Graefes Arch Clin Exp Ophthalmol DOI 10.1007/s00417-015-3055-6
CORNEA
Bone augmentation of the osteo-odonto alveolar lamina in MOOKP—will it delay laminar resorption? Geetha Iyer 1 & Bhaskar Srinivasan 1 & Shweta Agarwal 1 & Ekta Rishi 1 & Pukhraj Rishi 1 & Gunaseelan Rajan 2 & Shanmugasundaram Shanmugasundaram 2,3
Received: 11 March 2015 / Revised: 4 May 2015 / Accepted: 6 May 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract Purpose We aimed to describe a new technique and analyse the early outcomes of augmenting the canine tooth using a mandibular bone graft in an attempt to delay or retard the process of laminar resorption following the modified osteo odonto keratoprosthesis (MOOKP) procedure. Design This was a retrospective case series. Patients and methods Eyes that underwent the bone augmentation procedure between December 2012 and February 2014 were retrospectively analysed. The procedure, performed by the oromaxillofacial surgeon, involved securing a mandibular bone graft beneath the periosteum on the labial aspect of the canine tooth chosen to be harvested for the MOOKP procedure. This procedure was performed simultaneously with the Stage 1 A of the MOOKP. Three months later, the tooth was harvested and fashioned into the osteo-odonto alveolar lamina similar to the method described in the Rome–Vienna Protocol. Results The bone augmentation procedure was performed in 11 eyes (five SJS/ six chemical injuries). The mean follow-up after Stage 2 of MOOKP procedure in these eyes was 7.45 months (2 to 20 months). Complications noted were peripheral laminar exposure (three eyes—SJS) and bone graft
* Geetha Iyer [email protected] 1
CJ Shah Cornea Services/Dr G Sitalakshmi Memorial Clinic for Ocular Surface Disorders, Medical Research Foundation, Sankara Nethralaya, 18 College Road, Chennai 600006, Tamil Nadu, India
2
Rajan Dental Institute, 56, Dr RadhakrishnanSalai, Mylapore, Chennai 600004, Tamil Nadu, India
3
Department of Oral & Maxillofacial Surgery, SRM Dental College, Bharathi Salai, Ramapuram, Chennai 600089, Tamil Nadu, India
exposure and necrosis in the mouth (nine—SJS). No evidence of clinical laminar resorption was noted in any of the eyes. Conclusion Laminar resorption in MOOKP can lead to vision and globe threatening complications due to the consequent cylinder instability and chances of extrusion. Augmenting the bone on the labial aspect of the canine tooth might have a role to play in delaying or preventing laminar resorption. Keywords Keratoprosthesis . Modified osteo odonto keratoprosthesis . Stevens Johnson syndrome . Ocular chemical injuries . Bone grafting
Introduction Laminar resorption has emerged as a cause for concern following the MOOKP procedure for end-stage ocular surface disorders. Resorption rates have been noted to range between 0 and 28 % in previous studies [1, 2]. Resorption can be detected early by radiological imaging [3, 4] as well as clinically. In extreme cases of severe resorption, patients can present with extrusion of the cylinder or endophthalmitis. In our series of 85 eyes, we noted our resorption rate to be 22.98 % [5]. In this published report on laminar resorption in our series of MOOKP, the mean duration to the first sign suggestive of resorption among patients of SJS was 36.7 months (13 to 60 months), and among patients of chemical injury it was 43 months (28 to 66 months). Though there were earlier reports regarding laminar resorption and means to identify the same by radiological means, there existed no grading system for or means to address resorption. In another recent paper, we proposed a grading system for laminar resorption, along with management options appropriate to the grade [6]. We noted that resorption occurred more commonly on the labial aspect of the lamina with pre-existing
Graefes Arch Clin Exp Ophthalmol
thin bone in comparison to the palatal bone. We also described the successful use of bone morphogenetic protein to salvage laminae with moderate to severe resorption, not threatening cylinder integrity. Herein, we describe the technique and outcome of augmenting the labial aspect of the canine tooth with a mandibular graft prior to harvesting the same for laminar fashioning, in an attempt to delay or prevent the process of laminar resorption in MOOKP procedure.
