AposHealth for knee osteoarthritis

The main clinical evidence includes 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 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 the clinical evidence section of the assessment report in the supporting documentation.

There is a lack of evidence comparing AposHealth with 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 do 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 crossover undermined the robustness of the results.

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

When AposHealth is compared with a control group, the differences in pain, function and stiffness measured by the WOMAC score are statistically significant and show better outcomes for the AposHealth group. But the EAG noted that it is uncertain whether the improvement shown in the RCT is clinically meaningful. The EAG also noted that the WOMAC scores reported in the studies were not all on the same scale and advised caution when comparing WOMAC scores between studies and interpreting the evidence. Clinical evidence from non-comparative studies shows a consistent improvement in pain, function and stiffness after using AposHealth when compared with baseline and measured by the WOMAC score.

Two non-comparative studies included by the EAG had knee replacement surgery as a primary outcome, and only 1 of the studies was based in the UK. The UK-based study reported that 84% of people (305 of 365) using AposHealth whose condition met the criteria for total knee replacement surgery referral did not progress to total knee replacement surgery at 2 years. The other (US-based) study reported that 86% of people (204 of 237) using AposHealth did not progress to total knee replacement surgery at 2 years.

There is some evidence that AposHealth may improve quality of life, with stronger evidence for improvement to physical aspects. The RCT found no difference between the active and control groups in SF‑36 scores. The prospective comparative study reported a significant difference in the physical component summary and total score of the SF‑36 questionnaire but reported no difference in the mental component summary. In non-comparative studies, SF‑36 scores from baseline to post-treatment follow up for AposHealth showed significant improvements in some sub-scores, but improvements varied between studies.

There is limited, low-quality evidence that AposHealth results in reduced standard care resource use. The RCT reported no difference in rates of analgesic use between the active and control groups, and the prospective comparative study reported that the control group used more rescue medication (647 tablets) than the active group (273 tablets). The company submission also included unpublished survey and audit data that suggested AposHealth resulted in a reduction in health resource use.

The company submitted a Markov decision model comparing standard care with and without 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 have 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 the economic evidence section of the assessment report in the supporting documentation.

Key clinical parameters in the company model are the rate of total knee replacement, subsequent total knee replacement on the other knee, postoperative complications and mortality. The EAG added a starting age of 68 years 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.

The EAG base case is that AposHealth is cost saving 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 the section on knee replacement surgery delay).

The company did a 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. Lower standard care costs before knee surgery are likely to lead to cost savings because fewer costs are accumulated by people who are delaying having surgery. The cost of standard care before total knee replacement is the only parameter that makes the one-way sensitivity analysis cost saving at 20 years. The EAG also emphasised the importance of the reduction to standard care costs because of AposHealth. The EAG reiterated the uncertainty about this evidence, as described in the section on standard care resource use.

The EAG considered an exploratory scenario for people who 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.