Investigating the Effect of Axial Compression and Distraction On Cervical Facet Mechanics During Supraphysiologic Anterior Shear

2021 ◽  
Author(s):  
Ryan Quarrington ◽  
John J. Costi ◽  
Brian Freeman ◽  
Claire Jones
Keyword(s):  
Axial Compression ◽  
Muscle Activation ◽  
Radiographic Appearance ◽  
Linear Mixed Effects ◽  
Axial Forces ◽  
Facet Fracture ◽  
Inertial Loading ◽  
Shear Motion ◽  
Cervical Facet ◽  
Analysis Point

Abstract Bilateral cervical facet dislocation (BFD) with facet fracture (Fx) often causes tetraplegia but is rarely recreated experimentally, possibly due to a lack of muscle replication. Intervertebral axial compression (due to muscle activation) or distraction (due to inertial loading), when combined with excessive anterior translation, may influence inter-facet contact or separation and the subsequent production of BFD with or without Fx. This paper presents a methodology to produce C6/C7 BFD+Fx using anterior shear motion superimposed with 300 N compression or 2.5 mm distraction. The effect of these superimposed axial conditions on six-axis loads, and C6 inferior facet deflections and surface strains, was assessed. Twelve motion segments (70 ± 13 yr) achieved 2.19 mm of supraphysiologic anterior shear without embedding failure (supraphysiogic shear analysis point; SSP), and BFD+Fx was produced in all five specimens that reached 20 mm of shear. Linear mixed-effects models (a=0.05) assessed the effect of axial condition. At the SSP, the compressed specimens experienced higher axial forces, facet shear strains, and sagittal facet deflections, compared to the distracted group. Facet fractures had similar radiographic appearance to those that are observed clinically, suggesting that intervertebral anterior shear motion contributes to BFD+Fx.

Design aids for rectangular reinforced concrete sections under combined bending and axial forces

1988 ◽  
Vol 15 (5) ◽  
pp. 916-928 ◽  
Author(s):  
P. Riva ◽  
M. Z. Cohn
Keyword(s):  
Reinforced Concrete ◽  
Portland Cement ◽  
Key Words ◽  
Axial Compression ◽  
Strength Analysis ◽  
Short Columns ◽  
Axial Forces ◽  
Portland Cement Association

Design interaction diagrams, Pr–Mr, for rectangular reinforced concrete sections under combined bending and axial compression or tension forces in accordance with the current Canadian code are presented. The interest of the note is that the interaction diagrams eliminate the limitations of those in the Canadian Portland Cement Association Handbook. Their format can be extended to other section shapes and reinforcement layouts. Key words: Combined bending, design aids, interaction diagrams, rectangular sections, reinforced concrete, short columns, strength analysis.

Control Mechanisms in Oscillatory Motor Behavior

2013 ◽  
Author(s):  
Davide Piovesan ◽  
Felix C. Huang
Keyword(s):  
Muscle Activation ◽  
Motor Behavior ◽  
Rhythmic Movement ◽  
Control Mechanisms ◽  
Rhythmic Movements ◽  
Movement Trajectories ◽  
Reduced Frequency ◽  
The Central Nervous System ◽  
Human Motor ◽  
Inertial Loading

Studies on unimpaired humans have demonstrated that the central nervous system employs internal representations of limb dynamics and intended movement trajectories for planning muscle activation during pointing and reaching tasks. However, when performing rhythmic movements, it has been hypothesized that a control scheme employing an autonomous oscillator — a simple feedback circuit lacking exogenous input — can maintain stable control. Here we investigate whether such simple control architectures that can realize rhythmic movement that we observe in experimental data. We asked subjects to perform rhythmic movements of the forearm while a robotic interface simulated inertial loading. Our protocol included unexpected increases in loading (catch trials) as a probe to reveal any systematic changes in frequency and amplitude. Our primary findings were that increased inertial loading resulted in reduced frequency of oscillations, and in some cases multiple frequencies. These results exhibit some agreement with an autonomous oscillator model, though other features are more consistent with feedforward planning of force. This investigation provides a theoretical and experimental framework to reveal basic computational elements for how the human motor system achieves skilled rhythmic movement.

