Intra-hospital patient-specific 3D printed surgical guide for patients with thoracic scoliotic deformities, the collaboration between engineer and surgeon

Abstract

Background: This study validates the intra-hospital design and 3D printing process of personalized surgical guides to enhance the accuracy of pedicle screw insertion in patients with thoracic scoliotic deformities. It introduces a novel collaborative paradigm between surgeons and engineers, aiming to improve efficiency and reduce errors in the manufacturing of patient-specific instruments (PSIs).

Methods: The process began with the generation of 3D biomodels of vertebrae from computed tomography scans. Surgical guides were then created using two 3D printing techniques: Fused Filament Fabrication (FFF) with polylactic acid (PLA) and Stereolithography (SLA) with photopolymer resin. Three different prototypes were compared based on multifactorial indicators, including economic cost, macroscopic surface finish, and mechanical stability. The mechanical performance of the guides was evaluated under loads generated during pedicle screw penetration and threading.

Results and discussions: PLA models printed using FFF were found to be cheaper and simpler to manufacture than SLA resin models. Despite differences observed under a microscope, PLA models exhibited a macroscopic surface finish comparable to that of SLA resin models. Both materials demonstrated similar mechanical properties, although their values were lower than those reported in the manufacturer's datasheet. Importantly, both types of guides successfully withstood the mechanical loads generated during surgical procedures. The intra-hospital collaboration between engineers and surgeons was identified as a key factor in improving outcomes and reducing error risks, showcasing the benefits of interdisciplinary teamwork.

Conclusions: 3D-printed PSIs made from PLA using FFF are more cost-effective and quicker to produce compared to SLA resin models, while achieving similar results in surface finish and mechanical stability. The implementation of a collaborative approach between engineers and surgeons within hospital settings enhances the efficiency and accuracy of patient-specific surgical guide manufacturing, offering a promising solution for improving surgical outcomes in thoracic scoliotic deformities.

Keywords: 3D printing; Engineer-surgeon; Patient-specific surgical guide; Surgical planning.

Fig. 1

Flow chart of the research methodology

Fig. 2

a) Spine segmentation in Invesalius^®; b-c) Examples of the T11 and T10 vertebrae

Fig. 3

a) Complete spine made in Meshmixer^®; b) L4 vertebra; c) Example of needle trajectory in the L1 vertebra

Fig. 4

a) First design of the L1 vertebra; b) Second design on the L3 vertebra; c) Third design of the T12 vertebra; d) Orthogonal views with some measurements in mm of the PSI for T12

Fig. 5

a) Preparation for printing T12 and T9 vertebra guide in Ultimaker Cura^®; b) Printing process of PSIs for vertebrae L2 and L3 in PLA with PLA supports; c) Completed PSIs for vertebrae T9 and T12 with supports

Fig. 6

a) Preparation for printing PSIs in Preform^®; b) Printing process of PSIs in the FORMLABS^® 3 + printer; c) PSIs after completion of printing in the FORMLABS^® 3+

Fig. 7

1BA-type specimens used for tensile testing

Fig. 8

Experimental tests: a) PLA PSI on the spine model made of PLA; b) Resin PSI on the spine model made of resin.

Fig. 9

a) Prototype 1 for the L1 vertebra; b) Prototype 2 for the T9 vertebra; c) Prototype 3 for the T8 vertebra

Fig. 10

Sample provided by Company 1. a) PSI with K-needle; b) Rear view, without needles

Fig. 11

Reliability analysis of the 3D printing of PSI samples and broken specimens; a) Measurement of the internal hole of one of the PSI legs manufactured in PLA (21x magnification); b) Measurement of the internal hole of one of the PSI legs manufactured in Resin (25x magnification); c) Measurement of the cross-section of a Resin specimen used in the tensile test (21x magnification); d) Measurement of the cross-section of a PLA specimen used in the tensile test (20x magnification)