A broken leg, or leg fracture, involves a break in one of the three bones of the leg: the femur (thigh bone), tibia (shin bone), or fibula (calf bone). While many broken legs are not life-threatening and heal with proper care, severe fractures or complications can pose a significant risk to life. Leg bones require substantial force, such as from motor vehicle accidents or falls, to fracture. The injury and associated trauma can lead to serious outcomes.
Immediate Life-Threatening Consequences
A severe leg fracture can lead to immediate life-threatening situations primarily due to significant internal bleeding and hypovolemic shock. Fractures, particularly those involving large bones like the femur or pelvis, are highly vascular and can cause substantial blood loss. For instance, a fractured femur can lead to an estimated blood loss of up to 1.5 liters, while a pelvic fracture may cause up to 1 liter of blood loss. This internal hemorrhage may not be immediately visible.
Excessive blood loss can quickly lead to hypovolemic shock, a condition where the body’s circulation is severely compromised due to fluid loss. Symptoms include a rapid heart rate, low blood pressure, and altered consciousness. If not promptly addressed with intravenous fluids and blood transfusions to restore blood volume, this compromised circulation can lead to vital organ dysfunction and failure.
Major Systemic Complications
Several systemic complications can arise days or weeks after a leg fracture. One such complication is deep vein thrombosis (DVT), where blood clots form in the deep veins. Fractures increase DVT risk due to immobilization, direct vascular damage, a heightened clotting response, and slowed blood flow in veins.
If a DVT dislodges and travels to the lungs, it becomes a pulmonary embolism (PE). PE can cause sudden shortness of breath, chest pain, and a rapid heart rate. It is the third leading cause of death within 24 hours of trauma. The incidence of DVT varies widely depending on the fracture site and preventive measures, with some studies showing a DVT incidence in femur fractures between 6.85% and 32%, and in tibial fractures between 2.09% and 16.3% even with prophylactic treatments.
Another serious risk is fat embolism syndrome (FES), which occurs when fat globules from the bone marrow enter the bloodstream after a fracture. These fat particles can block small blood vessels in the lungs, brain, or skin, leading to respiratory distress, neurological changes like confusion. FES typically develops within 12 to 72 hours post-injury. While rare, occurring in 0.5% to 2% of isolated long bone fractures, FES can be severe, with a mortality rate ranging from 5% to 20%, though this rate has been trending downwards due to improved monitoring and preventive measures.
Severe infection and sepsis, particularly with open fractures where the bone breaks through the skin, create a direct pathway for bacteria to enter the wound and bloodstream, increasing the risk of bone infection and systemic infection. If the infection spreads, it can escalate to sepsis, a life-threatening condition where the body’s immune response overreacts and attacks its own tissues and organs. Without prompt treatment, sepsis can rapidly progress to septic shock, leading to organ failure and a high mortality rate. For instance, the 30-day mortality rate for patients developing sepsis after hip fracture surgery is around 16.2%, rising to 40.8% for those who progress to septic shock.
Compartment syndrome is a condition where swelling and increased pressure within a muscle compartment compromise blood supply, leading to muscle tissue death. This muscle breakdown releases harmful substances like myoglobin into the bloodstream. Myoglobin can then overwhelm the kidneys, causing acute kidney injury (AKI) or even kidney failure, a severe complication occurring in 17% to 50% of rhabdomyolysis cases. Untreated compartment syndrome can result in death.
Severe trauma can also trigger acute respiratory distress syndrome (ARDS), a severe lung condition where fluid fills the air sacs, making breathing extremely difficult. While sometimes associated with FES, ARDS can also occur as a systemic inflammatory response to major injury. It requires mechanical ventilation and can be fatal.
Factors Influencing Severity and Outcome
The outcome of a broken leg is heavily influenced by several factors, including the nature of the fracture, the patient’s overall health, and the quality and timeliness of medical care. Fractures of the femur generally require more force and are associated with a higher likelihood of significant blood loss and systemic complications. Open fractures, where the bone pierces the skin, carry a significantly elevated risk of infection and subsequent sepsis due to direct exposure to bacteria.
A patient’s pre-existing health conditions and age also profoundly impact their ability to recover and resist complications. Older individuals, especially those over 65, and patients with chronic conditions face increased risks of adverse outcomes, including higher mortality rates. For example, patients over 65 diagnosed with fat embolism syndrome show a higher in-hospital mortality rate of 17.6% compared to younger patients. These underlying health issues can compromise the body’s immune response, circulatory function, and overall resilience to trauma.
Prompt and effective medical intervention is important in mitigating the fatal risks associated with a broken leg. Timely diagnosis, appropriate immobilization, and, if necessary, surgical repair are important steps in preventing severe complications. For instance, early surgical fixation of long bone fractures can help reduce the incidence of fat embolism syndrome. Delays in treatment have been linked to an increased risk of infection and higher mortality. Careful post-injury care, including monitoring for signs of complications and administering preventive measures like blood clot-reducing medications, is also important in improving patient outcomes.