265 - Variations among Human Spine Segments and Their Relationships to in vi...

General Session: Biomechanics - Hall F

Presented by: A. Newcomb


A. Newcomb(1), J. Lehrman(1), N. Crawford(1), B. Kelly(1)

(1) Barrow Neurological Institute, Spinal Biomechanics Lab, Phoenix, AZ, United States


Introduction: Kinematic data from cadaveric tests are often used to validate finite element models. However, data describing relationships between motion segment features (i.e. subject height, BMD) and kinematics are lacking. The objective with this study was to retrospectively investigate the relationships between cadaveric cervical spinal motion segments and their biomechanical characteristics (ROM), including coupled motion.

Methods: Spine tissue donor information (age, gender, height and weight at time of death) was provided by local tissue banks. Bone mineral densities (BMD) were obtained at C4. 581 cadaveric cervical motion segments (between C1 and T1) from 147 donor spines [86 M/61 F, range: 20-69 yrs, mean age 53.5±10.6 yrs, BMD 0.558±0.101 g/cm2, mean height 173.4±12.0 cm] were included. Kinematic data (ROM in flexion-extension [FE], lateral bending [LB] and axial rotation [AR], including coupled motion [CM] (i.e. LB during AR and AR during LB) were retrieved from studies involving intact testing of the cervical spine segments, with all tests performed in one lab and using the same methods. In short, pure moment loads (1.5 Nm) were applied while measuring intervertebral rotations in 3D. Relationships between subject height, weight, gender, BMD and kinematic data (ROM, CM LB/AR and CM AR/LB) were studied using Pearson correlation and multiple regression analyses (p< 0.05).

Results: Values for ROM [Figure 1] were within typical ranges as reported in the literature. There were significant negative correlations between BMD and ROM, starting at C4-C5 and continuing caudally (R< -0.18, P< 0.02) . Other significant correlations with ROM include: cervical level [all directions of motion: R< -0.18, P< 0.001)], age [LB: R=-0.11, P< 0.009], gender [FL-EX and LB: M< F, P< 0.001], weight [FL-EX and LB: R=-0.10, P< 0.02], height [FL-EX and LB: R< -0.13, P< 0.003], and BMI [LB: R=-0.132, P=0.004]. There were significant correlations between both CMs and cervical level [Figure 2], with AR/LB decreasing caudally and LB/AR following the trend of primary motion ratios (LB÷AR). There were no correlations between CM and donor information (P>0.4). Multiple linear regression analysis showed that ROM of cervical motion segments can be predicted using relationships between subject cervical level, gender, age, weight and/or BMD [FL-EX: R = 0.321, P< 0.001;AR: R = 0.643, P< 0.001; and LB: R = 0.535, P< 0.001].

Discussion: Significant relationships exist between cervical spine segments' BMD and biomechanical properties (ROM and CM) at mid- and lower cervical levels. These relationships are of value during the validation process of finite element models involving human cervical spine segments, especially in studies focusing on motion preservation.

Figure 1

Figure 2