Perioperative Management and Anesthesia in Foot and Ankle Surgery

Comprehensive Introduction and Patho-Epidemiology

The evolution of foot and ankle surgery has been profoundly shaped by continuous, iterative advancements in perioperative management, particularly within the intersecting disciplines of regional anesthesia, hemostatic tourniquet control, and stringent infection prophylaxis. As the complexity of reconstructive procedures increases—ranging from extensive Charcot neuroarthropathy reconstructions and total ankle arthroplasties to minimally invasive percutaneous osteotomies—the modern orthopedic surgeon must possess a masterful, nuanced understanding of these foundational perioperative elements. The shift toward ambulatory surgery, driven by both economic pressures and enhanced recovery after surgery (ERAS) protocols, mandates an absolute optimization of the patient's physiological state prior to, during, and immediately following surgical intervention.

From an epidemiological perspective, the demographic landscape of foot and ankle pathology is rapidly shifting. The increasing global prevalence of diabetes mellitus, peripheral neuropathy, and peripheral arterial disease has dramatically elevated the baseline risk profile of patients presenting for pedal surgery. Consequently, the patho-epidemiology of perioperative complications—such as surgical site infections (SSIs), delayed wound healing, and thromboembolic events—has become a central focus of orthopedic research. The foot, with its unique microflora, terminal vascular arborization, and thin dorsal soft tissue envelope, represents a highly unforgiving anatomical environment where minor perioperative miscalculations can rapidly cascade into catastrophic morbidities, including deep-seated osteomyelitis or major limb amputation.

Historically, general anesthesia and prolonged postoperative opioid administration were the mainstays of perioperative care in this subspecialty. However, the contemporary opioid epidemic and a deeper understanding of nociceptive pathways have catalyzed a paradigm shift toward multimodal, opioid-sparing analgesic strategies heavily reliant on sophisticated regional anesthetic techniques. Furthermore, the biomechanical understanding of tourniquet-induced ischemia and reperfusion injury has evolved, prompting a reevaluation of traditional exsanguination protocols. This comprehensive chapter delineates the critical, evidence-based protocols required for optimizing patient outcomes, serving as an authoritative, exhaustive resource for orthopedic residents, fellows, and practicing consultants navigating the complex perioperative landscape of foot and ankle surgery.

To achieve consistent, reproducible excellence in surgical outcomes, the orthopedic surgeon must integrate these discrete perioperative variables into a cohesive, standardized protocol. This requires not only technical surgical dexterity but also an intimate understanding of the pharmacodynamics of local anesthetics, the rheology of venous stasis, and the microbiology of cutaneous biofilms. By mastering the patho-epidemiological principles that govern perioperative risks, the surgeon can preemptively mitigate complications, thereby ensuring the preservation of limb function, structural integrity, and the highest standards of patient safety.

Detailed Surgical Anatomy and Biomechanics

A profound comprehension of the descriptive and topographic anatomy of the foot and ankle is the absolute bedrock of safe surgical intervention, effective regional anesthesia, and complication avoidance. The complex neurovascular arborization in this distal extremity demands meticulous attention to anatomical variations, particularly when establishing surgical portals, designing extensile incisions, or depositing local anesthetics. The foot is innervated by five terminal branches derived from the sciatic and femoral nerves, each exhibiting distinct topographic territories and predictable, yet variable, anatomical courses that must be respected during dissection.

Peripheral Nerve Arborization and Topography

The superficial peroneal nerve (SPN) is notoriously vulnerable during anterolateral approaches to the ankle and hindfoot. Classic anatomical studies have demonstrated significant variability in its course; the SPN typically pierces the crural fascia to become subcutaneous approximately 10 to 15 centimeters proximal to the tip of the lateral malleolus. However, in a notable percentage of patients, the nerve may branch proximal to the ankle joint, or aberrant intermediate dorsal cutaneous branches may cross directly over the surgical intervals utilized for fibular fracture fixation or lateral ligament reconstruction. Transection of these branches invariably leads to the formation of recalcitrant, highly symptomatic postoperative neuromas.

