1. Spanning external fixation is recommended when definitive stabilisation and immediate wound cover are not carried out at the time of primary wound excision (debridement).
2. Spanning external fixation must be stable to prevent fracture site displacement and pain during patient transfer or movement.
3. Fracture patterns, the quantity of bone loss and degree of contamination at injury will determine the most appropriate form of definitive skeletal stabilisation.
4. Internal fixation is safe if there is minimal contamination at the time of injury.
5. If internal fixation is used at any time for stabilisation, it is mandatory for definitive soft tissue cover to be achieved simultaneously.
6. If exchange from spanning external fixation to internal fixation is planned, it is to be done as early as possible (within 3 days).
7. Modern multiplanar and circular fixators are used if there is significant contamination, bone loss, or multilevel fractures of the tibia.
In this chapter we draw upon published evidence and the experience of the authors to provide guidance in stabilisation for open tibial fractures. Most orthopaedic surgeons have, through their training, reached higher levels of proficiency and expertise in methods of internal fixation than with external fixation. The difference reflects the greater number of fractures treated with internal fixation methods. Consequently, we provide a clear rationale for the recommendations made and encourage adoption of the principles described.
Objectives in provisional stabilisation
Provisional stabilisation must control movement between fracture segments and reduce bleeding and pain. Recovery of soft tissues is facilitated by stable fixation, even if provisional (1). Spanning external fixators achieve this objective but the application should factor in the need for additional surgery; in particular, soft tissue reconstruction. Thus, plastic surgeons need to be involved with their orthopaedic colleagues over configurations of external fixators such that the proposed reconstruction of soft tissue defects is unimpeded by the device. Traction or long leg plaster slabs are not recommended after primary debridement.
Various external fixator systems are available for this purpose and are capable of being applied rapidly and easily. There are several fundamental properties that contribute to stable provisional external fixation including component choice, location of pins and overall fixator assembly.
Choosing appropriate fixator components
The generic components are the half-pin (or screw), clamp and rod. Half-pins and rods should be of a large diameter (2). In adults, 5 or 6 mm half-pins should be selected over the smaller 4 mm, whereas in children 4 mm pins are sufficient. Rods should be greater than 10 mm in diameter for adults and rods less than 10 mm, typically 8–9 mm, can be used in children. The bending stiffness of each of these cylindrical components increases exponentially with the fourth power of the radius; by selecting a large diameter half-pin and rod the surgeon can increase the stiffness of the assembled external fixator without need for duplication of components. This simplifies the configuration and facilitates soft tissue reconstruction by leaving a greater space free for unhindered access.
It was taught previously that the anteromedial surface of the tibia is the safest area to insert a half-pin. Unfortunately, whilst access to drill and insert a pin perpendicular to the subcutaneous surface of the tibia is uncomplicated, the exit point of the drill or half-pin can impinge on either the deep peroneal nerve or anterior tibial artery as both these important structures are situated on the interosseous membrane adjacent to the lateral wall in the proximal three-quarters of the tibia (Figure 6.1). Consequently, we recommend that the pins are inserted 1 cm medial to the crest of the tibia in the sagittal plane (3). Drilling can start perpendicular to the surface of the bone to prevent drill slip but, once the bone surface is entered, the drill should then be brought to a vertical alignment to penetrate the tibia in the sagittal plane. A half-pin inserted in the sagittal plane has the following advantages:
1. It controls displacing forces in the sagittal plane better. For the supine patient, lifting the leg or moving the patient will create displacing forces in this plane from the action of gravity (4).
3. The exit point of the drill or half-pin is buffered by the deep posterior muscles of the leg in the proximal three-quarters of the leg before the posterior tibial neurovascular bundle is at risk. In the distal quarter, these muscles transition to tendons but continue to shield the neurovascular bundle as it locates towards the medial side (Figure 6.2).
Pin placement in the foot has to factor in the local anatomy. Pins from the medial or lateral side into the calcaneum (or transcalcaneal pins in this area) can be inserted safely if sited at the junction of the posterior quarter and anterior three-quarters of a line subtended between the tip of the malleolus and postero-inferior point of the calcaneal tuberosity (Figure 6.3). Blunt dissection down to bone is essential after incision in order to avoid injury to either the medial or lateral calcaneal branches of the posterior tibial nerve. Using a drill sleeve also protects against iatrogenic injury to important neurovascular structures (5, 6, 7).
