Company: Southwest Research Institute (SwRI)
Contracting Agent: Naval Biodynamics Laboratory/Naval Air Warfare Center Aircraft Division

Purpose: Develop a methodology and computational tool for performing finite element-based probabilistic cervical spine injury analysis.

Background: Cervical spine injuries occur as a result of impact or from large inertial forces such as those experienced by military pilots during ejections, carrier landings, and ditchings. Other examples include motor vehicle, diving, and athletic related accidents. Reducing the likelihood of occupant injury by identifying and understanding the primary injury mechanisms and the important factors leading to injury motivates most research in this area. Therefore, it is of broad interest to design occupant safety systems that minimize the probability of injury. To do this, the designer must have quantified knowledge of the probability of injury due to different impact scenarios and also know which model parameters contribute the most to the injury probability. Although complex numerical (e.g., finite element) models are becoming more widely used as a means of augmenting and extending laboratory testing, most are deterministic in that they do not quantify the effect of uncertainties on the computed model responses.

Summary: A probabilistic methodology and computational tool was developed for evaluating the risk of cervical spine injury and applied to several cervical spine models (see figure). The calculations were performed using the NESSUS probabilistic analysis program integrated with the commercial ABAQUS finite element program. The probabilistic methods in NESSUS, which were initially developed for aerospace applications, are broadly applicable and their use warranted in situations where uncertainty is known or believed to have a significant impact on the structural response.

Potential applications of the methodology include the study of spinal behavior under normal and distressed conditions, the design of implants utilizing novel materials and/or configurations, analysis of novel instrumentation systems that may help avoid costly experimentation, and the design of anthropomorphic test devices or physical models that replicate human response such that injury under simulated dynamic conditions can be replicated.

Key Publications:

Thacker, B.H., Y.-T Wu, D.P. Nicolella, and R.C. Anderson, "Probabilistic Cervical Spine Injury Analysis Methods," 7th ASCE Specialty Conference on Probabilistic Mechanics and Reliability, ASCE, Worcester, Massachusetts, August 7-9, 1996.

Thacker, B.H., Y.-T Wu, D.P. Nicolella, and R.C. Anderson, "Probabilistic Injury Analysis of the Cervical Spine," Proceedings of the AIAA/ASME/ASCE/AHS/ASC 38th Structures, Structural Dynamics, and Materials (SDM) Conference, Kissimmee, Florida, April 7-10, 1997.

Thacker, B.H., Y.-T. Wu, and D.P. Nicolella, "Probabilistic Model of Neck Injury," Frontiers in Head and Neck Trauma: Clinical and Biomechanical, Probabilistic Model of Neck Injury, N. Yoganandan, F.A. Pintar, S.J. Larson, and A. Sances Jr. (eds.), IOS Press, Harvard, Massachusetts, pp. 409-424, 1998.

Links:

Southwest Research Institute Biomechanics Website.