Similarly, the sural nerve, formed by the convergence of the medial sural cutaneous nerve and the peroneal communicating branch, courses posterolaterally behind the lateral malleolus in close proximity to the small saphenous vein. Its location places it at high risk during the extensile lateral approach for calcaneal fractures or Achilles tendon repairs. On the medial aspect, the saphenous nerve—the sole terminal branch of the femoral nerve supplying the foot—arborizes anterior to the medial malleolus alongside the great saphenous vein. Deep to the flexor retinaculum, the tibial nerve bifurcates into the medial and lateral plantar nerves, providing the critical sensory innervation to the weight-bearing plantar surface and motor innervation to the intrinsic pedal musculature.

The Angiosome Concept in Foot and Ankle Surgery

Understanding the functional topography and vascular supply of the foot is essential for planning incisions that respect angiosomes and minimize devastating wound healing complications. The angiosome concept, pioneered by Taylor and Palmer, divides the foot and ankle into distinct three-dimensional blocks of tissue supplied by specific source arteries (the anterior tibial, posterior tibial, and peroneal arteries). Surgical incisions must be meticulously planned to either remain within a single angiosome or explicitly utilize the known anastomotic choke vessels between adjacent territories. The dorsal skin is exceptionally thin and pliable, accommodating significant postoperative edema but offering virtually no mechanical protection to the underlying extensor tendons and neurovascular bundles.

Biomechanics of Tourniquet Application

The biomechanical principles governing pneumatic tourniquet application are equally critical to perioperative safety. When a tourniquet is inflated, it exerts a compressive radial force that is transmitted through the soft tissues to the underlying neurovascular structures. The degree of tissue deformation is proportional to the applied pressure and the duration of inflation. Excessive pressure gradient differentials at the proximal and distal edges of the tourniquet cuff can induce significant shear stress on the myelin sheaths of peripheral nerves, precipitating neurapraxia or axonotmesis. Furthermore, prolonged ischemia alters the cellular biomechanics of the skeletal muscle distal to the cuff, leading to intracellular acidosis, depletion of adenosine triphosphate (ATP), and the accumulation of toxic oxygen free radicals upon reperfusion.

Exhaustive Indications and Contraindications

The selection of perioperative modalities, particularly regarding regional anesthesia and tourniquet utilization, requires a highly individualized risk-benefit analysis based on the patient's physiological reserves, the specific surgical pathology, and the anticipated duration of the procedure. While regional anesthesia and hemostatic tourniquets are universally employed in foot and ankle surgery, their application is not without inherent risks, and strict adherence to established indications and contraindications is paramount.

Selection of Regional Anesthesia Modalities

The popliteal fossa sciatic nerve block is the gold standard for major hindfoot, midfoot, and ankle reconstructions, providing profound intraoperative anesthesia and extended postoperative analgesia. It is explicitly indicated for highly painful, invasive procedures such as triple arthrodesis, total ankle arthroplasty, complex pilon fracture open reduction and internal fixation (ORIF), and extensive Charcot reconstructive osteotomies. Conversely, the comprehensive five-nerve ankle block is indicated for shorter, less invasive forefoot and midfoot procedures, such as hallux valgus correction, Weil osteotomies, or neurectomies, where proximal motor blockade of the leg is unnecessary and early ambulation is desired.

Tourniquet Utilization Criteria

A bloodless surgical field is imperative in foot and ankle surgery to identify delicate neurovascular structures, perform meticulous articular debridement, and ensure the optimal interdigitation of orthopedic implants and bone graft materials. Pneumatic tourniquets are indicated for nearly all major open reconstructive procedures of the lower extremity. However, their use is strictly contraindicated in patients with severe peripheral vascular disease (PVD), particularly those with an ankle-brachial index (ABI) of less than 0.45 or heavily calcified vessels (Mönckeberg's arteriosclerosis), where the compressive forces may fracture the calcified tunica media and precipitate acute arterial thrombosis.

Furthermore, tourniquets should be avoided or used with extreme caution in patients with sickle cell disease or trait, as the induced hypoxia, acidosis, and vascular stasis can trigger a catastrophic sickling crisis within the ischemic limb. Patients with a known history of severe peripheral neuropathy or pre-existing compressive neuropathies (e.g., tarsal tunnel syndrome) are also at an elevated risk for tourniquet-induced neurapraxia due to the "double crush" phenomenon, necessitating lower inflation pressures and strictly minimized ischemic times.

Pre-Operative Planning, Templating, and Patient Positioning

Thorough preoperative planning in foot and ankle surgery extends beyond radiographic templating of osteotomies and hardware selection; it encompasses a comprehensive physiological optimization of the patient, rigorous infection control protocols, and precise operative positioning. The preoperative phase is the critical window during which the surgeon must stratify the patient's risk for venous thromboembolism (VTE) and surgical site infections, implementing proactive measures to neutralize these threats before the first incision is made.

