1 Introduction

The first reports of the use of external fixation as treatment for pelvic fractures were published more than 100 years ago, but these devices were not used extensively until the 1930s–1940s [1–3]. Subsequently, recurring clinical problems caused external fixation to fall into disrepute in the 1950s–1960s. External fixation was the object of renewed interest, especially for pelvic disruptions, during the 1970s and early 1980s [4–12]. However, biomechanical and practical considerations have limited its usefulness while prompting the development of a treatment philosophy and methods that incorporate indications based on musculoskeletal and associated injuries, the patient′s physiological parameters, and the appropriate timing of treatment [10]. Today, external fixation is considered an essential part of the armamentarium for orthopedic surgeons in the acute resuscitation of polytraumatized patients, including unstable pelvic ring injuries, and it is the definitive treatment for specific fractures in special circumstances [13–15]. External fixation also may be used as an adjunct to internal fixation to neutralize rotational forces in the management of completely unstable pelvic ring injuries.

2 Biomechanical aspects

The stability of external fixation is related to both the osteoligamentous instability pattern of the pelvic ring and to the characteristics of the fixator itself—frame design, pin location, and size.

In their original biomechanical study on external pelvic fixation, Gunterberg et al [16] recognized the deficiency of the anterior frame and related its usefulness to the fracture pattern. They found that anterior frames did not provide sufficient stability to allow weight bearing with bilateral injuries or completely unstable unilateral injuries. Anterior frames did provide adequate stability in certain oblique unilateral fractures of the sacrum and ilium.

Mears and Fu [7, 17] studied anterior frames, acknowledged their deficiency in stabilizing unstable pelvic ring disruptions, and attempted to solve the problem with through-and-through pins connected to an anterior and posterior fixator. Stable fixation was obtained, but difficulty with providing nursing care to these patients led Mears and Fu [17] to abandon this technique. Increasing the pin size to 5 mm, adding a second set of pins anteriorly, and triangulating the bars significantly improved the stability of the anterior frame. Later work by Brown et al [18] led to the design of a biplanar external fixator with one set of pins placed superiorly through the iliac crest and a second set placed anteriorly into the ilium, starting between the anterior superior and anterior inferior iliac spines [19]. Finally, problems with achieving stability in the most difficult cases led Mears and Fu [17] to consider internal fixation in combination with external fixation. In their series, the stability of an anterior Slätis frame in combination with posterior transarticular sacroiliac joint screws was equivalent to that of an intact pelvic ring.

Brown et al [18], Shaw et al [19], and Rubash et al [20] recognized that nonanatomical fracture reduction significantly decreased the stability of fixation. They attributed the superior stability associated with anatomical reduction to the frictional and interlocking effects at the joint surfaces and fracture sites. These findings were observed with both external and internal fixation. In general, any time it is possible to compress the posterior structures, fixation is improved [21, 22].

McBroom and Tile [23] tested external skeletal fixation, internal fixation, and combinations of internal and external fixation using the pelves of human anatomical specimens. Several types of fixation were tested on partially stable pelves (simulated type B anterior posterior compression injuries) and completely unstable pelves (simulated type C vertical sheer injuries). For the partially stable simulated type B injuries, with the posterior ligamentous tension band intact, all tested external frames provided adequate stabilization for mobilization ( Fig 1.7-1 ). On the other hand, for the completely unstable simulated type C injuries none of the tested external frames provided adequate stability. Changes in pin placement, pin size, and frame design moderately improved the stability of the frames but not enough to stabilize the pelvis against physiological loads ( Fig 1.7-2 ).

Pelvic C-clamps provide more posterior stability than simple anterior fixation for certain fracture types. Pohlemann et al [24] compared one-pin supraacetabular external fixation to fixation with the Ganz et al [25] C-clamp and the Browner modification of this clamp in biomechanical models of rotationally unstable type B injuries and completely unstable type C injuries. Again, all methods provided excellent stability with the type B patterns, but the simple anterior fixation failed at low loads for unstable type C injuries. The C-clamps provided reasonable stability for pure sacroiliac dislocations, but no device withstood loads of more than 40 N in the transforaminal fracture model.