In addition to a pin in the calcaneum, a second level of fixation is needed if the configuration of the external fixator is to span the ankle. A single transcalcaneal pin is insufficient on its own to provide optimum stability across the ankle joint. The locus for the second pin includes the talar neck, base of first metatarsal, or cuboid.
The half-pin placed into the neck of the talus is inserted halfway between the tip of the medial malleolus and tuberosity of the navicular. Centring the drill is facilitated by ‘walking’ the drill tip anteriorly and posteriorly on the medial surface of the neck until a central position is identified. If this pin is inserted from the lateral side, the contours of the neck of the talus are palpated easily if the entire forefoot is adducted (7). The advantages of using the talar neck as a site for pin insertion are that it allows a pin diameter as large as that used in the tibia (5–6 mm) and the density of bone in this area provides excellent grip—both contribute to the stability of the external fixator.
Half-pins into the base of the first metatarsal should be smaller in diameter (3.5–4.5 mm) in order to avoid iatrogenic fracture after removal and need to be inserted obliquely and not transversely to avoid injury to the dorsalis pedis continuation of the anterior tibial artery (8). The cuboid on the lateral side of the foot accepts 5–6 mm pins but the density of cancellous bone here does not cater for as secure a grip as that of the neck of the talus.
If a knee-spanning configuration is required for open fractures of the proximal third of the tibia, pins placed in an anterolateral direction in the middle-third of the femur have a biomechanical advantage and are safe to insert (9).
Assembling the fixator for stability and facility for soft tissue reconstruction
The simplest stable configuration is assembled.
For middle third fractures, where knee or ankle-spanning fixators are not needed (unless an injury exists in the femur or foot, respectively), a single anterior bar is all that is required. Four pins with two in each segment will suffice provided the pins are placed near to and far from the fracture within each segment (the near–far principle). This spread of pins in each segment exerts an advantageous grip but the caveat is to avoid placing pins within exposed tibia or within the zone of injury.
A simple way to achieve this four pin-single bar assembly is to insert the most proximal and most distal pins first and connect the single bar between them. Traction is applied across the fracture to achieve approximate alignment and the clamps then tightened. The additional two pins closer to the fracture are then inserted through additional clamps attached to the same rod; some improvement to the quality of reduction is possible when these pins are introduced. Such a construct achieves the ‘near–far’ half-pin placement with regard to the fracture site and produces good control of proximal and distal segments of the fracture (Figure 6.4A–D).
When the fracture is situated in the distal third of the tibia, there may be room for a single pin in the distal segment or none at all, e.g. in open fractures of the tibial plafond. In these circumstances, crossing the ankle joint provides additional stability as the short distal tibial portion together with the foot constitute the ‘distal segment’. Pin placement in the foot and ankle requires some thought; the calcaneum, first metatarsal, neck of talus, and cuboid can be used. Two separate pins in the foot provide far better control than a single transcalcaneal pin. Again, control of sagittal plane forces is more important as ankle movement occurs in this plane, as does the displacing effect of gravity during patient movement or transfer. A single half-pin in the calcaneum used with a talar neck or base of metatarsal pin is a good combination. The delta configuration assembled with a transcalcaneal pin and metatarsal pin is a simple stable construct as is the delta frame from the single calcaneal half-pin and talar neck pin. The first assembly involves oblique bars across both sides of the distal tibia which may impede soft tissue reconstruction from both sides (Figure 6.5), whereas the second assembly can be constructed on either the medial or lateral side of the leg in anticipation of soft tissue surgery from the opposite side (Figure 6.6A–F). A ‘kickstand’ bar attached posteriorly elevates the limb and the heel from the bed and is helpful in protection against decubitus ulcers and limb swelling (Figure 6.7) (10, 11).
The primary objectives in treatment are to achieve union without infection and through as few additional operative procedures as possible. Both internal and external fixation techniques have their place. Variables that are considered when deciding on the type of definitive fixation include the fracture pattern, degree and type of initial contamination, timing of definitive soft tissue cover, and the presence of dead space after wound excision. Systematic reviews that have attempted guidance in this area have been hampered by the randomised trials using treatment devices that are now outdated or have included studies with poor precision (12, 13). Future studies may provide clearer advice (14).
Anatomy of the fracture
Fracture patterns are strong determinants of the definitive method of stabilisation: diaphyseal injuries with minimal bone loss are suited to locked intramedullary nails, whereas articular fractures are held well by plates and screws. Injuries with significant bone loss, articular fractures with comminution especially at the metaphyseal level, complex multilevel fractures, and those with associated ankle or knee joint instability are suitable for circular external fixation.
