Distal Locking Screws for Intramedullary Nailing of Tibial Fractures

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Trauma research

Background:

• Distal tibial fractures often involve the metaphysis and require stable fixation.
• Intramedullary nails offer advantages, but optimal distal screw configurations for unstable fractures are unclear.
• Current techniques aim to reduce malalignment and fixation loss using multiple distal screws.

Purpose of the Study:

• To biomechanically evaluate the stability of different distal screw configurations with the Expert tibial nail for unstable distal tibial fractures.
• To determine if increasing the number of distal screws beyond two enhances construct stability.
• To provide evidence-based guidance on screw selection for optimal fixation.

Main Methods:

• Thirty-six Expert tibial nails were implanted in composite bone models simulating a 42-C3 distal tibial fracture with a 7-mm gap osteotomy.
• Models were divided into four groups based on distal locking configurations (2, 3, or 4 screws).
• Nondestructive biomechanical testing assessed axial compression, coronal bending, and axial torsion, with passive construct stiffness measured.

Main Results:

• No statistically significant differences in construct stiffness were found between the groups for compression (P=.105), bending (P=.801), external rotation (P=.246), or internal rotation (P=.370).
• Minor variations in stiffness were observed, but these did not reach statistical significance.
• The 2-parallel screw configuration demonstrated comparable stability to configurations with more screws.

Conclusions:

• The classic configuration of two parallel distal screws provides adequate stability for the Expert tibial nail in treating unstable distal tibial fractures under partial weight-bearing conditions.
• Increasing the number of distal screws beyond two did not yield statistically significant improvements in biomechanical stability in this in vitro study.
• Surgeons can confidently use the two-screw configuration for these fractures, simplifying surgical planning and potentially reducing hardware-related complications.