Blast injury to bilateral lower extremities with right-leg Gustilo-type 3C fracture . Figure revealing the extensive surrounding soft-tissue damage caused by the blast wave
Types of blast injuries 
Type of blast injury
Blast wave and injury to air-filled organs
Shrapnel and projectile fragments
Structural collapse and displacement of the victim’s body as a whole
Burn and chemical injury
Infectious, chemical, or radioactive weapons
Serial aggressive debridement until achieving a stable wound without further tissue necrosis.
Removal of all foreign body loading.
Ensure an infection-free wound or with low bacterial contamination load prior to reconstruction.
Analyze the defect in a three-dimensional fashion (skin, soft tissue, muscle, bone) or reproduce the defect in delayed cases as shown in Fig. 9.2 (Table 9.2) with adequate prereconstruction planning .
Chronic presentation with healed wound postexplosive bullet injury . (a) Left-leg 14-cm bone defect. (b) Free fibula osteocutaneous flap harvest, inset, and fixation with plate and screws. (c) Six-month postoperative images with X-ray revealing an integrated hypertrophied vascularized fibular bone and full weight bearing on the injured leg
Gustilo and Anderson classification of open tibial fractures and bone exposure 
Open fracture with a wound <1 cm
Open fracture with a wound >1 cm without extensive soft-tissue damage
Open fracture with extensive soft-tissue damage
Type III with adequate soft-tissue coverage
Type III with soft-tissue loss with periosteal stripping
Type III with arterial injury requiring repair
In the setting of osteomyelitis , a muscle component in any flap type is considered the gold standard for reconstruction supplemented by antibiotics.
Timing of Reconstruction
Optimal timing of lower extremity reconstruction is debatable. Initial outcome studies by Gustilo, Byrd, and Godina in the late 1970s and early 1980s proposed that microsurgical reconstruction of traumatized lower extremities is best performed in the first week after injury [6–8]. Godina reviewed a series of 532 patients requiring free-flap transfer in extremity reconstruction and noted a 0.75% flap failure rate for flaps performed in the immediate phase (less than 72 h after injury), 12% failure rate of flaps performed within the delayed phase (3 days–3 months after injury), and 9.5% rate of failure in the group receiving flap coverage in the late phase (more than 3 months after injury) . In our experience, we could not find any difference in outcome between the three phases.
Intimal damage from the blast wave contributes to the pathogenicity of vascular complications in the acute period following injury [8, 9]. This principle underscores the importance of careful microvascular anastomosis outside the zone of injury, particularly within the acute phase of injury .
In war injuries, immediate reconstruction is often not applicable due to associated injuries, resuscitative needs, patient stabilization, and logistical delays starting from patient transportation to surgical scheduling .
Our primary goal is wound closure as soon as possible preferably within 7–10 days after injury to decrease the risk of infection, osteomyelitis, nonunion, and further tissue loss . Byrd et al. reported an overall complication rate of 18% for wounds closed within the first week of injury as compared to a 50% complication rate for wounds closed in the subacute phase (1–6 weeks after injury) [12, 13].
Parrett et al. highlighted that optimal synchronization between orthopedic surgeons and plastic surgeons results in better treatment in their retrospective review of 290 soft-tissue reconstructions over open tibial fractures .
Negative-Pressure Wound Therapy (NPWT )
First described by Fleischmann, NPWT was introduced as a semiocclusive dressing and a suction device over an open fracture .
The principles governing NPWT are the following:
Contraction of the wound (macrodeformation )
Stabilization of the wound environment
Removal of extracellular fluid
Microdeformation at the foam-wound interface 
Rezzadeh et al. demonstrated lower overall complication rates with NPWT compared to conventional wound care in the management of mangled lower extremities with Gustilo grade IIIB or IIIC open tibial fractures .
We strongly agree with Liu et al. that NPWT is considered a bridging tool either to buy time until complex reconstruction with a free flap is achieved or to provide granulation tissue in small wounds that can be covered with a skin graft .
