External ring fixation versus screw fixation for ankle arthrodesis: a biomechanical comparison

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Podiatric Medicine

Background:

• External ring fixation is an alternative to internal screw fixation for ankle arthrodesis, especially with poor bone quality or complex pathology.
• It allows for earlier weight-bearing and postoperative adjustments.
• This study compares the initial fixation integrity of external ring fixation versus internal screw fixation.

Purpose of the Study:

• To determine differences in initial ankle joint fixation integrity between external ring fixation and internal screw fixation techniques.
• To compare the biomechanical stability of ankle arthrodesis using these two methods.

Main Methods:

• Ankle arthrodesis was performed on ten cadaveric lower extremities using a hybrid ring fixator.
• Bending and torsional stiffness of the arthrodesed joint were quantified.
• The process was repeated after removing external fixators and performing arthrodesis with cannulated screws.

Main Results:

• No statistically significant difference was found in bending stiffness between the two techniques.
• Torsional stiffness showed no significant difference between external ring fixation and screw fixation.
• Joint rotation under torsional load was comparable for both fixation methods.

Conclusions:

• External ring fixation provides comparable primary stability to screw fixation for ankle arthrodesis under the tested conditions.
• External fixation is a viable option when internal fixation is problematic due to suboptimal bone quality or complex ankle pathology.