- Email: [email protected]
P21. Lumbar percutaneous pedicle screw breach rates: a comparison of robotic navigation versus conventional techniques
Proceedings of the 34th Annual Meeting of the North American Spine Society / The Spine Journal 19 (2019) S158−S194 Runx2. After 4 months, the X-ray and micro-CT three-dimensional reconstruction results showed that there was no obvious healing of the bone defect in the blank group, and the bone defect in the SF, HA/SF, NG/HA/ SF group was partially healed, and the NG/GMs/HA/SF group has basically healed whose healing effect was better than that of SF, HA/SF, NG/ HA/SF group. In the NG/GMs/HA/SF group, HE staining, Safranin solid staining and Masson staining showed more osteogenesis area. Futhermore, serological osteogenic indicators, molecular biology, osteogenesis, angiogenesis, inflammation-related genes and protein up-regulated. CONCLUSIONS: The NG/GMs/HA/SF composite scaffolds may be used to treat osteoporotic vertebral fractures in rats by regulating the “osteogenesis differentiation-angiogenesis-inflammation” homeostasis. FDA DEVICE/DRUG STATUS: Unavailable from authors at time of publication. https://doi.org/10.1016/j.spinee.2019.05.442
ePosters: Biomechanics P19. Vertebra/implant response to cyclic loading is influenced by central strut support in intervertebral devices Antonio Valdevit, PhD; S-E-A, Columbus, OH, US BACKGROUND CONTEXT: The presence of a central strut may serve to strengthen a spinal spacer. However, it is unknown how a strut located in the central endplate region will influence vertebral body response under cyclic loading. PURPOSE: The authors hypothesized that devices with an open design will display comparable stiffness to devices with a central strut. Further, open devices would not restrict movement of the vertebral endplate and therefore display improved viscoelastic properties of the construct as compared to implants with a central strut. STUDY DESIGN/SETTING: Implants were fabricated from Ti-6Al-4V alloy represented an Open (contact area 427.5mm2) and Strutted device (contact area 407.9mm2 to 504.5mm2 depending on strut contact). PATIENT SAMPLE: Fourteen L4 or L5 porcine vertebra were randomly assigned to the implant groups. OUTCOME MEASURES: The ratio of the unloading/loading (loss/storage) stiffness values are used to compute Tan (d). Traditionally Tan (d) is associated with the loss and storage moduli. Such a calculation is not possible due to the complexity of contact area for a vertebral body. However, within any one specimen, the contact area is uniform and results in a scalable factor of the actual Tan (d). METHODS: Loading from 50N to 500N was applied at 1Hz for 500 cycles. Load and deformation data were acquired at 60Hz at 20 cycle intervals. The loading (storage) stiffness, unloading (loss) stiffness and mean Tan (d) were computed at each cycle interval and subjected to non-linear regression. The respective values for K (Rate) and Span (Change from initial value) for each implant type were compared using an unpaired t-test. RESULTS: For the loading stiffness, the regression analysis resulted in two rate parameters: KFast and KSLow. In the case of unloading stiffness, single rate functions were preferred. No statistical differences for loading stiffness were found between open and strutted devices for KFast (P>0.12) and KSlow (P>0.18). For the unloading stiffness, the K value for open devices was significantly decreased as compared to the strutted devices (P<0.0001). Open implants displayed statistically increased K value (P=0.0001) as compared to strutted devices (P<0.0001) for the Tan (d) analysis. Statistically decreased K values of open devices for unloading stiffness reflects a slow and gradual dissipation of energy to achieve equilibrium during cyclic loading. The gradual, more dissipative changes in energy dissipation of open devices may be beneficial in initiating and sustaining bone remodeling during strain hardening. The Tan (d) results for open devices indicated a rapid response via statistically increased K values to achieve a level of viscoelastic equilibrium (Span) that is significantly greater than that displayed by strutted implants. Increases in Tan (d) reflect improved dampening of the material.
