Mechanical and biological effects of plate luting.

Plate luting, a technique that uses polymethylmethacrylate (PMMA) interposed between the plate and the bone, as well as between the screw heads and the plate, to improve the stability of internal fixation was tested in vitro using 20 paired equine third metacarpal bones with mid-diaphyseal osteotomies plated with six-hole broad ASIF compression plates. One of each pair was luted and all specimens were tested in static overload or cyclic loading at 75% of the ultimate breaking strength using four-point bending. Although no differences were measured in static overload tests between luted and nonluted plates, a three to 12-fold increase in the number of cycles to failure was noted with the luted specimens. In vivo studies of the biological reaction to plate luting were performed in seven horses using identical plates fixed to the intact radius. One side was luted while the opposite side was plated without luting. The horses were killed at 1, 2, 6, and 15 months after surgery. Quantitative histomorphometry showed no increase in porosity under the luted plate when compared with the nonluted side.