Mechanical and biological effects of plate luting.

This research article explores the mechanical and biological effects of plate luting – a technique used to improve the stability of internal fixation in bone repairs. Experiments carried out on equine bones demonstrated that while there were no differences in initial strength, the use of plate luting significantly enhanced the longevity under stress. Meanwhile, biological tests showed that the procedure does not increase bone porosity.

Research Methodology

• The research involved testing the technique of plate luting on 20 pairs of equine third metacarpal bones which had been subjected to mid-diaphyseal osteotomies and then plated with six-hole broad ASIF compression plates. This ensured a consistent base for comparison.
• One of each bone pair was luted – a process in which a cement-like substance, polymethylmethacrylate (PMMA), is placed between the plate and the bone, and between the screw heads and the plate. The second bone of each pair was left un-luted to act as a control.
• Each bone – luted and non-luted – was subjected to stress tests. The two methods of testing were static overload and cyclic loading at 75% of the bone’s ultimate breaking strength using four-point bending.

Findings

• No differences were observed in the initial strength (measured through static overload tests) between the luted and non-luted plates. This indicates that the luting process does not change the immediate mechanical stability of the bone repair.
• However, when subjected to repeated stress (cyclic loading tests), the luted bones showed significantly greater resilience. They showed a three to twelve-fold increase in the number of cycles to failure compared to the non-luted bones. This suggests that luting provides a significant improvement in the endurance of the fixation under repeated stress.

Biological Reaction to Plate Luting

• The team conducted in vivo studies on seven horses to examine the biological response to luting. Plates identical to those used in the initial tests were fixed to the intact radius of each subject.
• Plate luting was performed on one side, while the opposite side was plated without luting. The horses were euthanized at intervals of 1, 2, 6, and 15 months after surgery to allow for examination.
• Quantitative histomorphometry analysis (a technique used to analyze the microscopic structure of tissue) revealed that luting does not increase porosity under the luted plate when compared to the non-luted side. In other words, the procedure does not damage or weaken the bone structure beneath the plate.

Implications

• The findings suggest that plate luting could be beneficial in cases requiring internal bone fixation. This method does not compromise initial mechanical stability or the biological integrity of the bone.
• Moreover, plate luting increases the endurance of the fixation, potentially reducing the risk of mechanical failure over time due to repeated stress.