Craniovertebral junction fixation with transarticular screws: biomechanical analysis of a novel technique

2003 ◽  
Vol 98 (2) ◽  
pp. 202-209 ◽  
Author(s):  
L. Fernando Gonzalez ◽  
Neil R. Crawford ◽  
Robert H. Chamberlain ◽  
Luis E. Perez Garza ◽  
Mark C. Preul ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Axial Rotation ◽  
Craniovertebral Junction ◽  
Biomechanical Analysis ◽  
Lateral Bending ◽  
Content Type ◽  
Additional Stability ◽  
A New Technique ◽  
Flexion And Extension ◽  
Fine Print

Object. The authors compared the biomechanical stability resulting from the use of a new technique for occipitoatlantal motion segment fixation with an established method and assessed the additional stability provided by combining the two techniques. Methods. Specimens were loaded using nonconstraining pure moments while recording the three-dimensional angular movement at occiput (Oc)—C1 and C1–2. Specimens were tested intact and after destabilization and fixation as follows: 1) Oc—C1 transarticular screws plus C1–2 transarticular screws; 2) occipitocervical transarticular (OCTA) plate in which C1–2 transarticular screws attach to a loop from Oc to C-2; and (3) OCTA plate plus Oc—C1 transarticular screws. Occipitoatlantal transarticular screws reduced motion to well within the normal range. The OCTA loop and transarticular screws allowed a very small neutral zone, elastic zone, and range of motion during lateral bending and axial rotation. The transarticular screws, however, were less effective than the OCTA loop in resisting flexion and extension. Conclusions. Biomechanically, Oc—C1 transarticular screws performed well enough to be considered as an alternative for Oc—C1 fixation, especially when instability at C1–2 is minimal. Techniques for augmenting these screws posteriorly by using a wired bone graft buttress, as is currently undertaken with C1–2 transarticular screws, may be needed for optimal performance.

Stability of the craniovertebral junction after unilateral occipital condyle resection: a biomechanical study

1999 ◽  
Vol 90 (1) ◽  
pp. 91-98 ◽  
Author(s):  
A. Giancarlo Vishteh ◽  
Neil R. Crawford ◽  
M. Stephen Melton ◽  
Robert F. Spetzler ◽  
Volker K. H. Sonntag ◽  
...  
Keyword(s):  
Axial Rotation ◽  
Craniovertebral Junction ◽  
Biomechanical Study ◽  
Occipital Condyle ◽  
Upper Cervical Spine ◽  
Lateral Bending ◽  
Content Type ◽  
Axial Translation ◽  
Flexion Extension ◽  
Fine Print

Object. The authors sought to determine the biomechanics of the occipitoatlantal (occiput [Oc]—C1) and atlantoaxial (C1–2) motion segments after unilateral gradient condylectomy. Methods. Six human cadaveric specimens (skull with attached upper cervical spine) underwent nondestructive biomechanical testing (physiological loads) during flexion—extension, lateral bending, and axial rotation. Axial translation from tension to compression was also studied across Oc—C2. Each specimen served as its own control and underwent baseline testing in the intact state. The specimens were then tested after progressive unilateral condylectomy (25% resection until completion), which was performed using frameless stereotactic guidance. At Oc—C1 for all motions that were tested, mobility increased significantly compared to baseline after a 50% condylectomy. Flexion—extension, lateral bending, and axial rotation increased 15.3%, 40.8%, and 28.1%, respectively. At C1–2, hypermobility during flexion—extension occurred after a 25% condylectomy, during axial rotation after 75% condylectomy, and during lateral bending after a 100% condylectomy. Conclusions. Resection of 50% or more of the occipital condyle produces statistically significant hypermobility at Oc—C1. After a 75% resection, the biomechanics of the Oc—C1 and C1–2 motion segments change considerably. Performing fusion of the craniovertebral junction should therefore be considered if half or more of one occipital condyle is resected.

scholarly journals Biomechanical Analysis of Allograft Spacer Failure as a Function of Cortical-Cancellous Ratio in Anterior Cervical Discectomy/Fusion: Allograft Spacer Alone Model

2020 ◽  
Vol 10 (18) ◽  
pp. 6413
Author(s):  
Ji-Won Kwon ◽  
Hwan-Mo Lee ◽  
Tae-Hyun Park ◽  
Sung Jae Lee ◽  
Young-Woo Kwon ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Element Model ◽  
Axial Rotation ◽  
Biomechanical Analysis ◽  
Flexion Extension ◽  
Hybrid Motion ◽  
Anterior Cervical Discectomy Fusion ◽  
Flexion And Extension ◽  
Additional Fixation ◽  
Lateral Walls