Patients and methods Institutional Review Board approval was obtained for this study, which adhered to the tenets of the Declaration of Helsinki. Eleven patients in whom the MOOKP procedure was performed between December 2012 to February 2014, underwent the bone augmentation procedure. Informed consent was obtained from all the patients. The procedure was performed by the oromaxillofacial surgeon, along with Stage 1 A of the MOOKP surgery. The procedure was performed under general anesthesia.
Technique of bone augmentation Donor site A bilateral mental nerve block and lingual nerve infiltration with 2 % lignocaine and adrenaline 1:1,00,000 was given in relation to teeth 33–43. A vestibular incision was placed in relation to 43–33 regions and the mucoperiosteal flap was raised. The mental nerve was isolated and protected. A sagittal saw was used for the osteotomy in the chin region. The vertical osteotomy measuring 1 cm lateral to the midline and horizontal osteotomy measuring 1.5 cm in length was placed 5 mm beneath the lower anterior teeth, and was connected by a vertical osteotomy 5 mm medial to the mental nerve measuring 1 cm in length. The two vertical osteotomies were connected inferiorly by a horizontal osteotomy measuring 1.5 cm. Thin spatula osteotomes were used to complete the osteotomy. A bone graft measuring 1.5×1 cm was removed as a block graft from the chin and cancellous bone was also harvested from the deeper aspect. Hemostasis was achieved using bone wax and gelfoam. The wound was closed in layers with 3–0 vicryl. Recipient site The recipient site (right canine or left canine) in the maxilla was infiltrated buccally and palatally with 2 % lignocaine and adrenaline 1:1,00,000. A triangular flap was raised by placing
a crevicular incision around the lateral incisor, canine and first premolar, and a vertical incision was made anterior to the lateral incisor. A mucoperiosteal flap was raised and multiple burr holes were made around the canine with a 1-mm drill to induce bleeding from the outer cortex of the maxilla. The block bone was placed buccally over the canine root region and fixed with a 1.2 mm titanium micro-screw measuring 12 mm in length. Cancellous bone was placed around the block bone and a horizontal relieving incision was placed over the periosteum part of the flap to allow tension-free wound closure. The wound was closed with 3–0 vicryl. A diagrammatic representation of the technique is illustrated in Fig. 1a–d. Postoperative regimen An external dressing applied along the jaw line was removed after 2 days. The patient was administered systemic antibiotic–augmentin and metronidazole for a week, along with chlorhexidine mouthwash for 2 weeks. The ocular medications included topical antibiotics and lubricants, along with systemic acetazolamide if indicated. The harvesting of the augmented tooth is performed 3 months after the bone augmentation procedure. The surgical steps are similar to those described earlier as well as in the Rome-Vienna Protocol, the only difference being removal of the titanium screw after removal of the tooth. The augmented osteo-odonto alveolar lamina is placed in the contralateral subcutaneous cheek pocket for it to develop its fibrovascular covering. Three months later, the lamina is placed in the eye during Stage 2 of the MOOKP procedure.
Results Eleven eyes of 11 patients underwent the bone augmentation procedure prior to the MOOKP surgery at our center between December 2012 and February 2014. The age of the patients ranged from 20 to 40 years (mean age 28.18 years). Of these 11, nine were males and two were females. The primary etiology was Stevens Johnson syndrome in five eyes and chemical injury in six eyes. The mean follow-up after Stage 2 of MOOKP procedure in these eyes was 7.45 months (2 to 20 months). There were no intraoperative complications of the procedure. Postoperatively, the bone graft necrosed in one patient of SJS secondary to exposure due to retraction of the mucosal flap. This was in a patient that has had the MOOKP procedure done for the other eye at our center with loss of lamina to resorption after having maintained a best corrected visual acuity of 20/20 for almost 3 years. In three eyes, there was noted to be peripheral laminar exposure, which required being covered by a tarsoconjunctival pedicle flap.
