Effect of Hemoglobin A1c on union rates in foot and ankle surgery

Diabetes Mellitus is associated with impaired osseous healing following foot and ankle surgery. Although hemoglobin A1c is commonly used to assess surgical risk, its relationship with postoperative union remains unclear.

We performed a retrospective review of consecutive diabetic patients who underwent foot and ankle surgery between January 1, 2015, and May 1, 2020, to evaluate the association between preoperative hemoglobin A1c and union rates.

Demographic and clinical variables were collected, including preoperative and last recorded HbA1c, body mass index, smoking status, peripheral neuropathy, vitamin D level, history of chronic kidney disease, peripheral vascular disease, and surgical location. Patients were categorized according to osseous healing status (union vs nonunion).

Of 106 patients, 87 achieved union and 19 developed a nonunion. Preoperative hemoglobin A1c, last recorded hemoglobin A1c, interval change in hemoglobin A1c, and stratification into clinically relevant A1c categories (<7%, 7-8%, and >8%) were not associated with nonunion (all p>0.05). Age, sex, surgical location, smoking, peripheral neuropathy, peripheral vascular disease, and chronic kidney disease were not associated with healing. Patients with nonunion had significantly greater body weight (p=0.004), higher body mass index (p=0.020), and lower vitamin D levels (p=0.014) than those who achieved union.

Preoperative hemoglobin A1c was not associated with postoperative osseous healing, and no clinically meaningful hemoglobin A1c threshold predictive of nonunion was identified. Elevated body mass index and lower vitamin D levels were associated with impaired healing and may represent more relevant modifiable risk factors than hemoglobin A1c.