High-yield overview
When the Nail Edge Invades the Nail Fold
HalluxMost common site (great toe)
3 stagesHeifetz/Mozena severity
PhenolMatricectomy = lowest recurrence
~1-1.5%Recurrence after phenol matricectomy
HEIFETZ / MOZENA staging
Stage I (inflammatory)
PatternErythema, mild swelling and pain at the lateral nail fold; no discharge.
Treatment
Stage II (abscess/infection)
PatternIncreased pain, infection and serous/purulent DISCHARGE from the fold.
Treatment
Stage III (granulation/hypertrophy)
PatternChronic granulation tissue and hypertrophy of the lateral nail wall over the nail plate.
Treatment
(Mozena stage IV)
PatternChronic severe deformity with marked hypertrophy of both nail folds.
Treatment
Critical Must-Knows
- Onychocryptosis (ingrown toenail) is penetration of the LATERAL NAIL FOLD by the edge or a spicule of the nail plate, which acts as a foreign body and provokes inflammation, secondary infection and exuberant GRANULATION tissue; it most often affects the GREAT TOE (hallux).
- Contributing factors are improper nail cutting (cutting the nail too short or curved rather than straight across, leaving a spicule), TIGHT/constrictive footwear, trauma, HYPERHIDROSIS, abnormal nail shape (involuted/pincer nail), obesity and a genetic predisposition.
- Severity is graded by the HEIFETZ (and extended MOZENA) staging: stage I inflammatory (erythema/swelling/pain), stage II infected with discharge, stage III chronic granulation tissue and lateral wall hypertrophy (Mozena adds a stage IV with gross bilateral hypertrophy) - the stage guides treatment.
- EARLY (stage I) disease is managed CONSERVATIVELY: warm soaks, correct STRAIGHT-ACROSS nail trimming, lifting the nail edge off the fold with a cotton wisp/dental-floss or a gutter splint, taping techniques, roomy footwear, and treating any infection.
- When conservative measures fail, or for stage II-III disease, the definitive treatment is PARTIAL NAIL AVULSION combined with MATRICECTOMY of the corresponding nail-matrix horn - removing the offending nail edge AND ablating the matrix that produces it; matricectomy markedly reduces recurrence compared with simple avulsion alone.
- CHEMICAL matricectomy with PHENOL is the preferred modality for grade II-III onychocryptosis: meta-analysis shows phenol gives LOWER RECURRENCE and less pain than other methods, and a large series using a 4-minute application reported a recurrence of only about 1.1% (higher in cardiovascular disease and the young) - alternatives are sodium hydroxide/TCA chemical matricectomy and surgical (Winograd) wedge excision of the matrix.
Clinical Pearls
- “Ingrown toenail = nail edge/spicule penetrates the LATERAL nail fold (usually hallux); Heifetz/Mozena stages I-III(-IV).
- “Stage I: conservative (straight trimming, soaks, cotton wisp/gutter splint, footwear). Stage II-III: partial avulsion + matricectomy.
- “Phenol chemical matricectomy = lowest recurrence (~1-1.5%) and less pain (meta-analysis); matricectomy beats avulsion alone.
Avulsion Alone Recurs - Add a Matricectomy
Simple nail avulsion
Removing the offending nail edge without treating the matrix leaves the matrix to grow the same nail shape back - high recurrence. Acceptable only as a temporary measure.
Avulsion + matricectomy
Partial avulsion + matricectomy (chemical/phenol or surgical/Winograd) ablates the matrix horn that produces the offending edge - low recurrence (~1-1.5% with phenol). Preferred definitive treatment.
Pathogenesis & Presentation
A Foreign-Body Reaction in the Nail Fold
The nail plate edge or a retained spicule penetrates the soft tissue of the lateral nail fold. The embedded keratin behaves as a foreign body, driving an inflammatory response with pain, erythema and swelling; the breached skin is then prone to secondary infection, and chronic irritation produces granulation tissue and hypertrophy of the nail wall. Patients present with a painful, red, swollen nail fold of the great toe, often with discharge, and pain on footwear pressure. Recognising the stage (Heifetz/Mozena) directs whether conservative or surgical treatment is appropriate.
Management
Match the Treatment to the Stage
- Stage I (conservative): warm soaks, correct straight-across nail trimming (never cut down the corners), elevating the nail edge with a cotton wisp / dental-floss or a gutter splint, taping the fold away from the nail, roomy footwear, foot hygiene, and treating infection. Many early cases settle.
