Shape memory bone and soft tissue fixations

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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 hybridroute - 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 scaphoidcompression screws and soft tissue fixations, including ACL and rotator cuff repair; b) input to designof fixation devices and c) help remove barriers to clinical adoption;Industry - evaluate a) market size, b) process economics, c) routes to market, d) device designsRegulatory - we will engage with MHRA and BSI via our MeDe Innovation Centre.