Exploring the Role of Lateral Bending Postures and Asymmetric Loading on Cervical Spine Compression Responses

Abstract

In an effort to expand the understanding of head and neck injury dynamics in rollover type crashes, this investigation explores the influence of lateral bending postures and asymmetric compressive loads on the head and cervical spine. Drop testing of five male cadaver head-neck complexes was conducted with either an initial lateral bending posture onto a horizontal impact surface or with an initial neutral posture onto an obliquely oriented surface resulting in lateral bending. Five specimens were dropped from 0.45 and 0.53 m, with resulting impact speeds ranging from 2.9 to 3.25 m/s. Radiography of the specimens was performed pre- and post-testing to document any fractures. Three of the five specimens sustained compressive cervical vertebral fractures at lower neck loads ranging between 1518 N and 3472 N. Fracture patterns did suggest that the asymmetric postures and loading resulted in asymmetric fracture patterns. Overall compressive neck injury dynamics and tolerances appear similar to previous studies of purely sagittal plane dynamics based on these initial results. This study lays a foundation for quantifying the non-sagittal plane compressive response and tolerance of the cervical spine.

Cervical spine injuries and flexibilities following axial impact with lateral eccentricity

“…The very limited previous experimental studies of cervical spine injuries in response to compression with combined lateral bending may represent loading conditions with smaller lateral eccentricities than those of the high eccentricity group in the present study. These specimens reportedly had less soft tissue injuries than those in the high eccentricity group but with fractures of more medial structures; pedicle, facet, and spinous process [28,29]. Specimens in the low eccentricity group in the present study had the smallest eccentricities and these failed primarily through bony fractures of medial structures, in particular, those of the vertebral bodies and endplates with fractures of the laminae and spinous processes.…”

“…Numerous studies using cadaver spines have evaluated injurious sagittal plane compression of the cervical spine [23][24][25][26][27], while, to our knowledge, only two studies and few specimens have examined injurious compression-lateral bending loading [28,29]. The spectrum of injuries produced under axial compression with lateral bending is largely unknown and understanding these is essential to design devices and methods to prevent such injuries and for the identification, evaluation, classification, and treatment of patients with such injuries.…”

Neck Injury Biomechanics

“…Toomey et al, performed drop tests very similar to those on Nightingale et al, except that they were designed to apply combined compression and lateral bending [ 71 ]. It was thought that this confi guration might be more relevant to rollover injuries.…”

“…This is one of the reasons it is diffi cult to deduce the loading mechanism from the injury pattern. Toomey et al conducted one of the few rigorous studies on compressive impact with a lateral component [ 71 ]. The hypothesis was that such an impact would reliably produce asymmetric cervical spine fractures.…”

Sensitivity of Head and Cervical Spine Injury Measures to Impact Factors Relevant to Rollover Crashes

“…A 28 kg steel plate, padded and unpadded, impacted the temporoparietal junction above the external auditory meatus with a velocity of approximately 6 m/s. Nightingale et al (1996) and Toomey et al (2009) conducted inverted axial impacts at approximately 3.2 m/s with ligamentous cadaver head-neck complexes against surfaces of varying orientation to determine the effects of head inertia and impact surface on injury risk to the cervical spine. Select time-dependent responses of the THUMS-for example, resultant head CG acceleration-resulting from the simulated experimental conditions were quantitatively compared to the physical test results, where available, via cross-correlation analysis.…”