The design and ratio of the cortico-cancellous composition of allograft spacers are associated with graft-related problems, including subsidence and allograft spacer failure. Methods: The study analyzed stress distribution and risk of subsidence according to three types (cortical only, cortical cancellous, cortical lateral walls with a cancellous center bone) and three lengths (11, 12, 14 mm) of allograft spacers under the condition of hybrid motion control, including flexion, extension, axial rotation, and lateral bending,. A detailed finite element model of a previously validated, three-dimensional, intact C3–7 segment, with C5–6 segmental fusion using allograft spacers without fixation, was used in the present study. Findings: Among the three types of cervical allograft spacers evaluated, cortical lateral walls with a cancellous center bone exhibited the highest stress on the cortical bone of spacers, as well as the endplate around the posterior margin of the spacers. The likelihood of allograft spacer failure was highest for 14 mm spacers composed of cortical lateral walls with a cancellous center bone upon flexion (PVMS, 270.0 MPa; 250.2%) and extension (PVMS: 371.40 MPa, 344.2%). The likelihood of allograft spacer subsidence was also highest for the same spacers upon flexion (PVMS, 4.58 MPa; 28.1%) and extension (PVMS: 12.71 MPa, 78.0%). Conclusion: Cervical spacers with a smaller cortical component and of longer length can be risk factors for allograft spacer failure and subsidence, especially in flexion and extension. However, further study of additional fixation methods, such as anterior plates/screws and posterior screws, in an actual clinical setting is necessary.

Stabilizing effect of posterior lumbar interbody fusion cages before and after cyclic loading

2000 ◽  
Vol 92 (1) ◽  
pp. 87-92 ◽  
Author(s):  
Annette Kettler ◽  
Hans-Joachim Wilke ◽  
Rupert Dietl ◽  
Matthias Krammer ◽  
Christianto Lumenta ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Interbody Fusion ◽  
Posterior Lumbar Interbody Fusion ◽  
Axial Rotation ◽  
Lumbar Interbody Fusion ◽  
Lateral Bending ◽  
Content Type ◽  
Flexion Extension ◽  
Stabilizing Effect ◽  
Fine Print

Object. The function of interbody fusion cages is to stabilize spinal segments primarily by distracting them as well as by allowing bone ingrowth and fusion. An important condition for efficient formation of bone tissue is achieving adequate spinal stability. However, the initial stability may be reduced due to repeated movements of the spine during everyday activity. Therefore, in addition to immediate stability, stability after cyclic loading is of remarkable relevance; however, this has not yet been investigated. The object of this study was to investigate the immediate stabilizing effect of three different posterior lumbar interbody fusion cages and to clarify the effect of cyclic loading on the stabilization. Methods. Before and directly after implantation of a Zientek, Stryker, or Ray posterior lumbar interbody fusion cage, 24 lumbar spine segment specimens were each evaluated in a spine tester. Pure lateral bending, flexion—extension, and axial rotation moments (± 7.5 Nm) were applied continuously. The motion in each specimen was measured simultaneously. The specimens were then loaded cyclically (40,000 cycles, 5 Hz) with an axial compression force ranging from 200 to 1000 N. Finally, they were tested once again in the spine tester. Conclusions. In general, a decrease of movement in all loading directions was noted after insertion of the Zientek and Ray cages and an increase of movement after implantation of a Stryker cage. In all three cage groups greater stability was demonstrated in lateral bending and flexion than in extension and axial rotation. Reduced stability during cyclic loading was observed in all three cage groups; however, loss of stability was most pronounced when the Ray cage was used.

Biomechanical analysis of a newly designed bioabsorbable anterior cervical plate

2005 ◽  
Vol 3 (6) ◽  
pp. 465-470 ◽  
Author(s):  
Christopher P. Ames ◽  
Frank L. Acosta ◽  
Robert H. Chamberlain ◽  
Adolfo Espinoza Larios ◽  
Neil R. Crawford
Keyword(s):  
Axial Rotation ◽  
Metal Plate ◽  
Biomechanical Analysis ◽  
Fibular Graft ◽  
Disc Disease ◽  
Content Type ◽  
Flexion Extension ◽  
Cervical Plate ◽  
Anterior Cervical Plate ◽  
Fine Print

