Causes / typical injury mechanism: "Hip fractures" involve the proximal femur from the neck to the subtrochanteric region. They are caused by direct or indirect forces that overwhelm the strength of the bone.

Classic history and presentation:

• Most hip fractures occur in elderly women after falling from a standing height in the setting of underlying osteoporosis.
• A motor vehicle crash or fall from a height can cause a hip fracture in any age group.
• Femoral neck stress fractures can occur with repetitive weight-bearing, such as running.

Incidence: There are over 250 000 cases per year in the United States.

• Age – Patients are on average aged 72 years.
• Sex / gender – 75% occur in females.

Risk factors: Female sex, increasing age, Northern European ethnicity, smoking, alcohol use, prior fracture / fall history, osteoporosis, low estrogen levels, and the use of drugs that may increase the chance of falling (ie, sedatives, opioids, dopaminergic agents, anxiolytics / antidepressants).

Pathophysiology: Direct or indirect forces loading the proximal femur exceed the strength of the bone, causing the fracture. The force's direction and magnitude determine the fracture pattern.

Intracapsular fracture healing is complicated by the presence of synovial fluid, the inherent lack of periosteum, and disruption to the blood supply to the femoral head, which could lead to avascular necrosis (AVN) of the femoral head. Extracapsular fractures are less likely to damage the blood supply but can be displaced by the mechanical stress of load bearing. 

Grade / classification system: Hip fractures are classified based on their anatomical location, most commonly in the femoral neck or intertrochanteric region, and least commonly in the subtrochanteric region. These are further classified by specific fracture patterns and displacement.

Related topics: femoral neck fracture, femoral shaft fracture, hip injury, total hip arthroplasty periprosthetic fracture, traumatic hip dislocation