What are the differences between absolute and relative stability in orthopedic surgery, including examples such as Dynamic Compression Plate (DCP), Limited Contact Dynamic Compression Plate (LCDCP), Locking Compression Plate (LCP), external fixators (Ex Fix), and the Ilizarov method?

Absolute vs. Relative Stability in Orthopedic Fracture Fixation

Core Concept

Absolute stability achieves faster radiological union compared to relative stability in simple fractures, but the choice between these approaches must be guided by patient physiology, fracture pattern, and soft tissue condition rather than a rigid protocol. 1

Definitions and Biomechanical Principles

Absolute Stability

• Achieves rigid fixation with zero motion at the fracture site, promoting primary bone healing through direct cortical remodeling without callus formation 2
• Requires anatomic reduction with interfragmentary compression
• Results in significantly shorter time to radiological union (median 14 weeks vs. 25 weeks for relative stability in simple humeral shaft fractures) 1

Relative Stability

• Permits controlled micromotion at the fracture site, stimulating secondary bone healing through callus formation 2
• Preserves periosteal blood supply and biological environment
• Better suited for comminuted fractures, osteoporotic bone, and physiologically unstable patients 3

Device-Specific Applications

Dynamic Compression Plate (DCP)

• Designed for absolute stability through interfragmentary compression 4
• Requires precise anatomic reduction and extensive soft tissue dissection
• Best for simple fracture patterns (AO/OTA type A-B) in stable patients 1
• Higher infection risk due to extensive surgical exposure 4

Locking Compression Plate (LCP)

• Provides angular stability without requiring compression against bone, functioning as internal-external fixator 5
• Particularly useful in osteoporotic bone, segmental bone loss, and cortical defects 5
• Can achieve either absolute or relative stability depending on screw configuration 2
• Excellent results in humeral shaft nonunions (91% union rate, mean 16 weeks) 5

Limited Contact Dynamic Compression Plate (LCDCP)

• Reduces contact area with bone compared to standard DCP, preserving periosteal blood supply 2
• Maintains compression capabilities while improving biological environment
• Represents evolution toward balancing mechanical and biological factors 2

External Fixators (Ex Fix)

• Provide relative stability with minimal soft tissue disruption 3
• Mandatory for temporary stabilization in hemodynamically unstable patients with severe limb trauma 3
• Should be preferred over skeletal traction when definitive osteosynthesis cannot be performed within 24-36 hours 3
• Allow immediate weight bearing and adjustment of alignment 4

Ilizarov Method

• Provides relative stability through circular external fixation with tensioned wires 6
• Unique advantages: simultaneous correction of deformity and limb length discrepancy 3
• Superior healing rates compared to plate osteosynthesis in distal tibial fractures (average 130 days vs. 196.5 days) with immediate weight bearing 4
• High complication rates (30-100%) including pin tract infections and refracture rates up to 93% in congenital pseudarthrosis 3
• Best reserved as secondary option when other methods fail or for complex deformities with shortening >5cm 3

Clinical Decision Algorithm

Step 1: Assess Patient Physiology

• In hemodynamic instability, circulatory shock, or respiratory failure: Use external fixation for damage control 3, 7
• Delayed definitive osteosynthesis reduces systemic complications from surgical "second hit" 3, 7
• Stable patients can proceed directly to definitive fixation within 24 hours 3

Step 2: Evaluate Fracture Pattern

• Simple fractures (AO/OTA type A-B): Absolute stability preferred for faster union 1
• Comminuted fractures: Relative stability mandatory to preserve biology 2
• Segmental bone loss or cortical defects: LCP with relative stability 5

Step 3: Consider Soft Tissue Status

• Compromised soft tissues or open fractures: Minimize dissection, favor relative stability 2
• Pristine soft tissues in stable patient: Absolute stability acceptable 1

Step 4: Timing Strategy

• Unstable patients: External fixation → delayed definitive fixation within 2 weeks once stabilized 3
• Stable patients without severe visceral injury: Early definitive osteosynthesis within 24 hours 3
• Daily reassessment of hemodynamic, respiratory, and coagulation status guides conversion timing 3

Critical Pitfalls to Avoid

• Never prioritize immediate definitive fixation over physiologic stability - the "second hit" phenomenon increases mortality and morbidity 3, 7
• Adding lag screws for interfragmentary compression does not further reduce healing time in absolute stability constructs 1
• Ilizarov method alone has unacceptably high refracture rates (up to 93%) - consider combining with intramedullary fixation (reduces refracture to 22.3%) 3
• Elderly patients require angioembolization consideration even with mechanically stable fractures 3
• External fixators should not remain as definitive treatment beyond 2 weeks when conversion is feasible 3

Combined Approaches

Combining external fixation with intramedullary fixation prevents refractures and axial deformities (84% consensus agreement among specialists) 3

• Primary union rate: 84%, final union rate: 93.3% 3
• Refracture rate reduced by >50% compared to external fixation alone 3
• Particularly effective for complex cases with deformity correction needs 3