Graefes Arch Clin Exp Ophthalmol
Fig. 1 a Bone graft harvested from the mandibular bone after lifting the mucoperiosteum. b Graft secured in place over the root of the chosen maxillary canine using a titanium screw. c The mucoperiosteal flap over
the graft, freed to the extent possible using relaxing incisions. d The mucoperiosteal flap secured over the grafted bone at the end of surgery
The laminar dimensions have been noted in Table 1 along with the other patient details.
Since the resorption in our earlier series was always noted to occur along the labial aspect of the tooth, which corresponded to the side with thinner bone support in comparison to the palatal aspect, the authors decided to attempt to increase the bone thickness on the labial aspect by means of bone grafting. Cortical bone grafts have by themselves been harvested and used as a carrier for the optical cylinder, though the resorption rates have been noted to be shorter in comparison to the osteo-odonto alveolar lamina [11]. Various donor sites throughout the skeleton have been investigated and described for bone harvest. Local grafts from the oral and facial region offer a convenient source of bone and have revealed several benefits in the repair of alveolar defects [12]. Mandibular bone grafts, which are primarily cortical bone, exhibit little volume loss and show excellent incorporation at short healing times. Another obvious advantage of local grafts is that donor and recipient sites are in the same
Discussion Most of the patients undergoing MOOKP surgery are young adults. Following the procedure, they get back to a relatively normal life to complete their education and or work. The procedure by itself is a demanding and time consuming one, and takes up to 4–6 months towards completion of all stages. The results of the procedure are encouraging, especially given the good long-term retention of the prosthesis in these eyes [1, 7–10]. One of the issues unique to the MOOKP procedure that threatens the longevity of the lamina is resorption of the lamina [1–5]. Table 1
Details of patients who underwent bone augmentation prior to MOOKP procedure
Serial no
Age (years)
Sex
Etiology
1 2 3 4
40 28 24 21
F M M M
Chemical Chemical Chemical SJS
5 6 7
20 32 35
M M M
8 9 10 11
39 26 26 19
M F M M
Follow-up after stage 2 (months)
BCVA
Lamina dimensions (mm)
4 3 4 2
20/50 20/80 20/20 20/25
12.9×11.5×3.4 14.9×12.1×3.2 13.6×12×3.3 14.95×12.8×3.48
SJS Chemical SJS
12 5 11
20/50 20/30 20/50
13.1×11.9×3.3 13.9×12×3 13.6×11.4×3.5
SJS SJS Chemical SJS
9 0 20 12
20/30
12×10×3.5
CF@2 m 20/20
15.73×12.25×4.0 14.9×13×3.5
Comments
peripheral laminar exposure treated with tarsoconjunctival pedicle flap amblyopic peripheral laminar exposure treated with tarsoconjunctival pedicle flap Bone graft necrosis Optic disc pallor Exposed avascular lamina removed and replaced in subcutaneous pouch—awaiting restage 2
MOOKP modified osteo-odonto keratoprosthesis, BCVA best corrected visual acuity, mm millimeters, SJS Stevens Johnson Syndrome, CF@2 m counting fingers at 2 m
Graefes Arch Clin Exp Ophthalmol
Fig. 2 a Non-augmented osteo-odonto alveolar lamina showing less bone on the labial aspect (indicated by the red arrow). b Augmented osteo-odonto lamina showing more bone on the labial aspect in
comparison to non-augmented lamina (indicated by the red arrow) (dentine aspect). c Augmented lamina showing a centrally placed optical cylinder on the reverse (bone) aspect
operating field, so surgical and anesthesia times are reduced. In addition, these areas may offer a decreased morbidity from graft harvest compared to extraoral donor sites [12]. A plate of mandibular cortical bone 3–4 mm in thickness was added beneath the periosteum of the chosen maxillary canine and secured in place using a titanium screw. The grafted bone was covered by the periosteum and the gingival mucosa. A period of 3 months was allowed for the grafted bone to integrate with the maxillary bone. The length of the grafted bone was longer than the intended length of the tooth harvested (usually 15 mm from the neck of the canine tooth), so as to avoiding interference of the titanium screw in the future lamina. The width of the bone was also wider than the width of the root of the canine so as to straddle minimally over