What are the concepts of absolute and relative stability in orthopedic treatments, and how do devices such as Dynamic Compression Plate (DCP), Limited Contact Dynamic Compression Plate (LCDCP), Locking Compression Plate (LCP), Intramedullary (IM) nail, External Fixator (Ex Fix), and Ilizarov frame, as well as adjuncts like Transcutaneous Electrical Nerve Stimulation (TENS), apply to different types of fractures and patient conditions?

Absolute and Relative Stability in Orthopedic Fracture Fixation

Core Biomechanical Concepts

Absolute stability achieves rigid fixation with zero motion at the fracture site, promoting primary bone healing through direct cortical remodeling without callus formation, while relative stability permits controlled micromotion that stimulates secondary bone healing through callus formation. 1

Absolute Stability Characteristics

• Achieves interfragmentary compression with zero motion at fracture site 1
• Promotes primary (direct) bone healing without visible callus formation 2
• Requires anatomic reduction with restoration of cortical continuity 3
• Results in significantly faster radiological union (median 14 weeks vs 25 weeks for relative stability in simple fractures) 2

Relative Stability Characteristics

• Permits controlled micromotion at fracture site while maintaining alignment 1
• Promotes secondary (indirect) bone healing through callus formation 1
• Preserves periosteal blood supply through biological fixation techniques 4
• Demonstrates union rates exceeding 90% despite longer radiological healing time 4, 2

Device-Specific Applications

Dynamic Compression Plate (DCP) and Limited Contact-DCP (LC-DCP)

• DCP/LC-DCP achieve absolute stability through interfragmentary compression in simple fracture patterns (AO/OTA type A and B) 2, 5
• LC-DCP reduces contact area with bone compared to traditional DCP, theoretically preserving periosteal blood supply 5
• Both devices show equivalent functional outcomes with no significant difference in range of motion, grip strength, or DASH scores 5
• Indicated for simple diaphyseal fractures requiring anatomic reduction, particularly forearm fractures 5

Locking Compression Plate (LCP)

• LCP provides angular stability through fixed-angle locking screws, functioning as internal-external fixator 1, 6
• Can achieve either absolute stability (with compression through combination holes) or relative stability (with locking screws alone) 1
• Mandatory for complex type C fractures, periprosthetic fractures, and osteoporotic bone 4
• LISS (Less Invasive Stabilization System) variant demonstrates 90% union rate in distal femur fractures through biological fixation 4
• Shows no superiority over LC-DCP in simple forearm fractures but essential for complex fracture patterns 5

Intramedullary (IM) Nails

• IM nails provide relative stability through load-sharing fixation with controlled axial micromotion 1, 4
• Cephalomedullary nails are mandatory for subtrochanteric and reverse obliquity hip fractures (strong recommendation) 7, 3, 8
• Retrograde IM nailing demonstrates 90% union rate in distal femur fractures with minimal soft tissue disruption 4
• Preferred for bilateral or multisegmental lower extremity fractures and extra-articular fractures 4
• Either sliding hip screw or cephalomedullary device acceptable for stable intertrochanteric fractures 7, 3

External Fixators and Ilizarov Frames

• External fixators provide relative stability and are indicated for damage control orthopedics when definitive fixation cannot be performed within 24-36 hours 7
• Temporary stabilization by external fixators preferred over skeletal traction in hemodynamically unstable patients 7
• Ilizarov frames permit gradual correction and controlled micromotion through circular frame construct 1
• External fixation allows safe definitive surgery conversion within 36-48 hours once hemodynamic stability achieved 7

Clinical Decision Algorithm

For Simple Fractures (AO/OTA Type A-B)

1. Use absolute stability (DCP/LC-DCP with lag screws) for simple diaphyseal fractures requiring anatomic reduction 2
2. Absolute stability reduces time to radiological union by 11 weeks (HR 2.60, p<0.001) 2
3. Open reduction and internal fixation (ORIF) appropriate when soft tissue permits 4

For Complex Fractures (AO/OTA Type C)

1. Use relative stability (LCP/LISS or IM nail) for complex articular or comminuted fractures 4
2. Minimally invasive plating (MIPO) preserves biology and achieves >90% union despite longer healing time 4, 2
3. Locked plating mandatory for periprosthetic and osteoporotic fractures 4

For Hip Fractures

1. Stable intertrochanteric: sliding hip screw or cephalomedullary nail (both acceptable) 7, 3
2. Unstable intertrochanteric, subtrochanteric, or reverse obliquity: cephalomedullary nail (mandatory) 7, 3, 8
3. Displaced femoral neck: arthroplasty over fixation (strong recommendation) 7

For Damage Control Situations

1. Apply external fixator for temporary stabilization in hemorrhagic shock with vascular injury 7
2. Convert to definitive fixation within 36-48 hours once hemodynamically stable 7
3. Avoid skeletal traction—external fixation superior for temporary stabilization 7

Critical Pitfalls to Avoid

Biomechanical Errors

• Never use sliding hip screw for subtrochanteric fractures—cephalomedullary nail mandatory 8
• Do not add lag screws to achieve absolute stability if it compromises soft tissue envelope—biology trumps biomechanics in complex fractures 2
• Avoid locked plating in simple fractures when absolute stability with compression achieves faster union 2

Technical Considerations

• Precise preoperative planning required for both IM nailing and locked plating to reduce revision surgery risk 4
• Clinical outcome depends more on surgical technique than implant choice 4
• Far cortical locking combines dynamization with locked plating for superior distal femur healing 6

Postoperative Management

• Immediate full weight-bearing as tolerated after hip fracture surgery—non-weight bearing for 6 weeks is harmful 8
• Monitor serial radiographs for fracture healing progression, maintenance of reduction, and hardware complications 3
• All patients require systematic osteoporosis evaluation including DEXA scan, vitamin D, calcium, and PTH levels 3, 8