Tibia Reconstruction

The leg is a complex district with functions of weight-bearing support, stability, and motility. The osseus structure of the lower leg is composed of the tibia and the fibula. The tibia is most responsible for lower leg functions, while the fibula is a fairly expendable bone.

Occasionally, traumas, neoplasms, or acquired or congenital malformations affect the tibia, inhibiting leg functions and consequently necessitating bone reconstruction or substitution.[1] Small bone defects of the tibia are treated with external fixation and cancellous bone grafting, with satisfactory results.

The management of extensive and complex defects is more challenging and often results in leg amputation or shortening. Leg amputation is a severe mutilation that alters the patient's work and social life by limiting ambulation and self-sufficiency. Limb shortening is also responsible for an asymmetric gait and posture deformities.

The advent of microsurgery and its application to bone transfers has radically changed the treatment of complex tibial injuries, allowing plastic surgeons to reconstruct wide bone gaps with optimal functional, morphological, and cosmetic outcome—in most instances, avoiding the need for limb amputation or shortening. Free vascularized fibular transfer has become the standard practice to bridge long (>6 cm) bone defects of the extremities.

In the 1970s, microsurgical techniques were mainly used in emergency settings to reestablish vascular perfusion of amputated limbs and salvage them. Complex tibial fractures or extensive bone defects were usually treated by orthopedic surgeons with autologous nonvascularized cancellous bone grafting stabilized with external fixation. Complex open fractures of the tibia were associated with an increased incidence of delayed union (20-40%), nonunion (7-45%), and osteomyelitis (2.7-27%).[2] These contributed to a high incidence rate of delayed amputation, ranging from 20-75%.

Later, cortical bone grafting with rigid internal fixation was introduced. The early results of the use of the fibula graft protibia appeared satisfactory. In 1980, Enneking et al reported a 95% success rate in the postneoplastic reconstruction of tibial gaps greater than 7.5 cm with large, nonvascularized fibular autografts. This procedure demonstrated several complications, such as stress fractures (32%), bone nonunions (27% at 6 mo), and tibial curvatures. To reduce the complication rate, which increased in infected and poorly vascularized wounds, the use of free bone transfer microsurgically revascularized to the recipient area was proposed.

In 1973, Ueba and O'Brien evaluated the fibula as a donor site for the free microvascular bone flap. The first report of a successful free bone transplant was in 1974 by Ostrup and Fredrickson, who successfully transplanted free rib grafts vascularized on intercostal arteries in dogs.[3]

In 1975, Taylor et al performed the first 2 free microvascular fibula transfers on human patients to reconstruct tibial bone gaps.[4] Microvascular bone flaps were shown to heal more rapidly, with fewer complications and earlier functional recovery than conventional nonvascularized grafts. Gradually, microvascular bone flaps have gained popularity, becoming the treatment of choice for bone defects larger than 6 cm or located in poorly vascularized and contaminated wound beds.

Other donor areas have been used, such as ribs, the iliac crest, the radius, the metatarsus, and the scapula. Each of these has demonstrated some pitfalls and limits because of the reduced amount and poor quality of the bone available to be harvested, the possibility of raised muscle or skin in the flap, and the morbidity of the donor area.

Chen and Yan[5] and Harrison reported on the successful free osteocutaneous fibula flap, and, in 1982, Bovet et al[6] reported the use of an osteomuscular flap by including one half of the soleus muscle together with the fibula bone stock. In 1983, Ueba and O'Brien transplanted a bone stock as long as 30 cm, eventually associated to muscle and skin, using a free osteomyocutaneous fibula flap, with negligible donor area morbidity. Actually, the free fibula flap and the rigid fixation system are the universally recognized methods of treatment of complex tibial defects.

The tibia is a long bone, the anterior third of which is placed subcutaneously in the leg throughout most of its length. It is covered only by a thin layer of skin and subcutaneous tissue, with no surrounding muscle cuff. This anatomic location may be explained by the need to protect the blood vessels and nerves of the leg, which are located deep laterally, medially, and posteriorly. This position makes the tibia easily vulnerable to traumas, often resulting in exposed fractures.

Because of the exposure of devascularized bone in a contaminated bed, the spontaneous healing of these wounds is usually aggravated by delayed union, nonunion, infection, and osteomyelitis. Replacing necrotic or denuded bone with a skeletal substitute capable of healing in such an unfavorable environment is a problem with a difficult solution, even when adequate soft tissue cover is available.

The reconstruction of partially comminuted fractures or small bone gaps usually benefits from cancellous or devascularized cortical bone grafting and external fixation.

On the contrary, the reconstruction of segmental, comminuted tibial fractures or extensive bone defects requires vascularized bone grafts to overcome infection and restore bone continuity and blood supply. The Ilizarov technique is a procedure used for the reconstruction of such defects, but the bulky apparatus, long lengthening and union times, and pin tract infection limit the present method.[7]

Occasionally, malignant neoplasms such as osteosarcomas, chondrosarcomas, Ewing sarcomas, and metastatic tumors may involve the tibia and require resection of the bone and surrounding tissues.[8] In these patients, local curettage is not recommended because of the high incidence of local recurrences and distant metastasis and because of the poor rate of disease-free survival. Wide en bloc excision is indicated, and long bone reconstruction is useful to avoid amputation.

