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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.


Experimental Setup.
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Figure 0003: Experimental Setup.

Mentions: Eight fresh frozen human cadaveric spine specimens (L1-S1) were used for this study (age: 43.9±4.3 years). Radiographic screening was performed to exclude specimens with fractures, metastatic disease, bridging osteophytes, osteoporosis, previous spine surgeries or other conditions that could significantly affect the biomechanics of the spine. Bone mineral density (BMD) of each specimen was determined using a peripheral Quantitative Computed Tomography (pQCT) (Norland Medical Systems, Inc). A rectangular area 10 by 10 mm in the middle of the T12 vertebral body was investigated with an exposure dose of 200mA and 120 KVp. Based on the criteria proposed by WHO, specimens with normal BMD (BMD > 150 mg/cm3) were used for the study.25 Specimen demographics and pQCT values are presented in Table 1. The specimens were thawed and stripped of the paraspinal musculature while preserving the discs, facet joints, and osteoligamentous structures. The specimens were wrapped in saline soaked towels to prevent dehydration of the soft tissues. All tests were performed at room temperature. The specimens were fixed to the apparatus at the caudal end and free to move in any plane at the cephalad end Figure 2. A moment was applied by controlling the flow of water into bags attached to loading arms fixed to the L1 vertebra. The apparatus allows continuous cycling of the specimen between specified maximum moment endpoints in flexion, extension, lateral bending, and axial rotation. The load-displacement data was collected until two consecutive reproducible load-displacement loops were obtained. The angular motion of the L1 to S1 vertebrae were measured using an optoelectronic motion measurement system (Model 3020, Optotrak, Northern Digital, Waterloo, Ontario). In addition, bi-axial angle sensors (Model 902-45, Applied Geomechanics, Santa Cruz, CA) were mounted on each vertebra to allow real-time feedback for the optimization of the preload path. A sixcomponent load cell (Model MC3A-6-1000, AMTI Multi-component transducers, AMTI Inc., Newton, MA) was placed under the specimen to measure the applied compressive preload and moments. Fluoroscopic imaging (GE OEC 9800 Plus digital fluoroscopy machine) was used in the neutral, flexed and extended postures during the kinematic testing and during surgical implantations to ensure correct implant placement.


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)

Experimental Setup.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 0003: Experimental Setup.
Mentions: Eight fresh frozen human cadaveric spine specimens (L1-S1) were used for this study (age: 43.9±4.3 years). Radiographic screening was performed to exclude specimens with fractures, metastatic disease, bridging osteophytes, osteoporosis, previous spine surgeries or other conditions that could significantly affect the biomechanics of the spine. Bone mineral density (BMD) of each specimen was determined using a peripheral Quantitative Computed Tomography (pQCT) (Norland Medical Systems, Inc). A rectangular area 10 by 10 mm in the middle of the T12 vertebral body was investigated with an exposure dose of 200mA and 120 KVp. Based on the criteria proposed by WHO, specimens with normal BMD (BMD > 150 mg/cm3) were used for the study.25 Specimen demographics and pQCT values are presented in Table 1. The specimens were thawed and stripped of the paraspinal musculature while preserving the discs, facet joints, and osteoligamentous structures. The specimens were wrapped in saline soaked towels to prevent dehydration of the soft tissues. All tests were performed at room temperature. The specimens were fixed to the apparatus at the caudal end and free to move in any plane at the cephalad end Figure 2. A moment was applied by controlling the flow of water into bags attached to loading arms fixed to the L1 vertebra. The apparatus allows continuous cycling of the specimen between specified maximum moment endpoints in flexion, extension, lateral bending, and axial rotation. The load-displacement data was collected until two consecutive reproducible load-displacement loops were obtained. The angular motion of the L1 to S1 vertebrae were measured using an optoelectronic motion measurement system (Model 3020, Optotrak, Northern Digital, Waterloo, Ontario). In addition, bi-axial angle sensors (Model 902-45, Applied Geomechanics, Santa Cruz, CA) were mounted on each vertebra to allow real-time feedback for the optimization of the preload path. A sixcomponent load cell (Model MC3A-6-1000, AMTI Multi-component transducers, AMTI Inc., Newton, MA) was placed under the specimen to measure the applied compressive preload and moments. Fluoroscopic imaging (GE OEC 9800 Plus digital fluoroscopy machine) was used in the neutral, flexed and extended postures during the kinematic testing and during surgical implantations to ensure correct implant placement.

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.