Structural asymmetry between the hips and its relation to experimental fracture type

Area of Science:

• Orthopedics
• Biomechanics
• Gerontology

Background:

• Hip fractures are a major health concern, particularly in older adults.
• Understanding the structural factors contributing to fracture type is crucial for prevention and treatment.
• Paired femur analysis allows for within-person comparisons of structural properties and fracture patterns.

Purpose of the Study:

• To investigate the association between structural asymmetry of the femur and hip fracture type (cervical vs. trochanteric).
• To evaluate differences in bone mineral density (BMD), structural parameters, and failure load between left and right femurs and between fracture types.

Main Methods:

• Paired cadaver femurs (32 females, 24 males) were analyzed for BMD and structural properties.
• Mechanical testing was performed in a side-impact configuration to induce fractures.
• Fractures were classified as cervical or trochanteric, and structural differences were compared between sides and fracture types.

Main Results:

• Significant structural asymmetry was observed between left and right femurs, including larger dimensions and thicker cortices on the left.
• 30.4% of pairs exhibited different fracture types (trochanteric vs. cervical) on contralateral sides.
• Asymmetric fracture sides showed distinct structural characteristics (e.g., head/neck diameter ratio, neck-shaft angle) compared to symmetric sides and fracture types, with variations between sexes.
• Bone mineral density and failure load increased from symmetric cervical to asymmetric to symmetric trochanteric fractures.

Conclusions:

• Intrasubject structural asymmetry is associated with differing hip fracture types.
• The contralateral femur cannot be reliably used as a control in clinical studies due to inherent asymmetry.
• Considering individual structural asymmetry is vital for accurate clinical assessments and research designs related to hip fractures.