Acquired and congenital pathologies, such as osteomyelitis or pseudoarthrosis, also may affect the tibia, requiring resection and long bone substitution. In these patients, the more favorable local vascular and soft tissue conditions make reconstruction easier; nevertheless, bone grafts still yield high complication rates when gaps greater than 6 cm must be restored.

Generally, the goal in the reconstruction of tibial defects is to restore the anatomy of the altered segment, gaining a satisfactory functional recovery. Finding a bone substitute of adequate length and width, customized to the defect, covered by vascularized muscle or skin, and stabilized in the most anatomic position compatible with maximal functional return is often a great demand. Currently, microvascular free bone grafts are the best answer.

Large defects of the tibia are more often caused by low- to high-speed injuries resulting in exposed comminuted fractures than by the resection of bone tumors, osteomyelitis, or pseudoarthrosis.

Tibial fractures are the most common long bone fractures of the body skeleton. The most frequent causes are motorcycle accidents (28% of patients), vehicle accidents (24%), domestic accidents (13%), pedestrian accidents (12%), crushing lesions (8%), firearm accidents (2%), and miscellaneous causes such as work- and sports-related accidents (13%). For more information on traumatic injury, visit Medscape’s Trauma Resource Center.

Malignant tumors arising from the skeleton frequently involve the long bones such as the tibia. Among these tumors, the most frequent are osteogenic sarcomas, chondrosarcomas, fibrosarcomas, malignant histiocytomas, adamantinomas, lymphomas, angiosarcomas, liposarcomas, Ewing sarcomas, and tumors from metastatic diseases.

Etiologic factors involved in the pathogenesis of bone tumors are generally the same as those recognized for the development of cancer, such as genetic predisposition, exposure to carcinogens, and irradiation.

Chronic osteomyelitis of the tibia may be the consequence of an infection caused by trauma, surgery, or a contiguous infection (exogenous form), or it may be caused by an unknown bacteremia (hematogenous form; see the image below).

Chronic exogenous osteomyelitis is frequently the result of mistreatment of severe open fractures, leading to nonunion, deep acute infection, and bone incarceration.

Congenital pseudoarthrosis of the tibia is a specific type of nonunion that is present or incipient at birth. It is a rare malformation involving only 1 in 250,000 live births. Etiologic causes are unknown, but this disorder is frequently associated (50-90%) with neurofibromatosis.

Acquired forms of pseudoarthrosis may occur as a result of delayed union of severe fractures, leading to excessive callus formation, reduced stability, and tibial bowing.

The classification of tibial fractures considers the mechanism of the trauma, the location, the extent and type of fracture, involvement of soft tissues, and neurovascular impairment. The type of tibial fracture is related to the mechanism involved in its pathogenesis, ie, contusive, clean-cut, tear, degloving, crushing, avulsion, and burst (high speed). Usually, crushing, avulsions, or high-speed bursting injuries lead to more complex defects.

The anatomic classification divides tibial fractures into fractures of the knee, the tibial plate, the tibial shaft, and the ankle. Most of these are of strict pertinence to the orthopedic surgeon, while large, comminuted open fractures of the tibial shaft, commonly associated with wide soft tissue loss, require the expertise of plastic microsurgeons.

The extensive Orthopaedic Trauma Association classification of long bone fractures divides them according to the line of fracture as follows: linear (transverse, oblique, spiral), comminuted (< 50%, >50%, butterfly < 50%, butterfly >50%), segmental (2 level, 3 level, longitudinal split, comminuted), and bone loss (< 50%, >50%, complete).

The clinical classification considers the involvement of soft tissues in open fractures. In 1984, Gustilo and colleagues described 5 different grades in the Association of Osteosynthesis classification, as follows[9] :

• Grade 1 - Skin lesion smaller than 1 cm; clean; simple bone fracture with minimal comminution

• Grade 2 - Skin lesion larger than 1 cm; no extensive soft tissue damage; minimal crushing; moderate comminution and contamination

• Grade 3 - Extensive skin damage with muscle and neurovascular involvement; high-speed injuries; comminution of the fracture; instability

  • Grade 3a - Extensive laceration of soft tissues with bone fragments covered; usually high-speed traumas with severe comminution or segmental fractures

  • Grade 3b - Extensive lesion of soft tissues with periosteal stripping, contamination, and severe comminution due to high-speed traumas; usually, exposed bone must be replaced with a local or free flap as a cover

  • Grade 3c - Exposed fracture with arterial damage that requires repair (see the images below)

    Clinical Case 1. Preoperative radiograph of the traumatized leg. A multiple segmental and exposed spiral fracture of the tibia is identified (Gustilo stage 3c).
    Clinical Case 1. Early postoperative view of the emergency management of a middle-third tibial fracture. Reduction of the fracture and skin grafting to the defect.

The association of soft tissue injury with tibial fracture is of great importance in determining the ideal treatment.

Bone fragments or segments that are preserved but devascularized and not covered by healthy soft tissue usually heal into nonunion or pseudoarthrosis or undergo necrosis and require removal and secondary free bone reconstruction.

