scholarly journals Axial Spondylectomy and Circumferential Reconstruction via a Posterior Approach

Neurosurgery ◽  
2012 ◽  
Vol 72 (2) ◽  
pp. E300-E309 ◽  
Author(s):  
Rahul Jandial ◽  
Brandon Kelly ◽  
Brandon Bucklen ◽  
Saif Khalil ◽  
Aditya Muzumdar ◽  
...  
Keyword(s):  
Spinal Metastases ◽  
Cervical Vertebra ◽  
Biomechanical Analysis ◽  
The Novel ◽  
Lateral Mass ◽  
Lateral Bending ◽  
Patient Case ◽  
Flexion Extension ◽  
Anterior Column Reconstruction ◽  
Flexion And Extension

Abstract BACKGROUND: Spinal metastases of the second cervical vertebra are a subset of tumors that are particularly difficult to address surgically. Previously described techniques require highly morbid circumferential dissection posterior to the pharynx for resection and reconstruction. OBJECTIVE: To perform a biomechanical analysis of instrumented reconstruction configurations used after axial spondylectomy and to demonstrate safe use of a novel construct in a patient case report. METHODS: Several different published and novel reconstruction configurations were inserted into 7 occipitocervical spines that underwent axial spondylectomy. A biomechanical analysis of the stiffness of the constructs in flexion and extension, lateral bending, and rotation was performed. A patient then underwent a posterior-only approach for axial spondylectomy and circumferential reconstruction. RESULTS: Biomechanical analysis of different constructs demonstrated that anterior column reconstruction with bilateral cages spanning the C1 lateral mass to the C3 facet in combination with occipitocervical instrumentation was superior in flexion-extension and equivalent in lateral bending and rotation to currently used constructs. The patient in whom this construct was placed via a posterior-only approach for axial spondylectomy and instrumentation remained at neurological baseline and demonstrated no recurrence of local disease or failure of instrumentation to date. CONCLUSION: When C1 lateral mass to C3 facet bilateral cage plus occipitocervical instrumentation is compared with existing anterior and posterior constructs, this novel reconstruction is biomechanically equivalent if not superior in performance. In a patient, the posterior-only approach for C2 spondylectomy with the novel reconstruction was safe and durable and avoided the morbidity of the anterior approach.

scholarly journals Atlantoaxial fixation using C1 posterior arch screws: feasibility study, morphometric data, and biomechanical analysis

2019 ◽  
Vol 30 (3) ◽  
pp. 314-322 ◽  
Author(s):  
Gilbert Cadena ◽  
Huy T. Duong ◽  
Jonathan J. Liu ◽  
Kee D. Kim
Keyword(s):  
Biomechanical Testing ◽  
Axial Rotation ◽  
Biomechanical Analysis ◽  
Posterior Arch ◽  
Lateral Mass ◽  
Morphometric Data ◽  
Lateral Bending ◽  
Freehand Technique ◽  
Flexion Extension ◽  
Low Incidence

