scholarly journals Intubation biomechanics: laryngoscope force and cervical spine motion during intubation in cadavers—effect of severe distractive-flexion injury on C3–4 motion

2016 ◽  
Vol 25 (5) ◽  
pp. 545-555 ◽  
Author(s):  
Bradley J. Hindman ◽  
Ricardo B. Fontes ◽  
Robert P. From ◽  
Vincent C. Traynelis ◽  
Michael M. Todd ◽  
...  
Keyword(s):  
Cervical Spine ◽  
Macintosh Laryngoscope ◽  
Line Of Sight ◽  
Force Line ◽  
Cord Injury ◽  
Spine Motion ◽  
Cervical Segment ◽  
Posterior Subluxation ◽  
Flexion Injury ◽  
Anterior Posterior

OBJECTIVE With application of the forces of intubation, injured (unstable) cervical segments may move more than they normally do, which can result in spinal cord injury. The authors tested whether, during endotracheal intubation, intervertebral motion of an injured C3–4 cervical segment 1) is greater than that in the intact (stable) state and 2) differs when a high- or low-force laryngoscope is used. METHODS Fourteen cadavers underwent 3 intubations using force-sensing laryngoscopes while simultaneous cervical spine motion was recorded with lateral fluoroscopy. The first intubation was performed with an intact cervical spine and a conventional high-force line-of-sight Macintosh laryngoscope. After creation of a severe C3–4 distractive-flexion injury, 2 additional intubations were performed, one with the Macintosh laryngoscope and the other with a low-force indirect video laryngoscope (Airtraq), used in random order. RESULTS During Macintosh intubations, between the intact and the injured conditions, C3–4 extension (0.3° ± 3.0° vs 0.4° ± 2.7°, respectively; p = 0.9515) and anterior-posterior subluxation (−0.1 ± 0.4 mm vs −0.3 ± 0.6 mm, respectively; p = 0.2754) did not differ. During Macintosh and Airtraq intubations with an injured C3–4 segment, despite a large difference in applied force between the 2 laryngoscopes, segmental extension (0.4° ± 2.7° vs 0.3° ± 3.3°, respectively; p = 0.8077) and anterior-posterior subluxation (0.3 ± 0.6 mm vs 0.0 ± 0.7 mm, respectively; p = 0.3203) did not differ. CONCLUSIONS The authors' hypotheses regarding the relationship between laryngoscope force and the motion of an injured cervical segment were not confirmed. Motion-force relationships (biomechanics) of injured cervical intervertebral segments during endotracheal intubation in cadavers are not predicted by the in vitro biomechanical behavior of isolated cervical segments. With the limitations inherent to cadaveric studies, the results of this study suggest that not all forms of cervical spine injury are at risk for pathological motion and cervical cord injury during conventional high-force line-of-sight intubation.

scholarly journals Cervical spine motion: a fluoroscopic comparison of Shikani Optical Stylet® vs Macintosh laryngoscope

2007 ◽  
Vol 54 (6) ◽  
pp. 441-447 ◽  
Author(s):  
Timothy P. Turkstra ◽  
David M. Pelz ◽  
A. Allison Shaikh ◽  
Rosemary A. Craen
Keyword(s):  
Cervical Spine ◽  
Macintosh Laryngoscope ◽  
Spine Motion

Intubation biomechanics: validation of a finite element model of cervical spine motion during endotracheal intubation in intact and injured conditions

2018 ◽  
Vol 28 (1) ◽  
pp. 10-22 ◽  
Author(s):  
Benjamin C. Gadomski ◽  
Snehal S. Shetye ◽  
Bradley J. Hindman ◽  
Franklin Dexter ◽  
Brandon G. Santoni ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Finite Element ◽  
Cervical Spine ◽  
Endotracheal Intubation ◽  
Macintosh Laryngoscope ◽  
Element Model ◽  
Fe Model ◽  
Intervertebral Motion ◽  
Model Predictions ◽  
Spine Motion

