The incidence rate of hand tendon injuries is 28 per 100,000 per annum. Flexor tendon injuries account for ~40% hand tendon injuries and many patients suffer from multiple tendon injuries. Flexor tendon injuries predominantly affect working-aged young males involving manual labour. Hand tendon injuries can be severely disabling, which requires a rehabilitation time of 12 weeks. On average, a single flexor tendon repair costs £1330, and its associated rehabilitation and societal costs due to absence from work are estimated to be around £15,000.
Some of these tendons in particular are very challenging to repair due to muscle contraction, which leads to the severed tendon end retracting further into the host tissue. At present, retrieving the severed proximal tendon is very difficult without damaging the surrounding structures, which often leads to adhesion formation and thus limited functional outcome. Tendon injuries are predominantly repaired with sutures; and there has been limited progress in tendon repair techniques. It has been shown that suture repairs lead to high stress areas on tendon tissue which cause cell death and scar formation. Flexor tendon repair remains an unmet need as only 75% repairs achieve a satisfactory functional result with an 11% reoperation rate.
During an 18-month grant (Mar 2019 to Aug 2020) from Arthritis Research UK, a rapid integrated tendon repair system (RITRS) was developed to obtain improved hand flexor tendon retrieval and repair. The RITRS is a class III medical device consisting of two components – Product 1 for tendon retrieval and Product 2 for tendon reattachment. It is worth noting that Product 1 can be used as a standalone class IIa device. Firstly, Product 1 is used to retrieve retracted tendon ends using endoscopic instruments, which minimises trauma created during retrieval surgical exposure and reduces the chance of adhesion formation (most common complication). Product 2 then rapidly reconnects the severed tendon ends with a more even stress distribution compared to suture repair, leading to improved tendon healing. RITRS is completely degradable, which leads to reduced repair bulkiness. A range of prototypes were developed and manufactured through 3D printing in multiple design iterations; and their preliminary proof-of-concept data were obtained through various in vitro assessments and in silico modelling. In addition, our research on market reports and patent data revealed that a significant and growing market for our product. This project will further translate our initial design created in the ARUK project and will also create next product designs to further increase the tendon product repair portfolio.
Main questions to be answered:
Prof Cartmell and Mr Jason Wong have been working on the improvement of tendon repair outcomes and has developed the RTIRS using additive manufacture approaches of polycaprolactone (PCL) designed for hand tendon injuries. This PhD project aims to optimise the design of RTIRS for application in hand tendon injuries and to create subsequent prototypes for use in other body area target applications other than the hand.
- How can the original RTIRS system be further optimised for application in hand tendon injuries?
- How can the original RTIRS system be adapted to other tendon injuries?
- What is the optimal design of RTIRS? This includes shape of the device and considerations on implantation/suturing in the tendon to minimise surgery invasiveness using additive manufacture techniques
- Does the RTIRS have the appropriate mechanical properties to sustain the forces generated within the tendon during the process of healing? Incorporation of a reinforcing material in PCL will be explored (e.g. graphene oxide) to enhance mechanical properties of the device and loaded versus unloaded mechanical tests will be performed to assess performance of the device in simulated in vivo loaded conditions
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