In 1985, Byrd et al formulated a new and simplified classification of fractures, based on the mechanism of the trauma and bone and soft tissue lesion.[10] They recognized the importance of both the direct and indirect traumatic forces responsible for the bony lesions. Their classification is as follows:

• Type I - Low-energy fractures; oblique or spiral fracture with clean-cut laceration smaller than 1 cm

• Type II - Medium-energy trauma; displaced or comminuted fracture with laceration larger than 2 cm and myocutaneous contusion

• Type III - High-energy trauma; severely displaced or comminuted fracture; segmental fracture or bone defect with laceration larger than 2 cm and loss of skin and muscle substance

• Type IV - High-energy bursting trauma; crushing or avulsion with arterial damage requiring microvascular repair

Usually, malignant neoplasms involving the tibia, such as osteosarcomas, may be discovered incidentally during a routine roentgenogram of the skeleton or may manifest as a mass evoking pain by irritating surrounding tissues or causing a spontaneous fracture.

Occasionally, they may be discovered because of the presence of regional nodal metastasis of a silent primary bony lesion. Diagnosis is made using images from standard roentgenograms, nuclear magnetic resonance (NMR) and CT imaging scans, arteriograms, guided biopsies, and the report from the pathologist.

Radiologically, these malignant neoplasms may manifest variably as lytic or sclerotic lesions. The classification is according to the extent of the bony lesion, invasion of soft tissues, presence of regional or distant spread, and histologic grade.

In 1989, Enneking staged tumors in relation to anatomic site as follows[11] :

• Tumors

  • T1 - Intracapsular

  • T2 - Extracapsular intracompartmental

  • T3 - Extracompartmental

• Grading

  • G0 - Benign

  • G1 - Low-grade malignant

  • G2 - High-grade malignant

• Presence of metastases

  • M0 - Absent

  • M1 - Present

Enneking classified them in 3 main stages (I, II, III) and 2 substages (A, B) and differentiated treatment in relation to the stage. Staging grade site metastasis is as follows:

• IA, G1, T1, M0

• IB, G1, T2, M0

• IIA, G2, T1, M0

• IIB, G2, T2, M0

• IIIA, G1-2, T1, M1

• IIIB, G1-2, T2, M1

The hallmark of chronic osteomyelitis is infected dead bone within a compromised soft tissue envelope. Usually, osteomyelitis of the tibia manifests clinically as a torpid skin ulcer or cutaneous fistula secreting pus and overlying a chronic fracture site. One or more foci in the bone may contain purulent material, granulation tissue, or a sequestrum, and they may be surrounded by sclerotic, avascular bone and covered by scarred muscle and subcutaneous tissue.

Systemic symptoms usually subside. Bone necrosis, sclerosis, and lysis may be evident on radiographs. The diagnosis is supported by findings of radiolabeled monoclonal antibodies against leukocyte antigen scanning.

According to Cierny and Mader, clinical classification depends on physiologic and anatomic criteria.[12] The physiologic criteria are as follows:

• Class A - Normal response host

• Class B - Compromised wound healing

• Class C - Potentially worsening

Anatomic criteria are as follows:

• Type I - Medullary

• Type II - Superficial

• Type III - Localized full-thickness

• Type IV - Diffuse

Congenital pseudoarthrosis usually manifests in adolescence as an incorrect development of one of the main bone articulations.

Boyd classified congenital pseudoarthrosis into 6 types, as follows[13] :

• Type I - Anterior bowing and defect present at birth

• Type II - Hourglass constriction at birth

• Type III - Congenital cyst

• Type IV - Sclerotic segment with medullary obliteration

• Type V - Dysplastic fibula

• Type VI - Intraosseous neurofibroma or schwannoma

Acquired pseudoarthrosis manifests clinically as a chronically unstable bone union at the fracture site. Angulation or displacement of the bone segments may be evident. A hypertrophic callus may be present on the radiograph, together with a still-evident line of fracture (see the images below).

Traumatic fractures, tumors, osteomyelitis, or pseudoarthrosis may require compromised bone resection and subsequent reconstruction. Conventional treatments (ie, bone grafting, Ilizarov technique) are best indicated for limited (< 6 cm) defects because of the long time needed for newly formed bone to consolidate.

Microsurgical bone transfers are indicated when conventional treatments are not useful (ie, bone defect >6 cm, poorly vascularized or infected recipient beds) or have previously failed.

Primary indications for free bone transfer to tibial defects are as follows:

• Severely comminuted fractures or wide bone loss greater than 6 cm (grade 3a-3c from Gustilo classification, type III from Byrd classification)

• Wide (>6 cm) en bloc tibial resections for cancer

• Wide bone resection (>6 cm) for congenital pseudoarthrosis of the tibia

Secondary indications for free bone transfer are as follows:

• Wide bone resection of acquired pseudoarthrosis or chronic osteomyelitis following nonunions for failed conventional treatment of fractures

• Short limb (>6 cm) following conventional treatment of fractures or reimplantation of avulsed limb, with or without distraction

• Amputation stump lengthening

• Wide soft tissue coverage of bone defects (< 6 cm) of the lower third of the leg (osteocutaneous-myo-osteocutaneous flap)

The framework of the lower leg is composed of 2 long bones, the fibula and tibia, which are arranged in parallel.