OBJECTIVEC1–2 is a highly mobile complex that presents unique surgical challenges to achieving biomechanical rigidity and fusion. Posterior wiring methods have been largely replaced with segmental constructs using the C1 lateral mass, C1 pedicle, C2 pars, and C2 pedicle. Modifications to reduce surgical morbidity led to the development of C2 laminar screws. The C1 posterior arch has been utilized mostly as a salvage technique, but recent data indicate that this method provides significant rigidity in flexion-extension and axial rotation. The authors performed biomechanical testing of a C1 posterior arch screw (PAS)/C2 pars screw construct, collected morphometric data from a population of 150 CT scans, and performed a feasibility study of a freehand C1 PAS technique in 45 cadaveric specimens.METHODSCervical spine CT scans from 150 patients were analyzed to determine the average C1 posterior tubercle thickness and size of C1 posterior arches. Eight cadavers were used to compare biomechanical stability of intact specimens, C1 lateral mass/C2 pars screw, and C1 PAS/C2 pars screw constructs. Paired comparisons were made using repeated-measures ANOVA and Holm-Sidak tests. Forty-five cadaveric specimens were used to demonstrate the feasibility and safety of the C1 PAS freehand technique.RESULTSMorphometric data showed the average craniocaudal thickness of the C1 posterior tubercle was 12.3 ± 1.94 mm. Eight percent (12/150) of cases showed thin posterior tubercles or midline defects. Average posterior arch thickness was 6.1 ± 1.1 mm and right and left average posterior arch length was 28.7 mm ± 2.53 mm and 28.9 ± 2.29 mm, respectively. Biomechanical testing demonstrated C1 lateral mass/C2 pars and C1 PAS/C2 pars constructs significantly reduced motion in flexion-extension and axial rotation compared with intact specimens (p < 0.05). The C1 lateral mass/C2 pars screw construct provided significant rigidity in lateral bending (p < 0.05). There was no statistically significant difference between the two constructs in flexion-extension, lateral bending, or axial rotation. Of the C1 posterior arches, 91.3% were successfully cannulated using a freehand technique with a low incidence of cortical breach (4.4%).CONCLUSIONSThis biomechanical analysis indicates equivalent stability of the C1 PAS/C2 pars screw construct compared with a traditional C1 lateral mass/C2 pars screw construct. Both provide significant rigidity in flexion-extension and axial rotation. Feasibility testing in 45 cadaveric specimens indicates a high degree of accuracy with low incidence of cortical breach. These findings are supported by a separate radiographic morphometric analysis.

The cervical end of an occipitocervical fusion: a biomechanical evaluation of 3 constructs

2008 ◽  
Vol 9 (3) ◽  
pp. 296-300 ◽  
Author(s):  
Michael A. Finn ◽  
Daniel R. Fassett ◽  
Todd D. Mccall ◽  
Randy Clark ◽  
Andrew T. Dailey ◽  
...  
Keyword(s):  
Tracking System ◽  
Plate Fixation ◽  
Axial Rotation ◽  
Lateral Mass ◽  
Lateral Bending ◽  
Cross Link ◽  
3D Tracking ◽  
Flexion Extension ◽  
Biomechanical Evaluation ◽  
Rotation Motion

Object Stabilization with rigid screw/rod fixation is the treatment of choice for craniocervical disorders requiring operative stabilization. The authors compare the relative immediate stiffness for occipital plate fixation in concordance with transarticular screw fixation (TASF), C-1 lateral mass and C-2 pars screw (C1L-C2P), and C-1 lateral mass and C-2 laminar screw (C1L-C2L) constructs, with and without a cross-link. Methods Ten intact human cadaveric spines (Oc–C4) were prepared and mounted in a 7-axis spine simulator. Each specimen was precycled and then tested in the intact state for flexion/extension, lateral bending, and axial rotation. Motion was tracked using the OptoTRAK 3D tracking system. The specimens were then destabilized and instrumented with an occipital plate and TASF. The spine was tested with and without the addition of a cross-link. The C1L-C2P and C1L-C2L constructs were similarly tested. Results All constructs demonstrated a significant increase in stiffness after instrumentation. The C1L-C2P construct was equivalent to the TASF in all moments. The C1L-C2L was significantly weaker than the C1L-C2P construct in all moments and significantly weaker than the TASF in lateral bending. The addition of a cross-link made no difference in the stiffness of any construct. Conclusions All constructs provide significant immediate stability in the destabilized occipitocervical junction. Although the C1L-C2P construct performed best overall, the TASF was similar, and either one can be recommended. Decreased stiffness of the C1L-C2L construct might affect the success of clinical fusion. This construct should be reserved for cases in which anatomy precludes the use of the other two.

scholarly journals Biomechanical evaluation of the ProDisc-C stability following graded posterior cervical injury

2018 ◽  
Vol 29 (5) ◽  
pp. 515-524
Author(s):  
Michael D. Staudt ◽  
Doron Rabin ◽  
Ali A. Baaj ◽  
Neil R. Crawford ◽  
Neil Duggal
Keyword(s):  
Axial Rotation ◽  
Control Group ◽  
Lateral Bending ◽  
Cervical Injury ◽  
Cervical Arthroplasty ◽  
Posterior Surgery ◽  
Flexion Extension ◽  
Posterior Element ◽  
And Control ◽  
Flexion And Extension

