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Biomechanical characteristics of an integrated lumbar interbody fusion device.

Voronov LI, Vastardis G, Zelenakova J, Carandang G, Havey RM, Waldorff EI, Zindrick MR, Patwardhan AG - Int J Spine Surg (2014)

Bottom Line: Each specimen was tested in flexion (8Nm) and extension (6Nm) without preload (0 N) and under 400N of preload, in lateral bending (±6 Nm) and axial rotation (±5 Nm) without preload.PILLAR SA reduced ROM from 8.9±1.9 to 2.9±1.1° in FE with 400N follower preload (67.4%), 8.0±1.7 to 2.5±1.1° in LB, and 2.2±1.2 to 0.7±0.3° in AR.The PILLAR SA resulted in motions of less than 3° in all modes of motion and was not as motion restricting as the traditional 360° using bilateral pedicle screws.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery and Rehabilitation, Loyola University Medical Center, Maywood, Illinois ; Musculoskeletal Biomechanics Laboratory, Department of Veterans Affairs, Edward Hines Jr. VA Hospital, Hines, Illinois.

ABSTRACT

Introduction: We hypothesized that an Integrated Lumbar Interbody Fusion Device (PILLAR SA, Orthofix, Lewisville, TX) will function biomechanically similar to a traditional anterior interbody spacer (PILLAR AL, Orthofix, Lewisville, TX) plus posterior instrumentation (FIREBIRD, Orthofix, Lewisville, TX). Purpose of this study was to determine if an Integrated Interbody Fusion Device (PILLAR SA) can stabilize single motion segments as well as an anterior interbody spacer (PILLAR AL) + pedicle screw construct (FIREBIRD).

Methods: Eight cadaveric lumbar spines (age: 43.9±4.3 years) were used. Each specimen's range of motion was tested in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) under intact condition, after L4-L5 PILLAR SA with intervertebral screws and after L4-L5 360° fusion (PILLAR AL + Pedicle Screws and rods (FIREBIRD). Each specimen was tested in flexion (8Nm) and extension (6Nm) without preload (0 N) and under 400N of preload, in lateral bending (±6 Nm) and axial rotation (±5 Nm) without preload.

Results: Integrated fusion using the PILLAR SA device demonstrated statistically significant reductions in range of motion of the L4-L5 motion segment as compared to the intact condition for each test direction. PILLAR SA reduced ROM from 8.9±1.9 to 2.9±1.1° in FE with 400N follower preload (67.4%), 8.0±1.7 to 2.5±1.1° in LB, and 2.2±1.2 to 0.7±0.3° in AR. A comparison between the PILLAR SA integrated fusion device versus 360° fusion construct with spacer and bilateral pedicle screws was statistically significant in FE and LB. The 360° fusion yielded motion of 1.0±0.5° in FE, 1.0±0.8° in LB (p0.05).

Conclusions: The PILLAR SA resulted in motions of less than 3° in all modes of motion and was not as motion restricting as the traditional 360° using bilateral pedicle screws. The residual segmental motions compare very favorably with published biomechanical studies of other interbody integrated fusion devices.

No MeSH data available.


L4-L5 segmental flexion-extension range of motion in degrees.
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Figure 0009: L4-L5 segmental flexion-extension range of motion in degrees.

Mentions: In the absence of a compressive preload, the intact spine had a total angular motion of 9.0±2.3 degrees in flexion-extension corresponding to the moments used in this study (0-8Nm flexion, 0-6Nm extension) Figure 8. The motion increased to 11.8±2.7 degrees after nucleotomy (p < 0.01, compared to intact), then decreased to 5.6±3.2 degrees after implantation of the integrated lumbar cage (PILLAR SA), a reduction of 39.5±24.9% (p < 0.01, compared to intact). The addition of bilateral pedicle screws and rods to the integrated cage construct reduced the motion further, to 1.3±0.9 degrees (p < 0.01, compared to intact). The construct involving an interbody spacer (PILLAR AL) with supplemental bilateral pedicle screws and rods resulted in 1.7±1.2 degrees of angular motion at the L4-L5 segment, a reduction of 81.9±10.2% (p < 0.01, compared to intact). Application of a physiologic compressive preload of 400N caused a further decrease in motion of all fusion constructs(Figure 8). The angular motion of the construct utilizing the PILLAR SA implant was reduced to 3.4±1.7 degrees, a reduction of 64.5±12.7% from intact (p < 0.01, compared to 0 N preload). This is a significant improvement in the performance of the integrated cage due to the addition of physiologic compressive preload (64.5% vs. 39.5% reduction from intact motion). The 360° fusion yielded motion of 1.1±0.5 degrees in flexion-extension, which was significantly less than the motion in the construct using the integrated fusion device (p < 0.05). When the flexion and extension modes were analyzed separately, the integrated cage device, in the absence of a compressive preload, reduced motion in flexion (p < 0.01, compared to intact) but not in extension (p > 0.9, compared to intact) (Figure 9 & Figure 10). With the addition of a 400 N compressive preload, the motion of the integrated cage construct further reduced in flexion and the motion in extension became significantly smaller than intact (p < 0.05).