The fibula is thin and long. It can be divided into the body and the upper and lower extremities. The body can be considered a triangular prism. The upper extremity articulates with the articular face of the tibial epiphysis. The lower extremity joins the tibia in the tibiotarsal joint. The fibula provides insertion to many of the muscles of the leg.

The tibia is a long and thick bone. Anatomically, it can be divided into a body and 2 extremities. The body is a triangular prism, with 3 faces and 3 margins. The upper extremity is large and expands in 2 masses that form the tibial plate (which articulates with the femur). The lower extremity presents a basal articular surface and a medial thick protrusion, the medial malleolus, which, together, form the main part of tibiotarsal joint. Laterally, the lower tibial extremity articulates with the fibular lower epiphysis.

The tibia and fibula are also connected along their length by a fibrous membrane termed the interosseus membrane.

These 3 structures together divide the leg into 2 anatomic compartments, the anterior and posterior. The anterior compartment is further divided into anterior and anterolateral by a thick intermuscular fascia.[14]

The anterior compartment has 4 muscles termed the (1) extensor digitorum longus; (2) extensor hallucis longus; and (3) peroneus tertius, which originates from the fibula, and (4) the tibialis anterior, which originates from both bones. All together, these muscles bend and medially flex the feet. These muscles are vascularized by anterior tibial vessels and innervated by the deep peroneal nerve. Both vascular and nervous structures run deeply along the interosseous membrane.

The anterolateral compartment holds 2 muscles, the long and short (brevis) peroneus. Their action consists of extension, medial torsion, and abduction of the feet. They are vascularized by vessels from the peroneal artery and innervated by the superficial peroneal nerve (which runs deeply in the upper two upper thirds and then becomes superficial to the lower one third of the anterior skin of the leg).

The posterior compartment is divided into superficial and deep by a thin intermuscular fascia. Three muscles are located in the superficial compartment, termed the gastrocnemius, soleus, and plantaris. The gastrocnemius and plantaris originate from the femur, while the soleus originates from the fibula and tibia. The gastrocnemius and soleus join together in a thick tendon that inserts into the calcaneal bone (tendo calcanea). The plantaris is a thin muscle, the tendon of which medially follows the bigger triceps tendon to insert into the calcaneal bone. All of these muscles extend the feet (the gastrocnemius also bends the leg on the thigh) with a little medial torsion. They are vascularized by vessels from the popliteal artery and innervated by branches of the tibialis nerve from the popliteal fossa. The lateral portion of the soleus is also fed by branches from the peroneal artery.

The deep compartment contains 4 muscles termed the popliteus, flexor digitorum longus, flexor hallucis longus, and tibialis posterior. The popliteus helps bending of the knee and medially rotating the leg; the other muscles extend and medially rotate the feet and bend the toes.

The blood supply of the area is provided by 2 arteries, the tibial posterior and the peroneal. The first, which is a terminal branch of the popliteal artery, runs along the tibial posterior muscle, moving medially. It provides nutritional vessels for the muscles of the medial side of the compartment and an artery for the tibial bone.

The peroneal artery originates from the posterior tibial artery approximately 3-4 cm from the division between the popliteal and anterior tibial arteries. This artery runs laterally and downward along the fibula. It provides arteries for the surrounding muscles, an artery for the fibula (approximately 17 cm from its origin), and many perforating arteries for the lateral skin of the leg.[15]

A single nerve, the tibial nerve, innervates the compartment. It runs deeply in the first half of the leg and then moves medially and superficially.

The sciatic popliteal nerve runs subcutaneously at the level of the head of the fibula, where it passes around its neck, to deeper into the muscles of the anterior compartment.

The following are contraindications to free bone transfer to tibial defects:

• Crushing or avulsion injuries with jeopardized lower limb vascularization (high risk of failure of vascular anastomosis)

• Crushing or avulsion injuries with severe motor and sensitive nerve damage (better functional recovery with below-the-knee amputation and prosthetic rehabilitation)

• Severe, multiple lower limb joint compromise (better functional recovery with below-the-knee amputation and prosthesis rehabilitation)

• Severe bilateral lower limb fractures (no safe donor area available)

• Total amputations in which the segment may be reimplanted first and, if shortened, only then subsequently lengthened

Tetanus prophylaxis is usually administered to patients with open trauma. Specific antibiotic therapy based on the results of cultural samples is administered if necessary.

Trauma

Perform emergency nonsurgical reduction of the fracture and immobilization. Daily dressing changes with peroxide solution and saline washes are indicated to control infection. Wound debridement is also indicated.

Timing of reconstruction in open fractures has always been a matter of discussion. In fact, performing primary closure of traumatic wounds with tissue viability that is still in question is often discouraged; however, primary flap cover within 72 hours has been determined to yield better results and a lower infection rate than delayed or late closure. Therefore, an early reconstruction may underestimate or overestimate the amount of bone to excise and replace, while a delayed reconstruction may be at higher risk of infective and vascular complications. The timing of bone reconstruction depends on the time passed from injury at the first referral of the patient, on soft tissue involvement and viability, and on the width of the bone gap to be filled.

