Dr Tarjani Dave ( D13684 )
Precis: This study highlights the role of treating implant migration by placing a patient specific second orbital implant to re-center the migrated implant using rapid prototyping and 3D printing in ophthalmic plastic surgery. All 6 patients with inferotemporal implant migration had recentration of the implant over a mean follow up period of 24 months.
Aim: To determine whether a 3D printed patient specific implant (PSI) placed sub-periosteally centers spherical orbital implant post enucleation.
Methods: This is a single-center prospective consecutive interventional case series of 6 patients undergoing 3D printed, patient specific implant, for the correction of a non-porous spherical implant migration. Implant migration was assessed clinically and on patient photographs. Migration was sub-classified either as decentration that did not affect the prosthetic retention, or as displacement that affected the prosthetic retention in the eye socket. The primary outcome measure was centration of the implant clinically and radiologically with ability to retain the prosthesis. The secondary outcome measures were the mean PSI volume, volume of the custom ocular prosthesis (COP) and implant related complications like exposure and extrusion and migration of either implants.
Results: At a mean follow up of 24 months, all six orbital spherical implants remained centered. There were no cases of PSI displacement. The mean PSI implant volume was 3.05 + 0.65 milliliters (ml). There were no cases of implant extrusion, exposure or repeat migration of either implants. The mean COP volume was 2.39 + 0.68 ml. Additional procedures to optimize the aesthetic outcome of the COP were required in 5 patients for this cohort. Simultaneous fornix formation suture was performed in 2 patients, fornix formation with mucus membrane graft in 1 patient, Levator resection in 1 patient and Sulcus filler injection in 1 patient.
Conclusions: This paper describes a novel approach to treat migrated orbital implants post socket surgery. A 3D printing assisted PSI allows recenteration of the migrated implant centrally over a long follow up period of 2 years.
Orbital implant migration following evisceration or enucleation surgery has been observed with porous as well as non-porous implants.1 When the migrated orbital implant affects prosthesis placement and centeration surgical correction of migration is required. Treatment options include implant exchange and dermis fat graft.2,3 Secondary orbital implants have a 25% rate of resurgery of which 13% is attributable to implant migration.3 Dermis fat graft though an option involves a second site scar that may be unacceptable to many patients. In previously operated sockets the rate of graft necrosis is higher.4
3D printing technology along with computer aided design and prototyping is currently being used in the treatment of complex orbital fractures.5 Using these techniques, an individual prototype skull model that resembles the patients orbit can be obtained before surgery.
In the present study we describe a novel, cost effective, minimally invasive technique of designing a patient specific orbital implant using 3D printing of the patients orbit.
Methods:
Study approval, Design and Subjects
This is a single-centre prospective consecutive case series including patients with socket surgery presenting with inability to retain the prosthesis due to implant migration. Institutional Review Board (IRB)/Ethics Committee approval was obtained. All patients presenting to the ophthalmic plastic surgery service or the ocular prosthesis laboratory between January 2014 to December 2016, with the complain of frequent loss of prosthesis form the eye socket were assessed for the presence of infero-temporal implant migration. Migration was classified as decentration and displacement based on our previous work (reference). Six patients had inferotemporal implant displacement with inability to retain the prosthesis and were included in the study. All 6 patients had implant palpable anterior to the inferior orbital rim with consequent shallowing of the inferior fornix. Patients with contracted socket but central implant were excluded. All patients received a PSI custom designed with the aid of 3D printing and rapid prototyping. The cases operated by a one faculty in the service (TVD). All patients had a custom ocular prosthesis (COP) placement at the two months post-operative visit. Additional procedures required either along with the PSI placement or in the follow up period of 2 years were documented.
Outcome measures:
The primary outcome measure was the recentration of the spherical implant migration and the ability to retain the prosthesis. The secondary outcome measures were the mean PSI volume, diameter of the migrated implant, volume of the COP and other post-operative complications.