OBJECTIVEThere are limited data regarding the implications of revision posterior surgery in the setting of previous cervical arthroplasty (CA). The purpose of this study was to analyze segmental biomechanics in human cadaveric specimens with and without CA, in the context of graded posterior resection.METHODSFourteen human cadaveric cervical spines (C3–T1 or C2–7) were divided into arthroplasty (ProDisc-C, n = 7) and control (intact disc, n = 7) groups. Both groups underwent sequential posterior element resections: unilateral foraminotomy, laminoplasty, and finally laminectomy. Specimens were studied sequentially in two different loading apparatuses during the induction of flexion-extension, lateral bending, and axial rotation.RESULTSRange of motion (ROM) after artificial disc insertion was reduced relative to that in the control group during axial rotation and lateral bending (13% and 28%, respectively; p < 0.05) but was similar during flexion and extension. With sequential resections, ROM increased by a similar magnitude following foraminotomy and laminoplasty in both groups. Laminectomy had a much greater effect: mean (aggregate) ROM during flexion-extension, lateral bending, and axial rotation was increased by a magnitude of 52% following laminectomy in the setting of CA, compared to an 8% increase without arthroplasty. In particular, laminectomy in the setting of CA introduced significant instability in flexion-extension, characterized by a 90% increase in ROM from laminoplasty to laminectomy, compared to a 16% increase in ROM from laminoplasty to laminectomy without arthroplasty (p < 0.05).CONCLUSIONSForaminotomy and laminoplasty did not result in significant instability in the setting of CA, compared to controls. Laminectomy alone, however, resulted in a significant change in biomechanics, allowing for significantly increased flexion and extension. Laminectomy alone should be used with caution in the setting of previous CA.

scholarly journals Biomechanical Analysis of an Anterior Cervical Discectomy and Fusion Pseudarthrosis Model Revised With Machined Interfacet Allograft Spacers

2019 ◽  
Vol 10 (8) ◽  
pp. 973-981
Author(s):  
Raymond J. Hah ◽  
Ram Alluri ◽  
Paul A. Anderson
Keyword(s):  
Range Of Motion ◽  
Study Design ◽  
Axial Rotation ◽  
Biomechanical Analysis ◽  
Anterior Cervical Discectomy ◽  
Lateral Bending ◽  
Cervical Discectomy ◽  
Single Level ◽  
Flexion Extension ◽  
Potential Applications

Study Design: Biomechanics study. Objectives: To evaluate the biomechanical advantage of interfacet allograft spacers in an unstable single-level and 2-level anterior cervical discectomy and fusion (ACDF) pseudoarthrosis model. Methods: Nine single-level and 8 two-level ACDF constructs were tested. Range of motion in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) at 1.5 N m were collected in 4 testing configurations: (1) intact spine, (2) ACDF with interbody graft and plate/screw, (3) ACDF with interbody graft and plate/loosened screws (loose condition), and (4) ACDF with interbody graft and plate/loosened screws supplemented with interfacet allograft spacers (rescue condition). Results: All fixation configurations resulted in statistically significant decreases in range of motion in all bending planes compared with the intact spine ( P < .05). One Level. Performing ACDF with interbody graft and plate on the intact spine reduced FE, LB, and AR 60.0%, 64.9%, and 72.9%, respectively. Loosening the ACDF screws decreased these reductions to 40.9%, 44.6%, and 52.1%. The addition of interfacet allograft spacers to the loose condition increased these reductions to 74.0%, 84.1%, and 82.1%. Two Level. Performing ACDF with interbody graft and plate on the intact spine reduced FE, LB, and AR 72.0%, 71.1%, and 71.2%, respectively. Loosening the ACDF screws decreased these reductions to 55.4%, 55.3%, and 51.3%. The addition of interfacet allograft spacers to the loose condition significantly increased these reductions to 82.6%, 91.2%, and 89.3% ( P < .05). Conclusions: Supplementation of a loose ACDF construct (pseudarthrosis model) with interfacet allograft spacers significantly increases stability and has potential applications in treating cervical pseudarthrosis.

