In selected cases, en-bloc spondylectomy is the only option to reach wide resection margins for patients with malignant tumours of the thoracolumbar spine. These patients must be also provided a secure initial stabilization of the spine and this is the role of vertebral body replacements employed with posterior fixation systems. The aim of this study was to determine the postimplantation stiffness of a connected vertebral body replacement pedicle screw system in different implantation scenarios following an en-bloc spondylectomy. Reconstruction was varied by posterior fixation lengths and axial compression forces during implantation.
Three-dimensional stiffness was assessed in 6 fresh frozen human spinal specimens (Th11-L3) using a six degree of freedom spine simulator. Following en-bloc spondylectomy reconstruction was performed using a carbon composite fibre vertebral body replacement connected to a posterior fixation system by two artificial pedicles. The spines were loaded with pure moments (7.5 Nm) in the three main motion planes. The intersegmental rotations were measured between Th12 and L2.
Reconstructions using long posterior fixation modes demonstrated significant (P < 0.05) higher stiffness compared to short posterior fixations in all motion planes. In axial rotation short posterior fixation modes failed to reach the values of the intact state. Neither high nor low axial compression force during implantation showed a significant impact on postfusional stiffness.
In this biomechanical model, the employed system should be implanted with a posterior fixation of two adjacent segments to the lesion in order to achieve a secure stabilization of the treated segment.
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- The transmission of stress to grafted bone inside a titanium mesh cage used in anterior column reconstruction after total spondylectomy: a finite-element analysis.Spine. 2005; 30: 2783-2787
- Effects of irradiation on posterior spinal fusions. A rabbit model.Spine. 1994; 19: 1836-1841
- Segmental pedicle screw fixation or cross-links in multilevel lumbar constructs. A biomechanical analysis.Spine J. 2001; 1: 373-379
- A biomechanical study of posterior spinal instrumentation using pedicle screws with and without cross-links.J. Spinal Disord. Tech. 2005; 18: 364-368
- Surgical technique of en bloc spondylectomy for solitary metastases of the thoracolumbar spine.Unfallchirurg. 2007; 110: 163-170
- A biomechanical analysis of metastatic vertebral collapse of the thoracic spine: a sheep model study.Spine. 2004; 29: 994-999
- 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
- Spinal radiation before surgical decompression adversely affects outcomes of surgery for symptomatic metastatic spinal cord compression.Spine. 2001; 26: 818-824
- Combined stabilization of thoracolumbar spine fractures.Eur. J. Trauma. 2006; 32: 249-252
- Biomechanical analysis of thoracolumbar interbody constructs. How important is the endplate?.Spine. 1996; 21: 1032-1036
- Biomechanical evaluation of the stability of thoracolumbar burst fractures.Spine. 1994; 19: 1731-1740
- Range of motion in reconstruction situations following corpectomy in the lumbar spine: a question of bone mineral density?.Spine. 2005; 30: E229-E235
- 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
- Complications in surgical treatment of thoracolumbar injuries.Eur. Spine J. 2002; 11: 214-226
- The stability of reconstruction methods after thoracolumbar total spondylectomy. An in vitro investigation.Spine. 1999; 24: 1634-1638
- Biomechanical evaluation of spinal fixation devices: I. A conceptual framework..Spine. 1988; 13: 1129-1134
- Biomechanical time-tolerance of fresh cadaveric human spine specimens.J. Orthop. Res. 1985; 3: 292-300
- Biomechanical comparison of expandable cages for vertebral body replacement in the thoracolumbar spine.Spine. 2004; 29: 1413-1419
- Total excision of thoracic vertebrae (author’s transl).Rev. Chir. Orthop. Reparatrice Appar. Mot. 1981; 67: 421-430
- Is a single anterolateral screw-plate fixation sufficient for the treatment of spinal fractures in the thoracolumbar junction? A biomechanical in vitro investigation.Eur. Spine J. 2005; 14: 197-204
- Axial compression force measurement acting across the strut graft in thoracolumbar instrumentation testing.Clin. Biomech. 2003; 18: 631-636
- Biomechanical analysis of anterior poly-methyl-methacrylate reconstruction following total spondylectomy for metastatic disease.Spine. 2004; 29: 2012-2096
- Total spondylectomy in chondrosarcoma arising from the seventh thoracic vertebra.J. Bone Joint Surg. Br. 1971; 53: 288-295
- Vertebral body replacement with an expandable cage for reconstruction after spinal tumor resection.Neurosurg. Focus. 2003; 15: E8
- Total en bloc spondylectomy and circumspinal decompression for solitary spinal metastasis.Paraplegia. 1994; 32: 36-46
- Total en bloc spondylectomy. A new surgical technique for primary malignant vertebral tumors.Spine. 1997; 22: 324-333
- Stability potential of spinal instrumentations in tumor vertebral body replacement surgery.Spine. 1998; 23: 543-550
- Surgical approach to spine tumors.Orthopedics. 1989; 12: 897-905
- A universal spine tester for in vitro experiments with muscle force simulation.Eur. Spine J. 1994; 3: 91-97
- 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
- Testing criteria for spinal implants: recommendations for the standardization of in vitro stability testing of spinal implants.Eur. Spine J. 1998; 7: 148-154
- Stiffness between different directions of transpedicular screws and vertebra.Clin. Biomech. 1998; 13: S1-S8
Published online: September 13, 2007
Accepted: July 3, 2007
Received: November 15, 2006
© 2007 Elsevier Ltd. Published by Elsevier Inc. All rights reserved.