A comparison of three adjustable cortical button ACL fixation devices

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Sports medicine

Background:

• Adjustable cortical fixation devices are increasingly used in anterior cruciate ligament (ACL) reconstruction.
• A key concern is the potential for post-operative joint laxity.
• Cyclic displacement in mechanical testing can indicate clinical laxity.

Purpose of the Study:

• To evaluate and compare the cyclic displacement and maximum strength of different adjustable cortical fixation devices.
• To determine if fixation mechanisms influence mechanical performance and potential for laxity.
• Hypothesis: Cyclic displacement and strength vary based on the fixation mechanism of adjustable buttons.

Main Methods:

• Three adjustable fixation devices were tested: ToggleLoc with ZipLoop Technology (ZL), TightRope RT (TR), and RIGIDLOOP Adjustable (RLA).
• Mechanical testing involved pre-conditioning, 1000 cycles of cyclic loading (50-250 N at 1 Hz), and load-to-failure tests.
• Measurements included total cyclic displacement, ultimate strength, and failure modes.

Main Results:

• The RIGIDLOOP Adjustable (RLA) exhibited significantly lower cyclic displacement compared to both TightRope RT (TR) and ZipLoop Technology (ZL).
• The TightRope RT (TR) also showed significantly less displacement than the ZipLoop Technology (ZL).
• Both RLA and ZL demonstrated significantly higher ultimate strength than TR, with RLA and ZL being significantly stronger than TR.

Conclusions:

• The RIGIDLOOP Adjustable (RLA) and TightRope RT (TR) demonstrated clinically acceptable levels of cyclic displacement and maximum strength.
• Bench-top cyclic displacement may correlate with post-operative laxity in ACL reconstruction.
• Minimizing cyclic displacement is crucial for optimal clinical outcomes in ACL reconstruction using adjustable fixation devices.