both the adjacent teeth. This added girth to the root following the bone graft slightly increased the effort of harvesting the tooth. The additional bone graft was noted to increase the bone support on the labial aspect of the lamina comparable to that on the palatal aspect (Fig. 2a–c). However, it led to an increase in the width of the lamina, making it larger than the nonaugmented laminae. We anticipated the need for a larger mucosal graft to cover the larger lamina, and hence used a 3.5 cm graft instead of the regular 3 cm graft. Despite this, peripheral laminar exposure secondary to a bulky lamina was noted in three eyes belonging to SJS group, of which two were corrected by means of a tarsal pedicle flap. In one eye, the lamina had to be removed from the eye and replaced back in the subcutaneous pouch due to a large area of exposed avascular lamina. SJS eyes undergoing the MOOKP procedure have been noted to have issues of laminar exposure requiring mucosal revision surgeries, and we had earlier attributed the same to prior mucosal insult that occurs in this group making the mucosa in SJS patients more susceptible to erosion and necrosis [5]. Whether the exposures in the augmented laminae were due to a similar cause, or due to the increased bulk and therefore a mechanical stretch on the mucosa causing its necrosis and lamina exposure, is uncertain. It is however noteworthy that none of the augmented laminae in patients of chemical injuries had a similar laminar exposure.
Combining the bone augmentation with the Stage 1 A of the MOOKP had the advantage of preventing the need for a separate procedure, and therefore exposure to multiple general anesthesia. However, the surgical time increased by an hour and there was the need for the presence of the oromaxillofacial surgeon and the coordination therewith. The duration to the next stage of the procedure also increased to 3 months instead of the usual 1 month, thereby increasing the entire duration of the MOOKP procedure to a minimum of 6 months. The obvious shortcoming of the study is the limited followup period. However, a minimum follow-up period of 4–5 years would be required for proof of the concept, the approximate time period of presentation of patients with issues related to laminar resorption. Considering that the long-term results of MOOKP are by comparison better than the currently used keratoprosthesis for end-stage ocular surface diseases and laminar resorption has been noted across most published series, with no permanent curative or preventive modalities available as of now, the authors are of the opinion and hope that the process of augmenting the tooth using a bone graft could provide a means to delaying or preventing laminar resorption in these eyes.
Conflict of interest All authors certify that they have NO affiliation with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.
References 1.
2.
Tan A, Tan DT, Tan XW, Mehta JS (2012) Osteo-odonto keratoprosthesis: systematic review of surgical outcomes and complication rates. Ocul Surf 10(1):15–25 Stoiber J, Csáky D, Schedle A, Ruckhofer J, Grabner G (2002) Histopathologic findings in explanted osteoodontokeratoprosthesis. Cornea 21(4):400–404
Graefes Arch Clin Exp Ophthalmol 3.
4.
5.
6.
7.
Sipkova Z, Lam FC, Francis I, Herold J, Liu C (2013) Serial 3dimensional computed tomography and a novel method of volumetric analysis for the evaluation of the osteo-odonto-keratoprosthesis. Cornea 32(4):401–406 Stoiber J, Forstner R, Csáky D, Ruckhofer J, Grabner G (2003) Evaluation of bone reduction in osteo-odontokeratoprosthesis (OOKP) by three-dimensional computed tomography. Cornea 22(2):126–130 Iyer G, Srinivasan B, Agarwal S, Rachapalle SR (2014) Laminar resorption in modified osteo-odonto-keratoprosthesis procedure: a cause for concern. Am J Ophthalmol 158(2):263–269 Iyer G, Srinivasan B, Agarwal S, Shanmugasundaram S, Rajan G (2014) Structural & functional rehabilitation in eyes with lamina resorption following MOOKP–can the lamina be salvaged? Graefes Arch Clin Exp Ophthalmol 252(5):781–790 Falcinelli G, Falsini B, Taloni M et al (2005) Modified osteoodontokeratoprosthesis for treatment of corneal blindness: longtermanatomical and functional outcomes in 181 cases. Arch Ophthalmol 123:1319–1329
8.
