Advice
The technology
The technology
The STAK (self-treatment assisted knee flexion) tool (Orthopaedics Ltd) is a high-intensity medical stretching device for use in hospital or in the community. It is used to treat and prevent knee stiffness (arthrofibrosis) in people who have had knee trauma or surgery, such as knee replacement. It can be used daily at home or in hospital.
Arthrofibrosis sometimes happens after knee trauma or surgery as a result of an exaggerated inflammatory response, leading to the formation of dense scar tissue. The STAK tool enables a person to generate (using their own body weight) the high-intensity stretch needed to break down scar tissue, and to control and finely adjust the intensity of any stretch.
The device consists of an adjustable footplate that is placed on the ground and secured to a foot of the chair. While seated in a chair, the person places their foot into the STAK tool, which is set to the limit of their current knee flexion ability. They then apply force using their body weight and leverage to stretch the knee to the limit of their pain threshold at their end range of movement.
The STAK tool can be used independently at home so individuals are engaged and in control of their treatment. A programme is also provided that uses telephone calls, texts or Skype. This reduces the need for face-to-face physiotherapy appointments.
Innovations
The company claims the STAK tool is the only stretching device that uses the individual's own leverage and gravity to achieve higher increases in the range of movement in their knee.
Current care pathway
There is currently no NICE guidance on knee arthrofibrosis.
The NHS overview on knee replacement notes that surgery is usually needed when the knee joint is worn or damaged so that mobility is reduced, and there is pain even while resting. The most common reason for knee replacement surgery is osteoarthritis. Complications are rare but can include stiffness of the knee (arthrofibrosis).
NHS University Hospitals of Leicester self-treatment assisted knee flexion tool states that revision surgery for arthrofibrosis is both expensive for the NHS and traumatic for the patient. However, the alternatives are limited. Manipulation can be done, but this requires general anaesthetic, is not always successful and has risks attached to it. Improved range of movement has been noted from using continuous passive motion, but these devices are typically expensive and cumbersome, and need clinic appointments for treatment by trained staff.
NICE's guideline on joint replacement (primary): hip, knee and shoulder has been identified as relevant to this care pathway, in particular the section on postoperative rehabilitation.
Population, setting and intended user
The technology would be used by people who have had knee trauma or replacement and subsequently have knee stiffness.
Stiffness after total knee arthroplasty, defined as limited range of movement that affects activities of daily living, is a common problem happening in 5% to 30% of people.
In 2019, 103,617 partial knee replacements were done in the UK (National Joint Registry, 17th Annual Report 2020).
US data suggest that arthrofibrosis is responsible for the majority (28%) of hospital readmissions after total knee replacement.
Costs
Technology costs
The technology costs £250 (excluding VAT), including a supporting chair. The device is reusable.
Costs of standard care
Currently people would expect to get information before discharge about self-directed recovery exercises and physiotherapy, and face-to-face physiotherapy from the NHS on a more ad-hoc basis.
The company estimates that on average people would have 8 physiotherapy sessions from the NHS at a cost of £55 per group session. The more expensive one-to-one physiotherapy sessions at £64 are done on an ad-hoc basis (Personal Social Services Research Unit, 2020). Alternatively, an hour of staff costs for a mid-point band 5 physiotherapist is around £20 and a mid-point band 6 physiotherapist is around £25.
Resource consequences
The technology is not currently used in the NHS outside of research.
The company estimates that the technology could save the NHS around £11.7 million a year. This estimate is based on 30,671 people having treatment every year for arthrofibrosis using the STAK tool.
Most of the estimated savings, £7.36 million, arise from reducing the number of physiotherapy sessions from 8 to 3, and a further £5.27 million of savings by reducing numbers of people requiring manipulation under anaesthetic (estimated to cost £4,317) from 5% to 1%. The company assumes 20 STAK tools will be needed at each of the 168 NHS hospitals that carry out total knee operations in the UK. There is no published evidence to support these claims.
The company provided a manuscript of an unpublished economic evaluation of the STAK tool, using data from Aspinall et al. (2020). This reports that the STAK tool has a 96% probability of being cost effective based on a quality-adjusted life year (QALY) threshold of £20,000 to £30,000, and an incremental cost-effectiveness ratio of about £1,200 per QALY gained.
The STAK tool is expected to have a minimum lifespan of 10 years and is reusable. Training is provided at initial adoption and it is not expected that further training will be needed, but it is available on request at no cost. The remote monitoring, treatment and support through Skype and Zoom can be provided by the treating physiotherapist.
The company claims that the STAK tool could be easily incorporated into the physiotherapy pathway identified by the NICE guideline on joint replacement (primary): hip, knee and shoulder.