Brandon Santoni - Academia.edu (original) (raw)

Papers by Brandon Santoni

Clinical Orthopaedics and Related Research, 2008

Structural bone allografts are used to reconstruct large skeletal defects after tumor surgery. Al... more Structural bone allografts are used to reconstruct large skeletal defects after tumor surgery. Although allograft-related complications are declining, the use of perioperative radiation therapy is associated with a poorer outcome. Recently, BMP-2 levels in the host bed were reportedly diminished after exposure to radiation doses consistent with those used perioperatively to treat musculoskeletal sarcoma. Reintroduction of this osteogenic protein may circumvent the deleterious effects of preoperative radiation on allograft incorporation. We introduced a novel polymeric BMP-2 gene delivery system into the host-allograft junctions at the time of transplantation in an ovine tibial defect model with or without preoperative exposure to 50 Gy radiation. After 4 months, we noted no radiographic or histologic improvements in allograft incorporation after preoperative radiation and BMP-2 reintroduction; however, 50 Gy radiation was associated with increased porosity in the interface regions and poorer radiographic healing. We identified no BMP2-expressing cells or protein in the interface at the study end point, suggesting the polymeric gene delivery system was unable to promote extended expression of the protein or induce a healing response. Although gene therapy may hold promise as a novel technique to improve allograft incorporation, our data do not support that contention with the current approach.

Veterinary surgery : VS, 2011

ASME 2007 Summer Bioengineering Conference, 2007

Structural bone allografts are used to reconstruct large skeletal defects resulting from trauma, ... more Structural bone allografts are used to reconstruct large skeletal defects resulting from trauma, tumor resection, or revision arthroplasty. Though used for over a century, bone allografts suffer from a high rate of mechanical failure due to limited graft revitalization even after extended periods in vivo. The current study evaluated the mechanical properties of longitudinally perforated cortical bone allografts (LAP) that have been shown to promote accelerated graft incorporation in a large animal model. The compressive and tensile properties of longitudinally perforated allograft specimens, as determined through uniaxial compression and diametral compression tests, respectively, were not significantly affected by the presence of the conduit. However, transversely perforated grafts (TAP) demonstrated a marked decrease in tensile capacity (p = 0.04). Finite element analysis demonstrated moderate increases in the maximum principal stresses in LAP specimens while TAP models indicated an 83.4% increase in maximum principle stress near the conduit on the endosteal surface of the graft. This research and the previous in vivo study suggest that LAP adequately serves as an internal template within the cortical bone allograft for osseous apposition and revitalization without adversely affecting the structural or mechanical integrity of the graft.

IEEE Journal of Selected Topics in Quantum Electronics, 2010

We designed, fabricated, and characterized metamaterial-based RF-microelectromechanical system (R... more We designed, fabricated, and characterized metamaterial-based RF-microelectromechanical system (RF-MEMS) strain sensors that incorporate multiple split ring resonators (SRRs) in a compact nested architecture to measure strain telemetrically. We also showed biocompatibility of these strain sensors in an animal model. With these devices, our bioimplantable wireless metamaterial sensors are intended, to enable clinicians, to quantitatively evaluate the progression of long-bone fracture healing by monitoring the strain on the implantable fracture fixation hardware in real time. In operation, the transmission spectrum of the metamaterial sensor attached to the implantable fixture is changed when an external load is applied to the fixture, and from this change, the strain is recorded remotely. By employing telemetric characterizations, we reduced the operating frequency and enhanced the sensitivity of our novel nested SRR architecture compared to the conventional SRR structure. The nested SRR structure exhibited a higher sensitivity of 1.09 kHz/kgf operating at lower frequency compared to the classical SRR that demonstrated a sensitivity of 0.72 kHz/kgf. Using soft tissue medium, we achieved the best sensitivity level of 4.00 kHz/kgf with our nested SRR sensor. Ultimately, the laboratory characterization and in vivo biocompatibility studies support further development and characterization of a fracture healing system based on implantable nested SRR.

