Porous Hydroxyapatite and Aluminium-Oxide Ceramic Orbital Implant Evaluation Using CBCT Scanning: A Method for In Vivo Porous Structure Evaluation and Monitoring
Objective. This study aimed to define CBCT as a technique for postimplantation in vivo examination of porous hydroxyapatite and aluminium-oxide orbital implant shape, volume and density changes. Methods and Materials. CBCT was used to evaluate 30 enucleated patients treated with spherical polyglactin 910 wrapped hydroxyapatite and aluminum-oxide orbital implants. The mean duration of patient followup was 3.2 years or 1338 days with a range of 0.2 to 7.2 years or 79 to 2636 days in a population with an average age of 40.8 years. Results. The resolution of currently clinically used CBCT equipment allowed detailed structural observation of the orbital hydroxyapatite implants with some modifications. Volume and shape estimations were possible while density evaluation was more complicated compared to medical source computed tomography. The mean densities of the orbital implants were followed and a consistent gradual decrease identified from the beginning of implantation which was better defined after the applied correction procedure. Conclusion. CBCT with lower dosages of radiation exposure can be used to follow changes in implanted high-density porous structures. The density evaluation is possible with calibration modifications. Changes in orbital implant densities identified in this study may correspond to healing and maturation of soft tissues surrounding and penetrating the implants. 1. Introduction Enucleation has long been used for the treatment of ocular diseases such as intraocular malignancy, severe trauma, and blind painful eye. The major purpose of enucleation is to remove the diseased globe intact and to provide a cosmetically acceptable appearance [1]. The first orbital removal for medical treatment was performed in 1583. In 1885 the first orbital implants to replace the obvious cosmetically deleterious volume loss after evisceration were hollow glass, gold, or silver spheres [1–3]. Since then numerous studies describing different types of enucleation techniques and various types of orbital implants have been published [4–10]. These implanted spheres are permanently buried within the soft tissues of the orbit. Later a cosmetically pleasing, removable shield-like ocular prosthesis made from glass or medical grade acrylic is placed between the remaining conjunctiva and eyelids and supported by the sphere-shaped orbital implant. The characteristics of an ideal orbital implant include adequate volume replacement of the lost globe, good motility and support transmitted to the overlying ocular prosthesis, low rate of complications, and with an
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