Continuing Education Activity

The vascularized fibular free flap is a viable option for the reconstruction of large bony defects. Still, it may not be the ideal reconstructive modality in all scenarios, particularly when the patient suffers from lower extremity vascular disease. This activity reviews the indications and technical aspects of free fibular transfer and highlights the role of the interprofessional team in evaluating and treating patients with complex bone and soft tissue defects.

Objectives:

• Identify the ideal size of the graft and understand how to prepare the recipient area for vascular graft inset.
• Describe the evaluation for preoperative assessment of vascular patency.
• Review contraindications to free fibula transfer.
• Avoid complications in free fibula transfer.

Introduction

Bony defects are most often caused by trauma, tumor, infection, or congenital anomaly, and these can lead to poor quality of life and occasionally amputation. Despite the development of newer techniques like bridging endoprostheses and distraction osteogenesis, non-vascularized bone grafts are still used for the management of nonunions and defects to promote healing. Bone grafts have been used in reconstructive surgery for a century and recent advances in microvascular techniques have made free fibula flap transfer a viable option for reconstruction of long bony defects.[1][2]

In 1975, Taylor et al harvested and transferred the first free fibula through a posterior approach, and the technique was further improved by Gilbert, who described the lateral approach, which was later further developed by Chuang et al, who popularized the osteomyocutaneous fibular flap.[3][4] In 1994, Hidalgo further expanded indications for fibular free tissue transfer by describing osteotomy techniques that permit shaping the fibula to mimic that of the mandible, making the fibula the workhorse for head and neck reconstruction that it is today.[5]

There are many ways of employing fibular bone for reconstruction: cancellous and cortical autografts, bone allografts, endoprosthetic replacement, vascularized bone grafts, fibular osteocutaneous flaps, and fibular osteomuscular flaps.[6][7][8] Among these options, free vascularized fibular grafting is unique in that it provides immediate mechanical support but it also can grow or hypertrophy depending on the patient's situation.[9] Vascularized fibular grafting is not a solution in all cases that require bony reconstruction; however, it is a frequently-used option for bony defects >6 cm, failed non-vascularized bone grafting, infected nonunion with a bony defect, or following tumor resection, particularly when postoperative radiation therapy is planned.

Anatomy and Physiology

Bony Anatomy

The fibula is a long and straight, thick bone measuring approximately 3 cm x 40 cm, slightly longer in males than females. It has a tricortical profile, or triangular cross-section, with the muscle attachments to the fibula determining this shape. The mean fibula length is 387.4 ± 23.7 mm in males and 361.5 ± 12.3 mm in females. 

Joints and Supporting Structures

1. Proximal tibiofibular joint

The synovial joint between the head of the fibula and the lateral condyle of the tibia is supported by a capsule and anterior and posterior superior tibiofibular ligaments. The lateral collateral ligament and biceps femoris support the joint coronally. External rotation of the ankle produces a small amount of movement at the proximal tibiofibular joint.

2. Distal tibiofibular joint (ankle syndesmosis)

The fibrous joint between the fibular notch and distal tibia is made up of the interosseous membrane, the anterior and posterior inferior tibiofibular ligaments, and the inferior transverse tibiofibular ligaments. For this reason, the distal 5 cm of the fibula is essential for ankle joint function; any disruption to the syndesmotic structures can cause ankle instability.[10] 

Vascular Anatomy

The blood supply of the fibula is important for graft viability and union. Penetrating periosteal vessels supply the metaphysis and epiphysis while nonpenetrating periosteal vessels supply the diaphysis.[11] The major blood supply passes through the anterior tibial artery, the peroneal artery, and the posterior tibial artery. The epiphysis and proximal fibula are supplied by the anterior tibial artery, and the peroneal artery supplies the middle third.[10] 

Understanding this anatomy is very important for deciding which part of the fibula is needed for a particular patient's reconstruction. The length of the vascular pedicle can be up to 15 cm if the distal fibula is harvested, less if more proximal bone is used. Additionally, perforating vessels from the peroneal artery can support a skin paddle measuring up to 10 x 20 cm in surface area, which is very useful in head and neck reconstruction. Vascularized bone grafts may withstand early mechanical loading better than non-vascularized grafts and minimize the likelihood of bone resorption and stress fracture, as they can remodel over time.

Indications

Vascularized free fibula can be used in the following scenarios:

1. Traumatic bony defects >6cm in length[12]
2. Bony defects after tumor surgery
3. Resistant pseudarthrosis[13]
4. Limb length discrepancy
5. Chronic osteomyelitis with bone loss[14]
6. Mandibular reconstruction[15]
7. Vascularized epiphyseal transfer (for growing child following tumor resection)[16]
8. Osteonecrosis of the head of humerus/femur[17]

Contraindications

Free fibular flaps are contraindicated in the following scenarios:[3]

1. Peripheral vascular disease involving the lower extremities
2. Hypoplastic anterior tibial artery
3. Small skin pedicle available for flaps
4. Venous insufficiency
5. Deep vein thrombosis
6. History of contralateral lower extremity amputation

Equipment

The following equipment is needed:

