Mechanical analysis of resorbable plates for long-term soft-tissue molding

BACKGROUND:: Resorbable plates are used with increasing frequency in pediatric craniofacial surgery. A recent innovation has been the use of these plates in long-term soft-tissue molding. However, these plates were not designed for these applications, and an unanswered question remains the mechanical rigidity and stability of the plate when placed in a prolonged out-of-plane bend. METHODS:: Ten varieties of resorbable plates were folded to a right angle and subjected to a standardized 80-g load at body temperature over a duration of 2 weeks. Angle height was measured as an index of the ability of the plate to maintain its out-of-plane bend against an axial force. Each plate was subjected to 3 successive tests, after bending back to its original configuration. RESULTS:: All plates showed a progressive decrease in angle height over 2 weeks. Thickness of the plate appeared to correlate with mechanical rigidity and ability to maintain out-of-plane bend. The plates that performed the best were the Synthes PLGA (85/15) 1.2-mm and BioGeneral PLA (poly-D,L-lactic acid) 1.0-mm plates. Decrease in angle height occurred over shorter intervals in successive tests. CONCLUSIONS:: Of all the plates tested, none were able to maintain initial out-of-plane bend over 2 weeks of testing. Further research and development by industry are required to optimize mechanical properties of resorbable plates for applications in soft-tissue molding.