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Biomechanical analysis of a newly developed shape memory alloy hook in a transforaminal lumbar interbody fusion (TLIF) in vitro model.

Wang X, Xu J, Zhu Y, Li J, Zhou S, Tian S, Xiang Y, Liu X, Zheng Y, Pan T - PLoS ONE (2014)

Bottom Line: The UPS significantly reduced the ROM in extension/flexion and lateral bending; the BSMAH significantly reduced the ROM in extension/flexion, lateral bending, and axial rotation; and the USMAH significantly reduced the ROM in flexion and left lateral bending compared with the intact spine (p<0.05).The USMAH slightly reduced the ROM in extension, right lateral bending and axial rotation (p>0.05).Stability provided by the USMAH compared with the UPS was not significantly different.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, The Sixth Affiliated Hospital of Sun Yat-sen University, Guangzhou, PR China.

ABSTRACT

Objective: The objective of this biomechanical study was to evaluate the stability provided by a newly developed shape memory alloy hook (SMAH) in a cadaveric transforaminal lumbar interbody fusion (TLIF) model.

Methods: Six human cadaveric spines (L1-S2) were tested in an in vitro flexibility experiment by applying pure moments of ±8 Nm in flexion/extension, left/right lateral bending, and left/right axial rotation. After intact testing, a TLIF was performed at L4-5. Each specimen was tested for the following constructs: unilateral SMAH (USMAH); bilateral SMAH (BSMAH); unilateral pedicle screws and rods (UPS); and bilateral pedicle screws and rods (BPS). The L3-L4, L4-L5, and L5-S1 range of motion (ROM) were recorded by a Motion Analysis System.

Results: Compared to the other constructs, the BPS provided the most stability. The UPS significantly reduced the ROM in extension/flexion and lateral bending; the BSMAH significantly reduced the ROM in extension/flexion, lateral bending, and axial rotation; and the USMAH significantly reduced the ROM in flexion and left lateral bending compared with the intact spine (p<0.05). The USMAH slightly reduced the ROM in extension, right lateral bending and axial rotation (p>0.05). Stability provided by the USMAH compared with the UPS was not significantly different. ROMs of adjacent segments increased in all fixed constructs (p>0.05).

Conclusions: Bilateral SMAH fixation can achieve immediate stability after L4-5 TLIF in vitro. Further studies are required to determine whether the SMAH can achieve fusion in vivo and alleviate adjacent segment degeneration.

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Related in: MedlinePlus

Flexibility test system.The specimen was fixed on the working table. Laser balls were used to simulate planes of representative vertebral bodies. An unstrained spinal 3-D motion was obtained by cables connected to loading discs. A suspended counterweight transferred equal but opposing forces on to the top of the specimen. The movement of the laser balls was tracked by six cameras hanging at different sites from the ceiling.
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pone-0114326-g001: Flexibility test system.The specimen was fixed on the working table. Laser balls were used to simulate planes of representative vertebral bodies. An unstrained spinal 3-D motion was obtained by cables connected to loading discs. A suspended counterweight transferred equal but opposing forces on to the top of the specimen. The movement of the laser balls was tracked by six cameras hanging at different sites from the ceiling.

Mentions: The Flexibility Test System was composed of cables, pulleys, suspended counterweights, a loading disc, and a basement. The lower side of the PMMA block was placed on the basement, the upper side of the PMMA block was fixed to the loading disc. The cables connected to the loading disc and suspended counterweight transferred equal but opposing forces on to the top of the specimen (Figure 1). Thus, the custom-made testing system could apply pure moments in flexion/extension, right/left rotation and right/left lateral bending and allowed complete, unconstrained 3-dimensional motion of the spine. To overcome the spine's viscoelastic effects, before recording motion data for each loading scenario, three preconditioning cycles were applied to the specimen, and applied moments were maintained for approximately 30 seconds. The motion of each segment was recorded using a clinical motion analysis system with four marker balls arranged rigidly along the plane of each vertebral body. ROM was calculated by Cortex software.


