Biomaterials in craniofacial reconstruction

This review highlights some of the recent developments in biomaterials that are suited to reconstruction of the craniofacial skeleton. Although there is no ideal biomaterial, numerous alternatives are available to practicing surgeons that provide attractive alternatives to autogenous bone graft in the appropriate clinical settings. Biomaterials are a particularly well-suited for skeletal augmentation, as autogenous bone can often undergo unpredictable resorption in these applications. Although all of the biomaterials discussed in this article seem to maintain their volume over time, porosity of the biomaterial may be a significant factor in determining bone ingrowth into the implant. Methyl methacrylate is nonporous, and no bone ingrowth is expected. Cement paste implants tend to contain micropores, and experimental and clinical evidence indicates that there is less long-term bone ingrowth into these biomaterials than in implants with macroporous architecture. Biomaterials presently reviewed that have a macroporous architecture and have demonstrated bone ingrowth in clinical or experimental studies include ceramic and granular forms of hydroxyapatite, Hard Tissue Replacement (HTR) polymer, porous polyethylene (Medpor), bioactive glasses (Nova Bone), and demineralized bone paste. Prefabricated biomaterials and those that set as a cement are not designed to change dimension over time and are therefore best-suited for cranial vault reconstruction after completion of skull growth. Rubin and Yaremchuk conducted an exhaustive review of the complications and toxicities of implantable biomaterials used in facial surgery. They reviewed nearly 200 clinical studies reporting series of patients with implantable biomaterials in the face. Polymer and ceramic materials in the face had an overall infection rate of 3% and an exposure/extrusion rate of 1.2%; 4.6% of implants were removed because of implant-related complications. The authors concluded that it is difficult to attribute many of the complications solely to the implant material itself, and that there is much overlap between surgical technique, host response, and potential toxicity of the implant. The authors also noted that the biocompatibility of a material can vary depending on the conditions under which the implant is placed. Proplast had been used for implants in the malar, chin, nasal, and orbital floor regions with acceptable complication rates. However, when it was used as an interpositional disk implant in the temporomandibular joint, complication rates were significantly higher. Nearly all of the Proplast implants fractured over time under the load of the temporomandibular joint, and particulate fragments of Proplast would elicit a vigorous foreign body reaction and contribute to erosion of the joint. Therefore, alloplastic implants used for facial augmentation may have a different outcome when placed in positions subject to stress loading. Although current implant materials have favorable complication rates in most craniofacial applications, a biomaterial that fairs well in one clinical circumstance may not be ideal for all applications in facial reconstructive surgery.