Validation and application of a novel in vivo cervical spine kinematics analysis technique

To validate the accuracy of Cone beam computed tomography (CBCT) cervical spine modeling with three dimensional (3D)-3D registration for in vivo measurements of cervical spine kinematics. CBCT model accuracy was validated by superimposition with computed tomography (CT) models in 10 healthy young adults, and then cervical vertebrae were registered in six end positions of functional movements, versus a neutral position, in 5 healthy young adults. Registration errors and six degrees of freedom (6-DOF) kinematics were calculated and reported. Relative to CT models, mean deviations of the CBCT models were < 0.6 mm. Mean registration errors between end positions and the reference neutral position were < 0.7 mm. During flexion–extension (F–E), the translation in the three directions was small, mostly < 1 mm, with coupled LB and AR both < 1°. During lateral bending (LB), the bending was distributed roughly evenly, with coupled axial rotation (AR) opposite to the LB at C1–C2, and minimal coupled F–E. During AR, most of the rotation occurred in the C1–C2 segment (29.93 ± 7.19° in left twist and 31.38 ± 8.49° in right twist) and coupled LB was observed in the direction opposite to that of the AR. Model matching demonstrated submillimeter accuracy in cervical spine kinematics data. The presently evaluated low-radiation-dose CBCT technique can be used to measure 3D spine kinematics in vivo across functional F–E, AR, and LB positions, which has been especially challenging for the upper cervical spine.

Biomechanics of Lumbar Spine Injury in Road Barrier Collision–Finite Element Study

Literature and field data from CIREN database have shown that lumbar spine injuries occur during car crashes. There are multiple hypotheses regarding how they occur; however, there is no biomechanical explanation for these injuries during collisions with road safety barriers (RSBs). Therefore, the objective of this study was to investigate the mechanics of vertebral fractures during car collisions with concrete RSBs. The finite element method was used for the numerical simulations. The global model of the car collision with the concrete RSB was created. The lumbar spine kinematics were extracted from the global simulation and then applied as boundary conditions to the detailed lumbar spine model. The results showed that during the collision, the occupant was elevated, and then dropped during the vehicle landing. This resulted in axial compression forces 2.6 kN with flexion bending moments 34.7 and 37.8 Nm in the L2 and L3 vertebrae. It was shown that the bending moment is the result of the longitudinal force on the eccentricity. The lumbar spine index for the L1–L5 section was 2.80, thus indicating a lumbar spine fracture. The minimum principal strain criterion of 7.4% and damage variable indicated L2 and L3 vertebrae and the inferior part of L1, as those potentially prone to fracture. This study found that lumbar spine fractures could occur as a consequence of vehicle landing during a collision with a concrete RSB mostly affecting the L1–L3 lumbar spine section. The fracture was caused by a combination of axial forces and flexion bending moments.

Subject-Specific Spino-Pelvic Models Reliably Measure Spinal Kinematics During Seated Forward Bending in Adult Spinal Deformity

