Biomechanical Comparison Between Fixation Techniques for First-Metatarsophalangeal Joint Arthrodesis

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Materials science

Background:

• Metatarsophalangeal (MTP) arthrodesis is a standard treatment for severe foot deformities.
• Traditional fixation methods utilize stainless steel or titanium plates with screws.
• Nitinol, a superelastic alloy, presents potential for dynamic compression in MTP arthrodesis.

Purpose of the Study:

• To biomechanically compare nitinol constructs with traditional plate-and-screw fixation for first-MTP arthrodesis.
• To evaluate the hypothesis that nitinol constructs offer comparable or superior performance.

Main Methods:

• Three fixation groups were tested using cadaveric metatarsophalangeal joints: plate-and-screw (PS), nitinol staple and cross screw (NSS), and nitinol hybrid screw (NHS).
• Specimens underwent cyclic loading (20-90 N at 1 Hz for 100 cycles) followed by failure testing.
• Key outcome measures included failure load, stiffness, deflection, and gapping.

Main Results:

• Nitinol constructs (NSS and NHS) exhibited significantly higher failure loads and stiffness compared to the PS construct.
• Both nitinol constructs showed reduced deflection after cyclic loading and decreased gapping at failure.
• No significant biomechanical differences were found between the NSS and NHS constructs.

Conclusions:

• Nitinol constructs demonstrate superior mechanical properties for MTP arthrodesis compared to traditional plate-and-screw fixation.
• The findings support the use of nitinol in joint fusion procedures to enhance load-to-failure resistance and minimize displacement.
• Nitinol's superelastic properties offer a promising alternative for improving outcomes in MTP arthrodesis.