Mate Turbucz

Purpose: The objective of this systematic review is to present a comprehensive summary of existing research on the use of 3D printing in spinal surgery. Methods: The researchers conducted a thorough search of four digital databases (PubMed, Web of Science, Scopus, and Embase) to identify relevant studies published between January 1999 and December 2022. The review focused on various aspects, including the types of objects printed, clinical applications, clinical outcomes, time and cost considerations, 3D printing materials, location of 3D printing, and technologies utilized. Out of the 1620 studies initially identified and the 17 added by manual search, 105 met the inclusion criteria for this review, collectively involving 2088 patients whose surgeries involved 3D printed objects. Results: The studies presented a variety of 3D printed devices, such as anatomical models, intraoperative navigational templates, and customized implants. The most widely used type of objects are drill guides (53%) and anatomical models (25%) which can also be used for simulating the surgery. Custom made implants are much less frequently used (16% of papers). These devices significantly improved clinical outcomes, particularly enhancing the accuracy of pedicle screw placement. Most studies (88%) reported reduced operation times, although two noted longer times due to procedural complexities. A variety of 3DP technologies and materials were used, with STL, FDM, and SLS common for models and guides, and titanium for implants via EBM, SLM, and DMLS. Materialise software (Mimics, 3-Matic, Magics) was frequently utilized. While most studies mentioned outsourced production, in-house printing was implied in several cases, indicating a trend towards localized 3D printing in spine surgery. Conclusions: 3D printing in spine surgery, a rapidly growing area of research, is predominantly used for creating drill guides for screw insertion, anatomical models, and innovative implants, enhancing clinical outcomes and reducing operative time. While cost-efficiency remains uncertain due to insufficient data, some 3D printing applications, like pedicle screw drill guides, are already widely accepted and routinely used in hospitals.

Finite element (FE) analyses contribute to a better understanding of the human lumbar spine’s biomechanics and serve as an effective predictive tool. This study aims to present the development of two L1–L5 FE models using literature-based (LBM) and patient-specific (PSM) bone material assignment approaches. The geometry of the lumbar spine was developed based on quantitative computed tomography scans. The LBM and the PSM were compared under pure and combined loads. Various biomechanical parameters were investigated to validate the models. The total range of motion of the LBM in pure flexion-extension, lateral bending, and axial rotation were 30.9°, 29°, and 13.7°, respectively, while for the PSM, it was 31.6°, 28.6°, and 14.1°. The required computational time of the PSM to complete against pure and combined loads were 12.1 and 16.6 times higher on average compared to the LBM. This study demonstrated that both models agree with experimental and in silico results, although the cumulative distribution of the stress and characterization of strain values showed a noteworthy difference between the two models. Based on these findings, the clinically-focused biomechanical FE studies must perceive the differences in internal mechanical parameters and computational demand between the different bone modelling approaches.