INTRODUCTION AND HISTORICAL CONTEXT
The complete excision of the nail plate and germinal matrix—frequently referred to in the literature as the Zadik or Fowler procedure—is a definitive surgical intervention for chronic, refractory pathologies of the perionychium. Originally described by Quenu in 1887 and subsequently popularized by Wilson in 1944, this technique is designed to permanently halt the growth of the true nail plate while preserving the distal sterile matrix and the underlying osseous architecture of the distal phalanx.
Unlike radical amputations such as the terminal Syme procedure, which involves the resection of the distal half of the distal phalanx, the germinal matrix removal procedure preserves the length and biomechanical integrity of the hallux. The essential principle of this operation is the meticulous, complete extirpation of the germinal matrix (the primary source of nail plate generation) without disturbing the sterile matrix distal to the lunula.
Clinical Pearl: The sterile matrix does not generate a true, hard keratinous nail plate. Instead, following the removal of the germinal matrix, the retained sterile matrix undergoes squamous metaplasia and continues to form flaky cornifications. While functionally protective, this pseudo-nail can be cosmetically displeasing, making preoperative patient counseling an absolute necessity.
SURGICAL ANATOMY AND BIOMECHANICS
A profound understanding of the perionychial anatomy is mandatory to execute this procedure successfully and avoid the most common complication: recurrence of nail spicules.
The Perionychium
The perionychium consists of the nail bed (matrix), the nail fold (eponychium and paronychium), and the hyponychium.
* Germinal Matrix: Located proximal to the lunula and extending deep beneath the proximal nail fold. It is responsible for generating approximately 90% of the nail plate's volume. The germinal matrix curves sharply around the lateral aspects of the distal phalanx, forming deep lateral recesses (horns).
* Sterile Matrix: Extends from the distal edge of the lunula to the hyponychium. It contributes minimally to the thickness of the nail plate but is primarily responsible for the adherence of the nail plate to the underlying bed.
* Eponychium: The dorsal skin fold that covers the proximal aspect of the nail plate and germinal matrix.
* Extensor Hallucis Longus (EHL): The EHL tendon inserts into the dorsal base of the distal phalanx. Its insertion lies mere millimeters proximal to the proximal reflection of the germinal matrix.
Surgical Warning: The proximity of the EHL insertion to the proximal germinal matrix places the tendon at risk during the proximal dissection. Overly aggressive sharp dissection in the central proximal wound can lead to partial or complete EHL laceration, resulting in an extensor lag of the interphalangeal joint.
INDICATIONS AND PATIENT SELECTION
This procedure is generally reserved as a salvage operation when conservative measures and partial matricectomies (e.g., Winograd or Frost procedures) have failed. It is rarely utilized as a first-line treatment due to the permanent cosmetic alteration of the digit.
Primary Indications
- Recurrent Onychocryptosis (Ingrown Toenail): Multiple failed partial nail avulsions with chemical or surgical matricectomy.
- Onychogryposis: Severe "ram's horn" deformity of the nail, typically seen in the elderly, which causes pain, limits footwear options, and is refractory to routine podiatric debridement.
- Severe Onychomycosis: Fungal infections of the nail plate that are painful, cause severe dystrophy, and have failed or are contraindicated for systemic antifungal therapy.
- Pincer Nail Deformity (Incurvatum): Severe transverse overcurvature of the nail plate causing chronic pain and soft tissue impingement.
Ideal Candidates
- Middle-aged or Elderly Patients: Individuals with multiple occurrences of nail problems from a variety of causes who prioritize pain relief and functional footwear over cosmesis.
- Younger Patients (Predominantly Male): Patients who have endured multiple failed operations for ingrown toenails, have minimal concern for the cosmetic appearance of the toe, and desire a definitive cure without the bone shortening associated with a terminal Syme amputation.
Contraindications
- Severe Peripheral Arterial Disease (PAD): Ischemia compromises wound healing and increases the risk of digital gangrene. Non-invasive vascular studies (ABIs, toe pressures) should be obtained if vascular compromise is suspected.
- Active Soft Tissue Infection: While the procedure can be performed in the presence of gross infection, it is highly recommended to treat acute paronychia with antibiotics and partial avulsion first to reduce the bacterial load and optimize the surgical field.
