A Bioabsorbable Fixation Implant for Use in Proximal Interphalangeal Joint (Hammer Toe) Arthrodesis: Biomechanical Testing in a Synthetic Bone Substrate

The surgical correction of hammer toe deformity of the lesser toes is one of the most commonly performed forefoot procedures. In general, percutaneous Kirschner wires are used to provide fixation to the resected proximal interphalangeal joint. Although these wires are effective, issues such as pin tract infections as well as difficult postoperative management by patients make alternative fixation methods desirable. This study biomechanically compared a threaded/barbed bioabsorbable fixation implant made of a copolymer of 82% poly-L-lactic acid and 18% polyglycolic acid with a 1.57-mm Kirschner wire using the devices to fix 2 synthetic bone blocks together. Constructs were evaluated by applying a cantilever load, which simulated a plantar force on the middle phalanx. In all cases, the failure mode was bending of the implant, with no devices fracturing. The stiffness (approximately 6-9 N/mm) and peak load (approximately 8–9 N) of the constructs using the 2 systems were equivalent. Accelerated aging at elevated temperature (47°C) in a buffer solution showed that there was no reduction in mechanical properties of the bioabsorbable system after the equivalent of nearly 6 weeks in a simulated in vivo (37°C) environment. These results suggest that the bioabsorbable implant would be a suitable fixation device for the hammer toe procedure.