Flail Chest / Chest Wall Trauma (Orthopaedic Relevance)

Definition. Flail chest is three or more contiguous ribs each fractured in two or more places. The fractures isolate a free segment of chest wall that moves paradoxically, drawn in on inspiration and pushed out on expiration. It is a high-energy injury.

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What drives the morbidity. The paradox is the visible sign, but the morbidity is driven mainly by the underlying pulmonary contusion and by pain-related hypoventilation, which leads to atelectasis, retained secretions, pneumonia and respiratory failure, not by the paradox alone. The classic error is to focus on the dramatic chest-wall motion and under-treat the lung and the pain. The priorities are oxygenation, analgesia and pulmonary care, not merely splinting the segment.

The rib cage is a series of levers, and the pattern of fractures is a readable record of the energy and its direction. The fracture level, not just the count, changes what you go looking for.

• Ribs 1 and 2 are short, thick and protected beneath the clavicle and scapula. Fracturing them takes very high energy, so they are a red flag for injury to the great vessels (subclavian and aortic), the brachial plexus, and the head, neck and spine. A first-rib fracture on a trauma film should prompt vascular assessment rather than reassurance.
• Ribs 3 to 10 are the ones that flail. They are the mobile, spring-loaded ribs, and the usual flail segment lies anterolaterally or laterally, where the ribs are longest and least supported.
• Ribs 9 to 12 are short, mobile and overlie the upper abdomen. Fractures here should raise liver, splenic and renal injury: a left lower rib fracture is a splenic injury until imaging says otherwise.
• The costal cartilages are radiolucent, so costochondral separations and cartilage injuries are invisible on plain film. They are a recognised cause of an "occult" flail chest that is obvious clinically but unexplained radiographically, and CT with 3D reconstruction resolves this.

The neurovascular bundle. It runs in the costal groove under the inferior border of each rib, in the order vein-artery-nerve from above down. Two examinable consequences follow. An intercostal block or a chest drain is placed over the superior border of the rib below to avoid the bundle, and during rib fixation the plate and screws are positioned with the bundle in mind, since an errant drill causes bleeding that is awkward to control and an intercostal neuralgia that is permanent.

What a contusion is. The morbidity of a flail chest comes from the pulmonary contusion, a bruise of the lung parenchyma beneath the fractured segment. The impact ruptures alveolar capillaries, the alveoli fill with blood and oedema fluid, and surfactant is disrupted. The flooded, collapsed alveoli are still perfused but no longer ventilated, producing ventilation-perfusion mismatch and shunt, and therefore hypoxaemia out of proportion to the visible chest-wall injury.

It blossoms. The contusion is frequently under-called on the initial chest radiograph and characteristically worsens, radiographically and physiologically, over the first 24 to 72 hours before slowly resolving over days to weeks. CT is far more sensitive than plain film and shows the true extent early, and a large contused lung volume predicts ARDS and the need for ventilation.

Why patients deteriorate late. This delayed blossoming is why a flail-chest patient can look stable on arrival and then deteriorate at 24 to 48 hours. Serial respiratory assessment, a low threshold for CT and early escalation of support are what catch it.

The fluid paradox. The contused lung is leaky, so over-resuscitation with crystalloid worsens the oedema and the contusion, yet the polytrauma patient may genuinely need volume for haemorrhage. The aim is judicious, goal-directed fluid management: restore euvolaemia and treat shock but avoid fluid overload, with lung-protective ventilation if the patient is ventilated. The overall resuscitation and damage-control framework belongs to Polytrauma Management and Damage Control Orthopaedics.

Management follows ATLS principles, because this is a chest injury in a trauma patient. Before attention turns to the flail segment or SSRF, the primary survey must exclude the immediately life-threatening thoracic injuries, which high-energy rib fractures frequently cause.

• Tension pneumothorax. Air trapped under pressure with mediastinal shift: respiratory distress, hypotension, distended neck veins, tracheal deviation away from the side, and absent breath sounds with hyperresonance. It is a clinical diagnosis treated immediately by needle or finger decompression and then a chest drain; do not wait for a radiograph.
• Open pneumothorax. A "sucking" chest-wall wound. Cover it with a dressing taped on three sides (a flutter valve), then place a chest drain away from the wound.
• Massive haemothorax. Large blood loss into the hemithorax, with absent breath sounds, dullness and shock. Treat with a chest drain plus blood and volume, and thoracotomy for a large immediate or ongoing output.
• Cardiac tamponade. Beck's triad (hypotension, muffled heart sounds, raised JVP), diagnosed on FAST; it needs pericardial drainage or surgery.

When a flail chest deteriorates. Flail chest is itself one of the breathing problems of the primary survey. If the patient deteriorates, exclude a (tension) pneumothorax or haemothorax first, and remember that starting positive-pressure ventilation can convert a simple pneumothorax into a tension pneumothorax.

The single most examinable statistic in chest-wall trauma is not about flail chest at all. It is about how badly older patients tolerate any rib fracture.

The numbers. In the classic cohort, patients aged 65 and over with rib fractures had roughly twice the mortality and thoracic morbidity of younger patients with comparable injuries, 22% versus 10% mortality and 31% versus 17% pneumonia, despite similar fracture numbers and injury severity scores. The risk scales with the count: each additional rib fracture increases mortality by about 19% and the risk of pneumonia by about 27%.

What it changes. An older patient with two or three rib fractures is not a minor injury to be discharged from the emergency department with codeine; that is the trap. Lower the threshold for admission, monitoring and aggressive analgesia in this group, and consider high-dependency care where the fracture count is high or the reserve poor. Count the fractures deliberately on CT and use the number as a risk score, not just a description.