Hille K, Grabner G, Liu C, Colliardo P, Falcinelli G, Taloni M, Falcinelli G (2005) Standards for modified osteoodontokeratoprosthesis (OOKP) surgery according to Strampelli and Falcinelli: the Rome-Vienna Protocol. Cornea 24(8):895–908 9. Iyer G, Pillai VS, Srinivasan B et al (2010) Modified osteo-odonto keratoprosthesis - the Indian experience - results of the first 50 cases. Cornea 29:771–776 10. Liu C, Okera S, Tandon R et al (2008) Visual rehabilitation in endstage inflammatory ocular surface disease with the osteoodontokeratoprosthesis: results from the UK. Br J Ophthalmol 92: 1211–1217 11. De La Paz MF, De Toledo JA, Charoenrook V et al (2011) Impact of clinical factors on the long-term functional and anatomic outcomes of osteoodonto- keratoprosthesis and tibial bone keratoprosthesis. Am J Ophthalmol 151:829– 839 12. Misch CM (2000) Use of the mandibular ramus as a donor site for onlay bone grafting. J Oral Implantol 26(1):42–49
CORNEA
Bone augmentation of the osteo-odonto alveolar lamina in MOOKP—will it delay laminar resorption? Geetha Iyer 1 & Bhaskar Srinivasan 1 & Shweta Agarwal 1 & Ekta Rishi 1 & Pukhraj Rishi 1 & Gunaseelan Rajan 2 & Shanmugasundaram Shanmugasundaram 2,3
Received: 11 March 2015 / Revised: 4 May 2015 / Accepted: 6 May 2015 # Springer-Verlag Berlin Heidelberg 2015
Abstract Purpose We aimed to describe a new technique and analyse the early outcomes of augmenting the canine tooth using a mandibular bone graft in an attempt to delay or retard the process of laminar resorption following the modified osteo odonto keratoprosthesis (MOOKP) procedure. Design This was a retrospective case series. Patients and methods Eyes that underwent the bone augmentation procedure between December 2012 and February 2014 were retrospectively analysed. The procedure, performed by the oromaxillofacial surgeon, involved securing a mandibular bone graft beneath the periosteum on the labial aspect of the canine tooth chosen to be harvested for the MOOKP procedure. This procedure was performed simultaneously with the Stage 1 A of the MOOKP. Three months later, the tooth was harvested and fashioned into the osteo-odonto alveolar lamina similar to the method described in the Rome–Vienna Protocol. Results The bone augmentation procedure was performed in 11 eyes (five SJS/ six chemical injuries). The mean follow-up after Stage 2 of MOOKP procedure in these eyes was 7.45 months (2 to 20 months). Complications noted were peripheral laminar exposure (three eyes—SJS) and bone graft
* Geetha Iyer [email protected] 1
CJ Shah Cornea Services/Dr G Sitalakshmi Memorial Clinic for Ocular Surface Disorders, Medical Research Foundation, Sankara Nethralaya, 18 College Road, Chennai 600006, Tamil Nadu, India
2
Rajan Dental Institute, 56, Dr RadhakrishnanSalai, Mylapore, Chennai 600004, Tamil Nadu, India
3
Department of Oral & Maxillofacial Surgery, SRM Dental College, Bharathi Salai, Ramapuram, Chennai 600089, Tamil Nadu, India
exposure and necrosis in the mouth (nine—SJS). No evidence of clinical laminar resorption was noted in any of the eyes. Conclusion Laminar resorption in MOOKP can lead to vision and globe threatening complications due to the consequent cylinder instability and chances of extrusion. Augmenting the bone on the labial aspect of the canine tooth might have a role to play in delaying or preventing laminar resorption. Keywords Keratoprosthesis . Modified osteo odonto keratoprosthesis . Stevens Johnson syndrome . Ocular chemical injuries . Bone grafting
Introduction Laminar resorption has emerged as a cause for concern following the MOOKP procedure for end-stage ocular surface disorders. Resorption rates have been noted to range between 0 and 28 % in previous studies [1, 2]. Resorption can be detected early by radiological imaging [3, 4] as well as clinically. In extreme cases of severe resorption, patients can present with extrusion of the cylinder or endophthalmitis. In our series of 85 eyes, we noted our resorption rate to be 22.98 % [5]. In this published report on laminar resorption in our series of MOOKP, the mean duration to the first sign suggestive of resorption among patients of SJS was 36.7 months (13 to 60 months), and among patients of chemical injury it was 43 months (28 to 66 months). Though there were earlier reports regarding laminar resorption and means to identify the same by radiological means, there existed no grading system for or means to address resorption. In another recent paper, we proposed a grading system for laminar resorption, along with management options appropriate to the grade [6]. We noted that resorption occurred more commonly on the labial aspect of the lamina with pre-existing
