Biomechanical Analysis of Cervical Spine Injury Mechanisms in Rugby through Computational and Modelling Techniques

Abstract

In this thesis an integrated biomechanical framework was developed and applied for the investigation of catastrophic cervical spine injuries in rugby. The main aims of the thesis were to identify the primary injury mechanism of the commonly observed bilateral facet dislocations and secondly highlight the implications of technique on cervical spine injury risk during misdirected impacts. The integrated framework combined experimental in vitro and in vivo data that guided in silico methodologies to provide the most realistic representation of the injurious events. Firstly impact specific passive joint parameters (stiffness and damping) were estimated that described the cervical spine's response to axial loads representative of misdirected rugby impacts. Results showed a larger increase in axial joint stiffness compared to damping which was representative of the rate dependant loading response of intervertebral discs. Secondly a MRI-informed musculoskeletal model was developed and used for the estimation of neck muscle recruitment patterns experienced by players prior to rugby contact events. Knowledge of how muscles activate prior to impacts is crucial to describe the dynamic response of the cervical spine to misdirected loading. An EMG-assisted optimisation methodology was applied for the analysis of in vivo staged tackles and scrums in order to estimate neck muscle activations using the MRI-informed model. The EMG-assisted method tracked experimental neck joint moments (RMSE = 0.95-1.07 Nm; R2 = 0.90-0.95) whilst generating physiological muscle activation patterns (RMSE < 0.1; R2 > 0.8) and maintaining experimental co-contraction ratios. Finally and in order to answer the original research questions the passive parameters were included in the MRI-informed musculoskeletal model which was then used in theoretical simulations. Estimated in vivo neck muscle activations and kinematics during rugby tackles were prescribed to the model and in vitro impact forces were applied to seven skull locations. The initial neck angle of the model was changed trough 5 increments to investigate the effect of tackling technique. Results showed that initial neck extension angles and cranial head impact locations had the largest effects on maximal compression, anterior shear and extension moment loads. The pattern and combination of these loads in the lower cervical support buckling as the primary injury mechanism for rugby injuries and highlights the importance of correct tackling technique to reduce injury risk. In conclusion, this thesis provided the first evidence-based biomechanical evaluation of rugby spinal injuries within an injury prevention research model. This framework can inform future neck and head injury prevention policies in rugby and other impact sports.

Date of Award	4 Nov 2020
Original language	English
Awarding Institution	University of Bath
Supervisor	Ezio Preatoni (Supervisor), Richie Gill (Supervisor) & Dario Cazzola (Supervisor)