Pathways. Institutional rib fracture pathways, with protocolised analgesia, incentive spirometry, early physiotherapy and escalation criteria, exist precisely because this population deteriorates quietly at 48 to 72 hours.

The foundation. Analgesia and pulmonary care come first, and always. Management centres on multimodal analgesia, including regional techniques, so that the patient can breathe deeply and cough, together with aggressive pulmonary toilet and chest physiotherapy, supplemental oxygen, and escalation to non-invasive or invasive ventilation when respiratory failure develops.

Choosing the regional technique. Naming the options is not an answer. The examiner wants to know which one and why, and what stops you.

Thoracic epidural. The historic reference standard for multiple rib fractures and flail chest, giving bilateral segmental block and the best-documented improvement in pulmonary function. Its problem in this population is that it is frequently unavailable in practice. It is contraindicated or unwise with each of the following, all common in exactly the polytrauma patient who has a flail chest:

• Coagulopathy or therapeutic anticoagulation
• Haemodynamic instability, since the sympathectomy will not be tolerated in a patient who is still bleeding
• Spinal fracture or spinal cord injury
• Sepsis

Paravertebral block. Comparable unilateral analgesia with less hypotension and urinary retention, and more tolerant of anticoagulation. That makes it a practical alternative when the epidural is contraindicated and the injury is one-sided.

Erector spinae and serratus anterior plane blocks. Superficial fascial-plane techniques that are far from the neuraxis, quick, ultrasound-guided and comparatively safe in the anticoagulated patient. For this reason they have largely displaced the older options in many units, and they can be run as catheters.

Intercostal blocks. Simple but short-lived and multiple-injection, with the highest local anaesthetic absorption of the options, so they are best as a bridge.

Systemic multimodal therapy. This underpins everything: regular paracetamol, NSAIDs where renal function and bleeding risk permit, and opioid by patient-controlled analgesia, with ketamine as an opioid-sparing adjunct. The goal is the ability to take a deep breath, cough and be sat out, so titrate analgesia against incentive spirometry and the ability to clear secretions, not a pain score alone.

What SSRF offers. Surgical stabilisation of rib fractures (SSRF), or rib plating, is increasingly used and improves outcomes: lower mortality, fewer pulmonary complications and more ventilator-free days. It is used for flail chest, where the benefit is greatest, and for selected patients with multiple displaced rib fractures, particularly those ventilated or with more than three fractures.

Length of stay and resources. Here the evidence divides. The Tanaka trial found a shorter ICU stay after fixation, whereas the largest nationwide analysis (Kwon) found longer hospital and ICU stays and more resource use, which belongs in the consent conversation.

Timing. Early SSRF, within about 3 days (~82 hours), is associated with lower rates of ARDS and ventilator-associated pneumonia and shorter hospital stays than delayed fixation.

The orthopaedic role. The orthopaedic or trauma surgeon may perform or assist with rib fixation. They must also recognise and manage the associated skeletal injuries (scapula, clavicle, sternum, spine) and the intrathoracic and abdominal injuries that accompany this high-energy mechanism, and integrate chest-wall stabilisation into the overall polytrauma plan, including the timing of other orthopaedic procedures.

Planning and approach. Positioning and approach follow the fracture location, guided by the CT with 3D reconstruction. Posterolateral fractures are approached laterally or posterolaterally with the patient in the lateral position, and anterior fractures anteriorly. Muscle-sparing approaches and windows between latissimus dorsi and serratus anterior limit morbidity.

Which ribs to fix. You do not fix every fracture. The aim is to restore the stability and contour of the chest wall, which usually means fixing the ends of the flail segment and the most displaced ribs, commonly ribs 4 to 9: the first two are inaccessible beneath the scapula and clavicle, and the floating ribs contribute little to stability.

Implants. Anatomically pre-contoured locking plates are applied to the outer cortex, or intramedullary splints or rods are used for selected fractures where soft-tissue stripping is undesirable. Ribs are thin, so locking screws and adequate screw purchase matter.

Thoracoscopy and the pleura. VATS is often used alongside to evacuate a retained haemothorax, confirm the reduction from inside, and assess for lung injury or a diaphragmatic tear. A chest drain is usually placed and the pleura inspected, because an unrecognised pleural breach with positive-pressure ventilation is the immediate hazard.

Complications. These are the counterbalance to the outcome benefits and belong in the consent discussion:

• Implant failure or migration
• Symptomatic hardware requiring removal
• Surgical site infection and empyema
• Pleural injury and pneumothorax
• Intercostal neuralgia
• Nonunion

The acute phase dominates the teaching, but flail chest is not an injury people simply recover from, and the long-term picture is a fair viva question.

In hospital. The complications follow directly from the physiology. Pneumonia is the commonest, along with atelectasis and retained secretions, ARDS where the contusion is large, prolonged ventilation and its consequences including tracheostomy, retained haemothorax and empyema, and pneumothorax, which can appear late.

Afterwards. Three things are consistently under-appreciated:

• Chronic chest wall pain is common and can persist for a year or more, sometimes as a neuropathic intercostal neuralgia rather than as fracture pain, and it responds poorly to opioids.
• Persistent disability and delayed return to work are the rule rather than the exception after a flail chest, with reduced exercise tolerance and measurable restrictive impairment on lung function testing in a substantial minority.
• Symptomatic nonunion and chest wall deformity occur, and are one of the accepted later indications for rib fixation in a patient who was managed non-operatively at the time.

Follow-up. Because of this, follow-up should be active rather than assumed. Review pain and function, screen for the neuropathic component, and involve pain services and rehabilitation early rather than treating a healed radiograph as the end of the episode.