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Metformin—Wonder Drug for TKA Patients with Diabetes?

Elizabeth Hofheinz, M.P.H., M.Ed.

With type-2 diabetes on the rise, a team of researchers from Emory University in Atlanta set out to determine how the diabetes drug metformin might impact outcomes of total knee arthroplasty (TKA). Their retrospective cohort study, “Metformin Use Is Associated with Fewer Complications in Patients with Type-2 Diabetes Undergoing Total Knee Arthroplasty,” appears in the April 7, 2021 edition of The Journal of Bone and Joint Surgery.

Co-author Jacob M. Wilson, M.D., an orthopedic resident at Emory, told OSN: “Diabetes is known to negatively influence outcomes after total knee arthroplasty. We became interested in how this increased risk may be modifiable. Metformin has been extensively studied in the medical literature but has not previously been investigated in arthroplasty patients. Given that metformin is currently recommended for all patients with type II diabetes (except those with chronic kidney disease, where it is currently contraindicated), we felt it was important to determine the influence metformin may have on outcomes.”

Using the Truven MarketScan Commercial Claims and Encounters and Medicare Supplemental and Coordination of Benefits databases, the researchers identified adults who underwent primary unilateral TKA from 2009-2018 who were preoperatively diagnosed with type-2 diabetes. They analyzed 90-day outcomes and also did a subgroup analysis on 1-year revision rates. A total of 64,372 patients were included in the analysis—32,186 in the metformin group and the same in the no-metformin group.

“Outcomes and complication profiles following total knee arthroplasty have improved over the last few decades,” said Dr. Wilson to OSN. “However, high risk patient populations remain a challenge. Patients with diabetes are known to have higher risk. While metformin is indicated in the treatment of nearly all patients with type II diabetes, it is well documented that many of these patients are inappropriately not prescribed the medication. If metformin improves complication profiles in this group of patients, this is important information for orthopedic surgeons to be aware of as it should be incorporated into patient optimization protocols.”

Both the metformin cohort and the no-metformin cohort possessed similar baseline characteristics, with both having a mean patient age of 64 years and a composition of 58% female patients. Not only that, but the comorbidity burden was similar and the number of insulin-dependent patients and the number of patients taking other diabetic medications were both nearly identical in each group.

When the investigators controlled for baseline characteristics, they found that the odds of 90-day periprosthetic joint infection, deep vein thrombosis, and acute kidney injury were all increased in individuals who were not prescribed metformin.

Dr. Wilson: “We studied matched cohorts of patients with type II diabetes and found that those who were prescribed metformin had lower odds of prosthetic joint infection and revision surgery at 1-year. Patients on metformin were also found to have lower odds of readmission and early postoperative complications, including deep vein thrombosis.”

“Our study was retrospective in nature. Future work should be in the form of a prospective, randomized trial.”

Elizabeth Hofheinz

Two time winner of the MORE award Ms. Hofheinz was the first writer employed by Orthopedics This Week. The MORE award is granted annually by the American Academy of Orthopaedic Surgeons to recognize excellence in journalism. Ms. Hofheinz is currently the Director of Communications for Ortho Spine Partners (OSP).

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