Data Collection:
The data collected included the demographic details, the indication for surgery and the past ocular procedures, PSI fabrication time, the surgical technique and the surgical steps as detailed in the medical records. Socket examination findings pre-operatively and at the two-month, six-month, I year and 2 year postoperative visit included the (a) examination of the socket with the prosthesis, (b) examination of the socket without the prosthesis and (c) the examination of the prosthesis. The Pre and post-operative CT scan was assessed for centration of the migrated implant, the position of the implant in the orbit along the x,y and z axis. The post-operative complications like recurrent implant migration, exposure and extrusion if present were looked into.
Surgical techniques:
3D printing details:
DICOM images from the computed tomography scan were rendered as 3D models and the region of interest around the orbit was segmented and exported as a binary STL. This was sliced into several 2D layers using proprietary 3D Printing software. To build an accurate 3D model, support structures were generated to provide structural integrity to the model being 3D Printed. Distinct tool paths were generated for the model and the support structures in CMB format, which was then 3D Printed in the Stratasys Fortus 250 mc, an additive manufacturing system that employs Fused Deposition Modeling (FDM). 3D Printing was done at 178-micron layer thickness and with high-density infill to get a rigid model. The model was 3D Printed with Stratasys ABS P430 material and supporting structure was made with Stratasys ABS SR30. Once the 3D Printed model was ready, the support structures were dissolved in an ultrasonic agitation tank resulting in the final orbit model (figure 2A).
Custom implant fabrication:
Using this skull model as a mould, a PMMA implant was fabricated to sit in the basin of the inferior orbital fissure (figure 2B) of this patient to push the migrated implant centrally. The implant was sterilized prior to surgery.
Surgery details:
Through an inferior transconjunctival approach the periosteum was incised just within the orbital margin and reflected to expose the basin of the inferior orbital fissure. The customized orbital PMMA implant was placed subperiosteal, conforming to the pre-designed shape of the floor of the orbit. The recentration of the pre-existing spherical implant was checked for on table by palpating through the palpebral fissure and post-operatively with CT orbit at 6 weeks. Conjunctiva was closed and inferior fornix forming sutures were taken when necessary. Conformer was placed and suture tarsorrhaphy was performed.
Statistical Analysis:
The data were arranged on an excel spreadsheet. Relevant statistical analysis was done using MedCalc version 12.2.1.0. Continuous parametric data were reported as mean (+ standard deviation) and nonparametric data were reported as median with range. Variables between comparative groups were compared using paired t test for parametric distribution and Mann-Whitney U test for non-parametric distribution. A P value of <0.05 was assigned as statistically significant.
Results:
Case 1: This is the pilot case treated by this technique. A 16-year-old male patient presented to us for a tilted and unstable custom ocular prosthesis. On examination, he had a decentred prosthesis with its inferior edge resting on the lower eyelid margin (figure 1A,C). This was resulting in frequent fall of prosthesis from the socket. There was shelving of the inferior fornix with inferotemporal migration of the orbital implant (figure 1B). The implant was palpable anterior to the inferior orbital rim. There was no apparent conjunctival surface loss. Volume loss was evident in terms of the superior sulcus deformity. Computed Tomography scan of the orbit showed an 18 mm orbital implant migrated inferotemporally into the extraconal space (figure 1D). He had undergone three socket surgeries in the past starting with an evisceration with implant for a painful blind eye followed by implant exchange twice for inferotemporal implant migration. Owing to the recurrent inferotemporal implant migration we anticipated fibrosis in the orbit and hence did not consider an implant exchange. The patient denied dermis fat graft due to donor site morbidity. Hence we decided to place a customized implant in the inferotemporal orbit that would push the migrated implant centrally. The surgical steps were as discussed in methods. Six weeks postoperatively, CT scan of the orbit showed the customized orbital implant in place and with intraconal migration of the spherical implant (Figure 3C). A customized ocular prosthesis remained stable and central thereafter till his last follow-up of 2.5 years (figure 3A,B,D).