Object. The authors present a biomechanical analysis of a newly designed bioabsorbable anterior cervical plate (ACP) for the treatment of one-level cervical degenerative disc disease. They studied anterior cervical discectomy and fusion (ACDF) in a human cadaveric model, comparing the stability of the cervical spine after placement of the bioabsorbable fusion plate, a bioabsorbable mesh, and a more traditional metallic ACP. Methods. Seven human cadaveric specimens underwent a C6–7 fibular graft—assisted ACDF placement. A one-level resorbable ACP was then placed and secured with bioabsorbable screws. Flexibility testing was performed on both intact and instrumented specimens using a servohydraulic system to create flexion—extension, lateral bending, and axial rotation motions. After data analysis, three parameters were calculated: angular range of motion, lax zone, and stiff zone. The results were compared with those obtained in a previous study of a resorbable fusion mesh and with those acquired using metallic fusion ACPs. For all parameters studied, the resorbable plate consistently conferred greater stability than the resorbable mesh. Moreover, it offered comparable stability with that of metallic fusion ACPs. Conclusions. Bioabsorbable plates provide better stability than resorbable mesh. Although the results of this study do not necessarily indicate that a resorbable plate confers equivalent stability to a metal plate, the resorbable ACP certainly yielded better results than the resorbable mesh. Bioabsorbable fusion ACPs should therefore be considered as alternatives to metal plates when a graft containment device is required.

Biomechanical studies of an artificial disc implant in the human cadaveric spine

2005 ◽  
Vol 2 (3) ◽  
pp. 339-343 ◽  
Author(s):  
Patrick W. Hitchon ◽  
Kurt Eichholz ◽  
Christopher Barry ◽  
Paige Rubenbauer ◽  
Aditya Ingalhalikar ◽  
...  
Keyword(s):  
Biomechanical Testing ◽  
Axial Rotation ◽  
Load Testing ◽  
Artificial Disc ◽  
Lateral Bending ◽  
Content Type ◽  
Intact State ◽  
Flexion Extension ◽  
Fine Print

Object. The authors compared the biomechanical performance of the human cadaveric spine implanted with a metallic ball-and-cup artificial disc at L4–5 with the spine's intact state and after anterior discectomy. Methods. Seven human L2—S1 cadaveric spines were mounted on a biomechanical testing frame. Pure moments of 0, 1.5, 3.0, 4.5, and 6.0 Nm were applied to the spine at L-2 in six degrees of motion (flexion, extension, right and left lateral bending, and right and left axial rotation). The spines were tested in the intact state as well as after anterior L4–5 discectomy. The Maverick disc was implanted in the discectomy defect, and load testing was repeated. The artificial disc created greater rigidity for the spine than was present after discectomy, and the spine performed biomechanically in a manner comparable with the intact state. Conclusions. The results indicate that in an in vitro setting, this model of artificial disc stabilizes the spine after discectomy, restoring motion comparable with that of the intact state.

In vitro biomechanical analysis of three anterior thoracolumbar implants

2000 ◽  
Vol 93 (2) ◽  
pp. 252-258 ◽  
Author(s):  
Patrick W. Hitchon ◽  
Vijay K. Goel ◽  
Thomas N. Rogge ◽  
James C. Torner ◽  
Andrew P. Dooris ◽  
...  
Keyword(s):  
Axial Rotation ◽  
Biomechanical Analysis ◽  
Rigid Fixation ◽  
Angular Rotation ◽  
Content Type ◽  
Light Emitting ◽  
Vertebral Bodies ◽  
The Stability ◽  
Fine Print

Object. The goal of this study was to evaluate the comparative efficacy of three commonly used anterior thoracolumbar implants: the anterior thoracolumbar locking plate (ATLP), the smooth-rod Kaneda (SRK), and the Z-plate. Methods. In vitro testing was performed using the T9—L3 segments of human cadaver spines. An L-1 corpectomy was performed, and stabilization was achieved using one of three anterior devices: the ATLP in nine spines, the SRK in 10, and the Z-plate in 10. Specimens were load tested with 1.5-, 3-, 4.5-, and 6-Nm in flexion and extension, right and left lateral bending, and right and left axial rotation. Angular motion was monitored using two video cameras that tracked light-emitting diodes attached to the vertebral bodies. Testing was performed in the intact state in spines stabilized with one of the three aforementioned devices after the devices had been fatigued to 5000 cycles at ± 3 Nm and after bilateral facetectomy. There was no difference in the stability of the intact spines with use of the three devices. There were no differences between the SRK- and Z-plate—instrumented spines in any state. In extension testing, the mean angular rotation (± standard deviation) of spines instrumented with the SRK (4.7 ± 3.2°) and Z-plate devices (3.3 ± 2.3°) was more rigid than that observed in the ATLP-stabilized spines (9 ± 4.8°). In flexion testing after induction of fatigue, however, only the SRK (4.2 ± 3.2°) was stiffer than the ATLP (8.9 ± 4.9°). Also, in extension postfatigue, only the SRK (2.4 ± 3.4°) provided more rigid fixation than the ATLP (6.4 ± 2.9°). All three devices were equally unstable after bilateral facetectomy. The SRK and Z-plate anterior thoracolumbar implants were both more rigid than the ATLP, and of the former two the SRK was stiffer. Conclusions. The authors' results suggest that in cases in which profile and ease of application are not of paramount importance, the SRK has an advantage over the other two tested implants in achieving rigid fixation immediately postoperatively.

