In Situ Deformation of First Tarsometatarsal Arthrodesis Implants with Digital Image Correlation: A Cadaveric Study

Hallux valgus can be addressed through realignment and arthrodesis of the first tarsometatarsal joint. This study aimed to characterize the biomechanical performance of two implant constructs in a matched-pair cadaveric model. Simulated first tarsometatarsal arthrodesis utilized either a lag screw plus locking plate or nitinol staple construct placed in 90-degree configuration. In situ digital image correlation was performed on fresh-frozen cadaveric specimens to characterize 1st tarsometatarsal gapping during cyclic loading. Interfacial characteristics were analyzed with gap displacement allowed by the implant following cyclical loading. The locking plate and nitinol staple constructs gapped 1.367 ± 0.917 mm and 2.116 ± 0.8934 mm, respectively, under 50 N. Removing load, the locking plate and nitinol staple constructs measured 0.3898 ± 0.3787 mm and 0.673 ± 0.5467 mm of residual gapping, respectively. In our cadaver model, both constructs maintained compression and residual stability of the first tarsometatarsal joint gap under 3 mm. Contrary to our synthetic bone study, the locking plate constructs provided statistically superior performance during loading compared to nitinol staples.