Poly (96L/4D-Lactide) implants for repair of orbital floor defects: an in vitro study of the material properties in a simulation of the human orbit

Abstract

To test the mechanical and physical properties of two types of poly(96L/4D-lactide) (PLA96) implants and to evaluate their suitability for repair of large orbital floor defects, a study using an in vitro set-up was performed. Implants, 0.2 mm thick and 28 mm in diameter, were produced by either an extrusion process (type A) or by direct machining (type B) and had a molecular weight (Mw) of 64 x 103 and 146 x 103 g/mole, respectively, after y-sterilization with a dose of 25 kGy. The implants were tested over 8 weeks in an apparatus simulating the human orbit with a 3.1 cm 2 orbital floor defect under a static load corresponding to a retrobulbar pressure of 13 mm Hg as well as unloaded. Both implant types were able to counteract the applied static load without fracturing or excessive sagging. The type A implants sagged more than the type B implants (2.34-0.1 mm versus 1.0 _ 0.0 mm, p < 0.01) but retained and even increased their strength during the study whereas the type B implants showed a gradual strength-loss. In the clinical setting the observed sagging in both types would not have resulted in positional changes of the eyeball. It is concluded that with respect to the mechanical properties, both types of PLA96 implants tested are suitable for repair of large orbital floor defects.

Micro‐porous composite scaffolds of photo‐crosslinked poly(trimethylene carbonate) and nano‐hydroxyapatite prepared by low‐temperature extrusion‐based additive manufacturing

“…The E modulus of the photo‐crosslinked PTMC‐MA/nHA/N was 24 MPa, with a yield strength of 0.5 MPa. In applications with low loading such as orbital floor reconstruction (where peak stresses on the implant are 4 kPa), this should be sufficient.…”

Reconstruction of orbital wall defects: recommendations based on a mathematical model

“…Based on the research by Cordewener et al it was assumed that the pressure load (p) on the orbital floor implant due to the load of the orbital content after trauma was about 13 mmHg (1.73 kPa) (Cordewener et al, 1995). This assumption is based on the fact that the normal retrobulbar pressure (RBP) in humans ranges from 3 to 4.5 mmHg.…”