Speaker
Description
Introduction:
Osteochondral (OC) lesions to the knee represent a major burden from a societal and economic point of view, affecting young and active patients and predisposing them to develop post-traumatic osteoarthritis. Current treatments include marrow stimulation, autografts, and cell-based therapies; however, they all suffer from several limitations, including availability, cost and complexity of the procedure [1], highlighting the need for new and effective procedures. In this context, we present the design and fabrication of an extrusion toolhead for in situ bioprinting in the knee, as a regenerative, one-stage solution to treat OC defects.
Experimental section:
A literature survey of the current landscape of commercial arthroscopic devices was conducted to screen the tools currently available on the market. Based on ergonomics considerations, two preliminary designs of the extrusion toolhead were manufactured with Fused Deposition Modelling (FDM). Briefly, the two configurations have different handles depending on the grip type, including precision (pencil-like) and power grips. The extrusion is performed using a leadscrew mechanism and is actuated by a stepper motor with reduced weight to increase the comfort when holding the device. Each configuration includes a CNC milled aluminium block to maintain the ink inside the syringe at 37°C, facilitating the extrusion of gelatin-based inks and enabling their processing. Finally, the extrusion process is controlled using a dedicated board (Ramps v1.4) with the ad hoc configured Marlin firmware.
To test the toolheads in a simulated environment, a human knee phantom was designed and fabricated starting from CT scans of a femur and a tibia. Both bones were manufactured using FDM printing, while the cartilage parts (i.e., femoral and tibia cartilage, menisci) were prepared using ad hoc designed molds. The softer femoral and tibia articular cartilage [2], were prepared with Ecoflex 00-10 silicone (1:1), while the more rigid menisci [3] were obtained using Sylgard-184 silicone (1:10). OC defects of varying size were prepared by coring with a punch directly on the femoral cartilage. Finally, a usability test is currently being conducted with three surgeons at the University of Pisa, experts in arthroscopic procedures. They were tasked with using the two configurations to fill the OC defect prepared on the phantom and asked to provide their feedback through an ad hoc questionnaire.
Conclusions:
Herein, we presented the design and fabrication of custom toolheads for in situ extrusion bioprinting inside the knee, with the aim of regenerating OC defects in a minimally invasive, arthroscopic set-up. The design process was conducted with attention to usability and ergonomics, to facilitate the uptake of the technology in possible future clinical applications. Future developments will include the addition of other bioprinting technologies, like jetting and Filamented Light, to create complex multimaterial and multiscale constructs directly inside the knee.
Acknowledgments:
This project has received funding by the European Union under the call HORIZON-HLTH-2024-TOOL-11-02 (LUMINATE, 101191804).
References:
[1]: Solanki, K., et al. (2021). Journal of clinical orthopaedics and trauma, 22, 101602.
[2]: Salinas, E. Y., et al. (2023). Cartilage, 14(3), 338-350.
[3]: Abdelgaied, A., et al. (2015). Journal of biomechanics, 48(8), 1389-1396.
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