title: Computer-aided orbital wall defects treatment by individual design ultrahigh molecular weight polyethylene implants.
abstract: Despite of well-known advantages of high molecular weight polyethylene (Medpor, Synpore) in orbital reconstructions, the thickness of those implants significantly exceeds 0.5 mm and precise modification of thickness is limited. The aim of this study was to present the application of a self-developed method of treatment orbital wall fracture by custom implant made of ultrahigh molecular weight polyethylene (UHMW-PE).
  
  
  METHODS
  First, the test of influence of sterilization process upon implant deformation was performed (autoclaving, ethylene oxide, gas plasma, irradiation). Next, ten cases for delayed surgical treatment of orbital fracture were included into this study (7 males, 3 females). Based on CT scan and mirrored technique, a CAD model of virtual implant for repairing orbital wall was made. Then, an implant was manufactured with a computer numerical controlled milling machine from UHMW-PE block, sterilized and used during a surgical procedure. Clinically used implants had thickness from 0.2 to 4.0 mm.
  
  
  RESULTS
  The best method of sterilization is ethylene oxide process, and the worst is autoclaving. In this series of delayed surgical cases, functional results of orbital surgery are worse than in simpler, early treated cases, but long-term subsidence of diplopia is noticeable [10% poor results]. The results of the treatment depend on the initial level of diplopia where severe initial diplopia to be corrected requires thicker implants (p < 0.01). It also leads to longer surgical procedures (p < 0.01), but prolongation of the surgery had no negative influence upon results of any investigated follow-up examinations. Obviously, the orbital destruction intensity is related to injury-evoked initial diplopia but it also influences whole results of treatment up to 12 months post-op. Interesting result is presented by the relation of maximal implant thickness to 12-month diplopia evaluation. Thicker implants used result in lower residual diplopia (p < 0.05). This is important because of the correlation between the higher orbital destruction intensity with a thicker UHMW-PE implant (p < 0.05) applied in this series.
  
  
  CONCLUSIONS
  Patient-specific ultrahigh molecular weight polyethylene implants enable precise reconstructions of orbital wall. One should not be afraid of a significant eye globe reposition caused by these thickness modulated implants, as such repositioning is essential for an efficient correction of enophthalmos.
authors.affiliation: Department of Maxillofacial Surgery (Head: Marcin Kozakiewicz, DDS, PhD), Medical University of Lodz, Zeromskiego 113, Lodz, Poland. Electronic address: marcin.kozakiewicz@umed.lodz.pl.
authors.forename: Marcin
authors.initials: M
authors.lastname: Kozakiewicz
mesh_terms: D000328:Adult; D001672:Biocompatible Materials / Q000737:chemistry* / Q000528:radiation effects; D017076:Computer-Aided Design; D004172:Diplopia / Q000601:surgery; D004202:Disinfectants / Q000627:therapeutic use; D015841:Enophthalmos / Q000601:surgery; D005027:Ethylene Oxide / Q000627:therapeutic use; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D061330:Multidetector Computed Tomography / Q000379:methods; D061646:Operative Time; D009917:Orbital Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D058626:Plasma Gases / Q000627:therapeutic use; D011095:Polyethylenes / Q000737:chemistry* / Q000528:radiation effects; D011474:Prosthesis Design; D019919:Prosthesis Implantation / Q000379:methods; D019651:Plastic Surgery Procedures / Q000295:instrumentation; D013242:Sterilization / Q000379:methods; D013499:Surface Properties; D014584:User-Computer Interface; D055815:Young Adult
chemical_list: D001672:Biocompatible Materials; D004202:Disinfectants; D058626:Plasma Gases; D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene; D005027:Ethylene Oxide
keywords: CAD; CAM; Orbit; Ultrahigh molecular weight polyethylene