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.

Biomechanical analysis of Goel technique for C1–2 fusion

2011 ◽  
Vol 14 (5) ◽  
pp. 639-646 ◽  
Author(s):  
Jon Park ◽  
Justin K. Scheer ◽  
T. Jesse Lim ◽  
Vedat Deviren ◽  
Christopher P. Ames
Keyword(s):  
Motion Tracking ◽  
Tracking System ◽  
Testing Machine ◽  
Pedicle Screws ◽  
Axial Rotation ◽  
Biomechanical Analysis ◽  
Lateral Bending ◽  
Flexion Extension ◽  
Rod System ◽  
Harms Technique

Object The Goel technique, in which C1–2 intraarticular spacers are used, may be performed to restore stability to a disrupted atlantoaxial complex in conjunction with the Harms technique of placing polyaxial screws and bilateral rods. However, it has yet to be determined biomechanically whether the addition of the C1–2 joint spacers increases the multiaxial rigidity of the fixation construct. The goal of this study was to quantify changes in multiaxial rigidity of the combined Goel-Harms technique with the addition of C1–2 intraarticular spacers. Methods Seven cadaveric cervical spines (occiput–C2) were submitted to nondestructive flexion-extension, lateral bending, and axial rotation tests in a material testing machine spine tester. The authors applied 1.5 Nm at a rate of 0.1 Nm/second and held it constant for 10 seconds. The specimens were loaded 3 times, and data were collected on the third cycle. Testing of the specimens was performed for the following groups: 1) intact (I); 2) with the addition of C-1 lateral mass/C-2 pedicle screws and rod system (I+SR); 3) with C1–2 joint capsule incision, decortication (2 mm on top and bottom of each joint [that is, the C-1 and C-2 surface) and addition of bilateral C1–2 intraarticular spacers at C1–2 junction to the screws and rods (I+SR+C); 4) after removal of the posterior rods and only the bilateral spacers in place (I+C); 5) after removal of spacers and further destabilization with simulated odontoidectomy for a completely destabilized case (D); 6) with addition of posterior rods to the destabilized case (D+SR); and 7) with addition of bilateral C1–2 intraarticular spacers at C1–2 junction to the destabilized case (D+SR+C). The motion of C-1 was measured by a 3D motion tracking system and the motion of C-2 was measured by the rotational sensor of the testing system. The range of motion (ROM) and neutral zone (NZ) across C-1 and C-2 were evaluated. Results For the intact spine test groups, the addition of screws/rods (I+SR) and screws/rods/cages (I+SR+C) significantly reduced ROM and NZ compared with the intact spine (I) for flexion-extension and axial rotation (p < 0.05) but not lateral bending (p > 0.05). The 2 groups were not significantly different from each other in any bending mode for ROM and NZ, but in the destabilized condition the addition of screws/rods (D+SR) and screws/rods/cages (D+SR+C) significantly reduced ROM and NZ compared with the destabilized spine (D) in all bending modes (p < 0.05). Furthermore, the addition of the C1–2 intraarticular spacers (D+SR+C) significantly reduced ROM (flexion-extension and axial rotation) and NZ (lateral bending) compared with the screws and rods alone (D+SR). Conclusions Study result indicated that both the Goel and Harms techniques alone and with the addition of the C1–2 intraarticular spacers to the Goel-Harms technique are advantageous for stabilizing the atlantoaxial segment. The Goel technique combined with placement of a screw/rod construct appears to result in additional construct rigidity beyond the screw/rod technique and appears to be more useful in very unstable cases.