International Journal of Spine Surgery, 2014

Mechanically replacing one or more pain generating articulations in the functional spinal unit (F... more Mechanically replacing one or more pain generating articulations in the functional spinal unit (FSU) may be a motion preservation alternative to arthrodesis at the affected level. Baseline biomechanical data elucidating the quantity and quality of motion in such arthroplasty constructs is non-existent. The purpose of the study was to quantify the motion-preserving effect of a posterior total disc replacement (PDR) combined with a unilateral facet replacement (FR) system at a single lumbar level (L4-L5). We hypothesized that reinforcement of the FSU with unilateral FR to replace the resected, native facet joint following PDR implantation would restore quality and quantity of motion and additionally not change biomechanics at the adjacent levels. In-vitro study using human cadaveric lumbar spines. Six (n = 6) cadaveric lumbar spines (L1-S1) were evaluated using a pure-moment stability testing protocol (±7.5 Nm) in flexion-extension (F/E), lateral bending (LB) and axial rotation (AR). Each specimen was tested in: (1) intact; (2) unilateral FR; and (3) unilateral FR + PDR conditions. Index and adjacent level ROM (using hybrid protocol) were determined opto-electronically. Interpedicular travel (IPT) and instantaneous center of rotation (ICR) at the index level were radiographically determined for each condition. ROM, ICR, and IPT measurements were compared (repeated measures ANOVA) between the three conditions. Compared to the intact spine, no significant changes in F/E, LB or AR ROM were identified as a result of unilateral FR or unilateral FR + PDR. No significant changes in adjacent L3-L4 or L5-S1 ROM were identified in any loading mode. No significant differences in IPT were identified between the three test conditions in F/E, LB or AR at the L4-L5 level. The ICRs qualitatively were similar for the intact and unilateral FR conditions and appeared to follow placement (along the anterior-posterior (AP) direction) of the PDR in the disc space. Biomechanically, quantity and quality of motion are maintained with combined unilateral FR + PDR at a single lumbar spinal level.

The Spine Journal, 2011

PATIENT SAMPLE: 73 patients, age 46610 years, received 2 to 4-level fusion of L2-S1 vertebrae. Th... more PATIENT SAMPLE: 73 patients, age 46610 years, received 2 to 4-level fusion of L2-S1 vertebrae. Thrity-five patients received hardware removal 230630 days post-implantation. OUTCOME MEASURES: Outcome measures included: insertion torque, immediate removal torque, ultimate removal torque, evoked EMG stimulus threshold, screw size, and pedicle-screw clearance (pedicle thicknessscrew diameter). METHODS: Pedicle screw insertion (n5274) and removal (n5207) torques were measured using a manual torque wrench. Immediately upon insertion, pedicle screws were backed-out to assess immediate removal torque to ensure the insertion torque was not artificially elevated due to initial placement (n510). Paired samples (n526) were measured for both insertion and removal. EMG stimulation threshold currents for screw holes were measured prior to insertion and following removal. Paired and unpaired two-tailed t-tests were used to compare groups, as appropriate, with significance set at p!.05. Linear regressions were performed using Graph-Pad (Prism). All data reported as mean6SD. RESULTS: There were no differences between insertion and immediate removal torque (p5.56). However, upon ultimate removal, torque measure-

The Spine Journal, 2014

Despite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior... more Despite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior cervical discectomy and fusion (ACDF) procedures, there is little published biomechanical data describing its stabilizing effect relative to the traditional anterior plating technique over two contiguous levels. To biomechanically compare the acute stability conferred by a stand-alone interbody fusion device with three integrated fixation screws ("anchored cage") with a traditional six-hole rigid anterior plate in a two contiguous levels (C4-C5+C5-C6) fusion construct. We hypothesized that the anchored cage would confer comparable segmental rigidity to the cage and anterior plate construct. A biomechanical laboratory study using cadaveric human cervical spines. Seven (n=7) cadaveric human cervical spines (C3-C7) were subjected to quasistatic, pure-moment loading (±1.5 Nm) in flexion-extension (flex/ext), right/left lateral bending (RB/LB), and right/left axial rotation (RR/LR) for the following test conditions: intact; after discectomy and insertion of the AIC at C4-C5 and C5-C6 with anchoring screws engaged; after the removal of the integrated anchoring screws and instrumentation of an anterior locking plate (ALP) over both levels; and cage-only (CO) configuration with screws and anterior plate removed. Intervertebral range of motion (ROM) at the instrumented levels was the primary biomechanical outcome. Flex/ext, RB/LB, and RR/LR ROMs were significantly reduced (p<.001) over both levels by AIC and ALP constructs relative to the CO construct. Significant reduction in flex/ext motion was achieved with the ALP (6.8±3.7) relative to the AIC (10.2°±4.6°) (p=.041) construct. No significant differences were seen in ROM reductions over the two levels between the AIC and APL groups in lateral bending or axial rotation (p>.826). The anchored cage fusion construct conferred similar acute biomechanical stability in lateral bending and axial rotation ROMs relative to rigid anterior plating. We identified a statistically significant reduction (Δ=3.4°, combined over two levels) in sagittal plane ROM conferred by the ALP relative to the AIC construct. Our biomechanical findings may support the clinical use of no-profile integrated interbody devices over two contiguous levels in ACDF.