Within the first 72 hours after the trauma, simple lesions with limited or no soft tissue involvement are treated immediately with radical debridement and bone grafting or bone flap transfer in one stage. Complex lesions with soft tissue involvement are treated with muscle free flap and delayed bone grafting or a one-stage free osteomyocutaneous flap.

Patients referred 72 hours after trauma usually present with infected wounds and require debridement and delayed reconstruction. In summary, see the following:

• Immediate reconstruction (within 72 h)

  • One-stage surgery - Soft tissue and bone reconstruction (muscle flap and bone grafts/osteocutaneous-osteomyocutaneous flap)

  • Two-stage surgery - Soft tissue cover (pedicled free muscle flap); bone reconstruction (bone graft/flap)

• Delayed reconstruction (>72 h)

  • One-stage surgery - Soft tissue and bone reconstruction (muscle flap and bone grafts/osteocutaneous flap)

  • Two-stage surgery - Soft tissue cover (pedicled free muscle flap); bone reconstruction (bone graft/flap)

Usually, reconstruction of the tibia for open fractures is a function of the characteristics of the bone gap (≥ 6 cm) resulting from wound debridement and fracture reduction and of the characteristics of soft tissue damage (local or free flap).

Tumors

The choice of the reconstructive procedure depends on the primary pathology. Malignant bone neoplasms usually require wide resection with at least 2 cm of free tumor margin and, occasionally, en bloc resection of regional muscles and overlying skin with the biopsy site and nodal clearance.

Enneking has proposed a treatment protocol for staged bone lesions, in which G0 is benign, G1 is low-grade malignant, G2 is high-grade malignant, T0 is intracapsular, T1 is extracapsular/intracompartmental, and T2 is extracapsular/extracompartmental.[11] See the following:

• Tumor stage IA and type G1, T1, M0 - Local wide resection

• Tumor stage IB and type G1, T2, M0 - Wide amputation

• Tumor stage IIA and type G2, T1, M0 - Local radical resection

• Tumor stage IIB and type G2, T1, M0 - Radical amputation

• Tumor stage IIIA and type G1-2, T1, M1 - Palliative treatment

• Tumor stage IIIB and type G1-2, T2, M1 - Palliative treatment

The resulting complex defect often requires a free osteo-osteocutaneous-osteomyocutaneous reconstruction to avoid amputation. Surgical treatment is usually augmented by systemic adjuvant or postoperative chemotherapy.

Osteomyelitis

Sequestrectomy and resection of scarred and infected bone and soft tissue are needed to eradicate infection and achieve a viable vascular environment. Plan the reconstruction after the defect is evaluated.

Pseudoarthrosis

Treatment depends on the age of the patient and the severity of the disease. In advanced stages, when gaps larger than 3 cm must be filled or when conventional bone grafting has failed, a free vascularized fibula graft is the treatment of choice.

Bone reconstruction technique

Bone defects smaller than 6 cm with little or no soft tissue damage following traumas (Gustilo stage 1-2, Byrd stage I-II) and resection of tumors with acquired or congenital pathology are treated as described below.

Generally, in patients with traumas or resections of acquired or congenital pathologies who present with a well-vascularized bed and little or no soft tissue damage, bone defects smaller than 6 cm can be repaired easily with autologous transplantation of devascularized cancellous bone harvested from the iliac crest and stabilized with external fixation. With this technique, nearly 90% of patients with a defect no larger than 2.5 cm achieve bone union, with low morbidity at the donor site. Currently, no unequivocal reports exist regarding the percentage of bone unions for gaps of 2.5-6 cm.

The autologous transplantation of cancellous bone usually results in poor results, often complicated by stress fractures. The primary limitations of the use of cancellous bone are (1) the quantity of bone tissue available (defects >6 cm are difficult to fill) and (2) the prolonged immobilization time required before complete functional recovery and full-load stability.

Bone defects larger than 6 cm with little or no soft tissue damage following traumas (Gustilo stage 1-2, Byrd stage I-II) or resection for acquired or congenital pathology are treated as described below.

When the bone defect is larger than 6 cm, the transplantation of cortical bone is indicated. Enneking has successfully treated skeletal defects as wide as 25 cm with single or double devascularized fibula grafting, reporting a union success rate of 67% for gaps of 7.5-12.5 cm, with an incidence rate of stress fractures of only 17%.[16] A similar success rate of 68% was reported for gaps of 12.5-25 cm, with a higher incidence of stress fractures (58%).

Cortical bone autotransplants have limitations. A long period for revascularization is required. A long incorporating and remodeling time, undergoing creeping substitution, is necessary. Spontaneous stress fractures may occur late (reported to occur as many as 3 y after surgery). Finally, late stress fractures cause pseudoarthrosis at the fracture site in approximately 33% of these patients. Nevertheless, the success rate reported encourages the use of this technique for the reconstruction of long bone defects, especially following tumor resection.

The biomolecular basis responsible for the incorporation of these devascularized bone transplants is termed creeping substitution. This does not occur if (1) vascularization at the bed site is not good; (2) infection is present at the bed site; (3) soft tissue cover is inadequate; or (4) the bone defect is larger than 6 cm and is associated with comminuted or denuded fragments in a devascularized or infected bed with extended soft tissue damage or following traumas (Gustilo stage 3, Byrd stage III-IV), resection for tumors, or acquired or congenital pathology.

