Narrow ungual tuberosity associated with ingrown toenail: a case-control study based on foot imaging

Ingrown toenails are a common condition, yet their underlying cause remains unclear. This study investigates the association between the width of the distal phalanx of the hallux and the development of ingrown toenails. This case-control study included 86 patients diagnosed with ingrown toenails and 102 healthy control subjects. The mean age of patients in the ingrown toenail group was 31.71 ± 15.55 years, compared with 34.57 ± 12.30 years in the control group. The widest distance of the tuberositas unguis (TW) and the width of the nail bed (NB) were significantly lower in the ingrown toenail group than in the control group (9.97 ± 1.47 vs. 11.49 ± 1.04, p < 0.001; and 16.01 ± 2.65 vs. 17.14 ± 1.89, p = 0.001, respectively). In comparison, the width of the lateral nail fold (NF) was significantly greater in the ingrown toenail group than in controls (27.62 ± 4.43 vs. 25.82 ± 2.13, p = 0.001). Binary multivariate logistic regression analysis showed that only TW was negatively associated with ingrown toenail occurrence (odds ratio [OR] 0.279, 95% confidence interval [CI] 0.143–0.544, p < 0.05). Abnormal narrowing of the ungual tuberosity in the distal phalanx of the hallux appears to be a risk factor for ingrown toenails. These findings provide further insight into the etiology of this condition.