The Spine Journal, 2011

PATIENT SAMPLE: 73 patients, age 46610 years, received 2 to 4-level fusion of L2-S1 vertebrae. Th... more PATIENT SAMPLE: 73 patients, age 46610 years, received 2 to 4-level fusion of L2-S1 vertebrae. Thrity-five patients received hardware removal 230630 days post-implantation. OUTCOME MEASURES: Outcome measures included: insertion torque, immediate removal torque, ultimate removal torque, evoked EMG stimulus threshold, screw size, and pedicle-screw clearance (pedicle thicknessscrew diameter). METHODS: Pedicle screw insertion (n5274) and removal (n5207) torques were measured using a manual torque wrench. Immediately upon insertion, pedicle screws were backed-out to assess immediate removal torque to ensure the insertion torque was not artificially elevated due to initial placement (n510). Paired samples (n526) were measured for both insertion and removal. EMG stimulation threshold currents for screw holes were measured prior to insertion and following removal. Paired and unpaired two-tailed t-tests were used to compare groups, as appropriate, with significance set at p!.05. Linear regressions were performed using Graph-Pad (Prism). All data reported as mean6SD. RESULTS: There were no differences between insertion and immediate removal torque (p5.56). However, upon ultimate removal, torque measure-

The Spine Journal, 2014

Despite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior... more Despite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior cervical discectomy and fusion (ACDF) procedures, there is little published biomechanical data describing its stabilizing effect relative to the traditional anterior plating technique over two contiguous levels. To biomechanically compare the acute stability conferred by a stand-alone interbody fusion device with three integrated fixation screws ("anchored cage") with a traditional six-hole rigid anterior plate in a two contiguous levels (C4-C5+C5-C6) fusion construct. We hypothesized that the anchored cage would confer comparable segmental rigidity to the cage and anterior plate construct. A biomechanical laboratory study using cadaveric human cervical spines. Seven (n=7) cadaveric human cervical spines (C3-C7) were subjected to quasistatic, pure-moment loading (±1.5 Nm) in flexion-extension (flex/ext), right/left lateral bending (RB/LB), and right/left axial rotation (RR/LR) for the following test conditions: intact; after discectomy and insertion of the AIC at C4-C5 and C5-C6 with anchoring screws engaged; after the removal of the integrated anchoring screws and instrumentation of an anterior locking plate (ALP) over both levels; and cage-only (CO) configuration with screws and anterior plate removed. Intervertebral range of motion (ROM) at the instrumented levels was the primary biomechanical outcome. Flex/ext, RB/LB, and RR/LR ROMs were significantly reduced (p<.001) over both levels by AIC and ALP constructs relative to the CO construct. Significant reduction in flex/ext motion was achieved with the ALP (6.8±3.7) relative to the AIC (10.2°±4.6°) (p=.041) construct. No significant differences were seen in ROM reductions over the two levels between the AIC and APL groups in lateral bending or axial rotation (p>.826). The anchored cage fusion construct conferred similar acute biomechanical stability in lateral bending and axial rotation ROMs relative to rigid anterior plating. We identified a statistically significant reduction (Δ=3.4°, combined over two levels) in sagittal plane ROM conferred by the ALP relative to the AIC construct. Our biomechanical findings may support the clinical use of no-profile integrated interbody devices over two contiguous levels in ACDF.

