1.8.2 Internal fixation of the injured pelvic ring: navigation
1 Patient selection and indications
Classic techniques of internal fixation have traditionally required extensive surgical exposure that can result in wound-healing problems, damage to major vessels or nerves, and high incidence of infection. Most of these complications are related to the surgical exposure itself rather than to the initial injury. It, therefore seems reasonable to consider less invasive alternatives [1–4].
In an attempt to overcome the morbidity of extensile surgical approaches, percutaneous fixation of the pelvis has received increasing attention. Routt et al [5] described percutaneous fixation with an iliosacral screw for sacroiliac dislocation and sacral fractures, demonstrating it to be a safe, reproducible method that is biomechanically stable with less blood loss and infection. Subsequently, percutaneous fixation with iliosacral screws has become increasingly common for treating complex injuries of the pelvic ring [5–7]. Apart from the percutaneous iliosacral screw, several other types of screws have been described and eventually added to the orthopedic armamentarium for the treatment of pelvic and acetabular fractures. These include antegrade and retrograde intramedullary pubic ramus screws, as well as iliac wing and transverse screws [8–11].
The indications for percutaneous pelvic surgery are controversial among orthopedic trauma surgeons. Despite this debate, the percutaneous approach to pelvic ring fractures has gained popularity and has been adopted by many pelvic surgeons due to the following rationale:
Despite the pelvis′s complex structure, a pelvic ring fracture is not an intraarticular fracture in which a perfect reduction needs to be achieved irrespective of means. The surgeon often forgoes absolute anatomical reconstruction to avoid extensive exposure, and might accept “near anatomical” reconstruction without significantly affecting the clinical outcome.
The percutaneous approach does not entirely eliminate the need for a more “open” traditional approach but rather complements it. This approach is thus used to minimize open approaches in certain areas where it can be safely implemented.
In the case of percutaneous fixation of acetabular fractures, a completely different approach should be implemented. Since the surgeon is dealing with a weight-bearing joint, anatomical reconstruction is typically required; thus, inaccuracy in reduction and/or fixation will result in a compromised outcome.
Still, the percutaneous fixation of acetabular fractures is gaining popularity despite the obvious difficulties [12–14]. In some patients, especially the elderly, it is acceptable to achieve secondary congruency while avoiding the use of extensile and unsafe exposures [15, 16]. Additionally, some of the screw pathways routinely used in percutaneous pelvic surgery can be used in acetabular fracture fixation. The learning curve achieved during pelvic surgery procedures can be applied for more demanding acetabular surgery once the surgeon has gained sufficient experience and dexterity. Last, the development of computer-assisted surgery may improve performance and increase surgeon confidence in these procedures [17, 18].
One cannot discuss the benefits and future of percutaneous pelvic and acetabular surgery without referring to the breakthroughs achieved in recent years in innovative computeraided technologies. These technologies assist the surgeon throughout all stages of treatment, ranging from preoperative planning and intraoperative imaging to the execution of final fixation. There is no doubt that these new modalities significantly increase the feasibility of percutaneous approaches to the pelvis and acetabulum. As a result, implementation of newer technological advances may allow for easier, safer, and faster procedures. This process is currently underway, and it would be interesting to investigate the experience at any of the different surgical stages [19–21].
In percutaneous surgery of pelvic and acetabular fractures, even more than in percutaneous long-bone fracture fixation, surgery should be performed according to a combination of the following three stages: (1) understanding the different components of the fracture and performing preoperative planning; (2) indirect/closed reduction techniques; and (3) percutaneous fixation.
Computer-assisted navigation surgery does not stand alone as a treatment modality but rather is one of an array of highly technological methods for the treatment of pelvic fractures. In this chapter we show how to combine sophisticated technologies at each of the stages of treatment. Each of these technologies may individually add to the success of the treatment and, when combined, may prove to be considerably more helpful.
2 Preoperative assessment
2.1 General prerequisites
To ensure the percutaneous pelvic fixation by means of computed-assisted navigation is performed safely, the following criteria must be met:
The surgeon must understand the 3-D anatomy of the pelvis of the specific patient and of the specific fracture.
Based on x-rays and computed tomographic (CT) scan, the surgeon must study the safe zones for screw insertion and ascertain that the specific patient anatomy allows for the execution of percutaneous fixation.
Prior to surgery the surgeon must ensure via high-quality image intensification that there is no visual obstruction that might interfere with the comprehension of the bony anatomy and pathology. This prerequisite is mandatory in every percutaneous surgery. This is even more critical in computer-assisted navigated surgery. Images acquired for computer-assisted navigated surgery should be of high resolution and quality, sufficient to serve as the basis for intraoperative planning and execution.
The surgeon must have all required instrumentation for carrying out a percutaneous surgery of the pelvis, in particular long screws and cannulated screws.
The surgeon must have the ability to reduce the fracture, either closed or open. This requires a radiolucent table—an option for skeletal traction and the availability of different external fixators and reduction tools.
The surgeon must have the ability to perform open surgery, if needed. In open surgeries the navigation system has the advantage of absolute precision with low radiation emissions.
Operating room setup should take into account the positioning of the different navigation system components in such a way that tracking is easily available in different positions and angles, without obstructing the optical signal. The computer screen should be in a convenient location for the surgeon to monitor and operate without compromising sterility ( Fig 1.8.2-1 ).
The entire team, and not just the surgeons, should be familiar with the specific components of the system to perform a smooth surgical procedure with minimal difficulty.
