Onychocryptosis can be understood by splitting the term - onyx meaning nail and kryptos meaning hidden. It is a common form of nail disease. It is also called ingrowing toenail or embedded toenail or unguis incarnatus.
Here the nail grows out of its normal shape to form a curve. It develops lateral spikes that irritate the adjacent structures. Assume if someone hits you, you react to it, don't you? Similarly, when the spiked nail keeps on hitting the lateral skin, they respond to this by forming erythema, granulation tissues, etc.
Why do nails assume these abnormal shapes?
The most common etiology accepted is tight-fitting shoes, improper nail trimming, and bad foot hygiene. This is more common in the great toe on the lateral side and mostly bilateral because you would have the same wrong sized shoe on both sides.
The diagnosis is often straightforward, you see a patient present with a painfully swollen toe and the surrounding tissues are red, then it’s a case of onychocryptosis. The pain can range from a simple difficulty in walking to the inability to walk depending on the stage of the disease.
Another disease that simulates the condition is subungual exostosis which can be confirmed with an X-Ray showing bony proliferation.
The disease usually progresses in three stages,
Stage 1: Signs of inflammation with swelling and erythema of the surrounding skin
Stage 2: Acute infection with discharge and pain
Stage 3: Chronic infection with soft tissue hypertrophy and the formation of granulation tissue
Treatment
In case, if the patient is in stage 1 or 2 then conservative measures are sufficient, but if the patient has already progressed to stage 3 causing him disability then surgical methods become mandatory.
Self-help is the best help: a selection of proper shoe size is important. It is better to avoid shoes that are too small or narrow. Proper nail trimming can avoid the growth of lateral spikes. It should be cut in a straight fashion and not curved or too short.
Why not curved? The shorter curved portion of a nail can grow and get trapped in the skin surrounding the nail, which is a predisposing factor to develop the disease.
The affected toe has to be soaked in hot water. This will relieve the pain in most cases. If granulation tissue has formed then topical NSAIDS can help. A topical antibiotic has to be applied for controlling the infection.
Other conservative techniques:
The main aim is to safeguard the skin from the nail by either elevating it or pulling it away from the skin. This can be achieved by
- Cotton-wick insertion or dental floss insertion to raise the nail from the skin.
- A gutter splint or sleeve technique-gutters are prepared by cutting vinyl IV infusion tubes and this is used to separate the nail from the skin.
- Taping procedure – one end is attached to the ingrowing nail and the remaining is twisted around the toe. This is safe and less painful when compared to other procedures.
Surgical procedures:
These are exclusive for stage 3 disease and is performed under local anesthesia
- Spicule matricectomy - only the portion of the nail which is affected is removed
- Chemical partial matricectomy - it is done with phenol. This technique is the most accepted one with better outcomes. Other agents used for this purpose include sodium hydroxide and trichloroacetic acid.
- Complete matricectomy - the whole of the affected nail with its nail bed is removed.
There are different types of incision followed to perform the above procedures:
- Zadiks / fowlers incision - 45 degree angled with root flap.
- L shaped / frost incision
- D shaped / Winograd incision
- H shaped / Kaplan incision.
Newer techniques include - electrocautery, radiofrequency ablation, and carbon dioxide laser ablation.
Recurrences can follow any procedure but are least with chemical and laser matricectomy.
References:
Author’s Footnote
Ram’s horn nail/onychogryphosis is a similar condition in which the nails are curved upward. It usually develops due to repeated trauma or infection. They are generally treated surgically (matricectomy).
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