Robotic Simulation of an Eccentric Lever Arm Protocol and a Novel Head Weight Protocol for Evaluation of the Subaxial Cervical Spine: An In Vitro Biomechancial Comparison

2011 ◽  
Author(s):  
Daniel M. Wido ◽  
Denis J. DiAngelo ◽  
Brian P. Kelly
Keyword(s):  
Cervical Spine ◽  
Muscle Activation ◽  
Vertical Force ◽  
Follower Load ◽  
Testing Platform ◽  
Lever Arm ◽  
Subaxial Cervical Spine ◽  
Head Weight ◽  
Robotic Testing

In vitro testing provides a critical tool for understanding the biomechanics of the subaxial cervical spine. Previous common testing protocols used to evaluate the subaxial cervical spine include pure moment, follower load, and eccentric lever arm (EL) loading methods [1,2,3]. Although these methods are widely accepted, there is always a goal to try to better simulate physiologic loading conditions. While the follower load attempts to simulate compression due to muscle activation, no previous protocol has taken into account the constant vertical force vector applied to C2 produced by the weight of the human head. Furthermore, we are unaware of previous direct protocol to protocol comparisons using the same testing platform and test specimens. Our multi-axis programmable robotic testing platform (Spine Robot) provides the means to explore such comparisons. The objectives of this study were: 1) to develop a novel head weight influenced loading protocol (HWL), 2) simulate and compare the EL protocol and the HWL protocol on a single programmable robotic testing frame with a consistent specimen sample group.

Use of Spine Robot Employing Real Time Force Control to Simulate a Pure Moment Protocol for the Subaxial Cervical Spine: An In Vitro Biomechancial Study

2011 ◽  
Author(s):  
Daniel M. Wido ◽  
Denis J. DiAngelo ◽  
Brian P. Kelly
Keyword(s):  
Cervical Spine ◽  
Real Time ◽  
Force Control ◽  
Biomechanical Testing ◽  
Subaxial Cervical Spine ◽  
Experimental Artifact ◽  
Pure Moment ◽  
Robotic Testing ◽  
Spine Robot

A standard biomechanical testing protocol for evaluation of the sub-axial cervical spine is the application of pure bending moments to the free end of the spine (with opposing end fixed) and measurement of its motion response. The pure moment protocol is often used to compare spinal fusion instrumentation and has also been used to evaluate non-fusion instrumentation (e.g. disc arthroplasty devices) [1,2]. A variety of different testing systems have been employed to implement pure moment application. In cases where the loading is applied quasi-statically using a series of weights and pulleys the spine may relax between intermittent loading phases and/or unintended loading may be applied causing experimental artifact. Our objective was to use an existing programmable robotic testing platform (Spine Robot) to develop a novel real time force control strategy to simulate pure moment loading under precisely controlled continuous movement conditions. This would serve to advance robotic testing capabilities with an end goal to simulate different protocols in the same platform, and to potentially minimize fixturing and quasi-static artifacts.

Compressive Follower Load Influences Cervical Spine Kinematics and Kinetics During Simulated Head-First Impact in an in Vitro Model

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Amy Saari ◽  
Christopher R. Dennison ◽  
Qingan Zhu ◽  
Timothy S. Nelson ◽  
Philip Morley ◽  
...  
Keyword(s):  
Cervical Spine ◽  
Injury Risk ◽  
Muscle Activation ◽  
Ex Vivo ◽  
Reaction Force ◽  
Experimental Studies ◽  
Follower Load ◽  
Muscle Forces

Current understanding of the biomechanics of cervical spine injuries in head-first impact is based on decades of epidemiology, mathematical models, and in vitro experimental studies. Recent mathematical modeling suggests that muscle activation and muscle forces influence injury risk and mechanics in head-first impact. It is also known that muscle forces are central to the overall physiologic stability of the cervical spine. Despite this knowledge, the vast majority of in vitro head-first impact models do not incorporate musculature. We hypothesize that the simulation of the stabilizing mechanisms of musculature during head-first osteoligamentous cervical spine experiments will influence the resulting kinematics and injury mechanisms. Therefore, the objective of this study was to document differences in the kinematics, kinetics, and injuries of ex vivo osteoligamentous human cervical spine and surrogate head complexes that were instrumented with simulated musculature relative to specimens that were not instrumented with musculature. We simulated a head-first impact (3 m/s impact speed) using cervical spines and surrogate head specimens (n = 12). Six spines were instrumented with a follower load to simulate in vivo compressive muscle forces, while six were not. The principal finding was that the axial coupling of the cervical column between the head and the base of the cervical spine (T1) was increased in specimens with follower load. Increased axial coupling was indicated by a significantly reduced time between head impact and peak neck reaction force (p = 0.004) (and time to injury (p = 0.009)) in complexes with follower load relative to complexes without follower load. Kinematic reconstruction of vertebral motions indicated that all specimens experienced hyperextension and the spectrum of injuries in all specimens were consistent with a primary hyperextension injury mechanism. These preliminary results suggest that simulating follower load that may be similar to in vivo muscle forces results in significantly different impact kinetics than in similar biomechanical tests where musculature is not simulated.