Although the pin placement in the iliac crest is easier and more convenient especially in emergencies, it appears that external fixator pins placed in the supraacetabular region provide greater stability. Egbers et al [26] tested frame assemblies and differing pin positions in a human anatomical specimen. The best stability was provided by supraacetabular pin placement.

In a similar biomechanical model Kim et al [13] found supraacetabular pin placement provided greater stability than other pin locations for both types B and C patterns. Moreover, it appears that the dense bone of the supraacetabular regions provides better fixation than the bone of the iliac crest; there are certainly more structures at risk during insertion of these pins.

The results of biomechanical studies since the 1980s on external fixation of pelvic ring fractures revealed that anterior skeletal fixation provides adequate stability in rotationally unstable (type B) injuries but cannot alone stabilize a completely unstable (type C) injury sufficiently to allow mobilization unless the external fixation is supplemented with posterior internal fixation [27]. In the laboratory, only internal fixation adequately stabilized the unstable shear fracture with sufficient strength and rigidity to safely allow early ambulation ( Fig 1.7-2 ).

Many of the relevant biomechanical studies [9, 24, 26] were designed in response to clinical and practical problems associated with the insufficiency of anterior pelvic external fixation for management of posterior and vertical instability. Efforts to overcome the anterior frame′s deficiency included supplemental internal fixation [23, 28], new patterns of pin placement, and/or new frame designs [10, 29]. These biomechanical studies yielded conflicting and confusing results, which likely resulted from variations in setup and testing from one study to another. Nevertheless, these studies provide useful biomechanical information for the clinician to consider when applying a frame [11]. However, the surgeon should realize that concurrent injuries and the necessity of timely application in a critically injured patient are often more important than the exact construction of the frame and that biomechanical studies do not necessarily translate to the clinical situation. Human anatomical specimens never completely replicate the in vivo situation. Most biomechanical studies strip the pelvis of all structures but the bones and ligaments, whereas in vivo the muscles of the pelvic floor and abdomen may provide added stability [30]. Similarly, the exact setup of the model can produce different results. All external fixators tested on type B patterns provide excellent stability ( Fig 1.7-1 ) [15, 24], whereas none provide adequate stability for type C fractures ( Fig 1.7-2 ). Moreover, what is possible in the laboratory is not always possible in the clinical situation. For example, supraacetabular pin placement provides better bone and easier access in obese patients but can be difficult in the acute situation [13, 31].

Most simple frames provide enough stability to treat type B rotationally unstable (but vertically stable) injuries of the pelvis. All external fixator frames provide only marginal stability to treat completely unstable pelvic injuries and when used alone do not ensure sufficient stability for weight bearing and ambulation. However, all anterior frames provide adequate stability to control pelvic volume for acute resuscitation. Supplementation with or replacement by open reduction and internal fixation provides superior stability but may not be clinically possible in the acute management phase.

3 Indications

Pelvic external fixation has four indications:

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  For acute management of severe pelvic disruption to control hemorrhage and provide provisional stability

  
  
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  For early management of polytrauma patients to facilitate pulmonary hygiene and appropriate nursing care and to minimize pain

  
  
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  For definitive management of specific fracture patterns to maintain reduction and enable the patient to sit upright and ambulate ( Table 1.7-1 )

  
  
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  For use as an adjunct to enhance the stability of posterior internal fixation

For acute management of severe pelvic disruption and hypotension, the application of an external fixator is based both on the patient′s initial response to treatment and on the initial AP pelvic x-ray [15, 32]. Physical examination and evaluation of the AP x-ray help to identify the presence, degree, and type of instability. Patients whose injuries demonstrate external rotational or rotational, vertical, and posterior instability are considered high risk of significant local hemorrhage related to the fracture [33] and are candidates for emergent external fixation (see Chapter 1.8). In hemodynamically unstable patients with pelvic ring fractures, expeditious external fixation of the pelvis reduces blood loss and blood transfusion requirements [34–36]. External fixation is performed before laparotomy to avoid the deterioration associated with bleeding in the unstable pelvic ring injury requiring laparotomy [30].

