Biodegradable device applied in flatfoot surgery: comparative studies between clinical and technological aspects of removed screws.

Poly-L-lactide (PLLA) is one of the most used polymers for biomedical application; its use in sutures and other implants has been widely investigated. Although the knowledge of PLLA biodegradation and biocompatibility features is deep, PLLA screws used to correct the flat foot deformity have deserved attention since they are not degraded in most of cases after a long period of years (3-7) from the implantation. In this article, a clinical and radiological evaluation (NMR, histological and clinical outcomes) on patients was correlated with physico-chemical characterization (by SEM, DSC, GPC and XRD analysis at different temperatures) on both native and patient-recovered screws together with the theoretical degradation processes of PLLA-based implants. The data demonstrated the need for crossing the biodegradation and bioabsorption of the polymer with the characteristics of both the device (geometry, structure and fabrication process) and the implantation site.