23.3.1 Introduction

The fibula flap was originally described by Taylor et al in 1975 as a vascularized bone flap for augmented osteoinduction in a large tibial defect. ¹³ The flap was then modified by Chen and Yan in 1983 to include a skin paddle. The fibula osteocutaneous flap has remained a workhorse flap for segmental and intercalary bony defects in combination with soft-tissue reconstruction. ¹⁴ The ubiquitous use of this flap for long bone reconstruction is due to the length of bone one can obtain (over 25 cm) and the ability to reliably carry a cutaneous paddle with the flap. Multiple reports have demonstrated excellent rates of union, with up to 80% primary union rates and as high as 97% following supplemental bone grafting. ¹²

23.3.2 Attributes

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  Bicortical bone for increased mechanical strength and potential weight bearing.

  
  
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  Longest available piece of vascularized bone for reconstruction (~25–30 cm).

  
  
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  It can be osteotomized to fit recipient defect.

  
  
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  Multiple configurations include longitudinal strut, double-barreled, onlay, and as a hybrid used in conjunction with massive cadaveric allograft.

  
  
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  Large diameter vascular pedicle based on peroneal artery and comitantes.

23.3.3 Detriments

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  It sacrifices a major blood vessel to the lower leg.

  
  
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  Proximal and distal osteotomies must be carefully placed to avoid injury to the common peroneal nerve (CPN) or ankle mortise.

  
  
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  Skin paddle design inclusion frequently results in the need for skin grafting at the donor site.

  
  
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  Dissection through the flexor hallucis can result in a stiff or contracted toe.

  
  
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  It can result in chronic ankle instability.

23.3.4 Anatomic Considerations

The fibula receives its blood supply from the peroneal, anterior interosseous, and lateral geniculate arteries ¹⁵ ; however, the majority of flaps are designed to utilize the peroneal artery as the flaps’ major blood supply. All of the vessels supplying the fibula originate from the popliteal artery. After passing beneath the popliteus muscle, the popliteal artery divides into two major terminal branches: the anterior tibial artery and the tibioperoneal trunk. The anterior tibial artery branches proximal to the tibioperoneal trunk and perforates the interosseous membrane to travel within the anterior compartment of the leg. After passing through the interosseous membrane, the anterior tibial artery gives off several branches that supply the fibular head and fibular physis in children. These branches include the circumflex fibular artery as well as the first and second recurrent epiphyseal arteries. ¹⁵ Distal to the anterior tibial artery’s branch point, the popliteal artery terminates in the tibioperoneal trunk, which divides into the posterior tibial artery (coursing medial) and peroneal artery passing laterally to run along the posterior medial surface of the fibula.

After branching to the fibula, the peroneal artery runs in close proximity to the medial surface of the fibula between the tibialis posterior muscle and the flexor hallucis muscle. The peroneal artery provides both a nutrient vessel for endosteal blood flow and multiple periosteal perforating branches. The nutrient artery to the fibula diaphysis enters in the middle third of the bone and should be preserved during dissection. Additionally, the peroneal artery gives off several perforators to the lateral leg skin. These perforators pass along the posterior margin of the fibula, within the septum of the deep posterior compartment, also referred to as the posterior crural septum. A pooled analysis of 1,710 peroneal perforators was performed to evaluate the location and frequency of these cutaneous perforators along the axis of the fibula. The authors found that if the total length of the fibula is marked off into tenths from proximal to distal, the area with the highest density of perforators was localized in the sixth interval from the fibular head, with 19% of all perforators being found in this region. There was a 79% positive predictive probability of finding a skin perforator in this region. More proximal along the fibula, perforators are more likely to travel through the muscle belly of the soleus prior to irrigating the skin, whereas distal perforators are more likely to be septocutaneous due to the Achilles musculotendinous interface. ¹⁶

Finally, the surgeon should be aware of the course of the CPN, as it runs close to the proximal limits of the fibula dissection (Fig. 23‑1). The nerve originates from the apex of the popliteal fossa after splitting from the sciatic nerve, which continues distally as the tibial nerve. The CPN then travels between the head of the lateral gastrocnemius and the medial margin of the biceps femoris. At the fibular head, the CPN will often be encountered in the plane of dissection of the fibular flap as it moves from the popliteal fossa to the lateral compartment. At the level of the peroneus longus, the nerve divides into the superficial branch and deep peroneal branch. To protect the nerve and its branches, the proximal osteotomy is typically made 5 to 7 cm distal to the fibular head; however, if necessary, the head of the fibula may be taken for added length or for cases that require a growth plate transfer. In such cases, the nerve should be identified and protected during flap elevation.

