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de Andrada Pereira B, O'Neill LK, Sawa AGU, Zhou JJ, Wangsawatwong P, Lehrman JN, Godzik J, Oldham AJ, Turner JD, Kelly BP, Uribe JS. Biomechanical Assessment of a Novel Sharp-Tipped Screw for 1-Step Minimally Invasive Pedicle Screw Placement Under Navigation. Int J Spine Surg 2023; 17:484-491. [PMID: 37076254 PMCID: PMC10478698 DOI: 10.14444/8470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/21/2023] Open
Abstract
BACKGROUND The objective of this study was to assess the pullout force of a novel sharp-tipped screw developed for single-step, minimally invasive pedicle screw placement guided by neuronavigation compared with the pullout force for traditional screws. METHODS A total of 60 human cadaveric lumbar pedicles were studied. Three different screw insertion techniques were compared: (A) Jamshidi needle and Kirschner wire without tapping; (B) Jamshidi needle and Kirschner wire with tapping; and (C) sharp-tipped screw insertion. Pullout tests were performed at a displacement rate of 10 mm/min recorded at 20 Hz. Mean values of these parameters were compared using paired t tests (left vs right in the same specimen): A vs B, A vs C, and B vs C. Additionally, 3 L1-L5 spine models were used for timing each screw insertion technique for a total of 10 screw insertions for each technique. Insertion times were compared using 1-way analysis of variance. RESULTS The mean pullout force for insertion technique A was 1462.3 (597.5) N; for technique B, it was 1693.5 (805.0) N; and for technique C, it was 1319.0 (735.7) N. There was no statistically significant difference in pullout force between techniques (P > 0.08). The average insertion time for condition C was significantly less than that for conditions A and B (P < 0.001). CONCLUSIONS The pullout force of the novel sharp-tipped screw placement technique is equivalent to that of traditional techniques. The sharp-tipped screw placement technique appears biomechanically viable and has the advantage of saving time during insertion. CLINICAL RELEVANCE Single-step screw placement using high resolution 3-dimensional navigation has the potential to streamline workflow and reduce operative time. LEVEL OF EVIDENCE: 5
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Affiliation(s)
- Bernardo de Andrada Pereira
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Luke K O'Neill
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Anna G U Sawa
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - James J Zhou
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Piyanat Wangsawatwong
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Jennifer N Lehrman
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Jakub Godzik
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Alton J Oldham
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Jay D Turner
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Brian P Kelly
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Juan S Uribe
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
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Sawa AGU, Wangsawatwong P, Lehrman JN, Hostetler T, de Andrada Pereira B, Godzik J, Hlubek RJ, Uribe JS, Turner JD, Kelly BP. Rod Attachment Induces Significant Strain in Lumbosacral Fixation. Clin Spine Surg 2023; 36:E247-E251. [PMID: 36788442 DOI: 10.1097/bsd.0000000000001438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 12/01/2022] [Indexed: 02/16/2023]
Abstract
STUDY DESIGN This was a laboratory investigation. OBJECTIVE Rod attachment can induce significant pedicle screw-and-rod pre- strain that may predispose the instrumentation to failure. This study investigated how in vitro L5-S1 rod strain and S1 screw strain during rod-screw attachment (pre-strain) compared with strains recorded during pure-moment bending ( test- strain). SUMMARY OF BACKGROUND DATA The lumbosacral junction is highly vulnerable to construct failure due to rod fatigue fracture, sacral screw pull-out, and screw fatigue fracture. MATERIALS AND METHODS Twelve cadaveric specimens were instrumented with L2-ilium pedicle screws and rod. Strain gauges on contoured rods and sacral screws recorded strains during sequential rod-to-screw tightening (pre-strains). The same instrumented constructs were immediately tested in a 6-degree-of-freedom apparatus under continuous loading to 7.5 Nm in multidirectional bending while recording instrumentation test-strains. Rod and screw pre-strains and test-strains were compared using 1-way repeated-measures analysis of variance followed by Holm-Šidák paired analysis (significant at P <0.05). RESULTS The mean first (171±192 µE) and second (322±269 µE) rod attachment pre-strains were comparable to mean test-strains during flexion (265±109 µE) and extension (315±125 µE, P ≥0.13). The mean rod attachment pre-strain was significantly greater than mean test-strains during bidirectional lateral bending (40±32 µE ipsilateral and 39±32 µE contralateral, P <0.001) and axial rotation (72±60 µE ipsilateral and 60±57 µE contralateral, P <0.001). The mean first and second sacral screw pre-strains during rod attachment (1.03±0.66 and 1.39±1.00 Nm, respectively) did not differ significantly ( P =0.41); however, the mean sacral screw pre-strain during final (second) rod attachment was significantly greater than screw test-strains during all directions of movement (≤0.81 Nm, P ≤0.03). CONCLUSIONS Instrumentation pre-strains imposed during in vitro rod-screw attachment of seemingly well-contoured rods in L2-ilium fixation are comparable to, and at times greater than, strains experienced during in vitro bending. Spine surgeons should be aware of the biomechanical consequences of rod contouring and attachment on construct vulnerability.
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Affiliation(s)
- Anna G U Sawa
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ
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Wangsawatwong P, de Andrada Pereira B, Lehrman JN, Sawa AGU, O'Neill LK, Turner JD, Uribe JS, Kelly BP. Biomechanical Effects of Facet Joint Violation after Single-level Lumbar Fusion with Transpedicular Screw and Rod Instrumentation. Spine (Phila Pa 1976) 2023:00007632-990000000-00336. [PMID: 37141463 DOI: 10.1097/brs.0000000000004698] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 04/08/2023] [Indexed: 05/06/2023]
Abstract
STUDY DESIGN In vitro biomechanical study. OBJECTIVE This study aimed to investigate the biomechanical effects of facet joint violation (FV) on mobility and optically tracked intervertebral disc (IVD) surface strains at the upper level adjacent to L4-5 pedicle screw-rod fixation. SUMMARY OF BACKGROUND DATA FV is a complication that can occur when placing lumbar pedicle screws; the reported incidence is as high as 50%. However, little is known about how FV affects superior adjacent-level spinal stability, and especially IVD strain, after lumbar fusion. METHODS Fourteen cadaveric L3-S1 specimens underwent L4-5 pedicle-rod fixation, 7 in the facet joint preservation (FP) group and 7 in the FV group. Specimens were tested multidirectionally under pure moment loading (7.5 Nm). Colored maps of maximum (ε1) and minimum (ε2) principal surface strain changes on the lateral L3-4 disc were generated with the surface divided into 4 quarters anterior to posterior (Q1, Q2, Q3, and Q4, respectively) for subregional analyses. Range of motion (ROM) and IVD strain were normalized to intact upper adjacent-level and compared between the groups using analysis of variance. Statistical significance was set at P <0.05. RESULTS Normalized ROM was significantly greater with FV versus FP in flexion (11% greater; P =0.04), right lateral bending (16% greater; P =0.03), and right axial rotation (23% greater; P =0.04). Normalized L3-4 IVD ε1 during right lateral bending was greater on average for the FV group than the FP group: Q1, 18% greater; Q2, 12% greater; Q3, 40% greater ( P <0.001); Q4, 9% greater. Normalized ε2 values during left axial rotation were greater in the FV group, the highest increase being 25% in Q3 ( P =0.02). CONCLUSIONS Facet joint violation during single-level pedicle screw-rod fixation was associated with increased superior adjacent level mobility and alteration of disc surface strains, with significant increases in selected regions and directions of loading.
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Affiliation(s)
- Piyanat Wangsawatwong
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
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Koffie RM, de Andrada Pereira B, Lehrman JN, Godzik J, Sawa AGU, Gandhi SV, Kelly BP, Uribe JS, Turner JD. Influence of Spinal Deformity Construct Design on Adjacent-Segment Biomechanics. World Neurosurg 2022; 166:e656-e663. [PMID: 35872128 DOI: 10.1016/j.wneu.2022.07.076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 07/14/2022] [Accepted: 07/15/2022] [Indexed: 12/15/2022]
Abstract
BACKGROUND Adjacent level degeneration is a precursor to construct failure in adult spinal deformity surgery, but whether construct design affects adjacent level degeneration risk remains unclear. Here we present a biomechanical profile of common deformity correction constructs and assess adjacent level biomechanics. METHODS Standard nondestructive flexibility tests (7.5 Nm) were performed on 21 cadaveric specimens: 14 pedicle subtraction osteotomies (PSOs) and 7 anterior column realignment (ACR) constructs. The ranges of motion (ROM) at the adjacent free level in flexion, extension, axial rotation, and lateral bending were measured and analyzed. RESULTS ACR constructs had a lower ROM change on flexion at the proximal adjacent free level than constructs with PSO (1.02 vs. 1.32, normalized to the intact specimen, P < 0.01). Lateral lumbar interbody fusion adjacent to PSO and 4 rods limits ROM at the free level more effectively than transforaminal interbody fusion and 2 rods in correction constructs with PSO. Use of 2 screws to anchor the ACR interbody further decreased ROM at the proximal adjacent free level on flexion, but adding 4 rods in this setting added no further limitation to adjacent segment motion. CONCLUSIONS ACR constructs have less ROM change at the adjacent level compared to PSO constructs. Among constructs with ACR, anchoring the ACR interbody with 2 screws reduces motion at the proximal adjacent free level. When PSOs are used, lateral lumbar interbody fusion adjacent to the PSO level has a greater reduction in adjacent-segment motion than transforaminal interbody fusion, suggesting that deformity construct configuration influences proximal adjacent-segment biomechanics.
