Minimal Versus Maximal Plate Fixation Techniques of the Ulna: The Biomechanical Effect of Number of Screws and Plate Length

Abstract

Objective To test the hypothesis that longer plates with the minimum number of screws provide equivalent or superior strength of fixation to standard compression plating using the maximum number of screws. Design Prospective analysis of biomechanical data was performed. Setting In vitro experimentation. Interventions A reproducible osteotomy was made in formalin-fixed ulnae. The osteotomies were stabilized employing six-, eight-, or ten-hole plates with two screws in the outermost holes and two screws in the innermost holes, and compared to stabilization with a six-hole plate with six screws. Main Outcome Measure Four-point mechanical testing to failure was performed in both apex–dorsal (tension-band) or medial–lateral bending modes. Load–displacement curves were obtained. Results All of the longer plates with the minimum number of screws were stronger than the six-hole plate with six screws when tested in the medial–lateral and the tension–band mode. The eight-hole plate with four screws, however, was statistically inseparable from the fully loaded six-hole plate. There was no statistical difference between any of the configurations in regard to the stiffness of the fixation. Conclusions In a cadaveric ulnar osteotomy model stripped of soft tissue, the number of screws is less important than the length of the plate in providing bending strength to the construct.