Biomedical subjects
B J Doherty
Publications and source records attributed to B J Doherty.
The viscoelastic responses of the human cervical spine in torsion: experimental limitations of quasi-linear theory, and a method for reducing these effects.
The dynamic torsional viscoelastic responses of the human cadaver cervical spine were measured in vitro. The quasi-linear formulation of time dependent behavior was used to describe and predict the resultant torque as a function of applied angular deflection and time. The performance of the quasi-linear model was good, reaching correlation at the 99% confidence level; however, it tended to underestimate hysteresis energy (mean relative deviation = -19.1%) and observed stiffness. This was in part due to difficulties in establishing the physical constants of the quasi-linear model from finite rate relaxation testing. An extrapolation deconvolution technique to enhance the experimentally derived constants was developed, to reduce the detrimental effects of finite rate testing. The quasi-linear model based on this enhanced derivation showed improved predictive ability and hysteresis energy determination.
The role of torsion in cervical spine trauma.
A dynamic servocontrolled torsion machine has been used to characterize cervical injury due to pure rotation of the head. Resultant force moment, torque, and applied rotation have been measured. Torque applied to the base of the skull resulted in injury to the atlantoaxial joint. No evidence of lower cervical injury was observed by computed tomography, magnetic resonance imaging, in situ fluoroscopy, or visual inspection. Torque applied directly to the lower cervical spine induced ligamentous injury and unilateral facet dislocation; however, the torque to injure the lower cervical spine was significantly greater than the torque to injure the atlantoaxial joint. It was concluded that pure rotation of the head does not mediate lower cervical ligamentous injury because of the comparative weakness of the atlantoaxial joint.