Silicone rubber temporomandibular joint (TMJ) meniscal replacements: Postimplant histopathologic and material evaluation

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Abstract
Medical grade silicone rubber has long been considered a suitable meniscal replacement, but there has been increasing concern about migration of this material into adjacent tissues. The objectives of this study were to determine the definitive composition of tissue-incorporated material which is presumed by light microscopy to be silicone and to identify long term histopathologic sequelae of meniscal replacements. Adult female patients underwent meniscectomy and replacement with silicone rubber (Silastic) implants. After 12 to 18 months, recurrence of symptoms in 8% of these cases led to implant removal with excision of peri-implant fibrous pseudo-capsules. Excised tissues, including one preauricular lymph node and implants were submitted for light microscopy, SEM, and energy dispersive x-ray microanalysis (EDX) for the identification of elemental composition, critical surface tension measurement, and internal reflection infrared spectroscopy. EDX revealed prominent peaks for silicon in both pseudocapsular and nodal tissues. Morphologic findings surrounding the long-term implants included foreign body reaction, synovitis, dystrophic calcification, fibrocartilaginous metaplasia, hyalinization, and scarring. Particulate silicone debris induced a pathologic response in the tissues and migrated to nodes. These findings suggest that periodic evaluation be performed over the life of such implants to rule out breakdown under function. These findings should intensify the search for improvements or replacements for silicone rubber as an interpositional material in the temporomandibular joint.