Impact of Marijuana Usage on Nerve Transfer Outcomes

Introduction: For many patients with peripheral nerve injuries, marijuana can prove subjectively useful for pain management. However, to date, there are no studies investigating the impact of marijuana usage on nerve transfer outcomes.

Methods: The records of patients ≥18 years of age who underwent either radial-to-axillary nerve transfer or Oberlin transfer from a single institution were retrospectively reviewed, from 2014-2023. Demographic data, surgical characteristics, injury characteristics, nicotine use, alcohol use, marijuana use, and Medical Research Council (MRC) strength scores from preoperative evaluation to 24-months post-operation were collected. Functional strength was defined as ≥3/5 strength. Notable improvement was defined as a ≥2 point increase in MRC scores. Chi-squared tests and ANOVA were used for statistical analysis.

Results: Sixty-seven patients were included; 60 males, with the mean age at surgery of 43.3±17.3 years. Thirty-eight patients underwent radial-to-axillary nerve transfer, and 29 underwent Oberlin transfer. When analyzing for marijuana use, there were no significant differences in the proportion of patients with functional strength at 6, 12, 18, or 24 months postoperatively, or patients with notable improvement in the 6- and 24-month follow-up interval and preoperative and 24-month follow-up interval. Similarly, no significant associations were found when analyzing for alcohol or nicotine use, and no significant associations were found when controlling for type of surgery. Those that experienced notable improvement in the 6- and 24-month follow-up interval as well as the preoperative and 24-month interval were significantly younger than those that did not improve (38.8±15.0 vs 47.9±18.5 years, p=0.03; 40.5±16.2 vs 59.0±15.8 years, p=0.001). Patients with functional strength at 24-months post-operative experienced a significantly shorter interval between injury and surgery compared to those that did not have return of functional strength (0.7±0.3 vs 1.7±2.5 years, p=0.01).

Conclusion : In this cohort, marijuana, alcohol, or nicotine use did not influence nerve transfer outcomes. Notable improvement was significantly associated with younger age, and return of functional strength was significantly associated with shorter time until surgery. Larger cohorts will be beneficial to further establish the relationship between marijuana use and nerve transfer outcomes.