Possibilities of Computer-Aided Design/ Computer-Aided Manufacturing technology in orbit decompression for treatment of endocrine opthtalmopathy

Abstract

Actuality: Endocrine ophthalmopathy (EOP) is a chronic autoimmune disease of the eye, characterized by edema, lymphocytic infiltration of retrobulbar tissue and extraocular muscles with the subsequent develop ment of fibrosis. In a literature EOP is known as Graves’ orbitopathy, thyroid-associated ophthalmopathy or thyroid eye disease. Ninety present of cases of the disease are combined with Graves’ disease (GD), in 5% - with chronic autoimmune thyroiditis and in 5% it develops with absence of thyroid dysfunction [7]. A lot of patients (from 25 to 50%) with GD have clinical manifestations of EOP at the time of diagnosis [2,3]. The main clinical symptoms of EOP are exophthalmos, decreased visual fields, visual acuity, decreased eye mo bility. In the early stages of treatment of patients with EOP is used conservative therapy. Surgical treatment is indicated, when conservative was ineffective. The main surgical treatment for EOP is orbital decom pression. There are two methods of decompression: bone and fat decompression of the orbit, and their combination. Bone decompression of the orbit currently remains the most predictable surgery. However, studies by Leong and Sellari-Franceschini [5,9] reported that the overall incidence of complications ranges from 9.3% to 35%. The most common postoperative complications are: decreased visual acuity, diplopia (15% to 74%), hypoesthesia and dysesthesia of the first and second branches of the trigeminal nerve (17.5% and 28%, respectively), motor disorders (due to injury or fibrosis of the oculomotor muscles), symptomatic sinusitis, haemorrhage into the orbital cavity. Therefore, to define methods of complications prevention after bone orbital decompression is an actual task of EOP management. Aim and objectives: The aim of this study is to evaluate the possibilities of surgical guides application for orbital decompression as method of complications prevention in patients with endocrine ophthalmopathy. Materials and methods: The results of treatment of the 12 patients with EOP, who underwent bone orbital decompression at the Center for Maxillofacial Surgery and Dentistry of the Kiev Regional Clinical Hospital in the period from 2017 to 2020 were analysed. The examination of the patients included visiometry, to nometry, ophthalmoscopy, orbitovolumometry and assessment of the binocular vision. Multispiral comput ed tomography (MSCT) before and after surgery was performed for all patients to clarify the topographic and anatomical features of the orbital walls. Measurement of exophthalmos in the study group was define, based on MSCT, according to the method of Ramli et al. 2015 [6]. Safe zones for decompression was noted in order to prevent damage of the orbital soft tissues and to reduce the trauma of surgery, based on which and applying CAD / CAM technologies, resection surgical guide for decompression were made. The shape of the guide determined the area of bone resection after its placement on the exposed orbital floor and bone tissues were removed in safe zones. The results of the study was carried out by the methods of variation statistics with the determination of average values and errors and their assessment using the paired Student’s test and the Man-Whitney test. Results: The study included 7 (58.3%) women and 5 (41.7%) men with EOP. In total, 24 orbits were oper ated on. The average value of exophthalmos on the left side was 2.46±0.35 cm, on the right - 2.36±0.29 cm, which was interpreted as the presence of exophthalmos according to the recommendations of The Eu ropean Group on Graves’ Orbitopathy (EUGOGO) (2006) [8]. Early postoperative complications (from 12 to 72 hours after surgery) were manifested in the presence of diplopia in 16.6% of cases and hyposthesia of the second branch of the trigeminal nerve in 8.3% of cases. No complication three month after surgery was oserved. Mean exophthalmos value after surgery was 2.11±0.29cm, the left side was 2.14±0.28 cm. Thus, according to the EUGOGO recommendations [8], it can be argued that the patients included in the study showed a statistically significant improvement in the position of the eyes in comparison with preop erative measurements (p> 0.05). At the same time, comparing the results of exophthalmometry of the left and right sides, there was revealed the absence of a statistically significant difference between the studied parameters (p> 0.05). Conclusions: Based on our data, we can conclude that surgical decompression of the orbit using surgical guides makes it possible to achieve a significant decrease in the degree of exophthalmos (on average by 4.4 mm), while reducing the area of bone resection and the risk of postoperative complications