Graefes Arch Clin Exp Ophthalmol
thin bone in comparison to the palatal bone. We also described the successful use of bone morphogenetic protein to salvage laminae with moderate to severe resorption, not threatening cylinder integrity. Herein, we describe the technique and outcome of augmenting the labial aspect of the canine tooth with a mandibular graft prior to harvesting the same for laminar fashioning, in an attempt to delay or prevent the process of laminar resorption in MOOKP procedure.
Patients and methods Institutional Review Board approval was obtained for this study, which adhered to the tenets of the Declaration of Helsinki. Eleven patients in whom the MOOKP procedure was performed between December 2012 to February 2014, underwent the bone augmentation procedure. Informed consent was obtained from all the patients. The procedure was performed by the oromaxillofacial surgeon, along with Stage 1 A of the MOOKP surgery. The procedure was performed under general anesthesia.
Technique of bone augmentation Donor site A bilateral mental nerve block and lingual nerve infiltration with 2 % lignocaine and adrenaline 1:1,00,000 was given in relation to teeth 33–43. A vestibular incision was placed in relation to 43–33 regions and the mucoperiosteal flap was raised. The mental nerve was isolated and protected. A sagittal saw was used for the osteotomy in the chin region. The vertical osteotomy measuring 1 cm lateral to the midline and horizontal osteotomy measuring 1.5 cm in length was placed 5 mm beneath the lower anterior teeth, and was connected by a vertical osteotomy 5 mm medial to the mental nerve measuring 1 cm in length. The two vertical osteotomies were connected inferiorly by a horizontal osteotomy measuring 1.5 cm. Thin spatula osteotomes were used to complete the osteotomy. A bone graft measuring 1.5×1 cm was removed as a block graft from the chin and cancellous bone was also harvested from the deeper aspect. Hemostasis was achieved using bone wax and gelfoam. The wound was closed in layers with 3–0 vicryl. Recipient site The recipient site (right canine or left canine) in the maxilla was infiltrated buccally and palatally with 2 % lignocaine and adrenaline 1:1,00,000. A triangular flap was raised by placing
a crevicular incision around the lateral incisor, canine and first premolar, and a vertical incision was made anterior to the lateral incisor. A mucoperiosteal flap was raised and multiple burr holes were made around the canine with a 1-mm drill to induce bleeding from the outer cortex of the maxilla. The block bone was placed buccally over the canine root region and fixed with a 1.2 mm titanium micro-screw measuring 12 mm in length. Cancellous bone was placed around the block bone and a horizontal relieving incision was placed over the periosteum part of the flap to allow tension-free wound closure. The wound was closed with 3–0 vicryl. A diagrammatic representation of the technique is illustrated in Fig. 1a–d. Postoperative regimen An external dressing applied along the jaw line was removed after 2 days. The patient was administered systemic antibiotic–augmentin and metronidazole for a week, along with chlorhexidine mouthwash for 2 weeks. The ocular medications included topical antibiotics and lubricants, along with systemic acetazolamide if indicated. The harvesting of the augmented tooth is performed 3 months after the bone augmentation procedure. The surgical steps are similar to those described earlier as well as in the Rome-Vienna Protocol, the only difference being removal of the titanium screw after removal of the tooth. The augmented osteo-odonto alveolar lamina is placed in the contralateral subcutaneous cheek pocket for it to develop its fibrovascular covering. Three months later, the lamina is placed in the eye during Stage 2 of the MOOKP procedure.
