Lateral nail plate impingement on the adjacent nail fold, producing pain, inflammation, and granulation tissue.
Also known as: onychocryptosis, ingrown toenail, unguis incarnatus
Overview
Onychocryptosis is the painful inflammatory condition in which the lateral or distal edge of the nail plate penetrates or pressures the adjacent periungual soft tissue, producing inflammation, granulation tissue, and secondary infection. The hallux is involved in the great majority of cases.
Epidemiology
Most common in adolescents and young adults due to increased perspiration, footwear pressure, and active foot use. Also frequent in older adults with toenail dystrophy and reduced self-care. Diabetic patients are at increased risk for serious complications. Slight male predominance.
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Question 1DermatologyEasy
A 19-year-old man presents with a third episode in 8 months of a painful, swollen, erythematous right great toe. Each prior episode was treated with oral antibiotics and warm soaks with temporary improvement. Exam shows the lateral nail fold of the right hallux is erythematous, swollen, and tender, with granulation tissue and purulent drainage where the nail plate embeds into the soft tissue. There is no surrounding cellulitis or systemic symptoms. Which of the following is the most appropriate management?
APartial nail avulsion with phenol matricectomy
BIncision and drainage of the lateral nail fold
CDaily warm soaks and proper nail-trimming education
DComplete surgical avulsion of the entire nail plate
EOral cephalexin for 10 days
Reveal answer & full explanation
Correct answer: A — Partial nail avulsion with phenol matricectomy
APartial nail avulsion with phenol matricectomy✓
BIncision and drainage of the lateral nail fold
CDaily warm soaks and proper nail-trimming education
DComplete surgical avulsion of the entire nail plate
EOral cephalexin for 10 days
Why Partial nail avulsion with phenol matricectomy is correct
This patient has recurrent infected onychocryptosis (ingrown toenail) of the lateral nail fold with chronic granulation tissue — a third episode in 8 months.
Conservative measures (warm soaks, cotton wisp under the nail edge, straight-across trimming) are appropriate for a first or mild episode only; oral antibiotics are added only when there is surrounding cellulitis.
Recurrent disease with chronic granulation tissue requires definitive removal of the offending lateral nail spicule.
The standard procedure is partial nail avulsion (removing the lateral 3–4 mm strip) combined with chemical matricectomy using phenol (or sodium hydroxide) to permanently prevent regrowth of that nail edge.
Cure rates exceed 95% with this approach.
Why the others are wrong
Complete surgical avulsion of the entire nail plate — without matricectomy, this allows regrowth of the deformed nail with high recurrence.
Oral cephalexin for 10 days — antibiotics alone do not address the offending spicule and are insufficient for recurrent disease; they are indicated only for surrounding cellulitis, which is absent here.
Daily warm soaks and proper nail-trimming education — appropriate only for first or mild episodes, not recurrent disease with granulation tissue.
Incision and drainage of the lateral nail fold — the reflex for a fluctuant acute paronychia, and pus is present here, but the infection is driven by the embedded nail edge; draining the fold leaves that spicule in place, so the granulation tissue and infection keep recurring.
Question 2DermatologyMedium
A 19-year-old cross-country runner comes to the clinic with 1 week of pain, redness, and swelling along the lateral border of his right great toe. He reports trimming his toenails by curving the cutters around the corners to "follow the shape of the nail." Examination shows erythema and mild edema of the lateral nail fold with a tender, embedded nail spicule and early granulation tissue. Which of the following is the strongest risk factor for this patient's condition?
ARepetitive running on hard surfaces
BTinea pedis between the toes
CExcessive sweating of both feet
DCurved trimming of the nail corners
EWearing narrow athletic footwear
Reveal answer & full explanation
Correct answer: D — Curved trimming of the nail corners
ARepetitive running on hard surfaces
BTinea pedis between the toes
CExcessive sweating of both feet
DCurved trimming of the nail corners✓
EWearing narrow athletic footwear
Why Curved trimming of the nail corners is correct
Onychocryptosis occurs when the lateral nail plate presses into or pierces the lateral nail fold; rounding the corners leaves a sharp spicule that drives into the soft tissue as the nail grows.
Improper (curved or rounded) nail trimming is the single most common and most directly modifiable risk factor, which is why trimming straight across is the cornerstone of prevention.
Why the others are wrong
Repetitive running on hard surfaces causes repetitive hallux trauma, a contributing risk factor, but it is weaker than misdirected trimming and usually acts by creating the same kind of nail-edge and soft-tissue conflict.
Excessive sweating of both feet (hyperhidrosis) softens the periungual skin and is a recognized contributor, but it is a secondary, lower-yield factor compared with how the nail is cut.
Wearing narrow athletic footwear increases lateral pressure and is a real risk factor, yet it is less determinative than the trimming technique that creates the offending spicule.
Tinea pedis between the toes — athlete's foot is common in runners with sweaty feet and predisposes to cellulitis through fissured interdigital skin, but it involves the toe web spaces and does not drive the nail plate into the lateral nail fold.
