BMTH: 3D-printed Implants Creating Better Outcomes for a Common Wrist Injury
Pictured from left, Director of the Griffith Centre of Biomedical and Rehabilitation Engineering (GCORE), Professor David Lloyd, and Associate Professor David Saxby GCORE and DECRA Fellow of the Australian Research Council – key members of the Griffith University team paving the way to address the challenges linked to SLIL injuries – the most common of wrist ligament injuries.
A pioneering technique, developed by Griffith Centre of Biomedical and Rehabilitation Engineering (GCORE), that designs personalised bone-ligament-bone grafts using 3D-printed biocompatible scaffolds is set to create positive results for people afflicted with a scapholunate interosseous ligament (SLIL) injury – the most common of wrist ligament injuries.
The SLIL joins the scaphoid and lunate bones, which are bones critical to normal movement of the wrist. The overall incidence of wrist trauma is reported to be approximately 70 out of 10,000 individuals and many of these cases involve rupture of the SLIL. The SLIL rupture is particularly prevalent in athletic populations, with men of an average age of 40 years at elevated risk of this injury. Rupture of the SLIL causes dislocation of the scaphoid and lunate bones and can be career-ending for an athlete and limit productivity for those employed in manual labour. Typically, SLIL injuries are surgically treated, but have poor prognosis, with patients developing functional limitations and severe hand/wrist osteoarthritis, which impairs long-term health and imposes a substantial economic burden. Currently, there is no commercially available product that provides reliable and effective treatment for SLIL rupture.
In 2020, the global orthopaedic soft tissue repair market was valued at US$5.9 billion and is forecast to escalate at a compound annual growth rate of 6.3 per cent up to 2028. Meanwhile, in 2016, the tissue scaffold market segment was worth US$2.3 billion, addressing common injuries to tendons and ligaments, such as the anterior cruciate ligament (ACL) of the knee and SLIL. The small joint sub-segment accounted for ~10 per cent of the market, or US$230 million. Although there have been synthetic grafts developed for ACL surgeries, there is no market product for SLIL repair.
The Griffith Centre of Biomedical and Rehabilitation Engineering (GCORE), in close collaboration with clinical orthopaedics and regenerative medicine partners (WA-based Orthocell), sought to develop a world-first robust technology to address this unmet clinical need. The focus of its BioMedTech Horizons (BMTH) program funded project was to support preclinical research and development (R&D) to demonstrate viability of a SLIL reconstruction product at technology readiness level 5. Further partnerships with commercial partners would follow to develop the product to engineering scales, in compliance with market regulators, and for human clinical trials.
The Griffith University team leveraged three cutting-edge technologies for the BMTH project, which it had developed alongside its industry partners: the 3D-printed synthetic bone-ligament-bone biomechanical scaffold, which had been demonstrated to be effective in small- and medium-sized animal models; the maturation of the 3D-printed graft ligament using stem cells; and the creation of 3D computer musculoskeletal simulations from medical images of the patient’s wrist to design a personalised surgical procedure for each patient.
Within this BMTH project, two interconnected and concurrent streams of research were conducted. Stream one refined the 3D-printed graft, by formalising a computer design process to optimise graft mechanical performance, which was then verified experimentally by performing biomechanical testing. Stream two used ‘digital twins’ of intact cadaveric wrists to simulate wrist mechanics during common daily tasks and apply them to real cadaveric wrist specimens using robotic control framework.
Digital twins are a digital representation of the graft, tissue and human organ (e.g., the wrist) that inform surgical interventions, and are an application of digital engineering used to design the graft and surgery, improve clinical outcomes, reduce material waste and save money.
The team achieved all the goals of the project, which included surgically installing the implant into nine human cadaveric wrists. Getting to this point involved completion of numerous project milestones: 3D imaging of the wrist to create a personalised physical anatomical model, as well as a digital twin; using the digital twin to custom design a scaffold for safe installation and mechanical performance; design of custom surgical instruments for installation of the implant; fabrication of the implant and surgical instruments using 3D printing; successful installation of the stem-cell seeded and mechanically improved artificial ligament into three cadaveric wrists; control of the robot using the digital twin to successfully manipulate the wrist during the installation process; and finally, robotic testing and mechanical performance reports on the cadaver wrist-forearm complex.
Pictured, from left, a CAD image of the 3D Printed graft ligament, and computer modelling to show the 3D Printed graft ligament implant in the wrist.
The 3D modelling of the geometric and mechanical properties of the 3D-printed graft permitted detailed analysis and planning of the design and implantation of the synthetic ligament. Using digital twins, the Griffith University team made extensive iterative computational assessments and improvements to the device and surgical procedures, including the specific anchor points in the cashew-sized and-shaped scaphoid bone and the smaller crescent-shaped lunate bone to maximise mechanical performance, resulting in an ability to tailor surgical implants for each patient. These models were proven in test surgical procedures using cadaveric wrists.
An additional benefit was the realisation of a significant simplification of the otherwise complex and difficult surgery, resulting from the custom surgical instruments. This is expected to reduce theatre time by more than half, offering major cost savings for hospitals and other surgery providers. An advanced understanding was gained of the required regulatory pathways for key markets in the US, Europe and Australia. This advice has helped the Griffith team shape the direction of further development and sharpened its ability to communicate with current and future industry partners.
The outcomes of this project have paved the way to address the challenges linked to SLIL injuries – namely, long-term chronic difficulties and the considerable health and economic burden for impacted individuals. The Griffith team will continue to expand its cutting-edge technology through the next stage of clinical trial and validation: a world-first clinical trial to demonstrate the viability of a 3D-printed and reconstructed SLIL for human applications.
Sources:
https://pubmed.ncbi.nlm.nih.gov/8282472/
https://www.heighpubs.org/hceop/aceo-aid1004.php
https://journals.sagepub.com/doi/10.1177/1558944718787289
https://www.orthobullets.com/hand/6041/scapholunate-ligament-injury-and-disi
https://www.grandviewresearch.com/industry-analysis/soft-tissue-repair-market
https://www.grandviewresearch.com/industry-analysis/orthopedic-soft-tissue-repair-market