EXTRUSION OF POROUS POLYETHYLENE ORBITAL IMPLANT IN RECURRENT RETINOBLASTOMA

High-density porous polyethylene allografts are used as orbital implan ts in reconstruction of anophthalmic sockets. The use of this material for integrated buried implants is rather new, and studies on removed implants from humans are limited. We studied the case of a 6-year-old boy with an extruded porous polyethylene implant due to orbital recurr ence of retinoblastoma. The clinical and morphological features are re ported. Histopathology revealed fibrovascular downgrowth in the outer two thirds of the sphere. Scanning electron microscopy, however, docum ented further downgrowth of fibrous tissue into the central core. Tran smission electron microscopy depicted a spectrum of collagen fiber ori entations to polyethylene material, ranging from perpendicular to conc entric. Immunohistochemistry studies were inconclusive.