Because of the urgency to apply an external fixation device in acutely injured patients, the frame should be relatively simple and quickly applied. No more than one or two pins should be inserted into the dense supraacetabular bone of each hemipelvis. Application ideally should be performed under image intensification to guarantee proper, stable pin purchase and to avoid penetration of the hip joint (see section 4 in this chapter). The application of an external fixation device also should not delay subsequent laparotomy. Although placement in the anterior inferior spine is ideal, in the acute situation it may be easier to insert two pins into each crest 2–3 cm posterior to the anterior superior iliac spine.

Polytrauma patients with unstable pelvic fractures may require external fixation for damage control even when bleeding is not a problem. Definitive stabilization of a pelvic fracture can be complex, resulting in more blood loss and time in the operating room than the acutely injured patient can tolerate. Stabilization with external fixation can aid in pain management, pulmonary toilet, and general patient positioning until definitive fixation can be carried out. External fixation is also essential in stabilizing unstable pelvic ring injuries with severe concomitant peripelvic soft-tissue injury or organ damage. Internal fixation is associated with an increased risk of septic complications in these patients; therefore, external fixation might be contraindicated initially. External fixation under these circumstances is an adequate alternative for internal fixation until better soft-tissue conditions allow for definitive stabilization.

In both these indications, pin-track sepsis increases the risk of infection with definitive fixation. It is, therefore, important to consider pin placement in light of ultimate definitive fixation. If possible, it is ideal to place pins far from the planned incision. However, this is often not possible, and it is imperative to move from temporary external fixation to definitive internal fixation as soon as possible so the pin tracks have less time to colonize.

The third indication for pelvic external fixation is for definitive fixation. An anterior frame can serve as definitive fixation for a rotationally unstable, vertically stable, externally rotated pelvic (type B1) fracture, or an internally rotated pelvic (type B2) fracture. External fixation in these situations is useful when the anterior fracture pattern or the soft tissues preclude internal fixation. In some unstable type C fractures, the posterior soft tissues or patient condition preclude definitive posterior fixation. Although not ideal, in these situations, an anterior frame augmented by traction can provide definitive fixation.

For patients with pure open book (type B1, Young-Burgess APC II) fractures, internal fixation (anterior plating) may be the method of choice after reduction of the pubic symphysis, but it may be precluded by other injuries, local wound conditions, or coagulopathy. In these situations, external fixation is a viable alternative especially in symphysis disruptions that are anatomically reduced with external fixation alone. The internal rotational unstable injury (bucket-handle equivalent lateral compression injury) produces an unacceptable pelvic malunion if allowed to rotate internally. This type of instability is easily controlled by applying an external fixator on the pelvis to maintain the reduced externally rotated position.

External fixation may rarely be the only definitive treatment for type C (Young-Burgess APC III, VS, combined) fractures. In a few severely injured patients with unstable type C pelvic fractures, definitive posterior fixation may not be possible. In these situations, anterior external fixation and traction to the lower extremity on the affected side should be considered. Traction helps maintain the posterior reduction if definitive internal fixation never becomes possible, and it renders the surgery easier if definitive internal fixation is a viable option.

The fourth indication is an adjunct to posterior internal fixation, especially if the anterior injury has not been reduced. The application of a simple anterior frame greatly increases the stability of the overall construct. The additional external fixator also may be useful in the treatment of pelvic malunions and nonunions in obese patients and in patients with osteoporosis.

These four indications are based on the type of pelvic fracture, hemodynamic status of the patient, the local soft-tissue condition, and the profile of other injuries. In terms of fracture types, injuries that are rotationally unstable but vertically and posteriorly stable (type B, Young-Burgess APC I–II, LC I–III) can be managed both acutely and definitively by external fixation. Rotationally and vertically unstable injuries (type C, Young-Burgess APC III, VS, combined) are ideally definitively managed with anterior and posterior fixation. However, anterior external fixation can be used as acute stabilization for the management of bleeding and damage control. It can also be used as definitive fixation for the anterior pelvis in conjunction with internal fixation of the posterior pelvis [15].