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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.


Anterior interbody spacer PILLAR AL, Orthofix, Lewisville, TX.
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Figure 0002: Anterior interbody spacer PILLAR AL, Orthofix, Lewisville, TX.

Mentions: Lumbar interbody fusion is an often performed and well described procedure. The most commonly utilized fusion construct involves anterior and posterior fixation (360° fusion) utilizing an interbody graft/spacer with posterior pedicle screws and rods which substantially increases the stability of ALIF construct1–8 and is associated with a significantly improved fusion rate9, 10. An aggressive surgery by means of 360° fusion, although linked with higher fusion rates, is not always associated with a favorable clinical outcome9. Several clinical problems have been attributed to intraoperative damage of the posterior muscle groups. Numerous studies have shown that lumbar surgery through a posterior approach results in erector spinae muscle changes, demonstrated through clinical studies measuring extensor strength11, 12, histologic studies11, 13–17 and postoperative imaging studies by computed tomography (CT)11 or magnetic resonance imaging (MRI).18, 19 In addition erector spinae are detached from the paravertebral gutters then held laterally by self-retaining retractors during posterior lumbar surgery. Studies by Kawaguchi et al. suggest that pressure caused by self-retaining retractors leads to lesions of the erector spinae13. Results from biomechanical and clinical studies indicate that an anterior only approach utilizing an interbody spacer and anterior plate seem to provide stability comparable to that of a 360° (interbody + pedicle screw fixation) and less postoperative morbidity.20 However, the anterior only standard of care is the use of an interbody device with an anterior plate which protrudes anteriorly from the vertebral bodies creating a raised profile which interferes with the great vessels which are also anterior and adjacent to the lumbar vertebral bodies. The profile of current plates for anterior fusion is lower than that of earlier designs, but they are still bulky and might lead to postoperative complications. The insertion of these plates is a time-consuming surgical procedure which requires wider surgical exposure, more tissue dissection, anterior muscle disruption, and higher post-op morbidity. During this procedure some anatomical structures on the anterior aspect of the lumbar spine, such as the great vessels, are endangered. Other disadvantages include screw migration with possible soft tissue damage, increased of risk of adjacent level ossification and difficulty in stacking plates for adjacent level surgery. As a further improvement of this anterior only concept, combination or integrated interbody spacers for zero- or low profile segmental stabilization have been developed to perform the role of the separate spacer and plate. The proposed benefit of these integrated devices is that they provide sufficient stabilization to promote biologic fusion while avoiding posterior soft tissue morbidity during the primary procedure. In addition, the concern for adjacent level ossification is less, and in cases of adjacent level disease, the integrated interbody device can be placed without interfering with the previously operated segment nor requiring removal of the previously placed anterior plate. An additional benefit of these integrated devices is that they fit completely inside the disc space therefore limiting the exposure of the anterior spine column and potentially reduce complications such as vascular injury21–24. The objective of this study was to determine if an Integrated Interbody Fusion Device (PILLAR SA, Orthofix, Lewisville, TX) Figure 1A can stabilize single motion segments as effectively as an anterior interbody spacer (PILLAR AL, Orthofix, Lewisville, TX) Figure 1B + posterior instrumentation (pedicle screw construct) i.e. a 360° fusion construct. The following hypotheses were tested: (1) An Integrated Lumbar Interbody Fusion Device (PILLAR SA) will significantly reduce motion at the implanted level, relative to intact; (2) The PILLAR SA device will function biomechanically similar to a traditional anterior interbody spacer (PILLAR AL) plus posterior instrumentation (360° fusion construct).


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)

Anterior interbody spacer PILLAR AL, Orthofix, Lewisville, TX.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 0002: Anterior interbody spacer PILLAR AL, Orthofix, Lewisville, TX.
Mentions: Lumbar interbody fusion is an often performed and well described procedure. The most commonly utilized fusion construct involves anterior and posterior fixation (360° fusion) utilizing an interbody graft/spacer with posterior pedicle screws and rods which substantially increases the stability of ALIF construct1–8 and is associated with a significantly improved fusion rate9, 10. An aggressive surgery by means of 360° fusion, although linked with higher fusion rates, is not always associated with a favorable clinical outcome9. Several clinical problems have been attributed to intraoperative damage of the posterior muscle groups. Numerous studies have shown that lumbar surgery through a posterior approach results in erector spinae muscle changes, demonstrated through clinical studies measuring extensor strength11, 12, histologic studies11, 13–17 and postoperative imaging studies by computed tomography (CT)11 or magnetic resonance imaging (MRI).18, 19 In addition erector spinae are detached from the paravertebral gutters then held laterally by self-retaining retractors during posterior lumbar surgery. Studies by Kawaguchi et al. suggest that pressure caused by self-retaining retractors leads to lesions of the erector spinae13. Results from biomechanical and clinical studies indicate that an anterior only approach utilizing an interbody spacer and anterior plate seem to provide stability comparable to that of a 360° (interbody + pedicle screw fixation) and less postoperative morbidity.20 However, the anterior only standard of care is the use of an interbody device with an anterior plate which protrudes anteriorly from the vertebral bodies creating a raised profile which interferes with the great vessels which are also anterior and adjacent to the lumbar vertebral bodies. The profile of current plates for anterior fusion is lower than that of earlier designs, but they are still bulky and might lead to postoperative complications. The insertion of these plates is a time-consuming surgical procedure which requires wider surgical exposure, more tissue dissection, anterior muscle disruption, and higher post-op morbidity. During this procedure some anatomical structures on the anterior aspect of the lumbar spine, such as the great vessels, are endangered. Other disadvantages include screw migration with possible soft tissue damage, increased of risk of adjacent level ossification and difficulty in stacking plates for adjacent level surgery. As a further improvement of this anterior only concept, combination or integrated interbody spacers for zero- or low profile segmental stabilization have been developed to perform the role of the separate spacer and plate. The proposed benefit of these integrated devices is that they provide sufficient stabilization to promote biologic fusion while avoiding posterior soft tissue morbidity during the primary procedure. In addition, the concern for adjacent level ossification is less, and in cases of adjacent level disease, the integrated interbody device can be placed without interfering with the previously operated segment nor requiring removal of the previously placed anterior plate. An additional benefit of these integrated devices is that they fit completely inside the disc space therefore limiting the exposure of the anterior spine column and potentially reduce complications such as vascular injury21–24. The objective of this study was to determine if an Integrated Interbody Fusion Device (PILLAR SA, Orthofix, Lewisville, TX) Figure 1A can stabilize single motion segments as effectively as an anterior interbody spacer (PILLAR AL, Orthofix, Lewisville, TX) Figure 1B + posterior instrumentation (pedicle screw construct) i.e. a 360° fusion construct. The following hypotheses were tested: (1) An Integrated Lumbar Interbody Fusion Device (PILLAR SA) will significantly reduce motion at the implanted level, relative to intact; (2) The PILLAR SA device will function biomechanically similar to a traditional anterior interbody spacer (PILLAR AL) plus posterior instrumentation (360° fusion construct).

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.