- Stage II-III / failed conservative care (definitive surgery): partial nail avulsion of the offending
border plus matricectomy of the corresponding matrix horn. Matricectomy options:
- Chemical matricectomy - PHENOL (preferred for grade II-III): apply phenol to the exposed matrix (commonly a 4-minute application) after avulsion - lowest recurrence and less pain.
- Chemical - sodium hydroxide / TCA: alternatives with comparable efficacy; some reports show less postoperative discharge.
- Surgical (Winograd) wedge excision of the lateral nail, matrix and inflamed fold; or Zadik/terminal Syme procedures for total matrix ablation in severe recurrent disease.
- Treat active infection, ensure tetanus cover where relevant, and counsel diabetic/vascular patients carefully (impaired healing).
Related Toenail Disorders (differential)
Not every painful or deformed toenail is onychocryptosis - keep in mind: onychomycosis (fungal nail - thickened, discoloured, crumbly), onychogryphosis ('ram's horn' grossly thickened curved nail), subungual exostosis / osteochondroma (a bony outgrowth of the distal phalanx lifting the nail - radiograph if suspected), subungual melanoma (a pigmented streak/Hutchinson's sign - do not miss), pincer/involuted nail (transverse over-curvature), and paronychia (nail-fold infection). See our Paronychia and Subungual Exostosis topics.
Evidence & Key Studies
Evidence
Efficacy and safety of phenol-based partial matricectomy in onychocryptosis: a systematic review and meta-analysis
Vinay K, Narayan Ravivarma V, Thakur V, et al. • Journal of the European Academy of Dermatology and Venereology (2022)
Key Findings:
- Across 18 controlled studies (1655 patients), phenol matricectomy was associated with significantly FEWER recurrences than other modalities (about 49 fewer per 1000).
- Phenol also produced less postoperative pain; however TCA- and NaOH-based matricectomies had less postoperative discharge/haemorrhage.
- Phenol matricectomy combines a low recurrence rate with a favourable adverse-effect profile and is the preferred modality for grade II-III onychocryptosis.
Evidence
Recurrence of onychocryptosis treated with phenolization: does phenol application time matter? A follow-up of 622 procedures
Montesi S, Lazzarino AI, Galeone G, et al. • Dermatology (2019)
Key Findings:
- In 622 consecutive procedures using a 4-minute phenol chemical matricectomy, overall recurrence was only 1.1%.
- Recurrence was higher in patients with cardiovascular disease (5.1%) and in younger patients.
- An uninterrupted 4-minute phenol application appears to be an appropriate time to achieve matrix ablation with a low recurrence rate.
Evidence Attribution
According to PubMed, the superiority of phenol matricectomy for recurrence/pain comes from the cited Vinay meta-analysis, and the ~1.1% recurrence with a 4-minute application (higher with cardiovascular disease and youth) from the cited Montesi series. The Heifetz/Mozena staging and conservative measures are standard clinical teaching. (See also our Paronychia and Diabetic Foot topics.)
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
Viva scenarioStandard
Clinical prompt
“How would you assess and manage a patient with a painful ingrown great toenail, and what determines whether you operate?”
Practical approach
Ingrown toenail, or onychocryptosis, is penetration of the lateral nail fold by the edge or a spicule of the nail plate, which acts as a foreign body and causes inflammation, infection and granulation tissue, usually of the great toe. I would take a history for nail-cutting habits, footwear, trauma, sweating, recurrence and relevant comorbidities such as diabetes or vascular disease, and examine the toe to stage the severity using the Heifetz or Mozena system: stage I is inflammatory with erythema, swelling and pain; stage II adds infection and discharge; stage III has chronic granulation tissue and hypertrophy of the nail wall. The stage determines treatment. For stage I, I would manage conservatively: warm soaks, correct straight-across nail trimming, lifting the nail edge off the fold with a cotton wisp, dental floss or a gutter splint, taping, roomy footwear and treating any infection. If conservative treatment fails or for established stage II to III disease, the definitive treatment is partial nail avulsion of the offending border combined with a matricectomy of that matrix horn, because removing the nail edge without ablating the matrix leads to high recurrence. My preferred matricectomy is chemical, using phenol, which the evidence shows gives the lowest recurrence - around one to one-and-a-half percent - and less pain; surgical wedge excision such as the Winograd procedure is an alternative. I would take particular care in diabetic or vascular patients because of impaired healing.
