Fabrication of patient specific composite orbital floor implants by stereolithography

Abstract

Fractures of the orbital floor are common in traffic accidents and assaults, and inadequate treatment can result in serious complications. Accurate anatomical reconstruction of the orbit using implants is the preferred treatment. Implants require degradability, adequate mechanical properties to support the orbital contents, and osteoinductivity or osteoconductivity so that the implant is replaced by de novo bone over time. Here, we report on a semi-automatic process for the generation of virtual models of patient-specific implants for orbital floor reconstruction. These models were generated using clinical computed tomography images of five clinical cases of orbital fracture. To fabricate accurately shaped implants based on the models, we utilized stereolithography, a high-resolution additive manufacturing technique. We prepared resins from bioresorbable, photo-curable functionalized poly(trimethylene carbonate) oligomers and osteoinductive nano-hydroxyapatite to manufacture composite implants. Incorporation of 40 wt.% nano-hydroxyapatite into photo-crosslinked poly(trimethylene carbonate) leads to an increase of the E modulus, ultimate strength and toughness from 2.8 to 60 MPa, 2.4 to 7.1 N/mm2 and 330 to 1671 N/mm2, respectively. Additionally, water uptake increased from 0.8% to 7.3%, and water contact angle decreased from 80°to 68°. Patient-specific, homogeneous, and mechanically stable implants can readily be prepared using these composite resins.

Poly(trimethylene carbonate) and nano‐hydroxyapatite porous scaffolds manufactured by stereolithography

“…The formed PTMC with number average molecular weight of 10 kg/mol, as determined by 1 H nuclear magnetic resonance, was thereafter dissolved in dichloromethane under dry N 2 atmosphere. In order to obtain a photo‐crosslinkable compound, PTMC macromer with methacrylate end‐groups (PTMC‐MA) was subsequently prepared by reacting PTMC hydroxyl groups with methacrylic anhydride (from Sigma‐Aldrich), as recently described, in order to obtain a degree of functionalization of 99% …”

Phase‐separated mixed‐macromer hydrogel networks and scaffolds prepared by stereolithography

“…Scaffolds with defined pore structure and connectivity, geometry, mechanical properties, cell‐seeding efficiency, and transport of nutrients and metabolites can be built at a high resolution . Additionally, patient‐specific implants for tissue regeneration based on magnetic resonance imaging or CT scan data can be readily prepared by stereolithography . However, for such purposes, the number of resins based on biocompatible and biodegradable materials is still limited.…”

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

“…A three‐armed PTMC oligomer was prepared by ring‐opening polymerization of TMC initiated by TMP. As reported previously, TMC and TMP were charged in a flask under N 2 atmosphere at a molar ratio of 96.7 to 1 (TMC/TMP). Under N 2 , the polymerization was conducted at 130°C for 3 days using Sn(Oct) 2 as a catalyst at a concentration of 0.13 wt%.…”

“…In contrast, this is not possible by conventional techniques for the preparation of macro‐porous structures such as salt leaching or gas foaming . Additionally, the use of additive manufacturing techniques allows for the fabrication of patient‐specific implants derived from computed tomography (CT) data . This is especially useful for treatment of complex defects such as defects of the orbital floor and walls that require an accurate fit of the scaffold …”