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CONCLUSIONS: While metal devices encompassing an open concept are comparable in stiffness to devices containing a central strut, open designs can permit the unimpeded, viscoelastic response of the vertebral body which may be beneficial in the remodeling process. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. https://doi.org/10.1016/j.spinee.2019.05.443
P20. Titanium expandable interbody spacers placed via bilateral-TLIF provides stability similar to ALIF: an in-vitro range of motion analysis Steven A. Schopler, MD1, Samantha Greeley, BA2, Gerald Hayward, BS2, Hassaan P. Sheikh, BS2, Brandon Bucklen, PhD2; 1 Southern California Orthopedic Institute, Bakersfield, CA, US; 2 Globus Medical, Audubon, PA, US BACKGROUND CONTEXT: The transforaminal lumbar interbody fusion (TLIF) approach was developed to avoid the risks of the anterior lumbar interbody fusion (ALIF) and posterior lumbar interbody fusion (PLIF) approaches, and their potential for damage to the major vessels and the neurological elements, respectively. Construct stability of these various lumbar interbody fusion techniques is paramount to promote arthrodesis. Placement of two titanium expandable interbody spacers intradiscally following a bilateral facetectomy has the theoretical advantage of increased stability. PURPOSE: This biomechanical study aims to compare the stability of bilateral-TLIF with titanium expandable interbody spacers compared to various standard constructs in an in-vitro range of motion kinematic analysis in cadaveric models. STUDY DESIGN/SETTING: In vitro biomechanics study. OUTCOME MEASURES: Range of motion in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) was captured for each specimen. METHODS: Twenty-four fresh frozen cadaveric spines (L3−L4/L5−S1) were divided into four groups with equivalent bone mineral density average scores (n=6). Specimens were instrumented with either (1) one static ALIF spacer; (2) one static oblique TLIF spacer (Ob); (3) two static bilateral-TLIF spacers (BiSt); or (4) two expandable bilateral-TLIF spacers (BiEx). Constructs were tested according to a load control protocol (§6.0Nm) before and after posterior fixation in FE, LB, and AR. Motion was captured for the (1) intact condition, (2) interbody spacer with posterior pedicle screw and rod fixation (Spacer+PI), and (3) spacer-alone (Spacer). Motion was normalized to intact, change in stability from intact to Spacer+PI and Spacer constructs was calculated, and statistical analyses were performed (p<0.05). RESULTS: All groups with PI reduced motion from intact in all modes. BiST resulted in comparable stability to ALIF in FE and AR. BiEX Spacer increased stability in all modes and was the only group to gain stability in FE (31% vs. -74%[ALIF], -46%[Ob], and -20%[BiST]). BiEX Spacer added significantly more stability than Ob Spacer in LB (49% vs. -7% [p=0.014]). CONCLUSIONS: The proposed bilateral-TLIF technique resulted in comparable stability to an ALIF spacer. Adding posterior fixation to the construct notably increased stability in all modes, emphasizing the need for supplemental fixation. When examining the sole effect of the spacer, only the expandable bilateral-TLIF spacer group gained stability from intact in all modes of motion, illustrating the biomechanical benefits of expandable technology. FDA DEVICE/DRUG STATUS: Interbody spacers are indicated for this application (Approved for this indication) https://doi.org/10.1016/j.spinee.2019.05.444
P21. Lumbar percutaneous pedicle screw breach rates: a comparison of robotic navigation versus conventional techniques Jaykar R. Panchmatia, MA, MD, FRCS (Tr & Orth)1, Alexander R. Vaccaro, MD, PhD2, Wenhai Wang, PhD3, Jonathan Harris3, Brandon Bucklen, PhD3; 1 Guy’s & St. Thomas’ Hospitals, London, United
Refer to onsite annual meeting presentations and postmeeting proceedings for possible referenced figures and tables. Authors are responsible for accurately reporting disclosure and FDA device/drug status at time of abstract submission.