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Affiliation(s)
- Robert M Koffie
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Bernardo de Andrada Pereira
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Jennifer N Lehrman
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Jakub Godzik
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Anna G U Sawa
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Shashank V Gandhi
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Brian P Kelly
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Juan S Uribe
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Jay D Turner
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
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Pereira BDA, Lehrman JN, Sawa AG, Wangsawatwong P, Godzik J, Xu DS, Turner JD, Kelly BP, Uribe JS. Biomechanical Effects of Proximal Polyetheretherketone Rod Extension on the Upper Instrumented and Adjacent Levels in a Human Long-Segment Construct: A Cadaveric Model. Neurospine 2022; 19:828-837. [PMID: 36203305 PMCID: PMC9537850 DOI: 10.14245/ns.2244146.073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 06/12/2022] [Indexed: 12/14/2022] Open
Abstract
OBJECTIVE The high mechanical stress zone at the sudden transition from a rigid to flexible region is involved in proximal junctional kyphosis (PJK) physiopathology. We evaluated the biomechanical performance of polyetheretherketone (PEEK) rods used as a nontraditional long semirigid transition phase from a long-segment metallic rod construct to the nonfused thoracic spine. METHODS Pure moment range of motion (ROM) tests (7.5 Nm) were performed on 7 cadaveric spine segments followed by compression (200 N). Specimens were tested in the following conditions: (1) intact; (2) T10-pelvis pedicle screws and rods (PSRs); and (3) extending the proximal construct to T6 using PEEK rods (PSR+PEEK). T10-11 rod strain, T9 anterolateral bone strain, and T10 screw bending moments were analyzed. RESULTS At the upper instrumented vertebra (UIV)+1, PSR+PEEK versus PSR significantly decreased ROM in flexion (115%, p = 0.02), extension (104%, p = 0.003), left lateral bending (46%, p = 0.02), and right lateral bending (63%, p = 0.008). Also, at UIV+1, PSR+PEEK versus intact significantly decreased ROM in flexion (111%, p = 0.01) and extension (105%, p = 0.003). The UIV+1 anterior column bone strain was significantly reduced with PSR+PEEK versus PSR during right lateral bending (p = 0.02). Rod strain polarities reversed with PEEK rods in all loading directions except compression. CONCLUSION Extending a long-segment construct using PEEK rods caused a decrease in adjacent-level hypermobility as a consequence of long-segment immobilization and also redistributed the strain on the UIV and adjacent levels, which might contribute to PJK physiopathology. Further studies are necessary to observe the clinical outcomes of this technique.
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Affiliation(s)
- Bernardo de Andrada Pereira
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Jennifer N. Lehrman
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Anna G.U. Sawa
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Piyanat Wangsawatwong
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Jakub Godzik
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - David S. Xu
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Jay D. Turner
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Brian P. Kelly
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA,Corresponding Author Brian P. Kelly c/o Neuroscience Publications; Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center 350 W. Thomas Rd.; Phoenix, AZ 85013, USA
| | - Juan S. Uribe
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
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de Andrada Pereira B, Wangsawatwong P, Lehrman JN, Sawa AGU, Farber SH, Godzik J, O'Neill LK, Uribe JS, Kelly BP, Turner JD. Subtle segmental angle changes of single-level lumbar fusions and adjacent-level biomechanics: cadaveric study of optically measured disc strain. J Neurosurg Spine 2022; 37:1-10. [PMID: 35535834 DOI: 10.3171/2022.3.spine211221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 03/08/2022] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Changes to segmental lordosis at a single level may affect adjacent-level biomechanics and overall spinal alignment with an iatrogenic domino effect commonly seen in adult spinal deformity. This study investigated the effects of different segmental angles of single-level lumbar fixation on stability and principal strain across the surface of the adjacent-level disc. METHODS Seven human cadaveric L3-S1 specimens were instrumented at L4-5 and tested in 3 conditions: 1) neutral native angle ("neutral"), 2) increasing angle by 5° of lordosis ("lordosis"), and 3) decreasing angle by 5° of kyphosis ("kyphosis"). Pure moment loads (7.5 Nm) were applied in flexion, extension, lateral bending, and axial rotation, followed by 400 N of axial compression alone and together with pure moments. Range of motion (ROM), principal maximum strain (E1), and principal minimum strain (E2) across different surface subregions of the upper adjacent-level disc (L3-4) were optically assessed. Larger magnitudes of either E1 or E2 indicate larger tissue deformations and represent indirect measures of increased stress. RESULTS At the superior adjacent level, a significant increase in ROM was observed in kyphosis and lordosis versus neutral in flexion (p ≤ 0.001) and extension (p ≤ 0.02). ROM was increased in lordosis versus neutral (p = 0.03) and kyphosis (p = 0.004) during compression. ROM increased in kyphosis versus neutral and lordosis (both p = 0.03) in compression plus extension. Lordosis resulted in increased E1 across the midposterior subregion of the disc (Q3) versus neutral during right lateral bending (p = 0.04); lordosis and kyphosis resulted in decreased E1 in Q3 versus neutral with compression (p ≤ 0.03). Lordosis decreased E1 in Q3 versus neutral during compression plus flexion (p = 0.01), whereas kyphosis increased E1 in all quartiles and increased E2 in the midanterior subregion versus lordosis in compression plus flexion (p ≤ 0.047). Kyphosis decreased E1 in Q3 (p = 0.02) and E2 in the anterior-most subregion of the disc (Q1) (p = 0.006) versus neutral, whereas lordosis decreased E1 in Q3 (p = 0.008) versus neutral in compression plus extension. CONCLUSIONS Lumbar spine monosegmental fixation with 5° offset from the neutral individual segmental angle altered the motion and principal strain magnitudes at the upper adjacent disc, with induced kyphosis resulting in larger principal strains compared with lordosis. Segmental alignment of single-level fusion influences adjacent-segment biomechanics, and suboptimal alignment may play a role in the clinical development of adjacent-segment disease.
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Affiliation(s)
- Bernardo de Andrada Pereira
- 1Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix; and
| | - Piyanat Wangsawatwong
- 1Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix; and
| | - Jennifer N Lehrman
- 1Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix; and
| | - Anna G U Sawa
- 1Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix; and
| | - S Harrison Farber
- 2Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Jakub Godzik
- 2Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Luke K O'Neill
- 1Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix; and
| | - Juan S Uribe
- 2Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Brian P Kelly
- 1Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix; and
| | - Jay D Turner
- 2Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
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Kelly BP, Silva CR, Lehrman JN, Sawa AGU, de Andrada Pereira B, Godzik J, Turner JD. Use of digital imaging correlation techniques for full-field strain distribution analysis of implantable devices and tissue in spinal biomechanics research. J Biomech 2022; 135:111025. [PMID: 35259657 DOI: 10.1016/j.jbiomech.2022.111025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 02/03/2022] [Accepted: 02/24/2022] [Indexed: 11/19/2022]
Abstract
Few studies have used optical full-field surface strain mapping to study spinal biomechanics. We used a commercial digital imaging correlation (DIC) system to (1) compare posterior surface strains on spinal rods with those obtained from conventional foil strain gauges, (2) quantify bony vertebral body and intervertebral disc (IVD) surface strains on 3 L3-S cadaveric spines during gold-standard flexibility tests (7.5-Nm flexion-extension and 400-N compression), and (3) report our experience with the application and feasibility of DIC to comprehensively map strain in spinal biomechanics. Spinal rods were tested under zero load and using ASTM F1717 standard. For rod strain measures, the largest mean bias offset and baseline noise standard deviation under zero load for DIC were 7.6 με and 33.7 με, respectively. For tissue measures, the largest mean bias offset was 8 με for ε1 and -55 με for ε2 with baseline noise standard deviations of 19 με and 26 με, respectively. On average, DIC rod strain measurements were 5.3% less than strain gauge measurements throughout the load range. Principal IVD and bony surface strains were consistently measurable and showed marked regional differences in strain patterns under different load conditions. Strains measured on spinal rods using DIC techniques reasonably agreed with standard strain gauge measurements. Subregional strain analyses on soft and hard spinal tissues during standard flexibility tests were feasible. Optical strain mapping is a viable, accurate, and promising measurement technique for novel spinal biomechanical studies.
