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Operative treatment of chest wall injury
Thoracic injury is a significant cause of morbidity and death. Rib fractures, one of the most common manifestations of thoracic injury, are frequently encountered in victims of trauma. For example, 94% of severely or fatally injured seatbelt wearers have rib fractures. Approximately 25% of all deaths due to trauma result from injury to the thorax. Despite this, most thoracic injuries are treated with simple interventions such as supplemental oxygen, mechanical ventilation, tube thoracostomy, and analgesia. The vast majority of thoracic injuries do not require major operative procedures. The basic pathophysiology of thoracic injury involves hypoxia, hypercarbia, and both metabolic and respiratory acidosis. Flail chest is associated with all of these pathophysiologic states.
Approximately 10% of all patients admitted to trauma centers have rib fractures. Most of these patients require only analgesia, pulmonary toilet, and symptomatic care. Approximately 10% of patients admitted with rib fractures have a flail chest. Flail chest results from significant kinetic energy transmitted to the thorax. The classic definition of flail chest is the fracture of three or more consecutive ribs in at least two locations. With the improvement in computed tomography (CT) imaging, flail chest is more easily identified. However, when discussing flail chest, it is important to distinguish between radiographic findings of flail chest and clinical findings of flail chest, in which the former may or may not exhibit clinical features of flail chest. Patients with multiple consecutive rib fractures may exhibit the same respiratory compromise and pulmonary dysfunction classically associated with flail chest. Mechanical ventilation may be required in more than 50% of patients with flail chest even when optimal support, analgesia, and pulmonary toilet are provided. A key component in the successful treatment of flail chest is adequate analgesia. Failure to provide adequate analgesia in nonventilated patient results in severe pain, which produces hypoventilation, retention of secretions, progressive atelectasis, lobar collapse, pneumonia, and respiratory failure. The most effective method of providing analgesia for patients with flail chest is thoracic epidural analgesia. This intervention should be initiated as soon as possible to prevent progressive pulmonary insufficiency. All too often, this therapy is delayed past the initial 24 hours following injury, leading to increased morbidity. Alternatively, intercostal nerve blocks may be used if long-acting local anesthetics are available. The percutaneous placement of long catheters that permit the continuous installation of local anesthetic adjacent to the site of rib fractures and intercostal nerves may be useful, but the benefits of this technique are less well documented. External patches or dressings containing long-acting local anesthetic agents do not appear to be useful in patients with rib fractures and flail chest. The mortality rate for patients with flail chest is high, ranging from 10% to 40%. This high mortality rate is primarily due to associated injuries.
Indications for operative therapy
Indications for operative stabilization of rib fractures have evolved and increased over the last decade. Historically, many patients with rib fractures were not considered candidates for operative fixation. However, increasing experience suggests that previous contraindications for rib fixation may be less pertinent with newer operative techniques and improved technologies. Indications for operative fixation, which are discussed elsewhere, can be broadly broken up into two broad categories: anatomical considerations and physiologic considerations.
Flail chest is now considered the most common and well-supported indication for operative intervention. In a recent meta-analysis, including nearly 6000 patients with flail chest, Houwert et al showed significant reductions in hospital length of stay, intensive care unit (ICU) length of stay, duration of mechanical ventilation, decrease rates of pneumonia, and decreased need for tracheostomy. In a similar analysis comparing surgical fixation to nonsurgical management of rib fractures, Liu et al reviewed 14 papers including almost 900 patients. They found comparable decreases in hospital length of stay, ICU length of stay, duration of mechanical ventilation, and mortality. Given the results of these and other studies, the Eastern Association for the Surgery of Trauma practice management guideline currently suggests that patients with flail chest who are deemed appropriate surgical candidates should be operatively managed as early as possible, after potentially life-threatening injuries have been addressed.
Another anatomical consideration is chest wall deformity. This typically occurs in the setting of significant overlap of adjoining fracture segments, resulting in the loss of intrathoracic volume. Severely displaced rib fractures also have the potential to cause pulmonary lacerations, intercostal artery hemorrhage, and intercostal nerve entrapment, among other complications. Significant chest wall deformity subsequently leads to poor chest wall compliance, decreased lung expansion and secretion clearance, and pulmonary compromise. Chronic pain associated with rib fractures is frequently encountered with overlapping fractures.
Physiologic considerations include evaluation of pulmonary mechanics and assessment of mechanical ventilator needs. Scoring systems based on initial radiographic imaging of the thorax have been shown to be predictive of patients more likely to have subsequent respiratory failure. Severely displaced fractures and flail chest both lead to decreased chest wall compliance and ultimately lead to impaired ventilation. In order to identify those patients with poor mechanics, pulmonary function tests have traditionally been the gold standard. However, this method is not feasible in the acute setting. Many surgeons rely on incentive spirometry as a gauge of pulmonary physiology. In general, those patients unable to achieve 50% of predicted volumes during incentive spirometry with adequate analgesia are considered to have threatened pulmonary reserves and should be considered for operative fixation. Although there is currently no consensus when operative fixation is indicated to facilitate liberation from mechanical ventilation, Doben et al were able to achieve liberation with a median of 1.5 days after surgical fixation.