OBJECTIVEBecause of limitations inherent to cadaver models of endotracheal intubation, the authors’ group developed a finite element (FE) model of the human cervical spine and spinal cord. Their aims were to 1) compare FE model predictions of intervertebral motion during intubation with intervertebral motion measured in patients with intact cervical spines and in cadavers with spine injuries at C-2 and C3–4 and 2) estimate spinal cord strains during intubation under these conditions.METHODSThe FE model was designed to replicate the properties of an intact (stable) spine in patients, C-2 injury (Type II odontoid fracture), and a severe C3–4 distractive-flexion injury from prior cadaver studies. The authors recorded the laryngoscope force values from 2 different laryngoscopes (Macintosh, high intubation force; Airtraq, low intubation force) used during the patient and cadaver intubation studies. FE-modeled motion was compared with experimentally measured motion, and corresponding cord strain values were calculated.RESULTSFE model predictions of intact intervertebral motions were comparable to motions measured in patients and in cadavers at occiput–C2. In intact subaxial segments, the FE model more closely predicted patient intervertebral motions than did cadavers. With C-2 injury, FE-predicted motions did not differ from cadaver measurements. With C3–4 injury, however, the FE model predicted greater motions than were measured in cadavers. FE model cord strains during intubation were greater for the Macintosh laryngoscope than the Airtraq laryngoscope but were comparable among the 3 conditions (intact, C-2 injury, and C3–4 injury).CONCLUSIONSThe FE model is comparable to patients and cadaver models in estimating occiput–C2 motion during intubation in both intact and injured conditions. The FE model may be superior to cadavers in predicting motions of subaxial segments in intact and injured conditions.

Cervical facetectomy and its effect on spine strength

1985 ◽  
Vol 63 (2) ◽  
pp. 278-282 ◽  
Author(s):  
Richard B. Raynor ◽  
James Pugh ◽  
Ilan Shapiro
Keyword(s):  
Cervical Spine ◽  
Facet Joint ◽  
Fracture Load ◽  
Facet Joints ◽  
Shear Tests ◽  
Content Type ◽  
Spine Motion ◽  
Vertebral Bodies ◽  
The Difference ◽  
Anterior Posterior

✓ Fourteen cervical spine motion segments consisting of two adjacent vertebral bodies and their connecting ligaments were tested in shear. Five had intact facet joints, five had bilateral facetectomy of 50% or less, and four had bilateral 70% facetectomy. Three to 5 mm of root could be exposed in the specimens with 50% facetectomy, and 8 to 10 mm in those with 70% facetectomy. Anterior-posterior shear tests were run alternately in compression and distraction. Facetectomy was found to have no effect on compression and distraction stiffness. Failure in the 70% facetectomized specimens was due to fracture of the remaining joint at 159 lbs. In the specimens with 50% facetectomy, a fracture load could not be established since failure of the specimen mounting occurred at 208 lbs, as it did in two of the specimens without facetectomy that were tested to failure. The difference in bone fracture at 159 lbs and mounting failure at 208 lbs is significant at p < 0.05. Bilateral resection of more than 50% of the facet joint significantly compromises the shear strength of a cervical spine motion segment.

scholarly journals Intubation Biomechanics

2014 ◽  
Vol 121 (2) ◽  
pp. 260-271 ◽  
Author(s):  
Bradley J. Hindman ◽  
Brandon G. Santoni ◽  
Christian M. Puttlitz ◽  
Robert P. From ◽  
Michael M. Todd
Keyword(s):  
Cervical Spine ◽  
Endotracheal Intubation ◽  
Elective Surgery ◽  
Cervical Cord ◽  
Force And Motion ◽  
Glottic View ◽  
Cord Injury ◽  
Patients At Risk ◽  
Spine Motion ◽  
The Relationship

