Abstract
Background context
Unstable burst fractures of the thoracolumbar spine may be treated surgically. Vertebral
body replacements (VBRs) give anterior column support and, when used with supplemental
fixation, impart rigidity to the injured segments. Although some VBRs are expandable,
device congruity to the vertebral end plates is imprecise and may lead to stress risers
and device subsidence.
Purpose
The objective of this study was to compare the rigidity of a VBR that self-adjusts
to the adjacent vertebral end plates versus structural bone allograft and with an
unsupported anterior column in a traumatic burst fracture reconstruction model.
Study design
Biomechanical flexibility testing with rod strain measurement.
Patient sample
Twelve T11–L3 human spine segments.
Outcome measures
Range of motion, neutral zone, and posterior fixation rod stress (moments).
Methods
Flexibility testing was performed to±6 Nm in flexion-extension, lateral bending, and
axial rotation on 12 intact human T11–L3 specimens. Burst fractures were created in
L1, and flexibility testing was repeated in three additional states: subtotal corpectomy
with posterior instrumentation (PI) only from T12 to L2, reconstruction with a femoral
strut allograft and PI, and reconstruction with a VBR (with self-adjusting end plates)
and PI. The PI consisted of pedicle screws and strain gage instrumented rods that
were calibrated to measure rod stress via flexion-extension bending moments.
Results
There was no statistical difference in range of motion or neutral zone between the
strut graft and VBR constructs, which both had less motion than the PI-only construct
in flexion/extension and torsion and were both less than the intact values in flexion/extension
and lateral bending (p<.05). Posterior rod moments were significantly greater for
the PI-only construct in flexion/extension relative to the strut graft and VBR states
(p=.03).
Conclusions
This study, which simulated the immediate postoperative state, suggests that a VBR
with self-adjusting end plate components has rigidity similar to the standard strut
graft when combined with PI. Posterior rod stress was not significantly increased
with this type of VBR compared with the strut graft reconstruction. The benefits of
burst fracture stabilization using a self-adjusting VBR ultimately will not be known
until long-term clinical studies are performed.
Keywords
To read this article in full you will need to make a payment
Purchase one-time access:
Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online accessOne-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:
Subscribe to The Spine JournalAlready a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
References
- Anterior decompression of traumatic thoracolumbar fractures with incomplete neurological deficit using a retroperitoneal approach.J Bone Joint Surg Am. 1985; 67: 89-104
- The management of acute thoracolumbar burst fractures with anterior corpectomy and Z-plate fixation.Spine. 2004; 29: 1901-1908
- Anterior-only stabilization of three-column thoracolumbar injuries.J Spinal Disord Tech. 2005; 18: S7-S14
- Selection criteria and outcome of operative approaches for thoracolumbar burst fractures with and without neurological deficit.J Neurosurg. 1997; 86: 48-55
- Anterior stabilization of thoracolumbar burst fractures using the Kaneda device: a preliminary report.Orthopedics. 1995; 18: 673-678
- Two column lesions in the thoracolumbar junction: anterior, posterior or combined approach? A comparative biomechanical in vitro investigation.Eur Spine J. 2007; 16: 813-820
- In vitro analysis of anterior and posterior fixation in an experimental unstable burst fracture model.J Spinal Disord Tech. 2008; 21: 216-224
- [Surgical treatment of injuries of the thoracolumbar transition. 2: operation and roentgenologic findings].Unfallchirurg. 2000; 103: 1032-1047
- Complications in surgical treatment of thoracolumbar injuries.Eur Spine J. 2002; 11: 214-226
- Surgical treatment of traumatic fractures of the thoracic and lumbar spine.Spine. 2004; 29: 803-814
- Anterior-only stabilization using plating with bone structural autograft versus titanium mesh cages for two- or three-column thoracolumbar burst fractures: a prospective randomized study.Spine. 2009; 34: 1429-1435
- Operative compared with nonoperative treatment of a thoracolumbar burst fracture without neurological deficit. A prospective, randomized study.J Bone Joint Surg Am. 2003; 85: 773-781
- Clinical outcome and radiographic results after surgical treatment of post-traumatic thoracolumbar kyphosis following simple type A fractures.Eur Spine J. 2004; 13: 101-107
- Effectiveness of titanium mesh cylindrical cages in anterior column reconstruction after thoracic and lumbar vertebral body resection.Spine. 2003; 28: 902-908
- Anterior vertebral body replacement with a titanium implant of adjustable height: a prospective clinical study.Eur Spine J. 2007; 16: 161-172
- Unstable thoracolumbar burst fractures: anterior-only versus short-segment posterior fixation.J Spinal Disord Tech. 2006; 19: 242-248
- Pain regulation and health-related quality of life after thoracolumbar fractures of the spine.Eur Spine J. 2007; 16: 1925-1933
- Low thoracic and lumbar burst fractures: radiographic and functional outcomes.Eur Spine J. 2007; 16: 1934-1943
- A prospective cohort study comparing the VAS spine score and Roland-Morris disability questionnaire in patients with a type A traumatic thoracolumbar spinal fracture.Eur Spine J. 2008; 17: 1096-1100
- Vertebral body replacement systems with expandable cages in the treatment of various spinal pathologies: a prospectively followed case series of 60 patients.Neurosurgery. 2008; 63: 537-544
- Angular stable anterior plating following thoracolumbar corpectomy reveals superior segmental stability compared to conventional polyaxial plate fixation.Spine. 2008; 33: 1429-1437
Rose PS, Buchl EH, Adickes MS et al. Early subsidence of expandable anterior vertebral body cages. 38th Annual Meeting of the Scoliosis Research Society; September 10–13, 2003; Quebec City, Canada.