The majority of patients with flail chest are not operative candidates. In most cases, underlying pulmonary contusion is the primary cause of hypoxia and the reason that these patients require mechanical ventilation. Patients with significant hypoxia due to pulmonary contusion should not undergo elective operations. Operative fixation may be timed before or after hypoxia from pulmonary contusion is a significant issue. In some patients, the biomechanical effects of multiple rib fractures and flail chest prevent adequate ventilation. This inadequate ventilation can produce respiratory failure independent of underlying pulmonary contusion. Many surgeons complete rib fixation as soon as patients are stable, preferably within 72 hours of injury.
The indications for surgical stabilization of rib fractures and flail chest continue to evolve. Indications are different for patients with acute respiratory failure as compared to patients with nonunion of rib fractures producing chronic pain and disability. In the acute setting, potential indications for operative fixation of severely displaced rib fractures and flail chest include patients who must undergo thoracotomy for associated intrathoracic injuries. Hemodynamically stable patients who require thoracotomy may be considered for simultaneous repair of rib fractures. Another group of candidates for operative fixation are patients who do not initially require intubation and mechanical ventilation but have progressive deterioration of pulmonary function despite aggressive nonoperative treatment that includes adequate analgesia, aggressive pulmonary toilet, and the subsequent requirement for mechanical ventilation. Other patients who initially require ventilatory support for pulmonary contusion may become candidates for operative fixation if they remain ventilator dependent after pulmonary contusion has resolved. Patients with extensive, displaced rib fractures or anterolateral flail chest with progressive dislocation of the fractured ribs are also candidates for operative fixation. Operative fixation in this group of patients can prevent unacceptable chest wall deformity and, more importantly, prevent chronic pain by eliminating the development of pseudoarthroses. In these patients, intercostal neuralgia may play a significant role in chronic pain. The use of gabapentin should be considered as a standard component of therapy for chronic pain associated with displaced rib fractures and pseudoarthroses. An algorithm to determine the applicability of operative treatment of acute chest wall injury is represented in Figure 1 .
Anatomy, positioning, and incisions
The exposure of rib fractures for operative fixation requires knowledge of chest wall anatomy. Major muscle groups of the chest include the trapezius, the rhomboids, the pectoralis major and minor, the latissimus dorsi, the serratus anterior, and the erector spinae muscles. Approaches that are useful for exposure of rib fractures include the standard thoracotomy incisions: anterolateral, axillary, and posterolateral. The posterolateral incision with the patient in lateral decubitus position provides the widest exposure and remains the most frequently used incision. However, as techniques have improved, newer minimally invasive, muscle-sparing incisions are now more widely utilized. These include subscapular, inframammary, and posterior vertical approaches in which muscle “splitting” is performed to avoid muscle transection. An important anatomic landmark is the triangle of auscultation. The triangle of auscultation is located at the inferior angle of the scapula. It is bordered on three sides—inferiorly by the latissimus dorsi muscle, superiorly by the inferior border of the trapezius, and laterally by the medial border of the scapula formed by the teres major muscle and infraspinatus muscle. The floor of the triangle consists of the posterior thoracic wall, which contains the rhomboid major muscle, serratus anterior muscle, and erector spinae muscles. Exploitation of this triangle allows access to posterior, lateral, and subscapular fractures while minimizing muscle trauma. In general, fractures of the first, second, and tenth through twelfth ribs do not need to be repaired as they provide little contribution to overall chest wall mechanics. However, if access to anterior fractures of the first through third ribs should be needed, a small horizontal incision with splitting of the pectoralis fibers provides adequate exposure. Similarly, access to the tenth through twelfth ribs may also be achieved via incision directly over top of the underlying rib space.
Proper positioning is of critical importance when performing surgical stabilization. Helical CT scan of the chest with three-dimensional reformatting provides extremely useful information for determining optimal positioning. In general, three standard positions are utilized: supine, lateral decubitus, and prone. Supine positioning is ideal for anterior fractures. In this position, patients are placed flat on their back with the ipsilateral arm with 90 degrees of abduction. If access to more lateral fractures is required, a bump placed under the patient can facilitate more lateral exposure. Perhaps the most versatile position is the lateral decubitus position. This position allows exposure of most anterior, lateral, and posterior fractures and is particularly useful when a combination of these fracture patterns exists (anterior and posterior fractures, etc.). To achieve lateral decubitus positioning, the patient is placed on a beanbag and rolled laterally. Appropriate padding should be placed under all pressure points. An axillary roll is placed. The knees are placed in gentle flexion with adequate padding. If entry into the thorax is necessary, the bed should be flexed in a jackknife position to extend the intercostal space. The prone position is well suited for posterior and posterolateral fractures. The patient is placed facedown on a well-padded operating table. The ipsilateral arm is allowed to hang down off the table and supported with an arm support. This allows for superior and lateral rotation of the scapula, facilitating access to subscapular fractures.
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