Customized titanium reconstruction of post-traumatic orbital wall defects: a review of 22 cases

Abstract

The authors present the clinical results of their method of customized reconstruction of orbital wall defects using titanium mesh or sheet. High resolution computed tomography (CT) data are imported and processed to create a three-dimensional (3D) image which is used to reconstruct the orbital defect. Mirror imaging of the air in the contralateral maxillary sinus is used to overcome artefact defects in the floor. A stereolithographic model is constructed, from which titanium mesh or sheet is shaped and sized to the required contours for implantation. Twenty-two patients were treated using this technique from 2003 to 2008. Postoperatively 10 patients reported early resolution of their diplopia. Six patients noticed significant improvement of their symptoms with mild residual diplopia in one direction only and at the extremes of gaze at final review. One patient required ocular muscle surgery. Enophthalmos resolved in eight of the nine cases. No patients developed enophthalmos or diplopia as a postoperative complication. The use of titanium mesh for orbital floor reconstruction has been shown to be safe and effective. Customized titanium implants accurately reproduce orbital contours thus restoring orbital volume. This reduces operative time and improves the functional and aesthetic outcomes of post-traumatic orbital reconstruction.

The use of high resolution computed tomography (CT), with the ability to examine the scans routinely in three planes, has provided a better understanding of the three-dimensional (3D) structure of the bony orbit. This combined with the use of rapid prototype models from CT data allows the construction of a more accurate customized implant for post-traumatic reconstruction of orbital wall defects . In this article, a retrospective review of orbital wall fractures treated using customized titanium mesh or sheet implants is described. The authors’ recently described method of virtually reconstructing the orbital floor defect prior to rapid prototype model construction is also briefly discussed .

Materials and methods

Indications for using the technique included severe comminution, large defects with little or no posterior bony support and secondary reconstruction.

Patients were scanned using high resolution CT with a slice thickness of 0.5 mm. The raw CT information obtained was imported in DICOM (Digital Imaging and Communications in Medicine) file format and processed to create a 3D image using Mimics software (Materialise NV, Leuven, Belgium). Despite the ultra-thin CT slices, the orbital floor may, in some areas, be less than 0.5 mm thick . This is too thin to be captured by the scan, resulting in the phenomenon of pseudo-foramina when viewed in 3D format on both the injured and unaffected orbital floors. To overcome this obstacle, the captured air volume of the contralateral maxillary sinus was identified to create a virtual 3D image of that sinus. This modified CT was exported as an STL file into another software package, Freeform ® (SensAble, USA) which allowed intuitive 3D digital manipulation with biofeedback. The position of the mid sagittal plane was then established in order to be able to mirror image the sinus morphology to the defect side ( Fig. 1 ). The superior contour of the 3D sinus volume thus recreates the shape of the orbital floor .

Fig. 1
the process of virtual reconstruction of the orbital floor using the shape and position of the opposite maxillary sinus. (A) Capturing the air in the contralateral maxillary sinus. (B) Establishing a mid-sagittal plane. (C) Mirroring the maxillary sinus onto the defect side. (D) A 3D image with the virtually reconstructed orbital floor.

The resulting virtual model was used to construct a stereolithographic model ( Fig. 2 ) using rapid prototyping. This model was used to enable the shaping of the titanium mesh in the laboratory to the required contours to fit the virtually repaired orbital defect. The pre-shaped titanium mesh was then sent to be sterilized for use in the operating theatre. Alternatively the model was used to make an implant of the desired shape and size using titanium sheet as previously described . This was carried out by taking an impression of the affected orbit on the stereolithographic model with the now reconstructed orbital wall defect. A hard stone plaster model was poured, which was subsequently used to fabricate the customized implant from commercially pure titanium using pressure flasks. Two different titanium thicknesses of 0.25 and 0.5 mm were available, pressed over the cast using 6000 PSI for 24 or 48 h, respectively. The resulting plate was trimmed, smoothed and polished. Multiple venting holes were created in some cases, according to the designing surgeon’s preference, and a flange was extended over the orbital rim to facilitate implant positioning and to prevent it from being displaced posteriorly, with a hole for subsequent screw fixation. The implant was pacified overnight in concentrated nitric acid for decontamination. The final plate was sent for sterilisation to be used in the operating room. The shortest achievable time from the decision to operate to the implant being sterile and ready to use was 4 days with the rate-limiting step being mainly the logistic problems of the construction of the stereolithographic model at another offsite institution.

Fig. 2
(A) Stereolithographic model with the customized titanium plate in position prior to sterilisation. (B) 3D reformatted image of a postoperative CT scan with the titanium plate highlighted.

The two alternative incisions used for access were the mid-eyelid blepharoplasty or the conjunctival incision, depending on operator preference. Where the conjunctival incision was used in the presence of floor and medial defects, a post-caruncular extension was performed to access the medial wall. Orbital dissection was performed in the normal way, exposing and delineating the defect. Herniated orbital contents were retrieved and the plate was inserted and anchored with one or more screws depending on plate design and position. Forced duction testing was performed in all cases and closure was performed after confirming that there was no restriction or tethering of the globe.

