The Biomechanics of Lumbar Graded Facetectomy Under Anterior-Shear Load

Abstract

In this paper, an anatomically accurate three-dimensional finite-element (FE) model of the human lumbar spine (L2-L3) was used to study the biomechanical effects of graded bilateral and unilateral facetectomies of L3 under anterior shear. The intact L2-L3 FE model was validated under compression, tension, and shear loading and the predicted responses matched well with experimental data. The gross external (translational and coupled) responses, flexibilities, and facet load were delineated for these iatrogenic changes. Results indicted that unilateral facetectomy of greater than 75% and bilateral facetectomy of 75% or more resection markedly alter the translational displacement and flexibilities of the motion segment. This study suggests that fixation or fusion to restore strength and stability of the lumbar spine may be required for surgical intervention of greater than 75% facetectomy.

Poroelastic Analysis of Lumbar Spinal Stability in Combined Compression and Anterior Shear

“…Natarajan et al 5 reported a substantial sudden change in rotational motion of the motion segment, due to applied torsion moment, after 75% removal of any one of the facet joints. Similar observations were also reported by Teo et al, 6 who concluded that complete unilateral facetectomy of >75% and bilateral facetectomy of 75% resection markedly altered the translational displacement and flexibilities, especially the motion segment with complete bilateral facetectomy. But these earlier elastostatic FE models were based on elastic constitutive laws and assumed the annulus and nucleus to consist of only a single phase.…”

“…4 Over the years, a number of mathematical models have been developed to investigate the instability of a motion segment. [4][5][6] For mathematical modeling purposes, the finite element (FE) method is the method of choice, in particular as biologic structures usually exhibit an irregular geometry and often undergo large deformations. Also, facilitated by the availability of powerful digital computers, the FE method has been applied to more complex models.…”

Validation of a clinical finite element model of the human lumbosacral spine

“…Goel et al [12] validated L4-L5 model with data from the Schultz et al [29] study. The finite element model of the L2-L3 segment in the Teo et al [38] study was validated with data from Panjabi et al [22] experiments. It should be noted that researchers have published entire moment-rotation curves under different loading modes.…”

Hemilaminoplasty for the treatment of lumbar intraspinal synovial cysts (LISCs) and literature review

“…Furthermore, we do not think that partial medial facetectomy, systematically performed in our series even in case of spondylolisthesis, compromise segmental stability. Natarajan and Teo [43,44] found that unilateral facetectomy of less than 75 % could induced negligible translational displacement and flexibilities of lumbar finite element model and could not require primary fusion, whereas medial facetectomy in our cohort is just to resect the hypertrophic part which results from segmental instability and spondylolisthesis, only accounting for about 25 % of the facet joint. The minimally invasive cystectomy using a tubular contralateral approach advocated by Rhee et al [45] may prevent facet disruption and postoperative instability, but with normal aging, the degenerated facet hypertrophy will cause further lateral recess and central canal stenosis which make medial facetectomy a mandatory step for decompression of the exiting nerve root and dural sac, regardless of the open or minimally invasive approach.…”