Effects of neck movements on stability and subsidence in cervical interbody fusion: an in vitro study

2001 ◽  
Vol 94 (1) ◽  
pp. 97-107 ◽  
Author(s):  
Annette Kettler ◽  
Hans-Joachim Wilke ◽  
Lutz Claes
Keyword(s):  
Bone Cement ◽  
Interbody Fusion ◽  
In Vitro Study ◽  
Axial Rotation ◽  
Vitro Study ◽  
Implant Design ◽  
Lateral Bending ◽  
Content Type ◽  
Fine Print

Object. The aim of this in vitro study was to determine the influence of simulated postoperative neck movements on the stabilizing effect and subsidence of four different anterior cervical interbody fusion devices. Emphasis was placed on the relation between subsidence and spinal stability. Methods. The flexibility of 24 human cervical spine specimens was tested before and directly after being stabilized with a WING, BAK/C, AcroMed I/F cage, or with bone cement in standard flexibility tests under 50 N axial preload. Thereafter, 700 pure moment loading cycles (± 2 Nm) were applied in randomized directions to simulate physiological neck movements. Additional flexibility tests in combination with measurements of the subsidence depth were conducted after 50, 100, 200, 300, 500, and 700 loading cycles. In all four groups, simulated postoperative neck movements caused an increase of the range of motion (ROM) ranging from 0.4 to 3.1° and of the neutral zone from 0.1 to 4.2°. This increase in flexibility was most distinct in extension followed by flexion, lateral bending, and axial rotation. After cyclic loading, ROM tended to be lower in the group fitted with AcroMed cages (3.3° in right lateral bending, 3.5° in left axial rotation, 7.8° in flexion, 8.3° in extension) and in the group in which bone cement was applied (5.4°, 2.5°, 7.4°, and 8.8°, respectively) than in those fixed with the WING (6.3°, 5.4°, 9.7°, and 6.9°, respectively) and BAK cages (6.2°, 4.5°, 10.2°, and 11.6°, respectively). Conclusions. Simulated repeated neck movements not only caused an increase of the flexibility but also subsidence of the implants into the adjacent vertebrae. The relation between flexibility increase and subsidence seemed to depend on the implant design: subsiding BAK/C cages partially supported stability whereas subsiding WING cages and AcroMed cages did not.

Effect of a prosthetic disc nucleus on the mobility and disc height of the L4–5 intervertebral disc postnucleotomy

2001 ◽  
Vol 95 (2) ◽  
pp. 208-214 ◽  
Author(s):  
Hans-Joachim Wilke ◽  
Sinead Kavanagh ◽  
Sylvia Neller ◽  
Christian Haid ◽  
Lutz Eberhart Claes
Keyword(s):  
Intervertebral Disc ◽  
Axial Rotation ◽  
Disc Height ◽  
In Vitro Test ◽  
Lateral Bending ◽  
Content Type ◽  
Intact State ◽  
Device Implantation ◽  
Flexion Extension ◽  
Fine Print

Object. Current procedures for treatment of degenerative disc disease may not restore flexibility or disc height to the intervertebral disc. Recently, a prosthetic device, intended to replace the degenerated nucleus pulposus, was developed. In this biomechanical in vitro test the authors study the effect of implanting a prosthetic nucleus in cadaveric lumbar intervertebral discs postnucleotomy and determine if the flexibility and disc height of the L4–5 motion segment is restored. Methods. The prosthetic disc nucleus device consists of two hydrogel pellets, each enclosed in a woven polyethylene jacket. Six human cadaveric lumbar motion segments (obtained in individuals who, at the time of death, were a mean age of 56.7 years) were loaded with moments of ± 7.5 Nm in flexion—extension, lateral bending, and axial rotation. The following states were investigated: intact, postnucleotomy, and after device implantation. Range of motion (ROM) and neutral zone (NZ) measurements were determined. Change in disc height from the intact state was measured after nucleotomy and device implantation, with and without a 200-N preload. Conclusions. Compared with the intact state (100%), the nucleotomy increased the ROM in flexion—extension to 118%, lateral bending to 112%, and axial rotation to 121%; once the device was implanted the ROM was reduced to 102%, 88%, and 90%, respectively. The NZ increased the ROM to 210%, lateral bending to 173%, and axial rotation to 107% after nucleotomy, and 146%, 149%, 44%, respectively, after device implantation. A 200-N preload reduced the intact and postnucleotomy disc heights by approximately 1 mm and 2 mm, respectively. The original intact disc height was restored after implantation of the device. The results of the cadaveric L4–5 flexibility testing indicate that the device can potentially restore ROM, NZ, and disc height to the denucleated segment.

