Three of the commonest minor procedures in general practice concern the nails, and all three rest on the same foundation: an effective digital block and a tourniquet. Without a bloodless field one works by feel, and by feel nail spicules are left behind — which is the commonest cause of recurrence.

Indications

Condition	Procedure
Acute paronychia with fluctuance or visible pus	Incision and drainage
Acute paronychia without pus formation	Antibiotics and soaks alone
Ingrown nail with mild inflammation	Splinting with a cotton wisp
Ingrown nail with moderate inflammation	Splinting with a strip of suture material or a drain
Ingrown nail, severe or recurrent	Partial nail avulsion, often with chemical matrix ablation
A nail spicule that has split off	Removal of the spicule
A painful subungual haematoma with an intact nail plate and intact nail folds	Trephination, whatever the size of the haematoma
A subungual haematoma with a split, loosened or avulsed nail plate, or a damaged nail fold edge	Nail avulsion and inspection of the nail bed, with suture of any nail bed laceration

Contraindications

There are no absolute contraindications, but be cautious and consider referral in:

Diabetes with neuropathy or peripheral arterial disease — a risk of osteomyelitis and poor healing. Check the ankle-brachial index and the foot status before any procedure on a toe.
Critical ischaemia.
Immunosuppression.
Suspicion of another diagnosis: gout, a felon (pulp abscess), herpetic whitlow (never incise a herpetic whitlow), subungual melanoma (a pigmented longitudinal nail band that is widening, with pigment in the cuticle — Hutchinson's sign).
An open fracture of the distal phalanx with a subungual haematoma — manage it as an open fracture.

The anatomy of the nail apparatus

The terminology is hard to follow without a picture, and several of the steps below refer to structures that are not visible when looking at the nail.

The nail plate is the hard, visible nail.
The nail bed is the tissue beneath the nail plate; a laceration here heals with a deformed nail unless it is sutured.
The matrix lies most proximally, largely hidden beneath the proximal nail fold, and is the only tissue that produces new nail. Its visible distal part is the lunula.
The matrix horns are the lateral extensions of the matrix, reaching out to the sides beneath the nail folds. It is these that must be destroyed during matrix ablation — miss the horn and the nail spike returns in the same corner.
The nail folds are the skin folds proximal and lateral to the plate, and the cuticle is the flap of skin that extends from the proximal fold over the base of the plate.

The nail apparatus in longitudinal section beside the same nail seen from above, with the matrix proximally beneath the nail fold and the matrix horns in the proximal corners — Figure 1. On the left a longitudinal section through the fingertip: the bone of the terminal phalanx at the bottom, the nail bed as a thin layer above it, and the nail plate uppermost. Most proximally, hidden beneath the proximal nail fold and the cuticle, lies the matrix — the violet zone — where the nail plate is formed and pushed forward. The insertion of the extensor tendon lies immediately above the matrix, which is the reason not to go deeper than necessary proximally. On the right the same nail from above, where the lateral extensions of the matrix, the matrix horns, appear in both proximal corners beneath the nail folds. The nail plate grows out at its full width only as long as the horns are intact, and it is the horn on the ingrown side that the phenol must reach.

Preparation and equipment

Chlorhexidine in alcohol or an iodine solution.
Lidocaine 10 mg/mL without adrenaline for the block (adrenaline is safe in fingers and toes according to modern data, but there is rarely any reason to use it when a tourniquet is being applied anyway), a 27 G needle, a 5 mL syringe.
A tourniquet: a Penrose drain with artery forceps, or the cut-off finger of a sterile glove rolled down.
A nail splitter or strong pointed scissors, a Freer elevator or small artery forceps, toothed surgical forceps.
A size 11 scalpel.
A chemical cautery agent: phenol 88 %, sodium hydroxide 10 % or silver nitrate.
Electrocautery or a heated paper clip for trephination.
Antibiotic ointment, a non-adherent dressing, gauze.

The digital block

Anaesthetise from the dorsal aspect, one injection medial and one lateral to the base of the phalanx, 2–3 mL on each side, with the needle tip directed volarly until a weal forms over the volar nerve. Wait 10 minutes — insufficient waiting time is the commonest reason for the patient finding the procedure painful. Test with a needle tip before you start.

Apply the tourniquet only after the block has taken effect, and note the time. It must not stay on for longer than 20–30 minutes.

A finger seen from the dorsal aspect with two needles inserted on either side of the base of the proximal phalanx and zones of spread around the volar nerve bundles — Figure 2. Digital nerve block. The needle is inserted from the dorsal aspect on either side of the base of the proximal phalanx, close to the bone, and directed volarly. The four nerves of the finger run in the corners: the two large volar nerves, each with an artery beside it, and the two thinner dorsal nerves. The depot on each side must therefore be placed so that it reaches both the volar and the dorsal nerve — if it is placed dorsally alone, the pulp of the finger remains sensitive. Inject slowly and avoid forcing large volumes all the way round the finger, since it is the pressure itself, not the adrenaline, that puts the circulation at risk.

Procedure

Paronychia — incision and drainage

A digital block if the abscess is more than superficial.
Introduce a Freer elevator, small artery forceps or the back of a size 11 scalpel blade between the nail and the nail fold, parallel to the nail, and lift the fold off the nail plate.
A skin incision is usually not needed. With a large abscess pointing through the skin, an incision can be made parallel to the nail fold.
Express the pus and send it for culture.
If necessary, place a thin gauze wick under the fold for 24–48 hours.
If the abscess extends beneath the nail plate (subungual extension), the proximal or lateral part of the nail must be removed.

