Dive Brief:

• Cannabis use before orthopaedic surgery is associated with higher rates of complications and adverse events, according to three studies looking at thousands of insurance database entries presented at the annual meeting of the American Academy of Orthopaedic Surgeons (AAOS).
• With cannabis use rising quickly in U.S. adults aged 45 to 64 years, the studies sought to find out if marijuana consumption prior to knee and hips replacements affects outcomes. Rates of dislocation, lengths of hospital stay and other negative outcomes were higher in cannabis users. 
• One study author said the findings suggest surgeons may be able to reduce the risk of postoperative complications by talking to patients about the outcomes associated with cannabis use.

Dive Insight:

Use of cannabis in the age groups that undergo total knee and hip arthroplasties has increased as U.S. states have liberalized their laws on the drug. According to one of the studies presented at the AAOS annual meeting, cannabis use is up 48% in adults aged 45 to 54 years and 455% in adults aged 55 to 64 years.

Multiple groups of researchers are trying to figure out the implications of the trend for outcomes in patients who undergo surgery. Last month, a paper published in JACC: Cardiovascular Interventions showed marijuana use is associated with higher risks of cerebrovascular accident and bleeding, but a lower risk of acute kidney injury, after percutaneous coronary intervention. The analysis looked at a registry of 113,477 patients, 3,970 of whom reported marijuana use.  

Now, another set of studies have analyzed orthopaedic outcomes. One of the studies analyzed the outcomes of knee replacement patients in an insurance database. The researchers looked at almost 5,000 patients, evenly split between people who did and did not consume cannabis. The two groups were matched by age, sex, obesity, alcohol use and other variables that could affect outcomes. The frequency and quantity of cannabis consumption is unclear from the study report. 

Rates of cerebrovascular accidents, deep vein thromboses, hematomas, heart attacks and urinary tract infections were significantly higher in the cannabis group at 90 days but not at one year after the surgery. Readmissions were higher in the cannabis group at both time points. Other outcomes such as revision rates and opioid consumption were similar across the two groups.

The other two studies looked at outcomes in patients with cannabis use disorder, a term for people with “a problematic pattern of cannabis use leading to clinically significant impairment or distress.” One study analyzed a private database of 55,553 knee replacement patients, 9,260 of whom had the disorder. The analysis found the people in the cannabis cohort spent significantly longer in the hospital and were more likely to develop complications such as pneumonia and respiratory failure.

In the third study, an analysis of a private payer database of 44,154 hip replacement patients, 7,361 of whom had cannabis use disorder, found people with the condition spent longer in hospital and had higher rates of some of the same complications seen in the other analyses, such as pneumonia and respiratory failure.