Variations Among Human Lumbar Spine Segments and Their Relationships to In Vitro Biomechanics: A Retrospective Analysis of 281 Motion Segments From 85 Cadaveric Spines

Abstract

Background: Biomechanical properties of intact spinal motion segments are used to establish baseline values during in vitro studies evaluating spinal surgical techniques and implants. These properties are also used to validate computational models (ie, patient-specific finite element models) of human lumbar spine segments. Our laboratory has performed a large number of in vitro mechanical studies of lumbar spinal segments, using a consistent methodology. This provides extensive biomechanical data for a large number of intact motion segments, along with donor demographic variables, bone mineral density (BMD) measurements, and geometric properties. The objective of this study was to analyze how donor demographics, BMD, and geometric properties of cadaveric lumbar spine segments affect motion segment flexibility, including the range of motion (ROM), lax zone (LZ), and stiff zone (SZ), to help improve our understanding of spinal biomechanics.Methods: A retrospective study examined the relationships between the biomechanical properties of 281 lumbar motion segments from 85 human cadaveric spines, donor demographic variables (age, sex, weight, height, and body mass index), and specimen measurements (vertebral body height, intervertebral disc height, and BMD).Results: Statistical correlation and regression analyses showed that the flexibility of a lumbar motion segment is affected by lumbar level, donor age, sex, and weight as well as the intervertebral disc height, vertebral body height, and bone quality. Increased disc height was associated with decreased ROM (axial rotation), decreased LZ (flexionextension and axial rotation), and increased SZ (flexion-extension and lateral bending) in the male group, but increased ROM (lateral bending) in the female group. Increased vertebral body height correlated with increased LZ (lateral bending) in the female group. Increased BMD correlated with decreased ROM overall.Conclusions: Biomechanical measurements from flexibility testing of cadaveric lumbar spine segments are significantly correlated with donor demographics and specimen measurements. Many of these correlations are sexdependent. Biomechanics

In Vitro Biomechanics of Human Cadaveric Cervical Spines With Mature Fusion

“…Both of the above-mentioned retrospective studies conducted in our laboratory generally demonstrated no significant correlation between ROM and specimen age, 26,27 but significant negative correlations in ROM with increased BMD in both lumbar (P .04) and cervical (P .01) spines in FE and LB. The SZ was significantly negatively correlated with increased age in both spine regions in FE (P , .001) and LB (P , .001) but not with BMD.…”

“…Patients who require spine surgery often have low BMD as a consequence of older age. 25 Previously our laboratory retrospectively studied the relationship between parameters including age, BMD, ROM, LZ, and SZ in 285 intact cadaveric lumbar motion segments 26 and in 581 intact cervical cadaveric motion segments. Both studies observed a significant negative correlation between BMD and increased age (P .02).…”

Biomechanical Evaluation of Oblique Lateral Locking Plate System for Oblique Lumbar Interbody Fusion: A Finite Element Analysis

“…However, the realistic human lumbar spine does not have 100% symmetry, and the mobility and stress can vary. 25 Therefore, the results of the lumbar spine in exion, extension, left bending, right bending, left rotation, and right rotation were recorded separately in this study.…”

Automated Pipeline to Generate Anatomically Accurate Patient-Specific Biomechanical Models of Healthy and Pathological FSUs

“…The lack of patient-specific material properties may influence the resulting ROMs. Different studies have shown how much biomechanical parameters vary between subjects ( Van Rijsbergen et al, 2018 ; Sawa et al, 2020 ; Wawrose et al, 2020 ) and how the ROM is affected by these variations. The ROMs reported in this work were partially out of range as compared to other studies ( Dreischarf et al, 2014 ).…”