulation of the cervical spine.

Conclusion: This pilot work suggests that it is feasible to use iMR technology to study the mechanics of spinal mobilisation. Preliminary findings suggest that there is little or no displacement of the vertebral bodies as a result of an AP mobilisation, although there is considerable soft tissue compression.