The average volume and weight of all the other patients operated for PSI’s and the demographics of the other cases are as described in table 1.
|
Sr No |
Eye |
Age/gender |
Prior socket surgery |
Other ocular findings |
Prior attempts at implant centration |
Adjunctive procedures |
Pre existent implant diameter |
PSI implant volume cm3 |
Final COP weight (gms) |
|
1 |
OD |
17/M |
1. Enucleation + Implant 2. Implant exchange 3. Implant exchange |
1. Shallow inferior fornix |
2 |
FFS |
18 |
2.70 |
2.05 |
|
2 |
OD |
47/M |
1. Scleral tear repair 2. Enucleation with implant |
1. LL laxity 2. shallow inf fornix 3. SSD grade IV |
None |
Ptosis correction |
18 |
2.50 |
1.75 |
|
3 |
OD |
25/M |
1. Enucleation + Implant 2. FFS + MMG 3. FFS 4. FFS + MMG |
1. LL laxity 2. Shallow Inf fornix 3. SSD grade IV |
None |
FFS + MMG |
18 |
2.00 |
2.49 |
|
4 |
OD |
21/M |
1. Enucleation + Implant |
1. Shallow inferior fornix 2. Grade II SSD |
None |
FFS |
16 |
3.5 |
1.99 |
|
5 |
OS |
45/F |
1. Enucleation 2. Secondary Implant |
1. Shallow inferior fornix 2. Grade IV SSD |
None |
Filler injection 1cc Superior sulcus |
18 |
3.00 |
3.80 |
|
6 |
OD |
3/M |
1. Enucleation + Implant |
1. Shallow inferior fornix |
None |
None |
18 |
2.30 |
1.90 |
None of the 6 patients developed complications of the spherical or patient specific implant over a mean 24 month follow up. Two patients underwent a simultaneous inferior fornix formation suture for shallow inferior fornix. One patient underwent a subsequent fornix formation suture and mucus membrane graft for grade 1 contracted socket with shallow inferior fornix. One patient required a levator reinsertion for anophthalmic ptosis and one patient had persistent severe superior sulcus deformity for which a hyaluronic gel filter was injected in the superior fornix. The mean pre- operative and post-operative COP weight were 2.86+1.06 and 2.4+0.82 (p=0.4). The mean PSI implant weight was 2.6 cm3. The mean pre and post-operative enophthalmos was 1.8+1.32 mm and 0.6+1.21 mms. The mean pre-operative superior sulcus deformity was grade 2 pre-operatively and grade 0 post-operatively. There was no reduction in the ocular motility post surgery with the patient specific implant.
Discussion:
This study shows that placing a second sub-periosteal implant in the quadrant of migration can center inferotemporal migration of spherical orbital implant following enucleation. This second implant can be custom configured such that it allows exact centration of the spherical implant. The use of 3D printing and rapid prototyping technology allows for the required shape and size configuration of the patient specific implant. This reduced the chances of further implant complications such as migration, exposure and extrusion. To the best of our knowledge this is a novel application of 3D printing technology in ophthalmic plastic surgery with promising results.
Non-porous implants suffer a higher rate of implant migration compared to their porous counterparts especially in the setting of enucleation.6,7 However in the absence of pegging, a porous implant does not provide additional motility compared to a non-porous implant.8-10 Hence several surveys have shown that a significant proportion of surgeons prefer to place a non-porous implant following socket surgery.9,10 While the non-porous implant offers an excellent and comparable outcome to its porous counterpart, one of the important disadvantages is implant migration since it is devoid of fibrovascular tissue ingrowth into the implant.11
Implant migration has been poorly studied in literature. In our opinion the cause of implant migration seems to be orbital fibrosis or disturbances in the Koornneef’s septa that are present between the extraocular muscles and divide the orbit into its extra and intraconal spaces.12-19 Once these septa are disturbed or damaged during socket surgery the chances that an implant may migrate increase. This is specifically true in case of enucleation where there is more disturbance of the orbital anatomy versus evisceration. All the 6 patients in our series suffered implant migration following enucleation.
