APEX study

The APEX study was comprised of two randomised controlled trials.

Between 2009 and 2013, 322 patients waiting for total hip replacement and 316 waiting for total knee replacement took part in a single-centre, double-blind randomised controlled trial.

Participants were randomly assigned to receive local anaesthetic infiltration and usual care or usual care only. The primary outcome in the trials was pain severity (measured using the ‘WOMAC’ Pain Scale) at 12 months after surgery.

In the trial including patients undergoing total knee replacement, there was no strong evidence that the intervention reduced pain, but in the trial for patients undergoing total hip replacement, those patients who received the intervention had less pain at 12 months post-operative than patients who received usual care.

We concluded from the APEX trials that routine use of infiltration could be beneficial in improving long-term pain relief for some patients after total hip replacement.

Main findings from the trials:

The effect of local anaesthetic wound infiltration on chronic pain after lower limb joint replacement:  A protocol for a double-blind randomised controlled triaBMC Musculoskeletal Disorders, 2011; 12:53

Using resource use logs to reduce the amount of missing data in economic evaluations alongside trials Value in Health, 2013; 16(1):195-201

Discussion and qualitative evaluation of internal peer-review to train nurses recruiting to a randomised controlled trial – internal peer-review for recruitment training in trials (InterPReTiT) Journal of Advanced Nursing; 2014, 70(4): 777-790

Effect of local anaesthetic infiltration on chronic postsurgical pain after total hip and knee replacement: the APEX randomised controlled trials  Pain, 2015; 156:1161-1170 

Pre-operative widespread pain sensitisation and chronic pain after hip and knee replacement: a cohort analysis. Pain, 2015; 156(1): 47-54.

Local anaesthetic wound infiltration in addition to standard anaesthetic regimen in total hip and knee replacement: Long-term cost-effectiveness analyses alongside the APEX randomised controlled trials. BMC Medicine, 2015; 13:151

Rest pain and movement-evoked pain as unique constructs in hip and knee replacements  Arthritis Care & Research, 2016; 68(2):237-45

Central sensitization as a determinant of patients' benefit from total hip and knee replacement European Journal of Pain, 2017; 21(2):357-65

A unified multi-level model approach to assessing patient responsiveness including; return to normal, minimally important differences and minimal clinically important improvement for patient reported outcome measures BMJ Open, 2017; 7(7):e014041

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