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.

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.

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.

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.

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.

Bioabsorbable anterior lumbar plate fixation in conjunction with cage-assisted anterior interbody fusion

2002 ◽  
Vol 97 (4) ◽  
pp. 447-455 ◽  
Author(s):  
Denis J. DiAngelo ◽  
Jeffrey L. Scifert ◽  
Scott Kitchel ◽  
G. Bryan Cornwall ◽  
Bobby J. McVay
Keyword(s):  
Interbody Fusion ◽  
Plate Fixation ◽  
Axial Rotation ◽  
Biomechanical Study ◽  
Local Motion ◽  
Content Type ◽  
Flexion Extension ◽  
Spine Model ◽  
Fine Print

Object. An in vitro biomechanical study was conducted to determine the effects of anterior stabilization on cage-assisted lumbar interbody fusion biomechanics in a multilevel human cadaveric lumbar spine model. Methods. Three spine conditions were compared: harvested, bilateral multilevel cages (CAGES), and CAGES with bioabsorbable anterior plates (CBAP), tested under flexion—extension, lateral bending, and axial rotation. Measurements included vertebral motion, applied load, and bending/rotational moments. Application of anterior fixation decreased local motion and increased stiffness of the instrumented levels. Clinically, this spinal stability may serve to promote fusion. Conclusions. Coupled with the bioabsorbability of the plating material, the bioabsorbable anterior lumbar plating system is considered biomechanically advantageous.

Immediate Stiffness of the C5–C6 Segment after Discectomy with the Cloward Technique: An in Vitro Biomechanical Study on a Human Cadaveric Model

Neurosurgery ◽  
2001 ◽  
Vol 49 (6) ◽  
pp. 1399-1408 ◽  
Author(s):  
Andrzej Maciejczak ◽  
Michał Ciach ◽  
Maciej Radek ◽  
Andrzej Radek ◽  
Jan Awrejcewicz
Keyword(s):  
Interbody Fusion ◽  
Spinal Instrumentation ◽  
Axial Rotation ◽  
Postoperative Management ◽  
Biomechanical Study ◽  
Lateral Bending ◽  
Cervical Discectomy ◽  
Cloward Procedure ◽  
Flexion Extension

ABSTRACT OBJECTIVE To determine whether the Cloward technique of cervical discectomy and fusion increases immediate postoperative stiffness of single cervical motion segment after application of interbody dowel bone graft. METHODS We measured and compared the stiffness of single-motion segments in cadaveric cervical spines before and immediately after interbody fusion with the Cloward technique. Changes in range of motion and stiffness of the C5–C6 segment were measured in a bending flexibility test (flexion, extension, lateral bending and axial rotation) before and after a Cloward procedure in 11 fresh-frozen human cadaveric specimens from the 4th through the 7th vertebrae. RESULTS The Cloward procedure produced a statistically significant increase in stiffness of the operated segment in flexion and lateral bending when compared with the intact spine. The less stiff the segment before the operation, the greater the increase in its postoperative flexural stiffness (statistically significant). The Cloward procedure produced nonuniform changes in rotational and extensional stiffness that increased in some specimens and decreased in others. CONCLUSION Our data demonstrate that Cloward interbody fusion increases immediate postoperative stiffness of an operated segment only in flexion and lateral bending in cadaveric specimens in an in vitro environment. Thus, Cloward fusion seems a relatively ineffective method for increasing the stiffness of a construct. This may add to discussion on the use of spinal instrumentation and postoperative management of patients after cervical discectomy, which varies from bracing in hard collars through immobilization in soft collars to no external orthosis.

Biomechanical comparison of anterior and posterior stabilization methods in atlantoaxial instability

2004 ◽  
Vol 100 (3) ◽  
pp. 277-283 ◽  
Author(s):  
Sung-Min Kim ◽  
T. Jesse Lim ◽  
Josemaria Paterno ◽  
Tae-Jin Hwang ◽  
Kun-Woo Lee ◽  
...  
Keyword(s):  
The Other ◽  
Atlantoaxial Instability ◽  
Fixation Method ◽  
Posterior Fixation ◽  
Lateral Bending ◽  
Biomechanical Stability ◽  
Transarticular Screw ◽  
Content Type ◽  
Flexion Extension ◽  
Fine Print

Object. The authors compared the biomechanical stability of two anterior fixation procedures—anterior C1–2 Harms plate/screw (AHPS) fixation and the anterior C1–2 transarticular screw (ATS) fixation; and two posterior fixation procedures—the posterior C-1 lateral mass combined with C-2 pedicle screw/rod (PLM/APSR) fixation and the posterior C1–2 transarticular screw (PTS) fixation after destabilization. Methods. Sixteen human cervical spine specimens (Oc—C3) were tested in three-dimensional flexion—extension, axial rotation, and lateral bending motions after destabilization by using an atlantoaxial C1–2 instability model. In each loading mode, moments were applied to a maximum of 1.5 Nm, and the range of motion (ROM), neutral zone (NZ), and elastic zone (EZ) were determined and values compared using the intact spine, the destabilized spine, and the postfixation spine. The AHPS method produced inferior biomechanical results in flexion—extension and lateral bending modes compared with the intact spine. The lateral bending NZ and ROM for this method differed significantly from the other three fixation techniques (p < 0.05), although statistically significant differences were not obtained for all other values of ROM and NZ for the other three procedures. The remaining three methods restored biomechanical stability and improved it over that of the intact spine. Conclusions. The PLM/APSR fixation method was found to have the highest biomechanical stiffness followed by PTS, ATS, and AHPS fixation. The PLM/APSR fixation and AATS methods can be considered good procedures for stabilizing the atlantoaxial joints, although specific fixation methods are determined by the proper clinical and radiological characteristics in each patient.

A biomechanical comparison of the Rogers interspinous and the Lovely—Carl tension band wiring techniques for fixation of the cervical spine

2000 ◽  
Vol 93 (1) ◽  
pp. 109-116
Author(s):  
Albert V. B. Brasil ◽  
Danilo G. Coelho ◽  
Tarcísio Eloy P. B. Filho ◽  
Fernando M. Braga
Keyword(s):  
Cervical Spine ◽  
Axial Rotation ◽  
Tension Band ◽  
Tension Band Wiring ◽  
Lesion Group ◽  
Percentage Increase ◽  
Content Type ◽  
Flexion Extension ◽  
Biomechanical Evaluation ◽  
Fine Print

Object. The authors conducted a biomechanical study in which they compared the uses of the Rogers interspinous and the Lovely-Carl tension band wiring techniques for internal fixation of the cervical spine. Method. An extensive biomechanical evaluation (stiffness in positive and negative rotations around the x, y, and z axes; range of motion in flexion—extension, bilateral axial rotation, and bilateral bending; and neutral zone in flexion—extension, bilateral axial rotation, and lateral bending to the right and to the left) was performed in two groups of intact calf cervical spines. After these initial tests, all specimens were subjected to a distractive flexion Stage 3 ligamentous lesion. Group 1 specimens then underwent surgical fixation by the Rogers technique, and Group 2 specimens underwent surgery by using the Lovely—Carl technique. After fixation, specimens were again submitted to the same biomechanical evaluation. The percentage increase or decrease between the pre- and postoperative parameters was calculated. These values were considered quantitative indicators of the efficacy of the techniques, and the efficacy of the two techniques was compared. Conclusions. Analysis of the findings demonstrated that in the spines treated with the Lovely—Carl technique less restriction of movement was produced without affecting stiffness, compared with those treated with the Rogers technique, thus making the Lovely—Carl technique clinically less useful.

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