The Spine Journal, 2014

No profile, integrated interbody cages are designed to act as implants for cervical spine fusion,... more No profile, integrated interbody cages are designed to act as implants for cervical spine fusion, which obviates the need for additional internal fixation, combining the functionality of an interbody device and the stabilizing benefits of an anterior cervical plate. Biomechanical data are needed to determine if integrated interbody constructs afford similar stability to anterior plating in single-level cervical spine fusion constructs. The purpose of this study was to biomechanically quantify the acute stabilizing effect conferred by a single low-profile device design with three integrated screws ("anchored cage"), and compare the range of motion reductions to those conferred by a standard four-hole rigid anterior plate following instrumentation at the C5-C6 level. We hypothesized that the anchored cage would confer comparable postoperative segmental rigidity to the cage and anterior plate construct. Biomechanical laboratory study of human cadaveric spines. Seven human cadaveric cervical spines (C3-C7) were biomechanically evaluated using a nondestructive, nonconstraining, pure-moment loading protocol with loads applied in flexion, extension, lateral bending (right+left), and axial rotation (left+right) for the intact and instrumented conditions. Range of motion (ROM) at the instrumented level was the primary biomechanical outcome. Spines were loaded quasi-statically up to 1.5 N-m in 0.5 N-m increments and ROM at the C5-C6 index level was recorded. Each specimen was tested in the following conditions: 1. Intact 2. Discectomy+anchored cage (STA) 3. Anchored cage (screws removed)+anterior locking plate (ALP) 4. Anchored cage only, without screws or plates (CO) RESULTS: ROM at the C5-C6 level was not statistically different in any motion plane between the STA and ALP treatment conditions (p>.407). STA demonstrated significant reductions in flexion/extension, lateral bending, and axial rotation ROM when compared with the CO condition (p<.022). In this in vitro biomechanical study, the anchored cage with three integrated screws afforded biomechanical stability comparable to that of the standard interbody cage+anterior plate cervical spine fusion approach. Due to its low profile design, this anchored cage device may avoid morbidities associated with standard anterior plating, such as dysphagia.

Clinical Orthopaedics and Related Research, 2008

Structural bone allografts are used to reconstruct large skeletal defects after tumor surgery. Al... more Structural bone allografts are used to reconstruct large skeletal defects after tumor surgery. Although allograft-related complications are declining, the use of perioperative radiation therapy is associated with a poorer outcome. Recently, BMP-2 levels in the host bed were reportedly diminished after exposure to radiation doses consistent with those used perioperatively to treat musculoskeletal sarcoma. Reintroduction of this osteogenic protein may circumvent the deleterious effects of preoperative radiation on allograft incorporation. We introduced a novel polymeric BMP-2 gene delivery system into the host-allograft junctions at the time of transplantation in an ovine tibial defect model with or without preoperative exposure to 50 Gy radiation. After 4 months, we noted no radiographic or histologic improvements in allograft incorporation after preoperative radiation and BMP-2 reintroduction; however, 50 Gy radiation was associated with increased porosity in the interface regions and poorer radiographic healing. We identified no BMP2-expressing cells or protein in the interface at the study end point, suggesting the polymeric gene delivery system was unable to promote extended expression of the protein or induce a healing response. Although gene therapy may hold promise as a novel technique to improve allograft incorporation, our data do not support that contention with the current approach.

Veterinary surgery : VS, 2011

ASME 2007 Summer Bioengineering Conference, 2007

Structural bone allografts are used to reconstruct large skeletal defects resulting from trauma, ... more Structural bone allografts are used to reconstruct large skeletal defects resulting from trauma, tumor resection, or revision arthroplasty. Though used for over a century, bone allografts suffer from a high rate of mechanical failure due to limited graft revitalization even after extended periods in vivo. The current study evaluated the mechanical properties of longitudinally perforated cortical bone allografts (LAP) that have been shown to promote accelerated graft incorporation in a large animal model. The compressive and tensile properties of longitudinally perforated allograft specimens, as determined through uniaxial compression and diametral compression tests, respectively, were not significantly affected by the presence of the conduit. However, transversely perforated grafts (TAP) demonstrated a marked decrease in tensile capacity (p = 0.04). Finite element analysis demonstrated moderate increases in the maximum principal stresses in LAP specimens while TAP models indicated an 83.4% increase in maximum principle stress near the conduit on the endosteal surface of the graft. This research and the previous in vivo study suggest that LAP adequately serves as an internal template within the cortical bone allograft for osseous apposition and revitalization without adversely affecting the structural or mechanical integrity of the graft.