Preoperative Risk Stratification and DVT Prophylaxis

While the incidence of deep vein thrombosis (DVT) and pulmonary embolism (PE) following foot and ankle surgery is historically lower than that of major joint arthroplasty, it remains a critical medicolegal and clinical concern. Multicenter studies indicate that the overall incidence of symptomatic DVT in foot and ankle surgery ranges from 1% to 4%. The surgeon must utilize validated risk assessment models, such as the Caprini Risk Assessment Score, to stratify patients. High-risk factors include Achilles tendon ruptures (the highest risk category in this subspecialty), major hindfoot trauma, prolonged postoperative cast immobilization, obesity, prior history of VTE, and known thrombophilias.

Aggressive Skin Preparation and Biofilm Disruption

Surgical site infections (SSIs) can lead to catastrophic outcomes, including osteomyelitis, hardware failure, and amputation. The unique microflora of the foot, particularly within the interdigital web spaces and periungual folds, necessitates aggressive preoperative decontamination. The foot harbors a high density of resident flora, including Staphylococcus epidermidis, Staphylococcus aureus, and various Gram-negative bacilli and fungi. Studies evaluating preoperative skin preparation have definitively shown that chemical application alone is insufficient. The use of sterile bristles and alcohol-based solutions (e.g., Chlorhexidine gluconate in isopropyl alcohol) is significantly superior to standard aqueous iodine paints. The surgeon or assistant must mechanically scrub the foot, as mechanical friction disrupts the established biofilm and desquamates the dead stratum corneum, allowing the bactericidal agent to penetrate effectively.

Patient Positioning and Operating Room Setup

Patient positioning is dictated by the surgical approach and the chosen anesthetic modality. For posterior approaches to the Achilles tendon or the posterior malleolus, the patient is positioned prone, requiring meticulous padding of all bony prominences (e.g., the contralateral patella, anterior superior iliac spines, and face) to prevent decubitus ulcers and perioperative neuropathies. The lateral decubitus position is frequently utilized for extensile lateral approaches to the calcaneus or isolated fibular fixation. In all positions, a well-padded radiolucent triangle or bump is essential to elevate the operative extremity, facilitating unencumbered fluoroscopic imaging and allowing the surgeon circumferential access to the foot and ankle. When utilizing ultrasound-guided regional anesthesia, the room must be ergonomically configured so that the anesthesiologist has a direct line of sight to the ultrasound monitor while maintaining sterile technique.

Step-by-Step Surgical Approach and Fixation Technique

Although the execution of osteotomies and hardware placement constitutes the mechanical core of foot and ankle surgery, the "surgical approach" fundamentally begins with the precise, step-by-step execution of the regional anesthetic block and the systematic application of the hemostatic tourniquet. The integration of these perioperative techniques creates the optimal physiological environment—a painless, bloodless field—that permits meticulous anatomical dissection and rigid internal fixation.

Ultrasound-Guided Popliteal Sciatic Nerve Block

The execution of the popliteal sciatic nerve block requires high-frequency linear ultrasound guidance to ensure precise deposition of the local anesthetic while avoiding intraneural injection. The patient is typically positioned prone or in the lateral decubitus position. The ultrasound transducer is placed transversely across the popliteal fossa, identifying the pulsatile popliteal artery. Superficial and lateral to the artery, the sciatic nerve is visualized as a hyperechoic, honeycomb-like structure. The transducer is tracked proximally until the bifurcation of the tibial and common peroneal nerves converges into the unified sciatic nerve (typically 5 to 10 cm proximal to the popliteal crease). Using an in-plane technique, an echogenic block needle is advanced through the biceps femoris muscle. The local anesthetic (e.g., 20-30 mL of 0.5% Ropivacaine) is injected deep to the paraneural sheath, creating a circumferential "donut sign" around the nerve, ensuring rapid onset and dense blockade.

