Cervical Spine Muscle-Tendon Unit Length Differences Between Neutral and Forward Head Postures: Biomechanical Study Using Human Cadaveric Specimens

Lesions in facet joints such as bone hyperplasia and degenerative changes in the intervertebral discs, can compress nerve roots and the spinal cord, leading to cervical spondylosis (CS). Lesions in these parts of the spine are commonly related to abnormal loads caused by bad posture of the cervical spine. This study aimed to understand the potential mechanical effects of load amplitude on cervical spine motion to provide a theoretical basis for the biomechanical causes of CS, and to provide a reference for preventing of the condition. In this study, a finite element model of the normal human cervical spine (C1-C7) was established and validated using an infrared motion capture system to analyze the effects of flexion angle on the stresses experienced by intervertebral discs, the anterior edge of the vertebral body, the pedicle, uncinate and facet joints. Our analysis indicated that the intervertebral disc load increased by at least 70% during the 20∘ to 45∘ flexion of the neck with 121% load increase in the vertebrae. In the intervertebral discs, the stress was largest at C4-C5, and the stress was moderate at C5-C6. These results are consistent with clinical CS prone site research. According to Wolff’s law, when bones are placed under large stresses, hyperplasia can result to allow adaptation to large loads. Increased cervical spine flexion angles caused the proliferation of bone in the above-mentioned parts of the spine and can accelerate accelerating the appearance of CS.

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Kinematics of a Novel Canine Cervical Fusion System

Veterinary and Comparative Orthopaedics and Traumatology ◽

10.1055/s-0041-1725016 ◽

2021 ◽

Author(s):

Claudia Zindl ◽

Noel Fitzpatrick ◽

Alan S. Litsky ◽

Matthew J. Allen

Keyword(s):

Cervical Spine ◽

Angular Displacement ◽

Biomechanical Study ◽

Fusion System ◽

Adjacent Level ◽

Four Point Bending ◽

Rod System ◽

Bending Loads ◽

Adjacent Level Effects ◽

Implant System

Abstract Objective The aim of this study was to determine the biomechanical behaviour of a novel distraction–fusion system, consisting of an intervertebral distraction screw, pedicle locking screws and connecting rods, in the canine caudal cervical spine. Study Design Biomechanical study in cadaveric canine cervicothoracic (C3–T3) spines (n = 6). Cadaveric spines were harvested, stripped of musculature, mounted on a four-point bending jig, and tested using non-destructive four-point bending loads in extension (0–100 N), flexion (0–60 N) and lateral bending (0–40 N). Angular displacement was recorded from reflective optical trackers rigidly secured to C5, C6 and C7. Data for primary and coupled motions were collected from intact spines and following surgical stabilization (after ventral annulotomy and nucleotomy) with the new implant system. Results As compared with the intact spine, instrumentation significantly reduced motion at the operated level (C5-C6) with a concomitant non-significant increase at the adjacent level (C6-C7). Conclusion The combination of a locking pedicle screw-rod system and intervertebral spacer provides an alternative solution for surgical distraction–stabilization in the canine caudal cervical spine and supports the feasibility of using this new implant system in the management of disc-associated cervical spondylomyelopathy in dogs. The increase in motion at C6-C7 may suggest the potential for adjacent level effects and clinical trials should be designed to address this.

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The role of cervical collars and verbal instructions in minimising spinal movement during self-extrication following a motor vehicle collision - a biomechanical study using healthy volunteers

Scandinavian Journal of Trauma Resuscitation and Emergency Medicine ◽

10.1186/s13049-021-00919-w ◽

2021 ◽

Vol 29 (1) ◽

Author(s):

Tim Nutbeam ◽

Rob Fenwick ◽

Barbara May ◽

Willem Stassen ◽

Jason E. Smith ◽

...

Keyword(s):

Cervical Spine ◽

Lumbar Spine ◽

Healthy Volunteers ◽

Motion Tracking ◽

Motor Vehicle ◽

Biomechanical Study ◽

Cervical Collar ◽

Vehicle Collision ◽

Spinal Movement ◽

Total Movement

Abstract Background Motor vehicle collisions account for 1.3 million deaths and 50 million serious injuries worldwide each year. However, the majority of people involved in such incidents are uninjured or have injuries which do not prevent them exiting the vehicle. Self-extrication is the process by which a casualty is instructed to leave their vehicle and completes this with minimal or no assistance. Self-extrication may offer a number of patient and system-wide benefits. The efficacy of routine cervical collar application for this group is unclear and previous studies have demonstrated inconsistent results. It is unknown whether scripted instructions given to casualties on how to exit the vehicle would offer any additional utility. The aim of this study was to evaluate the effect of cervical collars and instructions on spinal movements during self-extrication from a vehicle, using novel motion tracking technology. Methods Biomechanical data on extrications were collected using Inertial Measurement Units on 10 healthy volunteers. The different extrication types examined were: i) No instructions and no cervical collar, ii) No instructions, with cervical collar, iii) With instructions and no collar, and iv) With instructions and with collar. Measurements were recorded at the cervical and lumbar spine, and in the anteroposterior (AP) and lateral (LAT) planes. Total movement, mean, standard deviation and confidence intervals are reported for each extrication type. Results Data were recorded for 392 extrications. The smallest cervical spine movements were recorded when a collar was applied and no instructions were given: mean 6.9 mm AP and 4.4 mm LAT. This also produced the smallest movements at the lumbar spine with a mean of 122 mm AP and 72.5 mm LAT. The largest overall movements were seen in the cervical spine AP when no instructions and no collar were used (28.3 mm). For cervical spine lateral movements, no collar but with instructions produced the greatest movement (18.5 mm). For the lumbar spine, the greatest movement was recorded when instructions were given and no collar was used (153.5 mm AP, 101.1 mm LAT). Conclusions Across all participants, the most frequently occurring extrication method associated with the least movement was no instructions, with a cervical collar in situ.

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The biomechanical study of cervical spine: A Finite Element Analysis

The International Journal of Artificial Organs ◽

10.1177/0391398821995495 ◽

2021 ◽

pp. 039139882199549

Author(s):

Pechimuthu Susai Manickam ◽

Sandipan Roy

Keyword(s):

Finite Element ◽

Cervical Spine ◽

Degrees Of Freedom ◽

Three Dimensional ◽

Biomechanical Study ◽

Fe Analysis ◽

Von Mises Stress ◽

Fe Model ◽

Element Analysis ◽

End Plate

The biomechanical study helps us to understand the mechanics of the human cervical spine. A three dimensional Finite Element (FE) model for C3 to C6 level was developed using computed tomography (CT) scan data to study the mechanical behaviour of the cervical spine. A moment of 1 Nm was applied at the top of C3 vertebral end plate and all degrees of freedom of bottom end plate of C6 were constrained. The physiological motion of the cervical spine was validated using published experimental and FE analysis results. The von Mises stress distribution across the intervertebral disc was calculated along with range of motion. It was observed that the predicted results of functional spine units using FE analysis replicate the real behaviour of the cervical spine.

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