Bicortical Compression and Construct Stability With Variable Pitch Locking Screws in Cadaveric Specimens

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Trauma surgery

Background:

• Variable pitch locking screws are designed to enhance compression and stability in orthopedic fixation.
• Standard locking screws are widely used but may offer less compression.
• Bicortical fixation is a common technique for stabilizing bone fractures.

Purpose of the Study:

• To compare the interfragmentary and plate-bone compression achieved by variable pitch locking screws versus standard locking screws.
• To evaluate the biomechanical stability of constructs using variable pitch versus standard locking screws in bicortical fixation scenarios.

Main Methods:

• Nine matched pairs of cadaveric distal tibiae and fibulae were used.
• Compression was measured with variable pitch and standard locking screws at increasing torque in distal tibiae.
• Fibula constructs with either variable pitch or standard locking screws underwent cyclic axial/torsional loading and 4-point bending tests.

Main Results:

• Variable pitch locking screws generated significantly higher interfragmentary and plate-bone compression in distal tibiae compared to standard screws.
• No significant differences in axial or angular displacement were observed in cyclic loading of fibula constructs.
• Construct stiffness and maximum force to failure were comparable between variable pitch and standard locking screw constructs in 4-point bending.

Conclusions:

• Variable pitch locking screws enhance compression in bicortical fixation compared to standard locking screws.
• The biomechanical stability of variable pitch locking screw constructs is similar to standard locking screw constructs in a stable bicortical fibula fixation model under external loading.