A new study has shown that a smartphone app improved pain control and reduced opiate painkiller use in patients who used the app after total knee replacement surgery.

The study is being presented at the meeting 'Euroanaesthesia' (the annual meeting of the European Society of Anaesthesiology) in Vienna, Austria (1-3 June). The more the study participants used the app, the more likely they were to lower pain scores and decrease their use of opioids.

"These are important findings given the current demands on the healthcare system and the growing misuse of prescription painkillers worldwide", said author Dr Amar Sheombar from Kliniek ViaSana in the Netherlands.

"Few clinically-tested mobile apps exist with clear measurable goals to guide patients in pain control and opiate use at home after surgery," Sheombar added.

To investigate the effect of the app on pain and opiate use, Dutch researchers randomly assigned 71 patients (aged 56-70 years) undergoing total knee replacement the app and usual care (38 patients) or usual care alone (33) in the first two weeks at home after surgery.

The mobile app allows patients to input their pain level (no pain, bearable pain, unbearable pain, or untenable pain)--based on this information and the number of days after surgery, the app offers advice on drug pain relief use and exercises or rest. Questionnaires were used to establish opiate use (oxycodone) and pain levels at rest, during activity, and at night, as well as other pain drug use, experiences with exercises, pain acceptance, function, and quality of life. Participants completed questionnaires preoperatively, daily during the first two weeks, and after one month.

Amount of app use was also recorded, with 'active use' defined as at least 12 uses of the app over two weeks. During the study, average Visual Analogue Scale (VAS) pain score was 23 (the scale is 0 to 100 where 100 represents the highest pain) and average opiate use across the group was less than half (0.4) of one 5mg oxycodone tablet per day.

Compared to the control group, users of the app used 23 per cent less opiates and 15 per cent more paracetamol in the first two weeks following surgery. Regular (active) use of the app led to a further reduction in opiate use and improved pain control during activity and at night.

Regular app users (19 patients) reported four times faster reduction in pain during activity, six times faster reduction in pain at night, and 44 per cent less opiate and 76 per cent less gabapentin use (taken to relieve nerve pain) compared to controls. Opiate use was substituted by 21 per cent more paracetamol use in regular app users.

"Knowing that 80 per cent of interactive advice is remembered may explain why regular use of the app contributes to lower pain scores and reduced opiate use", said Dr Sheombar.