Medial and lateral exostoses of the distal phalanx of the hallux: A potentially painful bunion-like structure. Part 1: Incidence and clinical application.

BACKGROUND: Exostoses at the base of the distal phalanx of the great toe are usually asymptomatic. The literature has not generally considered them as the origin of a possible problem resulting from a pressure conflict between hallux and shoe (medial aspect) or second toe (lateral aspect) nor a potential complication of surgical correction of hallux valgus deformity. No studies, to our knowledge, have evaluated its possible correlation with other foot disorders. When one of these neglected exostoses became painful after surgical correction of hallux valgus, we decided to start a study to determine their possible origin, prevalence in daily practice and histo-pathological morphology.

METHODS: Two hundred and fifty-four feet of patients (average age 41.7y.) were enrolled in the study from January 2007 to June 2009. Dorsoplantar weight-bearing radiographs were used to analyze the presence of exostoses and their correlation with the distal phalanx morphology, metatarsal formula (or transverse plane orientation of the metatarsal heads parabola) and hallux valgus angles. Patients were classified according to their age and main symptom for consultation. Four exostoses removed from cadaver feet were also analyzed microscopically.

RESULTS: Osseous excrescences arising on the medial or lateral aspect at the proximal part of the terminal phalanx of the hallux were observed in 132 feet (51.9%). Thirty-five feet out of these 132 (13.7%) had exostoses on both sides of the phalanx.A statistically significant positive correlation was found between the presence of a medial exostosis of the phalanx and the severity of HVA. Patients with higher IPH and asymmetry angles have a lower prevalence of medial exostoses (p<0.05). Amongst the different morphologies of the second phalanx, exostoses were most likely found in the standard form.

CONCLUSIONS: Prevalence of exostoses at the base of the distal phalanx is high (51.9% of the studied feet). Histological findings would suggest that these exostoses could be considered a mechanical reactive process, produced by a chronic irritation by shoes. We encourage surgeons to be aware of its potential clinical implications. Direct resection is very simple and the most appropriate treatment for symptomatic cases.