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Affiliation(s)
- Brian P Kelly
- Spinal Biomechanics Laboratory, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States.
| | - Casey R Silva
- Spinal Biomechanics Laboratory, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States
| | - Jennifer N Lehrman
- Spinal Biomechanics Laboratory, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States
| | - Anna G U Sawa
- Spinal Biomechanics Laboratory, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States
| | - Bernardo de Andrada Pereira
- Spinal Biomechanics Laboratory, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States
| | - Jakub Godzik
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States
| | - Jay D Turner
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States
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de Andrada Pereira B, Sawa AGU, Godzik J, Lehrman JN, Uribe JS, Turner JD, Kelly BP. Influence of Lumbar Lordosis on Posterior Rod Strain in Long-Segment Construct During Biomechanical Loading: A Cadaveric Study. Neurospine 2021; 18:635-643. [PMID: 34610695 PMCID: PMC8497261 DOI: 10.14245/ns.2142368.184] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 08/03/2021] [Indexed: 12/02/2022] Open
Abstract
Objective The lordotic shape of the lumbar spine differs substantially between individuals. Measuring and recording strain during spinal biomechanical tests is an effective method to infer stresses on spinal implants and predict failure mechanisms. The geometry of the spine may have a significant effect on the resultant force distribution, thereby directly affecting rod strain.
Methods Seven fresh-frozen cadaveric specimens (T12-sacrum) underwent standard (7.5 Nm) nondestructive sagittal plane tests: flexion and extension. The conditions tested were intact and pedicle screws and rods (PSR) at L1-sacrum. The posterior right rod was instrumented with strain gauges between L3–4 (index level) and the L5–S1 pedicle screw. All specimens underwent lateral radiographs before testing. Lordotic angles encompassing different levels (L5–S1, L4–S1, L3–S1, L2–S1, and L1–S1) were measured and compared with rod strain. Data were analyzed using Pearson correlation analyses.
Results Strong positive correlations were observed between lordosis and posterior rod strain across different conditions. The L3–S1 lordotic angle in the unloaded intact condition correlated with peak rod strain at L3–4 with PSR during flexion (R=0.76, p=0.04). The same angle in the unloaded PSR condition correlated with peak strain in the PSR condition during extension (R=-0.79, p=0.04). The unloaded intact L2–S1 lordotic angle was significantly correlated with rod strain at L3–4 in the PSR condition during flexion (R=0.85, p=0.02) and extension (R=-0.85, p=0.02) and with rod strain at L5–S1 in the PSR condition during flexion (R=0.84, p=0.04).
Conclusion Lordosis measured on intact and instrumented conditions has strong positive correlations with posterior rod strain in cadaveric testing.
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Affiliation(s)
- Bernardo de Andrada Pereira
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Anna G U Sawa
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Jakub Godzik
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Jennifer N Lehrman
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Juan S Uribe
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Jay D Turner
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Brian P Kelly
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
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de Andrada Pereira B, Wangsawatwong P, Lehrman JN, Sawa AGU, Lindsey DP, Yerby SA, Godzik J, Waguespack AM, Uribe JS, Kelly BP. Biomechanics of a laterally placed sacroiliac joint fusion device supplemental to S2 alar-iliac fixation in a long-segment adult spinal deformity construct: a cadaveric study of stability and strain distribution. J Neurosurg Spine 2021; 36:42-52. [PMID: 34534964 DOI: 10.3171/2021.3.spine202175] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 03/01/2021] [Indexed: 11/06/2022]
Abstract
OBJECTIVE S2 alar-iliac (S2AI) screw fixation effectively enhances stability in long-segment constructs. Although S2AI fixation provides a single transarticular sacroiliac joint fixation (SIJF) point, additional fixation points may provide greater stability and attenuate screw and rod strain. The objectives of this study were to evaluate changes in stability and pedicle screw and rod strain with extended distal S2AI fixation and with supplemental bilateral integration of two sacroiliac joint fusion devices implanted using a traditional minimally invasive surgical approach. METHODS Eight L1-pelvis human cadaveric specimens underwent pure moment (7.5 Nm) and compression (400 N) tests under 4 conditions: 1) intact (pure moment loading only); 2) L2-S1 pedicle screw and rod with L5-S1 interbody fusion; 3) added S2AI screws; and 4) added bilateral laterally placed SIJF. Range of motion (ROM), rod strain, and screw-bending moment (S1 and S2AI) were analyzed. RESULTS Compared with S1 fixation, S2AI fixation significantly reduced L5-S1 ROM in right lateral bending by 50% (0.11°, p = 0.049) and in compression by 39% (0.22°, p = 0.003). Compared with fixation ending at S1, extending fixation with S2AI significantly decreased sacroiliac joint ROM by 52% (0.28°, p = 0.02) in flexion, by 65% (0.48°, p = 0.04) in extension, by 59% (0.76°, p = 0.02) in combined flexion-extension, and by 36% (0.09°, p = 0.02) in left axial rotation. The addition of S2AI screws reduced S1 screw-bending moment during flexion (0.106 Nm [43%], p = 0.046). With S2AI fixation, posterior L5-S1 primary rod strain increased by 124% (159 μE, p = 0.002) in flexion, by 149% (285 μE, p = 0.02) in left axial rotation, and by 99% (254 μE, p = 0.04) in right axial rotation. Compared with S2AI fixation, the addition of SIJF reduced L5-S1 strain during right axial rotation by 6% (28 μE, p = 0.04) and increased L5-S1 strain in extension by 6% (28 μE, p = 0.02). CONCLUSIONS Long-segment constructs ending with S2AI screws created a more stable construct than those ending with S1 screws, reducing lumbosacral and sacroiliac joint motion and S1 screw-bending moment in flexion. These benefits, however, were paired with increased rod strain at the lumbosacral junction. The addition of SIJF to constructs ending at S2AI did not significantly change SI joint ROM or S1 screw bending and reduced S2AI screw bending in compression. SIJF further decreased L5-S1 rod strain in axial rotation and increased it in extension.
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Affiliation(s)
- Bernardo de Andrada Pereira
- 1Spinal Biomechanics Laboratory, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Piyanat Wangsawatwong
- 1Spinal Biomechanics Laboratory, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Jennifer N Lehrman
- 1Spinal Biomechanics Laboratory, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Anna G U Sawa
- 1Spinal Biomechanics Laboratory, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | | | | | - Jakub Godzik
- 3Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona; and
| | | | - Juan S Uribe
- 3Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona; and
| | - Brian P Kelly
- 1Spinal Biomechanics Laboratory, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
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Lehrman JN, Mulholland CB, de Andrada Pereira B, Sawa AGU, Kelly BP, Tumialán LM. Dimensional Characterization of the Human Lumbar Interlaminar Space as a Guide for Safe Application of Minimally Invasive Dilators. Oper Neurosurg (Hagerstown) 2021; 21:E89-E94. [PMID: 33582809 DOI: 10.1093/ons/opab011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 12/08/2020] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND The risk of interlaminar passage of a dilator into the lumbar spinal canal in minimally invasive approaches is currently unknown. Among anthropometric data reported in the medical literature, there is no cadaveric report of the interlaminar dimensions of the lumbar spine. OBJECTIVE To report the lumbar interlaminar dimensions in neutral, flexion, and extension postures. METHODS A total of 8 spines were sectioned into lumbar segments. Digitized coordinate data defining the locations and movements of chosen anatomic points on the laminar edges at a given spinal level were used to measure changes in the opening dimensions during static neutral posture and flexion-extension movements. Interlaminar dimensions were averaged and categorized for each vertebral level and spinal posture. RESULTS The mean interlaminar distance increased from neutral posture to flexion across all vertebral levels. The mean interlaminar distances in the neutral posture ranged from 12.21 mm (L5-S1) to 14.88 mm (L1-L2). In flexion, the range was from 17.15 mm (L5-S1) to 18.50 mm (L4-L5). These measurements are greater than the first several diameters of dilators in all minimally invasive dilator sets. CONCLUSION The precise measurements of the lumbar interlaminar space are valuable to minimally invasive spine surgeons for the dilatation phase of the operation. The risk of interlaminar passage of a minimally invasive dilator is greatest in flexion with dilators that have a diameter of 16 mm or less. There is considerably less risk of interlaminar passage in patients positioned on an extended Jackson table.