A retrospective review of 22 cases treated at the authors’ institution using customized titanium implants for orbital wall reconstruction was carried out. A form was designed for data collection and patients’ case notes were examined, looking at emergency cards, outpatient clinic notes, operating records and correspondence. The collected information was entered into a spreadsheet programme (MS Excel ® , Microsoft USA) for further processing. The results were reviewed and analysed.

Results

Twenty-two patients were treated using this technique between 2003 and 2008 ( Figs 3 and 4 ). A summary of the results is presented in Table 1 . Seventeen patients presented with diplopia, nine of whom also had enophthalmos. Two patients had enophthalmos with hypoglobus but no diplopia. Postoperatively, 10 patients reported early resolution their diplopia. Six patients noticed significant improvement of their symptoms with mild residual diplopia, in one direction only and at the extremes of gaze, at final review. One patient required ocular muscle surgery. Enophthalmos resolved in eight of the nine cases. No patients developed enophthalmos or diplopia as a postoperative complication.

Fig. 3
(A) Preoperative coronal CT scan image demonstrating a left-sided medial orbital wall defect. (B) Postoperative coronal CT scan of the same patient showing the customized titanium plate in position. (C) 3D reformatted postoperative CT scan demonstrating the medial wall titanium plate.

Fig. 4
Extensive orbital floor defect reconstructed with a customized titanium mesh. (A) Sagittal view of the preoperative CT scans showing the unaffected side. (B) Sagittal view of the preoperative CT scans showing the orbital floor defect. (C) Sagittal view of the postoperative CT scans showing the titanium mesh reconstruction of the orbital floor defect.

Table 1
Results of post-traumatic orbital wall reconstruction using customized titanium implants in 22 patients.
Age Sex Diagnosis (site and indication) Aetiology Preop enophthalmos Preop diplopia Time from trauma to surgery in days Incision Implant profile Postop enophthalmos Postop diplopia Complications Follow-up in months
1 23 M Floor comminution with malar fracture Assault Yes Yes 12 Lower blepharoplasty 0.5 mm plate No Resolved 30/7 Scleral show, settled later 16
2 30 M Large floor defect with malar fracture Assault No No 7 Lower blepharoplasty Mesh No No Scleral show 19
3 29 M Floor comminution Sports No Yes 13 Lower blepharoplasty Mesh No Resolved 8/12 None 8
4 18 F Floor and medial wall secondary reconstruction RTA Yes Yes 114 Lower blepharoplasty 0.5 mm plate Resolved Improved Mild residual diplopia 3
5 18 M Large floor defect Assault No yes 31 Conjunctival Mesh No Improved None 2
6 64 M Floor and malar fracture Work-related No No 17 Lower blepharoplasty Mesh No No None 5
7 24 F Large floor defect Assault No Yes 37 Lower blepharoplasty Mesh No Improved None 2
8 27 M Large floor defect Assault No Yes 20 Lower blepharoplasty Mesh No Resolved 1/7 None 3
9 36 M Large floor and medial wall defect RTA Yes with hypoglobus No 62 Lower blepharoplasty 0.5 mm plate Resolved No Ectropion (also had severe lid injuries) 5
10 15 M Large floor defect Sport No Yes 10 Lower blepharoplasty 0.5 mm plate No Resolved 1/7 None 20
11 29 M Large medial wall defect Sport No Yes 34 Lower blepharoplasty and medial ethmoidotomy 0.25 mm plate No Resolved 1/7 Temporary ectropion, resolved 6
12 32 F Floor and medial wall secondary reconstruction RTA Yes with hypoglobus Yes 2 years Lower blepharoplasty 0.5 mm plate Improved Improved Discomfort and palpable plate rim 38
13 44 M Large floor defect Sports Yes Yes 73 Conjunctival 0.25 Resolved Required ocular muscle surgery None 24
14 49 M Large floor and medial wall defect Assault Yes with hypoglobus Yes 253 Conjunctival with lateral canthotomy Mesh Resolved Resolved None 6
15 49 M Large floor and medial wall defect Assault Yes with hypoglobus No 68 Lower blepharoplasty 2 × 0.25 mm plates Resolved No None 10
16 17 M Large floor defect Assault Yes with hypoglobus Yes 164 Conjunctival 0.25 mm plate Resolved Resolved 5 days postop None 8
17 40 M Large floor defect Assault Yes Yes 234 Conjunctival 0.25 mm plate Resolved Resolved Mild right globe elevation, subsequently settled 15
18 30 M Comminution Assault No Yes 27 Lower blepharoplasty 0.25 mm plate No Resolved Deterioration in vision postop, resolved later 5
19 25 M Large floor and medial wall defect Fall No Yes 24 Lower blepharoplasty 0.25 mm plate Resolved No None 6
20 29 M Large floor defect Sports yes Yes 90 Conjunctival 0.25 mm plate Resolved Resolved 7/7 None 3
21 19 M Large floor defect Assault No No 27 Lower blepharoplasty 0.25 mm plate No No None 2
22 32 M Delayed primary reconstruction Assault yes Yes 331 Lower blepharoplasty 0.25 mm plate Improved Improved None 4
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Jan 27, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Customized titanium reconstruction of post-traumatic orbital wall defects: a review of 22 cases
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