Advantage and Indication
The use of external fixation is less invasive, can achieve adequate stability, and provide good access for wound management without compromising stability10. Vascular injuries of the lower legs, if not treated early and competently, are a major cause of limb amputation and even life-threatening, limb salvage is critically dependent on ischemic time11. In 1963, Malan and Tattoni12 introduced the concept of the 6-h rule for re-vascularization, and most authors used 6h as the definition of early intervention, however, skeletal muscle and nerve are, in fact, even more sensitive to ischaemia13,14. Glass et al15 in a Kaplan-Meier survival curve analysis, demonstrated that limb salvage begins to fall almost immediately the time when any further delay results in a rapid decline in survival, which begins at about 3-4 h. So, the time of re-vascularization should be as short as possible to minimize ischemia time and re-perfusion time, thus prevent potential necrotic changes and ischemia reperfusion injury, which is the key to limb salvage.
Reconstruction of the bone framework is one of the important steps in the surgery of vascular repair, and the surgical sequence has been the subject of debate. Some surgeons advocated arterial repair before fracture fixation suggests that this method minimizes ischemic time16–18. Others suggest that by performing skeletal fixation first, the requirements for vascular reconstruction can be better measured, and stabilization avoids iatrogenic disruption to the subsequent vascular repair19. Iannacone et al4 suggested that immediate external fixation allows the vascular repair to be performed in a controlled environment to protect the completed vascular repair from disruption. Our experience suggested that the use of external fixation technology to enable skeletal fixation prior to vascular repair has yielded satisfactory results in the treatment of vascular injuries of the lower legs. Also, researchers say that we should pay attention to the dynamization of fracture fixation to improve the fracture healing process. In the bone healing process, stabilizing elements of the fixator are removed at some time during the treatment leading to greater flexibility of the fixation and it gets good results.20
The application scene of external fixation
Though external fixation has many advantages, we should also know that only when we use external fixation properly will we get satisfactory results. A prospective study of 59 patients with Grade II or III open tibial shaft fractures compared internal and external fixation shows that the rate and extent of complications are lower with external fixation though both methods yielded excellent results21. Another RCT shows that external fixation is a satisfactory method of treatment for fractures of the tibial plafond and is associated with fewer complications than internal fixation22. Through another RCT, Leung et al drew a conclusion that plate fixation combined with percutaneous pin fixation for the treatment of intra-articular fractures of the distal part of the radius is better than external fixation23. Other researchers such as P Pairon agrees with the idea that external fixation is a safe option for stabilisation of extremity lesions in the polytraumatised patient as well as in fractures with severe soft tissue damage. Even so, he also mentioned that stable polytraumatised patients who could not benefit from initial stabilisation with an external fixator should immediately be treated with a definitive osteosynthesis24. Our study suggests that we should choose the proper fixator in order to improve patients’ prognosis rather than use external fixator without taking patients’ situation into consideration.
Furthermore, another viewpoint we should consider. Zi-Chen Zhao demonstrates that combined fixation is an effective and safe alternative for management of open tibial diaphyseal fractures compared with external fixation25. In actual circumstances, we may choose the proper fixation method depended on types of fracture, ages of the patients et al.
Complication
Pin tract infection is one of the most common complications of external fixation. Occurring in 10.3% of our patients is comparable to those of 9.4–30% reported by other studies26,27. Infection varies from minor inflammation remedied by local wound care; to superficial infection requiring antibiotics, local wound care, and occasional pin removal; to osteomyelitis requiring sequestrectomy. Higher rates of pin tract infection are seen when the pins are placed through large volumes of soft tissue (for example, thigh)10. So external fixator pins should be applied outside the zone of injury to span the zone of injury to minimize soft-tissue insult. Pins placed within the zone of injury are disadvantageous, which provided access for bacteria to invade potential space created by soft-tissue disruption, and their associated hematoma can cause deep infection. For different degrees of the pin tract infection, Checketts et al28 devised a classification system that aids in the formulation of treatment options.