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Affiliation(s)
- Jennifer N Lehrman
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Celene B Mulholland
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Bernardo de Andrada Pereira
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Anna G U Sawa
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Brian P Kelly
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Luis M Tumialán
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
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Godzik J, de Andrada Pereira B, Sawa AGU, Lehrman JN, Mundis GM, Hlubek RJ, Uribe JS, Kelly BP, Turner JD. Biomechanics of open versus minimally invasive deformity correction: comparison of stability and rod strain between pedicle subtraction osteotomy and anterior column realignment. J Neurosurg Spine 2021:1-9. [PMID: 34214986 DOI: 10.3171/2020.12.spine201306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 12/07/2020] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Anterior column realignment (ACR) is a new minimally invasive approach for deformity correction that achieves a degree of lordosis similar to that obtained with pedicle subtraction osteotomy (PSO). This study compared the biomechanical profiles of ACR with PSO using range of motion (ROM) and posterior rod strain (RS) to gain insight into the ACR technique and the necessary surgical strategies to optimize longevity and stability. METHODS An in vitro biomechanical study using standard flexibility testing (7.5 Nm) was performed on 14 human cadaveric specimens, separated into 2 groups similar in age, sex, bone mineral density, and intact ROM. For group 1 (n = 7, instrumented L1-S1), a 30° ACR was performed at L3-4. For group 2 (n = 7, instrumented T12-S1), a 30° L3 PSO was performed. Specimens were subjected to nondestructive loads in flexion, extension, axial rotation, lateral bending, and compression. Conditions tested were 1) intact, 2) pedicle screw with 2 rods (PSR), 3) ACR or PSO with 2 rods (+2R), and 4) ACR or PSO with 4 rods (+4R). Primary outcome measures of interest were ROM stability and posterior RS at L3-4. RESULTS No difference was observed between groups in lumbar lordosis (p = 0.83) or focal angular lordosis at L3-4 (p = 0.75). No differences in stability were observed between ACR+2R and PSO+2R (p ≥ 0.06); however, ACR+2R was significantly less stable than PSR in flexion and extension (p ≤ 0.02), whereas PSO+2R was less stable than PSR only in extension (p = 0.04). ACR+4R was more stable than ACR+2R in flexion, extension, left axial rotation, and compression (p ≤ 0.02). PSO+4R was more stable than PSO+2R only in extension (p = 0.04). Both ACR+2R and PSO+2R resulted in significant increases in RS in flexion and extension compared with PSR (p ≤ 0.032). RS in flexion and extension decreased significantly for ACR+4R versus ACR+2R and for PSO+4R versus PSO+2R (p ≤ 0.047). PSO+2R yielded lower RS than ACR+2R in compression (p = 0.03). No differences existed in RS between ACR+4R and PSO+4R (p ≥ 0.05). CONCLUSIONS Although ACR appeared to be slightly more destabilizing than PSO using traditional 2R fixation, both techniques resulted in significant increases in posterior RS. The 4R technique increased stability in ACR and decreased RS in both ACR and PSO but may be more beneficial in ACR. Longer-term clinical studies are needed to appropriately identify the durability of the ACR technique in deformity correction.
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Affiliation(s)
| | - Bernardo de Andrada Pereira
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona; and
| | - Anna G U Sawa
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona; and
| | - Jennifer N Lehrman
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona; and
| | - Gregory M Mundis
- 3San Diego Spine Foundation, Scripps Clinic Division of Orthopedic Surgery, La Jolla, California
| | | | | | - Brian P Kelly
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona; and
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Wangsawatwong P, Sawa AGU, de Andrada Pereira B, Lehrman JN, O'Neill LK, Turner JD, Uribe JS, Kelly BP. Adjacent-segment effects of lumbar cortical screw-rod fixation versus pedicle screw-rod fixation with and without interbody support. J Neurosurg Spine 2021:1-7. [PMID: 34144524 DOI: 10.3171/2020.11.spine20977] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 11/09/2020] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Cortical screw-rod (CSR) fixation has emerged as an alternative to the traditional pedicle screw-rod (PSR) fixation for posterior lumbar fixation. Previous studies have concluded that CSR provides the same stability in cadaveric specimens as PSR and is comparable in clinical outcomes. However, recent clinical studies reported a lower incidence of radiographic and symptomatic adjacent-segment degeneration with CSR. No biomechanical study to date has focused on how the adjacent-segment mobility of these two constructs compares. This study aimed to investigate adjacent-segment mobility of CSR and PSR fixation, with and without interbody support (lateral lumbar interbody fusion [LLIF] or transforaminal lumbar interbody fusion [TLIF]). METHODS A retroactive analysis was done using normalized range of motion (ROM) data at levels adjacent to single-level (L3-4) bilateral screw-rod fixation using pedicle or cortical screws, with and without LLIF or TLIF. Intact and instrumented specimens (n = 28, all L2-5) were tested using pure moment loads (7.5 Nm) in flexion, extension, lateral bending, and axial rotation. Adjacent-segment ROM data were normalized to intact ROM data. Statistical comparisons of adjacent-segment normalized ROM between two of the groups (PSR followed by PSR+TLIF [n = 7] and CSR followed by CSR+TLIF [n = 7]) were performed using 2-way ANOVA with replication. Statistical comparisons among four of the groups (PSR+TLIF [n = 7], PSR+LLIF [n = 7], CSR+TLIF [n = 7], and CSR+LLIF [n = 7]) were made using 2-way ANOVA without replication. Statistical significance was set at p < 0.05. RESULTS Proximal adjacent-segment normalized ROM was significantly larger with PSR than CSR during flexion-extension regardless of TLIF (p = 0.02), or with either TLIF or LLIF (p = 0.04). During lateral bending with TLIF, the distal adjacent-segment normalized ROM was significantly larger with PSR than CSR (p < 0.001). Moreover, regardless of the types of screw-rod fixations (CSR or PSR), TLIF had a significantly larger normalized ROM than LLIF in all directions at both proximal and distal adjacent segments (p ≤ 0.04). CONCLUSIONS The use of PSR versus CSR during single-level lumbar fusion can significantly affect mobility at the adjacent segment, regardless of the presence of TLIF or with either TLIF or LLIF. Moreover, the type of interbody support also had a significant effect on adjacent-segment mobility.
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de Andrada Pereira B, Lehrman JN, Sawa AGU, Lindsey DP, Yerby SA, Godzik J, Waguespack AM, Uribe JS, Kelly BP. Biomechanical effects of a novel posteriorly placed sacroiliac joint fusion device integrated with traditional lumbopelvic long-construct instrumentation. J Neurosurg Spine 2021:1-10. [PMID: 34144523 DOI: 10.3171/2020.11.spine201540] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 11/24/2020] [Indexed: 11/06/2022]
Abstract
OBJECTIVE S2-alar-iliac (S2AI) screw fixation effectively ensures stability and enhances fusion in long-segment constructs. Nevertheless, pelvic fixation is associated with a high rate of mechanical failure. Because of the transarticular nature of the S2AI screw, adding a second point of fixation may provide additional stability and attenuate strains. The objective of the study was to evaluate changes in stability and strain with the integration of a sacroiliac (SI) joint fusion device, implanted through a novel posterior SI approach, supplemental to posterior long-segment fusion. METHODS L1-pelvis human cadaveric specimens underwent pure moment (7.5 Nm) and compression (400 N) tests in the following conditions: 1) intact, 2) L2-S1 pedicle screw and rod fixation with L5-S1 interbody fusion, 3) added S2AI screws, and 4) added bilateral SI joint fixation (SIJF). The range of motion (ROM), rod strain, and screw bending moments (S1 and S2AI) were analyzed. RESULTS S2AI fixation decreased L2-S1 ROM in flexion-extension (p ≤ 0.04), L5-S1 ROM in flexion-extension and compression (p ≤ 0.004), and SI joint ROM during flexion-extension and lateral bending (p ≤ 0.03) compared with S1 fixation. SI joint ROM was significantly less with SIJF in place than with the intact joint, S1, and S2AI fixation in flexion-extension and lateral bending (p ≤ 0.01). The S1 screw bending moment decreased following S2AI fixation by as much as 78% in extension, but with statistical significance only in right axial rotation (p = 0.03). Extending fixation to S2AI significantly increased the rod strain at L5-S1 during flexion, axial rotation, and compression (p ≤ 0.048). SIJF was associated with a slight increase in rod strain versus S2AI fixation alone at L5-S1 during left lateral bending (p = 0.048). Compared with the S1 condition, fixation to S2AI increased the mean rod strain at L5-S1 during compression (p = 0.048). The rod strain at L5-S1 was not statistically different with SIJF compared with S2AI fixation (p ≥ 0.12). CONCLUSIONS Constructs ending with an S2AI screw versus an S1 screw tended to be more stable, with reduced SI joint motion. S2AI fixation decreased the S1 screw bending moments compared with fixation ending at S1. These benefits were paired with increased rod strain at L5-S1. Supplementation of S2AI fixation with SIJF implants provided further reductions (approximately 30%) in the sagittal plane and lateral bending SI joint motion compared with fixation ending at the S2AI position. This stability was not paired with significant changes in rod or screw strains.