In patients with bone defects larger than 6 cm in devascularized and/or infected bed sites, the use of autologous microvascular bone flaps is the method of choice.

The free fibula-protibia transfer is not an innovative procedure in the orthopedic field but can be considered the evolution of an old intuition by orthopedic surgeons, such as Putti, who were transferring the fibula as a nonvascularized graft to reconstruct congenital absence of the tibia. It is also the result of the recent biological advances in tissue vascularization and bone microcirculation of fractures treated with autologous bone transplantation.

Furthermore, the fibula is not essential for load-bearing and ambulation, but it can be used to reconstruct the tibia when the main support of lower the leg is no longer able to fulfill its function. The choice of a single- or double-barrel fibula depends on the characteristics of the gap and the need for support.

Lee and Park report a 93% success rate for the microsurgical reconstruction of traumatic tibial defects.

Soft tissue reconstruction

The choice of the soft tissue reconstructive procedure mainly depends on the location and extent of the soft tissue defect. Usually, soft tissue reconstruction is mandatory for open fractures and for resection related to osteomyelitis, but it is questionable for closed fractures and for resection related to pseudoarthrosis or tumors.

A retrospective study by Rubio-Yanchuck et al indicated that in patients with distal tibial fractures, the need for flap coverage in corresponding soft tissue injury was greater in association with external fixation (odds ratio [OR] 12.5), open fractures (OR 5.25), high-energy trauma (OR 1.7), skin necrosis, and vascular alterations on angio computed tomography (CT) scan.[17]

Soft tissue reconstruction has been clearly demonstrated to affect fracture healing and callus formation in open fractures. For defects of the superior third of the leg, use the medial/lateral gastrocnemius, free muscle flap, or free osteocutaneous fibula (Clinical Case 3; see the images below).

For defects of the middle third of the leg, use a soleus flap, a free muscle flap (Clinical Case 4; see the images below).

Another option for defects of the middle third of the leg is a free osteocutaneous fibula (Clinical Case 1, see the images below).

For defects of the inferior third of the leg, use a free muscle flap or free osteocutaneous fibula (Clinical Case 2; see the images below).

Bone stabilization

The choice of bone stabilization depends on the bone reconstruction technique chosen. Free cancellous bone grafts warrant external fixation. Free cortical bone grafts warrant external fixation, external and internal fixation, and internal fixation. Free vascularized bone flaps warrant external fixation and inlay fibula (see the images below), external fixation and onlay fibula with or without a step cut and compressive screws, internal fixation by inlay fibula and intramedullary nail, or internal fixation by onlay fibula with or without a step cut and compressive screws.

To obtain a faster healing of the fracture lines, some cancellous bone chips obtained from the iliac crest may be used.

Other considerations

The ablation of tibial tumors usually results in massive loss of tibial bone (often >6 cm), with possible preservation of soft tissues and vascular pedicles. In these patients, the reconstructive procedure first appears to be less problematic compared to high-energy traumas, but the use of adjunctive treatments such as chemotherapy or radiotherapy often compromises the result of the reconstruction. For example, these adjunctive treatments may affect the rapidity of bone union and the hypertrophy of the fibular bone.

The use of the free fibula flap for the reconstruction of tibial defects following resection for chronic osteomyelitis has not always yielded satisfactory results. Among the factors that influence these results are fibrosis of the soft tissues surrounding bone and vascular structures and resulting venous hypertension. Internal fixation methods have been avoided to reduce the risk of exacerbating the osteomyelitis.

The treatment of congenital pseudoarthrosis has always been problematic because of the difficulty of matching the different lengths of the tibial bones in young patients during growth age and because of the possible complications following free fibular transplant in children, such as valgus deformity of the tibia or ankle and rigidity and atrophy of the ankle. Nevertheless, free fibula transplantation remains the technique of choice. Regarding this, remember that in young patients, transplanting fibular bone, with its epiphyseal growing nucleus, is possible to reconstruct contralateral bone and restore limb growth.

With the use of the fibula flap, the peroneal artery of the donor limb is sacrificed. A preoperative evaluation of the vascular flow to the donor leg must be performed to avoid iatrogenous ischemia of the foot. The same evaluation must be conducted on the recipient leg to assess for the presence of valid arterial inflow and the absence of a peronea magna anomaly.

In addition to a clinical evaluation of the pulses of the anterior tibial artery at the level of the dorsal surface of the foot and of the posterior tibial artery at the level of the medial malleolus, an instrumental evaluation also must be in the routine. Currently, color Doppler ultrasound scanning is the procedure of choice to assess vascular patency and flow directions, while angiography or arteriography is left for doubtful cases.

Fibula harvesting is discussed below.

Osseus flap

Position the patient supine on the operating table. Raise the flap under ischemia with the patient's knee flexed 90° and the foot fixed to the table with the girdle interiorly rotated.