- High Cosmetic Expectations: Patients who expect a normal-appearing toe postoperatively are poor candidates.
PREOPERATIVE PLANNING AND COUNSELING
The cornerstone of preoperative preparation for germinal matrix removal is managing patient expectations. The surgeon must explicitly inform the patient that the new "nail" over the sterile matrix will not look or grow like the previous normal nail.
The retained sterile matrix will produce a hyperkeratotic, flaky cornification. This pseudo-nail acts as a biological dressing over the distal phalanx but lacks the smooth, hard, translucent qualities of a true nail plate. Documenting this conversation in the preoperative consent is medicolegally imperative.
SURGICAL TECHNIQUE
The following technique details the meticulous sharp dissection required to achieve complete germinal matrix eradication.
1. Anesthesia and Positioning
- The patient is placed in the supine position.
- A digital block is performed using a long-acting local anesthetic (e.g., 0.5% bupivacaine mixed with 1% lidocaine). The use of epinephrine in digital blocks is generally safe based on modern evidence, but plain anesthetic combined with a mechanical tourniquet remains the traditional textbook standard.
- A digital tourniquet (e.g., a sterile Penrose drain or a commercial digital ring tourniquet) is applied to the base of the hallux to provide a bloodless surgical field. Exsanguination is achieved by elevating the digit or wrapping it with an Esmarch bandage prior to tourniquet inflation/clamping.
2. Nail Plate Avulsion
- Remove the entire nail plate initially.
- Introduce a Freer elevator or a straight hemostat under the distal free edge of the nail plate.
- Gently advance the instrument proximally, separating the nail plate from the underlying sterile and germinal matrices.
- Sweep the elevator dorsally to free the nail plate from the overlying eponychium.
- Grasp the nail plate with a heavy hemostat or needle driver and remove it with a rolling motion to avoid tearing the underlying bed.
3. Eponychial Flap Elevation
- Raise the eponychium as a full-thickness flap to expose the underlying proximal germinal matrix.
- Create two oblique incisions extending from both corners of the proximal nail fold. These incisions should extend approximately 1 cm proximally, angling slightly outward.
- Carefully elevate the dorsal skin flap (eponychium) off the underlying germinal matrix. Retract this flap proximally using fine skin hooks or a stay suture.
4. Lateral Nail Fold Excision
- Excise the inner 1 to 2 mm of the nail fold on both the medial and lateral sides of the nail. This removes hypertrophied granulation tissue and ensures adequate exposure of the lateral matrix horns.
5. Germinal Matrix Excision
- Defining the Distal Margin: Begin the transverse incision 1 to 2 mm distal to the lunula. If the lunula is indistinct or obscured by pathology, begin the incision one-third of the distance from the cuticle to the distal nail edge. Make this incision transversely across the sterile matrix, cutting down to the periosteum of the distal phalanx.
- Lateral Dissection: Retracting the lateral nail fold, remove each edge of the matrix from the distal phalanx by sharp dissection.
- The Lateral Recesses: The matrix follows the lateral curvature of the phalanx almost to the midlateral line. This anatomical nuance must be kept in mind during the lateral dissection. Failure to remove the germinal matrix deep within these lateral grooves is the most common cause of postoperative nail spicule formation.
- Proximal Dissection: With the distal edge and both lateral margins of the germinal matrix detached from the phalanx, the proximal edge and corners can be visualized clearly. Retract the proximal nail fold (eponychial flap) further proximally.
- Complete the removal of the matrix by sharp dissection, elevating it off the bone from distal to proximal.
Pitfall: Leaving microscopic remnants of the germinal matrix in the proximal corners (lateral horns) will inevitably lead to the growth of painful, cosmetically displeasing nail spicules that require revision surgery.
6. Periosteal Excision and EHL Protection
- The insertion of the extensor hallucis longus centrally, as well as the fat and subcutaneous tissue at the proximal corners, must be exposed before adequate excision of the germinal matrix is possible.
- Identify and protect the EHL tendon.
- To ensure absolute eradication of matrix cells, the periosteum on the dorsal and lateral borders of the distal phalanx should be removed by sharp dissection in conjunction with the germinal matrix. Scraping the bone with a curette or a periosteal elevator provides an additional layer of security against recurrence.
