Operative Orthopaedics: Principles of Foot and Ankle Surgical Techniques

SURGICAL TECHNIQUES IN FOOT AND ANKLE ORTHOPAEDICS

The successful execution of foot and ankle surgery requires a profound understanding of regional anatomy, meticulous preoperative planning, and an uncompromising adherence to sterile technique. The foot presents a unique surgical environment; its dependent position, specialized glabrous skin, and high density of bacterial colonization demand specialized protocols for preoperative preparation, intraoperative hemostasis, and soft tissue handling. This comprehensive guide details the evidence-based principles of surgical preparation, operating room ergonomics, and tourniquet management essential for the modern orthopaedic surgeon.

PREOPERATIVE PREPARATION AND SKIN ANTISEPSIS

The normal bacterial flora residing on the foot presents a formidable challenge in orthopaedic surgery. The interdigital web spaces are particularly problematic, as they are frequently moist due to confinement in hosiery and occlusive footwear, creating an ideal microenvironment for bacterial proliferation. Furthermore, bacteria reside in dense colonies deep within the thick stratum corneum of the plantar surface, within the follicles of sebaceous glands, and along the hair shafts of the dorsal foot.

Ward and Pre-Induction Preparation

To mitigate the risk of surgical site infection (SSI), rigorous preoperative cleansing is mandatory. The extremity to be operated on should be scrubbed for 8 to 10 minutes, extending from the toes to the knee, utilizing an antibacterial soap (e.g., 4% chlorhexidine gluconate or povidone-iodine scrub) that the patient’s skin can tolerate.

• Targeted Cleansing: Particular attention must be directed to the interdigital web spaces and the periungual folds, where bacterial loads are highest.
• Sterile Wrapping: Following this initial ward or pre-induction cleansing, the extremity is wrapped sterilely with a cloth secured by a gauze wrap. This protective barrier is not removed until the patient is positioned on the operating table.

Intraoperative Skin Preparation

Once the patient is on the operating table, the skin is prepared again with a surgical antiseptic solution. The choice of antiseptic and the method of application remain subjects of ongoing academic debate.

Forefoot procedures are particularly worrisome due to the exceptionally high bacterial counts between the toes. While no universal consensus has been reached regarding the absolute best skin preparation solution in foot and ankle surgery, quantitative analyses of positive cultures have demonstrated significant reductions in heavy bacterial growth when mechanical friction is applied. Specifically, the use of bristled brushes combined with povidone-iodine and isopropyl alcohol has been shown to effectively penetrate the stratum corneum and dislodge deep-seated bacterial colonies.

Clinical Pearl: When preparing the foot, mechanical friction is just as critical as the chemical agent. The thick keratinized layer of the plantar foot shields bacteria from superficial painting. Use a bristled brush for the initial scrub phase before applying the final antiseptic paint.

Recent literature has challenged traditional dogma regarding the necessity of isolating the toes during hindfoot surgery. A landmark study by Goucher and Coughlin investigated the efficacy of skin preparation with chlorhexidine gluconate and isopropyl alcohol. They found no clinical benefit in covering or isolating the toes during hindfoot or ankle surgery following this specific preparation protocol. In their cohort, only two of 40 patients yielded positive cultures postoperatively, and critically, neither patient developed a clinical infection.

ANTIMICROBIAL PROPHYLAXIS

Systemic prophylactic antibiotics are utilized routinely in foot and ankle procedures to further reduce the incidence of postoperative infections, particularly when hardware (osteosynthesis materials or arthroplasty implants) is being utilized.

• First-Line Agents: A first-generation cephalosporin (e.g., Cefazolin 2g IV, or 3g for patients weighing >120 kg) is the gold standard and the most frequently utilized antibiotic. It provides excellent coverage against Staphylococcus aureus and Streptococcus species, the most common pathogens in orthopaedic SSIs.
• Alternative Agents: If the patient possesses a documented, severe allergy to penicillin or cephalosporins (e.g., anaphylaxis, Stevens-Johnson syndrome), an aminoglycoside (e.g., Gentamicin), Clindamycin, or Vancomycin should be administered.
• Timing: Prophylactic antibiotics must be completely infused 15 to 60 minutes prior to the inflation of the tourniquet or the initial surgical incision to ensure adequate tissue minimum inhibitory concentrations (MIC).

