A Biocompatible Silicone Framework for External Ear Reconstruction Using a Phosphorylcholine Coating

Abstract

Sir: The application of a novel biocompatible framework for ear reconstruction is described in a patient who was not enthusiastic about autologous reconstruction using costal cartilage or the use of a temporal parietal flap required when using a Medpor prosthesis. Preformed Silastic frameworks in ear reconstruction were first used by Cronin and Ascough in the 1970s,1 but they were prone to problems, most notably that of extrusion. The nonvascular nature of synthetic materials impedes healing and induces deposition of scar tissue around the implant, which may distort the framework shape. The silicone ear prosthesis was coated in a synthetic polymer (Fig. 1) incorporating phosphorylcholine (Vertellus Specialties Ltd., Middlesbrough, United Kingdom), which has a chemical nature similar to that of cell membrane lipids, and has been used to coat a number of implanted medical devices. Studies show that phosphorylcholine polymers significantly reduce protein deposition, cellular adhesion, and biofilm formation, and greatly reduce capsule thickness around implants.2,3 This case is the first documented application of a phosphorylcholine-coated silicone framework prosthesis in humans.Fig. 1.: Phosphorylcholine-coated silicone ear prosthesis.Under local anesthesia, a subcutaneous pocket was dissected to accommodate the framework. The patient was pleased with the result, but the projection was not enough to quite balance the left side. After 4 years, the implant was exchanged with a slightly larger one. The first framework was easy to remove and was not distorted or covered with a scar capsule, as is normally encountered around silicone prostheses. Analysis of the explant with rhodamine dye showed that the phosphorylcholine coating was still evident on the framework. This second framework has now been implanted for 1 year, has maintained good shape, and remains covered in soft healthy skin (Fig. 2). The patient routinely sleeps on his reconstructed ear, and it withstands the knocks of everyday life well.Fig. 2.: Oblique view of the ear 1 year after insertion of a second prosthesis.The prosthesis underlies native temporomastoid skin such that there is no color mismatch with surrounding tissues. The flexible nature of the ear also feels more natural than that of a rigid costal cartilage construct. Its shape can be precisely determined preoperatively with the patient's input. A mold can be taken from the contralateral ear, if available, to help design the prosthetic framework, and removes the uncertainties of a single intraoperative attempt of carving costal cartilage. The phosphorylcholine coat should reduce encapsulation and thus the risk of distortion to the ear, but also allows for ease in exchanging the implant if the shape or size is unsatisfactory. In summary, our 5-year experience of this relatively simple method of ear reconstruction is very encouraging and is worthy of consideration for a larger, longer term trial. It avoids the more invasive approach of other forms of ear reconstruction and appears suitable for those unwilling or unable to undergo more complex surgery under general anesthesia. In this case, progressively larger prostheses were inserted as a means of tissue expansion, such that the patient was never without an ear. The use of a phosphorylcholine coat to reduce biofilm formation and scar tissue encapsulation has promising applications in other silicone-based products in reconstructive surgery. Colin Link, M.B.B.S. Anthony Barabas, M.R.C.S.(Eng.) St. Georges Hospital London Brent Tanner, F.R.C.S. East Grinstead Hospital East Grinstead, United Kingdom