Degradation of LactoSorb fixation devices in the craniofacial skeleton

Numerous reports about bioabsorbable internal fixation in the craniofacial skeleton substantiate successful clinical outcomes, especially in pediatric patients. Despite this, little physicochemical data exist to document the rate of device degradation in the human body. In vitro and in vivo animal studies are often used to study the degradation characteristics during product development; however, there has been little effort to correlate preclinical device degradation studies with clinical studies. This study analyzed a fragment of a LactoSorb copolymer plate that was removed from a 17-month-old patient with sagittal synostosis after 3 months' residence. The retrieval was performed during the second part of a planned 2-stage intervention. The fragment was white, opaque, and very brittle, with some signs of mass loss. The inherent viscosity, a measure of mean molecular weight, was determined to be 0.32 ± 0.02 dL/g. LactoSorb implants, as manufactured, have an inherent viscosity of about 1.30 to 1.55 dL/g. Thus, the inherent viscosity was reduced by approximately 75% to 80% over this 3-month interval in the patient. Assuming an exponential decline in inherent viscosity over time, this corresponds to a half-life of about 40 to 44 days. This may be compared with a half-life of about 36 to 45 days derived from prior in vitro studies. The mass loss observed in the LactoSorb implants also corresponds, qualitatively, to that which has been shown to occur in animal models. Thus, the limited data at hand suggest that the degradation profile of LactoSorb copolymer in this human patient is consistent with that reported in prior in vitro and in vivo animal studies.