8 results on '"Theodore, Nicholas"'
Search Results
2. Pediatric cervical spine injuries: a comprehensive review
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Mortazavi, Martin, Gore, Pankaj A., Chang, Steve, Tubbs, R. Shane, and Theodore, Nicholas
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- 2011
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3. What Can Standard in Vitro Biomechanical Testing Tell Us about Adjacent Segment Disease?
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Kelly, Brian P. and Theodore, Nicholas
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CERVICAL vertebrae , *BIOMECHANICS , *KINEMATICS , *INTERVERTEBRAL disk , *IN vitro studies , *ANATOMY - Published
- 2016
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4. Biomechanical Effects of an Oblique Lumbar PEEK Cage and Posterior Augmentation.
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Soriano-Baron, Hector, Newcomb, Anna G.U.S., Malhotra, Devika, Martinez del Campo, Eduardo, Palma, Atilio E., Theodore, Nicholas, Crawford, Neil R., Kelly, Brian P., and Kaibara, Taro
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POLYETHER ether ketone , *NONDESTRUCTIVE testing , *BIOMECHANICS , *SPINAL fusion - Abstract
Lumbar interbody spacers are widely used in lumbar spinal fusion. The goal of this study is to analyze the biomechanics of a lumbar interbody spacer (Clydesdale Spinal System, Medtronic Sofamor Danek, Memphis, Tennessee, USA) inserted via oblique lumbar interbody fusion (OLIF) or direct lateral interbody fusion (DLIF) approaches, with and without posterior cortical screw and rod (CSR) or pedicle screw and rod (PSR) instrumentation. Lumbar human cadaveric specimens (L2–L5) underwent nondestructive flexibility testing in intact and instrumented conditions at L3–L4, including OLIF or DLIF, with and without CSR or PSR. OLIF alone significantly reduced range of motion (ROM) in flexion-extension (P = 0.005) but not during lateral bending or axial rotation (P ≥ 0.63). OLIF alone reduced laxity in the lax zone (LZ) during flexion-extension (P < 0.001) but did not affect the LZ during lateral bending or axial rotation (P ≥ 0.14). The stiff zone (SZ) was unaffected in all directions (P ≥ 0.88). OLIF plus posterior instrumentation (cortical, pedicle, or hybrid) reduced the mean ROM in all directions of loading but only significantly so with PSR during lateral bending (P = 0.004), without affecting the compressive stiffness (P > 0.20). The compressive stiffness with the OLIF device without any posterior instrumentation did not differ from that of the intact condition (P = 0.97). In terms of ROM, LZ, or SZ, there were no differences between OLIF and DLIF as standalone devices or OLIF and DLIF with posterior instrumentation (CSR or PSR) (P > 0.5). OLIF alone significantly reduced mobility during flexion-extension while maintaining axial compressive stiffness compared with the intact condition. Adding posterior instrumentation to the interbody spacer increased the construct stability significantly, regardless of cage insertion trajectory or screw type. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
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5. Biomechanical Evaluation of Cervicothoracic Junction Fusion Constructs.
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Godzik, Jakub, Dalton, Jonathan F., Martinez-del-Campo, Eduardo, Newcomb, Anna G.U.S., Dominguez, Felix, Reyes, Phillip M., Theodore, Nicholas, Kelly, Brian P., and Crawford, Neil R.
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THORACIC vertebrae , *CERVICAL vertebrae , *SCREWS , *ROTATIONAL motion - Abstract
Objective We studied the effect of different cervicothoracic construct design variables on biomechanical stability in vitro. Methods Six fresh-frozen human cadaveric spines (C5–T4) were used. After intact analysis, each specimen was destabilized and reconstructed, with all groups having 4.0-mm pedicle screws placed at T1–T3. The 2 hook-rod constructs included interlaminar hooks at C6 and C7, with either 3.5-mm or 4.0-mm rods (C6–T3). The 2 screw-rod constructs tested included lateral mass screws at C6 and C7, with either 3.5-mm or 4.0-mm rods (C6–T3). The 2 screw-connector-rod constructs tested included lateral mass screws at C6 and C7, with either 3.5-mm or 4.0-mm rods; 1 rod spanned C6-C7 with a connector to a second rod of the same size spanning T1–T3. Global (C6–T3) and intervertebral (C6-C7, C7-T1, T1-T2, and T2-T3) ranges of motion were compared for each construct. Results In terms of global (C6–T3) stability, 3.5-mm versus 4.0-mm rod constructs were not significantly different, regardless of whether the construct was hook-rod, screw-rod, or screw-connector-rod. The hook-rod constructs provided less stability compared with the screw-rod and screw-connector-rod constructs in lateral bending (P < 0.04) and axial rotation (P < 0.001). The screw-rod constructs demonstrated a similar range of motion to that of the screw-connector-rod constructs, except for significantly less axial rotation at the C6-C7 level with 3.5-mm rods (P = 0.04). Conclusions We found that the rod diameter of a construct does not appear to significantly influence the biomechanical stability of subaxial constructs. The screw-rod construct resulted in certain biomechanical advantages compared with the screw-connector-rod construct, and both were significantly superior to the hook-rod construct. [ABSTRACT FROM AUTHOR]
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- 2019
- Full Text
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6. Biomechanical and Endplate Effects on Nutrient Transport in the Intervertebral Disc.