With this background knowledge, that it’s the orbital fibrosis and disturbance in the orbital anatomy that increases the risk of non-porous implant migration, it is most certain that an implant exchange with non-porous implant will not help in re-centering a migrated spherical orbital implant. The use of a porous implant for implant exchange may be an alternative, however a theoretical risk of the porous implant remaining migrated exists since we have established that it’s the orbital fibrosis that is responsible for migration of the implant. Also the cost of a porous implant is approximately $200 vs that of a non-porous implant which is $ 20-25.20 This leaves us with the option of dermis fat graft for volume augmentation in patients with a migrated spherical non-porous implant. However the requirement for a second site incision and the higher rate of graft necrosis in repeat socket surgeries makes this procedure an unattractive choice.21,22
3D printing and rapid prototyping has been used in ophthalmic plastic surgery for the correction of complies orbito-zygomatic fractures and in creation of patient specific implants for volume augmentation in the orbit.23,24 3D printing and computer-assisted techniques allow for the creation of the patients orbit in vitro and this serves as a mould for fabrication of the patient specific implant. With the use of freely available softwares such as MIMICS, it is possible to compute the PSI and directly print the implant using the readily available, inexpensive, range of materials in plastic that can be 3D printed. This implant can then be converted to a PMMA model using the same techniques as those of fabricating a custom ocular prosthesis.
The limitations of this study include, lack of histo-pathological documentation of fibrosis in the orbit as a cause for implant migration, a smaller patient cohort and a relatively shorter duration of follow up. The cost effectiveness of the treatment has been calculated by taking into account only the cost of 3D printing and not the additional cost of fabrication of the PSI implant. However since we used PMMA for the fabrication of the PSI, it still remains an inexpensive alternative. The procedure does involve placement of a second implant in the orbit and this increases the risk of implant related complications. The mean follow-up duration of 24 months may be a limitation, however no complication related to both the implants were seen over this follow up duration. We do recommend a longer follow up of these cases.
Conclusion:
Patient specific orbital implant fabrication using 3D printing and additive manufacturing offers a novel and cost-effective way to centre orbital implants in patients with recurrent implant migration. This is especially true for patients who have associated volume loss. Pre-operative 3D Printing enables us to determine the exact shape and size of the patient specific implant.
Acknowledgements:
1. Hyderabad Eye Research Foundation
2. Dr Vivek Dave and Dr. Sayan Basu for providing assistance with the manuscript preparation
Competing interests: none
Funding: This study was funded by the Hyderabad Eye Research Foundation.
References:
1. Custer PL, Kennedy RH, Woog JJ, et al. Orbital implants in enucleation surgery: A report by the American Academy of Ophthalmology. Ophthalmology 2003;110(10);2054-61.
2. Quaranta-Leoni FM, Moretti C, Sposato S, et al. Management of porous orbital implants requiring explantation: a clinical and histopathological study. Ophthal Plast Reconstr Surg 2014;30:132–6.
3. Sundelin KC, Dafgard Kopp EM. Complications associated with secondary orbital implantations Acta Ophthalmol 2015:93:679–683.
4. Nentwich MM, Schebitz-Walter K, Hirneiss C, et al. Dermis fat grafts as
primary and secondary orbital implants. Orbit 2014 Feb;33:33-8.
5. Baumann A, Sinko K, Dorner G. Late Reconstruction of the Orbit With Patient-Specific Implants Using Computer-Aided Planning and Navigation. J Oral Maxillofac Surg 2015;73:S101-S106.
6. Migliori ME. Enucleation versus evisceration. Curr Opin Ophthalmol 2002;13:298 –302.
7. Custer PL. Enucleation: past, present and future. Ophthal Plas Recostr Surg 2000;16:316 –21.
8. Tari AS, Malihi M, Kasaee A, Tabatabaie SZ, Hamzedust K, Musavi MF, et al. Enucleation with hydroxyapatite implantation versus evisceration plus scleral quadrisection and alloplastic implantation. Ophthal Plast Reconstr Surg 2009Mar-Apr;25(2):130-3.