Management of bone defects strongly depends on the length of the existing gap. Three modalities for bone reconstruction are:
Nonvascularized cancellous bone grafts , best used for nonunions or small bone gaps of less than 5 cm 
Bone lengthening or distraction osteogenesis for defects of 4–8 cm 
Vascularized bone grafts with an average healing time of 6 months ideal for defects greater than 5 cm as shown in Fig. 9.2
Composite defect (bone, muscle, skin, and tendon with or without nerve loss) reconstruction is considered more complex. It is important to analyze the defect in a three-dimensional fashion in order to distribute skin paddles according to the perforating vessels to cover the defect as shown in Fig. 9.3. The skin paddle is also important to monitor the viability of the flap ; however, when the perforators are damaged or not available, an internal Doppler might be used to monitor the patency of the anastomosed vessels. A muscle component can be included within the flap to cover any infected bone or for additional soft-tissue coverage whenever the skin paddles are not enough.
Subacute presentation 3 weeks postblast injury to the right leg . (a) Composite defect consisting of a 12-cm tibial bone defect, fibular fracture, and 80% soft-tissue loss of the distal third of the leg. (b) Free fibula osteomyocutaneous flap harvesting and tailoring the proximal skin paddle to cover the lateral aspect of the leg, the distal skin paddle to cover the medial aspect of the leg, and the soleus muscle to cover the anterior defect in between the two skin paddles. (c) Six-month postoperative images with the X-ray revealing an integrated hypertrophied vascularized fibular bone
Composite defect reconstruction is either performed in a single stage using a single chimeric flap (bone, skin, and/or muscle) or a double free flap or in two stages by providing soft-tissue coverage and bone spacer as first step followed by bone reconstruction at a later stage [20, 21].
We prefer a one-stage reconstruction using a vascularized free fibula osteocutaneous or osteomyocutaneous flap in which variable muscles can be included such as flexor hallucis longus muscle or the soleus muscle . We believe that a one-stage reconstruction hastens recovery, lowers costs, prevents adjacent soft tissue and recipient vessel scarring, avoids repeated microvascular tissue transfer, achieves early structural stability of the bone, promotes bone union, improves success rates of infection resolution, and reduces overall healing time of severe complex injuries of the lower extremities .
Reconstruction According to Anatomical Region
The hemigastrocnemius or the soleus , but not both, is the armamentarium of choice for knee soft-tissue reconstruction. The gastrocnemius muscle flap may also provide functional reconstruction of the knee extensor mechanism as described by Patel et al. . These flaps often require a skin graft for coverage. Local fasciocutaneous flaps such as the anterior tibial artery perforator flap could also be adopted as reliable coverage for patellar and knee defects, bestowing versatility and flexibility to the reconstructive surgeon’s armamentarium . Another fasciocutaneous flap is the distally based reverse anterolateral thigh flap supplied by retrograde flow through the genicular artery. This flap is not free of complications such as venous congestion and partial necrosis.
Proximal Third of the Leg
Similar to the knee region, soft-tissue reconstruction of the proximal third of the leg is relatively straightforward. Variable local and regional muscle flaps such as the gastrocnemius and soleus muscles are available to cover any exposed bone in the proximal third of the tibia whether it is fractured or not . The medial or lateral head of the gastrocnemius muscle can each be used as a myocutaneous or muscle flap; moreover, both heads of the gastrocnemius muscle may be used as long as the soleus muscle is intact.
Based on any local skin perforator detected by Doppler, a freestyle fasciocutaneous flap can be raised and adopted for coverage of locoregional defects. In blast injury , those locoregional options might not be available due to extensive soft-tissue damage; therefore, a muscle flap with a skin graft might still be the ideal choice for reconstruction.
Middle Third of the Leg
High-energy injuries to the middle third of the leg often result in exposed fractures of the tibia and fibula secondary to the relatively thin soft-tissue envelope anteriorly . Fractures of the middle third of the tibia can be adequately covered by the hemisoleus muscle flap based on branches from the popliteal artery, posterior tibial artery, and peroneal artery. The gastrocnemius muscle may also be used with its medial and lateral heads based on the medial and lateral sural arteries, respectively. Those options might become less reliable or not available the more caudal the injury is and/or the more severe the blast damage is.