INTRODUCTION TO FOOT AND ANKLE OPERATIVE TECHNIQUES

The successful execution of foot and ankle surgery demands a profound understanding of regional anatomy, meticulous preoperative planning, and precise intraoperative execution. Unlike other orthopedic subspecialties, the foot and ankle present unique challenges, including a complex biomechanical architecture, a high density of neurovascular structures within confined compartments, and a cutaneous envelope that is notoriously difficult to sterilize. This comprehensive guide expands upon foundational surgical techniques, detailing evidence-based protocols for preoperative skin preparation, tourniquet management, regional anesthesia, and prophylactic anticoagulation.

PREOPERATIVE PREPARATION AND SKIN ANTISEPSIS

The human foot harbors a dense and diverse microbiome, particularly within the interdigital web spaces and periungual folds. Consequently, achieving adequate skin antisepsis is a critical prerequisite for minimizing surgical site infections (SSIs).

Evidence-Based Skin Preparation Protocols

Historically, a variety of solutions and application methods have been utilized, ranging from povidone-iodine (PI) scrubs to chlorhexidine gluconate (CHG) in isopropyl alcohol. Recent quantitative and qualitative analyses have provided clarity on the most efficacious regimens.

A synthesis of landmark studies (Cheng et al., Keblish et al., Bibbo et al., and Ostrander et al.) reveals distinct advantages of alcohol-based solutions over traditional aqueous iodine:
* Cheng et al. (2009): In a quantitative analysis of 50 patients undergoing forefoot surgery, the authors compared 1% PI with 23% isopropyl alcohol against 0.5% CHG with 70% isopropyl alcohol. The CHG-alcohol combination demonstrated superior bacterial eradication, particularly in the challenging interdigital spaces.
* Ostrander et al.: Evaluated 125 patients using either 0.7% PI with 74% isopropyl alcohol or 2% CHG with 70% isopropyl alcohol. Both alcohol-based solutions significantly outperformed aqueous solutions, yielding a postoperative infection rate of 0% in the optimized cohorts compared to 7.5% in historical controls using non-alcohol-based preps.
* Application Technique: The debate between "scrubbing and painting" versus "painting only" has largely been settled. Keblish and Bibbo demonstrated that a meticulous 3- to 5-minute scrub followed by painting provides optimal bacterial load reduction, particularly when utilizing chloroxylenol or CHG preparations.

Clinical Pearl: The Web Space Challenge
The interdigital web spaces are the most common sites for residual bacterial colonization post-preparation. Surgeons must ensure that the prep sponge or applicator aggressively debrides the desquamated epithelium in these clefts. A preliminary alcohol prewash is highly recommended for visibly soiled or hyperkeratotic feet.

TOURNIQUET MANAGEMENT AND EXSANGUINATION

A bloodless operative field is indispensable in foot and ankle surgery to identify delicate neurovascular bundles, perform precise osteotomies, and ensure optimal cement interdigitation or hardware placement. However, tourniquet application is not benign; it carries risks of neurovascular neurapraxia, muscle ischemia, and systemic hemodynamic shifts.

Esmarch Bandage Exsanguination and Tourniquet

For procedures distal to the mid-calf, an Esmarch bandage can serve dual purposes: exsanguination and acting as a primary tourniquet. This technique permits most forefoot and midfoot procedures to be performed in a bloodless field for up to 2 hours.

Grebing and Coughlin rigorously evaluated the sub-bandage pressures generated by 4-inch and 6-inch elastic rubber bandages (Esmarch) applied around the ankle. Their methodology involved tensioned wraps followed by tucking the remainder of the bandage beneath the proximal end:
* Three Wraps with a Tuck: Produced an average pressure of 222 mm Hg (range, 146 to 319 mm Hg).
* Four Wraps with a Tuck: Generated an average pressure of 288 mm Hg (range, 202 to 405 mm Hg).

