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Full Threaded Cannulated Screw
Q&A
Q1: What is a Full Threaded Cannulated Screw and what is its primary design feature?
A1: A Full Threaded Cannulated Screw is an orthopedic implant that features a hollow central canal (cannulation) along its entire length, combined with continuous threading from tip to head. This unique design allows it to be inserted over a pre-placed guide wire while providing compression along the entire bone-implant interface.
Q2: What are the main clinical advantages of the fully threaded cannulated design?
A2: Key advantages include:
Precise Placement: Guided insertion over a K-wire ensures accurate screw positioning
Continuous Compression: Provides uniform compression across the entire fracture line
Reduced Migration Risk: Full threading minimizes screw backing-out compared to partially threaded designs
Minimally Invasive: Enables percutaneous insertion for reduced tissue damage
Q3: In which surgical procedures are Full Threaded Cannulated Screws most commonly used?
A3: They are particularly valuable in:
Hip Fracture Fixation: Femoral neck and intertrochanteric fractures
Pelvic and Acetabular Surgery: Sacroiliac joint fixation, pelvic ring fractures
Foot and Ankle Surgery: Subtalar arthrodesis, fracture fixation
Small Bone Fixation: Scaphoid, radial head, and other periarticular fractures
Q4: How does the biomechanical performance compare to partially threaded cannulated screws?
A4: Full threaded screws provide:
Superior Pull-out Resistance: Continuous threads maximize bone purchase
Reduced Stress Shielding: More even stress distribution along the screw length
Better Osteoporotic Bone Fixation: Enhanced holding power in poor quality bone
Elimination of “Lag Effect” Limitations: No stress concentration at thread-shaft junction
Q5: What are the potential challenges or limitations of using Full Threaded Cannulated Screws?
A5: Main considerations include:
Reduced Fracture Compression: Cannot generate the same lag effect as partially threaded screws
Insertion Torque: Higher resistance during insertion due to full threading
Cost: Typically more expensive than standard partially threaded screws
Learning Curve: Requires different surgical technique for optimal use
Q6: How does the cannulation affect the screw’s mechanical strength?
A6: The hollow design reduces:
Torsional Strength: Approximately 15-30% reduction compared to solid screws
Bending Stiffness: Decreased resistance to bending forces
Fatigue Resistance: Potentially reduced in high-stress applications
However, modern designs with optimized wall thickness maintain sufficient strength for most clinical applications.