- Preliminary results of staged anterior debridement and reconstruction using titanium mesh cages in the treatment of thoracolumbar vertebral osteomyelitis.Spine J. 2004; 4: 388-395
- The implications of stress patterns in the vertebral body under axial support of an artificial implant.Med Eng Phys. 2009; 31: 833-837
- Factors influencing stresses in the lumbar spine after the insertion of intervertebral cages: finite element analysis.Eur Spine J. 2003; 12: 413-420
- Evaluation of effects of selected factors on inter-vertebral fusion-a simulation study.Med Eng Phys. 2005; 27: 197-207
- Analysis of stress distribution in lumbar interbody fusion.Spine (Phila Pa 1976). 2005; 30: 1731-1735
- A biomechanical study of regional endplate strength and cage morphology as it relates to structural interbody support.Spine (Phila Pa 1976). 2004; 29: 2389-2394
- Biomechanical evaluation of contemporary posterior spinal internal fixation configurations in an unstable burst-fracture calf spine model: special references of hook configurations and pedicle screws.Spine. 2004; 29: 257-262
- Biomechanical testing of anterior and posterior thoracolumbar instrumentation in the cadaveric spine. Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004.J Neurosurg Spine. 2004; 1: 116-121
- Biomechanical studies on two anterior thoracolumbar implants in cadaveric spines.Spine. 1999; 24: 213-218
- Biomechanical evaluation of anterior and posterior fixations in an unstable calf spine model.Spine. 1997; 22: 261-266
- Biomechanical comparison of expandable cages for vertebral body replacement in the thoracolumbar spine.Spine. 2004; 29: 1413-1419
- Experimental study of thoracolumbar burst fractures. A radiographic and biomechanical analysis of anterior and posterior instrumentation systems.Spine. 1994; 19: 1711-1722
- Loads on a telemeterized vertebral body replacement measured in two patients.Spine. 2008; 33: 1170-1179
- In vitro, biomechanical comparison of an anterior lumbar interbody fusion with an anteriorly placed, low-profile lumbar plate and posteriorly placed pedicle screws or translaminar screws.Spine. 2005; 30: 1846-1851
- Thoracolumbar burst fracture. A biomechanical investigation of its multidirectional flexibility.Spine. 1994; 19: 578-585
- The incidence and distribution of burst fractures.Emerg Radiol. 2006; 12: 124-129
- Changes in the disc space after fractures of the thoracolumbar spine.J Bone Joint Surg Br. 1998; 80: 833-839
- Reliability of a novel classification system for thoracolumbar injuries: the Thoracolumbar Injury Severity Score.Spine. 2006; 31: S62-S69
- MR imaging of the traumatized lumbar spine.Magn Reson Imaging Clin N Am. 1999; 7: 589-602
- Stiffness of prosthetic nucleus determines stiffness of reconstructed lumbar calf disc.Spine J. 2004; 4: 265-274
- Comparative biomechanical testing of anterior and posterior stabilization procedures.Spine. 2005; 30: E352-E362
- Biomechanical evaluation of short-segment posterior instrumentation with and without crosslinks in a human cadaveric unstable thoracolumbar burst fracture model.Spine (Phila Pa 1976). 2010; 35: 278-285
- Load-sharing characteristics of stabilized lumbar spine segments.Spine. 2000; 25: 170-179
- Testing criteria for spinal implants: recommendations for the standardization of in vitro stability testing of spinal implants.Eur Spine J. 1998; 7: 148-154
- Three-dimensional motion analysis with Synex. Comparative biomechanical test series with a new vertebral body replacement for the thoracolumbar spine.Eur Spine J. 2000; 9: 472-485
- Instability of the lumbar burst fracture and limitations of transpedicular instrumentation.Spine. 1995; 20: 1452-1461
- Loads on an internal spinal fixation device during walking.J Biomech. 1997; 30: 41-47
- A method for the fatigue testing of pedicle screw fixation devices.J Biomech. 1994; 27: 1383-1388
- Two in vivo surgical approaches for lumbar corpectomy using allograft and a metallic implant: a controlled clinical and biomechanical study.Spine J. 2006; 6: 648-658
- Spinal segment range of motion as a function of in vitro test conditions: effects of exposure period, accumulated cycles, angular-deformation rate, and moisture condition.Anat Rec. 1998; 251: 15-19
Article info
Publication history
Accepted:
August 22,
2010
Received in revised form:
July 2,
2010
Received:
December 5,
2009
Footnotes
FDA device/drug status: not applicable.
Author disclosures: GRB (stock ownership, including options and warrants, Dynamic Spine; research support: staff/materials, Synthes Spine, Abbott Spine); ALF (other, Excelen); BPB (other, Excelen: Center for Bone & Joint Research and Education).
Funding for this study was in part provided by Dynamic Spine (San Diego, CA, USA).
Identification
Copyright
© 2010 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
