Dual-Plate Allograft Reconstruction for Expansile Lytic Lesions of the Metacarpal May Allow for Immediate Postoperative Weightbearing in a Biomechanical Setting.

Abstract

This biomechanical study investigates whether reconstruction of expansile lesions of the metacarpal with fibular allograft and a dual-plate construct is strong enough for immediate postoperative weightbearing. Twelve cadaveric middle finger metacarpals (6 matched pairs) from adult donors were used. One side of each pair was randomly assigned to undergo allograft reconstruction with dual plating (experimental construct). The matched contralateral side was assigned to the control construct, a transverse fracture with standard, 8-hole dorsal plating. In the experimental construct, an expansile bone lesion was simulated in the native metacarpal by resecting 1.5 cm from the proximal carpometacarpal joint to 1.5 cm from the distal articular surface and was reconstructed with fibular allograft. Biomechanical testing was performed by a 6-degree-of-freedom robotic KUKA manipulator. The distal portion of each specimen was clamped in place, and a cantilever bending force was applied by the KUKA to test the load to failure. Failure was defined as periprosthetic fracture, fracture displacement, or screw pullout. Paired <i>t</i> tests were used to compare load to failure between matched pairs (R studio). Significance was set at <i>P</i> < .05. The load to failure of dual-plate allograft constructs did not significantly differ from that of the control construct, 494.7 ± 239.07 N (95% CI, 243.81-745.59 N) versus 342.2 ± 99.9 N (95% CI, 237.45-447.04 N), <i>P</i> = .19. Experimental constructs failed at the proximal allograft-native bone interface. Control constructs failed via fracture displacement. Dual-plate fixation constructs for allograft reconstruction of the metacarpal are comparable in mechanical stability to standard metacarpal fracture fixation that allow for immediate postoperative range of motion.