Absorbable Plate Strength Loss During Molding

Abstract

Bioabsorbable plating systems play an integral role in cranial vault remodeling. After experiencing a case of plate failure requiring emergent reexploration, we investigated the potential causes. We hypothesize that extended submersion in the molding bath during plate preparation might advance the rate of hydrolysis and compromise plate structural integrity. Using an absorbable poly-D/L-lactic acid plating system, we assessed the effect of extended submersion on plate strength and stiffness when loaded in a cantilever fashion and with pure tension. We assessed these differences with the Student t test and linear regression modeling. We also generated a computer model of the plates for finite element analysis. When left in the molding bath for extended periods, the plates changed color and lost strength. After 5 minutes, 30% of maximum plate load capacity was lost in a cantilever beam test (P < 0.001) consistent with use of a 15% thinner plate. Tensile testing revealed the initial elastic modulus of 6.42 +/- 0.13 GPa decreased 16% to 5.41 +/- 0.50 GPa after 5 minutes of submersion (P = 0.027). The changes in plate strength and elastic modulus both worsened with increased submersion times. Finite element analysis of the plates also predicted clinically significant increases in plate deviation under normal loading conditions. Our study demonstrates that extended submersion of absorbable plates during molding results in a significant loss of plate strength and stiffness. Further, our computer model predicts that these changes could result in an unacceptable plate deviation under normal loading conditions. Together, these data caution against overmolding of plates to avoid compromising their structural integrity.

Intracerebral foreign body granuloma caused by a resorbable plate with passive intraosseous translocation after cranioplasty

“…Poly-llactide was used in the next generation, providing sufficient healing time before resorption. As the clinical usage of PLLA broadened from the late 1980s, reports documented successful applications in craniofacial surgeries, but problems such as weakened strength because of extended submersion during molding 1 and long intervals until complete degradation 8 still required attention. Bergsma et al reported that, even after 5.7 years, PLLA implants had not been fully resorbed.…”

Retrospective Review of Resorbable Plate Fixation in Pediatric Craniofacial Surgery

“…It has been demonstrated that too much bending during plate contouring significantly weakens the material, as does leaving a plate too long in the water bath used to heat the plate for bending in the first place. 9 With regard to personal experience, I use resorbable plates in more cases in my pediatric practice than I did 10 years ago, but I use fewer plates. The advantages of reduced risks of intracranial migration and growth interference remain.…”