Aetiology

Falls from a standing height account for a significant majority of hip fractures in older people.[12][13]​ This is associated with the osteopenic or osteoporotic condition of bone.[20][21][22]​ See Osteoporosis. Studies suggest an increased risk of hip fracture among patients with dementia.[22]​ In one population-based study, patients with dementia with coexistent osteoporosis were at increased risk of hip fracture compared with patients with dementia alone.[23]​

In younger people, the primary aetiology is high-energy trauma including motor vehicle accidents and falls from a height.[17]

Pathophysiology

Fracture pathophysiology includes cortical disruption, periosteal damage, and damage to the intramedullary and cancellous architecture. Histomorphometric studies have shown that cortical thinning and some decrease in trabecular bone mass and connectivity can be seen especially in osteoporosis suggesting a lower quality of bone, and therefore decreased mechanical strength resulting in fracture.[24] An age-related decline in osteocyte viability has also been observed in experimental studies.[25] An inflammatory response also occurs following fractures of the proximal femur.[26]

Classification

Classify fractures radiographically into intracapsular and extracapsular to guide surgical management.

  • Intracapsular fractures

    • The retinacular vessels that pass up the femoral capsule may be damaged, especially if the fracture is displaced, resulting in poor blood supply to the femoral head often leading to avascular necrosis.[1] 

  • Extracapsular fractures

    • Include trochanteric or subtrochanteric, which typically heal well.[2]​​

  • Fractures may be further subdivided, depending on the level of the fracture and the presence or absence of displacement and comminution.[1] 

The Garden classification categorises intracapsular hip fractures into four types based on anteroposterior radiographs of the hip. It incorporates displacement, fracture completeness, and relationship of bony trabeculae in the femoral head and neck.[3][4] 

Intracapsular (femoral neck) fractures can be classified as follows:[5]

  • Type 1: impacted in valgus

  • Type 2: undisplaced

  • Type 3: displaced <50% and in varus

  • Type 4: completely displaced.

Reliability studies have suggested there is poor inter- and intra-rater agreement in categorising fractures with this classification.[6] 

Extracapsular fractures are classified broadly into trochanteric and subtrochanteric types. The AO classification is useful in further guiding surgical management.[7] This categorises fractures according to location, joint involvement, fracture pattern, and geometry. 

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