Metatarsophalangeal Arthrodesis: Risk Factors for Nonunion in a 10-Year Retrospective Cohort

Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/ Purpose: First metatarsophalangeal (MTP) joint fusion is a common surgical procedure to treat hallux rigidus and malalignment at the MTP joint. Nonunion after first MTP arthrodesis has been reported at rates of 2-35%, which may result in continued pain and limitation in function. It is crucial that surgeons identify factors which may increase this risk. However, there is a paucity in the current literature of large, primary studies identifying risk factors for nonunion after first MTP fusion. The present study aims to provide an expansive, single-site analysis of nonunion risk factors after first MTP fusion. We hypothesized risk factors such as diabetes, smoking and a body-mass index (BMI) greater than 30 are associated with increased risk of nonunion. Methods: This was a retrospective cohort study. All patients who underwent first MTP fusion performed by three board certified orthopedic foot and ankle surgeons between 09/20/2013 and 09/20/2023 were included. Pre-operative patient demographics, comorbidities, intraoperative medications, and post-operative complications were collected. Comorbidities of interest included BMI ≥ 30 kg/m2, alcohol use, smoking status, diabetes, peripheral neuropathy, and osteoporosis. Follow-up data collected included diagnosis of nonunion, bone stimulator use, and wound complications. Each variable’s relative risk (RR) was calculated and relationships to the diagnosis of nonunion were evaluated using the Chi-Squared Test of Independence. For all statistical tests, assumptions of α < 0.05 and β = 0.8 were made. Results: A total of 471 patients (364 female) were included. Their mean age was 61.46+/-10.95 years and BMI was 28.01+/-6.70 kg/m2. There were 29 nonunions (6.2%) and 43 wound complications (9.1%). Patients with nonunion did not statistically differ in sex or age. Patients with BMI>30 (RR 2.42, p=0.015), and diabetes (RR 2.81, p=0.028) produced increased rates of nonunion. Diagnosis of peripheral neuropathy was further segmented into diabetic peripheral neuropathy (RR 7.63, p=.006) and idiopathic peripheral neuropathy (RR 4.27, p=0.016), which both showed increased rates. Of the 15 patients prescribed bone stimulators due to observed delayed bone bridging, 4 ultimately progressed to fusion, as verified by imaging (p < 0.001). Osteoporosis (p=1.00), bisphosphonate use (p=0.636), and smoking history (p=0.302) were found to have no statistical difference in nonunion rates. Conclusion: This is the first study to demonstrate higher risk association of nonunion with idiopathic peripheral neuropathy, as well as validate prior findings of diabetic peripheral neuropathy and obese BMI as risk factors. Despite previous literature, both smoking and a preoperative diagnosis of osteoporosis showed no increased risk for nonunion. While the current study cannot draw conclusions on bone stimulator use due to population limitations, the findings do warrant further research to assess their efficacy. Future work should utilize critical appraisal of patients’ diabetes, peripheral neuropathy, and BMI to stratify nonunion risk and optimize arthrodesis outcomes.