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Affiliation(s)
| | | | - Anna G U Sawa
- 1Department of Neurosurgery, Spinal Biomechanics Laboratory, and
| | | | | | - Jakub Godzik
- 3Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | | | - Juan S Uribe
- 3Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Brian P Kelly
- 1Department of Neurosurgery, Spinal Biomechanics Laboratory, and
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Pereira BDA, Heller JE, Lehrman JN, Sawa AGU, Kelly BP. Biomechanics of Circumferential Cervical Fixation Using Posterior Facet Cages: A Cadaveric Study. Neurospine 2021; 18:188-196. [PMID: 33819945 PMCID: PMC8021845 DOI: 10.14245/ns.2040552.276] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 10/28/2020] [Indexed: 12/27/2022] Open
Abstract
OBJECTIVE Anterior cervical discectomy and fusion (ACDF) is a common procedure for the treatment of cervical disease. Circumferential procedures are options for multilevel pathology. Potential complications of multilevel anterior procedures are dysphagia and pseudarthrosis, whereas potential complications of posterior surgery include development of cervical kyphosis and postoperative chronic neck pain. The addition of posterior cervical cages (PCCs) to multilevel ACDF is a minimally invasive option to perform circumferential fusion. This study evaluated the biomechanical performance of 3-level circumferential fusion with PCCs as supplemental fixation to anteriorly placed allografts, with and without anterior plate fixation. METHODS Nondestructive flexibility tests (1.5 Nm) performed on 6 cervical C2-7 cadaveric specimens intact and after discectomy (C3-6) in 3 instrumented conditions: allograft with anterior plate (G+P), PCC with allograft and plate (PCC+G+P), and PCC with allograft alone (PCC+G). Range of motion (ROM) data were analyzed using 1-way repeated-measures analysis of variance. RESULTS All instrumented conditions resulted in significantly reduced ROM at the 3 instrumented levels (C3-6) compared to intact spinal segments in flexion, extension, lateral bending, and axial rotation (p < 0.001). No significant difference in ROM was found between G+P and PCC+G+P conditions or between G+P and PCC+G conditions, indicating similar stability between these conditions in all directions of motion. CONCLUSION All instrumented conditions resulted in considerable reduction in ROM. The added reduction in ROM through the addition of PCCs did not reach statistical significance. Circumferential fusion with anterior allograft, without plate and with PCCs, has comparable stability to ACDF with allograft and plate.
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Affiliation(s)
- Bernardo de Andrada Pereira
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | | | - Jennifer N Lehrman
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Anna G U Sawa
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Brian P Kelly
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
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Godzik J, de Andrada Pereira B, Sawa AGU, Lehrman JN, Hlubek RJ, Kelly BP, Turner JD. Impact of dual-headed pedicle screws on the biomechanics of lumbosacral junction multirod constructs. J Neurosurg Spine 2021:1-9. [PMID: 33545680 DOI: 10.3171/2020.8.spine191545] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Accepted: 08/03/2020] [Indexed: 11/06/2022]
Abstract
OBJECTIVE The objective of this study was to evaluate a novel connector design and compare it with traditional side connectors, such as a fixed-angle connector (FAC) and a variable-angle connector (VAC), with respect to lumbosacral stability and instrumentation strain. METHODS Standard nondestructive flexibility tests (7.5 Nm) and compression tests (400 N) were performed using 7 human cadaveric specimens (L1-ilium) to compare range of motion (ROM) stability, posterior rod strain (RS), and sacral screw bending moment (SM). Directions of motion included flexion, extension, left and right lateral bending, left and right axial rotation, and compression. Conditions included 1) the standard 2-rod construct (2R); 2) the dual-tulip head (DTH) with 4-rod construct (4R); 3) FACs with 4R; and 4) VACs with 4R. Data were analyzed using repeated-measures ANOVA. RESULTS Overall, there were no statistically significant differences in ROM across the lumbosacral junction among conditions (p > 0.07). Compared with 2R, DTH and FAC significantly reduced RS in extension, left axial rotation, and compression (p ≤ 0.03). VAC significantly decreased RS compared with 2R in flexion, extension, left axial rotation, right axial rotation, and compression (p ≤ 0.03), and significantly decreased RS compared with DTH in extension (p = 0.02). DTH was associated with increased SM in left and right axial rotation compared with 2R (p ≤ 0.003) and in left and right lateral bending and left and right axial rotation compared with FAC and VAC (p ≤ 0.02). FAC and VAC were associated with decreased SM compared with 2R in right and left lateral bending (p ≤ 0.03). CONCLUSIONS RS across the lumbosacral junction can be high. Supplemental rod fixation with DTH is an effective strategy for reducing RS across the lumbosacral junction. However, the greatest reduction in RS and SM was achieved with a VAC that allowed for straight (uncontoured) accessory rod placement.
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Affiliation(s)
| | - Bernardo de Andrada Pereira
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Anna G U Sawa
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Jennifer N Lehrman
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | | | - Brian P Kelly
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
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Bohl MA, McBryan S, Newcomb AGUS, Lehrman JN, Kelly BP, Nakaji P, Chang SW, Uribe JS, Turner JD, Kakarla UK. Range of Motion Testing of a Novel 3D-Printed Synthetic Spine Model. Global Spine J 2020; 10:419-424. [PMID: 32435561 PMCID: PMC7222693 DOI: 10.1177/2192568219858981] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
STUDY DESIGN Biomechanical model study. OBJECTIVE The Barrow Biomimetic Spine (BBS) project is a resident-driven effort to manufacture a synthetic spine model with high biomechanical fidelity to human tissue. The purpose of this study was to investigate the performance of the current generation of BBS models on biomechanical testing of range of motion (ROM) and axial compression and to compare the performance of these models to historical cadaveric data acquired using the same testing protocol. METHODS Six synthetic spine models comprising L3-5 segments were manufactured with variable soft-tissue densities and print orientations. Models underwent torque loading to a maximum of 7.5 N m. Torques were applied to the models in flexion-extension, lateral bending, axial rotation, and axial compression. Results were compared with historic cadaveric control data. RESULTS Each model demonstrated steadily decreasing ROM on flexion-extension testing with increasing density of the intervertebral discs and surrounding ligamentous structures. Vertically printed models demonstrated markedly less ROM than equivalent models printed horizontally at both L3-4 (5.0° vs 14.0°) and L4-5 (3.9° vs 15.2°). Models D and E demonstrated ROM values that bracketed the cadaveric controls at equivalent torque loads (7.5 N m). CONCLUSIONS This study identified relevant variables that affect synthetic spine model ROM and compressibility, confirmed that the models perform predictably with changes in these print variables, and identified a set of model parameters that result in a synthetic model with overall ROM that approximates that of a cadaveric model. Future studies can be undertaken to refine model performance and determine intermodel variability.
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Affiliation(s)
- Michael A. Bohl
- Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Sarah McBryan
- Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Anna G. U. S. Newcomb
- Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Jennifer N. Lehrman
- Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Brian P. Kelly
- Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Peter Nakaji
- Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Steve W. Chang
- Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Juan S. Uribe
- Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - Jay D. Turner
- Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
| | - U. Kumar Kakarla
- Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA,U. Kumar Kakarla, c/o Neuroscience Publications, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, 350 W Thomas Road, Phoenix, AZ 85013, USA.
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Sawa AGU, Lehrman JN, Crawford NR, Kelly BP. Variations Among Human Lumbar Spine Segments and Their Relationships to In Vitro Biomechanics: A Retrospective Analysis of 281 Motion Segments From 85 Cadaveric Spines. Int J Spine Surg 2020; 14:140-150. [PMID: 32355618 DOI: 10.14444/7021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Background Biomechanical properties of intact spinal motion segments are used to establish baseline values during in vitro studies evaluating spinal surgical techniques and implants. These properties are also used to validate computational models (ie, patient-specific finite element models) of human lumbar spine segments. Our laboratory has performed a large number of in vitro mechanical studies of lumbar spinal segments, using a consistent methodology. This provides extensive biomechanical data for a large number of intact motion segments, along with donor demographic variables, bone mineral density (BMD) measurements, and geometric properties. The objective of this study was to analyze how donor demographics, BMD, and geometric properties of cadaveric lumbar spine segments affect motion segment flexibility, including the range of motion (ROM), lax zone (LZ), and stiff zone (SZ), to help improve our understanding of spinal biomechanics. Methods A retrospective study examined the relationships between the biomechanical properties of 281 lumbar motion segments from 85 human cadaveric spines, donor demographic variables (age, sex, weight, height, and body mass index), and specimen measurements (vertebral body height, intervertebral disc height, and BMD). Results Statistical correlation and regression analyses showed that the flexibility of a lumbar motion segment is affected by lumbar level, donor age, sex, and weight as well as the intervertebral disc height, vertebral body height, and bone quality. Increased disc height was associated with decreased ROM (axial rotation), decreased LZ (flexion-extension and axial rotation), and increased SZ (flexion-extension and lateral bending) in the male group, but increased ROM (lateral bending) in the female group. Increased vertebral body height correlated with increased LZ (lateral bending) in the female group. Increased BMD correlated with decreased ROM overall. Conclusions Biomechanical measurements from flexibility testing of cadaveric lumbar spine segments are significantly correlated with donor demographics and specimen measurements. Many of these correlations are sex-dependent.
