What is bone biomechanics?

Bone biomechanics is the branch of biomechanics that studies the mechanical behavior of bones under different forces and loads.

It analyzes how the musculoskeletal system:

• Supports weight

• Distributes forces

• Maintains stability

• Responds to movement

• Adapts to mechanical stress

Bone tissue possesses biomechanical properties that allow it to resist:

• Compression

• Tension

• Bending

• Torsion

• Shear

Biomechanics is fundamental in:

• Traumatology

• Orthopedics

• Implant Design

• Osteosynthesis

• Rehabilitation

  
  

Understanding these principles allows for the optimization of treatments and the improvement of the stability of orthopedic fixations.

Axial load

Axial loading is a force applied along the longitudinal axis of a bone or anatomical structure.

This type of loading occurs constantly during activities such as:

• Walking

• Running

• Jumping

• Lifting weights

Under normal conditions, bones adequately distribute axial loads thanks to their biomechanical architecture.

However, excessive loads can produce:

• Fractures

• Structural collapse

• Joint injuries

• Bone fatigue

  
  

In orthopedics, understanding axial loading is essential for designing implants and fixation systems that adequately support body forces.

Compression

Compression is a mechanical force that acts by pushing a structure toward its center, reducing its length or volume.

Bones tolerate compressive forces relatively well due to the strength of their cortical and trabecular tissue.

Examples of compression

• Body weight on legs

• Vertebral compression

• Hip load during gait

In osteosynthesis, some implants are designed to generate controlled compression on the fracture site, promoting:

• Stability

• Bone consolidation

• Primary healing

Proper compression improves the bond between bone fragments.

Strain

Tension is a mechanical force that acts by pulling a structure apart in opposite directions.

In the musculoskeletal system, tensile forces are typically produced by muscle and ligament action.

Examples of tension in bone biomechanics

• Muscle traction on bone

• Stretching injuries

• Bone avulsions

Bone has less resistance to tension compared to compression.

In traumatology, some fixation systems convert tensile forces into compression to improve biomechanical stability.

Torsion

Torsion is a rotational force that causes a bone to rotate about its longitudinal axis.

This mechanism generates internal stress that can produce spiral fractures or complex injuries.

Frequent situations

• Sudden twists during sports

• High-energy accidents

• Forced rotational movements

Torsional strength depends on:

• Bone geometry

• Bone quality

• Structural integrity

Modern orthopedic implants aim to adequately control torsional forces to prevent displacement and mechanical failure.

Absolute stability

Absolute stability is a biomechanical concept in which there is no movement between fractured bone fragments.

Its goal is to achieve consolidation through primary bone healing.

Main features

• Absence of micromovement

• Interfragmentary compression

• Precise anatomical alignment

• Direct consolidation

  
  

Methods used

• Compression screws

• Compression plates

• Rigid osteosynthesis

Absolute stability is often used in:

• Joint fractures

• Simple fractures

• Injuries requiring precise anatomical reduction

Relative stability

Relative stability allows for small, controlled movements between bone fragments during the healing process.

This micromovement promotes callus formation and secondary bone consolidation.

Main features

• Controlled micromobility

• Bone callus formation

• Increased biomechanical flexibility

Frequent systems

• Intramedullary nails

• External fixators

• Plate bridges

Relative stability is especially useful in:

• Comminuted fractures

• Diaphyseal fractures

• High-energy trauma

The balance between mobility and stability is key to proper consolidation.

AO Principles

The AO principles are international guidelines developed to optimize the surgical treatment of fractures.

These principles revolutionized modern traumatology and continue to underpin many current techniques.

Fundamental principles

Anatomical reduction

Restore normal bone anatomy.

Stable fixation

Provide adequate stability according to the type of fracture.

Biological preservation

Protect blood supply and soft tissues.

Early mobilization

Promote early functional recovery.

The AO principles aim to improve:

• Bone consolidation

• Patient function

• Clinical outcomes

• Reduced complications

Primary and secondary healing

Bone healing can occur through primary or secondary mechanisms depending on the biomechanical stability of the fracture.

Primary healing

This occurs when there is absolute stability and interfragmentary compression.

Characteristics:

• It does not form a visible callus.

• Direct consolidation.

• Requires minimal mobility.

It is common in:

• Rigid osteosynthesis

• Articular fractures

Secondary healing

It is the most common mechanism of bone consolidation.

It occurs when there is relative stability with controlled micromovement.

Characteristics:

• Bone callus formation

• Progressive biological process

• Greater biomechanical tolerance

Stages of secondary healing

• Inflammation

• Soft callus formation

• Hard callus formation

• Bone remodeling

Both mechanisms are fundamental in traumatology and depend on the fixation technique used.

OSTEONORTE SAS offers solutions and implants for osteosynthesis and traumatology procedures in Colombia.