Biomechanical Performance of 4-Leg Sustained Dynamic Compression Staples in First Tarsometatarsal Arthrodesis.

Background: This study investigates the biomechanical efficacy of new 4-leg Sustained Dynamic Compression (SDC) NiTiNOL staples, hypothesized to offer superior stability and resilience to loading before fusion completion, compared with conventional hardware.

Methods: Twenty sawbones left full foot models were divided into 4 treatment groups: (1) 4-leg Inline Staple, (2) 4-leg Inline Staple + 2-leg Staple, (3) 4-leg Inline Staple + Screw, and (4) Plate + Screw. An osteotomy was performed to simulate a Lapidus procedure, and the respective fixation methods were applied. Mechanical testing was conducted using a servo-hydraulic testing machine to evaluate constructs' load, contact force, contact area, and plantar gap.

Results: The 4-leg Inline Staple + Screw group demonstrated significantly increased joint contact force, joint contact area, and decreased plantar gap compared with the Plate + Screw group, both before and after cyclic testing. All SDC-containing constructs exhibited post-cyclic joint contact areas that were 2.36×, 3.87×, and 5.49× greater than the post-cyclic plate + screw group. Most notably, the 4-leg Inline Staple + Screw group maintained a plantar gap of less than 3 mm throughout the testing, unlike other groups.

Conclusions: The 4-leg Inline SDC Staple, particularly when combined with a static screw, demonstrated biomechanical superiority over traditional plate and screw constructs in Lapidus procedures. These findings suggest a promising avenue for enhanced post-operative stability, which could translate into quicker patient recovery, improved fusion rates, and potentially lower non-union rates. Further clinical trials are warranted to validate these biomechanical advantages in patient outcomes.

Level of evidence: Therapeutic, Level V: Bench Testing.