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When ‘Ingrown Toenail’ Pain May Be Caused By A Subungual Exostosis

Disorders of toenails easily rank in the top five most common podiatric complaints in our patient population. We see ingrown toenails every day and sometimes we get into a rut assuming that the source of all pain from the toenail is the toenail itself.

It is important to obtain an accurate history on the location of the pain. It is more important to examine the toe rather than just looking at it and saying, “Yes, that is an ingrown nail” and recommending a partial nail avulsion with a matrixectomy.

The examination should include careful inspection of the nail plate. If the nail plate is deformed, there may be a history of nail root damage or chronic pressure on the nail plate. Palpation exams should include not only the medial and lateral nail folds where ingrown toenails are common, but also direct pressure dorsal to plantar on the nail plate itself. When one locates pain at the nail fold and it is obvious that the nail is intimate with the skin, the clinician can narrow down the diagnosis to either onychocryptosis or paronychia.

However, if pain is not only on the nail folds but directly under the nail, then there may be a subungual exostosis. Physicians should proceed to investigate further further with an X-ray.

The presentation of pain associated with a subungual exostosis can be very subtle or quite obvious. Part of the examination for pain under the toenail should include a lateral X-ray of the affected digit. I will have the patient rest the toe on a roll of gauze to elevate the toe to reduce superimposition of the other digits.

Remember that the exostosis is a benign bone tumor comprised of bone and cartilage called an osteochondroma. Therefore, when one sees the spur on the X-ray, only the bone component is visible. I explain that to my patients because a seemingly tiny piece of bone growth under the nail does not seem like the logical source of any significant pain.

After diagnosing subungual exostosis, one should decide whether to remove the exostosis or not. One option is to permanently remove the toenail if there is a small exostosis and the toenail is thickened or severely deformed. Another option is to remove the exostosis.

If the patient cannot decide what to do, I often will recommend a temporary total nail avulsion. If during the first few months of not having a nail, the patient has no pain and is not bothered by not having a nail, then the decision to permanently remove the nail is easy.

From a surgical standpoint for removal of a subungual exostosis, I typically perform a fish mouth incision without removing the toenail. If the exostosis is very large and the nail bed and bone are tenting the nail, then I usually remove part of the nail or the entire nail.

One of the most common errors in incision planning is creating the incision too plantar. I tend to make the incision as dorsal (close to the nail) as possible, just so I can get the suture needle to grab some skin on the dorsal (superior) side. The incision is sharp to bone and I sharply dissect the distal phalanx away from the soft tissue to expose the tuft of the bone and exostosis. I generally use the sagittal saw and do a fairly aggressive resection of bone including the exostosis.

The final X-ray will have a beveled appearance of the distal phalanx. Then close the skin with nylon in a simple fashion.

In summary, don't forget about the subungual exostosis in the assessment of disorders of the toenail. The next “ingrown nail” you see may be a subungual exostosis in disguise.

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