• #15 blade scalpel
• Monopolar and bipolar electrocautery
• Soft tissue set with Langenbeck retractors, periosteal elevators, forceps, hemostats, needle drivers, Metzenbaum scissors
• Gigli saw or reciprocating saw
• Plates, screws, and fixation hardware as necessary, screwdriver
• Drill
• Operating microscope
• Microvascular instrument set
• Doppler probe for vascular assessment
• Dermatome for harvesting a split-thickness skin graft to cover the skin paddle donor site, if necessary
• Appropriate sutures for closing the leg and the recipient site
• Dressing supplies for the leg

Personnel

A team consisting of the following personnel is required:

• Anesthesiology team
• Primary surgeon (plastic surgeon, orthopedic surgeon, head and neck surgeon, or oral surgeon )
• Surgical assistants
• Radiographic technician
• Circulating nurse
• Surgical technician

Preparation

Recipient site evaluation includes identification of appropriate vessels to perfuse the flap, determining appropriate patient positioning, and choosing the method of bone fixation. All types of implants should be available (e.g., plates, screws, K-wires, external fixators, and intramedullary nails).

Preoperatively, donor site skin, muscle bulk, and vascular status are evaluated. Strong and independent pulses should be present at both the dorsalis pedis and the posterior tibial artery. Any uncertainty about their status should be further investigated with Doppler ultrasonography. In certain cases, CT (computed tomography) angiography or MR (magnetic resonance) angiography may be required to assess the vascular status. Documentation of a preoperative neurological assessment is necessary because transient postoperative peroneal nerve palsy can occur. 

For tibial reconstruction, the contralateral fibula is preferred, while the ipsilateral fibula is generally used for femoral reconstruction. Upper limb recipient sites may use either fibula, and the choice of the fibula for head and neck reconstruction will depend on the status of neck vessels, as well as whether the mandible or maxilla is being reconstructed, and whether the skin flap will replace oral mucosa or facial skin.

Technique

After informed consent, prophylactic antibiotics are administered, and general anesthesia is induced. An Esmarch bandage is used to exsanguinate the leg, and a tourniquet is applied to either 150 mmHg above systolic blood pressure or 350 mmHg. All pressure points should be padded carefully because of the long duration of the case. Ideally, two teams work simultaneously to decrease operative time, one at the recipient site and the other at the harvest site.[18] Particular attention should be paid to patient positioning to ensure both teams can work efficiently and that the microscope has enough room to be brought close to the field for microvascular anastomosis.

Recipient site surgery: Recipient site surgical dissection depends upon the diagnosis. For example, the extent of bone resection required in cases of pseudarthrosis or the amount of debridement and curettage for chronic osteomyelitis. Resection and reconstruction can be performed as a single procedure or can be done in 2 stages as in osteomyelitis (eradication of infection followed by free fibula transfer) or oncologic resection (ablation of tumor and lymph node dissection followed by fibula transfer after negative margins have been confirmed). It is critical to select and isolate appropriate recipient vessels for vascular anastomosis and to communicate the size of the defect to the fibular harvest team to ensure a graft of adequate length.[19]

Donor site surgery: The lateral surgical approach is the most commonly used, with a longitudinal incision made along the lateral lower leg. The central portion of the fibula is harvested for most indications, as the distal 5 cm is important for ankle joint stability. The proximal 5 cm of bone is also left in place in order to protect the peroneal nerve. Bony cuts are made proximally and distally. Some surgeons consistently harvest the entire fibula between the proximal and distal 5 cm, planning to shorten the bone as necessary after harvest; some harvest only what length is needed to reconstruct the defect. Care is taken to avoid injury of the peroneal artery and its accompanying 2 venae comitantes. If a longer vascular pedicle is required, the use of the distal fibula will provide up to 15 cm in length. In some cases, a graft 2 to 3 cm longer than the bony defect may be required, as overlapping the graft on the osteotomy site may be necessary for fixation.[20] An example of the lateral approach to fibula harvest for head and neck reconstruction is detailed below:

Begin with incision around the anterior aspect of the skin paddle, coming through the subcutaneous fat and fascia, heading deep and anteriorly toward the fibula. Identify but do not dissect out the perforating blood vessels. They may run in the posterior intermuscular septum, but more likely will run through muscle. Follow the posterior intermuscular septum onto the lateral aspect of the fibula. Separate the peroneus brevis from the lateral fibula, which will expose the entire lateral fibula. Leave the periosteum inact between the planned osteotomy sites. Continue dissecting anteriorly until the anterior intermuscular septum is reached; divide the septum. Separate the extensor digitorum longus from the anterior fibula. Continue anteriorly/deeply until the interosseous membrane is encountered; divide the interosseous membrane. Avoid dissecting too deep, because the anterior tibial artery, with its veins and the deep peroneal nerve, can be injured. Make the posterior skin paddle incision and continue between the flexor hallucis longus and soleus, taking care not to injure the previously identified perforators; taking a cuff of soleus muscle with the flap will help to keep the vessels safe. Gently incising along the fascia of the flexor hallucis longus with a #15 blade will allow the posterior tibial artery with its veins and tibial nerve to release somewhat and drop back away from the surgical field. This is known as the O'Leary maneuver. Dissect closely around the deep aspect of the superior fibula at the osteotomy site with a large right angle clamp. Pass the Gigli saw with the clamp and make the superior osteotomy over a malleable retractor to protect the underlying tissue. Dissect closely around the deep aspect of the inferior fibula at the osteotomy site with a large right angle clamp. Pass the Gigli saw with the clamp and make the inferior osteotomy over a malleable retractor to protect the underlying tissue. Distract the fibula laterally and identify the inferior aspect of the pedicle. Ligate the inferior pedicle with 2-0 silk ties. Divide the remaining muscular attachments on the fibula: the tibialis posterior and the flexor hallucis longus. Identify and ligate the superior pedicle after the fibula has been liberated from all of its other attachments. Close in layers over a suction drain. If the skin paddle is narrow or non-existent, primary closure may be possible, but a split-thickness skin graft is usually required.