Key clinical points
Onychocryptosis = nail edge penetrates lateral fold (usually hallux); foreign-body inflammation/granulation
Stage with Heifetz/Mozena (I inflammatory, II infected, III granulation/hypertrophy)
Stage I conservative (straight trimming, soaks, cotton wisp/gutter splint, footwear)
Failed/stage II-III: partial avulsion + matricectomy; phenol = lowest recurrence (~1-1.5%); avulsion alone recurs
Common pitfalls
Doing simple avulsion alone (high recurrence) instead of adding matricectomy
Cutting the nail down the corners (creates a spicule)
Ignoring diabetes/vascular status before nail surgery
Further questions
“Why does avulsion alone recur? - The matrix regrows the same nail shape; you must ablate the matrix horn”
“Which matricectomy has the lowest recurrence? - Phenol chemical matricectomy”
Viva scenarioStandard
Clinical prompt
“A nail looks abnormal but is lifting up with a firm swelling under the nail edge, and the toe is not simply inflamed at the fold. What else must you consider besides an ingrown toenail?”
Practical approach
A toenail problem is not always onychocryptosis, and a firm swelling lifting the nail should prompt me to consider a subungual exostosis or osteochondroma - a bony outgrowth of the distal phalanx that elevates and deforms the nail - which I would investigate with a plain radiograph and treat by excision if confirmed. The other important diagnoses not to miss are a subungual melanoma, suggested by a pigmented longitudinal streak or pigment spreading onto the nail fold, which is Hutchinson's sign, and which needs biopsy; onychomycosis, a fungal infection producing a thickened, discoloured, crumbly nail; onychogryphosis, the grossly thickened ram's-horn nail of the elderly or neglected foot; a pincer or involuted nail with transverse over-curvature; and paronychia, infection of the nail fold. So my approach to an abnormal nail is to characterise it clinically, image it if I suspect bone involvement, and biopsy anything suspicious for melanoma, rather than assuming every painful nail is simply ingrown.
Key clinical points
Firm swelling lifting the nail -> subungual exostosis/osteochondroma (radiograph; excise)
Do NOT miss subungual melanoma (pigmented streak / Hutchinson's sign -> biopsy)
Differential: onychomycosis, onychogryphosis, pincer/involuted nail, paronychia
Characterise clinically; image if bone suspected; biopsy if melanoma suspected
Common pitfalls
Labelling every painful/deformed nail as 'ingrown'
Missing a subungual melanoma
Not radiographing a firm subungual swelling (exostosis)
Further questions
“What sign suggests subungual melanoma? - Hutchinson's sign (pigment onto the nail fold)”
“How do you confirm a subungual exostosis? - Plain radiograph of the distal phalanx”
Mnemonics & Memory Aids
Mnemonic
STRAIGHT
S
Soaks (warm) for early disease
T
Trim straight across (never down the corners)
R
Raise the nail edge (cotton wisp / gutter splint)
A
Avulsion (partial) of the offending border
I
Infection - treat it
G
Granulation/hypertrophy = stage III (operate)
H
Healing care in diabetics/vascular patients
T
Tissue matrix ablation (phenol) for low recurrence
Hook:Cut STRAIGHT across - and for the matrix, ablate it (phenol) to stop recurrence.
Mnemonic
PHENOL
P
Partial avulsion first
H
Horn of matrix is the target
E
Evidence: lowest recurrence + less pain
N
Nail matrix chemically ablated
O
~1.1% recurrence (4-min application)
L
Low complication profile (preferred grade II-III)
Hook:PHENOL matricectomy = partial avulsion + ablate the matrix horn = low recurrence.
Exam day cheat sheet
Onychocryptosis - Exam Day Cheat Sheet
Definition & cause
- Nail edge/spicule penetrates the lateral nail fold (usually hallux)
- Causes: cutting too short/curved, tight shoes, trauma, hyperhidrosis, pincer nail
- Foreign-body inflammation -> infection -> granulation/hypertrophy
Staging (Heifetz/Mozena)
- I: inflammatory (erythema/swelling/pain)
- II: infected with discharge
- III: granulation + lateral wall hypertrophy (Mozena IV: gross bilateral)
Treatment
- Stage I: soaks, straight trimming, cotton wisp/gutter splint, footwear
- Stage II-III/failed: partial avulsion + MATRICECTOMY (avulsion alone recurs)
- Phenol chemical matricectomy preferred (lowest recurrence ~1-1.5%, less pain); Winograd = surgical option
Differential (abnormal nail)
- Subungual exostosis (radiograph), subungual melanoma (Hutchinson's - biopsy)
- Onychomycosis, onychogryphosis, pincer/involuted nail, paronychia
- Care in diabetic/vascular feet (healing)