We compared the gross behavior of and microscopic response to implant materials currently in clinical use for facial bone augmentation at different sites in dogs. Materials evaluated include porous polytetrafluoroethylene carbon (Proplast), large-pore high-density polyethylene (Medpor), solid medical-grade silicone rubber (Silastic), polyamide mesh (Supramid), and autogenous rib bone. The subjects were 12 mixed-breed dogs and the materials were implanted directly on bone with periosteum removed at one of three sites in the dog's face (malar eminence, nasal dorsum, and chin). Animals were killed 3 months after surgery and stability of the implants was graded by manual manipulation. Blocks of tissue, including the study materials and underlying bone, were examined microscopically after sectioning. Stability results are tabulated and histologic appearance is described by site for each material evaluated. These data demonstrate marked variability of stability and cellular response depending on the site of implantation. From these data one may conclude that the site of implantation and implant movement are essential factors in determining the nature of the tissue response and fate of an implant. Solid and porous alloplastic materials show an acceptable tissue response, but neither demonstrates the ability to consistently provide an implant that is stable on underlying bone.

The current status of materials for use in middle ear reconstruction is discussed with particular emphasis given to alloplastic implants including bioinert and bioactive materials. Bioglass is a bioactive transparent glass which forms a bond with living tissues. Its development and characteristics are discussed, and the early results of a clinical trial using a Bioglass middle ear prosthesis are presented. The satisfactory tissue response and hearing results found in this preliminary group of patients encourage further clinical evaluation of the Bioglass middle ear prosthesis for use in ossicular reconstruction.

The transoral approach to pathology of the upper cervical spine is logical, but it is seldom used due to concerns about exposure and infection. The authors report on 16 consecutive patients requiring exposure from clivus through C3 for pathology, including spinal cord compression by rheumatoid pannus, craniovertebral anomalies, and tumor. Exposure was obtained using a Dingman mouth gag and soft palate retraction with silicone rubber sheeting. A horizontal "H" incision was made in the posterior pharyngeal wall creating three layers, closed separately, with attention to a watertight closure of the final mucosal layer. In no case was it necessary to divide the mandible, tongue, soft palate, or uvula. There were no deaths, wound breakdowns, infections, or persistent cerebrospinal fluid leakage. Patients with neurological indications improved postoperatively, and all tumors were grossly resected. Combined otolaryngology/neurosurgical exposure and treatment of pathology involving the upper cervical spine via the transoral approach is safe and effective. Functional results have been excellent, and no major complications were encountered.

Four biomaterials, UF45S5 Bioglass, Silastic, Plasti-Pore, and Proplast, were used to replace the incus in a mouse ear model. Bioglass, a bioactive glass ceramic, compared favorably with the other test materials in maintaining surgical positioning between malleus and stapes and remaining stable to a blast of nitrogen gas and to pick manipulation. In a short-term animal study, Bioglass showed histocompatibility comparable to that of these other implant materials now used in ossicular replacement surgery in humans.