Proceedings of the 34th Annual Meeting of the North American Spine Society / The Spine Journal 19 (2019) S158−S194
S168 2
Kingdom; Rothman Institute, Philadelphia, PA, US; 3 Globus Medical, Audubon, PA, US BACKGROUND CONTEXT: Pedicle screw fixation is an established means of stabilizing the thoracic and lumbar spine. Computer-assisted navigation has been demonstrated to improve the accuracy of pedicle screw placement. Few studies have compared screw breach rates using navigated robotic platforms. PURPOSE: The goal of this study is to determine if the use of a navigated robotic platform, Excelsius GPSTM (Globus Medical, Inc., Audubon, PA), minimizes pedicle breach in comparison to conventional techniques, and to determine why breach rates differ between these two techniques. STUDY DESIGN/SETTING: Cadaveric study. METHODS: Ten board-certified neuro- and orthopaedic spine surgeons inserted 80 percutaneous lumbar screws in 10 unembalmed human cadavers. Forty screws were inserted using conventional fluoroscopic guidance; 40 were inserted using a navigated robotic platform. None of the participating surgeons had prior experience with navigated robotic spine surgery. At the end of the study, each screw was assessed with CT scans, plain radiographs, and visual inspection to determine the presence or absence of pedicle breaches. RESULTS: Forty percent (16/40) of screws inserted using conventional fluoroscopic guidance breached the pedicle compared to 2.5% (1/40) of screws inserted with robot assistance (p=0.00005). High-grade breaches accounted for 17.5% (7/40) of screws inserted using fluoroscopic guidance. No high-grade breaches were observed in screws inserted using robotic assistance. High-grade breaches were defined as Gertzbein-Robbins grade C, D or E. Lateral breaches accounted for 88.2% (15/17) of all breaches. A subgroup analysis was performed of the 14 fluoroscopic screws that breached laterally. Detailed analyses revealed that the starting points of screws that breached laterally were significantly more lateral than those of the contralateral accurate screws (p=0.016). Pedicle screw diameter, length, and angulation in the transverse plane did not differ significantly between accurate screws and those that breached (p>0.05). Of the total 80 screws placed, robotic navigation allowed for use of both larger diameter (6.3§0.5mm vs. 6.6§0.6mm, p<0.001) and longer screws (46.9§3.5mm vs. 50.3§4.1mm, p=0.027). CONCLUSIONS: Use of a navigated robotic platform allows surgeons to identify an appropriate entry point, plan the pedicle screw trajectory based on that entry point, and execute insertion of the pedicle screw in a safe manner, which in the context of the current study resulted in a significantly lower pedicle breach rate compared to conventional techniques. FDA DEVICE/DRUG STATUS: Excelsius GPS (Approved for this indication).