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.

scholarly journals Biomechanical Comparison of Posterior Fixation Combinations with an Allograft Spacer between the Lateral Mass and Pedicle Screws

2020 ◽  
Vol 10 (20) ◽  
pp. 7291
Author(s):  
Soo-Bin Lee ◽  
Hwan-Mo Lee ◽  
Tae-Hyun Park ◽  
Sung Lee ◽  
Young-Woo Kwon ◽  
...  
Keyword(s):  
Pedicle Screws ◽  
Element Model ◽  
Axial Rotation ◽  
Posterior Fixation ◽  
Hybrid Technique ◽  
Lateral Mass ◽  
Lateral Bending ◽  
Flexion Extension ◽  
Hybrid Motion ◽  
Biomechanical Comparison

Background: There are a few biomechanical studies that describe posterior fixation methods with pedicle screws (PS) and lateral mass screws (LMS); the combination of both screw types and their effect on an allograft spacer in a surgically treated cervical segment is unknown. Methods: Finite element model (FEM) analyses were used to investigate the effects of a hybrid technique using posterior PS and LMS. Stress distribution and subsidence risk from a combination of screws under hybrid motion control conditions, including flexion, extension, axial rotation, and lateral bending, were investigated to evaluate the biomechanical characteristics of different six-screw combinations. Findings: The load sharing on the allograft spacer in flexion mode was highest in the LMS model (74.6%) and lowest in the PS model (35.1%). The likelihood of subsidence of allograft spacer on C6 was highest in the screws from the distal LMS (type 5) model during flexion and extension (4.902 MPa, 30.1% and 2.189 MPa, 13.4%). In lateral bending, the left unilateral LMS (type 4) model screws on C5 (3.726 MPa, 22.9%) and C6 (2.994 MPa, 18.4%) yielded the greatest subsidence risks, because the lateral bending forces were supported by the LMS. In counterclockwise axial rotation, the left unilateral LMS (type 4) model screws on C5 (3.092 MPa, 19.0%) and C6 (3.076 MPa, 18.9%) demonstrated the highest subsidence risks. Conclusion: The asymmetrical ipsilateral use of LMS and posterior PS in lateral bending and axial rotation demonstrated the lowest stability and greatest subsidence risk. We recommend bilateral symmetrical insertion of LMS or posterior PS and posterior PS on distal vertebrae for increased stability and reduced risk of allograft spacer subsidence.

Biomechanical analysis of stand-alone lumbar interbody cages versus 360° constructs: an in vitro and finite element investigation

2021 ◽  
pp. 1-9
Keyword(s):  
Interbody Fusion ◽  
Posterior Instrumentation ◽  
Axial Rotation ◽  
Posterior Fixation ◽  
Interbody Cage ◽  
Lateral Bending ◽  
Flexion Extension ◽  
Lateral Interbody ◽  
Flexion And Extension

OBJECTIVE Low fusion rates and cage subsidence are limitations of lumbar fixation with stand-alone interbody cages. Various approaches to interbody cage placement exist, yet the need for supplemental posterior fixation is not clear from clinical studies. Therefore, as prospective clinical studies are lacking, a comparison of segmental kinematics, cage properties, and load sharing on vertebral endplates is needed. This laboratory investigation evaluates the mechanical stability and biomechanical properties of various interbody fixation techniques by performing cadaveric and finite element (FE) modeling studies. METHODS An in vitro experiment using 7 fresh-frozen human cadavers was designed to test intact spines with 1) stand-alone lateral interbody cage constructs (lateral interbody fusion, LIF) and 2) LIF supplemented with posterior pedicle screw-rod fixation (360° constructs). FE and kinematic data were used to validate a ligamentous FE model of the lumbopelvic spine. The validated model was then used to evaluate the stability of stand-alone LIF, transforaminal lumbar interbody fusion (TLIF), and anterior lumbar interbody fusion (ALIF) cages with and without supplemental posterior fixation at the L4–5 level. The FE models of intact and instrumented cases were subjected to a 400-N compressive preload followed by an 8-Nm bending moment to simulate physiological flexion, extension, bending, and axial rotation. Segmental kinematics and load sharing at the inferior endplate were compared. RESULTS The FE kinematic predictions were consistent with cadaveric data. The range of motion (ROM) in LIF was significantly lower than intact spines for both stand-alone and 360° constructs. The calculated reduction in motion with respect to intact spines for stand-alone constructs ranged from 43% to 66% for TLIF, 67%–82% for LIF, and 69%–86% for ALIF in flexion, extension, lateral bending, and axial rotation. In flexion and extension, the maximum reduction in motion was 70% for ALIF versus 81% in LIF for stand-alone cases. When supplemented with posterior fixation, the corresponding reduction in ROM was 76%–87% for TLIF, 86%–91% for LIF, and 90%–92% for ALIF. The addition of posterior instrumentation resulted in a significant reduction in peak stress at the superior endplate of the inferior segment in all scenarios. CONCLUSIONS Stand-alone ALIF and LIF cages are most effective in providing stability in lateral bending and axial rotation and less so in flexion and extension. Supplemental posterior instrumentation improves stability for all interbody techniques. Comparative clinical data are needed to further define the indications for stand-alone cages in lumbar fusion surgery.

