What is Subungual Exostosis?
The Exostosis refers to the abnormal bony outgrowth. The word Exostosis is made of three words, which are Ex meaning out, Ost meaning bone, and Osis meaning abnormal growth or condition. The Subungual Exostosis is the abnormal bony outgrowth formed on the tip of the distal phalanx. The Subungual Exostosis on the toe was first observed by the Dupuytren and is, therefore, sometimes referred to as the Dupuytren’s Exostosis, whereas on the fingertips was reported by Hutchinson. It can occur at any age and has no known cause.
Subungual Exostosis Symptoms
The bony outgrowth, Subungual Exostosis, mostly occurs in the big toe, either in the middle or inner region. It also occurs in the other toes, but its frequency is far less. It rarely occurs in the fingers, with the middle and index finger being the most common sites for the Subungual Exostosis. It causes swelling under the nail, which leads to the separation of the nail and the toe. The subungual Exostosis is often misdiagnosed, which leads to incorrect treatment.
Subungual Exostosis is more common in females than in males. It can occur in any age, but the usual onset of the Subungual Exostosis is between the age of 20 to 50 years. The bony outgrowth usually develops under the nail bed and extends upward, leading to the separation of the nail plate from the bed. This causes pain and swelling. It can also cause pain with direct pressure on the affected toe, oedema, deformity of the nail, and erythema.
Sometimes ulceration can also be found. The lesion usually takes weeks to a month to grow. In some individuals, the subungual Exostosis is asymptomatic and is accidentally found in X-rays for other conditions. The symptoms of subungual Exostosis may improve or get worse depending upon the type of shoes being worn.
Subungual Exostosis Causes
There is no clear, known, precise cause of Subungual Exostosis. There are some factors and theories about the cause of Subungual Exostosis. One of the most common theories among them is trauma, which leads to acute or chronic inflammation, thereby causing metaplasia. Around 30% of cases are reported with trauma being the cause of the Subungual Exostosis. According to another theory, the Subungual Exostosis is the result of mechanical irritation, infection, or disease of the nail bed, which causes metaplasia.
Some other theories state that the causes of Subungual Exostosis include tumour, heredity, and cartilaginous cyst activation. Another theory states that the Subungual Exostosis is a reactive response to a microtrauma. This microtrauma leads to fibroblasts growth, which in turn induces metaplasia and calcification. Some of the other factors considered to be the cause of the Subungual Exostosis are recurrent infection, previous surgery, high heel shoes, and first ray foot deformities like hallux limitus and hallux valgus.
Subungual Exostosis Treatment
Before the treatment, it is essential to confirm the bony origin of the lesion through the X-ray. Because the Subungual Exostosis is often confused with the Subungual verruca, amelanotic subungual melanoma, and osteochondroma, the treatment of the Subungual Exostosis can be either nonoperative vs operative. The nonoperative treatment or medical treatment involves nail plate trimming and the wearing of the high box and extra deep or width special shoes that protects the toes and allow freedom of motion—the reduction of the activity and use of painkillers to alleviate the pain associated with the Subungual Exostosis.
The nonoperative treatment only provides the relief of the symptoms, not the cure. The bony outgrowth is progressive that continues to grow; therefore, the best treatment is the surgical removal of the bony outgrowth. The surgery can be done either by direct access to the nail bed or indirect access around the nail plate through the fish mouth incision. The direct access method is used in the case of a defective nail bed, whereas the indirect access lifts the nail and exposes the Subungual Exostosis. The purpose of this surgery is to reduce pain and deformity.
The surgery provides the localized removal of the bony outgrowth without involving other joints and reducing the risk of misalignment. The procedure is usually performed under local anaesthesia. The procedure usually takes 15 to 20 minutes. During the procedure, an incision is made along the toe to allow either direct or indirect access to the bony outgrowth. This bony outgrowth is then resected, and the underlying bone is curetted. The skin is put together and stitched. The absorbable stitches are usually used. The patient is asked to avoid any manual work for at least 4-8 weeks. The complications associated with the surgery are pain, swelling, inflammation, infection, Complex Regional Pain Syndrome, and scarring.