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Affiliation(s)
- Anna G U Sawa
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Jennifer N Lehrman
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | | | - Brian P Kelly
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
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Tumialán LM, Lehrman JN, Mulholland CB, de Andrada Pereira B, Newcomb AGUS, Kelly BP. Dimensional Characterization of the Human Cervical Interlaminar Space as a Guide for Safe Application of Minimally Invasive Dilators. Oper Neurosurg (Hagerstown) 2020; 19:E275-E282. [DOI: 10.1093/ons/opaa013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 12/15/2019] [Indexed: 11/13/2022] Open
Abstract
Abstract
BACKGROUND
The risk of interlaminar passage of a dilator into the cervical spinal canal in minimally invasive approaches is currently unknown. Among the various anthropometric data reported in the literature, there is no report of the interlaminar dimensions in the cervical spine.
OBJECTIVE
To report the cervical interlaminar dimensions in neutral, flexion, and extension.
METHODS
A total of 8 spines were sectioned into cervical (C2-T1) segments. Digitized coordinate data defining the locations and movements of chosen anatomic points on the laminar edges at a given spinal level were used to compute the dimensions during a static neutral posture, flexion, and extension positions to mimic the positions during surgery. Interlaminar dimensions were averaged and categorized for each vertebral level and spinal posture.
RESULTS
Based on the reported measurements, the smallest diameter dilator in commonly used dilator sets has the potential to traverse the interlaminar space at all levels in flexion. In a neutral posture, the average interlaminar distance at C2-3, C6-7, and C7-T1 was still greater than 2.0 mm, the smallest diameter of the initial dilator. The largest interlaminar distance was at C6-7 in flexion (7.68 ± 1.60 mm).
CONCLUSION
Because dilators pass directly onto the cervical lamina without visualization of the midline structures, the interlaminar distances have increased relevance in the minimally invasive cervical approaches of foraminotomy and laminectomy. The data in this report demonstrate the theoretical risk of interlaminar passage with small diameter dilators in posterior minimally invasive approaches to the cervical spine.
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Affiliation(s)
- Luis M Tumialán
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Jennifer N Lehrman
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Celene B Mulholland
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Bernardo de Andrada Pereira
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Anna G U S Newcomb
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Brian P Kelly
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
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Godzik J, Pereira BDA, Newcomb AGUS, Lehrman JN, Mundis GM, Hlubek RJ, Uribe JS, Kelly BP, Turner JD. Optimizing biomechanics of anterior column realignment for minimally invasive deformity correction. Spine J 2020; 20:465-474. [PMID: 31518683 DOI: 10.1016/j.spinee.2019.09.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 09/04/2019] [Accepted: 09/05/2019] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Anterior column realignment (ACR) is a powerful but destabilizing minimally invasive technique for sagittal deformity correction. Optimal biomechanical design of the ACR construct is unknown. PURPOSE Evaluate the effect of ACR design on radiographic lordosis, range of motion (ROM) stability, and rod strain (RS) in a cadaveric model. STUDY DESIGN/SETTING Cadaveric biomechanical study. PATIENT SAMPLE Seven fresh-frozen lumbar spine cadaveric specimens (T12-sacrum) underwent ACR at L3-L4 with a 30° implant. OUTCOME MEASURES Primary outcome measure of interest was maximum segmental lordosis measured using lateral radiograph. Secondary outcomes were ROM stability and posterior RS at L3/4. METHODS Effect of grade 1 and grade 2 osteotomies with single-screw anterolateral fixation (1XLP) or 2-screw anterolateral fixation (2XLP) on lordosis was determined radiographically. Nondestructive flexibility tests were used to assess ROM and RS at L3-L4 in flexion, extension, lateral bending, and axial rotation. Conditions included (1) intact, (2) pedicle screw fixation and 2 rods (2R), (3) ACR+1XLP with 2R, (4) ACR+2XLP+2R, (5) ACR+1XLP with 4 rods (4R) (+4R), and (6) ACR+2XLP+4R. RESULTS Segmental lordosis was similar between ACR+1XLP and ACR+2XLP (p>.28). ACR+1XLP+2R was significantly less stable than all other conditions in flexion, extension, and axial rotation (p<.014); however, adding an extra screw improved stability to levels equal to 4R conditions (p>.36). Adding 4R to ACR+1XLP reduced RS in all directions of loading (p<.048), whereas adding a second screw did not (p>.12). There was no difference in strain between ACR+1XLP+4R and ACR+2XLP+4R (p>.55). CONCLUSIONS For maximum stability, ACR constructs should contain either fixation into both vertebral bodies (2XLP) or accessory rods (4R). 2XLP can be used without compromising the maximal achievable lordosis but does not provide the same RS reduction as 4R. CLINICAL SIGNIFICANCE ACR is a highly destabilizing technique that is increasingly being used for minimally invasive deformity correction. These biomechanical data will help clinicians optimize ACR construct design.
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Affiliation(s)
- Jakub Godzik
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350 W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Bernardo de Andrada Pereira
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350 W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Anna G U S Newcomb
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350 W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Jennifer N Lehrman
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350 W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Gregory M Mundis
- Division of Orthopedic Surgery, San Diego Spine Foundation, Scripps Clinic, La Jolla, CA, USA
| | - Randall J Hlubek
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350 W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Juan S Uribe
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350 W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Brian P Kelly
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350 W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Jay D Turner
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350 W. Thomas Rd., Phoenix, AZ 85013, USA.
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Lehrman JN, Narayanan M, Cavallo C, Newcomb AGUS, Zhao X, Kelly BP, Crawford NR, Nakaji P. Evaluation of abnormal styloid anatomy as a cause of internal jugular vein compression using a 3D-printed model: a laboratory investigation. J Clin Neurosci 2019; 72:386-391. [PMID: 31883814 DOI: 10.1016/j.jocn.2019.11.048] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 11/30/2019] [Indexed: 11/27/2022]
Abstract
This study used a 3-dimensional (3D) craniocervical junction model of styloidogenic jugular venous compression (SJVC) syndrome to simulate and evaluate intracranial pressure (ICP) after internal jugular vein (IJV) compression by an elongated styloid process during axial rotation. The 3D-printed model created using data from an SJVC-syndrome patient included an articulating occipital-cervical junction, simplified arteriovenous system, gauge to measure simulated ICP, fixed obstruction simulating left-sided venous occlusion, and right-sided vascular tubing to simulate IJV compression. The model was rotated axially to its extreme right and left; maximum degree of motion and pressure were recorded for 3 cycles. Measurements were repeated after styloid resection in 25% increments. The extreme right rotation (11°) of the intact styloid condition yielded a mean pressure of 15.34 ± 2.85 mmHg. After 25% styloid resection, extreme rotation (11°) yielded 13.96 ± 2.88 mmHg. After 50%, extreme rotation increased to 16° yielding 17.41 ± 3.52 mmHg; 11° rotation was 2.76 ± 1.96 mmHg. After 75%, extreme rotation increased to 19° yielding -0.86 ± 1.08 mmHg; 16° and 11° rotation yielded -0.69 ± 1.19 and -0.86 ± 1.08 mmHg, respectively. After 100%, extreme rotation to 19° yielded -1.21 ± 0.60 mmHg; 16° and 11° rotation yielded -0.34 ± 0.30 and 0.00 ± 0.00 mmHg, respectively. Extreme left rotations (11°) yielded mean pressures of -0.17 ± 0.00 (intact), -0.17 ± 0.30 (25%), 2.24 ± 0.79 (50%), 0.34 ± 0.30 (75%), and 0.17 ± 0.30 mmHg (100%). Simulated ICP increased proportionally to maximum ipsilateral axial rotation, and was highest after 50% styloid resection. Contralateral axial rotation did not increase pressure. IJV compression was relieved at 75% resection, suggesting that partial (75%) or complete styloidectomy is a potentially efficacious treatment for SJVC syndrome.
