The Role of Imaging in the Evaluation of the Osteo–Odonto–Acrylic Lamina in OOKP Surgery

Abstract

Abstract: : Purpose:Osteo–odonto–keratoprosthesis (OOKP) surgery is a technique used to replace damaged corneae in blind patients for whom cadaveric transplantation is not possible. The procedure involves utilising the patient’s tooth root and alveolar bone to support an optical cylinder. Bone resorption of the osteo–dental lamina can lead to extrusion of the acrylic cylinder. We have analysed the lamina dimensions using computed tomography (CT)/ electron beam tomography (EBT) to localise early resorption and thereby help predict cases where early re–intervention is necessary. Methods: A non–comparative case series was studied, based on the retrospective analysis of hospital records and cross–sectional imaging, of all patients who had undergone OOKP surgery between 1996–2004. Spiral/multi–slice CT or EBT with three–dimensional reconstructions (3D) was performed in all cases. The dimensions of the lamina were then measured and compared to those taken at the time of surgery. An analogue scale (0–3) was used to grade the degree of resorption. Results: Thirty five patients had undergone OOKP surgery between 1996–2004. Twenty patients (10 male and 10 female) with a mean age of 51.5 years (range 19–79 years) were entered into the study. Indications for OOKP surgery included Stevens Johnson syndrome, ocular cicatrical pemphigoid, drug induced scarring, graft versus host disease, linear IgA disease, congenital trigeminal nerve hypoplasia, trachoma and ectodermal dysplasia. 18 patients received autografts and 2 allografts. The OOKP lamina was lost in 4 patients due to bone resorption. In 2 cases bone resorption was monitored with imaging and guided early re–surgery. Explanted laminas clinically showed 100% concordance with the imaging findings. Conclusions: OOKP surgery is a complex procedure requiring life–long follow–up. The preservation of the osteo–odontal lamina is the key factor in the longevity of the OOKP. Post–operative CT and EBT are invaluable tools for detection of early, pre–clinical lamina resorption. This enables early prophylactic measures to be taken to preserve the lamina and prevent resorption related complications such as aqueous humour leakage, inflammation and extrusion of the optical cylinder.

Keywords: keratoprostheses • imaging/image analysis: clinical