Biomechanical evaluation of the New Zealand white rabbit lumbar spine: a physiologic characterization

Abstract

IntroductionThere are many variables that affect the results of lumbar fusions. Particularly with the advent of novel methods of instrumentation and the purification of bone-stimulating growth factors, the orthopedic surgeon is faced with many surgical options. Objective comparison of these many variables is imperative. Not only must existing fusion modalities be critically evaluated, but novel modalities must also be compared to those already in use.Outcome studies are an ideal way to compare the efficacy of fusions. However, it is difficult to normalize study groups in this type of clinical trial. Furthermore, baseline Abstract Physiologic motions of the human, sheep, and calf lumbar spines have been well characterized. The size, cost, and ease of care all make the rabbit an attractive alternative choice for an animal lumbar spine model. However, comparisons of normal biomechanical characteristics of the rabbit lumbar spine have not been made to the spines of larger species. The purpose of this study was to establish baseline physiologic kinematic data for the rabbit lumbar spine. Ten skeletally mature New Zealand white rabbit osteoligamentous spines were obtained. L4-L7 spine segments were harvested and mounted. Multi-directional flexibility testing was performed by applying pure moments up to 0.27 Nm. Resulting rotations were measured using an Optotrak system. Data were analyzed for each intervertebral level in the three planes of rotation. The three levels tested had roughly similar range of motion (ROM). The mean (SD) angular ROMs in flexion for L4-L5, L5-L6, L6-L7 were 12.10°(2.59°), 12.38°(2.70°), and 15.17°(3.22°), respectively. The ROMs in extension were 5.86°(

A novel application of velocity-based force control for use in robotic biomechanical testing

“…The range of motion of our single test specimen compares well with the data from Grauer et al (2000). Both studies tested to 0.27 N m and our L3-4 motion segment had 10.61 in flexion and 5.01 in extension compared to respective means of 12.11 and 5.91 for L4-5 in their study.…”

“…Both studies tested to 0.27 N m and our L3-4 motion segment had 10.61 in flexion and 5.01 in extension compared to respective means of 12.11 and 5.91 for L4-5 in their study. In our study, the total neutral zone was 1.11 compared to 13.81 in the Grauer et al (2000) study. One explanation for this large difference may be that the inherent properties of a stepwise loading protocol result in a larger neutral zone than a continuous loading protocol (Goertzen et al, 2004).…”

“…Higher RMS errors were seen in the axial force direction and this is likely due to the greater stiffness in this direction compared to the anterior and lateral directions. The rabbit spine testing described by Grauer et al (2000) did not use a robot and forces and moments in the unconstrained directions were not given. Walker and Dickey (2007) reported on a custom-built parallel robot used to test porcine lumbar spines to 15 N m in flexion-extension and forces were controlled to within 725 N of their zero targets.…”

“…1b). This in vitro test was performed at a constant 0.251/s (JogSpeed) in flexion-extension for three complete cycles reversing direction at 70.27 N m (Grauer et al, 2000). The JogVector parameter corresponding to the position controlled axis (R y ) was set to either +1 (extension) or À1 (flexion).…”

Tissue Engineering Strategies in Spinal Arthrodesis: The Clinical Imperative and Challenges to Clinical Translation

“…The biological graft healing environment accurately reflects that of humans, as evidenced by comparable nonunion rates using autograft [122,123]. In addition, studies have shown the rabbit lumbar spine exhibits a similar physiological range of motion to the human spine [124] with kinematic characteristics that are useful for the evaluation of posterolateral spinal fusion [125]. However, the model has a number of limitations:…”