Complex Neck Loading and Injury Tolerance in Lateral Bending With Head Rotation From Human Cadaver Tests

Advancements in automated vehicles may position the occupant in postures different from the current standard posture. It may affect human tolerance responses. The objective of this study was to determine the lateral bending tolerance of the head-cervical spine with initial head rotation posture using loads at the occipital condyles and lower neck and describe injuries. Using a custom loading device, head-cervical spine complexes from human cadavers were prepared with load cells at the ends. Lateral bending loads were applied to prerotated specimens at 1.5 m/s. At the occipital condyles, peak axial and antero-posterior and medial-lateral shear forces were: 316-954 N, 176-254 N, and 327-508 N, and coronal, sagittal, and axial moments were: 27-38 N·m, 21-38 N·m, and 9.7-19.8 N·m, respectively. At the lower neck, peak axial and shear forces were: 677-1004 N, 115-227 N, and 178-350 N, and coronal, sagittal, and axial moments were: 30-39 N·m, 7.6-21.3 N·m, and 5.7-13.4 N·m, respectively. Ipsilateral atlas lateral mass fractures occurred in four out of five specimens with varying joint diastasis and capsular ligament involvements. Acknowledging that the study used a small sample size, initial tolerances at the occipital condyles and lower neck were estimated using survival analysis. Injury patterns with posture variations are discussed.