2.2 Clinical and radiological evaluation
In computer-assisted navigated percutaneous pelvic surgery, clinical evaluation must be comprehensive and thorough. A careful analysis including medical history and physical examination is essential for making the correct diagnosis and treatment plan. The patient should be undressed, and the examiner should carefully check all wounds to confirm the presence or absence of an open pelvic fracture. Wounds around the pelvic disruption are considered as having communication with the fracture, until proven otherwise. The physical examination should also include the genitalia, as the presence of bleeding from the urethra suggests an occult open pelvic fracture or a potential urethral injury. The surgeon should look carefully for signs of deformity, such as a shortened and externally rotated lower extremity and should check for stability by pushing the iliac crests and feeling for abnormal movement. Direct palpitation may reveal a large symphyseal gap or unstable rami. Both rectal and vaginal examinations are essential [22]. The x-ray evaluation follows the clinical one, and includes AP, inlet, and outlet films for the pelvis, and AP and Judet views for the acetabulum. Computed tomographic scans and more sophisticated studies are performed as necessary and when possible [23].
2.3 Preoperative planning
Although 3-D CT has considerably improved imaging, complete understanding of the fracture lines and fragments in pelvic and acetabular fractures can, at times, still be difficult. One of the most often discussed difficulties is the choice of a correct operative approach. Following fracture reduction, the plates should be accurately contoured and the screws should be precisely directed. Currently, the control of screw orientation is possible only by means of image intensification. Considering all the above, it is obvious that strict preoperative planning is mandatory in pelvic and acetabular surgery and a crucial step in percutaneous surgical treatment. It is not surprising that new technologies have been introduced to help the surgeon plan the operative procedures more precisely. Computer programs developed in recent years have enabled the performance of a virtual operation of the injured pelvis. The purpose of this preoperative stage is to virtually perform all steps of the real surgical procedure. This development may help to improve pelvic and acetabular surgery in general but could make a colossal advance in percutaneous surgery of this area. The ability to exercise a virtual surgical procedure marking the safe zones allows for precise planning of screw dimensions and pathways and enables the prechecking of the percutaneous option as an alternative to the open approach. Moreover, since the information is based on specific imaging of the fracture, it can be used intraoperatively. The highly detailed information that is acquired in the preoperative stage may be transferred to the execution stage and thus direct the navigation accordingly. Nowadays, all computerized preoperative planning software, available either experimentally or for clinical use, are based on preoperative CT scans [24, 25] ( Fig 1.8.2-2 ).
The existing methods of computed-assisted preoperative planning are:
3-D imaging allowing for the performance of the different stages of a virtual surgical procedure, including segmentation, reduction, and fixation [26] ( Fig 1.8.2-3 ).
3-D imaging in which the virtual reduction is based on a mirror image of the healthy side as a template [27] ( Fig 1.8.2-4 ).
3-D imaging allowing for the performance of finite element analysis, providing the necessary information for choosing the most preferred biomechanical composition of fixation [28] ( Fig 1.8.2-5 ).
3 Surgical technique
3.1 Anesthesia
Minimally invasive percutaneous surgery of the pelvis can be integrated into the acute trauma management phase or as a definitive treatment after the patient is hemodynamically stable. The pelvic fracture can be characterized by the patient′s hemodynamic stability and by the mechanical stability of the injury. Overall there can be different variations of these factors that determine the scenario of treatment and the type of anesthesia in particular. It should be emphasized that from the surgeon′s point of view percutaneous surgery depends on the ability to achieve reduction of the fracture, whereas reduction depends on the patient′s full relaxation.
3.2 Patient positioning
As already mentioned, in percutaneous pelvic surgery the setup of the operating room is an integral part of the preoperative planning. The use of a radiolucent table is mandatory and although there is a weight limit in using such a table, solutions must be found to accommodate obese patients. The patient′s position on the table is also preplanned in accordance with the procedure to be performed.
3.3 Reduction
Although there is controversy in the literature regarding the required accuracy of reduction of various pelvic fracture patterns, most studies have correlated the quality of the reduction of the posterior pelvic ring to patient outcome. The indications for reduction and fixation are the presence of instability and/or deformity. The surgical goal remains to achieve and to maintain an anatomical reduction, preferably but not necessarily, by using closed means. Open or closed reduction, the main technical difficulty in pelvic fracture surgery remains achieving reduction of the pelvic ring [1–3].
Precise closed reduction is a prerequisite for percutaneous pelvic fixation, and closed reduction is a demanding task in most pelvic fractures and even more so in acetabular fractures. Without special innovative technologies, only few patients with pelvic fractures can be treated by percutaneous techniques. There are three indications for percutaneous pelvic fixation:
Cases of minimally displaced pelvic or acetabular fractures
Displaced fractures with feasible closed reduction
Complex fractures in which a combination of closed and open reduction is necessary
It is clear that the invention and development of closed reduction techniques is pertinent to achieving a breakthrough in this field. Currently, there are innovative tools based on table–skeletal pelvic fixation frames, which were devised as methods for securing the normal side of the pelvis to the table and maneuvering the other hemipelvis [29, 30]. The stabilization method is designed to resist movement of the intact side of the pelvis as extrinsic reduction forces are applied. These pelvic frames have increased our ability to obtain a closed reduction of the pelvic ring ( Fig 1.8.2-6 ). Based on preliminary reports, pelvic frames are the basis for further advancement in this demanding field [30].
Related posts:
1.8.1 Internal fixation of the injured pelvic ring: rationale
1.8.3 The management of the injured pelvic ring: internal fixation of stable pelvic ring fractures (type A)
1.7 External fixation of the pelvic ring
1.8.5 Internal fixation of lateral compression fractures (type B2)
1.6 Surgical approaches to the pelvis
1.9 Sacral fractures
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