Results Eleven eyes of 11 patients underwent the bone augmentation procedure prior to the MOOKP surgery at our center between December 2012 and February 2014. The age of the patients ranged from 20 to 40 years (mean age 28.18 years). Of these 11, nine were males and two were females. The primary etiology was Stevens Johnson syndrome in five eyes and chemical injury in six eyes. The mean follow-up after Stage 2 of MOOKP procedure in these eyes was 7.45 months (2 to 20 months). There were no intraoperative complications of the procedure. Postoperatively, the bone graft necrosed in one patient of SJS secondary to exposure due to retraction of the mucosal flap. This was in a patient that has had the MOOKP procedure done for the other eye at our center with loss of lamina to resorption after having maintained a best corrected visual acuity of 20/20 for almost 3 years. In three eyes, there was noted to be peripheral laminar exposure, which required being covered by a tarsoconjunctival pedicle flap.
Graefes Arch Clin Exp Ophthalmol
Fig. 1 a Bone graft harvested from the mandibular bone after lifting the mucoperiosteum. b Graft secured in place over the root of the chosen maxillary canine using a titanium screw. c The mucoperiosteal flap over
the graft, freed to the extent possible using relaxing incisions. d The mucoperiosteal flap secured over the grafted bone at the end of surgery
The laminar dimensions have been noted in Table 1 along with the other patient details.
Since the resorption in our earlier series was always noted to occur along the labial aspect of the tooth, which corresponded to the side with thinner bone support in comparison to the palatal aspect, the authors decided to attempt to increase the bone thickness on the labial aspect by means of bone grafting. Cortical bone grafts have by themselves been harvested and used as a carrier for the optical cylinder, though the resorption rates have been noted to be shorter in comparison to the osteo-odonto alveolar lamina [11]. Various donor sites throughout the skeleton have been investigated and described for bone harvest. Local grafts from the oral and facial region offer a convenient source of bone and have revealed several benefits in the repair of alveolar defects [12]. Mandibular bone grafts, which are primarily cortical bone, exhibit little volume loss and show excellent incorporation at short healing times. Another obvious advantage of local grafts is that donor and recipient sites are in the same
Discussion Most of the patients undergoing MOOKP surgery are young adults. Following the procedure, they get back to a relatively normal life to complete their education and or work. The procedure by itself is a demanding and time consuming one, and takes up to 4–6 months towards completion of all stages. The results of the procedure are encouraging, especially given the good long-term retention of the prosthesis in these eyes [1, 7–10]. One of the issues unique to the MOOKP procedure that threatens the longevity of the lamina is resorption of the lamina [1–5]. Table 1
Details of patients who underwent bone augmentation prior to MOOKP procedure
Serial no
Age (years)
Sex
Etiology
1 2 3 4
40 28 24 21
F M M M
Chemical Chemical Chemical SJS
5 6 7
20 32 35
M M M
8 9 10 11
39 26 26 19
M F M M
Follow-up after stage 2 (months)
BCVA
Lamina dimensions (mm)
4 3 4 2
20/50 20/80 20/20 20/25
12.9×11.5×3.4 14.9×12.1×3.2 13.6×12×3.3 14.95×12.8×3.48
SJS Chemical SJS
12 5 11
20/50 20/30 20/50
13.1×11.9×3.3 13.9×12×3 13.6×11.4×3.5
SJS SJS Chemical SJS
9 0 20 12
20/30
12×10×3.5
CF@2 m 20/20
15.73×12.25×4.0 14.9×13×3.5
Comments
peripheral laminar exposure treated with tarsoconjunctival pedicle flap amblyopic peripheral laminar exposure treated with tarsoconjunctival pedicle flap Bone graft necrosis Optic disc pallor Exposed avascular lamina removed and replaced in subcutaneous pouch—awaiting restage 2
MOOKP modified osteo-odonto keratoprosthesis, BCVA best corrected visual acuity, mm millimeters, SJS Stevens Johnson Syndrome, CF@2 m counting fingers at 2 m
Graefes Arch Clin Exp Ophthalmol