The investigators concluded that this technique is highly effective and safe, provided the tourniquet does not encroach upon the musculotendinous junction at the distal third of the leg, which could cause tethering and subsequent muscle necrosis or nerve compression. A survey of the American Orthopaedic Foot & Ankle Society (AOFAS) indicated that 73% of surgeons routinely utilize an elastic bandage for exsanguination.

Pneumatic Tourniquets: Ankle, Calf, and Thigh

When a pneumatic tourniquet is preferred, the surgeon must select the optimal site based on the surgical approach and the planned anesthesia.

• Ankle and Calf Tourniquets: These are highly convenient and generally well-tolerated under local or regional anesthesia. Rudkin et al. audited 1,000 patients undergoing foot and ankle surgery with ankle block anesthesia and an ankle cuff tourniquet. They confirmed the method's safety but issued a critical caveat: patients older than 70 years were at a 3.5 times greater risk of experiencing tourniquet pain compared to younger cohorts.
• Thigh Tourniquets: While providing excellent exsanguination for hindfoot and ankle reconstruction, thigh tourniquets are notoriously poorly tolerated under local or distal regional anesthesia. The ischemic pain transmitted via unmyelinated C-fibers typically limits thigh tourniquet tolerance to 30–45 minutes in an awake patient, necessitating deep sedation, spinal, or general anesthesia for longer cases.

Surgical Warning: Tourniquet Pressures
Never use a "one size fits all" pressure setting. Pneumatic tourniquets should be inflated to 100–150 mm Hg above the patient's systolic blood pressure for the lower extremity. For ankle tourniquets, a pressure of 250 mm Hg is standard for normotensive adults, but this must be titrated down for frail or elderly patients to prevent crush injury to the superficial peroneal and saphenous nerves.

REGIONAL ANESTHESIA IN FOOT AND ANKLE SURGERY

Regional anesthesia has revolutionized foot and ankle surgery, offering superior postoperative analgesia, reduced opioid consumption, and earlier discharge in the ambulatory setting.

Forefoot Block

The forefoot block is ideal for localized procedures such as hammertoe corrections, neuroma excisions, and simple bunionectomies. It involves infiltrating local anesthetic (typically a 50/50 mixture of 1% lidocaine and 0.5% bupivacaine without epinephrine) in a ring-like fashion proximal to the surgical site.

• Technique: The needle is introduced dorsally, targeting the dorsal digital nerves, and advanced plantarly to anesthetize the plantar digital nerves.
• Volume: Typically, 3 to 5 mL of anesthetic per web space is sufficient. Care must be taken to avoid excessive volume, which can cause compartment syndrome of the digit or vascular compromise due to mechanical compression.

Ankle Block

The ankle block provides comprehensive anesthesia to the entire foot and is the workhorse for midfoot and forefoot reconstructions. It requires the systematic blockade of five distinct terminal nerve branches.

1. Tibial Nerve: The largest and most critical nerve, supplying the plantar aspect of the foot. It is blocked posterior to the medial malleolus, deep to the flexor retinaculum, adjacent to the posterior tibial artery.
2. Deep Peroneal Nerve: Supplies the first web space and deep structures of the midfoot. It is blocked at the anterior ankle joint line, lateral to the extensor hallucis longus (EHL) tendon and medial to the dorsalis pedis artery.
3. Superficial Peroneal Nerve: Supplies the dorsum of the foot. It is blocked via a subcutaneous wheal extending from the anterior tibial crest to the lateral malleolus.
4. Sural Nerve: Supplies the lateral margin of the foot. It is blocked posterior to the lateral malleolus, adjacent to the small saphenous vein.
5. Saphenous Nerve: Supplies the medial margin of the foot. It is blocked anterior to the medial malleolus, adjacent to the great saphenous vein.

Pitfall: Ankle Block Failure
The most common reason for an incomplete ankle block is failure to adequately bathe the tibial nerve within the tarsal tunnel. Ensure the needle penetrates the flexor retinaculum; a distinct "pop" is often felt. Aspiration is mandatory to avoid intravascular injection into the posterior tibial artery or accompanying veins.

