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Anatomically Precise Revolutionary Implant for bone Conserving Osteoarthritis Treatment

Periodic Reporting for period 1 - APRICOT (Anatomically Precise Revolutionary Implant for bone Conserving Osteoarthritis Treatment)

Reporting period: 2019-10-01 to 2020-09-30

Prevalence and incidences of osteoarthritis (OA) vary depending on age, sex and study type, but an overall prevalence of 43.3% is estimated for OA in the hand. This prevalence is higher than that seen for the hip and knee, which are far more studied. There are currently no effective interventions known to restore natural joint kinematics while alleviating pain associated with the progression of degenerative bone disease of small joints. Current treatment programmes of pharmacological and non-pharmacological modalities can present complications with long-term use, such as liver and renal failure. Surgical (arthroplasty) intervention traditionally involves a metal or pyrocarbon component articulating against a polymer component in a hinge-like configuration to impart flexion and extension. However, complications, such as implant loosening or fracture, do occur, necessitating revision surgery. Silicone based implants are to date the gold standard in finger arthroplasty and offer much reduced reoperation rates. Nevertheless, they indicate similar rates of dislocation and deviation and – in the long run – high implant fracture rates (up to 30%). Crucially, state of the art implants cannot provide a natural range of motion, and they also lack shock absorption functionality as provided by native cartilage. Due to the limited options for the patient, fusion or arthrodesis of the joint is considered as a viable alternative, in particular for the toes and ankle. This is less of an option for the hand, where function is critical for most day-to-day activities. The patient therefore often lives with joint pain, and a severely impaired quality of life.

The vision of the APRICOT project is to create a radically new type of implant for the effective treatment of osteoarthritis (OA) of small joints. The APRICOT is an innovative patented and highly compliant thin flexible implant, which can be positioned minimally invasively within the affected joint space, restoring the joint’s natural kinematics, without the need for healthy bone removal, differentiating it from all current implant solutions.

Success for the APRICOT concept will benefit the patient in several ways. In addition to reducing or removing pain in the joints, implantation of the device will restore dignity and empower the patients, allowing them to return to work or contribute to their community. It will also decrease post-op healthcare costs and potential mental health issues resulting from feelings of isolation and withdrawal from society. This is particularly relevant today as people are living longer and keeping active in later life.

To achieve this, the team are employing state of the art materials science, modelling, manufacturing, and testing technologies to create, test, characterise and demonstrate prototype implants, and progress the concept towards clinical trials post project, subject to securing funding.
In the first reporting period, the team consulted with the clinician panel to determine a suitable joint to demonstrate the concept. initially, the digital hinge joints of the hand were selected, and the metacarpophalangeal (MCP) joint of the thumb was identified as an appropriate candidate for the technology based on its geometry, size, relative ease of surgical access, and the lack of an existing solution for MCP arthritis.
Patient public involvement strategies were undertaken to gain an understanding of the problems faced by patients, their concerns, and get an idea of which potential benefits were most important to them.
Computational modelling of the thumb joint progressed beyond the state of the art through the development of a fundamental statistical shape model that helped the team understand how the shape of the joint varies between individuals.
Various manufacturing strategies were investigated and the design of the device was developed with the aim of facilitating the application of coating and fixation treatments. This has generated new IP for Aurora Medical.
Bespoke test rigs have been designed that will enable the device performance to be assessed under typical loading conditions and geometries relevant to the MCP joint.
Concepts for fixation have been refined, with three alternative strategies currently running in parallel, ready for further evaluation.
Initial screening tests have indicated that two coating strategies are appropriate for the surfaces of the device, these will be further optimised in due course.
A project website has been created and regularly populated with new information. The communication, dissemination, and exploitation strategy has been refined, including establishing four Key Exploitable Results.
A Project Management Platform has been constructed to assist with the management of the project. Much communication, both bilateral and larger multi-partner meetings, has taken place.
The APRICOT implant goes beyond the state-of-the-art by obviating the need for (i) bone removal and (ii) two solid components articulating against each other (enabling minimally invasive implantation), and allowing for (iii) the creation of cartilage like friction and damping capabilities and (iv) natural range of motion and kinematics. It will create a paradigm shift in the way OA of small joints is treated by replicating the functionality of cartilage using a novel design principle based on caterpillar track movement. This motion prevents sliding movement at the anatomical surfaces, thus preventing wear at the implant site. This immobility will be strengthened using specially designed fixation features. As any articulation occurs within the implant, in the unlikely event that wear debris is generated, it will be retained within the sac. APRICOT will restore mobility without the need to remove healthy bone, and will avoid the need to subject the (often frail) patients to general anaesthetics and traumatic operating procedures.
The targeted breakthrough is to demonstrate the APRICOT concept, that is, to synthesize the latest advances in the fields of additive manufacturing, fixation technology, surface modification, and implant simulation to create a device that will restore pain free natural motion to small joints. This involves: (i) the selection of state of the art polymers and optimisation of their processing to realize a functionally graded implant with optimised mechanical properties; (ii) the development of a minimally invasive implantable fixation system using a combination of novel biological glues and a mechanical fixation into the subchondral bone for initial fixation, augmented by a biologically active coating for long term fixation; (iii) the development of surface functionalization protocols and fluid filling compositions that allow cartilage-like ultra-low friction kinematics and (iv) creation of novel computational models of small joints based on established musculoskeletal modelling of the hip and knee. All these efforts will be complemented by the development of novel dedicated mechanical and tribological test protocols specific to small joints.
The project addresses critical limitations in the treatment of osteoarthritis by creating a highly original, risky, but potentially very high gain solution. A paradigm shift in joint restoration will be achieved by integrating novel innovative scientific approaches to deliver a solution that has the potential to place Europe at the forefront of small joint arthroplasty.