Clinical and Radiographic Outcomes of Nitinol Compression Staples for Midfoot and Chopart Arthrodesis

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Nitinol staple use in orthopedic surgery has increased in recent years. Biomechanical studies provide useful data for use in foot/ankle; however, clinical data is limited. This study's purpose is to determine the efficacy of nitinol staples to achieve stable, bony arthrodesis in midfoot and Chopart joints, and examine their clinical outcomes and pain scores. A retrospective chart review was performed on 127 midfoot/Chopart joint arthrodeses (71 patients) using nitinol staples in isolation. The primary outcome variable was radiographic evidence of healing. Radiographs were blinded, randomized, and independently reviewed by three board certified foot and ankle surgeons. Complete/partial union was seen in 89% of all joints (113/127), increasing to 93% when including only midfoot joints (98/106). Chopart joints had significantly lower healing rates (15/21; 71%) compared to all midfoot joints (p = 0.01) and isolated tarsometatarsal joints (86/91; 95%) (p = 0.006). Neuropathy and smoking did not affect arthrodesis, but diabetes did (p = 0.004). Joints requiring bone grafting had worse rates of arthrodesis (38/49; 76%) (p = 0.002). For all joints, post-operative visual analog scale scores were significantly lower than pre-operative (p < 0.001). Pre-operative midfoot and Chopart pain scores were similar (p= 0.30). Midfoot joints had significantly lower pain scores post-operatively than pre-operatively (p < 0.001). No such significance existed in Chopart joints (p = 0.07). Isolated nitinol staples are a viable option for midfoot arthrodesis, especially tarsometatarsal joints, and offer significant pain improvement. Chopart joints may require more rigid fixation than nitinol staples, given the lower healing rate. Level of Clinical EvidenceIV