Surgical Warning: In patients with a history of MRSA colonization or those residing in healthcare facilities, consider the addition of Vancomycin to the prophylactic regimen. Ensure Vancomycin is infused slowly over 60-120 minutes to prevent Red Man Syndrome, timing the infusion appropriately before tourniquet inflation.

OPERATING ROOM SETUP, ERGONOMICS, AND EQUIPMENT

The ergonomic setup of the operating room is paramount for minimizing surgeon fatigue and maximizing surgical precision. When performing foot or ankle surgery, the surgeon and the primary assistant may choose to sit or stand, depending on the specific procedure and personal preference.

Draping and the Sterile Field

When the surgeon elects to sit—common during intricate forefoot procedures or midfoot fusions—additional draping is required. A sterile drape should be secured to the operating table and extended over the body of the surgeon. This creates a continuous, sterile field in the surgeon’s lap, preventing contamination if instruments are dropped or rested during the procedure.

Illumination and Magnification

Lighting that reduces shadows and focuses sharply on the operative field is an absolute necessity.
* Headlights: A high-intensity, fiber-optic or LED headlight is highly recommended, especially during deep plantar dissections, tarsal tunnel releases, or when navigating the complex anatomy of the subtalar joint.
* Magnification: Surgical loupes (2.5x to 3.5x magnification) are strongly advised to aid in the identification and protection of delicate neurovascular structures.

Limb Stabilization

To reduce the risk of iatrogenic injury, particularly to cutaneous nerves (e.g., the superficial peroneal nerve, sural nerve, or saphenous nerve), an assistant must hold the foot motionless. Retraction should be firm but gentle, utilizing appropriate instruments (e.g., Senn or Ragnell retractors) to avoid crushing the skin edges.

Careful preoperative planning, a thorough knowledge of the pertinent cross-sectional anatomy, excellent surgical exposure, proficiency with specialized equipment, and the strict elimination of operating room distractions collectively reduce the likelihood of an undesirable outcome.

TOURNIQUET PRINCIPLES AND HEMOSTASIS

The use of a pneumatic tourniquet is a cornerstone of operative orthopaedics. It allows for meticulous dissection in a completely bloodless field, significantly decreasing the likelihood of iatrogenic injury to nerves, vessels, and tendons, while simultaneously reducing operative time.

Indications and Contraindications

While a tourniquet is highly beneficial, adequate surgery of the foot can be performed without one. In selected patients, a tourniquet is strictly contraindicated.
* Absolute Contraindications: Severe peripheral vascular disease (PVD), calciphylaxis, deep vein thrombosis (DVT) in the operative limb, and sickle cell disease (where hypoxia and acidosis can trigger a sickling crisis).
* Relative Contraindications: Advanced age with fragile skin, severe peripheral neuropathy, and previous revascularization procedures (e.g., femoral-popliteal bypass grafts).

When the blood supply to the foot is questionable, a tourniquet is not recommended, and a constricting wrap around the ankle should be explicitly avoided to prevent irreversible ischemic necrosis of the distal extremity.

Exsanguination Techniques

Prior to tourniquet inflation, the limb must be properly exsanguinated to ensure a truly bloodless field.
1. Elevation: Elevating the leg at 45 to 60 degrees for 2 to 3 minutes allows for gravity-assisted venous drainage.
2. Mechanical Exsanguination: Exsanguination of the extremity from the toes to the proximal edge of the tourniquet is achieved using an elastic rubber wrap (Esmarch bandage) that is 10 cm wide. The wrap is applied tightly in an overlapping, distal-to-proximal fashion.
3. Inflation: The tourniquet is inflated rapidly while the Esmarch bandage is still in place, after which the bandage is promptly removed.

Pitfall: Never use an Esmarch bandage for exsanguination in a patient with a known or suspected deep vein thrombosis, or in the presence of a severe, purulent infection (e.g., a wet gangrenous diabetic foot ulcer), as this can precipitate a fatal pulmonary embolism or systemic bacteremia. In these cases, rely solely on gravity elevation prior to inflation.

Tourniquet Pressure Settings

The determination of appropriate tourniquet cuff pressure is critical to minimizing the risk of nerve neurapraxia and underlying soft tissue crush injury. Historically, standard pressures were applied universally; however, modern practice dictates a personalized approach.

