Ingrown Nails and Retronychia
Ingrown nails (onychocryptosis) and retronychia (retrograde onychocryptosis) are the two most serious forms of mechanical injury in which the nail invades the surrounding soft tissue. Both cause fibrosing inflammation, intense pain and overgrown granulation tissue.
Although both involve the nail plate piercing the tissue around it, they develop in completely different anatomical directions:
- Lateral ingrown nail (onychocryptosis / ingrown toenail):
- The nail plate grows forward toward its free edge, but its curved or sharp side edge pierces the epidermis and digs into the lateral nail fold.
- The sharp edge acts as a mechanical foreign body, triggering an acute cell-mediated inflammatory reaction with swelling, discharge, secondary infection and overgrown granulation tissue that spreads over the nail plate.
- Retronychia (backward or proximal ingrowth):
- The nail plate grows backward and embeds itself in the proximal nail fold.
- It usually follows repeated mechanical trauma to the tip of the toe (tight shoes, playing soccer). Instead of sliding forward, the new nail gets stuck and is pushed up beneath the proximal nail fold. This stacking of nail plates, old and new, sets off persistent granulomatous inflammation at the base of the nail.
Main Causes
- Incorrect nail trimming (the leading cause of onychocryptosis): cutting the nail too short or digging deep into the corners of the big toenail leaves a sharp spicule that pierces the skin as the nail grows.
- Mechanical pressure and footwear: tight closed-toe shoes and high heels that squeeze the toes; repeated toe trauma in athletes.
- Congenital anatomical abnormalities: an overly curved nail plate (pincer nails), an enlarged lateral nail fold, or a hammer toe.
- Associated conditions: excessive foot sweating (hyperhidrosis), which softens and tears the skin of the lateral nail fold, and nail fungus that deforms the nail.
Ingrown nails and retronychia are common, painful urgent problems that are often mishandled at nail salons (aggressive corner cutting that makes recurrence worse) or treated with long, unnecessary courses of oral antibiotics. At Haute-Derma, we follow the Heifetz/Kline clinical staging system. In early stages we favor minimally invasive, tissue-sparing techniques (cotton packing or gutter splints, BS-Spange orthotic braces). For recurrent cases or those with overgrown granulation tissue, we perform partial nail avulsion with 88% phenol matrixectomy.
Clinical Staging of Ingrown Nails (Heifetz and Kline)
Accurate staging helps the doctor choose between conservative and surgical treatment:
- Stage 1 (mild inflammation):
- The lateral nail fold is slightly swollen and red, with sharp pain on pressure.
- No pus and no granulation tissue yet.
- Stage 2 (infection/discharge, moderate):
- The lateral nail fold is markedly swollen, deep red and very painful.
- Mucus-like discharge or pus collects in the lateral groove, and the skin of the nail fold becomes eroded.
- Stage 3 (chronic granulation tissue, severe):
- Lumpy, overgrown granulation tissue that bleeds easily and partly covers the nail plate.
- Chronic inflammation, a hardened and deformed lateral nail fold, and constant pain with movement.
Onychocryptosis vs. Retronychia
| Feature | Lateral Ingrown Nail (Onychocryptosis) | Retronychia (Backward Ingrowth) |
|---|---|---|
| Site of penetration and inflammation | Lateral nail fold | Proximal nail fold / nail base |
| Mechanism | Sharp side edge digs sideways into the skin | Nail plate stops sliding forward and pushes backward |
| Key signs | Nail spicule in the lateral groove, granulation tissue at the side | Red, swollen proximal fold, loss of cuticle, stacked layers of nail |
| Onychoscopy findings | Lateral groove covered by granulation tissue and keratin spicules | Yellow/brown band at the nail base, dilated vessels in the proximal fold |
| Leading cause | Incorrect corner cutting, tight shoes | Repeated microtrauma to the toe tip |
| Best intervention | Partial nail avulsion + lateral matrixectomy | Removal of the entire damaged nail plate (nail avulsion) |
Treatment Protocols and Procedures at Haute-Derma
Conservative Treatment (for Stage 1 and Some Mild Stage 2 Cases)
- Cotton packing / gutter splinting:
- A small wisp of sterile cotton or a length of soft plastic tubing slit lengthwise (1–2 mm in diameter) is placed between the sharp nail edge and the lateral nail fold.
- The tube acts as a protective channel that separates the nail from the skin, letting the nail grow out without cutting into soft tissue.
- Nail bracing (orthonyxia / BS-Spange):
- A spring or composite strip is bonded to the nail surface. Its elastic force gently lifts both side edges of the nail, relieving pressure on the nail grooves.
- Taping technique:
- Stretchy medical tape is applied to the lateral nail fold, pulling it away from the nail, and anchored around the underside of the toe.
Definitive Minor Surgery (for Severe Stage 2, Stage 3 and Retronychia)
- Partial nail avulsion with chemical matrixectomy:
- Regional anesthesia: a digital block with 2% lidocaine without epinephrine.
- Longitudinal cut along the side: special nail scissors are used to cut a 2–3 mm strip along the ingrown edge, from the free edge all the way under the proximal nail fold.
- Strip removal and clearing granulation tissue: forceps are used to pull out the embedded nail strip, and necrotic granulation tissue is cleaned away.
- Phenol matrixectomy (phenolization): 88% phenol is applied with a special cotton-tipped applicator to the corresponding lateral horn of the nail matrix for 1–3 minutes in total (60 seconds at a time, repeated up to 3 times) to permanently destroy the matrix cells at that corner.
- Neutralizing rinse and dressing: the phenol-treated area is flushed with 70% alcohol or saline, antibiotic ointment is applied, and a pressure dressing is placed.
Advantages of phenolization: a recurrence rate of only < 2–5% (compared with 20–40% when the nail is simply cut without treating the matrix). Phenol also has antibacterial and local anesthetic effects, so patients feel very little pain after the procedure.
- Managing retronychia:
- The stacked, damaged nail plates must be removed completely (total nail avulsion) to free the proximal nail fold. The underlying matrix then recovers and grows a completely new nail over 6–12 months.
