Absolute Stability (AS) vs. Relative Stability (RS)

1. Definitions:

• Absolute Stability (AS): refers to achieving rigid fixation at the fracture site, preventing any motion. It aims for direct visualization, anatomic reduction, and stable fixation.
• Relative Stability (RS): preserves some controlled motion at the fracture site while still promoting healing. It focuses on functional reduction (alignment, rotation, and length) and allows for callus formation.

2. Clinical Considerations:

AS Approach: Indications: Suitable for simple metaphyseal fractures (type A) that require surgical treatment.

• Techniques: Often involves open reduction and internal fixation (ORIF) or plate osteosynthesis.
• Advantages: Faster time to radiographic union. Provides rigid stability. Recommended by the AO foundation for type A fractures.
• Limitations: May involve more extensive soft tissue dissection. Increased risk of non-union in multifragmentary fractures.

RS Approach: Indications: Reserved for multifragmentary fractures where fragment preservation of blood supply is crucial.

• Techniques: Minimally invasive plate osteosynthesis (MIPO) is commonly used.
• Advantages: Biologically friendly approach. Allows controlled motion, stimulating callus formation. May reduce complications.
• Limitations: Longer time to radiographic union. Requires careful patient selection.

3. Research Findings:

A retrospective cohort study evaluated AS vs. RS in MIPO plating for humeral shaft fractures (AO/OTA type 12A1 and 12A2):

• Time to Radiographic Union: AS group: Median time = 12 weeks. RS group: Median time = 18 weeks.
• Complications: Non-union occurred in 7% of RS cases. Radial nerve palsy observed in some RS patients.
• Recommendation: Simple metaphyseal fractures (type A) benefit from AS constructs. RS techniques are suitable for multifragmentary fractures.

4. Controversy and Future Directions:

• Debate continues regarding the advantages of RS over AS.
• Factors like union rtaes, functional outcomes and complications need further investigation.

In summary, while AS provides faster union, RS preserves biological factors. Surgeons choose the appropriate approach based on fracture type and patient factors. Remember that both stability concepts play essential roles in fracture management.