Biomechanical Analysis of Headless Compression Screw Versus Tension Band for Proximal Interphalangeal Joint Arthrodesis
Nathan Heineman, MD1, Dang-Huy Do, MD1, Junho Ahn, MD1, Douglas Sammer, MD2 and Daniel M Koehler, MD1, (1)UT Southwestern Medical Center, Dallas, TX, (2)Plastic Surgery, Division of Hand Surgery, University of Texas Southwestern, Dallas, TX
INTRODUCTION: Proximal interphalangeal joint (PIPJ) arthrodesis is a commonly employed procedure to address arthritis, instability, and deformity. There are multiple fixation methods available to maintain stability across the arthrodesis interval including headless compression screw (HCS), tension band, plating, and Kirschner wiring constructs. The purpose of this study was to compare the stiffness and load to failure biomechanical properties of the HCS and tension band techniques in a cadaveric model.
METHODS: Thirty-two non-thumb digits, each disarticulated at the metacarpophalangeal joint, were prepared from 8 paired upper limbs of four cadavers. Each finger was paired with the matching contralateral digit from the same specimen. One PIPJ of each pair was fused with an antegrade 3.5 mm HCS and the second was fused with a tension band construct utilizing a pair of 0.035â€� Kirschner wires with 24-gauge dental wire. Left and right hand specimens were evenly distributed between the fusion groups. Each PIPJ fusion construct was then stressed to 10 N in the radial deviation, ulnar deviation, flexion, and extension planes and stiffness (N/mm) was calculated. The fingers were stressed to failure in extension with the ultimate load and mode of failure recorded.
RESULTS: When stressed in extension, the HCS construct had a significantly greater mean stiffness than the tension band construct for PIPJ arthrodesis (16.4 N/mm vs. 10.8 N/mm, p=0.009). No significant differences were identified in stiffness when loading in ulnar deviation, radial deviation, or flexion. The mean ultimate load to failure in extension was 91.4 N for the HCS and 41.9 N for the tension band (p=0.0002). The mean load to produce 0.5 mm of displacement was 7.4 N for the HCS and 4.3 N for the tension band. The most common mode of failure for the HCS was fracture of the dorsal lip of the proximal phalanx (13/16). The most common mode of failure for the tension band construct was bending of the Kirschner wires (15/16).
CONCLUSIONS: In this cadaveric model, fusion of the PIPJ using a HCS resulted in a construct that was significantly stiffer in extension with greater than double the load to failure when compared to a tension band construct. While the stiffness required to achieve successful PIPJ arthrodesis has not been well quantified, the HCS proved to be the most favorable construct with respect to initial strength and stability.
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