Analysis of adjacent-segment cervical kinematics: the role of construct length and the dorsal ligamentous complex

2020 ◽  
Vol 32 (1) ◽  
pp. 15-22
Author(s):  
Daniel Lubelski ◽  
Andrew T. Healy ◽  
Prasath Mageswaran ◽  
Robb Colbrunn ◽  
Richard P. Schlenk
Keyword(s):  
Cervical Spine ◽  
Industrial Robot ◽  
Adjacent Segment ◽  
Segmental Motion ◽  
Lateral Mass ◽  
Subaxial Cervical Spine ◽  
Flexion Extension ◽  
Cervical Kinematics

OBJECTIVELateral mass fixation stabilizes the cervical spine while causing minimal morbidity and resulting in high fusion rates. Still, with 2 years of follow-up, approximately 6% of patients who have undergone posterior cervical fusion have worsening kyphosis or symptomatic adjacent-segment disease. Based on the length of the construct, the question of whether to extend the fixation system to undisrupted levels has not been answered for the cervical spine. The authors conducted a study to quantify the role of construct length and the terminal dorsal ligamentous complex in the adjacent-segment kinematics of the subaxial cervical spine.METHODSIn vitro flexibility testing was performed using 6 human cadaveric specimens (C2–T8), with the upper thoracic rib cage and osseous and ligamentous integrity intact. An industrial robot was used to apply pure moments and to measure segmental motion at each level. The authors tested the intact state, followed by 9 postsurgical permutations of laminectomy and lateral mass fixation spanning C2 to C7.RESULTSConstructs spanning a single level exerted no significant effects on immediate adjacent-segment motion. The addition of a second immobilized segment, however, created significant changes in flexion-extension range of motion at the supradjacent level (+164%). Regardless of construct length, resection of the terminal dorsal ligaments did not greatly affect adjacent-level motion except at C2–3 and C7–T1 (increasing by +794% and +607%, respectively).CONCLUSIONSDorsal ligamentous support was found to contribute significant stability to the C2–3 and C7–T1 segments only. Construct length was found to play a significant role when fixating two or more segments. The addition of a fused segment to support an undisrupted cervical level is not suggested by the present data, except potentially at C2–3 and C7–T1. The study findings emphasize the importance of the C2–3 segment and its dorsal support.

Rheumatoid Pannus Presenting as a Large Epidural Mass in the Subaxial Cervical Spine: A Case Report

2021 ◽  
Author(s):  
Nathan K Leclair ◽  
Joshua Knopf ◽  
Michael Baldwin ◽  
Faripour Forouhar ◽  
Hilary Onyiuke
Keyword(s):  
Case Report ◽  
Cervical Spine ◽  
Subaxial Cervical Spine

The Effectiveness of a Hinged Elbow Orthosis in Medial Collateral Ligament Injuries: An In Vitro Biomechanical Study

2019 ◽  
Vol 47 (12) ◽  
pp. 2827-2835
Author(s):  
Ranita H.K. Manocha ◽  
James A. Johnson ◽  
Graham J.W. King
Keyword(s):  
Medial Collateral Ligament ◽  
Muscle Activation ◽  
Mechanical Stability ◽  
Biomechanical Study ◽  
Return To Play ◽  
Collateral Ligament ◽  
Valgus Stress ◽  
Active Motion ◽  
Early Return

Background: Medial collateral ligament (MCL) injuries are common after elbow trauma and in overhead throwing athletes. A hinged elbow orthosis (HEO) is often used to protect the elbow from valgus stress early after injury and during early return to play. However, there is minimal evidence regarding the efficacy of these orthoses in controlling instability and their influence on long-term clinical outcomes. Purpose: (1) To quantify the effect of an HEO on elbow stability after simulated MCL injury. (2) To determine whether arm position, forearm rotation, and muscle activation influence the effectiveness of an HEO. Study Design: Controlled laboratory study. Methods: Seven cadaveric upper extremity specimens were tested in a custom simulator that enabled elbow motion via computer-controlled actuators and motors attached to relevant tendons. Specimens were examined in 2 arm positions (dependent, valgus) and 2 forearm positions (pronation, supination) during passive and simulated active elbow flexion while unbraced and then while braced with an HEO. Testing was performed in intact elbows and repeated after simulated MCL injury. An electromagnetic tracking device measured valgus angulation as an indicator of elbow stability. Results: When the arm was dependent, the HEO increased valgus angle with the forearm in pronation (+1.0°± 0.2°, P = .003) and supination (+1.5°± 0.0°, P = .006) during active motion. It had no significant effect on elbow stability during passive motion. In the valgus position, the HEO had no effect on elbow stability during passive or active motion in pronation and supination. With the arm in the valgus position with the HEO, muscle activation reduced instability during pronation (–10.3°± 2.5°, P = .006) but not supination ( P = .61). Conclusion: In this in vitro study, this HEO did not enhance mechanical stability when the arm was in the valgus and dependent positions after MCL injury. Clinical Relevance: After MCL injury, an HEO likely does not provide mechanical elbow stability during rehabilitative exercises or when the elbow is subjected to valgus stress such as occurs during throwing.

Allograft Bone Use in Pediatric Subaxial Cervical Spine Fusions

2017 ◽  
Vol 37 (2) ◽  
pp. e140-e144 ◽  
Author(s):  
Robert F. Murphy ◽  
Michael P. Glotzbecker ◽  
Michael T. Hresko ◽  
Daniel Hedequist
Keyword(s):  
Cervical Spine ◽  
Allograft Bone ◽  
Subaxial Cervical Spine

Morphological Evaluation of the Subaxial Cervical Spine in Patients with Basilar Invagination

Spine ◽  
2021 ◽  
Vol Publish Ahead of Print ◽  
Author(s):  
Shaoyi Lin ◽  
Minggui Bao ◽  
Zihan Wang ◽  
Xiaobao Zou ◽  
Su Ge ◽  
...  
Keyword(s):  
Cervical Spine ◽  
Basilar Invagination ◽  
Subaxial Cervical Spine ◽  
Morphological Evaluation
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