7. Closure
- Release the digital tourniquet and achieve hemostasis.
- Return the eponychial flap to its previous anatomical location.
- Usually, the advanced eponychial flap does not completely reach the remaining sterile nail bed, leaving a small transverse gap. This gap is clinically insignificant and quickly closes via secondary intention and wound contraction.
- The use of sutures to secure the corners of the eponychial flap is optional. If used, 4-0 or 5-0 non-absorbable sutures (e.g., nylon) are placed at the apices of the oblique incisions.
POSTOPERATIVE CARE AND REHABILITATION
Meticulous postoperative care is essential to ensure uncomplicated secondary healing of the exposed sterile matrix and the eponychial gap.
Immediate Postoperative Phase (0 to 48 Hours)
- Dressing: A nonadherent dressing (e.g., Xeroform, Adaptic, or a silicone contact layer) is applied directly over the exposed sterile matrix and surgical incisions. This is covered with a gently rolled gauze wrap and secured with a mild compressive bandage.
- Elevation: The patient is instructed to keep the foot strictly elevated above the level of the heart for the first 48 hours to minimize edema, throbbing pain, and postoperative bleeding.
- Weight-Bearing: Weight-bearing as tolerated in a rigid-soled, open-toe postoperative shoe is permitted, though ambulation should be minimized initially.
Subacute Phase (48 Hours to 2 Weeks)
- At 48 hours, the initial surgical dressing is removed.
- Hydrotherapy: Warm water soaks (often with Epsom salts or dilute chlorhexidine/povidone-iodine, depending on surgeon preference) are initiated for 15 to 20 minutes, twice daily. This promotes the mechanical debridement of exudate and prevents the nonadherent dressing from desiccating and adhering to the raw wound bed.
- Following each soak, the toe is patted dry, and a fresh nonadherent dressing and light gauze wrap are applied.
- If sutures were utilized for the eponychial flap, they are typically removed at 10 to 14 days postoperatively.
Long-Term Healing (2 to 8 Weeks)
- The patient continues to wear an open-toe shoe with a light dressing over the phalanx to protect the highly sensitive, healing sterile matrix from friction.
- The sterile matrix will gradually undergo hyperkeratosis, transitioning from a raw, weeping surface to a dry, flaky, cornified layer.
- Infection Considerations: If the procedure was performed in the presence of gross infection or severe paronychia, the inflammatory phase of wound healing may be prolonged. Healing may be delayed but should be complete by 6 to 8 weeks.
COMPLICATIONS AND MANAGEMENT
While highly successful when performed with meticulous technique, germinal matrix removal carries specific risks that the orthopedic surgeon must be prepared to manage.
1. Nail Spicule Recurrence
The most frequent complication is the regrowth of a nail spicule, usually arising from the lateral horns of the proximal germinal matrix. This occurs due to inadequate sharp dissection deep within the lateral recesses of the distal phalanx.
* Management: Symptomatic spicules require revision surgery. The specific area of recurrence is excised under local anesthesia, often supplemented with chemical matrixectomy (e.g., 89% phenol or 10% sodium hydroxide application) or electrocautery to destroy the residual matrix cells.
2. Postoperative Infection
Given that many of these procedures are performed on toes with a history of chronic paronychia or onychomycosis, superficial surgical site infections can occur.
* Management: Local wound care, increased frequency of warm soaks, and targeted oral antibiotic therapy based on local antibiograms (covering Staphylococcus aureus and common skin flora).
3. Extensor Hallucis Longus (EHL) Laceration
As previously noted, overly aggressive proximal dissection can sever the EHL insertion.
* Management: If recognized intraoperatively, the tendon should be primarily repaired to the distal phalanx using suture anchors or transosseous sutures. If recognized postoperatively as a chronic extensor lag, conservative management with a splint is often sufficient, as the functional deficit during normal gait is usually minimal, though surgical reconstruction may be considered in high-demand patients.
4. Epidermal Inclusion Cysts
Rarely, fragments of the germinal matrix or eponychial epidermis may be buried during the closure or healing process, leading to the formation of a painful epidermal inclusion cyst beneath the eponychial fold.
* Management: Surgical excision of the cyst and any associated matrix remnants.