Carry an incision on the edge of the fibula, which is palpable under the lateral side of the leg. Identify and preserve the sciatic popliteal external nerve, which runs under the head of the fibula. Dissect the peroneal muscles off the anterior face of the fibula, and incise the lateral septum to gain access to the extensor compartment. Dissect the extensor hallucis longus and digitorum longus free until the anterior tibial vessels, the tibial nerve, and the interosseus membrane are identified.

Carry the dissection posteriorly by incising the flexor compartment and dissecting the gastrocnemius, soleus, and flexor digitorum longus off the posterior face of the fibula. Identify the peroneal vessels proximally and distally.

With a reciprocating saw, osteotomize the fibula distally and proximally to harvest exactly the required length of bone. Section the peroneal bundle distally while the interosseus membrane is exposed and incised.

Completely retract the segment, and dissect the pedicle up to its origin at the level of the bifurcation from the posterior tibial artery. Spare the proximal 3 cm and distal 5 cm of fibula to protect the external sciaticus popliteus nerve and ankle stability.

The segment of fibula harvested may measure as long as 26-30 cm and as wide as 1.5 cm. The graft is usually remodeled in place before the pedicle is cut.

Depending on the type of osteosynthesis chosen, the bone ends are rounded with the use of a rotating drill to be more easily infibulated in the tibial medullary cavities or step cuts are performed at the fibula ends if osteosynthesis with compression screws is planned. Once the graft is customized and the recipient area is ready, cut the pedicle free and transfer the flap into the defect. Place Redon drainage for continuous suction of the wound near the fracture site.

A purely osseus flap is rarely used in the reconstruction of traumatic tibial defects because of its frequent association with soft tissue damage and because of the postoperative edema, which makes primary wound closure difficult. An osseous flap is indicated in the reconstruction of tibial defects following resection for pseudoarthrosis, but it is rarely used for tumors or osteomyelitis.

Recipient tibial area

After debridement or en bloc excision, in a clean and vascularized recipient bed, stabilize the tibial stumps with the aid of an external fixation device and prepare the medullary cavities to receive the graft.

Accomplish bone osteosynthesis of the fibula flap through infibulation or step osteotomies and compressions screws. Cancellous bone chips may be used adjunctively at the level of the osteosynthesis to improve healing.

A vascular anastomosis is usually performed with the posterior tibial artery and vein in a lateroterminal pattern in a safe zone, more often at the level of the ankle. The fibula flap also may be used as a flow-through flap to revascularize the leg, with the ends of the fibular artery anastomosed to the stumps of the posterior/anterior tibial artery to reconstruct its continuity.

In 1993, Banic and Hertel offered 2 suggestions for an earlier recovery of stability and load-bearing.[18] The first is to use a double-barrel free fibular vascularized flap. The second is to put cancellous bone between the fibula-tibial interface.

When bone gaps smaller than 10 cm are to be repaired, a whole-length fibula may be split in 2 segments vascularized from the same pedicle. If the gap is larger than 10 cm, a double-fibula free flap is preferred. A double-strut free vascularized fibula can withstand a higher torque and mechanical stress than single strut.

Donor area

Once the fibula graft is removed, seal the fibular stumps left in place with bone wax. Release the tourniquet and obtain hemostasis. Place a suction drain in between the muscles, exiting at the inferior limit of the skin incision. Suture the peroneal muscles to the soleus, and repair the fascial layer and the skin. Apply a protective cast to hold the ankle in correct functional position during healing.

The morbidity of the donor area of the fibula bone flap is negligible in adults. In children, some instances of tibial curvature and of valgus deformity of the ankle have been reported. Thus, a distal tibiofibular fusion is recommended in children to avoid valgus deformity of the ankle.

Osteocutaneous flap

See the images below. Harvest the skin flap, including the deep fascia of the leg along its longitudinal axis, in correspondence with the posterior intermuscular septum of the leg, which separates peroneal from soleus muscles.

Skin vascularization comes from 3 types of perforating vessels originating from the peroneal artery. The first type is the fasciomyocutaneous branches, which are located mainly in the superior third of the leg and run through the soleus muscle. The second type is the septal branches, which are present along the leg, vascularizing both the muscles and the skin. The third is the fascioseptal branches, which give blood to the skin only but are missing in 20% of patients.

Always close the donor area with a skin graft when the skin paddle is larger than 6 cm. Harvesting of the osteocutaneous flap may produce limitations of hallucis flexion and cosmetic defects due to skin grafting of the lateral leg.

Osteomuscular flap

The entire lateral half of the soleus muscle can be harvested together with the fibula flap. The dissection is similar to that already described except that after completing the anterior dissection of the fibula, carry this in a posterior plane located between the lateral head of the gastrocnemius and the soleus until the midline of the soleus is identified.

At this level, the dissection deepens laterally among the soleus and the flexor longus hallucis until the peroneal vessels are identified. The osteomuscular flap may be particularly indicated in trauma patients with extensive soft tissue damage and dead space that must be filled.

Position the patient supine, possibly on an air/water mattress, with both legs slightly elevated. The donor leg is held in functional position by an elastic bandage or a protective cast. The recipient leg is usually held in position by an external fixation device and wrapped in a soft bandage with a window for frequent inspections.

