Bioabsorbable screw fixation in coracoclavicular ligament reconstruction

Area of Science:

• Orthopedic surgery
• Biomaterials science
• Biomechanics

Background:

• Clavicle fractures often involve the coracoclavicular ligaments.
• Surgical fixation aims to restore stability and promote healing.
• Evaluating biomechanical properties of fixation devices is crucial for clinical success.

Purpose of the Study:

• To compare the biomechanical properties of stainless steel (SS) and poly L-lactic acid (PLLA) screws for coracoclavicular fixation.
• To assess pullout strength, stiffness, and elongation to failure for both screw types.

Main Methods:

• Seven matched pairs of fresh frozen human shoulders were used.
• Soft tissues were removed, leaving only the acromioclavicular and coracoclavicular ligament complexes.
• Shoulders were randomly assigned for fixation with either 4.5-mm SS screws or 4.5-mm PLLA screws.
• Mechanical testing using an Instron Mechanical Tester measured pullout strength, stiffness, and elongation to failure.

Main Results:

• The average pullout strength for SS screws was 720.6 N +/- 244.9 N.
• The average pullout strength for PLLA screws was 580.4 N +/- 188.6 N.
• No statistically significant difference (p = 0.089) was found between the pullout strengths of SS and PLLA screws.
• Both screw types exceeded the reported strength of the intact coracoclavicular complex (500 N).

Conclusions:

• Both stainless steel and biodegradable PLLA screws provide adequate initial biomechanical strength for coracoclavicular fixation.
• The comparable biomechanical performance suggests potential for biodegradable screws as a viable alternative to metal screws in clavicle fixation.