Evaluating the Effect of Diabetic Medications on Rates of Nonunion in Patients Undergoing Foot and Ankle Arthrodesis Treatments

Introduction/Purpose: Diabetes mellitus (DM) is known to negatively impact outcomes following surgical operations and increase the susceptibility of affected individuals to higher rates of nonunion, surgical site infection, ulceration, increased risk of amputation of the extremities, and various other perioperative complications. A number of in vitro studies suggest that the increase in undesired outcomes is largely secondary to the effects of diabetes-induced prolonged inflammation and advanced glycation end products (AGEs) on these patients' vascular systems and skeletal microarchitecture. However, there is a paucity of literature investigating the effects of blood glucose-regulating medications on the clinical outcomes of diabetic patients following fusion procedures. This study aims to determine the impact of commonly prescribed diabetic medications on bone health and bone healing following foot and ankle operations. Methods: A retrospective review was conducted of 114 diabetic patients undergoing ankle, hindfoot, or midfoot arthrodesis by one of two fellowship-trained foot and ankle orthopaedic surgeons from 2015-2022. Patients were identified by having undergone surgery via 27870, 27815, 27825, or 27835 CPT codes, as well as having been diagnosed with diabetes mellitus prior to or at time of surgery. Joints fused included the tibiotalar joint (n=45; 39.5%), subtalar joint (n=62; 54.4%), talonavicular joint (n=31; 27.2%), and calcaneocuboid (n=14; 12.3%). Data collected included demographics, medical history, diabetic medication, postoperative complications, readmission rates, and reoperation rates. 36 patient cases were noted to not have concurrent medications prescribed to control their diabetes, while the other 78 patient cases were concurrently prescribed either metformin (33 cases; 28.9%), insulin (19 cases; 16.7%), both metformin and insulin (18 cases; 15.8%), glipizides (11 cases; 9.6%), dulaglutides (7 cases; 6.1%), semaglutides (9 cases; 7.9%), and sitagliptins (8 cases; 7.0%). Results: The overall cohort was majority male (62.3%) with mean age 60.38 (range 31-76) years, mean BMI 34.00 (range 21.47- 61.38) kg/m2 and mean follow-up 1.90 (range .50-6.25) years. The cohort had a 27.2% superficial infection rate, 28.9% deep infection rate, 41.2% non-union rate, 47.4% reoperation rate, and a 14% 90-day readmission rate. Except for insulin-treated patients, who had significantly higher infection (insulin=45.9%, non-insulin=18.2%; p=.003) and deep infection rates (insulin=45.9%, non-insulin=18.2%; p=.003), there was no statistically significant difference in any outcomes by specific medication or any diabetic medication use. Patients with Charcot arthropathy (n=42) had significantly higher superficial infection (charcot=42.9%, non- Charcot=18.1%; p=.005), deep infection (Charcot=52.4%, non-Charcot=15.3%; p<.001), and 90-day readmission rates (Charcot=26.2%, non-Charcot=6.9%; p=.006). Conclusion: Our results indicate that patients on insulin or patients with Charcot arthropathy may be at increased risk of infection following foot and ankle fusion procedures. Other common medications to control diabetes mellitus were not found to increase risk of adverse outcomes. This finding is useful for surgeons and physicians attempting to optimize the clinical outcomes of diabetic patients undergoing the described procedures. However, further study with a greater sample size is necessary to confirm these findings.