What are the different classifications of bone fractures?

Comprehensive Classification of Bone Fractures

The most comprehensive classification of bone fractures includes categorization by mechanism of injury, anatomical location, fracture pattern, and stability, with specific systems developed for different skeletal regions to guide appropriate treatment decisions and predict outcomes.

Types of Fractures Based on Mechanism and Characteristics

Osteoporotic (Fragility) Fractures

• Defined as fractures associated with impaired bone strength, typically occurring with minimal trauma such as a fall from standing height 1
• Major osteoporotic fractures include clinical vertebral, hip, humerus, and forearm fractures 1
• Minor osteoporotic fractures include all other fractures except those of the face, hands, skull, feet, and ankles 1
• Fragility fractures are significant predictors of future fractures and require evaluation and treatment of underlying osteoporosis 1

Traumatic Fractures

• Caused by significant external impact force or injury exceeding a fall from standing height 1
• Distinguished from fragility fractures by the magnitude of force required to cause the fracture 1

Pathologic Fractures

• Occur secondary to altered skeletal physiology in the setting of benign or malignant lesions 1
• Examples include fractures in bone affected by malignancy, multiple myeloma, or other skeletal pathology 1
• Defined as fractures occurring without adequate trauma due to preexistent pathological bone lesions 2
• Causes include osteoporosis, osteomalacia, osteonecrosis, osteogenesis imperfecta, fibrous dysplasia, giant cell granulomas, Paget's disease, and tumors 2

Stress Fractures

• Associated with major recent increase in physical activity or repeated excessive activity with limited rest 1
• Common sites include tibia, tarsal navicular, metatarsal, fibula, femur, pelvis, and spine 1

Buckle Fractures

• Stable injuries with low risk for displacement, typically occurring when compressive forces cause axial loading along the length of the bone 3
• Most commonly seen in the distal radius of children 3
• Result from compression forces with common mechanisms including short falls (6 inches to 4 feet) 3

Classification Systems for Specific Anatomical Regions

AO/OTA Classification System for Long Bone Fractures

• Provides a unified scheme for classifying fractures of the entire skeleton 4
• Categorizes fractures into three main types with increasing severity 1:
  • Type A: Axial compression injuries 1
  • Type B: Distraction injuries of anterior and/or posterior elements 1
  • Type C: Axial torque leading to anterior and posterior element disruption with rotation 1
• The system has good to excellent inter- and intraobserver reliability at the main type level but decreases at the subtype level 4

AO Spine Thoracolumbar Injury Classification System

• Comprehensive yet simple scheme with greater reproducibility than prior systems 1
• Based on the Magerl hierarchy with ascending severity 1:
  • Type A: Compression injuries with injury of anterior elements and preservation of posterior ligamentous complex 1
  • Type B: Failure of posterior or anterior tension band in distraction 1
    • B1: Transosseous monosegmental failure of posterior tension band 1
    • B2: Bony/ligamentous failure of posterior tension band with type A vertebral body fracture 1
    • B3: Hyperextension injuries through disc space or bone (common in ankylosing spondylitis) 1
  • Type C: Disruption of all elements with displacement or dislocation 1
• Includes neurological grading component (N0-N4) and case-specific modifiers 1

Load Sharing Classification (LSC) for Burst Fractures

• Helps guide treatment of burst fractures based on three characteristics identified on CT 1:
  1. Comminution/involvement 1
  2. Apposition of fragments 1
  3. Correction of kyphotic deformity 1
• Point total determines treatment approach: 7-9 points benefit from anterior fixation, while <7 points can be treated by posterior short-segment fixation alone 1

Mandibular Fracture Classification

• Classified according to degree of comminution, location, and presence of displaced fragments 1
• Due to the U-shaped configuration of the mandible, approximately 67% of cases have two separate fractures 1
• Common patterns include 1:
  • Mandibular angle or subcondylar fracture with contralateral parasymphyseal fracture
  • Flail mandible: bilateral subcondylar fractures with symphyseal fracture

Nasal Bone Fracture Classification

• Several classification systems exist, including the Rhee system which relies on CT to determine the degree of septal deviation 1

