What is Retronychia?
Retronychia is essentially a "proximal" ingrown toenail. Instead of the side edges of the nail digging into the skin near the tip of the toe (the standard ingrown nail), the entire nail plate is pushed backward, embedding itself deep into the proximal nail fold (the cuticle area). It almost exclusively affects the big toes (hallux).
The "Layered Nail" Phenomenon
Retronychia creates a very distinct mechanical problem within the nail factory (matrix).
The Mechanism
- Trauma causes the nail plate to completely detach from the matrix (root).
- However, the old nail fails to shed completely.
- A new nail begins growing underneath the old one.
- The old nail is forced backward, acting like a foreign body in the cuticle.
Clinical Signs
- Intense redness, swelling, and pain isolated to the cuticle area.
- Elevation of the proximal nail fold.
- Yellowish discoloration and thickening of the nail (due to multiple layers of nail plate stacked together).
Why Does It Happen?
The primary cause is repetitive micro-trauma combined with restrictive footwear. It is frequently seen in runners, hikers, and women who wear tight, high-heeled shoes.
When the toe constantly jams into the front of a shoe during walking or running, the force is transmitted backward. Over time, this backward force overcomes the forward growth of the nail, detaching it from the root and setting the stage for the new nail to grow underneath it.
Surgical Resolution
Retronychia rarely resolves with antibiotics or soaking, because the problem is mechanical—a hard piece of keratin is embedded in the flesh. The definitive, curative treatment is a minor podiatric procedure called a Proximal Nail Avulsion. Under local anesthesia, the specialist will carefully remove the top, embedded layer of the old nail, leaving the new nail underneath to grow out naturally. The pain and inflammation typically resolve within days of the procedure.