Fig. 2 a Non-augmented osteo-odonto alveolar lamina showing less bone on the labial aspect (indicated by the red arrow). b Augmented osteo-odonto lamina showing more bone on the labial aspect in
comparison to non-augmented lamina (indicated by the red arrow) (dentine aspect). c Augmented lamina showing a centrally placed optical cylinder on the reverse (bone) aspect
operating field, so surgical and anesthesia times are reduced. In addition, these areas may offer a decreased morbidity from graft harvest compared to extraoral donor sites [12]. A plate of mandibular cortical bone 3–4 mm in thickness was added beneath the periosteum of the chosen maxillary canine and secured in place using a titanium screw. The grafted bone was covered by the periosteum and the gingival mucosa. A period of 3 months was allowed for the grafted bone to integrate with the maxillary bone. The length of the grafted bone was longer than the intended length of the tooth harvested (usually 15 mm from the neck of the canine tooth), so as to avoiding interference of the titanium screw in the future lamina. The width of the bone was also wider than the width of the root of the canine so as to straddle minimally over both the adjacent teeth. This added girth to the root following the bone graft slightly increased the effort of harvesting the tooth. The additional bone graft was noted to increase the bone support on the labial aspect of the lamina comparable to that on the palatal aspect (Fig. 2a–c). However, it led to an increase in the width of the lamina, making it larger than the nonaugmented laminae. We anticipated the need for a larger mucosal graft to cover the larger lamina, and hence used a 3.5 cm graft instead of the regular 3 cm graft. Despite this, peripheral laminar exposure secondary to a bulky lamina was noted in three eyes belonging to SJS group, of which two were corrected by means of a tarsal pedicle flap. In one eye, the lamina had to be removed from the eye and replaced back in the subcutaneous pouch due to a large area of exposed avascular lamina. SJS eyes undergoing the MOOKP procedure have been noted to have issues of laminar exposure requiring mucosal revision surgeries, and we had earlier attributed the same to prior mucosal insult that occurs in this group making the mucosa in SJS patients more susceptible to erosion and necrosis [5]. Whether the exposures in the augmented laminae were due to a similar cause, or due to the increased bulk and therefore a mechanical stretch on the mucosa causing its necrosis and lamina exposure, is uncertain. It is however noteworthy that none of the augmented laminae in patients of chemical injuries had a similar laminar exposure.
Combining the bone augmentation with the Stage 1 A of the MOOKP had the advantage of preventing the need for a separate procedure, and therefore exposure to multiple general anesthesia. However, the surgical time increased by an hour and there was the need for the presence of the oromaxillofacial surgeon and the coordination therewith. The duration to the next stage of the procedure also increased to 3 months instead of the usual 1 month, thereby increasing the entire duration of the MOOKP procedure to a minimum of 6 months. The obvious shortcoming of the study is the limited followup period. However, a minimum follow-up period of 4–5 years would be required for proof of the concept, the approximate time period of presentation of patients with issues related to laminar resorption. Considering that the long-term results of MOOKP are by comparison better than the currently used keratoprosthesis for end-stage ocular surface diseases and laminar resorption has been noted across most published series, with no permanent curative or preventive modalities available as of now, the authors are of the opinion and hope that the process of augmenting the tooth using a bone graft could provide a means to delaying or preventing laminar resorption in these eyes.
Conflict of interest All authors certify that they have NO affiliation with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.
References 1.
2.
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