IEEE Journal of Selected Topics in Quantum Electronics, 2010

We designed, fabricated, and characterized metamaterial-based RF-microelectromechanical system (R... more We designed, fabricated, and characterized metamaterial-based RF-microelectromechanical system (RF-MEMS) strain sensors that incorporate multiple split ring resonators (SRRs) in a compact nested architecture to measure strain telemetrically. We also showed biocompatibility of these strain sensors in an animal model. With these devices, our bioimplantable wireless metamaterial sensors are intended, to enable clinicians, to quantitatively evaluate the progression of long-bone fracture healing by monitoring the strain on the implantable fracture fixation hardware in real time. In operation, the transmission spectrum of the metamaterial sensor attached to the implantable fixture is changed when an external load is applied to the fixture, and from this change, the strain is recorded remotely. By employing telemetric characterizations, we reduced the operating frequency and enhanced the sensitivity of our novel nested SRR architecture compared to the conventional SRR structure. The nested SRR structure exhibited a higher sensitivity of 1.09 kHz/kgf operating at lower frequency compared to the classical SRR that demonstrated a sensitivity of 0.72 kHz/kgf. Using soft tissue medium, we achieved the best sensitivity level of 4.00 kHz/kgf with our nested SRR sensor. Ultimately, the laboratory characterization and in vivo biocompatibility studies support further development and characterization of a fracture healing system based on implantable nested SRR.

International Journal of Spine Surgery, 2014

Mechanically replacing one or more pain generating articulations in the functional spinal unit (F... more Mechanically replacing one or more pain generating articulations in the functional spinal unit (FSU) may be a motion preservation alternative to arthrodesis at the affected level. Baseline biomechanical data elucidating the quantity and quality of motion in such arthroplasty constructs is non-existent. The purpose of the study was to quantify the motion-preserving effect of a posterior total disc replacement (PDR) combined with a unilateral facet replacement (FR) system at a single lumbar level (L4-L5). We hypothesized that reinforcement of the FSU with unilateral FR to replace the resected, native facet joint following PDR implantation would restore quality and quantity of motion and additionally not change biomechanics at the adjacent levels. In-vitro study using human cadaveric lumbar spines. Six (n = 6) cadaveric lumbar spines (L1-S1) were evaluated using a pure-moment stability testing protocol (±7.5 Nm) in flexion-extension (F/E), lateral bending (LB) and axial rotation (AR). Each specimen was tested in: (1) intact; (2) unilateral FR; and (3) unilateral FR + PDR conditions. Index and adjacent level ROM (using hybrid protocol) were determined opto-electronically. Interpedicular travel (IPT) and instantaneous center of rotation (ICR) at the index level were radiographically determined for each condition. ROM, ICR, and IPT measurements were compared (repeated measures ANOVA) between the three conditions. Compared to the intact spine, no significant changes in F/E, LB or AR ROM were identified as a result of unilateral FR or unilateral FR + PDR. No significant changes in adjacent L3-L4 or L5-S1 ROM were identified in any loading mode. No significant differences in IPT were identified between the three test conditions in F/E, LB or AR at the L4-L5 level. The ICRs qualitatively were similar for the intact and unilateral FR conditions and appeared to follow placement (along the anterior-posterior (AP) direction) of the PDR in the disc space. Biomechanically, quantity and quality of motion are maintained with combined unilateral FR + PDR at a single lumbar spinal level.

