Shukri, Farid Fikri
(2018)
Effect of graded laminectomy and facetectomy on biomechanical properties of normal lumbar spine : a finite element study.
Masters thesis, Universiti Sains Malaysia.
Abstract
Graded laminectomy and facetectomy are techniques for decompressing neural structure in
the lumbar spine. However this resection techniques normally lead to a decrease in spinal
stability. Previous experimental studies were based on in vitro human cadaver model to
determine the instability of lumbar spine following graded decompression surgery. However,
there are some major limitations in these experimental studies in which the inability to
determine the intrinsic parameters such as loads, stresses and strains over the intervertebral
disc and vertebra bodies after the surgery. In order to investigate spinal stability and the
intrinsic parameters after decompression spinal surgery, a finite element analysis of the
lumbar spine was performed. Intersegmental motions of lumbar vertebrae, stresses of
intervertebral disc and vertebra bodies were calculated while simulating an intact spine as
well as different extents of resection (hemilaminectomy, hemifacetectomy, total
laminectomy and total facetectomy).
METHODOLOGY
A three-dimensional, non-linear finite element model of the lumbar spine was created using
Mimic 10.01 software and meshed using 3-Matic 11.0 software . Only one model of lumbar
finite element L1-L5 was constructed from a normal lumbar CT images, and this finite
element model was extrapolated to represent the human population with normal lumbar spine.
Since no in vitro experiment is done in our study, the validation of our finite element model is
based on previous experimental study. Then, spinal decompression procedures are simulated
on the lumbar model using Marc Mentat 2010 software. There is no statistical analysis as the
result is analysed directly from decompression surgery of one normal lumbar model, hence,
there is no hypothesis in our study.
RESULT
For surgery that preserved the spinous process (hemilaminectomy, hemifacetectomy and total
facetectomy), the displacement of the spine are 1.31o, 1.20o, 1.37o. However, when the
spinous process is resected (laminectomy), the displacement of the spine in flexion rise up to
3.43o which was increased 4.53% compared to intact model. The displacement of lumbar
spine in extension post decompression surgery are 1.85o, 1.87o, 1.91o and 1.95o. The result
showed near equal displacement of lumbar spine in extension after each simulation surgery.
There is high stress concentration post decompression surgery over anterior aspect of the
intervertebral disc L3/L4 in flexion group otherwise low in extension group. The increased ,
stress concentration on vertebra bodies also produce different pattern in each decompression
surgery during flexion and extension.
CONCLUSION
Graded laminectomy and facetectomy of lumbar spine in finite element analysis shows
increase in intersegmental motion that lead to spinal instability. In our study, total
laminectomy affect stability the most by having more intersegmental mobility and most
intervertebral disc stress in flexion. Total facetectomy affect the intervertebral disc stress
more in flexion but only have slight increase of intersegmental motion in flexion. This shows
that total laminectomy produce the most instability compared to total facetectomy.
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