PURPOSE: To evaluate kinematic and load-to-failure properties of a novel cement augmentation technique with an integrated lateral lumbar interbody fusion (LLIF) device, both alone and with unilateral pedicle fixation, in comparison with bilateral pedicle screws and non-integrated LLIF (BPS+S). STUDY DESIGN/SETTING: In vitrohuman cadaveric study. PATIENT SAMPLE: 12 cadaveric specimens. OUTCOME MEASURES: Range of motion (ROM) and ultimate load to failure. METHODS: Twelve specimens (L3−S1) underwent discectomy (L4 −L5). Specimens were separated into 3 groups: (1) BPS+S, (2) polymethylmethacrylate (PMMA), integrated LLIF, and unilateral pedicle screws. (PMMA+UPS+iS), and (3) PMMA with iSA (PMMA+iSA). Before LLIF insertion, a vertebroplasty needle inserted 3mm deep from the endplate at the vertical midline of the vertebral body (VB). The needle was repeatedly inserted through the cancellous bone, creating a cavity deep to the endplate. PMMA (3cc) was injected into the cavity, limited to approximately 25% of the operative endplates, followed by insertion of the LLIF device. After cement curing, flexion-extension, lateral bending and axial rotation were applied. Finally, a compressive load was applied to the segments until failure to assess spacer-endplate strength. RESULTS: No significant differences in BMD T-scores between BPS+S (-1.9§0.7), PMMA+UPS+iS (-1.8§0.5), and PMMA+iS (-1.8§0.7) groups were observed (P = 0.992). Operative constructs significantly reduced motion relative to intact specimens in all motion planes (P < 0.05). BPS+S provided the most stability, reducing motion by 71.6% to 86.4%, followed by PMMA+UPS+iS (68.1% to 79.4%) and PMMA+iSA (62.9% to 81.9%); no significant differences were found (P > 0.05). PMMA+UPS+iS provided the greatest resistance to failure (2290 N), followed by PMMA+iSA (1970 N), and lastly, BPS+S (1390 N); no significant differences were observed (P > 0.05). CONCLUSIONS: A novel technique of vertebral endplate cement augmentation via the lateral approach with an integrated interbody device for osteoporotic patients who would otherwise require posterior fixation to reduce likelihood of subsidence is proposed. The integrated lateral interbody spacer with vertebral endplate cement augmentation, both prior to and following unilateral pedicle fixation, was biomechanically equivalent to traditional anteroposterior fixation with non-integrated LLIF. The integrated device with cement augmentation moderately improved spacer-endplate interface compared to BPS+S in an osteoporotic model, increasing failure loads compared by 41.7%; the addition of unilateral fixation further increased resistance to failure (64.7%). Overall, results suggest integrated LLIF with cement may be a viable alternative in the presence of osteoporosis. FDA DEVICE/DRUG STATUS: Unavailable from authors at time of publication.
https://doi.org/10.1016/j.spinee.2019.05.445 https://doi.org/10.1016/j.spinee.2019.05.446 P22. Lumbar intervertebral spacer with cement augmentation of endplates and integrated screws as a fixation device in an osteoporotic model: an in vitro kinematic and load-to-failure study Rayshad Oshtory, MD, MBA1, Jonathan Harris2, Pavan D. Patel3, Belin A. Mirable4, Brandon Bucklen, PhD2; 1 Pacific Heights Spine Center, San Francisco, CA, US; 2 Globus Medical, Audubon, PA, US; 3 Drexel University, Philadelphia, PA, US; 4 University of Notre Dame, Notre Dame, IN, US BACKGROUND CONTEXT: Integrated LLIF stabilizes the spine and avoids complications related to posterior fixation. However, contraindications such as low bone mineral density (BMD) and older age can increase risk of subsidence. Traditional cement augmentation through cannulated pedicle screws enhances pedicle fixation and cage-endplate interface, yet may be disadvantageous due to associated paraspinal dissection, blood loss, and iatrogenic infection. Nevertheless, cement augmentation may be sufficient in preventing subsidence of stand-alone LLIF reconstructions in elderly patients. The lateral application of cement with integrated LLIF fixation has been introduced and requires kinematic and failure characterizations.
P23. Variations in stresses and strains along the rod during in-vitro loading of long fusion constructs Jennifer Lehrman, MS1, Anna G. Newcomb, MS2, Taylor Hostetler, BS1, Bernardo De Andrada Pereira, MD3, Jakub Godzik, MD3, Jay D. Turner, MD, PhD4, Brian Kelly, PhD1; 1 Barrow Neurological Institute, Phoenix, AZ, US; 2 St. Joseph’s Hospital and Medical Center, Phoenix, AZ, US; 3 Phoenix, AZ, US; 4 Barrow Brain and Spine, Phoenix, AZ, US BACKGROUND CONTEXT: Rod strains at one or two levels of spinal constructs are measured during in vitro studies to help evaluate the local biomechanical effects of different pedicle screw and rod (PSR) configurations. However, little is known about patterns of rod strain distribution particularly in longer PSR constructs that span the entire lumbar spine. PURPOSE: The purpose of this study was to analyze intervertebral rod strains at all six instrumented levels during multi-directional pure moment loading of lumbar spine constructs instrumented with PSR across T12-S. STUDY DESIGN/SETTING: In vitro biomechanical study using human cadaveric specimens.