The Comprehensive Five-Nerve Ankle Block

For forefoot surgical approaches, the ankle block provides targeted anesthesia without proximal motor compromise. This technique involves the systematic blockade of the five terminal nerves at the level of the malleoli.
1. Tibial Nerve: Blocked posterior to the medial malleolus, deep to the flexor retinaculum, adjacent to the posterior tibial artery using 5-7 mL of anesthetic.
2. Deep Peroneal Nerve: Blocked at the anterior ankle joint line, traversing between the tendons of the extensor hallucis longus (EHL) and extensor digitorum longus (EDL), lateral to the dorsalis pedis artery.
3. Superficial Peroneal Nerve: Blocked via a superficial subcutaneous wheal extending from the anterior tibial crest to the lateral malleolus.
4. Sural Nerve: Blocked via a subcutaneous injection between the lateral malleolus and the lateral border of the Achilles tendon.
5. Saphenous Nerve: Blocked via a subcutaneous wheal anterior to the medial malleolus, adjacent to the great saphenous vein. Meticulous aspiration prior to injection is mandatory to prevent intravascular administration.

Hemostatic Tourniquet Application and Calibration

Following the establishment of regional anesthesia, the surgical field is prepped, and the tourniquet is applied to facilitate the surgical approach and subsequent hardware fixation. The choice between an ankle and a calf tourniquet depends on the proximal extent of the planned incision. A well-padded cast padding layer is applied smoothly to prevent skin blistering or pinching. The modern standard dictates basing the tourniquet inflation pressure on the patient's Limb Occlusion Pressure (LOP) or systolic blood pressure (typically Systolic BP + 100 mmHg for the lower extremity), resulting in pressures between 225 and 250 mmHg. Prior to inflation, the limb is strictly exsanguinated using an Esmarch bandage to minimize venous engorgement, which obscures surgical planes and complicates the identification of delicate fascial intervals during the surgical approach.

Once the bloodless field is achieved, the surgeon can proceed with the definitive surgical approach, utilizing atraumatic soft tissue handling. The absence of hemorrhage allows for precise identification of the neurovascular bundles, optimal preparation of arthrodesis surfaces, and the meticulous application of internal fixation constructs (e.g., locking plates, compression screws) without the interference of pooled blood, which can compromise the bone-implant interface and obscure fluoroscopic visualization.

Complications, Incidence Rates, and Salvage Management

Despite meticulous adherence to perioperative protocols, complications related to anesthesia, tourniquet use, and thromboembolism can occur. The orthopedic surgeon must be highly vigilant, capable of rapidly diagnosing these adverse events, and proficient in executing immediate salvage management protocols to prevent long-term morbidity or mortality.

Local Anesthetic Systemic Toxicity and Neurological Deficits

Local Anesthetic Systemic Toxicity (LAST) is a rare but potentially fatal complication resulting from the inadvertent intravascular injection or rapid systemic absorption of local anesthetics. It manifests as progressive central nervous system excitation (perioral numbness, tinnitus, seizures) followed by cardiovascular collapse and refractory arrhythmias. Immediate salvage management requires the cessation of anesthetic administration, securing the airway, and the prompt intravenous administration of 20% lipid emulsion therapy (Intralipid) to act as a "lipid sink," sequestering the lipophilic anesthetic molecules away from myocardial and cerebral receptors. Peripheral nerve injuries, ranging from transient neurapraxia to permanent axonotmesis, can occur secondary to direct needle trauma, intraneural injection, or tourniquet compression.

Tourniquet-Induced Ischemia and Reperfusion Injury

Prolonged tourniquet times (exceeding 120 minutes) significantly increase the risk of ischemic reperfusion injury, deep vein thrombosis, and postoperative compartment syndrome. Upon deflation, the sudden reperfusion of the ischemic limb releases a profound load of acidic metabolites, potassium, and myoglobin into the systemic circulation, which can transiently depress myocardial contractility. In the local soft tissue envelope, reperfusion triggers an intense inflammatory cascade, leading to massive interstitial edema that can compromise wound closure and precipitate wound dehiscence or necrosis.

Phased Post-Operative Rehabilitation Protocols

The immediate and intermediate postoperative phases require a highly structured, delicate balance between protecting the surgical repair, managing nociception, and initiating progressive rehabilitation. The presence of a regional anesthetic block introduces unique biomechanical and proprioceptive challenges that must be explicitly addressed in the postoperative protocol to prevent inadvertent structural failure of the operative construct.