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Affiliation(s)
- Jennifer N Lehrman
- Spinal Biomechanics Laboratory, Department of Neurosurgery Research, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States
| | - Mohan Narayanan
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States
| | - Claudio Cavallo
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States
| | - Anna G U S Newcomb
- Spinal Biomechanics Laboratory, Department of Neurosurgery Research, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States
| | - Xiaochun Zhao
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States
| | - Brian P Kelly
- Spinal Biomechanics Laboratory, Department of Neurosurgery Research, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States
| | | | - Peter Nakaji
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, United States.
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Snyder LA, Lehrman JN, Menon RK, Godzik J, Newcomb AGUS, Kelly BP. Biomechanical implications of unilateral facetectomy, unilateral facetectomy plus partial contralateral facetectomy, and complete bilateral facetectomy in minimally invasive transforaminal interbody fusion. J Neurosurg Spine 2019; 31:447-452. [PMID: 31075766 DOI: 10.3171/2019.2.spine18942] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 02/13/2019] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Minimally invasive transforaminal interbody fusion techniques vary among surgeons. One decision point is whether to perform a unilateral facetectomy (UF), a unilateral facetectomy plus partial contralateral facetectomy (UF/PF), or a complete bilateral facetectomy (CBF). The authors therefore compared the biomechanical benefits of all 3 types of facetectomies to determine which approach produces improved biomechanical outcomes. METHODS Seven human cadaveric specimens (L3-S1) were potted and prepped for UF, with full facet removal, hemilaminectomy, discectomy, and pedicle screw placement. After distraction, a fixed interbody spacer was placed, and compression was performed. A final fixation configuration was performed by locking the rods across the screws posteriorly with bilateral compression. Final lordosis angle and change and foraminal height were measured, and standard nondestructive flexibility tests were performed to assess intervertebral range of motion (ROM) and compressive stiffness. The same procedure was followed for UF/PF and CBF in all 7 specimens. RESULTS All 3 conditions demonstrated similar ROM and compressive stiffness. No statistically significant differences occurred with distraction, but CBF demonstrated significantly greater change than UF in mean foraminal height after bilateral posterior compression (1.90 ± 0.62 vs 1.00 ± 0.45 mm, respectively, p = 0.04). With compression, the CBF demonstrated significantly greater mean ROM than the UF (2.82° ± 0.83° vs 2.170° ± 1.10°, p = 0.007). The final lordosis angle was greatest with CBF (3.74° ± 0.70°) and lowest with UF (2.68° ± 1.28°). This finding was statistically significant across all 3 conditions (p ≤ 0.04). CONCLUSIONS Although UF/PF and CBF may require slightly more time and effort and incur more risk than UF, the potential improvement in sagittal balance may be worthwhile for select patients.
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Affiliation(s)
| | - Jennifer N Lehrman
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Ram Kumar Menon
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | | | - Anna G U S Newcomb
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Brian P Kelly
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
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Hlubek RJ, Godzik J, Newcomb AGUS, Lehrman JN, de Andrada B, Bohl MA, Farber SH, Kelly BP, Turner JD. Iliac screws may not be necessary in long-segment constructs with L5-S1 anterior lumbar interbody fusion: cadaveric study of stability and instrumentation strain. Spine J 2019; 19:942-950. [PMID: 30419290 DOI: 10.1016/j.spinee.2018.11.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 11/05/2018] [Accepted: 11/05/2018] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Lumbosacral pseudoarthrosis and instrumentation failure is common with long-segment constructs. Optimizing lumbosacral construct biomechanics may help to reduce failure rates. The influence of iliac screws and interbody type on range of motion (ROM), rod strain (RS), sacral screw strain (SS) is not well-established. PURPOSE Investigate the effects of transforaminal lumbar interbody fusion (TLIF), anterior lumbar interbody fusion (ALIF), and iliac screws on long-segment lumbosacral construct biomechanics. STUDY DESIGN Biomechanical study. PATIENT SAMPLE Fourteen human cadaveric spine specimens. OUTCOME MEASURES Lumbosacral ROM, RS, and SS. METHODS Specimens were potted at L1 and the ilium. Specimens were equally divided into either an L5-S1 ALIF or TLIF group and underwent testing in the following conditions: (1) intact (2) L2-S1 pedicle screw rod fixation (PSR-S) (3) L2-ilium (PSR-I) (4) PSR-S+ALIF (ALIF-S) or TLIF (TLIF-S) (5) PSR-I + ALIF (ALIF-I) or TLIF (TLIF-I). Pure moment bending (7.5 Nm) in flexion, extension, lateral bending, axial rotation, and compressive loads (400N) were applied and ROM, SS, and RS were measured. Comparisons were performed using a one-way ANOVA (p<.05). RESULTS ALIF-S and TLIF-S provided similar decreases in ROM as TLIF-I (p>.05). Compared to PSR-S, PSR-I significantly decreased SS during bending in all directions (p<.02) but increased RS in flexion and extension (p≤.02). Anterior lumbar interbody fusion-S provided similar decreases in SS as TLIF-I in all directions (p>.40) but had significantly less RS than TLIF-I in flexion, extension, compression (p<.01). TLIF-S had more SS than TLIF-I in flexion, extension, axial rotation (p<.02), while TLIF-S had less RS only in flexion (p=.03). Compared to PSR-I, ALIF-I decreased the RS (p<.02) but TLIF-I did not (p>.67). CONCLUSIONS Iliac screws were protective of SS but increased RS at the lumbosacral junction. Constructs with ALIF and no iliac screws result in comparable SS as constructs with TLIF and iliac screws with significantly reduced RS. If iliac screws are utilized, ALIF but not TLIF reduces the iliac screw-induced RS. CLINICAL SIGNIFICANCE There is a relatively high incidence of lumbosacral instrumentation failure in adult spinal deformity. Optimizing lumbosacral construct biomechanics may help to reduce failure rates. Iliac screws induce lumbosacral rod strain and may be responsible for instrumentation failure. Constructs with lumbosacral ALIF reduce iliac-screw induced rod strain and may obviate the need for fixation to the ilium.
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Affiliation(s)
- Randall J Hlubek
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Jakub Godzik
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Anna G U S Newcomb
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Jennifer N Lehrman
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Bernardo de Andrada
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Michael A Bohl
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Samuel H Farber
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Brian P Kelly
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350W. Thomas Rd., Phoenix, AZ 85013, USA
| | - Jay D Turner
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, 350W. Thomas Rd., Phoenix, AZ 85013, USA.
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Godzik J, Lehrman JN, Newcomb AGUS, Menon RK, Whiting AC, Kelly BP, Snyder LA. Tailoring selection of transforaminal interbody spacers based on biomechanical characteristics and surgical goals: evaluation of an expandable spacer. J Neurosurg Spine 2019; 32:1-7. [PMID: 30978679 DOI: 10.3171/2019.1.spine181008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 01/18/2019] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Transforaminal lumbar interbody fusion (TLIF) is commonly used for lumbar fusion, such as for foraminal decompression, stabilization, and improving segmental lordosis. Although many options exist, surgical success is contingent on matching design strengths with surgical goals. The goal in the present study was to investigate the effects of an expandable interbody spacer and 2 traditional static spacer designs in terms of stability, compressive stiffness, foraminal height, and segmental lordosis. METHODS Standard nondestructive flexibility tests (7.5 N⋅m) were performed on 8 cadaveric lumbar specimens (L3-S1) to assess intervertebral stability of 3 types of TLIF spacers at L4-5 with bilateral posterior screw-rod (PSR) fixation. Stability was determined as range of motion (ROM) in flexion-extension (FE), lateral bending (LB), and axial rotation (AR). Compressive stiffness was determined with axial compressive loading (300 N). Foraminal height, disc height, and segmental lordosis were evaluated using radiographic analysis after controlled PSR compression (170 N). Four conditions were tested in random order: 1) intact, 2) expandable interbody cage with PSR fixation (EC+PSR), 3) static ovoid cage with PSR fixation (SOC+PSR), and 4) static rectangular cage with PSR fixation (SRC+PSR). RESULTS All constructs demonstrated greater stability than the intact condition (p < 0.001). No significant differences existed among constructs in ROM (FE, AR, and LB) or compressive stiffness (p ≥ 0.66). The EC+PSR demonstrated significantly greater foraminal height at L4-5 than SRC+PSR (21.1 ± 2.6 mm vs 18.6 ± 1.7 mm, p = 0.009). EC+PSR demonstrated higher anterior disc height than SOC+PSR (14.9 ± 1.9 mm vs 13.6 ± 2.2 mm, p = 0.04) and higher posterior disc height than the intact condition (9.4 ± 1.5 mm vs 7.1 ± 1.0 mm, p = 0.002), SOC+PSR (6.5 ± 1.8 mm, p < 0.001), and SRC+PSR (7.2 ± 1.2 mm, p < 0.001). There were no significant differences in segmental lordosis among SOC+PSR (10.1° ± 2.2°), EC+PSR (8.1° ± 0.5°), and SRC+PSR (11.1° ± 3.0°) (p ≥ 0.06). CONCLUSIONS An expandable interbody spacer provided stability, stiffness, and segmental lordosis comparable to those of traditional nonexpandable spacers of different shapes, with increased foraminal height and greater disc height. These results may help inform decisions about which interbody implants will best achieve surgical goals.