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Giers, Morgan B., Munter, Bryce T., Eyster, Kyle J., Ide, George D., Newcomb, Anna G.U.S., Lehrman, Jennifer N., Belykh, Evgenii, Byvaltsev, Vadim A., Kelly, Brian P., Preul, Mark C., and Theodore, Nicholas
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NUCLEUS pulposus , *CELL physiology , *CALCIFICATION , *EXTRACELLULAR matrix , *BIOMECHANICS , *INTERVERTEBRAL disk - Abstract
Background Physical data are lacking on nutrient transport in human intervertebral discs (IVDs), which support regeneration. Our objective was to study nutrient transport in porcine IVDs to determine the effects of biomechanical and physiological factors. Methods In vitro testing of whole porcine IVDs was performed under different loading conditions. Fifty cervical, thoracic, and lumbar discs with attached end plates were removed from 4 Yorkshire pigs (90–150 lbs). Discs were placed in Safranin O or Fast Green FCF histological stains in diffusion or diurnal compression-tested groups. The end plate was studied by the use of polyurethane to block it. Traction was studied with a mechanical testing frame. Discs were cut transversely and photographed. Images were analyzed for depth of annulus fibrosus (AF) stained. The nucleus pulposus (NP) was assigned a staining score. Results Results showed no difference in AF staining between the 2 stains ( P = 0.60). The depth of AF staining did not increase ( P = 0.60) due to convection or disc height change via diurnal loading. The NP in all open end plate samples was stained completely by day 3. NP staining was decreased in blocked end plate samples ( P = 0.07) and AF staining was significantly less in traction samples than in diffusion-only samples ( P = 0.04). Conclusions This method showed that most small molecule nutrient transport occurs via the end plate. Compressive load was a negligible benefit or hindrance to transport. Traction hindered transport in the short term. This method can be used to study strategies for increasing nutrient transport in IVDs. [ABSTRACT FROM AUTHOR]
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- 2017
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7. Biomechanical evaluation of a metal-on-metal cervical intervertebral disc prosthesis.
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Colle, Kyle O., Butler, John B., Reyes, Phillip M., Newcomb, Anna G.U.S., Theodore, Nicholas, and Crawford, Neil R.
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INTERVERTEBRAL disk prostheses , *BIOMECHANICS , *METALS in surgery , *MUSCLE strength , *THREE-dimensional imaging , *MEDICAL imaging systems , *STANDARD deviations - Abstract
Abstract: Background context: In vitro nondestructive flexibility testing of the CerviCore total disc replacement (TDR) was performed. It was hypothesized that TDR would not significantly alter biomechanics relative to intact, whereas rigid fixation would cause significant changes. Purpose: To assess the ability of a cervical metal-on-metal saddle-shaped TDR to replicate normal biomechanics in vitro. Study design: Human cadaveric flexibility experiment. Methods: Nine human cadaveric C3–T1 specimens were tested intact, after TDR and after anterior plating. Flexion, extension, lateral bending, and axial rotation were induced by pure moments; flexion-extension was then repeated using a simplified muscle force model with 70-N follower load. Optical markers measured three-dimensional intervertebral motion, and eight points of laminar surface strain were recorded near the left and right C5–C6 facet joints. Biomechanical parameters studied included range of motion (ROM), lax zone (LZ), angular coupling pattern, sagittal instantaneous axis of rotation (IAR), and facet loads normal to the facet joint plane. Mean values of parameters were compared statistically using repeated measures analysis of variance and Holm-Sidak tests. Results: Total disc replacement caused significant reduction in ROM during extension (p=.004) and significant reduction in LZ during lateral bending (p=.01). However, plating significantly reduced both ROM and LZ during flexion, extension, and lateral bending (p<.006). Sagittal IAR shifted relative to intact by 3.6 mm after TDR (p>.05) and 6.5 mm after plating (p>.05). Coupled axial rotation/degree lateral bending was 99% of intact after TDR but 76% of intact after plating (p=.15). Coupled lateral bending/degree axial rotation was 95% of intact after TDR but 85% of intact after plating (p=.43). Neither construct altered facet loads from intact. Conclusions: With regard to ROM, LZ, IAR, and coupling, deviations from intact biomechanics were less substantial after TDR than after plating. Facet load alterations were minimal with either construct. Our results show that this particular TDR permits ROM and maintains some measures of kinematics in a cadaver model. [Copyright &y& Elsevier]
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- 2013
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8. P23 - Biomechanical Effects of an Oblique Lumbar PEEK Cage and Posterior Augmentation.
- Author
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Sorian-Baron, Hector, Newcomb, Anna G., Crawford, Neil, Kelly, Brian, and Theodore, Nicholas
- Subjects
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LUMBAR vertebrae diseases , *BIOMECHANICS , *POLYETHER ether ketone , *RANGE of motion of joints - Published
- 2017
- Full Text
- View/download PDF
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