Subungual exostosis

Subungual exostoses are bony projections which arise from the dorsal surface of the distal phalanx, most commonly of the hallux (the big toe).Subungual exostosis (2/3)Subungual exostosis (3/3), after excision Subungual exostoses are bony projections which arise from the dorsal surface of the distal phalanx, most commonly of the hallux (the big toe). They tend to be painful due to the pressure applied to the nail bed and plate. They can involve destruction of the nail bed. These lesions are not true osteochondromas, rather it is a reactive cartilage metaplasia. The reason it occurs on the dorsal aspect is because the periosteum is loose dorsally but very tightly adherent volarly. Subungal malignant melanomas can also occur in canines. They are distinct from subungual osteochondroma.