The Effect of Spinal Destabilization and Instrumentation on Lumbar Intradiscal Pressure: An In Vitro Biomechanical Analysis

Study Design. In vitro biomechanical testing was performed in human cadaveric lumbar spines, using pressure needle transducers to analyze the effects of spinal destabilization and instrumentation on lumbar intradiscal pressures. Objectives. To quantify changes in lumbar intradiscal pressures at three adjacent disc levels under conditions of spinal reconstruction, and to evaluate the possibility of pressure‐induced disc pathology secondary to spinal instrumentation. Summary of Background Data. Lumbar intradiscal pressures under in vivo and in vitro conditions and the use and development of spinal instrumentation have been investigated comprehensively. However, the effects of spinal destabilization and instrumentation on lumbar intradiscal pressure have not been delineated clearly. Methods. In 11 human cadaveric lumbosacral specimens, specially designed pressure needle transducers quantified intradiscal pressure changes at three adjacent disc levels (L2‐L3, proximal; L3‐L4, operative; and L4‐L5, distal) under four conditions of spinal stability: intact, destabilized, laminar hook and pedicle screw reconstructions. Biomechanical testing was performed under axial compression (0‐600 N), anterior flexion (+12.5°) and extension (−12.5°), after which the level of degeneration and disc area (cm2) were quantified. Results. In response to destabilization and instrumentation, proximal disc pressures increased as much as 45%, and operative pressure levels decreased 41‐55% (P < 0.05), depending on the instrumentation technique. Linear regression and correlation analyses comparing intradiscal pressure to the grade of disc degeneration were not significant (r = 0.24). Conclusions. Changes in segmental intradiscal pressure levels occur in response to spinal destabilization and instrumentation (P < 0.05). Intradiscal cyclic pressure differentials drive the metabolic production and exchange of disc substances. Conditions of high or low disc pressure secondary to spinal instrumentation may serve as the impetus for altered metabolic exchange and predispose operative and adjacent levels to disc pathology.

[1]  T. Taylor,et al.  The effect of spinal fusion on intervertebral disc composition: an experimental study. , 1976, The Journal of surgical research.

[2]  J. Schlegel,et al.  Lumbar Motion Segment Pathology Adjacent to Thoracolumbar, Lumbar, and Lumbosacral Fusions , 1996, Spine.

[3]  J. Leong,et al.  Long‐Term Results of Lumbar Intervertebral Disc Prolapse , 1983, Spine.

[4]  A. Nachemson.  The Load on Lumbar Disks in Different Positions of the Body , 1966, Clinical orthopaedics and related research.

[5]  A. Nachemson,et al.  Lumbar intradiscal pressure. Experimental studies on post-mortem material. , 1960, Acta orthopaedica Scandinavica. Supplementum.

[6]  H. Ranu.  Measurement of Pressures in the Nucleus and within the Annulus of the Human Spinal Disc: Due to Extreme Loading , 1990, Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine.

[7]  V K Goel,et al.  Effect of Disc Degeneration at One Level on the Adjacent Level in Axial Mode , 1991, Spine.

[8]  A. Naylor,et al.  Fluid Content of the Nucleus Pulposus as a Factor in the Disk Syndrome* , 1953, British medical journal.

[9]  R. Harris,et al.  ACQUIRED SPONDYLOLYSIS AS A SEQUEL TO SPINE FUSION. , 1963, The Journal of bone and joint surgery. American volume.

[10]  S. L. Griffith,et al.  Intradiscal Pressure Measurements Above an Instrumented Fusion: A Cadaveric Study , 1995, Spine.

[11]  R Louis,et al.  Fusion of the lumbar and sacral spine by internal fixation with screw plates. , 1986, Clinical orthopaedics and related research.

[12]  H. Tsuji,et al.  Water Diffusion Pathway, Swelling Pressure, and Biomechanical Properties of the Intervertebral Disc During Compression Load , 1989, Spine.

[13]  A. Brodsky.  Post-laminectomy and post-fusion stenosis of the lumbar spine. , 1976, Clinical orthopaedics and related research.

[14]  A NACHEMSON,et al.  Measurement of intradiscal pressure. , 1959, Acta orthopaedica Scandinavica.

[15]  CASEY K. LEE,et al.  Accelerated Degeneration of the Segment Adjacent to a Lumbar Fusion , 1988, Spine.

[16]  F. Magerl.  Stabilization of the lower thoracic and lumbar spine with external skeletal fixation. , 1984, Clinical orthopaedics and related research.

[17]  A NACHEMSON,et al.  THE EFFECT OF FORWARD LEANING ON LUMBAR INTRADISCAL PRESSURE. , 1965, Acta orthopaedica Scandinavica.

[18]  L. Unander-Scharin.  Spinal fusion in low back pain. , 1951, Acta orthopaedica Scandinavica.

[19]  E R Luque,et al.  The Anatomic Basis and Development of Segmental Spinal Instrumentation , 1982, Spine.

[20]  S. Holm,et al.  Variations in the Nutrition of the Canine Intervertebral Disc Induced by Motion , 1983, Spine.

[21]  R. Biscup,et al.  Segmental spine plates with pedicle screw fixation. A new internal fixation device for disorders of the lumbar and thoracolumbar spine. , 1986, Clinical orthopaedics and related research.

[22]  S. Rolander.  Motion of the lumbar spine with special reference to the stabilizing effect of posterior fusion. An experimental study on autopsy specimens. , 1966, Acta orthopaedica Scandinavica.

[23]  B. Cunningham,et al.  1989 Volvo Award in Basic Science: Device-Related Osteoporosis with Spinal Instrumentation , 1989, Spine.

[24]  A. Nachemson,et al.  IN VIVO MEASUREMENTS OF INTRADISCAL PRESSURE. DISCOMETRY, A METHOD FOR THE DETERMINATION OF PRESSURE IN THE LOWER LUMBAR DISCS. , 1964, The Journal of bone and joint surgery. American volume.

[25]  J Krämer,et al.  Pressure dependent fluid shifts in the intervertebral disc. , 1977, The Orthopedic clinics of North America.

[26]  M. Adams,et al.  Internal Intervertebral Disc Mechanics as Revealed by Stress Profilometry , 1992, Spine.

[27]  J. Zucherman,et al.  Lumbar Laminectomy for Herniated Disc: A Prospective Controlled Comparison with Internal Fixation Fusion , 1987, Spine.

[28]  McAfee Pc,et al.  A Biomechanical Analysis of Spinal Instrumentation Systems in Thoracolumbar Fractures: Comparison of Traditional Harrington Distraction Instrumentation with Segmental Spinal Instrumentation , 1985 .