Degree of contamination
Internal fixation should not be used in injuries highly contaminated with road grit, soil, or sewage.
The National Institute for Health and Care Excellence (NICE) recommends that if internal fixation is used, it is essential that definitive soft tissue cover is achieved at the same time. Delayed cover over internal fixation leads to increased and unacceptable infection rates (15, 16, 17, 18).
Internal fixation can be used safely in open injuries which, after wound excision (debridement), can be closed by simple suture of the wound (typically Gustilo–Anderson grades I and II) (19). If wound closure requires a local or free flap and the fracture has little bone loss or contamination, internal fixation carries low rates of infection as long as definitive soft tissue closure using well-vascularised tissue is achieved at the same time. Such situations occur when both orthopaedic and plastic surgeons decide that definitive skeletal stabilisation and cover can be accomplished then and there and safely. In that scenario, the entire operative procedure is carried out as a formal second intervention; this would involve new instruments, a re-prep and re-drape of the limb, and the surgical team changing into fresh attire. Whilst direct evidence to support this two-procedure single-stage event is absent, open injuries that are excised (debrided) and lavaged of gross or even microscopic contaminants will render all instruments and drapes used unsterile without exception.
In contrast, if provisional external fixation is used and wound closure delayed, conversion to internal fixation should proceed cautiously. The risks associated with conversion from provisional spanning external fixation to internal fixation have not been quantified. Recommendations that intervals of 4–28 days are ‘safe’ are quoted but intramedullary canal contamination from pin sites is an early phenomenon and infection from one pin site tracking along the canal to reach the remainder of the cavity does occur (20, 21, 22, 23). If conversion from external to internal fixation is planned, we recommended that this be achieved within 72 hours of the primary wound excision (debridement) (this implies that it is performed usually at the second-look procedure) and that definitive soft tissue cover is achieved at the same time. If this window of opportunity for conversion is missed, consideration should be given to definitive management with modern multiplanar or circular external fixators.
Degree and location of soft tissue and bone loss
Current techniques for dealing with bone loss include the creation of new bone by distraction osteogenesis (the Ilizarov method) or autogenous bone grafting following use of a cement spacer in the defect (the Masquelet method) (24, 25, 26). The former technique is well established and reliable; if the fracture characteristics are such that this method is to be employed in reconstruction of the limb, circular external fixation or a rail-type external fixator will be a better choice for definitive stabilisation. Smaller losses of bone—usually cuneiform in shape rather than segmental defects—can be treated by a planned autogenous bone grafting later; here internal or external fixation can be the definitive stabilisation depending on the level of the fracture and contamination at injury.
Dead space and management
In severe open injuries, tissue loss occurs either primarily (direct consequence of the injury where fragments or segments of bone are extruded and left at the scene of trauma) or secondarily after wound excision (debridement). In both, there is a resulting defect that becomes filled with haematoma. This haematoma-filled space can be prevented through the use of negative pressure wound dressings, antibiotic-impregnated cement spacers and, in some instances, performing an acute shortening of the limb with the intention of restoring length at a later stage. Acute shortening, if used for dead space management, may influence the choice of stabilisation device as it is more common for a circular or rail-type fixator to be used in this scenario as it then can be utilised for the subsequent limb lengthening (27).
Dead space is often thought of as a cavity but any structure unable to provide some resistance to bacterial proliferation within or on itself—non-viable tissue, haematoma, internal fixation devices—behaves as dead space. For these reasons, meticulous wound excision (debridement), pervention of cavities, avoidance of internal fixation in highly contaminated injuries, and early definitive soft tissue cover remain guiding principles for treating open fractures of the tibia.
Stable spanning external fixation is applied at the time of primary wound excision (debridement) if definitive fracture fixation is not performed. The choice of components and the fixator configuration should resist displacing forces at the fracture site during patient transfer or with patient movement. The applied fixator should enable the proposed soft tissue reconstruction to be carried out without impediment.
If definitive soft tissue cover can be provided at primary wound excision (debridement) and wound contamination is minimal, internal fixation is a suitable choice for definitive stabilisation. If soft tissue cover is delayed, there is significant contamination, or for complex fracture patterns with bone loss, modern multiplanar or circular fixators are more appropriate. In a combined orthoplastic approach, bone and soft tissue reconstruction strategies are planned together; decisions are made that enable both to be carried out with each facilitating the other.
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