Refer to onsite annual meeting presentations and postmeeting proceedings for possible referenced figures and tables. Authors are responsible for accurately reporting disclosure and FDA device/drug status at time of abstract submission.
ePosters: Biomechanics P19. Vertebra/implant response to cyclic loading is influenced by central strut support in intervertebral devices Antonio Valdevit, PhD; S-E-A, Columbus, OH, US BACKGROUND CONTEXT: The presence of a central strut may serve to strengthen a spinal spacer. However, it is unknown how a strut located in the central endplate region will influence vertebral body response under cyclic loading. PURPOSE: The authors hypothesized that devices with an open design will display comparable stiffness to devices with a central strut. Further, open devices would not restrict movement of the vertebral endplate and therefore display improved viscoelastic properties of the construct as compared to implants with a central strut. STUDY DESIGN/SETTING: Implants were fabricated from Ti-6Al-4V alloy represented an Open (contact area 427.5mm2) and Strutted device (contact area 407.9mm2 to 504.5mm2 depending on strut contact). PATIENT SAMPLE: Fourteen L4 or L5 porcine vertebra were randomly assigned to the implant groups. OUTCOME MEASURES: The ratio of the unloading/loading (loss/storage) stiffness values are used to compute Tan (d). Traditionally Tan (d) is associated with the loss and storage moduli. Such a calculation is not possible due to the complexity of contact area for a vertebral body. However, within any one specimen, the contact area is uniform and results in a scalable factor of the actual Tan (d). METHODS: Loading from 50N to 500N was applied at 1Hz for 500 cycles. Load and deformation data were acquired at 60Hz at 20 cycle intervals. The loading (storage) stiffness, unloading (loss) stiffness and mean Tan (d) were computed at each cycle interval and subjected to non-linear regression. The respective values for K (Rate) and Span (Change from initial value) for each implant type were compared using an unpaired t-test. RESULTS: For the loading stiffness, the regression analysis resulted in two rate parameters: KFast and KSLow. In the case of unloading stiffness, single rate functions were preferred. No statistical differences for loading stiffness were found between open and strutted devices for KFast (P>0.12) and KSlow (P>0.18). For the unloading stiffness, the K value for open devices was significantly decreased as compared to the strutted devices (P<0.0001). Open implants displayed statistically increased K value (P=0.0001) as compared to strutted devices (P<0.0001) for the Tan (d) analysis. Statistically decreased K values of open devices for unloading stiffness reflects a slow and gradual dissipation of energy to achieve equilibrium during cyclic loading. The gradual, more dissipative changes in energy dissipation of open devices may be beneficial in initiating and sustaining bone remodeling during strain hardening. The Tan (d) results for open devices indicated a rapid response via statistically increased K values to achieve a level of viscoelastic equilibrium (Span) that is significantly greater than that displayed by strutted implants. Increases in Tan (d) reflect improved dampening of the material.
