Etiology
Falls from a standing height account for a significant majority of hip fractures in older patients.[9][12] This is associated with the osteopenic or osteoporotic condition of bone.[19][20] A National Institutes of Health consensus conference in the US defines osteoporosis as "a skeletal disorder characterized by compromised bone strength predisposing a person to an increased risk of fracture. Bone strength reflects the integration of two main features: bone density and bone quality."[21] The World Health Organization defines osteoporosis as a bone mineral density at or below 2.5 standard deviations below normal peak values for young adults.[22] See Osteoporosis.
Osteopenia is defined as a T-score bone mineral density between -1.0 and -2.5 standard deviations below peak values for young adults.[9][22] There is an almost 3-fold increase in the risk of proximal femoral fractures for both men and women for each decrease of 1 standard deviation below peak bone mass values.[23]
Studies suggest an increased risk of hip fracture among patients with dementia.[24][25][26] In one population-based study, patients with dementia with coexistent osteoporosis were at increased risk of hip fracture compared with patients with dementia alone.[27]
In younger patients, the primary etiology is high-energy trauma including motor vehicle accidents and falls from height.[16]
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 thus decreased mechanical strength resulting in fracture.[28] An age-related decline in osteocyte viability has also been observed in experimental studies.[29] An inflammatory response also occurs following fractures of the proximal femur.[30]
Classification
General classification
Intracapsular (within the hip capsule - classically called femoral neck fractures)
Subcapital
Midcervical
Basicervical
Extracapsular (outside the hip capsule)
Intertrochanteric fractures
Subtrochanteric fractures (not classically considered hip fractures, and will not be discussed here).
Garden classification[1]
Intracapsular (femoral neck) fractures can be further classified as follows:
Type 1: Impacted in valgus
Type 2: Undisplaced
Type 3: Displaced <50% and in varus
Type 4: Completely displaced.
Reliability studies, however, have suggested that there is poor inter- and intra-rater agreement in categorizing fractures with this classification.[2] Grouping types 1 and 2 into undisplaced/minimally displaced, and type 3 and 4 into displaced, may therefore be more appropriate.
Evans classification[3]
Intertrochanteric fractures can be further classified as follows:
Undisplaced 2-part fracture
Stable 2-part fracture with the fracture line running superolateral to inferomedial
Displaced with some trochanteric comminution but intact posteromedial cortex
Three-part fracture with posteromedial cortex comminution
Four-part fracture with involvement of both trochanters.
The Orthopaedic Trauma Association and the AO Foundation classification[4]
The Orthopaedic Trauma Association/AO Foundation classification is useful for further guiding surgical management. It categorizes fractures according to location, joint involvement, fracture pattern, and geometry.
Pauwels classification[5]
This is a historical classification developed and published in the 1930s. It is based on the angle of the fracture as seen on the anteroposterior projection. This classification was developed in an attempt to predict nonunion; however, observational prognostic studies have not substantiated this.[6]
Degree 1: up to 30°
Degree 2: 30 to 50°
Degree 3: >50°.
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