Abstract Introduction: Laryngoscopy and endotracheal intubation in the presence of cervical spine instability may put patients at risk of cervical cord injury. Nevertheless, the biomechanics of intubation (cervical spine motion as a function of applied force) have not been characterized. This study characterized and compared the relationship between laryngoscope force and cervical spine motion using two laryngoscopes hypothesized to differ in force. Methods: Fourteen adults undergoing elective surgery were intubated twice (Macintosh, Airtraq). During each intubation, laryngoscope force, cervical spine motion, and glottic view were recorded. Force and motion were referenced to a preintubation baseline (stage 1) and were characterized at three stages: stage 2 (laryngoscope introduction); stage 3 (best glottic view); and stage 4 (endotracheal tube in trachea). Results: Maximal force and motion occurred at stage 3 and differed between the Macintosh and Airtraq: (1) force: 48.8 ± 15.8 versus 10.4 ± 2.8 N, respectively, P = 0.0001; (2) occiput-C5 extension: 29.5 ± 8.5 versus 19.1 ± 8.7 degrees, respectively, P = 0.0023. Between stages 2 and 3, the motion/force ratio differed between Macintosh and Airtraq: 0.5 ± 0.2 versus 2.0 ± 1.4 degrees/N, respectively; P = 0.0006. Discussion: The relationship between laryngoscope force and cervical spine motion is: (1) nonlinear and (2) differs between laryngoscopes. Differences between laryngoscopes in motion/force relationships are likely due to: (1) laryngoscope-specific cervical extension needed for intubation, (2) laryngoscope-specific airway displacement/deformation needed for intubation, and (3) cervical spine and airway tissue viscoelastic properties. Cervical spine motion during endotracheal intubation is not directly proportional to force. Low-force laryngoscopes cannot be assumed to result in proportionally low cervical spine motion.

scholarly journals Intubation Biomechanics

2015 ◽  
Vol 123 (5) ◽  
pp. 1042-1058 ◽  
Author(s):  
Bradley J. Hindman ◽  
Robert P. From ◽  
Ricardo B. Fontes ◽  
Vincent C. Traynelis ◽  
Michael M. Todd ◽  
...  
Keyword(s):  
Cervical Spine ◽  
Random Order ◽  
Cord Compression ◽  
Odontoid Fracture ◽  
Force Sensing ◽  
Type Ii ◽  
High Likelihood ◽  
Force Ratio ◽  
Spine Motion ◽  
Cervical Segment

Abstract Background The aims of this study are to characterize (1) the cadaver intubation biomechanics, including the effect of repeated intubations, and (2) the relation between intubation force and the motion of an injured cervical segment. Methods Fourteen cadavers were serially intubated using force-sensing Macintosh and Airtraq laryngoscopes in random order, with simultaneous cervical spine motion recorded with lateral fluoroscopy. Motion of the C1-C2 segment was measured in the intact and injured state (type II odontoid fracture). Injured C1-C2 motion was proportionately corrected for changes in intubation forces that occurred with repeated intubations. Results Cadaver intubation biomechanics were comparable with those of patients in all parameters other than C2-C5 extension. In cadavers, intubation force (set 2/set 1 force ratio = 0.61; 95% CI, 0.46 to 0.81; P = 0.002) and Oc-C5 extension (set 2 − set 1 difference = −6.1 degrees; 95% CI, −11.4 to −0.9; P = 0.025) decreased with repeated intubations. In cadavers, C1-C2 extension did not differ (1) between intact and injured states; or (2) in the injured state, between laryngoscopes (with and without force correction). With force correction, in the injured state, C1-C2 subluxation was greater with the Airtraq (mean difference 2.8 mm; 95% CI, 0.7 to 4.9 mm; P = 0.004). Conclusions With limitations, cadavers may be clinically relevant models of intubation biomechanics and cervical spine motion. In the setting of a type II odontoid fracture, C1-C2 motion during intubation with either the Macintosh or the Airtraq does not appear to greatly exceed physiologic values or to have a high likelihood of hyperextension or direct cord compression.

Cervical Spine Motion: A Fluoroscopic Comparison During Intubation with Lighted Stylet, GlideScope, and Macintosh Laryngoscope

2005 ◽  
Vol 101 (3) ◽  
pp. 910-915 ◽  
Author(s):  
Timothy P. Turkstra ◽  
Rosemary A. Craen ◽  
David M. Pelz ◽  
Adrian W. Gelb
Keyword(s):  
Cervical Spine ◽  
Macintosh Laryngoscope ◽  
Spine Motion ◽  
Lighted Stylet
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