In silico investigation of the primary stability of different olif constructs in normal and osteoporotic conditions
Bereczki Ferenc
Clinical Medicine
Dr. Reusz György
MOM Kulturális Központ Simándy József terem
2024-09-18 08:30:00
Physiology and Pathology of the Musculoskeletal System
Dr. Szőke György
Dr.Éltes Péter, Dr.Lazáry Áron
Dr. Fabio Galbusera
Dr. Hangody György Márk
Dr. Szendrői Miklós
Dr. Hangody László Rudolf
Dr. Manó Sándor
The objective of this doctoral thesis was to conduct computerized in silico simulations to investigate the different implant constructs used in OLIF surgeries. Specifically, the focus was on comparing the two-step surgery required posterior fixation constructs (BPS) with the one-step surgery lateral plate systems (SSA, LPS) in normal and osteoporotic conditions. Additionally, the thesis aimed to determine if the use of PMMA augmentation could enhance primary stability and minimize differences between OLIF constructs in osteoporotic bone. The research was conducted in two parts.
In Part I of the thesis a spinal bi-segmental L2-4 finite element model was created, and validated based on the literature. The model was further modified to represent the presence of osteoporosis. Simplified 3D implant models used in OLIF surgeries were successfully incorporated into the L3-4 motion segment during a virtual surgical procedure, resulting in surgical finite element models. A two-step simulation method was employed, involving a follower-load followed by bending and rotational movements. Primary stability was assessed through four parameters: ROM of the operated segment, caudal displacement of the OLIF cage, maximum stress concentration on the endplate beneath the cage, and increased screw motion induced by osteoporosis. The results indicated that BPS provided superior biomechanical stability for OLIF cages compared to SSA or LPS constructs, under both normal and osteoporotic conditions. Furthermore, osteoporosis exacerbated the difference in the primary stability between the bilateral pedicle screw fixation and the two other investigated fixation methods.
In Part II of the thesis, the impact of PMMA augmentation on osteoporotic bone was examined for BPS and the novel SSA implant constructs. Surgical models with PMMA augmentation were created, with the amount of injected PMMA/screw gradually increasing from 1 cm3 to 6 cm3. The simulation method used was similar to that used in Part I. ROM, caudal displacement of the cage, and maximum stress concentrations on the endplate beneath the cage were investigated. The findings revealed that PMMA augmentation can enhance stability in both constructs, thereby reducing the existing disparity between them. The research suggests that injecting between 3 cm3 and 4 cm3 of PMMA per screw can achieve comparable stability to the BPS system in the SSA construct. Based on the findings, the concept of an SSA augmentation device is desirable but currently not available on the market.
