Simple rib fractures are the most common injury sustained following blunt chest trauma, accounting for more than half of thoracic injuries from nonpenetrating trauma. Approximately 10% of all patients admitted after blunt chest trauma have one or more rib fractures. These fractures are rarely life-threatening in themselves but can be an external marker of more severe visceral injury inside the abdomen and the chest.
The image below depicts aortic injury, closely associated with a widening of greater than 8 cm measured at the widest points of the mediastinum.
The most common mechanism of injury for rib fractures in elderly persons is a fall from height or from standing. In adults, motor vehicle accident (MVA) is the most common mechanism. Youths sustain rib fractures most often secondary to recreational and athletic activities, as well as by nonaccidental trauma.
Rib fractures may also be pathologic. Cancers that metastasize to bone (eg, prostate, breast, renal) frequently become apparent in a rib. Ribs are relatively thin compared with major long bones and are more likely to fracture when invaded by a metastatic lesion.
In a study of Japanese patients with rheumatoid arthritis who were followed over a mean duration of 5.2 years, 13.5% reported incident fractures, with rib fractures being the most common fractures in men and vertebral fractures being the most common fractures in women, followed by rib fractures. 
The chest wall protects underlying sensitive structures by surrounding internal organs with hard osseous structures including the ribs, clavicles, sternum, and scapulae. An intact chest wall is necessary for normal respiration.
Rib fractures may compromise ventilation by a variety of mechanisms. Pain from rib fractures can cause respiratory splinting, resulting in atelectasis and pneumonia. Multiple contiguous rib fractures (ie, flail chest) interfere with normal costovertebral and diaphragmatic muscle excursion, potentially causing ventilatory insufficiency. Fragments of fractured ribs can also act as penetrating objects leading to the formation of a hemothorax or a pneumothorax. Ribs commonly fracture at the point of impact or at the posterior angle (structurally their weakest area). Ribs four through nine (4-9) are the most commonly injured.
The thinnest and weakest portion of the first rib is at the groove for the subclavian artery.  The mechanism of first-rib injury in motor vehicle accidents seems to be a violent contraction of the scalene muscles brought on by the sudden forward movement of the head and neck. 
A single blow may cause rib fractures in multiple places. Traumatic fractures most often occur at the site of impact or the posterolateral bend, where the rib is weakest.
Due to the greater pliability of children's ribs, greater force is required to produce a fracture.
The incidence of rib fractures is dramatically underreported. More than 2 million blunt mechanisms of injury occur annually just as motor vehicle collisions, with reported incidence of chest injury between 67 and 70% of those.  The prevalence of rib fractures is linked to the prevalence of the underlying cause of the trauma. Rib fractures are more common in countries with higher incidence of MVAs.
Because children have more elastic ribs, they are less likely than adults to sustain fractures following blunt chest trauma. Elderly individuals are more likely to have associated injuries and complications. Children present more frequently with trauma to the underlying chest and abdominal organs without the associated rib fractures commonly seen in adults. Classically, this made rib fractures in children an ominous sign of potential high-force injury. Bruising near the fracture site is uncommon with pediatric rib fractures, seen in only 9.1% of pediatric rib fractures in one study.  Consider child abuse in children who lack a significant mechanism for multiple rib fractures or have fractures in different stages of healing. Children younger than 2 years with rib fractures have a prevalence of child abuse as high as 83%.
Older persons are more prone to rib fractures than younger adults  and, therefore, the pulmonary sequelae such as atelectasis, pneumonia, and respiratory arrest. The presence of cardiopulmonary disease also significantly increases morbidity and mortality rates in patients older than 65 years. The clinical benefits of a rib scoring system has been tested at one site for hospitalized older adults. 
Rib fractures are not usually dangerous in and of themselves. Patients may develop pneumonia from splinting. Morbidity correlates with the degree of injury to underlying structures.
In one study of patients with rib fractures, the mortality rate reached 12%; of these, 94% had associated injuries and 32% had a hemothorax or a pneumothorax.  More than half of all patients required either operative or ICU management. Average blood loss per fractured rib is reportedly 100-150 mL.
In one retrospective study of 99 elderly patients, 16% of patients (95% confidence interval [CI], 9.5-24.9%) developed adverse events, including 2 deaths.  Adverse events were defined as acute respiratory distress syndrome (ARDS), pneumonia, unanticipated intubation, transfer to ICU for hypoxemia, or death. Risk factors associated with these adverse events were age ≥85 years, initial systolic blood pressure < 90 mm Hg, hemothorax, pneumothorax, 3 or more unilateral rib fractures, or pulmonary contusion. These risk factors predicted adverse events with 100% sensitivity (95% CI, 79.4-100%), and 38.6% specificity (95% CI, 28.1-49.9%), and they may identify variables that might aid in identifying patients at high risk for serious adverse events if validated in a larger prospective study.
A study of rib fractures in patients younger than 21 years found that mortality increased nearly linearly for increasing numbers of pediatric rib fractures. Odds of mortality increased with each additional rib fractured in all pediatric age groups. Mortality doubled from 1.79% without rib fracture to 5.81% for 1 rib fracture and then nearly linearly increased to 8.23% for 7 fractures. Ventilator days also increased with increasing number of rib fractures. 
Position of the fractured rib in the thorax helps identify potential injury to specific underlying organs. Fracture of the lower ribs usually is associated with injury to abdominal organs rather than to lung parenchyma. Fracture of the left lower ribs is associated with splenic injuries, and fracture of the right lower ribs is associated with liver injuries. Fracture of the floating ribs (ribs 11, 12) is often associated with renal injuries.
First rib fractures have often been described as having a high association with serious or lethal spinal or vascular injuries.  They are rarest of all rib fractures  and were once thought to be a harbinger of severe trauma,  since the first rib is very well protected by the shoulder, lower neck musculature, and clavicle.
First rib fractures were thought to require a much higher impact force to fracture than other ribs, but that theory is now in question. Until further studies are done, fractures of the first rib should raise suspicion of significant chest trauma. The presence of a first rib injury requires a multidisciplinary approach. CT of the spine and chest allows for an early diagnosis. Appropriate treatment and observation in the intensive care unit may prevent further morbidity and/or mortality. 
While first rib fractures have a high association with spinal fractures and are associated with multisystem injuries, the occurrence of first rib fractures is not always associated with increased morbidity and mortality.  Mortality rates as high as 36% have been previously reported with fractures of the first rib, which are associated ith injury to the lung, ascending aorta, subclavian artery, and brachial plexus. Other complications associated with first rib fractures include delayed subclavian vessel thrombosis, aortic aneurysm, tracheobronchial fistula, thoracic outlet syndrome,  and Horner's syndrome. 
The association of lower rib fractures with pelvic fractures has been associated with a higher incidence of solid organ injury. 
Isolated rib fractures in younger patients have a good prognosis. Older patients have a higher incidence of significant pulmonary complications. In one study, 16% of patients 65 years and older with isolated blunt chest trauma had some delayed adverse event, defined as pneumonia, ARDS, unanticipated intubation, need to transfer patient to ICU for hypoxemia, and death from pulmonary sequelae. 
Return to work or sport depends on the activity involved and the level of pain. Heavy labor and intensive training for athletes with stress fractures are not recommended for the first 3 weeks. When pain is not present at rest, the patient can begin to increase his or her activity level but this should be gradually done. Most rib fractures heal within 6 weeks. Many patients are able to resume daily activities much sooner. 
Virtually all nonpathologic rib fractures heal well with conservative management. Some patients are able to return to work within a few days, depending on their occupation. 
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