TESSYS Technique With Small Grade of Facetectomy Has Potential Biomechanical Advantages Compared to the In-Out TED With Intact Articular Process : An In-Silico Study

Abstract

Background: The facetectomy was reported as an important procedure in both in-out and out-in (i.e. transforaminal endoscopic spine system (TESSYS)) techniques in the transforaminal endoscopic discectomy (TED), and which was also related to the deterioration of postoperative biomechanical environment and related poor prognosis. Recently, the facetectomy was reported to be avoided in the modified in-out TED, but iatrogenic injury of annulus and related larger grades of nucleotomy can also be seen as risk factors for the prognosis deterioration. Meanwhile, above mentioned risk factors can be alleviated in TESSYS TED, and the grade of facetectomy can also be reduced in this surgery with the use of endoscopic dynamic drill. Methods: To evaluate the risk of biomechanical deterioration and related postoperative complications of these two surgical modified strategies in TED, an intact lumbo-sacral finite element model and the corresponding model with adjacent segments degeneration have been constructed and validated, modified in-out and TESSYS TED have been simulated in these models. Then, the change of biomechanical indicators have been computed to evaluate the risk of postoperative complications in the surgical segement. Results: Compared with intact FEA models, the tendency of biomechanical deterioration in TESSYS TED models was generally slight. By contrast, obvious biomechanical deterioration can be observed in models with modified in-out TED. The degenerative change in adjacent segments magnifies rather than alters the overall tendency of biomechanical change. Conclusions: Modified TESSYS TED with a small grade of facetectomy has potential biomechanical advantages compared with the in-out TED with intact articular process (i.e. without facetectomy). The iatrogenic injury of annulus and larger grade of nucleotomy can be seen as risk factors for postoperative biomechanical deteriorations and complications in the surgical segment.