Antibiotics are given for surrounding cellulitis, immunosuppression or diabetes; the first choice is flucloxacillin, with anaerobic cover added after nail biting or oral contact.

Ingrown nail — splinting

Lift the lateral edge of the nail with artery forceps and slide a cotton wisp, a strip of suture material or a 1 cm length of a 2–3 mm drain beneath the edge with a sawing movement until the nail lifts free of the fold. It is changed daily after washing and removed once the inflammation has settled and the nail has grown beyond the fold.

Ingrown nail — partial avulsion

A digital block and a tourniquet.
Free the lateral 3–4 mm of the nail plate from the nail bed with an elevator, all the way in beneath the cuticle to the matrix.
Cut the nail longitudinally with a nail splitter, all the way to the base. If no splitter is available, use strong pointed scissors with upward pressure to spare the nail bed.
Grasp the segment with artery forceps close to the root and twist it away from the nail bed until it comes free from the fold and the cuticle.
Inspect to ensure that no spicules remain.
In recurrent disease: destroy the corresponding part of the matrix with phenol 88 % on a cotton bud for 30 seconds × 3, drying between applications, and then irrigate copiously with saline or alcohol. Phenol must not come into contact with the surrounding skin.
Release the tourniquet, check the circulation, apply antibiotic ointment and a non-adherent dressing.

Three panels of partial nail avulsion on a great toe: the elevator beneath the nail edge, the nail splitter cutting longitudinally, and the freed segment being twisted out while a cotton bud is advanced towards the matrix horn — Figure 3. Partial nail avulsion in three steps. First the lateral 3–4 mm of the nail plate is freed from the nail bed with an elevator advanced proximally right in beneath the cuticle — if it is not taken all the way, the root remains. The plate is then cut longitudinally with a nail splitter in a straight line all the way to the base. Finally the segment is grasped close to the root with artery forceps and twisted outwards so that it comes free of the fold, revealing the exposed nail bed and the lateral matrix horn; that is where the phenol-soaked cotton bud must reach, in beneath the proximal nail fold. The phenol is applied to a dry surface and then irrigated away copiously.

Subungual haematoma — trephination

Burn a hole through the nail plate with electrocautery or a red-hot paper clip, in the middle of the haematoma. The nail plate has no nerve supply; a block is rarely needed. Hold it in place until the blood has drained. With a concomitant fracture of the distal phalanx, trephination is still indicated, but the wound must then be regarded as an open fracture.

The dividing line lies at the nail plate, not at the size of the haematoma. The older rule that a haematoma involving more than 25 or 50 % of the nail surface requires nail avulsion and suture of the nail bed has not held up in follow-up studies: as long as the nail plate and the edges of the nail folds are intact, the appearance of the nail is just as good after trephination alone, whatever the extent of the haematoma and whether or not there is an underlying tuft fracture. Nail avulsion with inspection and suture of the nail bed is, however, indicated when

the nail plate is split, partly loosened or avulsed,
the edge of the nail fold is torn or the base of the nail plate lies on top of the nail fold,
there is a displaced fracture of the terminal phalanx requiring reduction.

A fingertip with a dark subungual haematoma and a cautery tip over the middle of the nail, together with a section showing the hole through the nail plate and the blood draining out — Figure 4. Trephination of a subungual haematoma. The hole is burned vertically through the nail plate directly over the darkest, most tense part of the haematoma. The section on the right shows why the procedure relieves the pain: the clot lies enclosed between the nail bed and the nail plate and lifts the plate, and it is the pressure in that closed space that hurts. The cautery must stop as soon as the plate has been penetrated — **it must not reach down into the nail bed**, which is the risk above all with thin nails and in children. One hole is usually enough; drain until the flow of blood stops and press gently on the nail plate.

Complications

Infection, at worst osteomyelitis of the distal phalanx — particularly in patients with diabetes.
Nail bed injury with permanent nail deformity.
Recurrence of the ingrown nail (10–30 % without matrix ablation, under 5 % with phenol).
An inclusion cyst in the nail fold.
Hyperkeratosis, oedema and persistent redness of the nail fold.
Digital ischaemia from a forgotten tourniquet — count the instruments and the tourniquet at the end.
Chemical burns of the surrounding skin from spilled phenol.

Aftercare and follow-up

Antibiotic ointment and a non-adherent dressing. After partial avulsion: soaks in lukewarm water 2–3 times daily from day one, with a daily change of dressing. Elevation and rest for the first 24 hours. Roomy shoes.

Inspect after 2–3 days with infection in mind. Phenol-treated wounds often weep for 2–4 weeks — this is expected and is not in itself a sign of infection.

Give instructions on cutting the nail straight across, not rounded at the corners, and on shoes that do not press. In patients with diabetes: refer for specialist foot care.

Common pitfalls

Insufficient waiting time after the block — always test with a needle tip.
No tourniquet, which gives a blood-filled field and spicules left behind.
The nail not cut all the way to the base — the single commonest cause of recurrence.
Incising a herpetic whitlow. Grouped vesicles and severe pain without pus — treat with aciclovir, do not incise.
A missed subungual melanoma behind a "haematoma" that does not grow out with the nail.
Nail avulsion merely because the haematoma is large. If the nail plate and the edge of the fold are intact, trephination is enough; if they are damaged, it is not enough however small the haematoma.
Phenol on healthy skin, or inadequate irrigation afterwards.
A diabetic foot without a vascular assessment — the procedure can start a chronic ulcer.

Nail procedures — paronychia, ingrown toenail and subungual haematoma