Association between onychogryphosis and lower extremity complications: a multicenter cohort study using TriNetX

Introduction: Onychogryphosis has been associated with chronic foot injury and vascular disease. We evaluated whether onychogryphosis is associated with increased 5 year risk of lower extremity complications. Methods: Using TriNetX Research Network patients with onychogryphosis were propensity score matched 1:1 to controls for age, sex, race, obesity, type II diabetes, chronic kidney disease, and smoking. Cox proportional hazards models estimated 5 year hazard ratios (HRs) for lower extremity complications, with subgroup analyses for diabetes and peripheral artery disease (PAD). Results: After matching (174,537 per cohort), onychogryphosis was associated with increased 5 year risk of foot/toe amputation procedures (HR 2.798, 95% CI 2.516-3.111), ulcer (HR 2.108, 95% CI 2.023-2.196), cellulitis (HR 1.743, 95% CI 1.685-1.803), osteomyelitis (HR 1.673, 95% CI 1.583-1.769) and gangrene (HR 1.485, 95% CI 1.382-1.597) (all p<0.0001). Associations remained significant in diabetes and PAD restricted analyses. Conclusion: Onychogryphosis was associated with substantially increased 5 year risk of major lower extremity complications in a large matched cohort, with consistent findings among patients with type II diabetes and PAD. We recommend focused lower extremity assessment and brief risk screening with low threshold for vascular or primary care referral in high-risk patients with onychogryphosis.