Popliteal Sciatic Nerve Block

For complex hindfoot reconstructions, ankle arthrodesis, or Achilles tendon repairs, the popliteal sciatic nerve block is the gold standard. It provides profound anesthesia and prolonged postoperative analgesia, and crucially, it covers the tourniquet pain associated with calf tourniquets.

Prone Approach

• Anatomy: The sciatic nerve typically bifurcates into the tibial and common peroneal nerves 5 to 10 cm proximal to the popliteal crease.
• Technique: With the patient prone, the apex of the popliteal fossa is identified (bounded by the biceps femoris laterally and the semimembranosus/semitendinosus medially). Using ultrasound guidance, the needle is introduced out-of-plane or in-plane to target the sciatic nerve just proximal to its bifurcation.
• Advantage: Excellent visualization of the nerve and surrounding vasculature.

Lateral Approach

• Indication: Ideal for patients who cannot be positioned prone (e.g., severe obesity, advanced pregnancy, or unstable spinal fractures).
• Technique: With the patient supine, the leg is internally rotated. The needle is introduced through the lateral thigh, anterior to the biceps femoris tendon, and directed medially toward the sciatic nerve. Ultrasound is highly recommended to gauge depth and avoid the popliteal vessels.

PROPHYLACTIC ANTICOAGULATION

Although routine prophylactic postoperative anticoagulation is universally recommended after major hip or knee arthroplasty, its use after foot and ankle surgery remains a topic of nuanced debate.

Current Guidelines and Risk Stratification

The American College of Chest Physicians (ACCP) and the American Academy of Orthopaedic Surgeons (AAOS) generally advise against routine chemical deep vein thrombosis (DVT) prophylaxis for isolated foot and ankle surgery in patients without specific risk factors. The baseline risk of symptomatic venous thromboembolism (VTE) following foot and ankle surgery is remarkably low, estimated at 0.5% to 1.5%.

However, chemical prophylaxis (e.g., Low Molecular Weight Heparin [LMWH], direct oral anticoagulants [DOACs], or aspirin) should be strongly considered in the presence of compounding risk factors:
1. Patient-Specific Factors: History of prior DVT or pulmonary embolism (PE), known thrombophilia (e.g., Factor V Leiden), active malignancy, obesity (BMI > 30), age > 60 years, or current use of oral contraceptives/hormone replacement therapy.
2. Procedure-Specific Factors: Achilles tendon rupture repairs, major hindfoot trauma (e.g., calcaneus or pilon fractures), and procedures requiring prolonged non-weight-bearing cast immobilization.

Clinical Pearl: The Caprini Risk Assessment
Utilize a modified Caprini Risk Assessment Model for all foot and ankle patients. For patients scoring in the "high risk" category, a 14- to 28-day course of LMWH (e.g., Enoxaparin 40 mg daily) or Aspirin 81 mg twice daily is recommended, balancing the risk of VTE against the risk of postoperative wound hematoma and subsequent infection.

POSTOPERATIVE PROTOCOLS AND RECOVERY

The culmination of excellent preoperative preparation, precise tourniquet use, and effective regional anesthesia is a smooth postoperative recovery.

1. Elevation: Strict elevation of the operative extremity above the level of the heart is mandatory for the first 48 to 72 hours to minimize edema, reduce tension on the surgical incision, and mitigate throbbing pain.
2. Analgesia: The transition from regional block to oral analgesics must be preemptive. Patients should be instructed to take their first dose of oral analgesia (e.g., acetaminophen, NSAIDs, or a short course of opioids) before the regional block completely wears off, typically 12 to 18 hours postoperatively for a popliteal block.
3. Mobilization: Early, safe mobilization is the most effective form of DVT prophylaxis. Even if the patient is non-weight-bearing on the operative extremity, active range of motion of the knee and hip, combined with upper extremity conditioning, should be encouraged immediately post-surgery.

By adhering to these rigorous, evidence-based surgical techniques, the orthopedic surgeon can consistently achieve superior clinical outcomes, minimize perioperative complications, and ensure the highest standard of patient care in foot and ankle surgery.