23.3.5 Anatomic Variations and Potential Pitfalls

The complications seen with the fibular flap are often related to lower leg anatomic variation and fibula donor site morbidity. Due to the limited skin laxity, intramuscular dissection, and ankle mortise changes, removal of the fibula can be associated with several donor site complications. Momoh et al ¹⁷ evaluated 157 consecutive patients who underwent a free fibula flap for head and neck reconstruction, in order to determine the risk factors for acute and long-term morbidity following use of the flap. They found a 31.2% incidence of perioperative complications, most commonly due to local wound disruptions, including skin graft loss at the closure site (15%), cellulitis (10%), and dehiscence (8%). Additionally, long-term complications were identified in 17% of patients, and were commonly related to gait disturbances, with decreased ankle mobility (12%), hallux contracture (9%), leg weakness (8%), and ankle instability (4%). Despite these complications, the authors reported that 96% of patients returned to their preoperative level of ambulatory activity.

From a vascular standpoint, in patients with normal three-vessel runoff the harvest of the peroneal artery appears to have minimal impact to the overall vascularity and viability of the distal leg and foot. To demonstrate this, near-infrared spectroscopy has been utilized pre- and postoperatively following the removal of the fibula flap and the corresponding peroneal artery. The study found that the distal oxygen saturation decreased less than 5% in the first 8 hours postoperatively; however, the oxygen saturation subsequently recovered to the baseline after 8 hours. ¹⁸

In rare instances, the posterior tibial or anterior tibial arteries can be hypoplastic or injured, and the peroneal artery subsequently becomes a dominant arterial supply to the lower leg and foot. In rarer instances, both the posterior tibial and the anterior tibial are aplastic, creating a hypertrophied peroneal artery, referred to as a peronea arteria magna. To determine the incidence of these rare variations, a systematic review was conducted among 26 studies, which examined a total of 5,790 limbs. ¹⁹ The study found that abnormal branching patterns with at least one hypoplastic artery have been reported in 5% of patients. The most frequent variation reported was a hypoplastic posterior tibial artery, whereas the incidence of the peronea arteria magna was only found in 0.4% of limbs.

While the incidence of anatomic variation is low, we still recommend preoperative evaluation of the lower extremity prior to flap elevation. In the cases of lower extremity trauma, this may be even more important for the recipient limb, where single vessel traumatic occlusion can be seen in greater than 25% of patients requiring free tissue transfer. ²⁰ A CT angiogram can provide detailed anatomic arterial information of both lower limbs and can be obtained with little risk to the patient. Finally, during flap elevation, the surgeon should carefully verify that the peroneal artery is the selected vessel, as retractors or dissection within the posterior compartment can place the posterior tibial artery in close proximity to the fibula, potentially resulting in injury to the posterior tibial artery or common tibioperoneal trunk.

23.3.6 Flap Design

The fibula can be either oriented as a single longitudinal flap or osteotomized to create a “double-barreled” paired configuration (Fig. 23‑3). The paired endosteal, or “internal,” and periosteal (“external”) circulations allow the segments to remain well vascularized if the intervening periosteal sleeve is left intact without injury. The double barrel may be especially useful when reconstructing large metaphyseal defects or areas subjected to high axial strain and weight bearing. However, in order to have sufficient bone for reconstruction, the double-barrel configuration should be limited to defects less than 13 cm in length, based on the average available length of the fibula.

Some authors have advocated for the use of the longitudinal vascularized fibular strut with a combination of rigid plating, as the fibular flap will eventually hypertrophy following repetitive load. Sainsbury reported on 18 patients with fibula flap interposition following resection for sarcoma. In this group, the mean time to union was 24 months (range, 9–72 months), and the authors found that the fibula underwent significant hypertrophy following axial loading, with resultant diameters of 71% of the recipient bone. ²¹

