Total knee replacement is a major and painful orthopaedic (joint and bone) surgery where the knee joint is replaced with an artificial joint. It is an effective and successful procedure to treat severe knee arthritis and reduce pain, but many patients report intense pain after the surgery. Postoperative pain control is predominated by opioids (morphine-based drugs). While opioids are effective to manage the pain, they can have acute and chronic complications, including confusion, nausea, vomiting, constipation and high risk of addiction. Medical cannabis is an effective and safe alternative for pain treatment. Recent studies showed that patients have reported a reduction in opioid usage when taking cannabis as a substitute for pain relief. This study aims to investigate whether adding medical cannabis (cannabidiol - CBD) treatment will decrease the amount of opiates needed in the first 2 weeks after knee replacement compared to a group given placebo.
COPE (Cannabinoids to Obviate Pain Experiment after knee replacement) will be a single-centre, prospective, randomized, placebo-controlled, superiority trial, with two parallel groups designed to investigate the effect of cannabis as postoperative pain treatment compared to placebo on total opioid consumption after total knee replacement. Eligible patients are: men and non-pregnant women aged ≥18 years scheduled to undergo primary total knee replacement. and with no opioid usage within the last 3 months or history of narcotic abuse. Patients will be recruited at the department of orthopaedic surgery at St Michael's Hospital (Toronto - Canada), and informed consent will be obtained from those eligible. Central computer-generated randomization will be used to randomly assign participants to cannabis or placebo groups (1:1 ratio). Only the study pharmacist will know allocated treatments.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
TRIPLE
Enrollment
220
Postoperative pain treatment
Placebo comparator
St. Michael's Hospital
Toronto, Ontario, Canada
Opioid consumption
Assess cumulative opioid consumption (morphine equivalent dose) by means of drug reconciliation (medication diaries and pill counts) i.e. patients will self report how many opioid pills they took each day, by means of the medication diaries and at 4 weeks follow up will bring the pills back to clinic appointment.
Time frame: 2 weeks after total knee replacement
Visual Analog Pain Scale
Assess pain from a visual scale that ranges from 0 to 10. Straight line with the endpoints defining extreme limits such as 'no pain at all' (zero) and 'pain as bad as it could be' (ten)
Time frame: Pain scale will be assessed at 24 hours, 2, 6 and 12 weeks after knee replacement
Oxford knee score
A short questionnaire consists of 12 questions ranging from 0 to 48 points, designed to assess function and pain after knee replacement surgery. Higher values represent a better outcome. Scores between 40-48 indicate satisfactory joint function
Time frame: Questionnaire will be completed by patients at 6 weeks after knee replacement
Health status and quality of life
EQ-5D is a questionnaire where patients self-rate their level of severity of health status and health-related quality of life. Consists of 5 dimensions (mobility, self care, usual activities, pain/discomfort, anxiety/depression) and each one of them has 5 levels (no problems, slight problems, moderate problems, severe problems, and extreme problems) where patients will indicate how they feel regarding their health status and quality of life.
Time frame: Questionnaire will be completed by patients at 6 weeks after knee replacement
Quality of recovery - 15 (QoR-15)
Quality of recovery scores are patient-reported outcome measures evaluating recovery after surgery regarding the last 24h. It is a short-form score with 15 questions that assess the 5 dimensions (pain, physical comfort, physical independence, physiological support and emotional state) and has 2 parts (A and B). Part A scores from 0 \[poor\] to 10 \[excellent\] - as higher is the score as better is the recovery. Part B scores from 10 \[excellent\] to 0 \[poor\] - as higher is the score as better is the recovery.
Time frame: Questionnaire will be completed by patients at 12 weeks after knee replacement
Self-reported opioid use and urinalysis
Patients will self report whether they are still using opioids (yes or no) and they will undergo a urinalysis (urine test). Patients will pee in a designed cup and a trained assessed will test the urine (with chemical strip) to detect the presence of one or more opioids in urine.
Time frame: The test will be completed at 12 weeks after knee replacement
Narcotic monitoring prescription
Using data from the Narcotics Monitoring System from ICES (Institute for Clinical Evaluative Sciences) which already captures all opioid prescriptions dispensed in retail pharmacies across Ontario, the investigators will assess if participants have had any filled prescription after knee replacement and record the number of prescriptions filled.
Time frame: Will be assessed at 12 months after knee replacement
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