The Application Research Of Treatment On Old Post-traumatic Enophthalmos Based On Three-dimensional Digital Technology

Objective1. To set up a database of orbital parameters of normal Chinese subjects using a three-dimensional reconstruction method to determine criteria for treatment of orbital deformities and provide the reference basis for the diagnosis, preoperative planning and evaluating prognosis of post-traumatic enophthalmos especially.2. To explore a simple and convenient method for preoperative planning and intraoperative guidance of post-traumatic enophthalmos with Medpor implant based on three-dimensional digital technology to achieve individual correction and advancement of accuracy and safety for surgical treatment.3. To establish three-dimensional finite element model of the repairing for orbital defect with Medpor implant, and to explore biomechanical characteristics including displacement and stress analysis of Medpor implant with the state of implantation in orbital floor to provide the reference basis for surgeons.Methods1. CT data of 102 normal people from August 2011 to December 2015 were collected. Then summarized the anatomic parameters by measurement through follow steps:CT data acquisition, three-dimensional reconstruction, selection of anatomical landmark points and statistical induction. And discrepancy analysis of orbital parameters between men and women was done.2. CT data of 15 patients of old post-traumatic enophthalmos who has been received surgical correction were collected. All was divided into two groups numbered A and B. Group A included patients who was received individual Medpor implantation, group B included patients who was received non-individual Medpor implantation. Evaluation of prognostic indexes of the two different groups was done. Discrepancy analysis between them was done by SPSS.3. Three-dimensional finite element model of the repairing for orbital defect with Medpor implant was modeled and then displacement and stress analysis of Medpor implant was done by finite element method.Results1. The morphologic parameters of normal Chinese orbit were measured on 3D models using three-dimensional digital technology. In men and women, respectively, mean orbital width 39.91 and 38.87 mm, mean orbital height 33.72 and 33.58 mm, mean medial orbital wall length 46.15 and 45.50 mm, mean lateral orbital wall length 47.89 and 47.73 mm, mean orbital floor length 47.79 and 46.77 mm, mean orbital roof length 52.65 and 51.77 mm, mean intraorbital distance 27.04 and 25.33 mm, mean extra-orbital distance 96.95 and 93.37 mm, mean orbital rim perimeter 127.05 and 122.07mm, mean bony orbital volume was 26.06 and 24.323 mL. There were significant differences between men and women in 70% of anatomic parameters. Minor differences (<0.5mm) between the two orbits were found but being considered no influence on the orbital symmetry.2. There were significant differences between group A and group B in orbital bony volume and eye ball protrusion of affected side. The variation of orbital bony volume and eye ball protrusion of affected side in group A was higher than group B, which showed the method of group A was superior to group B. There was positive positive correlation between orbital bony volume variation and eye ball protrusion variation.3. The finite element was established in this study succesfully. No fixation between Medpor impant and orbital wall allows large displacement and no stress. Fixation by one screw or two screws has the same stress value.Conclusions1. A database of normal Chinese morphologic parameters of orbit was developed based on a three-dimensional reconstruction method. The findings provide parameters for preoperative planning and prediction of postoperative outcome.2. It is concluded that 3D digital reconstruction method could be applied in individual correction of old post-traumatic enophthalmos. The treatment effect of individual Medpor implantation in group A was superior to group B. And it is shown that prognostic indexes of post-traumatic correction can be quantitative by 3D digital technique. A conclusion was drawn that there is a linear relation between the volume of implants and eye protrusion.3. Three-dimensional finite element model of the repairing for orbital defect with Medpor implant was established firstly. Although objective results of FEA can be referenced, operator should make a choice on the basis of intraoperative situations and individual experience.