Discussion
chronic pain, pain
CHRONIC PAIN, SECONDARY
At four years after delivery, the STAR care pathway remained a cost-effective treatment to improve pain outcomes for people with chronic pain at three months after TKR. The point estimates of effect among those reporting pain outcomes at four years are consistent with findings at 12 months (BPI pain severity − 0.42 at four years versus − 0.65 at one year, BPI pain interference − 0.64 versus − 0.68 at one year), therefore any longer-term disbenefit from the care pathway can be ruled out.Cost savings in terms of NHS long stay admissions were £737 in the first year. Further costs savings of £339 between one year to four years after delivery suggest there are no bounce back effects on costs over the longer term. There are currently no other evidence-based treatment options for patients with chronic post-surgical pain after TKR. Implementation of the STAR care pathway presents a clinically important and cost-effective treatment option for those patients who will present with chronic post-surgical pain three months after TKR. We have since developed an e-learning training package and delivery toolkit to enable and support national implementation of the STAR care pathway in the NHS [The strength of evidence from the longer-term follow-up is limited by the lower response rates, with 86% (n = 313/363) of the randomised sample contributing data at one year and 67% (n = 226/337) of those enrolled at 12 months after randomisation contributing at four years. Our findings are therefore, based on two-thirds of the trial population. However, there were no substantial differences in measured baseline characteristics or utility values between participants who completed four-year follow-up questionnaires and those who did not. Any small differences between the two groups work against the intervention and have been adjusted for in the analysis. By four-year follow-up, it is over three years since most participants have had any form of intervention, and it is difficult to quantify the effects of any treatments subsequent to the STAR care pathway.Surgical trials often have routine follow-up that improves attrition rates. Loss to follow-up in orthopaedic trials has been estimated to be 15% at three years [Community based NHS care and personal expenses were not collected for this follow-up study. The recall bias resulting from the long recall period (median 3 years) needed to obtain this information would have called into question the validity of these data. Further, in the original trial we had shown that inpatient stays were the main NHS cost driver and hence this was our focus in the follow-up study. A limitation of the study is therefore that the long-term effect on community based NHS care and personal expenses is unknown. In the original study the main cost driver from the patient perspective was hours of unpaid leave which was in favour of the intervention arm, therefore the follow-up results are potentially conservative in nature.The higher number of inpatient admissions and their duration in the usual care arm continued in the longer-term follow-up. This translated into higher costs for the usual care arm and was the main source of the differences in costs between the treatment groups; QALYs remained higher in the intervention group compared to the conventional treatment group. Again, the results may have been influenced by the differential attrition rates between the trial arms, which would imply that the data were not missing at random. However, a sensitivity analysis which considered the likely biases, did not alter the original findings. From a secondary care NHS perspective, the conclusion that the intervention is the cost-effective option still holds within longer-term follow-up.