Image-based subject-specific models and simulations are recently being introduced to complement current state-of-the-art mostly static insights of the adult spinal deformity (ASD) pathology and improve the often poor surgical outcomes. Although the accuracy of a recently developed subject-specific modeling and simulation framework has already been quantified, its reliability to perform marker-driven kinematic analyses has not yet been investigated. The aim of this work was to evaluate the reliability of this subject-specific framework to measure spine kinematics in ASD patients, in terms of 1) the overall test-retest repeatability; 2) the inter-operator agreement of spine kinematic estimates; and, 3) the uncertainty of those spine kinematics to operator-dependent parameters of the framework. To evaluate the overall repeatability 1], four ASD subjects and one control subject participated in a test-retest study with a 2-week interval. At both time instances, subject-specific spino-pelvic models were created by one operator to simulate a recorded forward trunk flexion motion. Next, to evaluate inter-operator agreement 2], three trained operators each created a model for three ASD subjects to simulate the same forward trunk flexion motion. Intraclass correlation coefficients (ICC’s) of the range of motion (ROM) of conventional spino-pelvic parameters [lumbar lordosis (LL), sagittal vertical axis (SVA), thoracic kyphosis (TK), pelvic tilt (PT), T1-and T9-spino-pelvic inclination (T1/T9-SPI)] were used to evaluate kinematic reliability 1] and inter-operator agreement 2]. Lastly, a Monte-Carlo probabilistic simulation was used to evaluate the uncertainty of the intervertebral joint kinematics to operator variability in the framework, for three ASD subjects 3]. LL, SVA, and T1/T9-SPI had an excellent test-retest reliability for the ROM, while TK and PT did not. Inter-operator agreement was excellent, with ICC values higher than test-retest reliability. These results indicate that operator-induced uncertainty has a limited impact on kinematic simulations of spine flexion, while test-retest reliability has a much higher variability. The definition of the intervertebral joints in the framework was identified as the most sensitive operator-dependent parameter. Nevertheless, intervertebral joint estimations had small mean 90% confidence intervals (1.04°–1.75°). This work will contribute to understanding the limitations of kinematic simulations in ASD patients, thus leading to a better evaluation of future hypotheses.

THE EFFECTS OF DYNAMIC NEUROMUSCULAR STABILITY EXERCISE ON THE SCOLIOSIS AND PAIN CONTROL IN THE YOUTH BASEBALL PLAYERS

While the presence of dynamic neuromuscular stabilization (DNS) has been provided as an important component of the integrated spinal stabilization and associated abdominal stabilization prior to dynamic movement, no previous study has investigated the spinal mechanical effects scoliosis and pain control in youth baseball player with scoliosis. This study compared the effects of gymball exercise, with and without DNS core stability exercise, on spine kinematics and pain control in youth baseball player with scoliosis. A total of 28 participants with scoliosis were randomized into gymball exercise, with and without DNS core stability exercise. Clinical outcomes included the Cobb’s angle and visual analog scale (VAS). Two-way repeated analysis of variance (ANOVA) was conducted at [Formula: see text]. Two-way repeated ANOVA showed that gymball with DNS showed superior effects, compared to gymball without DNS, on Cobb’s angle ([Formula: see text]), but not on VAS ([Formula: see text]). Our results provide novel, promising clinical evidence that DNS improved scoliosis kinematics as well as pain control in youth baseball player with scoliosis.

Impact of corset bracing on 3D spine kinematics during ADL in children with Spondylolysis

Spondylolysis is a stress fracture of the vertebral pars interarticularis that frequently affects adolescents involved in sports. Conservative bracing methods may assist the clinician in treating spondylolysis, though there is a need to further validate these techniques. The goal of this study was to evaluate differences in the 3D movements of the thoracic and lumbar spine before and after bracing. Five patients (mean age 14.4 ± 1.3 years) with spondylogenic back pain were evaluated for kinematic measurements using a Vicon motion capture system. Patients performed activities both with and without a lumbar corset brace including walking, kneeling, standing from a chair, standing from the floor, ascending and descending stairs, and lifting. Patients were evaluated for differences in thoracic and lumbar range of motion (ROM) in the braced and unbraced condition. While wearing the brace, patients demonstrated reduced extension ROM of the thoracic spine while walking (mean reduction = 0.4°), ascending stairs (3.0°), descending stairs (2.1°), lifting (14.8°), standing from a chair (4.1°), standing from the floor (16.7°), and kneeling (8.4°). Patients also exhibited reduced extension ROM of the total lumbar spine while ascending stairs (mean reduction = 1.8°), lifting (12.7°), standing from a chair (9.5°), standing from the floor (11.8°), and kneeling (4.7°). These results provide evidence that bracing reduces stress on the pars interarticularis and relieves symptoms in the athlete with spondylogenic back pain, thereby facilitating a return to sports.