Fixation of graft: Fixation may be accomplished with a plethora of different techniques, depending on the type of reconstruction. Intramedullary nails, compression plates, and the Ilizarov fixator are all options. Hardware should not be changed once vascular anastomosis is complete, and care should be taken when placing the screws as they can compromise the blood supply to the graft.

In cases of mandibualr reconstruction, a novel approach is the "jaw in a day" concept, in which dental implants are placed into the fibula under the same anesthetic as the flap transfer, substantially expediting the patient's return to oral feeding.[21]

Complications

Anesthesia-related Complications[22]

• Nausea and vomiting
• Dental injuries during intubation
• Sore throat
• Anaphylaxis to anesthetic agents
• Myocardial infarction
• Respiratory depression
• Aspiration pneumonia
• Hypothermia

Intraoperative Complications[23]

• Bleeding
• Length discrepancy of graft
• Iatrogenic graft fracture
• Improper fixation
• Damage to the neurovascular bundle

Postoperative Complications

• Graft fracture (most common complication)
• Surgical site infection (2nd most common complication)[17]
• Great toe contracture (flexor hallucis longus lengthening usually corrects the contracture)
• Peroneal nerve injury[24]
• Hardware failures or extrusion
• Gait disturbance due to pain[25]
• Nonunion/malunion
• Growth abnormality due to physis injury[18]
• Wound dehiscence
• Amputations[26]
• Leg length discrepancies
• Valgus malalignment of the donor limb
• Equinus deformity of the ankle [27]
• Nerve injury with sensory loss or motor deficit
• Chronic ankle pain
• Expanding hematoma
• Thrombosis of the anastomosed vessels and partial or complete flap failure

Clinical Significance

Autogenous vascularized fibular grafting plays a vital role in the reconstruction of long bone defects, infected nonunions, and reconstruction of tumor resection defects in adults and children. Vascularized fibular grafts not only provide osteoinductive and mechanical support but also have the ability to remodel and hypertrophy to withstand loading, making fibular grafting different from other types of bony reconstruction. A successful outcome depends not only on surgeon experience but also on appropriate patient selection and preoperative expectation management.

Enhancing Healthcare Team Outcomes

Patients are usually initially followed by a team of intensivists, surgeons, physical therapists, and speech/swallowing therapists in head and neck cancer reconstruction. Intraoperatively, an interprofessional group consisting of orthopedic/plastic/head and neck/oral surgeons, radiology technicians, surgical technologists, an anesthesiologist, and nursing staff must perform these complicated operations. When two surgical teams can operate simultaneously, the workload is divided operative time is decreased, which lowers the risk of perioperative cardiopulmonary complications.[28]

Patients should be optimized medically before surgery, and the vascularity of the lower extremity should be evaluated with angiography or ultrasound. Careful preoperative evaluation of the patient will establish candidacy for microvascular fibular free tissue transfer and ensure the patient and surgeon share realistic expectations.

Nursing, Allied Health, and Interprofessional Team Interventions

Attentive nursing care is critical in the immediate postoperative period to monitor for flap complications. Physical therapists will help to mobilize the patient early, which can prevent such perioperative complications as deep vein thrombosis and pulmonary embolism. In cases of mandibular or maxillary reconstruction, speech and swallowing therapists and nutritionists are critical to maintaining the patient's caloric intake.

Nursing, Allied Health, and Interprofessional Team Monitoring

Monitoring the flap for signs of failure is critical in the first two weeks of healing, but even more so during the first 72 hours, during which the anastomosed vessels are re-epithelializing. Signs of flap failure include a dusky or pale color, a cool temperature (unless the flap is intraoral), the rigidity of the soft tissue due to edema, either very rapid or absent capillary refill of the skin paddle, either very rapid return of dark blood or no return of blood at all when pricked with a lancet, and absent Doppler signals. Often, loss of the Doppler signal is the last sign of a flap failure, because venous congestion accounts for 80% to 90% of flap failures, and the arterial signal may not disappear until very late in the process. In the case of vascular failure, rapid return to the operating room for revision of the anastomoses is critical.[29]