Alternatively, in the cases of chronic nonunion, the fibula can be utilized to augment primary bone healing in combination with autograft or allograft. The “onlay” technique describes a technique where the fibula is used to span the site of nonunion to increase osteogenesis and primary bone healing; this technique is especially useful in the cases of chronic infection, failed massive allograft, or irradiated avascular bone. ²² Friedrich et al evaluated the outcomes of 25 patients who received an onlay fibular flap, and found fracture union in 21 patients at an average of 11 months postoperatively, 22 of these patients having received prior bone irradiation. The authors noted that 21 of the fractures were pathologic secondary to irradiation and avascular necrosis. Prior to fibular flap treatment, 10 patients had failed operative fixation of the fracture with a nonunion for an average of 14 months, and the remaining 15 had trialed and failed cast immobilization. ²³

In oncologic cases where the intercalary bone defect exceeds the length requirements of a double-barreled design, or in those that may require more rigid osteosynthesis, the fibula flap can be placed within the center of an allograft. This hybrid technique was originally described by Capanna in 1993 for reconstruction of large oncologic intercalary bone defects of the tibia, and utilizes an allograft that has been cored or hallowed to allow the passage of the fibula flap internally (Fig. 23‑4). The fibula can be slotted into the intramedullary canal of the allograft. A channel is then created within the allograft with a rotary burr to allow access and passage of the vascular pedicle (Fig. 23‑4). The Capanna technique allows for immediate rigid fixation as large plates, or double plating can be applied to the allograft, while the fibula remains protected from injury during hardware fixation. In the long term, the fibula allows for accelerated healing at the osteosynthesis sites. In addition, the fibula helps revascularize the allograft leading to lower rates of infection and late fracture. ¹¹

Studies evaluating the outcome of the Capanna technique have demonstrated improved time to bone healing and subsequent weight bearing. Houdek et al evaluated their outcomes with the technique in 18 pediatric patients who underwent limb salvage following oncologic tibial resections. In this group, the overall limb salvage rate was 94% and despite 6 patients requiring a secondary procedure for a symptomatic nonunion, 17 of these patients had good or excellent outcome as indicated by their Mankin score. ^{24 ,​ 25} Similar findings were demonstrated by Schwarz et al. In their retrospective review of 13 patients, 8 required secondary bone grafting for nonunion, but the median time to union was 10 months (range, 3–40 months) and of the surviving patients, 91% achieved full weight bearing by 2 years and were able to participate in sports. ²⁶

Finally, the fibula flap design can be modified to include the proximal fibular head for either a vascularized physeal transfer or an osteochondral flap. Dissection is modified in these cases to harvest the fibular head on the anterior tibial artery and subsequent nutrient branches to the fibular head and physis. ¹⁵ In these cases, the fibula is approached through the interval between the tibialis anterior and extensor digitorum longus. The motor branches from the deep peroneal nerve must be carefully preserved to the anterior compartment, while including a strip of muscle and interosseous membrane with the recurrent epiphyseal branch of the anterior tibial artery.

23.3.7 Flap Harvest

The total length of the fibula should be marked out to identify a safe interval for the proximal and distal osteotomies. Typically, 6 cm is left proximally to prevent iatrogenic injury to the CPN proximally and 6 cm is left distally to avoid the development of ankle instability distally (Fig. 23‑1).

If a skin paddle is to be included, the perforators are identified with a handheld Doppler along the posterior border of the fibula, whereas any skin perforators on the anterior margin are most likely from the anterior tibial artery and should not be included. The paddle should be marked out, with the anticipation that skin paddles in excess of 4 cm may require a skin graft for donor site closure. ¹⁷ Under tourniquet control, the anterior skin margin can be incised, and the surgeon should consider a suprafascial dissection to maintain a potential surface for skin grafting in larger skin paddles. Additionally, this may help identify and avoid injury to the superficial peroneal nerve.

The division between the anterior and lateral compartments can be identified by a longitudinal fibrofatty strip, and based on the Doppler, dissection proceeds to the posterior margin of the peroneus longus and brevis muscles to the marked perforators. We find it helpful to separate the soleus insertion from the fibula. This allows one to create a window into the posterior compartment to visualize the peroneal vessels proximally. At this point, we will often also identify the peroneal nerve and mark it with a vessel loop to prevent any retraction injury.

Once the peroneal artery has been visualized, dissection begins to elevate the peroneus muscles and the extensor digitorum muscles medially. The skin perforators can be isolated on their perforator passing through the posterior crural septum. Proximally, skin perforators can be dissected through the soleus without a muscular cuff by following the course of the perforator and associated fascial envelope. At this point, the skin flap can be tacked to the bone with several temporary stitches to prevent avulsion during the remainder of the harvest. If there is no skin paddle, the elevation of the fibula flap can proceed directly without identification of perforators or posterior dissection of the soleus.