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Improper nail trimming (curved or 'rounded' trimming) — most common modifiable factor
Tight, narrow, or ill-fitting footwear
Trauma to the great toe (running, kicking sports)
Hyperhidrosis
Congenital nail-fold or nail-plate shape abnormalities (pincer nails, convoluted toes)
Obesity
Onychomycosis or other nail dystrophy
Oral retinoid therapy (isotretinoin)
Diabetes and peripheral vascular disease (worsen complications, not necessarily incidence)
Pathophysiology
The lateral nail plate, often after misdirected trimming or trauma, presses into or pierces the lateral nail fold. Persistent mechanical pressure and minor breaks in the skin produce inflammation, often followed by bacterial infection (Staphylococcus aureus, mixed flora) and exuberant hypertrophic granulation tissue. Untreated, the condition self-perpetuates because the granulation tissue covers the offending nail edge and prevents spontaneous resolution.
Clinical presentation
Symptoms
Localized pain at the lateral nail fold, exacerbated by footwear or walking
Redness, swelling, and warmth of the affected fold
Purulent or serosanguineous drainage in advanced (Stage II-III) disease
Bleeding from friable granulation tissue
Signs / physical exam
Stage I (inflammation): erythema and mild edema of the nail fold, tenderness with pressure
Stage II (infection): worsened erythema, drainage, hyperhidrosis, beginning granulation
Stage III (chronic): hypertrophic granulation tissue, lateral nail-fold hypertrophy, possible nail plate dystrophy
Typical localization: medial or lateral border of the hallux
Classic findings
Painful, erythematous lateral hallux nail fold with exuberant granulation tissue covering an embedded nail spicule.
Differential diagnosis
Paronychia (acute or chronic) — Inflammation of the proximal/lateral nail fold without nail plate impingement; treat the infection/dermatitis
Pyogenic granuloma of the nail fold — Friable vascular nodule that bleeds easily; may arise on top of chronic ingrown toenail or with retinoid therapy
Subungual exostosis — Bony outgrowth lifting the distal nail; visible on radiograph
Squamous cell carcinoma of the nail unit — Chronic non-healing lesion of the periungual skin; biopsy any persistent unilateral 'ingrown toenail' that does not respond
Partial nail avulsion + phenol matricectomy (definitive)
Heifetz staging of onychocryptosis and stage-directed therapy.
Treatment
First-line
Stage I (mild): warm soaks 10-20 min several times daily; meticulous foot hygiene; loose footwear; trim nails straight across (do NOT round the corners); cotton wisp or dental floss placed under the offending nail edge to lift it off the fold; topical antiseptic (chlorhexidine, povidone-iodine)
Stage I-II with infection: routine topical or oral antibiotics do not improve outcomes and do not replace addressing the nail edge; give oral antibiotics (cephalexin or dicloxacillin; clindamycin or TMP-SMX if MRSA suspected) only when surrounding cellulitis or systemic signs are present
Stage II not responding to conservative care or Stage III: partial nail avulsion (removal of the offending lateral edge of the nail plate) under digital block with 1-2% lidocaine (plain or with epinephrine 1:100,000-200,000, which is safe in digital blocks; use caution in significant peripheral arterial disease) — definitive when combined with matricectomy for recurrent disease
Phenol chemical matricectomy (88% phenol applied to the lateral matrix for 30-60 seconds, repeated) following partial nail avulsion — recurrence about 1-5% in published series; adding phenol lowers recurrence compared with nail surgery without chemical matrix ablation (Cochrane review Eekhof 2012)
Second-line / adjunct
Sodium hydroxide chemical matricectomy as an alternative to phenol
Surgical matricectomy (Winograd procedure) — definitive but higher recurrence than phenol
Silver nitrate 10-25% application to granulation tissue or topical timolol 0.5% solution for exuberant granulation
Gutter splinting or nail-brace therapy for mild recurrent disease in patients unwilling to undergo avulsion
Evaluate and treat hyperhidrosis (aluminum chloride, glycopyrrolate) and ill-fitting footwear
Complications
Recurrence (10-50% after avulsion alone; 1-5% after avulsion + phenol matricectomy)
Cellulitis, osteomyelitis of the distal phalanx (especially in diabetics)
Pyogenic granuloma of the nail fold
Chronic nail dystrophy and cosmetic deformity
Limb-threatening infection in patients with peripheral vascular disease or diabetic neuropathy
Phenol matricectomy local complications: prolonged drainage, hypopigmentation, narrow nail
PANCE pearls
Trim toenails straight across — never round the corners; this is the most important preventive measure.
Conservative therapy (warm soaks, cotton wisp under the nail edge, proper footwear) cures most Stage I cases.
Antibiotics alone do not cure infected onychocryptosis without addressing the nail edge.
Phenol matricectomy after partial nail avulsion is the most durable cure for recurrent disease — Cochrane evidence supports it.
Diabetic and vasculopathic patients require lower threshold for definitive procedure and tight follow-up; do not let mild disease smolder.
Persistent, non-healing 'ingrown toenail' deserves a biopsy to rule out squamous cell carcinoma or amelanotic melanoma — particularly in adults with no clear mechanical cause.
References
Cochrane 2012 — Eekhof JAH et al. Interventions for ingrowing toenails (Cochrane Database Syst Rev 2012)
AAFP — Mayeaux EJ et al. Ingrown toenail management (American Family Physician 2019)
AFP 2009 — Heidelbaugh JJ, Lee H. Management of the ingrown toenail (Am Fam Physician 2009)
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