9. Su GW, Yen MT. Current trends in managing the anophthalmic socket after primary enucleation and evisceration. Ophthal Plast Reconstr Surg 2004
Jul;20(4):274-80.
10. Viswanathan P, Sagoo MS, Olver JM. UK national survey of enucleation,
evisceration and orbital implant trends. Br J Ophthalmol 2007 May;91(5):616-9.
11.
12. Ettl AR, Salomonowitz E, Koornneef L. Magnetic resonance imaging of the orbit: Basic principles and anatomy. Orbit. 2000 Dec;19(4):211-237.
13. Ettl A, Koornneef L, Daxer A, Kramer J. High-resolution magnetic resonance imaging of the orbital connective tissue system. Ophthal Plast Reconstr Surg. 1998 Sep;14(5):323-7.
14. Ettl A, Kramer J, Daxer A, Koornneef L. High-resolution magnetic resonance imaging of the normal extraocular musculature. Eye (Lond). 1997;11 ( Pt 6):793-7.
15. Ettl A, Priglinger S, Kramer J, Koornneef L. Functional anatomy of the levator palpebrae superioris muscle and its connective tissue system. Br J Ophthalmol. 1996 Aug;80(8):702-7.
16. Koornneef L. Orbital septa: anatomy and function. Ophthalmology. 1979 May;86(5):876-80.
17. Koornneef L. New insights in the human orbital connective tissue. Result of a new anatomical approach. Arch Ophthalmol. 1977 Jul;95(7):1269-73.
18. Koornneef L. Details of the orbital connective tissue system in the adult. Acta Morphol Neerl Scand. 1977 Feb;15(1):1-34.
19. Koornneef L. The development of the connective tissue in the human orbit. Acta Morphol Neerl Scand. 1976 Dec;14(4):263-90.
20. Ho VWM, Hussain RN, Czanner G, Sen J, Heimann H, Damato BE. Porous Versus Nonporous Orbital Implants After Enucleation for Uveal Melanoma: A Randomized Study. Ophthal Plast Reconstr Surg. 2017 Nov/Dec;33(6):452-458.
21. Nentwich MM, Schebitz-Walter K, Hirneiss C, Hintschich C. Dermis fat grafts as primary and secondary orbital implants. Orbit. 2014 Feb;33(1):33-8.
22. Bosniak SL. Complications of dermis-fat orbital implantation. Adv Ophthalmic Plast Reconstr Surg. 1990;8:170-81.
23. Callahan AB, Campbell AA, Petris C, Kazim M. Low-Cost 3D Printing Orbital Implant Templates in Secondary Orbital Reconstructions. Ophthal Plast Reconstr Surg. 2017 Sep/Oct;33(5):376-380.
24. Scawn RL, Foster A, Lee BW, Kikkawa DO, Korn BS. Customised 3D Printing: An Innovative Training Tool for the Next Generation of Orbital Surgeons. Orbit. 2015;34(4):216-9.
Figure Legends:
Figure 1: Pre-operative examination details. 1A: right decentered prosthesis with superior sulcus deformity, 1B: inferotemporal migration of implant highlighted with * and shelving of the lower fornix, 1C: Inferior edge of the prosthesis resting on the lower eyelid margin with increased inferior scleral show, 1D: CT orbit in the coronal plane showing inferotemoral spherical orbital implant migration
Figure 2: Skull models in soft copy and 3D. 2A: skull model built in 3D using DICOM images of the patients CT orbit, 2B: skull model printed in plastic and used as a mould to fabricate an orbital implant from PMMA.
Figure 3: Comparison of pre and post-operative result. 3A: pre-operative standard view photograph of the patient with superior sulcus deformity and decentred ocular prosthesis, 3B: post-operative standard view photograph of the patient with correction of the superior sulcus deformity and a better fitting ocular prosthesis. 3C: pre-operative CT orbit of the patient showing an inferotemoral migrated spherical orbital implant. 3D: post-operative CT showing a patient specific implant pushing the spherical implant towards the central intraconal space.
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