We’re bringing hope to arthritis sufferers
Our researchers are working to transform surgery and rehabilitation success rates for arthritis sufferers.
Drawing on aerospace engineering expertise, they are using a novel combination of motion capture and imaging techniques to create a computer model that will improve the outcome of finger joint replacement operations.
Osteoarthritis, a painful condition usually caused by wear and tear in the joints, can have a devastating impact on people’s quality of life and carries significant societal and economic costs. Nearly three quarters of people with osteoarthritis report constant pain, while one third retire early, give up work or reduce their working hours because of the condition.*
One solution for osteoarthritis sufferers is surgery to replace affected joints, but while operations such as hip and knee replacements have high success rates, this isn’t the case for finger joint replacements. In fact, a Southampton study looking at the outcome of surgery to replace the proximal interphalangeal (PIP) finger joint found that around a third of operations were unsuccessful. While surgery usually reduced pain, there was often no improvement in the range of movement, or the new joints tended to stiffen, dislocate or wear out.
One reason for this is a lack of detailed information about the complex dynamics of the PIP joint. Dr Alex Forrester, Associate Professor in Computational Engineering, explains: “When a surgeon cuts away some of the finger bone to put in a new joint, the position, size and angle all have to be correct for the soft tissue and ligaments to work properly around it.”
However, to date the key factors for success haven’t been identified, and this is what Alex, working as part of a multidisciplinary team, aims to find out. By developing a sophisticated computer model that maps the internal geometry of the joint, the team will be able to determine how variations in the location of a replacement joint could affect the outcome of surgery. The model could also inform the design of replacement finger joints and targeted rehabilitation protocols to rebuild strength and recover function.
Motion capture and imaging technology
To create the model, the researchers used an innovative combination of motion capture and imaging technology to collect data about the hands of 10 arthritis-free people.
“We fixed reflective markers to the skin of our subjects’ hands and filmed them with a range of cameras as they went through a set of movements,” says Alex. “By tracking and triangulating the position of the markers in 3D space, we could build a computerised video representation of the movement of their hands.”
The next challenge was to determine how the internal structure of the finger related to these markers. With the markers still in place, the subjects’ hands were scanned performing the same sets of movements using CT (computed tomography) and MR (magnetic resonance) imaging, producing a picture of the relative positions of the bone and soft tissue beneath the skin.
This combination of techniques is enabling the researchers to understand how the skin and soft tissue move around the bones – something that was previously only possible using the intrusive and painful method of inserting pins directly into bones.
Simulating surgical outcomes
It’s an approach that has the potential to transform the effectiveness of finger joint replacement surgery. “The computer model can be adjusted to simulate the effects of osteoarthritis on the PIP joint and to show what would happen if the joint was replaced,” says Alex.
“The idea is that a surgeon could see what might happen in the patient if they performed the procedure based on predictions from the computer model. In future it’s possible that individual patients could have their joints scanned to produce a 3D-printed replacement joint tailored to their anatomy.”
The technique could also be applied to other joints in the body to achieve the sorts of success rates that are currently seen in knee and hip replacement surgery.
Aerospace expertise
Alex’s contribution to the project draws on his experience in aerospace engineering. Having previously worked on wing aerodynamics, gas turbine, satellite and Formula One car design, he became interested in musculoskeletal conditions when his wife was diagnosed with rheumatoid arthritis.
“The way the finger joint works – and the effectiveness of a replacement – is very much down to geometry and the shape of the joint,” he explains. “Aerospace engineers use shape design to optimise the efficiency of aerodynamic surfaces; we’re using the same techniques to represent and manipulate the shapes of the articulating surfaces of the joint.
“Rolls-Royce doesn’t run experiments when it builds jet engines – it uses computer simulations that are accurate enough to ensure that when the engine is built it works. We’re not quite at that stage with humans, but the idea is that we’ll be able to simulate what will happen in surgery, leading to higher success rates.”
Joining forces across disciplines
The University’s culture of collegiality has been critical in facilitating this research, enabling Alex to work with experts at the Southampton Musculoskeletal Research Unit, including hand surgeon Professor David Warwick, bioengineer Dr Alex Dickinson, biomechanics specialist Dr Cheryl Metcalf, and Dr Leonard King, a radiologist at University Hospital Southampton (UHS). Alex says: “We meet regularly to discuss musculoskeletal disorders and how we can collaborate to find solutions. There’s a real desire among specialists in this area to work together to take research in healthcare forward.”
Access to the MR imaging research facility based at UHS has also been crucial to the study, as has the support of lead for MRI physics Dr Angela Darekar and MR research radiographer Chris Everitt. Without this resource and expertise to develop the non-standard MR imaging protocol, considerable up-front funding would have been needed to get the project to this stage.
Initially supported by an Engineering and Physical Sciences Research Council doctoral prize, the team is now seeking further funding to continue its work. Alex comments: “We’re in a position where we have really promising models and a great multidisciplinary team; the next step is to validate our findings before applying what we have learned to patients.”
Osteoarthritis – the human and societal costs
- Osteoarthritis affects more than 8 million people in the UK*
- 6 per cent of over 45s – over 1.5 million people in total – have sought treatment for arthritis in the hand or wrist
- Osteoarthritis in the hands is more common among women* – it currently affects around 620,000 working-age women
- 30.8m working days were lost in the UK in 2016 due to musculoskeletal problems*
*State of Musculoskeletal Health 2017, Arthritis Research UK
https://www.arthritisresearchuk.org/arthritis-information/data-and-statistics/state-of-musculoskeletal-health.aspx