Influence of cervical spine position, turning time, and cervical segment on cadaver intradiscal pressure during cervical spinal manipulative therapy.

OBJECTIVE: The purpose of this study was to determine influences of cervical spine positions, turning times, and cervical segments on cadaver intradiscal pressure (IDP) during cervical spinal manipulative therapy (SMT). METHODS: We simulated cervical SMT with stretching and rotation on 7 fresh adult cadaver specimens in the material test system machine. The changes in IDP for cervical intervertebral disks (C3/4, C4/5, and C5/6) during 4 different stages of cervical SMT (physiologic state, end of the traction stage, turning stage, and finish time) were monitored. Five different cervical positions (extension 20°, extension 10°, neutral position, flexion 10°, flexion 20°) and 3 different turning times (0.06, 0.11, 0.16 second) of IDP were monitored, using micropressure sensors. RESULTS: The variable tendency of cervical IDP presents a "V"-shaped curve during SMT. The 4 stages of SMT had significantly different IDP (F=5498.956; P<.001). There were also significant differences in IDP between 5 cervical positions ([F=1371.216; P<.001], [flexion 20°>flexion 10°>neutral position>extension 10°>extension 20°]), 3 turning times ([F=419.530; P<.001], [0.06>0.11>0.16 seconds]), and 3 cervical segments ([F=84.282; P<.001], [C3/4