Biomechanical characteristics of an integrated lumbar interbody fusion device.

Voronov LI, Vastardis G, Zelenakova J, Carandang G, Havey RM, Waldorff EI, Zindrick MR, Patwardhan AG - Int J Spine Surg (2014)

L4-L5 segmental flexion-extension range of motion in degrees.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4325499&req=5

Figure 0009: L4-L5 segmental flexion-extension range of motion in degrees.
Mentions: In the absence of a compressive preload, the intact spine had a total angular motion of 9.0±2.3 degrees in flexion-extension corresponding to the moments used in this study (0-8Nm flexion, 0-6Nm extension) Figure 8. The motion increased to 11.8±2.7 degrees after nucleotomy (p < 0.01, compared to intact), then decreased to 5.6±3.2 degrees after implantation of the integrated lumbar cage (PILLAR SA), a reduction of 39.5±24.9% (p < 0.01, compared to intact). The addition of bilateral pedicle screws and rods to the integrated cage construct reduced the motion further, to 1.3±0.9 degrees (p < 0.01, compared to intact). The construct involving an interbody spacer (PILLAR AL) with supplemental bilateral pedicle screws and rods resulted in 1.7±1.2 degrees of angular motion at the L4-L5 segment, a reduction of 81.9±10.2% (p < 0.01, compared to intact). Application of a physiologic compressive preload of 400N caused a further decrease in motion of all fusion constructs(Figure 8). The angular motion of the construct utilizing the PILLAR SA implant was reduced to 3.4±1.7 degrees, a reduction of 64.5±12.7% from intact (p < 0.01, compared to 0 N preload). This is a significant improvement in the performance of the integrated cage due to the addition of physiologic compressive preload (64.5% vs. 39.5% reduction from intact motion). The 360° fusion yielded motion of 1.1±0.5 degrees in flexion-extension, which was significantly less than the motion in the construct using the integrated fusion device (p < 0.05). When the flexion and extension modes were analyzed separately, the integrated cage device, in the absence of a compressive preload, reduced motion in flexion (p < 0.01, compared to intact) but not in extension (p > 0.9, compared to intact) (Figure 9 & Figure 10). With the addition of a 400 N compressive preload, the motion of the integrated cage construct further reduced in flexion and the motion in extension became significantly smaller than intact (p < 0.05).

Bottom Line: Each specimen was tested in flexion (8Nm) and extension (6Nm) without preload (0 N) and under 400N of preload, in lateral bending (±6 Nm) and axial rotation (±5 Nm) without preload.PILLAR SA reduced ROM from 8.9±1.9 to 2.9±1.1° in FE with 400N follower preload (67.4%), 8.0±1.7 to 2.5±1.1° in LB, and 2.2±1.2 to 0.7±0.3° in AR.The PILLAR SA resulted in motions of less than 3° in all modes of motion and was not as motion restricting as the traditional 360° using bilateral pedicle screws.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery and Rehabilitation, Loyola University Medical Center, Maywood, Illinois ; Musculoskeletal Biomechanics Laboratory, Department of Veterans Affairs, Edward Hines Jr. VA Hospital, Hines, Illinois.

ABSTRACT

Introduction: We hypothesized that an Integrated Lumbar Interbody Fusion Device (PILLAR SA, Orthofix, Lewisville, TX) will function biomechanically similar to a traditional anterior interbody spacer (PILLAR AL, Orthofix, Lewisville, TX) plus posterior instrumentation (FIREBIRD, Orthofix, Lewisville, TX). Purpose of this study was to determine if an Integrated Interbody Fusion Device (PILLAR SA) can stabilize single motion segments as well as an anterior interbody spacer (PILLAR AL) + pedicle screw construct (FIREBIRD).

Methods: Eight cadaveric lumbar spines (age: 43.9±4.3 years) were used. Each specimen's range of motion was tested in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) under intact condition, after L4-L5 PILLAR SA with intervertebral screws and after L4-L5 360° fusion (PILLAR AL + Pedicle Screws and rods (FIREBIRD). Each specimen was tested in flexion (8Nm) and extension (6Nm) without preload (0 N) and under 400N of preload, in lateral bending (±6 Nm) and axial rotation (±5 Nm) without preload.

Results: Integrated fusion using the PILLAR SA device demonstrated statistically significant reductions in range of motion of the L4-L5 motion segment as compared to the intact condition for each test direction. PILLAR SA reduced ROM from 8.9±1.9 to 2.9±1.1° in FE with 400N follower preload (67.4%), 8.0±1.7 to 2.5±1.1° in LB, and 2.2±1.2 to 0.7±0.3° in AR. A comparison between the PILLAR SA integrated fusion device versus 360° fusion construct with spacer and bilateral pedicle screws was statistically significant in FE and LB. The 360° fusion yielded motion of 1.0±0.5° in FE, 1.0±0.8° in LB (p0.05).

Conclusions: The PILLAR SA resulted in motions of less than 3° in all modes of motion and was not as motion restricting as the traditional 360° using bilateral pedicle screws. The residual segmental motions compare very favorably with published biomechanical studies of other interbody integrated fusion devices.

No MeSH data available.