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implant response to cyclic loading is influenced by central strut support in intervertebral devices
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.
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.
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.