S167
CONCLUSIONS: While metal devices encompassing an open concept are comparable in stiffness to devices containing a central strut, open designs can permit the unimpeded, viscoelastic response of the vertebral body which may be beneficial in the remodeling process. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. https://doi.org/10.1016/j.spinee.2019.05.443
P20. Titanium expandable interbody spacers placed via bilateral-TLIF provides stability similar to ALIF: an in-vitro range of motion analysis Steven A. Schopler, MD1, Samantha Greeley, BA2, Gerald Hayward, BS2, Hassaan P. Sheikh, BS2, Brandon Bucklen, PhD2; 1 Southern California Orthopedic Institute, Bakersfield, CA, US; 2 Globus Medical, Audubon, PA, US BACKGROUND CONTEXT: The transforaminal lumbar interbody fusion (TLIF) approach was developed to avoid the risks of the anterior lumbar interbody fusion (ALIF) and posterior lumbar interbody fusion (PLIF) approaches, and their potential for damage to the major vessels and the neurological elements, respectively. Construct stability of these various lumbar interbody fusion techniques is paramount to promote arthrodesis. Placement of two titanium expandable interbody spacers intradiscally following a bilateral facetectomy has the theoretical advantage of increased stability. PURPOSE: This biomechanical study aims to compare the stability of bilateral-TLIF with titanium expandable interbody spacers compared to various standard constructs in an in-vitro range of motion kinematic analysis in cadaveric models. STUDY DESIGN/SETTING: In vitro biomechanics study. OUTCOME MEASURES: Range of motion in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) was captured for each specimen. METHODS: Twenty-four fresh frozen cadaveric spines (L3−L4/L5−S1) were divided into four groups with equivalent bone mineral density average scores (n=6). Specimens were instrumented with either (1) one static ALIF spacer; (2) one static oblique TLIF spacer (Ob); (3) two static bilateral-TLIF spacers (BiSt); or (4) two expandable bilateral-TLIF spacers (BiEx). Constructs were tested according to a load control protocol (§6.0Nm) before and after posterior fixation in FE, LB, and AR. Motion was captured for the (1) intact condition, (2) interbody spacer with posterior pedicle screw and rod fixation (Spacer+PI), and (3) spacer-alone (Spacer). Motion was normalized to intact, change in stability from intact to Spacer+PI and Spacer constructs was calculated, and statistical analyses were performed (p<0.05). RESULTS: All groups with PI reduced motion from intact in all modes. BiST resulted in comparable stability to ALIF in FE and AR. BiEX Spacer increased stability in all modes and was the only group to gain stability in FE (31% vs. -74%[ALIF], -46%[Ob], and -20%[BiST]). BiEX Spacer added significantly more stability than Ob Spacer in LB (49% vs. -7% [p=0.014]). CONCLUSIONS: The proposed bilateral-TLIF technique resulted in comparable stability to an ALIF spacer. Adding posterior fixation to the construct notably increased stability in all modes, emphasizing the need for supplemental fixation. When examining the sole effect of the spacer, only the expandable bilateral-TLIF spacer group gained stability from intact in all modes of motion, illustrating the biomechanical benefits of expandable technology. FDA DEVICE/DRUG STATUS: Interbody spacers are indicated for this application (Approved for this indication) https://doi.org/10.1016/j.spinee.2019.05.444
P21. Lumbar percutaneous pedicle screw breach rates: a comparison of robotic navigation versus conventional techniques Jaykar R. Panchmatia, MA, MD, FRCS (Tr & Orth)1, Alexander R. Vaccaro, MD, PhD2, Wenhai Wang, PhD3, Jonathan Harris3, Brandon Bucklen, PhD3; 1 Guy’s & St. Thomas’ Hospitals, London, United
Refer to onsite annual meeting presentations and postmeeting proceedings for possible referenced figures and tables. Authors are responsible for accurately reporting disclosure and FDA device/drug status at time of abstract submission.