Evaluate suction drains daily and remove them only when 20-30 mL of serum is collected. Perform continuous washing drainage of the recipient area with isotonic sodium chloride solution or 30% povidone-iodine solution, mainly in trauma patients. Continue until no more blood or corpuscular secretion is drained (usually 7 d).

If a skin graft has been applied to the donor leg, remove the dressing together with the stitches on the fifth day. No ambulation is allowed within the first 2 weeks.

After 2-3 weeks, the donor area has also healed. Remove the cast or elastic bandage and ask the patient to walk on the donor leg with the aid of crutches. The external fixation device used to immobilize the fibula flap and to stabilize the osteosynthesis is left in place, and the patient is discharged.

Maintain the fixation method until radiologic findings demonstrate a good osteointegration and integration of the graft. Usually, the external fixation device is removed after complete bone union is accomplished (generally 10 wk). Full load-bearing capacity is recovered gradually, and it is recovered completely only after 4-6 months postsurgery. Functional rehabilitation of the joints may be started early after surgery, eventually substituting the external fixation device with an orthopedic tutor.

With the aid of a Doppler probe, monitor the viability of the free fibula flap in the early postoperative period every hour the first day, every 2 hours the second and third days, and 4 times per day until 2 weeks postoperatively to check the patency of the microanastomosis and to survey the skin or muscle island perfusion.

Evaluate bone union with serial radiographs or bone scans at 1 month, 3-6 months, and 1 year following surgery (see the images below). Radiologically, bone union is achieved when continuity is obtained in 2 planes and the fracture line has disappeared. Stress fractures or curvature can be easily identified.

A comprehensive rehabilitation program including early static quadriceps exercises is started on the third day, passive stretching and mobilization of all joints is begun after 1 week, and subsequent active mobilization follows.

Later, non–weight-bearing, protected mobilization is followed by limited and full weight-bearing exercises and gait analysis. Assess patients for complications, time to bone union, and functional recovery. Bone union is achieved clinically when full weight bearing without splints or pain is obtained. Functional recovery is achieved when full mobilization without aids or splints and an acceptable range of joint motion are achieved (see the images below).

Complications may be divided into general and specific, and specific complications can be related to the recipient or to the donor area. General complications are those related to each surgical procedure (eg, reaction to anesthetics, hematoma, seroma, infection).

Specific complications are those related to fibula harvesting, tibial reconstruction, and free flap surgery. Specific complications related to the donor area may be divided into early and late complications. Other than a 2% incidence of infection, the most common early complications reported are decreased flexion power of the big toe, paresthesia, dysesthesia of the dorsum of the foot, and, only rarely, foot ischemia and lesions of the sciaticus popliteus nerve with loss of foot dorsiflexion. Other common perioperative complications are skin graft loss, cellulitis, wound dehiscence, and abscess.[19] Among the 27% incidence of late complications reported, the most common are edema, pain with ambulation, stiffness of the ankle, hypertrophic scarring, and, only rarely, instability and tibial curvature in children.

Fibular harvesting does not cause any relevant functional deficit to adults, while a few incidents of tibial curvature and valgus deformity of the ankle are reported in children.

Early complications related to the recipient area are arterial or venous thrombosis of the anastomosis, ischemia or congestion of the skin island, soft tissue infection and breakdown, limb shortening or lengthening, and, only rarely, posterior tibial artery thrombosis.

Late recipient site complications are stress fractures (up to 40%; average, 25%), instability of the osteosynthesis, delayed bone union, nonunion, pseudoarthrosis, tibial malalignment or recurvatum, and pain and/or edema after long-distance walking.

With regard to microvascular complications, the bone flap may tolerate venous thrombosis because of spontaneous bleeding from the medullary canal, but vein drainage of the skin paddle must be supported with leech therapy. In the worst scenario of an arterial thrombosis, the fibula can survive in place as a simple graft. On the contrary, the skin island is very delicate because it relies on few and small perforating vessels and is very sensitive to circulatory changes.

Lee and Park reported a 93% success rate in the reconstruction of extensive tibial fractures with free vascularized fibula flaps.[20] Of 46 patients, 43 achieved bone union after an average of 3.75 months (range of 3-7 mo) from surgery. Partial weight bearing was started after bone union with the aid of crutches or splints.

Free fibular transplantation following cancer resection often achieves lower success rates than the same procedure used for traumas.

In 1992, Han and coworkers reported the results of 69 patients affected by bone cancer who underwent tibial resection and reconstruction with the free fibula; 46 patients (67%) obtained bone union, while another 10 needed a further procedure for bone union, bringing the success rate to 81%.[21]

Han and coworkers also reported the results of 60 patients affected by chronic osteomyelitis who were treated with free contralateral fibula flaps and achieved a primary union success rate of 48%.[21] After a second procedure, the final success rate was 77%.

In 1983, Weiland et al reported a bone union rate of 60% in 13 patients.[22] Free fibula transplantation remained the technique of choice for congenital pseudoarthrosis. Gilbert and Wood reported 43 cases of congenital pseudoarthrosis treated with free fibula protibia from 1976-1992, some of whom were operated on several times and observed for up to 5 years, with a final success rate of 91%.[23] Morrissy and colleagues reported lower success rates in 40 patients, with a union rate of 55%.[24]