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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

45 mm Shape memory Alloy Hook (SMAH).Left, prototype; right, unfolded in ice and water mixture.
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pone-0114326-g002: 45 mm Shape memory Alloy Hook (SMAH).Left, prototype; right, unfolded in ice and water mixture.

Mentions: For the USMAH, an appropriately sized TLIF spacer was inserted into the middle third of the L4-5 disc space. The length between the superior edge of the L4 lamina and inferior edge of the L5 lamina was measured to allow selection of a suitable SMAH. Different size SMAHs ranging from 39 mm to 59 mm in length were designed to meet individual needs. Every 2 mm is an interval. Therefore, if the shortest length between the superior edge of the L4 lamina and inferior edge of the L5 lamina was 45 mm, a 43 mm or 41 mm SMAH was chosen. The smaller size hook provided a persistent compressive force to stabilize the lumbar segments. After an SMAH was instrumented, stability was checked by shaking the hook. The hook was unfolded in an ice-water mixture using a stretcher, and instrumented on the right side superior edge of the L4 lamina and inferior edge of the L5 lamina using a holder (Figure 2). Gauze soaked in water at 37°C water was spread on the surface of the hook to promote re-plasticity. BSMAHs were instrumented on both side of L4 and L5 laminas, but the left facet joint was retained intact. When the SMAHs flexibility tests were complete, gauze soaked in ice-water was spread onto the surface of the hook to facilitate its removal. The pedicle screws (6.5 mm in diameter ×45 mm in length) and 5.5-mm–diameter titanium rods were instrumented according to common practice. As the SMAH did not damage the posterior structure, implantation of the pedicle screw-rod constructs was not affected by previous instrumentation with the SMAH.


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)

45 mm Shape memory Alloy Hook (SMAH).Left, prototype; right, unfolded in ice and water mixture.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0114326-g002: 45 mm Shape memory Alloy Hook (SMAH).Left, prototype; right, unfolded in ice and water mixture.
Mentions: For the USMAH, an appropriately sized TLIF spacer was inserted into the middle third of the L4-5 disc space. The length between the superior edge of the L4 lamina and inferior edge of the L5 lamina was measured to allow selection of a suitable SMAH. Different size SMAHs ranging from 39 mm to 59 mm in length were designed to meet individual needs. Every 2 mm is an interval. Therefore, if the shortest length between the superior edge of the L4 lamina and inferior edge of the L5 lamina was 45 mm, a 43 mm or 41 mm SMAH was chosen. The smaller size hook provided a persistent compressive force to stabilize the lumbar segments. After an SMAH was instrumented, stability was checked by shaking the hook. The hook was unfolded in an ice-water mixture using a stretcher, and instrumented on the right side superior edge of the L4 lamina and inferior edge of the L5 lamina using a holder (Figure 2). Gauze soaked in water at 37°C water was spread on the surface of the hook to promote re-plasticity. BSMAHs were instrumented on both side of L4 and L5 laminas, but the left facet joint was retained intact. When the SMAHs flexibility tests were complete, gauze soaked in ice-water was spread onto the surface of the hook to facilitate its removal. The pedicle screws (6.5 mm in diameter ×45 mm in length) and 5.5-mm–diameter titanium rods were instrumented according to common practice. As the SMAH did not damage the posterior structure, implantation of the pedicle screw-rod constructs was not affected by previous instrumentation with the SMAH.

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