Interfragmentary lag screw fixation in locking plate constructs increases stiffness in simple fracture patterns

Area of Science:

• Orthopedic biomechanics
• Surgical fixation techniques
• Bone fracture healing

Background:

• Distal femur fractures present complex fixation challenges.
• Locking plates are commonly used for stabilization.
• The role of additional lag screws requires biomechanical evaluation.

Purpose of the Study:

• To quantify the impact of an additional lag screw on construct stiffness.
• To compare fixation stiffness with and without a lag screw in distal femur fractures.

Main Methods:

• Biomechanical testing of paired fresh frozen human femora (5 donors).
• Testing of locking plate constructs with and without interfragmentary lag screws.
• Application of torsional load (2-4 Nm/deg) and axial compression (500-1000 N).

Main Results:

• Constructs with an interfragmentary lag screw demonstrated axial and torsional stiffness similar to intact bone.
• Bridging plate constructs exhibited significantly lower stiffness under both loading conditions.
• The addition of a lag screw enhanced construct stability.

Conclusions:

• Lag screw augmentation of locking plates provides superior axial and torsional stiffness for distal femur fractures.
• This fixation method offers biomechanical advantages over standard bridging plates.
• Findings support the use of lag screws with locking plates for improved fracture stabilization.