Pediatric Long-Bone Fracture Classification

• AO comprehensive pediatric long-bone fracture classification describes localization, morphology, and severity in 3 categories 5:
  1. Simple fractures (comprising ~90% of diaphyseal, 99% of metaphyseal, and 100% of epiphyseal fractures) 5
  2. Wedge fractures 5
  3. Complex fractures 5
• Studies suggest simplifying to just two categories: simple and wedge/complex fractures 5

Destructive Fractures Classification

• Refers to fractures where osseous tissues are too severely damaged to be repaired, but soft tissues, nerves, and veins are less severely injured and can be repaired 6
• Divided into 6 types based on whether fractures communicate with the external environment and fracture sites 6:
  • a1: Closed diaphysis destructive fracture 6
  • a2: Open diaphysis destructive fracture 6
  • b1: Closed joint-involved destructive fracture 6
  • b2: Open joint-involved destructive fracture 6
  • c1: Closed mixed destructive fracture 6
  • c2: Open mixed destructive fracture 6

Classification Based on Fracture Risk and Bone Density

WHO Classification Based on T-scores

• T-score ≥ -1.0: Normal BMD 1
• T-score between -2.5 and -1.0: Osteopenia or low bone mass 1
• T-score ≤ -2.5: Osteoporosis 1

Fracture Risk Categories

• Very high fracture risk: Recent fractures, multiple fragility fractures, very low BMD (T-score below -3.0) 1
• High fracture risk: History of vertebral or hip fracture regardless of BMD, or low BMD with specific risk factors 1
• Intermediate fracture risk: BMD T-score ≤ -2.5 in lumbar spine, total hip, or femoral neck 1
• Imminent fracture risk: Highest risk in the 1-2 years following a major osteoporotic fracture 1

Vertebral Fracture Assessment and Classification

Vertebral Fracture Assessment (VFA)

• Feature of DXA scanners that obtains lateral thoracic and lumbar spine images to screen for fractures 1
• Detection of fractures allows risk restratification and potential initiation of pharmacotherapy 1
• Indications include T-scores < -1.0 and one or more of the following 1:
  1. Women age ≥70 years or men age ≥80 years 1
  2. Historical height loss >4 cm (>1.5 inches) 1
  3. Self-reported but undocumented prior vertebral fracture 1
  4. Glucocorticoid therapy equivalent to 5 mg prednisone daily for ≥3 months 1

Vertebral Fracture Classification

• Semiquantitative method based on morphometry 1
• Vertebrae characterized by shape (wedge, concave, or crush) and location of defect (anterior, posterior, and/or middle) 1
• Fracture severity graded on a scale from 1 to 3 1
• Established classification systems include Genant, McCloskey, or modified algorithm-based qualitative method 1

Clinical Implications of Fracture Classification

Impact on Treatment Decisions

• Fracture classification guides treatment decisions, helps estimate prognosis, and allows comparison of results 4
• For distal fibula fractures, immediate full weight-bearing is recommended for nondisplaced, mildly comminuted fractures 7
• Surgical management is indicated for displacement >2mm, ankle mortise instability, bi/tri-malleolar fractures, open fractures, and high-energy injuries 7

Morbidity and Mortality Considerations

• Fragility fractures are associated with significant morbidity and mortality 1
• Postfracture mortality is highest in the first year, particularly following clinical vertebral fractures or hip fractures 1
• Vertebral fractures often do not come to clinical attention but represent a major gap in identifying individuals at high fracture risk 1

Imaging Considerations

• Standard radiographic protocols should include appropriate views based on fracture location 7
• CT is useful for complex fracture patterns or suspected intra-articular involvement 7
• Weight-bearing radiographs can detect dynamic abnormalities not apparent on non-weight-bearing images 7

Importance of Proper Classification

• Ideal fracture classification should be reliable, reproducible, all-inclusive, mutually exclusive, logical, and clinically useful 4
• Proper classification facilitates communication between physicians, guides treatment decisions, and helps estimate prognosis 4
• The unified OTA and AO classification system provides a standardized alpha-numeric code for fractures throughout the skeleton 8