The peroneal and anterior compartment muscles are then reflected sharply to keep a minimal (1–2 mm) cuff of muscle intact to prevent injury to the periosteum. Following this, the interosseous membrane is identified and carefully incised near the fibula. At the site of the bone cuts, a periosteal elevator is used to carefully create space between the peroneal artery and the fibula, and a curved retractor is placed to protect the vessels. Distally, in the instance of heavy atherosclerosis or if there is potential difficulty controlling the pedicle, a 1-cm paired osteotomy can be performed to remove a small block of bone and allow direct visualization and control of the pedicle. Following the proximal and distal osteotomies, the flap is elevated from distal to proximal, freeing the pedicle from the flexor hallucis muscle and preserving the skin perforators, if included. The proximal peroneal artery and venae comitantes are identified at the tibioperoneal trunk, and if possible, the tourniquet is deflated prior to ligation to ensure adequate perfusion to both the flap and the foot.

Following harvest, the flexor hallucis muscle can be suspended to the interosseous membrane with the hallux in extension to prevent postoperative toe contractures. Additionally, the operative leg should be immobilized for 5 to 7 days in a well-padded posterior splint with the ankle in neutral.

23.4.1 Introduction

Free rib flaps were first described in 1977 for reconstruction of lower extremity injuries. ²⁷ The rib is composed of membranous bone that possesses a dual blood supply, from the posterior intercostal artery and an abundant periosteal blood supply from the serratus anterior muscle. The periosteal blood supply is derived from the thoracodorsal artery providing a long reliable pedicle to be used in vascularized bone grafting. Typically, this graft is used to reconstruct lower extremity defects when the contralateral fibula is damaged or absent. ²⁸

One advantage of this flap is the combination of a large serratus muscle soft-tissue envelope with or without the latissimus. ²⁹ This allows for bone reconstruction and extensive soft-tissue coverage with the use of a single pedicle. Double-rib transfers are also possible without the need for excessive chest wall reconstruction. Double-rib transfers have been shown to be biomechanically superior to single-rib transfer for some nonunions. ³⁰

23.4.2 Attributes

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  Cortical cancellous vascularized bone of up to 10 to 15 cm can be easily harvested.

  
  
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  Can be harvested in combination with the serratus, latissimus, or scapular flap.

  
  
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  Minimal functional donor site morbidity.

  
  
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  Can be osteotomized to ease insetting.

23.4.3 Detriments

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  Risk of pneumothorax.

  
  
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  Potential risk to long thoracic nerve injury, which could lead to winged scapula.

  
  
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  Proximal serratus resection can lead to scapular dysfunction.

  
  
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  Bone does not provide sufficient biomechanical strength for unrestricted weight bearing alone, and is best used to augment existing structural bone.

23.4.4 Anatomic Considerations

The rib receives its blood supply from the intercostal vessels, which provide endosteal and periosteal perforators. The thoracodorsal arterial contribution to the serratus muscle anastomoses with the intercostal system, allowing the rib to be harvested on the serratus muscle. Additionally, the serratus muscle supplies intramuscular perforators directly to the rib periosteum.

As the ribs are curved, we find it best to osteotomize the pleural cortex with an oscillating saw prior to placing them within the leg. This allows one to straighten the rib against the tibia or the femur. ³¹ We also prefer to fix the ribs with 3.5 compression screws or with heavy suture in a cerclage fashion. While the rib lacks the structural strength of the fibula, the high cancellous content may accelerate bony consolidation. ³²

23.4.5 Anatomic Variations and Potential Pitfalls

When harvesting the rib with the serratus anterior as part of a combination “chimeric” flap with the latissimus dorsi or scapular flap, the pedicle must be dissected all the way to the axillary artery in order to rule out any vascular anomalies and to ensure that the latissimus dorsi and the other components are nourished by a single thoracodorsal pedicle. Once the pedicle has been adequately visualized, the serratus anterior digitations between the 5th and 10th ribs can be harvested in conjunction with the latissimus dorsi. Most surgeons prefer to take the digitations between the 5th and 8th ribs as the 9th and 10th rib digitations are not always reliable. Harvesting only between the sixth and eighth digitations has been shown to be helpful in minimizing functional morbidity created by sacrificing the serratus muscle. Preservation of the most cephalad portion of the serratus and its attachment to the scapula prevents the possibility of postoperative scapular winging.