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Affiliation(s)
| | - Jennifer N Lehrman
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Anna G U S Newcomb
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Ram Kumar Menon
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | | | - Brian P Kelly
- 2Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
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Bohl MA, Morgan CD, Mooney MA, Repp GJ, Lehrman JN, Kelly BP, Chang SW, Turner JD, Kakarla UK. Biomechanical Testing of a 3D-printed L5 Vertebral Body Model. Cureus 2019; 11:e3893. [PMID: 30911450 PMCID: PMC6424546 DOI: 10.7759/cureus.3893] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Background We examined the biomechanical performance of a three-dimensional (3D)-printed vertebra on pedicle screw insertional torque (IT), axial pullout (APO), and stiffness (ST) testing. Materials and methods Seventy-three anatomically identical L5 vertebral body models (146 pedicles) were printed and tested for IT, APO, and ST using single-threaded pedicle screws of equivalent diameter (6.5 mm), length (40.0 mm), and thread pitch (2.6 mm). Print properties (material, cortical thickness [number of shells], cancellous density [in-fill], in-fill pattern, print orientation) varied among models. One-way analysis of variance was performed to evaluate the effects of variables on outcomes. Results The type of material significantly affected IT, APO, and ST (P < 0.001, all comparisons). For acrylonitrile butadiene styrene (ABS) models, in-fill density (25-35%) had a positive linear association with APO (P = 0.002), ST (P = 0.008), and IT (P = 0.10); similarly for the polylactic acid (PLA) models, APO (P = 0.001), IT (P < 0.001), and ST (P = 0.14). For the nylon material type, in-fill density did not affect any tested parameter. For a given in-fill density, material, and print orientation, the in-fill pattern significantly affected IT (P = 0.002) and APO (P = 0.03) but not ST (P = 0.23). Print orientation also significantly affected IT (P < 0.001), APO (P < 0.001), and ST (P = 0.002). Conclusions 3D-printed vertebral body models with specific print parameters can be designed to perform analogously to human bone on pedicle screw tests of IT, APO, and ST. Altering the material, in-fill density, in-fill pattern, and print orientation of synthetic vertebral body models could reliably produce a model that mimics bone of a specific bone mineral density.
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Affiliation(s)
- Michael A Bohl
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Clinton D Morgan
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Michael A Mooney
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Garrett J Repp
- Department of Neurology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Jennifer N Lehrman
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Brian P Kelly
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Steve W Chang
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - Jay D Turner
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
| | - U Kumar Kakarla
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, USA
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Cross WW, Berven SH, Slater N, Lehrman JN, Newcomb AGUS, Kelly BP. In Vitro Biomechanical Evaluation of a Novel, Minimally Invasive, Sacroiliac Joint Fixation Device. Int J Spine Surg 2018; 12:587-594. [PMID: 30364882 DOI: 10.14444/5072] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Background Sacroiliac (SI) joint pathology may result in low-back pain, which causes substantial disability. Treatment failure with operative management of SI pain may be related to incomplete fusion of the joint and to fixation failure. The objective of this study was to evaluate the initial biomechanical stability of SI joint fixation with a novel implantable device in an in vitro human cadaveric model. Methods The right and left sides of 3 cadaveric L4-pelvis specimens were tested (1) intact, (2) destabilized, and (3) instrumented with an implantable SI joint fixation device using a simulated single-stance load condition. Right-leg and left-leg stance data were grouped together for a sample size of 6, and angular range of motion (ROM) was determined during application of flexion-extension, lateral bending, and axial rotation bending moments to a limit of 7.5 Nm. Results Following intact testing, destabilization by severing the posterior SI joint capsule and ligaments and the pubic symphysis reliably produced a significantly destabilized joint with the mean angular ROM more than doubling in flexion-extension and lateral bending and more than tripling in axial rotation (P ≤ .003) compared to the intact condition. Instrumentation with the SI screw fixation device significantly reduced mean joint ROM compared to the destabilized condition in all 3 anatomic planes tested (P < .001). When compared to the intact condition, the SI-instrumented condition significantly reduced lateral bending (P = .01) and had a similar ROM in flexion-extension (P = .14) and axial rotation (P = .85). Conclusions Instrumentation with the SI screw fixation device significantly reduced mean joint ROM compared to the destabilized condition, with similar ROM in flexion-extension and axial rotation, and it significantly reduced ROM in lateral bending compared to that for the intact joint. The ROM values observed with the instrumented condition were comparable to levels of mobility considered favorable for spinal fusion.
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Affiliation(s)
- William W Cross
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota
| | - Sigurd H Berven
- Department of Orthopedic Surgery, University of California at San Francisco, San Francisco, California
| | | | - Jennifer N Lehrman
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Anna G U S Newcomb
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
| | - Brian P Kelly
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona
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Dou N, Lehrman JN, Newcomb AGUS, Kelly BP. In Reply to the Letter to the Editor "C2 Spinous Process Screws". World Neurosurg 2018; 116:477. [PMID: 30049031 DOI: 10.1016/j.wneu.2018.05.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 05/02/2018] [Indexed: 11/28/2022]
Affiliation(s)
- NingNing Dou
- Department of Neurosurgery Research, Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Jennifer N Lehrman
- Department of Neurosurgery Research, Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Anna G U S Newcomb
- Department of Neurosurgery Research, Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Brian P Kelly
- Department of Neurosurgery Research, Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
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Dou N, Lehrman JN, Newcomb AGUS, Kelly BP. A Novel C2 Screw Trajectory: Preliminary Anatomic Feasibility and Biomechanical Comparison. World Neurosurg 2018; 113:e93-e100. [PMID: 29408275 DOI: 10.1016/j.wneu.2018.01.177] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 01/22/2018] [Accepted: 01/23/2018] [Indexed: 11/25/2022]
Abstract
BACKGROUND Pedicle screw and translaminar screw fixation in C2 may not be applicable in many patients with anatomic abnormalities or narrow laminar thickness and spinous process height. The aim of this study was to assess morphometric and mechanical feasibilities of a novel alternative screw trajectory that pierces the bifid base of C2. METHODS Anatomic measurements that determined the feasibility of spinous process bifid base (SPB) screw fixation were assessed in 14 cadaveric C2 vertebrae. Pullout tests to assess ultimate fixation strength for 3 screw trajectories (transpedicular, translaminar, and SPB) were performed in cadaveric vertebrae for comparison. RESULTS Anatomic measurements included mean spinous process height (10.4 ± 4.2 mm) and mean bilateral bifid base length (10.1 ± 2.2 mm) and thickness (left, 4.4 ± 1.0 mm; right, 4.3 ± 0.9 mm). In 64% (9/14) of specimens, bifid base length was ≥9 mm. Mean pullout strength for transpedicle, translaminar, and SPB screws in 9 viable specimens was 648 ± 305 N, 628 ± 417 N, and 755 ± 279 N. CONCLUSIONS SPB screw fixation may be viable anatomically and mechanically for C2 fixation. Feasibility of SPB screw fixation is determined by length, thickness, and mutual angle of the bilateral bifid bases. Patients with thin (<4 mm) and short (<9 mm) bifid bases are not likely to be suitable candidates. SPB screw fixation shows potential as an alternative approach or a salvage technique for patients with high-riding vertebral arteries or severely thin C2 lamina and warrants further investigation.
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Affiliation(s)
- NingNing Dou
- Department of Neurosurgery, XinHua Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China
| | - Jennifer N Lehrman
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Anna G U S Newcomb
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Brian P Kelly
- Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
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Giers MB, Munter BT, Eyster KJ, Ide GD, Newcomb AG, Lehrman JN, Belykh E, Byvaltsev VA, Kelly BP, Preul MC, Theodore N. Biomechanical and Endplate Effects on Nutrient Transport in the Intervertebral Disc. World Neurosurg 2017; 99:395-402. [DOI: 10.1016/j.wneu.2016.12.041] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 12/09/2016] [Accepted: 12/10/2016] [Indexed: 01/18/2023]
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