The Spine Journal, 2011

PATIENT SAMPLE: 73 patients, age 46610 years, received 2 to 4-level fusion of L2-S1 vertebrae. Th... more PATIENT SAMPLE: 73 patients, age 46610 years, received 2 to 4-level fusion of L2-S1 vertebrae. Thrity-five patients received hardware removal 230630 days post-implantation. OUTCOME MEASURES: Outcome measures included: insertion torque, immediate removal torque, ultimate removal torque, evoked EMG stimulus threshold, screw size, and pedicle-screw clearance (pedicle thicknessscrew diameter). METHODS: Pedicle screw insertion (n5274) and removal (n5207) torques were measured using a manual torque wrench. Immediately upon insertion, pedicle screws were backed-out to assess immediate removal torque to ensure the insertion torque was not artificially elevated due to initial placement (n510). Paired samples (n526) were measured for both insertion and removal. EMG stimulation threshold currents for screw holes were measured prior to insertion and following removal. Paired and unpaired two-tailed t-tests were used to compare groups, as appropriate, with significance set at p!.05. Linear regressions were performed using Graph-Pad (Prism). All data reported as mean6SD. RESULTS: There were no differences between insertion and immediate removal torque (p5.56). However, upon ultimate removal, torque measure-

The Spine Journal, 2014

Despite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior... more Despite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior cervical discectomy and fusion (ACDF) procedures, there is little published biomechanical data describing its stabilizing effect relative to the traditional anterior plating technique over two contiguous levels. To biomechanically compare the acute stability conferred by a stand-alone interbody fusion device with three integrated fixation screws ("anchored cage") with a traditional six-hole rigid anterior plate in a two contiguous levels (C4-C5+C5-C6) fusion construct. We hypothesized that the anchored cage would confer comparable segmental rigidity to the cage and anterior plate construct. A biomechanical laboratory study using cadaveric human cervical spines. Seven (n=7) cadaveric human cervical spines (C3-C7) were subjected to quasistatic, pure-moment loading (±1.5 Nm) in flexion-extension (flex/ext), right/left lateral bending (RB/LB), and right/left axial rotation (RR/LR) for the following test conditions: intact; after discectomy and insertion of the AIC at C4-C5 and C5-C6 with anchoring screws engaged; after the removal of the integrated anchoring screws and instrumentation of an anterior locking plate (ALP) over both levels; and cage-only (CO) configuration with screws and anterior plate removed. Intervertebral range of motion (ROM) at the instrumented levels was the primary biomechanical outcome. Flex/ext, RB/LB, and RR/LR ROMs were significantly reduced (p<.001) over both levels by AIC and ALP constructs relative to the CO construct. Significant reduction in flex/ext motion was achieved with the ALP (6.8±3.7) relative to the AIC (10.2°±4.6°) (p=.041) construct. No significant differences were seen in ROM reductions over the two levels between the AIC and APL groups in lateral bending or axial rotation (p>.826). The anchored cage fusion construct conferred similar acute biomechanical stability in lateral bending and axial rotation ROMs relative to rigid anterior plating. We identified a statistically significant reduction (Δ=3.4°, combined over two levels) in sagittal plane ROM conferred by the ALP relative to the AIC construct. Our biomechanical findings may support the clinical use of no-profile integrated interbody devices over two contiguous levels in ACDF.

The Spine Journal, 2011

PATIENT SAMPLE: 73 patients, age 46610 years, received 2 to 4-level fusion of L2-S1 vertebrae. Th... more PATIENT SAMPLE: 73 patients, age 46610 years, received 2 to 4-level fusion of L2-S1 vertebrae. Thrity-five patients received hardware removal 230630 days post-implantation. OUTCOME MEASURES: Outcome measures included: insertion torque, immediate removal torque, ultimate removal torque, evoked EMG stimulus threshold, screw size, and pedicle-screw clearance (pedicle thicknessscrew diameter). METHODS: Pedicle screw insertion (n5274) and removal (n5207) torques were measured using a manual torque wrench. Immediately upon insertion, pedicle screws were backed-out to assess immediate removal torque to ensure the insertion torque was not artificially elevated due to initial placement (n510). Paired samples (n526) were measured for both insertion and removal. EMG stimulation threshold currents for screw holes were measured prior to insertion and following removal. Paired and unpaired two-tailed t-tests were used to compare groups, as appropriate, with significance set at p!.05. Linear regressions were performed using Graph-Pad (Prism). All data reported as mean6SD. RESULTS: There were no differences between insertion and immediate removal torque (p5.56). However, upon ultimate removal, torque measure-