Comparison of the biomechanics of hydroxyapatite and polymethylmethacrylate vertebroplasty in a cadaveric spinal compression fracture model

2001 ◽  
Vol 95 (2) ◽  
pp. 215-220 ◽  
Author(s):  
Patrick W. Hitchon ◽  
Vijay Goel ◽  
John Drake ◽  
Derek Taggard ◽  
Matthew Brenton ◽  
...  
Keyword(s):  
Compression Fracture ◽  
Axial Rotation ◽  
Load Testing ◽  
Lateral Bending ◽  
Content Type ◽  
Significant Difference ◽  
Flexion Extension ◽  
Before And After ◽  
Weight Drop ◽  
Fine Print

Object. Polymethylmethacrylate (PMMA) has long been used in the stabilization and reconstruction of traumatic and pathological fractures of the spine. Recently, hydroxyapatite (HA), an osteoconductive, biocompatible cement, has been used as an alternative to PMMA. In this study the authors compare the stabilizing effects of the HA product, BoneSource, with PMMA in an experimental compression fracture of L-1. Methods. Twenty T9—L3 cadaveric spine specimens were mounted individually on a testing frame. Light-emitting diodes were placed on the neural arches as well as the base. Motion was tracked by two video cameras in response to applied loads of 0 to 6 Nm. The weight-drop technique was used to induce a reproducible compression fracture of T-11 after partially coring out the vertebra. Load testing was performed on the intact spine, postfracture, after unilateral transpedicular vertebroplasty with 7 to 10 ml of PMMA or HA, and after flexion—extension fatiguing to 5000 cycles at ± 3 Nm. No significant difference between the HA- and PMMA cemented—fixated spines was demonstrated in flexion, extension, left lateral bending, or right and left axial rotation. The only difference between the two cements was encountered before and after fatiguing in right lateral bending (p ≤ 0.05). Conclusions. The results of this study suggest that the same angular rigidity can be achieved using either HA or PMMA. This is of particular interest because HA is osteoconductive, undergoes remodeling, and is not exothermic.

Biomechanical comparison of facet-sparing laminectomy and Christmas tree laminectomy

2003 ◽  
Vol 99 (2) ◽  
pp. 214-220 ◽  
Author(s):  
Paul W. Detwiler ◽  
Christina B. Spetzler ◽  
Sara B. Taylor ◽  
Neil R. Crawford ◽  
Randall W. Porter ◽  
...  
Keyword(s):  
Axial Rotation ◽  
Shear Loading ◽  
Angular Motion ◽  
Christmas Tree ◽  
Lumbar Stenosis ◽  
Lateral Bending ◽  
Content Type ◽  
Objective Evidence ◽  
Flexion Extension ◽  
Fine Print

Object. The authors compared differences in biomechanical stability between two decompressive laminectomy techniques for treating lumbar stenosis. A Christmas tree laminectomy (CTL), in which bilateral facetectomies and foraminotomies are performed, was compared with facet-sparing laminectomy (FSL), in which the facets are undercut but not resected. Spinal instability was assessed immediately postoperatively and again after discectomy to model long-term degeneration. Methods. Sixteen motion segments obtained from five human cadaveric lumbar specimens were studied in vitro by conducting nondestructive flexibility tests. Specimens were tested intact, after FSL or CTL, and again after discectomy. Nonconstraining torques (≤ 5 Nm) were applied to induce flexion, extension, axial rotation, and lateral bending; strings and pulleys were used while vertebral angles were measured. Anteroposterior translation in response to shear loading (≤ 100 N) was also measured. Angular motion, shear motion, and sagittal-plane axes of rotation were compared to evaluate stability. Compared with the intact condition, CTL-treated specimens had significantly larger increases in angular motion during flexion, lateral bending, and axial rotation than their FSL-treated counterparts (p < 0.05, nonpaired Student t-tests). Subsequent discectomy caused greater increases in motion in the CTL group. Axes of rotation shifted less from their normal positions after FSL than after CTL. Conclusions. This study provides objective evidence that the treatment of lumbar stenosis with FSL induces less biomechanical instability and alters kinematics less than FSL. These findings support the use of the FSL in treating lumbar stenosis.

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