Elsevier

World Neurosurgery

Volume 139, July 2020, Pages e255-e264
World Neurosurgery

Original Article
Biomechanical Model Study of the Effect of Partial Facetectomy on Lumbar Stability Under Percutaneous Endoscopy

https://doi.org/10.1016/j.wneu.2020.03.190Get rights and content

Objective

To investigate the effect of partial facetectomy on lumbar stability using percutaneous endoscopy.

Methods

Five male adult volunteers with no history of lumbar disease participated in the study. Based on computed tomography data, a three-dimensional model of the L3-S1 segment was created using the Mimics l5.0 and Ansys 13.0 software. The use of an 8.5-mm-diameter ring saw was simulated to cut through 5 different needle insertion points (IPs) commonly used in the clinic on the left-side facet joint (FJ) of L5 to perform facetectomy. The first to third IPs were on the apex of the superior FJ, the midpoint of the ventral side of the superior FJ, and the lowest point of the ventral side of the superior FJ. The fourth and fifth IPs represented the positions of the second and third IPs (8.5 mm/2) after the radius of the ring saw was translated to the dorsal side of the superior FJ. Physiologic load was applied to the human models. The pressure on the left and right FJ of the L5 vertebra, the pressure on the L4-5 intervertebral disc, and the range of motion of the lumbar spine were recorded when normal flexion and extension and lateral flexion and rotation of the lumbar spine model after facetectomy were simulated.

Results

Compared with the intact group, the second IP, maximum pressure on the L4-5 intervertebral disc after facetectomy was not significantly different under any condition (P > 0.05). The maximum pressure on the left FJ of L5 showed significant differences during right rotation of the lumbar spine (P < 0.05). The pressure on the right FJ of L5 was significantly different during left rotation of the lumbar spine (P < 0.05). The range of motion of the lumbar spine was not significantly different under any condition (P > 0.05).

Conclusions

The second IP at the midpoint of the ventral side of the superior FJ showed minimal effect on lumbar spine biomechanics compared with all the other IPs during percutaneous transforaminal facetectomy. Thus, it can be considered as the most suitable IP for facetectomy.

Introduction

Because of the continuous development of minimally invasive spinal techniques over recent years, transforaminal endoscopic spine system (TESSYS) surgery has gradually become the preferred option for the surgical treatment of lumbar disc herniation, because it is minimally invasive and allows rapid recovery.1, 2, 3 However, some patients who have undergone TESSYS surgery for lumbar disc herniation have subsequently had lumbar instability. Several retrospective clinical reviews have come to the same conclusion.4,5 During TESSYS surgery, some parts of the facet joint (FJ) are removed to effectively decompress the lumbar spine and enlarge the working channel of the endoscope.6 However, numerous experimental biomechanical studies have shown that the FJ affects the stability of the lumbar spine.7, 8, 9, 10 Therefore, the selection of the most appropriate insertion point (IP) on the FJ, able to establish a working channel that minimizes lumbar instability, is critical for successful facetectomy. It is unknown whether IPs commonly used in the clinic are the most appropriate in terms of biomechanics. These are the key issues addressed by this research study.

Section snippets

Development of a Three-Dimensional Finite Element Model

Five healthy male volunteers of similar age, height, and weight, with no family history of lumbar disease, participated in the study. All volunteers provided signed informed consent. The presence of low back pain, lumbar deformity, or any lumbar spine diseases were ruled out through examination. Each volunteer was scanned by a three-dimensional (3D) lumbar vertebral computed tomography (CT) scanner (General Electric Company, Boston, Massachusetts, USA) to acquire lumbar CT images. The acquired

Proportion of FJ Resected During Facetectomy

Because facetectomy was performed through different IPs, the angles between the ring saw and the FJs were different; thus, the volumes of resected FJs were also different. To calculate the volume of resected FJ for each model, the Mimics software was used to cut the complete left superior FJ of L5 in the same way for each model and then calculate the volume. The left FJ volume of the resected models was subtracted from the left FJ volume of the intact models to determine the resected FJ volume

Discussion

In TESSYS surgery, an insertion is performed under local anesthesia in the posterior aspect of the vertebral body to allow direct entry into the spinal canal for free discectomy. The surgery is conducted away from the outlet and dorsal root ganglia, avoiding the muscles and ligaments adjacent to the vertebral body as far as possible.15 Compared with open surgery, the postoperative visual analog scale score, Oswestry Disability Index, and complications have been significantly reduced.16 In

Conclusions

The finite element analysis showed that the first IP (at the apex of the superior FJ), commonly used in TESSYS surgery, is not the most appropriate. Using the second IP (at the midpoint of the ventral side of the superior FJ) has minimal impact on the biomechanics of the lumbar spine, which changed when the removed volume of the superior FJ was >27.15%. The conclusions of these simulations can help guide the most appropriate surgical process for facetectomy under TESSYS. The most appropriate IP

CRediT authorship contribution statement

Xin-ru Li: Conceptualization, Methodology, Software, Investigation, Writing - original draft. Jia Yu: Validation, Formal analysis, Visualization, Software. Wen Zhang: Validation, Formal analysis, Visualization. Gong-ming Gao: Data curation, Supervision, Writing - review & editing. Long Han: Resources, Writing - review & editing, Supervision. Liang Chen: Writing - review & editing. Lu-ming Nong: Resources, Writing - review & editing, Supervision, Data curation.

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  • Conflict of interest statement: The research was supported by General Project of Jiangsu Provincial Department of Health (H2019025), The Project of Invigorating Health Care through Science, Technology and Education (Jiangsu Provincial Medical Youth Talent), Changzhou High-level Medical Talents Training Project (2016CZBJ029), and Six Talent Peaks Project, Jiangsu Provincial Finance Department (WSW-186), the National Key R&D Program of China (No. 2018YFB1107000), the National Natural Science Foundation of China (11572211).

    Xin-ru Li, Jia Yu, and Wen Zhang contributed equally as first authors.

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