Smart toe® implant versus buried Kirschner wire for proximal interphalangeal joint arthrodesis: a comparative study

The surgical correction of hammer digits offers a variety of surgical treatments ranging from arthroplasty to arthrodesis, with many options for fixation. In the present study, we compared 2 buried implants for arthrodesis of lesser digit deformities: a Smart Toe® implant and a buried Kirschner wire. Both implants were placed in a prepared interphalangeal joint, did not violate other digital or metatarsal joints, and were not exposed percutaneously. A retrospective comparative study was performed of 117 digits with either a Smart Toe® implant or a buried Kirschner wire, performed from January 1, 2007 to December 31, 2010. Of the 117 digits, 31 were excluded because of a lack of 90-day radiographic follow-up. The average follow-up was 94 to 1130 days. The average patient age was 61.47 (range 43 to 84) years. Of the 86 included digits, 48 were left digits and 38 were right. Of the digits corrected, 54 were second digits, 24 were third digits and 8 were fourth digits. Fifty-eight Smart Toe® implants were found (15 with 19-mm straight; 2 with 19-mm angulated; 34 with 16-mm straight; and 7 with 16-mm angulated). Twenty-eight buried Kirschner wires were evaluated. No statistically significant difference was found between the Smart Toe® implants and the buried Kirschner wires, including the rate of malunion, nonunion, fracture of internal fixation, and the need for revision surgery. Of the 86 implants, 87.9% of the Smart Toe® implants and 85.7% of the buried Kirschner wires were in good position (0° to 10° of transverse angulation on radiographs). Osseous union was achieved in 68.9% of Smart Toe® implants and 82.1% of buried Kirschner wires. Fracture of internal fixation occurred in 12 of the Smart Toe® implants (20.7%) and 2 of the buried Kirschner wires (7.1%). Most of the fractured internal fixation and malunions or nonunions were asymptomatic, leading to revision surgery in only 8.6% of the Smart Toe® implants and 10.7% of the buried Kirschner wires. Both the Smart Toe® implant and the buried Kirschner wire offer a viable choice for internal fixation of an arthrodesis of the digit compared with other studies using other techniques.