A systematic review of pain outcomes reported by randomised trials of hip and knee arthroplasty

It is difficult to pool results from randomised clinical trials that report different outcomes. We want to develop a core set of pain-related outcomes after total hip or knee arthroplasty, the first stage of which is to systematically review published outcomes. We searched PubMed, Embase and CENTRAL for relevant trials to January 2020. We identified 165 outcomes from 565 trials with 50,668 participants, which we categorised into six domains: pain; analgesic consumption; quality of care; adverse events; mobility; and patient-reported outcome measures. The outcome in each domain reported by most trials was: visual analogue score for pain, 401 (71%); morphine consumption, 212 (38%); length of hospital stay, 166 (29%); nausea or vomiting, 425 (75%); range of motion, 173 (31%); and patient satisfaction score, 181 (32%). A primary outcome was reported in 281 (50%) trials: 101 (18%) trials reported consumption of rescue analgesics and 95 (17%) trials reported pain. We plan to publish a consensus on outcomes that should be reported in postoperative pain trials after hip or knee arthroplasty.

Evolution of bias and sample size in postoperative pain management trials after hip and knee arthroplasty

BACKGROUND

Bias (systematic error) and small trial sample size (random error) may induce imprecise and exaggerated treatment effects in randomised controlled trials (RCTs). To avoid this, SPIRIT- and CONSORT-guidelines, and Cochrane Collaboration bias recommendations were developed. We investigated risk of bias and trial sample size development over time in postoperative pain trials.

METHODS

This study was based on data from two systematic reviews regarding pain management after total hip arthroplasty (THA) or total knee arthroplasty (TKA). RCTs of analgesic interventions with a comparator control group were included. Primary outcomes were risk of bias and trial sample size developments over time. We calculated cumulated bias scores ranging from 0 to 14 based on Cochrane's seven bias domains (0 = low; 1 = unclear, 2 = high). Developments were evaluated with run and control charts. Further, we compared data from trials published between 1990-1999 and 2010-2016.

RESULTS

We included 171 trials published between 1989 and 2016. Overall, the summarised risk of bias decreased, mainly due to better randomization and allocation concealment. Visual inspection suggested an on-going improvement that started around 2007. Trial sample size did not change significantly. For trials published between 1990-1999 and 2010-2016 adequate reporting increased from 36% to 75% for random sequence generation, from 9% to 38% for allocation concealment and from 27% to 52% for blinding of participants/personnel.

CONCLUSION

Risk of bias for RCTs regarding postoperative pain management after THA and TKA has decreased from 2007 to 2016, mainly due to better randomization and allocation concealment. Deficiencies remain. Thus, reporting according to validated guidelines is essential. Sample sizes did not change significantly.

Low degree of satisfactory individual pain relief in post-operative pain trials

BACKGROUND

The majority of clinical trials regarding post-operative pain treatment focuses on the average analgesic efficacy, rather than on efficacy in individual patients. It has been argued, that in acute pain trials, the underlying distributions are often skewed, which makes the average unfit as the only way to measure efficacy. Consequently, dichotomised, individual responder analyses using a predefined 'favourable' response, e.g. Visual Analogue Scale (VAS) pain scores ≤ 30, have recently been suggested as a more clinical relevant outcome.

METHODS

We re-analysed data from 16 randomised controlled trials of post-operative pain treatment and from meta-analyses of a systematic review regarding hip arthroplasty. The predefined success criterion was that at least 80% of patients in active treatment groups should obtain VAS < 30 at 6 and 24 h post-operatively.

RESULTS

In the analysis of data from the randomised controlled trials, we found that at 6 h post-operatively, 50% (95% CI: 31-69) of patients allocated to active treatment reached the success criterion for pain at rest and 14% (95% CI: 5-34) for pain during mobilisation. At 24 h post-operatively, 60% (95% CI: 38-78) of patients allocated to active treatment reached the success criterion for pain at rest, and 15% (95% CI: 5-36) for pain during mobilisation. Similar results were found for trials from the meta-analyses.

CONCLUSION

Our results indicate that for conventional, explanatory trials of post-operative pain, individual patient's achievement of a favourable response to analgesic treatment is rather low. Future pragmatic clinical trials should focus on both average pain levels and individual responder analyses in order to promote effective pain treatment at the individually patient level.