Biomechanical analysis of a newly developed shape memory alloy hook in a transforaminal lumbar interbody fusion (TLIF) in vitro model.

Wang X, Xu J, Zhu Y, Li J, Zhou S, Tian S, Xiang Y, Liu X, Zheng Y, Pan T - PLoS ONE (2014)

Flexibility test system.The specimen was fixed on the working table. Laser balls were used to simulate planes of representative vertebral bodies. An unstrained spinal 3-D motion was obtained by cables connected to loading discs. A suspended counterweight transferred equal but opposing forces on to the top of the specimen. The movement of the laser balls was tracked by six cameras hanging at different sites from the ceiling.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4256230&req=5

pone-0114326-g001: Flexibility test system.The specimen was fixed on the working table. Laser balls were used to simulate planes of representative vertebral bodies. An unstrained spinal 3-D motion was obtained by cables connected to loading discs. A suspended counterweight transferred equal but opposing forces on to the top of the specimen. The movement of the laser balls was tracked by six cameras hanging at different sites from the ceiling.
Mentions: The Flexibility Test System was composed of cables, pulleys, suspended counterweights, a loading disc, and a basement. The lower side of the PMMA block was placed on the basement, the upper side of the PMMA block was fixed to the loading disc. The cables connected to the loading disc and suspended counterweight transferred equal but opposing forces on to the top of the specimen (Figure 1). Thus, the custom-made testing system could apply pure moments in flexion/extension, right/left rotation and right/left lateral bending and allowed complete, unconstrained 3-dimensional motion of the spine. To overcome the spine's viscoelastic effects, before recording motion data for each loading scenario, three preconditioning cycles were applied to the specimen, and applied moments were maintained for approximately 30 seconds. The motion of each segment was recorded using a clinical motion analysis system with four marker balls arranged rigidly along the plane of each vertebral body. ROM was calculated by Cortex software.

Bottom Line: The UPS significantly reduced the ROM in extension/flexion and lateral bending; the BSMAH significantly reduced the ROM in extension/flexion, lateral bending, and axial rotation; and the USMAH significantly reduced the ROM in flexion and left lateral bending compared with the intact spine (p<0.05).The USMAH slightly reduced the ROM in extension, right lateral bending and axial rotation (p>0.05).Stability provided by the USMAH compared with the UPS was not significantly different.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, The Sixth Affiliated Hospital of Sun Yat-sen University, Guangzhou, PR China.

ABSTRACT

Objective: The objective of this biomechanical study was to evaluate the stability provided by a newly developed shape memory alloy hook (SMAH) in a cadaveric transforaminal lumbar interbody fusion (TLIF) model.

Methods: Six human cadaveric spines (L1-S2) were tested in an in vitro flexibility experiment by applying pure moments of ±8 Nm in flexion/extension, left/right lateral bending, and left/right axial rotation. After intact testing, a TLIF was performed at L4-5. Each specimen was tested for the following constructs: unilateral SMAH (USMAH); bilateral SMAH (BSMAH); unilateral pedicle screws and rods (UPS); and bilateral pedicle screws and rods (BPS). The L3-L4, L4-L5, and L5-S1 range of motion (ROM) were recorded by a Motion Analysis System.

Results: Compared to the other constructs, the BPS provided the most stability. The UPS significantly reduced the ROM in extension/flexion and lateral bending; the BSMAH significantly reduced the ROM in extension/flexion, lateral bending, and axial rotation; and the USMAH significantly reduced the ROM in flexion and left lateral bending compared with the intact spine (p<0.05). The USMAH slightly reduced the ROM in extension, right lateral bending and axial rotation (p>0.05). Stability provided by the USMAH compared with the UPS was not significantly different. ROMs of adjacent segments increased in all fixed constructs (p>0.05).

Conclusions: Bilateral SMAH fixation can achieve immediate stability after L4-5 TLIF in vitro. Further studies are required to determine whether the SMAH can achieve fusion in vivo and alleviate adjacent segment degeneration.

Show MeSH
Related in: MedlinePlus