Study design: Retrospective cohort.
Objective: To examine metformin use on postoperative outcomes amongst patients with diabetes undergoing lumbar fusion.
Summary of background: Several animal studies have demonstrated that metformin, a first-line treatment for type 2 diabetes (T2DM), can attenuate neuropathic pain via decreased activation of microglia and suppression of inflammatory signaling.
Methods: Adult diabetic patients who underwent a 1-2-level posterior lumbar decompression and fusion (PLDF) (2017-2023) were identified and demographics, surgical data, metformin use/dosage, opioid consumption and patient-reported outcome measures (PROMs) collected. Statistical analysis was performed with alpha set at 0.05.
Results: Of the 299 diabetic patients who underwent a 1-2 level PLDF, 203 (67.9%) were taking metformin. There were no differences in morphine milligram equivalents (MMEs) in the 30 days prior to or the 30 days after surgery between groups. Patients on metformin had a lower Elixhauser (2.26 ± 1.48 vs. 2.79 ± 1.71; P=0.005), lower HgbA1c (7.15± 1.12 vs. 7.48± 1.59; p = 0.018), and fewer females (59.4% versus 42.4%, P= 0.009) but were otherwise demographically/surgically similar. Despite both groups having similar preoperative opioid use, metformin use was associated with lower MMEs at 30-90 days (31.8 ± 60.4 vs. 52.0 ± 92.0; P=0.018 and 90-365 days (65.0 ± 183 vs. 129 ± 292 MME; P=0.001), and greater improvement from pre- to postoperative PCS at 6 months (5.12 ± 8.96 vs -1.34 ± 8.57, P=0.048) and at 1-year (4.96 ± 9.47 vs. -1.87 ± 7.55, P = 0.027). Linear regression analysis identified metformin use as independently predictive of fewer postoperative MMEs 30-90 days postoperatively (Estimate -16.03, CI -31.51 to -0.56; P=0.043).
Conclusions: Metformin use was found to be independently associated with fewer MME requirements 30 days after surgery.
Keywords: Metformin; PLDF; PROMs; diabetes; opioid consumption.
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