Proceedings of the 34th Annual Meeting of the North American Spine Society / The Spine Journal 19 (2019) S158−S194
S168 2
Kingdom; Rothman Institute, Philadelphia, PA, US; 3 Globus Medical, Audubon, PA, US BACKGROUND CONTEXT: Pedicle screw fixation is an established means of stabilizing the thoracic and lumbar spine. Computer-assisted navigation has been demonstrated to improve the accuracy of pedicle screw placement. Few studies have compared screw breach rates using navigated robotic platforms. PURPOSE: The goal of this study is to determine if the use of a navigated robotic platform, Excelsius GPSTM (Globus Medical, Inc., Audubon, PA), minimizes pedicle breach in comparison to conventional techniques, and to determine why breach rates differ between these two techniques. STUDY DESIGN/SETTING: Cadaveric study. METHODS: Ten board-certified neuro- and orthopaedic spine surgeons inserted 80 percutaneous lumbar screws in 10 unembalmed human cadavers. Forty screws were inserted using conventional fluoroscopic guidance; 40 were inserted using a navigated robotic platform. None of the participating surgeons had prior experience with navigated robotic spine surgery. At the end of the study, each screw was assessed with CT scans, plain radiographs, and visual inspection to determine the presence or absence of pedicle breaches. RESULTS: Forty percent (16/40) of screws inserted using conventional fluoroscopic guidance breached the pedicle compared to 2.5% (1/40) of screws inserted with robot assistance (p=0.00005). High-grade breaches accounted for 17.5% (7/40) of screws inserted using fluoroscopic guidance. No high-grade breaches were observed in screws inserted using robotic assistance. High-grade breaches were defined as Gertzbein-Robbins grade C, D or E. Lateral breaches accounted for 88.2% (15/17) of all breaches. A subgroup analysis was performed of the 14 fluoroscopic screws that breached laterally. Detailed analyses revealed that the starting points of screws that breached laterally were significantly more lateral than those of the contralateral accurate screws (p=0.016). Pedicle screw diameter, length, and angulation in the transverse plane did not differ significantly between accurate screws and those that breached (p>0.05). Of the total 80 screws placed, robotic navigation allowed for use of both larger diameter (6.3§0.5mm vs. 6.6§0.6mm, p<0.001) and longer screws (46.9§3.5mm vs. 50.3§4.1mm, p=0.027). CONCLUSIONS: Use of a navigated robotic platform allows surgeons to identify an appropriate entry point, plan the pedicle screw trajectory based on that entry point, and execute insertion of the pedicle screw in a safe manner, which in the context of the current study resulted in a significantly lower pedicle breach rate compared to conventional techniques. FDA DEVICE/DRUG STATUS: Excelsius GPS (Approved for this indication).
PURPOSE: To evaluate kinematic and load-to-failure properties of a novel cement augmentation technique with an integrated lateral lumbar interbody fusion (LLIF) device, both alone and with unilateral pedicle fixation, in comparison with bilateral pedicle screws and non-integrated LLIF (BPS+S). STUDY DESIGN/SETTING: In vitrohuman cadaveric study. PATIENT SAMPLE: 12 cadaveric specimens. OUTCOME MEASURES: Range of motion (ROM) and ultimate load to failure. METHODS: Twelve specimens (L3−S1) underwent discectomy (L4 −L5). Specimens were separated into 3 groups: (1) BPS+S, (2) polymethylmethacrylate (PMMA), integrated LLIF, and unilateral pedicle screws. (PMMA+UPS+iS), and (3) PMMA with iSA (PMMA+iSA). Before LLIF insertion, a vertebroplasty needle inserted 3mm deep from the endplate at the vertical midline of the vertebral body (VB). The needle was repeatedly inserted through the cancellous bone, creating a cavity deep to the endplate. PMMA (3cc) was injected into the cavity, limited to approximately 25% of the operative endplates, followed by insertion of the LLIF device. After cement curing, flexion-extension, lateral bending and axial rotation were applied. Finally, a compressive load was applied to the segments until failure to assess spacer-endplate strength. RESULTS: No significant