AposHealth for knee osteoarthritis

Summary of the evidence

3.1 The main clinical evidence comprises 29 publications (15 full-text papers, 9 abstracts associated with the included full texts, and 5 additional abstracts) covering a total of 19 unique studies. The full-text papers comprise 1 randomised controlled trial (RCT), 1 prospective comparative study with a 2-year follow-up study and 12 non-comparative studies. Drew et al. (2022) reported clinical information from a comparative group at baseline only, so the study was treated as a single-arm observational study and the results were extracted from the AposHealth arm only. The full-text publications include a total of 3,767 people. For full details of the clinical evidence, see section 4 of the assessment report in the supporting documentation.

Comparative evidence

3.2 There is a lack of evidence comparing AposHealth to non-surgical standard care treatments. The EAG acknowledged that this may be driven by uncertainties in the care pathway making it difficult to design and conduct comparative studies. Both the RCT and prospective comparative study with a 2-year follow-up study compared AposHealth with a sham device. The EAG considered the RCT to be of high quality with a low risk of bias. The prospective comparative study allowed people to cross over between the groups after 8 weeks. The EAG stated that the unclear description of this cross over undermined the robustness of the results.

Observational evidence

3.3 The other 12 studies are observational and are at a high risk of bias. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores, SF-36 questionnaire results, and gait outcomes were frequently reported and the EAG acknowledged that the outcomes reported across the studies were consistent.

Outcomes

Company base case

3.8 The company's model finds AposHealth cost saving compared with non-surgical standard care at 5 and 10 years. The company submitted a Markov decision model comparing standard care with standard care with AposHealth. The model is based on movement of people from standard care (with or without AposHealth) to total knee replacement surgery, and then to total knee replacement surgery of the other knee. The model results were originally reported at a 2-year and 5-year time horizon. However, after queries from the EAG, the company submitted an additional model with an extended 10-year time horizon. The company model assumes that all people will receive 2 follow ups per year in years 2 to 5, and 1 follow up in years 5 to 10. The company's base case showed a cost saving of £1,886 at 5 years, and £247 at 10 years. For full details of the cost evidence, see section 9 of the assessment report in the supporting documentation.

Clinical and cost parameters

3.9 The company's model structure is considered appropriate, but the EAG made changes to certain parameters in the model. Key clinical parameters in the company model are the rate of total knee replacement, subsequent total knee replacement on the other knee, post-operative complications and mortality. The EAG added a starting age of 68 to the model based on data from the National Joint Registry annual report (2021). The company model assumes the rate of subsequent total knee replacement on the other knee as 0.5% per month, and the rate of total knee replacement revisions as 0.34% per month. The EAG's model includes a slightly lower rate of 0.395% for total knee replacement on the other knee, using the value from Sanders (2017). It also included a lower rate of 0.32% per month for total knee replacement revisions from an alternate data source and added a variable mortality rate as the cohort passes through the model. Total knee replacement costs in the company model are taken from NHS best practice tariffs. But the EAG used alternative NHS Reference Cost data from 2019 to 2020 (to avoid the impact of COVID-19) and inflated to 2022 to 2023.

EAG base case

3.10 The EAG and company models have some differences but have similar findings at 5 and 10 years. The EAG base case is cost saving for AposHealth compared with standard care by £1,958 per person at 5 years, and cost incurring by £46 per person at 10 years. The EAG extended the model further and reported that AposHealth is also cost incurring by £2,032 at 20 years. The EAG noted that cost savings primarily come from a reduction in total knee replacement and reduced subsequent complications and follow up. So, the EAG felt that the model results should be treated with caution because existing evidence for delay to surgery is limited, as described in the clinical evidence, see section 3.5.

Sensitivity analysis and additional scenarios

3.11 The cost of standard care, and reduction in standard care because of AposHealth are key cost drivers in the model. The company carried out deterministic sensitivity analysis with one-way and two-way tables for key parameters, which were varied by 20%. The EAG repeated this with the amended model and extended it to 20 years. The cost of standard care uses parameter variations based on lower costs from Cole (2022) and a 20% increase from the base case input. This results in the cost of standard care before total knee replacement being the only parameter that makes the sensitivity analysis cost saving at 20 years. The EAG emphasised the importance of standard care costs, and the reduction to these costs because of AposHealth. The EAG reiterated the uncertainty around this evidence as described in section 3.7.

3.12 AposHealth may be cost saving for people who do not want or cannot have knee surgery if standard care costs are reduced by 20%. The EAG considered a scenario for people who do not want or are unable to have total knee replacement by setting movement of people having surgery in the model to 0%. With the assumption of a 15% reduction in standard care costs, AposHealth is cost incurring by £538 at 5 years and £40 at 20 years. But, if there is a 20% reduction in standard care costs, AposHealth becomes cost saving by £259 at 5 years and £701 at 20 years.