Cervical spine injury potential resulting from sagittal plane inertial loadin

Objective. To explore the effects of head-mass induced inertial loads on potential compressive neurologic injury in the human cervical spine by quantifying the relationship between sagittal acceleration (+/-Gx) and measured changes in neural space geometry during impact.;Methods. Fifteen unembalmed osteoligamentous human spines (occiput to T5) were potted from T2 to T5 in dental plaster. While retaining C0-C1-C2 anatomic integrity, head-mass inertial load was provided by mounting an instrumented Hybrid III manikin head to the occiput of the cadaveric specimen. After removal of the entire spinal cord and nerve roots of C3-C6, these foramina were instrumented with neural space occlusion transducers. These transducers have been designed to measure dynamically the cross-sectional area of bony foramina that house the neurologic tissues in the spine during in vitro testing.;Using a closed-loop bench-top sled, these instrumented specimens were subjected to a combined total of 67 acceleration events ranging from 19.6 m/s2 (2g) to 98.1 m/s2 (10g) peak acceleration in both the +Gx and -Gx direction. In addition to orthogonal-linear and sagittal plane rotational accelerations within the manikin head, each of the sixteen neural space occlusion data channel were collected at 4000 samples per second.;Results. Significant neural space occlusions were found in both +Gx (rear-end) and -Gx (frontal) acceleration impacts. -Gx generated significant canal occlusion in the lower cervical spine while +Gx generated significant intervertebral foramen occlusion at the C5 and C6 root levels. At these lower spinal levels there was also significant occlusion differences between positive and negative sled acceleration in both the spinal cord and intervertebral foramen. Similar differences did not prevail for acceleration magnitude. Non-physiologic motions during the inertial loading generated simultaneous foramen occlusions and openings in the lower and upper sections of the spine, respectively, during rear-impact collisions. Dynamic occlusions greater than those seen during normal range of motion occurred at an average acceleration level of 4.55g (foramina) and 2.92g (spinal canal). Mechanical failure of the cadaveric specimen occurred on average at 7.38g. Dynamic occlusions during these failure events were typically not different from the non-failure occlusions. Significant correlations were found between age and failure acceleration magnitude.