Immediate Postoperative Phase and Proprioceptive Deafferentation

Surgeons must be acutely aware of the profound biomechanical and proprioceptive deficits induced by regional anesthesia. Anesthetic blockade of the sciatic or tibial nerves not only eliminates nociception but also completely abolishes proprioception by blocking the afferent signals from the ligamentous, capsular, and musculotendinous mechanoreceptors. Patients discharged with an active popliteal or ankle block have a completely insensate, "dead" leg, characterized by a significantly diminished sense of joint position in space. This functional deafferentation drastically increases the risk of falls and inadvertent, catastrophic weight-bearing on a newly reconstructed limb or fragile osteotomy. Mitigation requires strict non-weight-bearing instructions, mandatory physical therapy clearance utilizing crutches or a knee scooter, and the application of a rigid, well-padded protective splint or bivalved cast prior to discharge.

Analgesic Transition and Rebound Pain Mitigation

As the regional block begins to resolve (typically 18 to 24 hours postoperatively for a single-shot popliteal block), patients are at a high risk of experiencing severe, precipitous "rebound pain." This phenomenon occurs as the dense sensory blockade rapidly dissipates, exposing the central nervous system to a sudden barrage of unmitigated nociceptive input from the surgical site. To prevent this, a preemptive, multimodal oral analgesic regimen must be initiated before the block wears off. This protocol typically includes scheduled acetaminophen, non-steroidal anti-inflammatory drugs (NSAIDs) if not contraindicated by bone healing concerns, and membrane-stabilizing agents such as gabapentin or pregabalin. Short-acting oral opioids are reserved exclusively for breakthrough pain.

Progressive Weight-Bearing and Functional Restoration

Once the soft tissue envelope has healed and the surgical incisions are sealed (typically 2 to 3 weeks postoperatively), the patient transitions from a rigid cast to a removable controlled ankle motion (CAM) boot. Early, protected range of motion exercises are initiated to prevent capsular contracture and tendon adhesions, particularly following Achilles tendon repairs or periarticular fracture fixations. The progression of weight-bearing is strictly dictated by radiographic evidence of osseous union and the biomechanical stability of the internal fixation construct. Physical therapy focuses on restoring intrinsic foot muscle strength, normalizing the gait cycle, and retraining the proprioceptive pathways that were transiently disrupted during the perioperative period.

Summary of Landmark Literature and Clinical Guidelines

The contemporary practice of perioperative management in foot and ankle surgery is firmly rooted in a robust foundation of evidence-based literature and consensus guidelines established by premier orthopedic and anesthesiology societies. Mastery of these guidelines is essential for standardizing care, minimizing medicolegal liability, and optimizing patient outcomes.

Consensus on Regional Anesthesia and Infection Control

The American Society of Regional Anesthesia and Pain Medicine (ASRA) provides definitive guidelines regarding the performance of regional blocks in patients receiving antithrombotic therapy, dictating precise time intervals for catheter placement and removal to prevent epidural or peripheral hematomas. Landmark anatomical studies, such as those by Adkinson et al., have mapped the highly variable arborization of the superficial peroneal nerve, forming the anatomical basis for the blunt dissection techniques universally taught in modern orthopedic residency programs. Regarding infection control, the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) strongly advocate for the use of alcohol-based chlorhexidine solutions over aqueous povidone-iodine, supported by numerous randomized controlled trials demonstrating superior eradication of the cutaneous biofilm and a statistically significant reduction in SSI rates in lower extremity surgery.

Evidence-Based Venous Thromboembolism Prophylaxis

The American College of Chest Physicians (ACCP) and the American Academy of Orthopaedic Surgeons (AAOS) have published extensive, evidence-based clinical practice guidelines regarding the prevention of VTE in orthopedic surgery. While routine chemical prophylaxis is not universally mandated for isolated, ambulatory forefoot procedures in healthy patients, the guidelines strongly recommend risk stratification using tools like the Caprini score. For high-risk scenarios—such as Achilles tendon ruptures, major trauma, or patients with a history of prior VTE undergoing prolonged immobilization—the administration of low-molecular-weight heparin (LMWH) or direct oral anticoagulants (DOACs) is strongly recommended, balanced carefully against the risk of postoperative hematoma formation.

By integrating these advanced regional anesthesia techniques, employing safe and calibrated tourniquet protocols, executing meticulous skin preparation, and rigorously stratifying thromboembolic risks, the orthopedic surgeon establishes the optimal physiological environment for surgical success. Adherence to these textbook principles ensures not only the preservation of limb function and structural integrity but also the highest standards of patient safety and rapid postoperative recovery.