Comparison of pre-bent titanium mesh versus polyethylene implants in patient specific orbital reconstructions

Abstract

Introduction: Computerized tomography DICOM file can be relatively easily transformed to a virtual 3D model. With the help of additional software we are able to create the mirrored model of an undamaged orbit and on this basis produce an individual implant for the patient Authors decided to apply implants with any thickness, which are authors own invention to obtain volumetric support and more stable orbital wall reconstruction outcome. Material of choice was ultra-high molecular weight polyethylene (UHMWPE).

Objective: The aim of this study was to present and compare functional results of individual reconstructions of orbital wall using either titanium mesh or ultra-high molecular weight polyethylene.

Materials and methods: 57 consecutive patients affected by orbital wall fracture (46 males, 11 females, mean age 34±14 year) were treated in Department of Maxillofacial Surgery from 2010 to 2012. In the first group we used patient specific treatment by titanium mesh shaped on a 3D printed model of a mirrored intact orbit (37 orbits) or by individually manufactured UHMW-PE implantby CAM milling in second group (20 orbits). All of these patients were subjected to preoperative helical computerized tomography and consultation of an ophthalmologist (including binocular single vision loss test - BSVL). Further on, patients were operated under general anaesthesia using transconjuctival approach. BSVL was again evaluated post-operationally in 1 month and 6 months later.

Results: Functional treatment results (BSVL) for both groups were similar in 1 month as well as 6 months post operational time. There was no statistically significant difference between these two groups.

Conclusions: This study of 6 months functional result assessment of pre-bent individual implants and CNC milled ultra-high molecular weight polyethylene of the orbital wall has shown it to be a predictable reconstruction method. Individually shaped UHMWPE seems to be as good as pre-bent titanium mesh.

Figure 1

Blow-out fracture of the left orbit floor. A - coronal view in computerized tomography. B - sagittal view through left orbit. Bone fragments displacement and herniated orbital tissues shown by arrows.

Figure 2

Results of treatment. A – computerized tomography in sagittal view: titanium mesh deformated during intra-orbital maneuvres in primary surgery (asterisk); its deepest located part hurts the inferior rectus muscle. B – downgaze significantly limited in the left eye; C – result of binocular single vision loss test: diplopia caused by titanium mesh is mainly up- and downgaze. D - computerized tomography in sagittal view after corrective surgery and exchange of the implant to stiff patient specific ultra-high molecular weight polyethylene implant: orbital floor is reconstructed (arrow) and inferior rectus muscle is free. E – normal eye globe motility: full downgaze 1 month post-operationally. F - result of binocular single vision loss test: residual diplopia in upgaze/left.

Figure 3

Surgical steps in exchange titanium mesh to individual ultra-high molecular weight polyethylene implant. A – transconjunctival approach exposes the titanium mesh immerse in scar tissue in orbital floor. Orbital spatula holding the globe in the upper section, hooks holding the eylid in the lower part of the picture. B – mesh impressions in orbital floor scar tissue. C – individual polyethylene implant insertion through the transconjunctival approach. D – implant position in the orbit, implant alignment checked in previously designed reference areas, here visible fit of the implant to lower orbital rim. Implant position fixed with single 6mm long self-tapping screw from MatrixMIDFACE system by SYNTHES (Synthes, Zuchwil, Switzerland).

Figure 4

Plot comparison of ODI scale [[15]] of orbital injury and material used for orbital walls reconstruction. Although patients were assigned to both groups randomly there was a statistically significant difference between those two groups. Patients treated with ultra-high molecular weight polyethylene suffered from more extensive fractures than those treated with pre-bent titanium mesh. ODI scale [15] is described as follows: 1. site of destruction: floor i.e. one wall (1W); 2. floor+one wall (medial or lateral) i.e. two walls (2W); 3. floor+one margin i.e. one wall and one orbital margin (1W+1M);4. floor+one wall+one margin i.e. 2W+1M; 5. floor+one wall+two margins i.e. 2W+2M; 6. floor+two walls+one margin i.e. 3W+1M; 7. floor+one or two walls+two margins i.e. 3W+2M; 8. floor+two or three walls+more than one margin i.e. 3-4W+2-4M.

Figure 5

Comparison of treatment results in percentage of field of vision affected with loss of single vision (BSVL) for ultra-high molecular weight polyethylene and pre-bent titanium mesh. Examination was performed preoperatively, 1 month postoperatively and 6 months postoperatively. Despite differences in scale of injury in both groups (Figure 4) there was no statistically important difference in treatment results between patients treated with pre-bent titanium mesh or individually shaped CNC milled UHMW-PE implants.

Figure 6

Plot comparison of percentage of field of vision affected with loss of single vision (BSVL) pre- and 6 months postoperatively in accordance to patients’ gender. There was no statistically important difference in treatment results between genders.