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With medical and recreational marijuana use becoming legal in more states each year, it would not be surprising for orthopaedic surgeons to have a correspondingly greater percentage of marijuana-dependent patients than in the past.

The question is, does marijuana use have any impact on outcomes of orthopaedic procedures?

A study from researchers at the University of Chicago suggests that the answer may be yes, at least for some patients. At the American College of Surgeons’ Clinical Congress 2022, the researchers presented data showing that in their study, marijuana-dependent patients who underwent shoulder or knee arthroscopy had a greater risk of postoperative infection.

Lack of Information

Although the effect of marijuana use has been studied in pain management and cardiovascular health, few studies have looked at the potential effects of marijuana use by patients who are undergoing surgery. More states are legalizing marijuana, and the size of the cannabis market is predicted to reach $91.5 billion by 2028. [1]

Given this trend, the University of Chicago researchers wanted to determine if marijuana-dependent users face an increased risk of complications following knee or shoulder arthroscopy.

“There’s so much information out there on smoking, alcohol, and other substances, but not on marijuana use,” said study coauthor Jason Strelzow, MD, assistant professor of orthopaedic surgery at the University of Chicago.

“As providers and surgeons, we should be discussing marijuana use with our patients, something that we have traditionally shied away from.”

Study Details 

The researchers’ goal was to retrospectively evaluate the risk of postoperative complications – deep vein thrombosis (DVT), pulmonary embolism (PE), and infection – in knee and shoulder arthroscopy patients who had reported marijuana dependence.

Using the PearlDiver national insurance claims database, the researchers first identified all knee and shoulder arthroscopy patients. Then, they identified all patients in those 2 surgical populations who had a diagnostic code for marijuana dependence.

Note that marijuana dependence is a rigid definition applied only when patients have 3 or more criteria for dependence, such as using marijuana longer than intended, difficulty in cutting down use, spending a lot of time in obtaining or recovering from marijuana, and high tolerance.

Finally, the researchers recorded the rates of DVTs, PEs, and infections within 90 days of surgery for all knee and shoulder arthroscopy patients.

Univariate analyses of marijuana dependence on all outcomes were performed, followed by a multivariate logistic regression analysis controlling for known patient comorbidities.

Key Findings 

Of the nearly 1.9 million knee and shoulder arthroscopy patients included in the study, more than 21,000 patients had a diagnostic code for marijuana dependence.

Within both surgical groups, the marijuana-dependent cohort experienced increased rates of infection and DVT, while the PE rate stayed the same.

• For the shoulder arthroscopy group, the rate of infection increased from 0.7% to 1.7%, the DVT rate from 0.2% to 0.4%, while the PE rate stayed at 0.2%.
• In the knee arthroscopy group, the rate of infection increased from 1.1% to 2.6%, the DVT rate rose from 0.2 to 0.3%, and the PE rate stayed at 0.3%.

In the multivariate analyses controlling for a variety of patient risk factors, including tobacco use or a history of diabetes, marijuana dependence was identified as an independent risk factor for infection within both cohorts (knee: odds ratio [OR] 1.85, P < 0.001; shoulder: OR 1.65, P < 0.001)

Future Research Opportunities 

“The higher infection rate found by this new study should raise a red flag for patients and providers and should be discussed along with other risk factors before an arthroscopic procedure,” said lead study author Sarah Bhattacharjee, MD, who conducted the research while she was a medical student at the University of Chicago. Dr. Bhattacharjee is now a surgical resident in orthopaedic and sports medicine at the University of Washington.

Dr. Strelzow agreed, noting that he hopes surgeons will use the study results to help inform marijuana-dependent patients about risks, benefits, and available alternatives, such as reducing or eliminating marijuana use 6 months prior to an arthroscopic procedure.

Although the study focused on minimally invasive surgery, Dr. Strelzow said that “we would expect similar or larger effects with more open or invasive procedures.”

The study has identified the need for additional research to better understand the relationship between marijuana dependence and postoperative complications. In addition, given that the study used very rigid criteria for marijuana dependence, there are opportunities for future clinical studies to investigate how various levels of marijuana use impact postoperative complications.

Sources

Bhattacharjee S, et al. Marijuana and joints: outcomes following shoulder and knee arthroscopy. Presented at the American College of Surgeons’ Clinical Congress 2022, October 16-20, San Diego, California.

Bhattacharjee S, Seidel H, Liu C, Liu AM, Strelzow J. Marijuana and joints: outcomes after shoulder and knee arthroscopy. J Am Coll Surg. 235(5):p S166, November 2022. doi: 10.1097/01.XCS.0000894268.26020.35

Reference

1. Legal Cannabis Market Size Worth $91.5 Billion By 2028 | CAGR: 26.3%. Grand View Research, Inc., press release, July 27, 2021. Accessed November 21, 2022.