If a tourniquet is used, the pressure should generally be set 100 to 125 mm Hg higher than the patient's systolic blood pressure. Most surgeons consider the patient's baseline blood pressure, the circumference of the limb, and the amount of subcutaneous adipose tissue when determining the final cuff pressure.

In a comprehensive survey of members of the American Orthopaedic Foot and Ankle Society (AOFAS), the pressures most commonly used for calf and ankle cuffs ranged from 201 to 250 mm Hg. However, Younger et al. critically evaluated these practices and suggested that these pressures might be unnecessarily high for many patients. Modern pneumatic tourniquets capable of calculating Limb Occlusion Pressure (LOP) allow for the lowest effective pressure to be utilized, often significantly below 200 mm Hg for calf applications, thereby reducing the risk of post-tourniquet syndrome.

Tourniquet Time Limits and Ischemic Preconditioning

Prolonged ischemia leads to cellular hypoxia, acidosis, and eventual muscle necrosis, alongside mechanical compression injuries to peripheral nerves.

• Standard Limits: We rarely leave the tourniquet inflated for more than 90 minutes during procedures on the foot.
• Maximum Limits: Occasionally, complex reconstructive procedures may require inflation up to 120 minutes, which is generally considered the absolute upper limit of safe continuous ischemia in a healthy adult limb.
• Deflation Protocols: If the surgical procedure is prolonged and the surgeon anticipates the need for a tourniquet for longer than 60 to 75 minutes, it is highly advisable to employ a deflation protocol. The tourniquet should be deflated, and the leg elevated for 10 to 15 minutes to allow for reperfusion and the washout of acidic metabolic byproducts. Following this reperfusion period, a second tourniquet inflation should not exceed 30 minutes.

Tourniquet-Free Surgery: Emerging Evidence

While the tourniquet remains a staple, there is a growing body of evidence advocating for tourniquet-free surgery in specific scenarios. Smith and Hing, in a rigorous systematic review, reported that patients who underwent foot and ankle surgery without a tourniquet experienced:
* Less postoperative pain.
* Reduced postoperative swelling and edema.
* A shorter overall hospital stay compared to those who had tourniquet-assisted surgery.

Furthermore, their review suggested a potentially greater incidence of wound infection and deep vein thrombosis (DVT) in tourniquet-assisted foot and ankle surgery, likely secondary to reactive hyperemia, post-ischemic tissue hypoxia, and venous stasis. Although they conceded that further large-scale, randomized controlled trials are warranted to definitively change standard practice, these findings highlight the necessity of using tourniquets judiciously.

POSTOPERATIVE PROTOCOLS AND REHABILITATION

The surgical technique does not end with skin closure; the immediate postoperative management is critical for ensuring wound healing and preventing complications.

Dressings and Splinting

Following deflation of the tourniquet and meticulous hemostasis, a sterile, non-adherent dressing is applied to the incision. For most major foot and ankle reconstructions, a bulky, mildly compressive dressing (such as a modified Robert Jones bandage) is applied. This serves multiple purposes:
1. It absorbs postoperative hematoma and exudate.
2. It provides a physical barrier against contamination.
3. It offers mild compression to counteract the reactive hyperemia and edema that inevitably follows tourniquet deflation.
4. It immobilizes the soft tissues, reducing tension on the surgical incision and promoting primary intention healing.

Elevation and DVT Prophylaxis

Strict elevation of the operative extremity above the level of the heart is mandatory for the first 48 to 72 hours postoperatively to minimize swelling and throbbing pain. Depending on the patient's risk factors (e.g., obesity, history of VTE, use of oral contraceptives) and the duration of postoperative immobilization, chemical DVT prophylaxis (e.g., Low Molecular Weight Heparin or direct oral anticoagulants) should be considered in accordance with current AAOS and ACCP guidelines.

In conclusion, mastering the surgical techniques of foot and ankle orthopaedics requires a synthesis of anatomical knowledge, evidence-based preoperative preparation, and precise intraoperative execution. By respecting the unique microbiological environment of the foot and judiciously managing tourniquet application, the orthopaedic surgeon can consistently achieve optimal functional outcomes while minimizing the risk of devastating postoperative complications.