Highlighting of intervertebral movements and variations of intradiskal pressure during lumbar spine manipulation: a feasibility study.

OBJECTIVES To demonstrate relative movement of the vertebrae and variations in intradiskal pressure during 2 different lumbar spinal manipulations, in flexion or extension, in 2 unembalmed cadavers. DESIGN A pressure sensor was inserted into the L3-4 disk in cadaver 1 and into the L1-2 to L4-5 disks in cadaver 2. Two adjacent vertebrae (L3 and L4 in cadaver 1, and L4 and L5 in cadaver 2) were each equipped with 2 monoaxial accelerometers to record acceleration in the caudocranial axis and a biaxial accelerometer to record acceleration in the "horizontal" anatomic plane. SETTING Laboratory study. RESULTS During the thrust, relative intervertebral movements were demonstrated; movements differed with the type of manipulation (in flexion or extension). Intradiskal pressure initially increased, then decreased. CONCLUSIONS Lumbar spinal manipulations have a biomechanical effect on the intervertebral disks, producing a brief but marked change in intradiskal pressure. This effect, which differs slightly with the different types of manipulation studied, is the consequence of movements of the adjacent vertebrae.