Tirzepatide vs GLP-1s in spinal fusion

A retrospective study published in the European Spine Journal on 18 June 2026 compared pre-operative tirzepatide use against single-receptor GLP-1 agonists in obese patients undergoing spinal fusion. Across 918 propensity-matched pairs, tirzepatide users had fewer thrombotic events, fewer revision surgeries, and lower pseudarthrosis rates over two years of follow-up^[1].

What the study measured

The research team, led by Gregory Isaac Sacks, used the TriNetX Research Network, a federated database of de-identified electronic health records. They identified obese adults who filled either a tirzepatide prescription or a single-receptor GLP-1 agonist prescription (drugs such as semaglutide or liraglutide) in the 12 months before undergoing spinal fusion surgery^[1].

After propensity-score matching on age, sex, BMI, comorbidities, and surgical approach, 918 pairs remained for analysis. The design controlled for the most obvious confounders, but it is worth noting that the matching was done on coded variables in the database, not on granular clinical detail. The analysis then split outcomes into two windows: 90-day postoperative complications and two-year surgical durability^[1].

Early results at 90 days

Within the first 90 days after surgery, tirzepatide patients had a relative risk of 0.41 for thrombotic or embolic events compared with the single-receptor GLP-1 group. The difference was clinically meaningful: blood clots are among the most dangerous complications after spine surgery, particularly in obese patients who already carry elevated baseline risk^[1].

Urinary tract infections were also lower in the tirzepatide cohort (RR 0.47), and acute kidney injury occurred less often (RR 0.42). All three comparisons reached statistical significance. The pattern across multiple organ systems suggests a systemic difference in postoperative recovery rather than a coincidence in a single outcome measure^[1].

Long-term results at two years

At the two-year mark, the tirzepatide group needed fewer revision surgeries (RR 0.65) and experienced less post-laminectomy syndrome (RR 0.58). The most striking finding was the pseudarthrosis rate: a relative risk of 0.41, meaning tirzepatide users were less than half as likely to experience failed bone fusion compared with single-receptor GLP-1 users^[1].

The pseudarthrosis finding is consistent with an earlier propensity-matched analysis published in Clinical Spine Surgery in 2025. That study examined GLP-1 agonists as a class (not tirzepatide specifically) and found significantly lower pseudarthrosis rates after multilevel cervical fusion: 10.71% vs 17.61% for anterior procedures and 13.21% vs 22.28% for posterior procedures at six months^[2]. Taken together, the two studies suggest that incretin-class drugs may influence bone healing, though neither can establish a causal link.

What this study does not tell us

This was a retrospective database analysis, not a randomised controlled trial. The TriNetX network captures coded diagnoses and pharmacy fills, but it does not capture surgical technique details, bone graft type, fusion level, or whether patients actually took their medication as prescribed. Residual confounding is possible despite the propensity matching.

There is also no comparison with a non-GLP-1 control group. The study shows relative differences between two active drugs, not absolute benefit over no drug at all. Obese patients not taking any incretin medication might do worse, better, or the same as either group. We cannot tell from this data.

The mechanism behind tirzepatide's apparent advantage is not established. The authors propose that GIP receptor activation (the feature that distinguishes tirzepatide as a dual agonist from single-receptor GLP-1 drugs) may contribute additional anti-inflammatory or bone-metabolism effects. Animal studies have linked GIP signalling to osteoblast activity and bone formation. But that hypothesis has not been tested in a surgical population through a controlled trial^[1].

Why this matters for patients on incretin drugs

The number of patients arriving for elective surgery while taking a GLP-1 or dual-agonist medication is rising fast. As prescriptions for semaglutide and tirzepatide grow, surgeons and anaesthesiologists are encountering these patients more often. Existing surgical guidelines already address pre-operative fasting concerns with GLP-1 drugs (delayed gastric emptying raises aspiration risk during anaesthesia). This study adds a different question: whether the choice of incretin drug itself might influence surgical recovery.

For patients currently on tirzepatide or a single-receptor GLP-1 agonist who are considering spine surgery, the practical takeaway is limited. One retrospective study is not enough to change prescribing decisions. It is, however, enough to raise the question with your surgical team, especially regarding perioperative medication management. Anyone weighing surgical timing and medication choices should consult their prescribing clinician.