Management of Acute Unilateral Nondisplaced Subaxial Cervical Facet Fractures

2017 ◽  
Vol 14 (2) ◽  
pp. 104-111 ◽  
Author(s):  
Aditya Vedantam ◽  
Jared Steven Fridley ◽  
Jovany Cruz Navarro ◽  
Shankar P Gopinath
Keyword(s):  
Nonoperative Management ◽  
Exact Test ◽  
Laminar Fracture ◽  
Facet Fracture ◽  
The Mean ◽  
Lateral Mass Fracture ◽  
Fracture Types ◽  
Cervical Facet ◽  
Spine Radiographs

Abstract BACKGROUND Few studies have focused on the management of patients with nondisplaced cervical facet fractures. OBJECTIVE To determine the rate of successful nonoperative management and risk factors for instability in patients with acute traumatic, unilateral, nondisplaced cervical facet fractures. METHODS We reviewed patients with single or multilevel unilateral nondisplaced or minimally displaced subaxial cervical facet fractures between 2008 and 2014. Facet fractures were classified as type A1 fractures: superior facet fracture of caudal vertebra; type A2: inferior facet fracture of rostral vertebral; and type A3: floating lateral mass (fracture of pedicle and vertical laminar fracture). All patients were given a trial of nonoperative management with external immobilization using a hard cervical collar. Follow-up clinical data and cervical spine radiographs were analyzed to determine factors associated with instability. RESULTS Thirty-five patients (34 males, mean age 40.2 ± 2.4 yr) were reviewed. The mean follow-up duration was 2.7 ± 0.4 mo. The distribution of fracture types was type A1 (n = 15), type A2 (n = 4), type A3 (n = 5), type A1 and A2 fractures (n = 10), and type A1 and A3 fractures (n = 1). Nonoperative management was successful in 29 patients (82.9%), and 6 patients developed instability requiring surgery. All patients who failed nonoperative management had associated injuries suggesting a more severe mechanism of injury. No significant association was found between the type of facet fracture and outcome (Fisher's exact test, P = .18). CONCLUSION In our series, more than 80% of the patients with unilateral, nondisplaced cervical facet fractures underwent successful nonoperative management in the short term.

3:5880. Outcomes of Operative versus Nonoperative Treatment of Unilateral Cervical Facet Fracture Subluxations

2006 ◽  
Vol 6 (5) ◽  
pp. 39S-40S
Author(s):  
Marcel Dvorak ◽  
Bizhan Aarabi ◽  
Raja Rampersaud ◽  
Mitchel Harris ◽  
Michael Fehlings ◽  
...  
Keyword(s):  
Nonoperative Treatment ◽  
Facet Fracture ◽  
Cervical Facet

Unilateral Cervical Facet Fracture-Dislocation

2020 ◽  
pp. 439-443
Author(s):  
Brian E. Kaufman ◽  
John A. Heydemann ◽  
Suken A. Shah
Keyword(s):  
Fracture Dislocation ◽  
Facet Fracture ◽  
Cervical Facet

scholarly journals Anterior-Alone Surgical Treatment for Subaxial Cervical Spine Facet Dislocation: A Systematic Review

2020 ◽  
pp. 219256822090757
Author(s):  
Wendy Lee ◽  
Chung Chek Wong
Keyword(s):  
Systematic Review ◽  
Cervical Spine ◽  
Open Reduction ◽  
Meta Analysis ◽  
Fracture Dislocation ◽  
Facet Dislocation ◽  
Subaxial Cervical Spine ◽  
Mesh Terms ◽  
Facet Fracture ◽  
Cervical Facet

Study Design: Systematic review. Objective: Anterior-alone surgery has gained wider reception for subaxial cervical spine facets dislocation. Questions remain on its efficacy and safety as a stand-alone entity within the contexts of concurrent facet fractures, unilateral versus bilateral dislocations, anterior open reduction, and old dislocation. Methods: A systematic review was performed with search strategy using translatable MESH terms across MEDLINE, EMBASE, VHL Regional Portal, and CENTRAL databases on patients with subaxial cervical dislocation intervened via anterior-alone approach. Two reviewers independently screened for eligible studies. PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) flow chart was adhered to. Nine retrospective studies were included. Narrative synthesis was performed to determine primary outcomes on spinal fusion and revisions and secondary outcomes on new occurrence or deterioration of neurology and infection rate. Results: Nonunion was not encountered across all contexts. A total of 0.86% of unilateral facet dislocation (1 out of 116) with inadequate reduction due to facet fragments between the facet joints removed its malpositioned plate following fusion. No new neurological deficit was observed. Cases that underwent anterior open reduction did not encounter failure that require subsequent posterior reduction surgery. One study (N = 52) on old dislocation incorporated partial corpectomy in their approach and limited anterior-alone approach to cases with persistent instability. Conclusions: This systematic review supports the efficacy and success of anterior reduction, fusion, and instrumentation for cervical facet fracture dislocation. It is safe from a neurological standpoint. Revision rate due to concurrent facet fracture is low. Certain patients may require posteriorly based surgery or in specific cases combined anterior and posterior procedures.

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