Radiographic Results of Nitinol Compression Staples for Hindfoot and Midfoot Arthrodeses

Background: The purpose of this study was to determine the radiographic union rate after midfoot and hindfoot arthrodeses using a new generation of nitinol staples, and to compare outcomes between a nitinol staple construct and a nitinol staple and threaded compression screw construct. Methods: A retrospective chart review was performed to identify patients who underwent hindfoot or midfoot arthrodesis using a new generation of nitinol compression staples with or without a partially threaded cannulated screw with minimum 3-month radiographic follow-up. The primary outcome variable was radiographic evidence of arthrodesis on radiographs and, when available, computed tomographic scan in patients who underwent midfoot or hindfoot arthrodesis using nitinol staples. Ninety-six patients and 149 joints were eligible for analysis. Median radiographic follow-up was 5.7 months. Results: Radiographic union was seen in 93.8% (60/64) of patients and 95.1% (98/103) of joints using the nitinol staple construct. Radiographic union was seen in 90.6% (29/32) of patients and 95.7% (44/46) of joints using the nitinol combined staple and screw construct. There was no significant difference in radiographic union rate or revision surgery between the 2 groups. Seven patients developed nonunion, 4 in the nitinol staple construct group and 3 in the staple and screw group. Conclusions: New-generation nitinol staples were safe and effective for hindfoot and midfoot arthrodeses, with a high radiographic union rate. The use of a partially threaded screw for additional fixation was not found to either significantly increase or decrease radiographic fusion with nitinol staple fixation.