Shape memory bone and soft tissue fixations

Building on our current research, we will explore enhanced bone to bone and soft tissue to bone fixation devices made from bionert and bioresorbable shape memory polymers (SMP). These recover or partially recover an initial shape when subject to an appropriate stimulus (usually heating) above their glass transition temperature. SMPs will be structured by processing operations, to obtain controlled molecular orientation, whose recovery drives shape reversion. The research will be undertaken in close collaboration with Innovate Orthopaedics, a medical device company and Clinicians from the Fortius Clinic.
The proposed research will address: (i) specific unmet clinical needs in major market segments, (including shoulder and knee ligament injuries, meniscal tears and scaphoid fractures); (ii) treatment of specific patient subgroups to achieve a reduced overall recovery time, including a faster 'return to function' time, e.g. older people - over 50's are more susceptible to traumatic and degenerative injuries; rising levels of obesity are a risk factor in arthritis and meniscal injury; high performance athletes, or military personnel/ manual workers suffer sports or job-related trauma; for most cases, such injuries bring a significant socio-economic cost; (iii) overcoming known deficiencies in existing products (e.g. loosening metal compression screws); (iv) enhanced functionality for surgeons, with the potential for shorter theatre times and simplified procedures, and significantly reduced inventories.
In our research:
(i) SMPs will be formulated for specific applications, by including plasticisers to control reversion onset temperature, and other additives;
(ii) SMPs will be structured by (a) solid phase processing, to obtain controlled molecular orientation, whose recovery drives shape reversion, (b) by precision injection moulding, and (c) by hybrid processing using a range of techniques including: overmoulding of SMP cores; reversion moulding; reverting SMPs into moulded end features; developing novel geometries to reduce heat transfer to tissue; 3-d printing of two materials for solid phase processing.;
(ii) Triggering of shape recovery by body T fluid (saline 37C); micro resistance heating probe; a hybrid
route - trigger start of recovery by heating probe, with prolonged body T reversion by plasticisers; local ultrasound heating
(iii) controlled reversion in clinically relevant timescales - fast or slow according to application, using controlled reversion triggering temperature, including body temperature - and degree of reversion;
(iv) the balance between bioresorption rate and interference force and pull out force from bone (Leeds University facilities);
(iii) the value of shape memory behaviour in accommodating variations in bone and fixing hole quality;
(v) match of bone properties/ osteogenesis including incorporation of nano hydroxyapatite and antiinflammatories being developed in our labs;
(v) modelling (finite element analysis) of stresses in SMP fixations to inform optimal design.
Partner Roles:
Clinicians - a) define Clinical challenges/ requirements for specific indications, especially scaphoid
compression screws and soft tissue fixations, including ACL and rotator cuff repair; b) input to design
of fixation devices and c) help remove barriers to clinical adoption;
Industry - evaluate a) market size, b) process economics, c) routes to market, d) device designs
Regulatory - we will engage with MHRA and BSI via our MeDe Innovation Centre.

We aim for significant healthcare impact from our research, with commercially significant outcomes, with a defined route to regulatory certification and a clear patent pathway, particularly in bone to bone and tissue to bone fixation devices for a range of orthopaedic repairs.
Healthcare impacts will be in (i) meeting specific unmet clinical needs in major market segments, (including shoulder and knee ligament injuries, meniscal tears and scaphoid fractures); (ii) treatment of specific patient subgroups to achieve a reduced overall recovery time, including a faster 'return to function' time, e.g. older people - over 50's are more susceptible to traumatic and degenerative injuries; rising levels of obesity are a risk factor in arthritis and meniscal injury; high performance athletes, or military personnel/ manual workers suffer sports or job-related trauma; for most cases, such injuries bring a significant socio-economic cost, therefore treatments will not only benefit patients but also their carers, and also the NHS by reducing pressure through shorter hospital stays and faster rehabilitation; (iii) overcoming of known deficiencies with existing products (e.g. the loosening of metal compression screws); (iv) enhanced functionality for surgeons, with the potential for shorter theatre times and simplified procedures. Our clinicians are leaders in sports injuries (but also with for example, active service medical expertise and general trauma expertise) but we see the sports applications, with its extremes, as a potentially valuable 'accelerated' model of fixations for broader cases. In addition, there will be additional economic impact in reduced inventories and in emerging business through these new technologies.
The total annual estimated global healthcare market (2015) that could potentially be addressed using shape memory polymeric for orthopaedic soft tissue lesion repair is estimated to be around $1.2bn p.a., and small bone fracture fixation implants is around $2bn p.a. This market is expected to grow, driven by increased sports participation, and an aging demographic. Our programme will contribute to the UK position of strength in medical device technology and manufacturing, including a strong SME base - including our partners. We will engage with Regulatory bodies, including MHRA and BSI via our MeDe Innovation Centre, to help promote routes to assessing these new technologies. We will also achieve further academic impact, to help maintain a world-leading position for the UK in solid phase orientation processing of polymers research and precision micromoulding research in the Polymer IRC laboratories at Bradford, and continuing international visibility by the outputs from this research and the proposed Early Career Researcher exchanges with China, based on the UK-China advanced materials for healthcare community which we lead.