Pin-bone interface loosening or failure mainly with bone resorption around needles, full weight-bearing too early, fracture gaps > 2 mm of unstable fracture, osteoporosis and so on. External fixation failure includes the pins and link rod crack and bending deformation. Repeating bending makes the metal fatigue, is a major cause of external fixation failure29.
Another common complication of external fixation is bone nonunion. Our study showed bone nonunion rate was 20% (16/80), considering that the original restoration is not satisfied, fracture gaps too large, severe soft tissue injury. Cross and Swiontkowski30 demonstrated as high as 13% bone nonunion rate using the external fixator, which was related to improper surgical technique, inaccurate fracture reduction, the initial severe trauma and the lack of elastic fixation changing in time. Menon31 demonstrated the early period static fixation, middle and later period elastic fixation could be beneficial to the bone union. The main reason for bone malunion is that the original restoration is not satisfied, the incidence of relative angular deformity was higher than rotational deformity, so the ideal fracture reduction should be performed as well as possible before placing pins, instead of excessive dependence on external fixator adjusting.
The general techniques for using external fixators are demanding, regardless of the specific fixator selected. Attention to detail is essential if the maximal advantage of the external fixator is to be gained and potentially serious complications are to be minimized. The initial treatment of the condition for which the external fixator is chosen must be considered first: irrigation, debridement, and reduction of the severe, open fracture; drainage, debridement, and sequestrectomy of the infected fracture. Furthermore, the surgeon must be familiar with the cross-sectional anatomy of the limb and with the relatively safe zones and danger zones for pin insertion. In addition, Hadeed demonstrated that two methods can be used to improve the stability of the pins. In the one hand, the operator should place pins closer to the fracture site, add more pins and increase the spread of the pins in order to improve the stiffness of the construct. In the other hand, he may increase the diameter of the rods or secure it closer in proximity to the bone32. By the way, the application of new materials of the pin such as hydroxyapatite-coated external will strongly enhance pin fixation.
Management of arterial injuries
To recognize the vascular injury after surgical stabilization of trauma is vital for limb stability. Certain orthopedic injuries known to be associated with vascular injury are knee dislocation (especially posterior) and proximal tibial and fibular fractures, according to Treiman et al33, up to 23% of patients suffering knee dislocations had popliteal artery injuries. When making a diagnosis of vascular injuries, careful physical exam sensitive and specific, angiography should be used sparingly, the role of Color Flow Doppler is evolving. By the way, CT angiogram is recommended for use in the operation, for it has a high selectivity and specificity, and it is also noninvasive and requires less radiation34. Collateral arterial supply to the lower limb is frail and easily disrupted by soft tissue swelling or thrombosis, and thus the lower leg is almost totally dependent on the major trunk artery such as the popliteal artery, anterior tibial artery, and posterior tibial artery. An amputation rate of 16% following popliteal artery injury was reported by Hafez et al35, and Andrew et al36 demonstrated that the popliteal artery is vulnerable to injury from fractures or dislocations because it is tethered to both the distal femur by the adductor hiatus and the proximal tibia by the tendinous arch of the soleus muscle.
The key points of treatment are minimized preoperative delays, the primary end-to-end anastomosis is the first choice for repair, if interposition grafts are required, auto logous vein graft is preferable to synthetic material, because a reversed saphenous vein graft from the contralateral limb has clearly superior patency rates, also can avoid foreign body in vivo37–39. Injury to veins should be repaired to minimize postoperative swelling, and compartment syndrome, which is a major risk factor for amputation following artery injury. There is evidence that fasciotomy done at the time of arterial repair, but before the development of compartment syndrome (prophylactic fasciotomy), may lower amputation rates40. Thrombosis is an important complication to suspect following arterial repair because it is both common and correctable. Heparinisation and routine monitoring of distal pulses postoperatively may reduce the incidence of thrombosis and allow for more rapid diagnosis when present.