The Spine Journal, 2014

Despite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior... more Despite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior cervical discectomy and fusion (ACDF) procedures, there is little published biomechanical data describing its stabilizing effect relative to the traditional anterior plating technique over two contiguous levels. To biomechanically compare the acute stability conferred by a stand-alone interbody fusion device with three integrated fixation screws ("anchored cage") with a traditional six-hole rigid anterior plate in a two contiguous levels (C4-C5+C5-C6) fusion construct. We hypothesized that the anchored cage would confer comparable segmental rigidity to the cage and anterior plate construct. A biomechanical laboratory study using cadaveric human cervical spines. Seven (n=7) cadaveric human cervical spines (C3-C7) were subjected to quasistatic, pure-moment loading (±1.5 Nm) in flexion-extension (flex/ext), right/left lateral bending (RB/LB), and right/left axial rotation (RR/LR) for the following test conditions: intact; after discectomy and insertion of the AIC at C4-C5 and C5-C6 with anchoring screws engaged; after the removal of the integrated anchoring screws and instrumentation of an anterior locking plate (ALP) over both levels; and cage-only (CO) configuration with screws and anterior plate removed. Intervertebral range of motion (ROM) at the instrumented levels was the primary biomechanical outcome. Flex/ext, RB/LB, and RR/LR ROMs were significantly reduced (p<.001) over both levels by AIC and ALP constructs relative to the CO construct. Significant reduction in flex/ext motion was achieved with the ALP (6.8±3.7) relative to the AIC (10.2°±4.6°) (p=.041) construct. No significant differences were seen in ROM reductions over the two levels between the AIC and APL groups in lateral bending or axial rotation (p>.826). The anchored cage fusion construct conferred similar acute biomechanical stability in lateral bending and axial rotation ROMs relative to rigid anterior plating. We identified a statistically significant reduction (Δ=3.4°, combined over two levels) in sagittal plane ROM conferred by the ALP relative to the AIC construct. Our biomechanical findings may support the clinical use of no-profile integrated interbody devices over two contiguous levels in ACDF.

The Spine Journal, 2014

No profile, integrated interbody cages are designed to act as implants for cervical spine fusion,... more No profile, integrated interbody cages are designed to act as implants for cervical spine fusion, which obviates the need for additional internal fixation, combining the functionality of an interbody device and the stabilizing benefits of an anterior cervical plate. Biomechanical data are needed to determine if integrated interbody constructs afford similar stability to anterior plating in single-level cervical spine fusion constructs. The purpose of this study was to biomechanically quantify the acute stabilizing effect conferred by a single low-profile device design with three integrated screws ("anchored cage"), and compare the range of motion reductions to those conferred by a standard four-hole rigid anterior plate following instrumentation at the C5-C6 level. We hypothesized that the anchored cage would confer comparable postoperative segmental rigidity to the cage and anterior plate construct. Biomechanical laboratory study of human cadaveric spines. Seven human cadaveric cervical spines (C3-C7) were biomechanically evaluated using a nondestructive, nonconstraining, pure-moment loading protocol with loads applied in flexion, extension, lateral bending (right+left), and axial rotation (left+right) for the intact and instrumented conditions. Range of motion (ROM) at the instrumented level was the primary biomechanical outcome. Spines were loaded quasi-statically up to 1.5 N-m in 0.5 N-m increments and ROM at the C5-C6 index level was recorded. Each specimen was tested in the following conditions: 1. Intact 2. Discectomy+anchored cage (STA) 3. Anchored cage (screws removed)+anterior locking plate (ALP) 4. Anchored cage only, without screws or plates (CO) RESULTS: ROM at the C5-C6 level was not statistically different in any motion plane between the STA and ALP treatment conditions (p>.407). STA demonstrated significant reductions in flexion/extension, lateral bending, and axial rotation ROM when compared with the CO condition (p<.022). In this in vitro biomechanical study, the anchored cage with three integrated screws afforded biomechanical stability comparable to that of the standard interbody cage+anterior plate cervical spine fusion approach. Due to its low profile design, this anchored cage device may avoid morbidities associated with standard anterior plating, such as dysphagia.