Augmentation of Anterior Lumbar Interbody Fusion with Anterior Pedicle Screw Fixation: Demonstration of Novel Constructs and Evaluation of Biomechanical Stability in Cadaveric Specimens

Neurosurgery ◽  
2006 ◽  
Vol 58 (3) ◽  
pp. 522-527 ◽  
Author(s):  
Aftab Karim ◽  
Debi Mukherjee ◽  
Murali Ankem ◽  
Jorge Gonzalez-Cruz ◽  
Donald Smith ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Interbody Fusion ◽  
Axial Rotation ◽  
The Novel ◽  
Lumbar Interbody Fusion ◽  
Lateral Bending ◽  
Biomechanical Stability ◽  
Current Standard ◽  
Computed Tomographic ◽  
Flexion Extension

Abstract OBJECTIVE: Anterior lumbar interbody fusion (ALIF) has proven effective for indications including discogenic back pain, nonunion, and instability. Current practice involves posterior pedicle screw augmentation of the ALIF procedure (ALIF-PPS). This approach requires intraoperative repositioning of the patient for percutaneous posterior pedicle screw placement. We have developed a novel technique in which the ALIF procedure is augmented with anterior pedicle screws (APS; ALIF-APS). In this study, we introduce this new technique and compare the biomechanical stability of the novel ALIF-APS with the current standard ALIF-PPS. METHODS: The technique was demonstrated in a cadaveric L4–S1 specimen using neuronavigation and fluoroscopy. Plain radiographs and computed tomographic scans of the construct were obtained. Twelve cadaveric spines (7 men and 5 women) from donors with an average age of 81 years (range, 64–93 yr) were then harvested from L4–S1. Six specimens were dedicated to ALIF-APS constructs, and the remaining six were dedicated to ALIF-PPS constructs. The specimens were then studied at L5–S1 in the following steps: 1) intact form, 2) after anterior discectomy, 3) after implantation of titanium cages (ALIF), and 4) after APS or PPS fixation in conjunction with the ALIF. Measurements were obtained in axial rotation and left and right lateral bending flexion-extension. Data were normalized by calculating the ratio of the stiffness of the instrumented to the intact spine. Statistical analyses were then performed on the data. RESULTS: Radiographs and computed tomographic scans of the construct showed accurate placement of the APS at L5 and S1. The normalized data showed that ALIF-APS and ALIF-PPS had approximately equal stability in axial rotation (1.17 ± 0.43 versus 0.85 ± 0.14), lateral bending (0.93 ± 0.22 versus 0.95 ± 0.16), and flexion- extension (0.77 ± 0.13 versus 0.84 ± 0.2). Paired t test analysis did not show a significant difference between the biomechanical stiffness of ALIF-APS and ALIF-PPS in axial rotation, lateral bending, and flexion-extension. CONCLUSION: We demonstrate a new technique in a cadaveric specimen whereby the ALIF procedure is augmented with APS fixation using neuronavigation and fluoroscopy. Biomechanical evaluation of the constructs suggests that the ALIF-APS has comparable stability with ALIF-PPS. APS augmentation of ALIF has potential advantages over the current standard ALIF-PPS because it can 1) eliminate the patient repositioning step, 2) minimize the total number of incisions and the total operative time, and 3) protect against dislocation of the ALIF interbody graft or cage. Work is in progress to develop a low-profile system for the novel APS constructs described here.

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