Long-term absorption of poly-L-lactic Acid interference screws

Area of Science:

• Orthopedic surgery
• Biomaterials science
• Radiology

Background:

• Poly-L-lactic acid (PLLA) interference screws are used in anterior cruciate ligament (ACL) reconstruction.
• Long-term in vivo degradation and bone integration of these screws require evaluation.

Purpose of the Study:

• To assess the long-term in vivo degradation of PLLA interference screws used in ACL reconstruction.
• To evaluate bone ingrowth and tunnel healing at least 7 years post-surgery using CT and radiography.

Main Methods:

• 20 patients who underwent ACL reconstruction with PLLA screws were evaluated at a minimum of 7 years post-surgery.
• Radiography and CT scans were used to assess screw degradation and bone ingrowth.
• Clinical outcomes were measured using Lysholm, Tegner, Cincinnati, and IKDC scores.

Main Results:

• No intact PLLA screws remained after 7 years; screw tracts showed fibrous tissue with low Hounsfield units.
• Bone plug fused to the tunnel wall, but no significant bone ingrowth occurred at the screw site.
• Patients reported good functional outcomes with minimal side-to-side laxity.

Conclusions:

• PLLA interference screws completely degrade over time and are not replaced by bone.
• ACL tunnels fill with nonossified fibrous tissue, not new bone.
• This study provides a benchmark for evaluating newer biodegradable screws designed for bone ingrowth.