differences in BMD T-scores between BPS+S (-1.9§0.7), PMMA+UPS+iS (-1.8§0.5), and PMMA+iS (-1.8§0.7) groups were observed (P = 0.992). Operative constructs significantly reduced motion relative to intact specimens in all motion planes (P < 0.05). BPS+S provided the most stability, reducing motion by 71.6% to 86.4%, followed by PMMA+UPS+iS (68.1% to 79.4%) and PMMA+iSA (62.9% to 81.9%); no significant differences were found (P > 0.05). PMMA+UPS+iS provided the greatest resistance to failure (2290 N), followed by PMMA+iSA (1970 N), and lastly, BPS+S (1390 N); no significant differences were observed (P > 0.05). CONCLUSIONS: A novel technique of vertebral endplate cement augmentation via the lateral approach with an integrated interbody device for osteoporotic patients who would otherwise require posterior fixation to reduce likelihood of subsidence is proposed. The integrated lateral interbody spacer with vertebral endplate cement augmentation, both prior to and following unilateral pedicle fixation, was biomechanically equivalent to traditional anteroposterior fixation with non-integrated LLIF. The integrated device with cement augmentation moderately improved spacer-endplate interface compared to BPS+S in an osteoporotic model, increasing failure loads compared by 41.7%; the addition of unilateral fixation further increased resistance to failure (64.7%). Overall, results suggest integrated LLIF with cement may be a viable alternative in the presence of osteoporosis. FDA DEVICE/DRUG STATUS: Unavailable from authors at time of publication.
https://doi.org/10.1016/j.spinee.2019.05.445 https://doi.org/10.1016/j.spinee.2019.05.446 P22. Lumbar intervertebral spacer with cement augmentation of endplates and integrated screws as a fixation device in an osteoporotic model: an in vitro kinematic and load-to-failure study Rayshad Oshtory, MD, MBA1, Jonathan Harris2, Pavan D. Patel3, Belin A. Mirable4, Brandon Bucklen, PhD2; 1 Pacific Heights Spine Center, San Francisco, CA, US; 2 Globus Medical, Audubon, PA, US; 3 Drexel University, Philadelphia, PA, US; 4 University of Notre Dame, Notre Dame, IN, US BACKGROUND CONTEXT: Integrated LLIF stabilizes the spine and avoids complications related to posterior fixation. However, contraindications such as low bone mineral density (BMD) and older age can increase risk of subsidence. Traditional cement augmentation through cannulated pedicle screws enhances pedicle fixation and cage-endplate interface, yet may be disadvantageous due to associated paraspinal dissection, blood loss, and iatrogenic infection. Nevertheless, cement augmentation may be sufficient in preventing subsidence of stand-alone LLIF reconstructions in elderly patients. The lateral application of cement with integrated LLIF fixation has been introduced and requires kinematic and failure characterizations.
P23. Variations in stresses and strains along the rod during in-vitro loading of long fusion constructs Jennifer Lehrman, MS1, Anna G. Newcomb, MS2, Taylor Hostetler, BS1, Bernardo De Andrada Pereira, MD3, Jakub Godzik, MD3, Jay D. Turner, MD, PhD4, Brian Kelly, PhD1; 1 Barrow Neurological Institute, Phoenix, AZ, US; 2 St. Joseph’s Hospital and Medical Center, Phoenix, AZ, US; 3 Phoenix, AZ, US; 4 Barrow Brain and Spine, Phoenix, AZ, US BACKGROUND CONTEXT: Rod strains at one or two levels of spinal constructs are measured during in vitro studies to help evaluate the local biomechanical effects of different pedicle screw and rod (PSR) configurations. However, little is known about patterns of rod strain distribution particularly in longer PSR constructs that span the entire lumbar spine. PURPOSE: The purpose of this study was to analyze intervertebral rod strains at all six instrumented levels during multi-directional pure moment loading of lumbar spine constructs instrumented with PSR across T12-S. STUDY DESIGN/SETTING: In vitro biomechanical study using human cadaveric specimens.
Refer to onsite annual meeting presentations and postmeeting proceedings for possible referenced figures and tables. Authors are responsible for accurately reporting disclosure and FDA device/drug status at time of abstract submission.