The superior tibia widens from the diaphysis proximally ( Figure 1). The proximal tibia is more readily subject to valgus force because of an anatomic predisposition with 5–7° of knee valgus in normal anatomic alignment and due to lateral side impacts being a more common injury mechanism. The same study also concluded that an intact MCL is required for an isolated lateral plateau fracture to occur because the MCL acts as the pivot point causing the lateral femoral condyle to impact the lateral tibial plateau. In a cadaver study that looked at mechanisms of injury it was found that pure valgus forces resulted in the typical lateral split fractures, axial forces resulted in joint compression fractures, and a combination of axial and valgus forces resulted in split depression fractures. In general, greater axial load results in more severe fractures with increased comminution, fragment displacement, and associated soft tissue injury. Axial load is usually a predominant component of the injury mechanism and produces higher energy at failure than angular forces. Angular, axial, and compression forces can all lead to failure of the condyles. The magnitude and direction of the force of injury many times will influence the fracture pattern. The most common mechanism of injury overall is pedestrian struck by motorized vehicles (30%) and the second most common is low energy falls (22%). The injury mechanism can involve motor vehicles, sports, and falls from height. In the younger population, high energy mechanisms predominate. A higher incidence of compression fracture patterns tends to be seen in such cases despite lower energy injury mechanisms. Bone quality influences fracture patterns with low bone density decreasing the force necessary for injury. The forces acting on the bone in conjunction with the bone quality determine the resulting fracture patterns. In the elderly, lateral fracture patterns are seen more commonly than medial. Osteopenia and osteoporosis play a large role in the fracture mechanisms and patterns observed. With an aging population and associated osteoporosis, the incidence of this injury is increasing. The majority of tibial plateau fractures in the elderly are due to low energy falls. The injury mechanism seen in tibial plateau fractures is largely age-dependent. With an increase in life expectancy as well as a large aging population in many developed countries it is expected that the incidence of low-energy tibial plateau fractures will continue to increase. There is a shift of incidence between males and females that occurs after the age of 60 with females predominating (61%). The highest incidence for tibial plateau fractures in females occurs between age 55 and 59. Comminuted fractures are more common in males. The majority of fractures occur in males (70%) with men aged 40–44 years being the most affected patient population overall. The age distribution is bimodal for both males and females which is similar to what is seen in other periarticular injuries. The combined incidence of a patient having a tibial plateau fracture with associated polytrauma on admission has been estimated at 16–40%. They have an annual incidence of 10.3 per 100,000. Fractures involving the tibial articular surface account for a little over 1% of all long bone fractures, 56.9% of all proximal tibia fractures/dislocations, and 8% of all fractures in the elderly.
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