CHARACTERISTICS OF THE TISSUE-RESPONSE TO MEDPOR POROUS POLYETHYLENE IMPLANTS IN THE HUMAN FACIAL SKELETON

The Medpor porous polyethylene implant is a highly stable and somewhat flexible porous alloplast that is used for facial reconstruction and augmentation. A total of 37 surgical biopsy specimens of 32 Medpor imp lants from 24 patients was examined. The specimens were submitted eith er as biopsies performed during staged or revision surgery (28 specime ns), or as a result of implant exposure (9 specimens). All the exposur es occurred in areas of thin soft tissue coverage. Three of the expose d implants were removed; the other six implant exposures were treated by revising the implant and gaining secondary coverage. All specimens, both in the normal biopsy group and the exposed implant group, demons trated soft tissue ingrowth, vascularization with mature blood vessels , and lamellar collagen deposition. Exposed implants had additional fi ndings of inflammatory changes at the site of exposure. Five of the im plants became exposed within 4 weeks of implantation and these also sh owed tissue ingrowth, mature vessel formation, and collagen deposition . These findings demonstrate that soft tissue and vascular ingrowth oc cur in the pores of the Medpor implant in humans. Ingrowth occurred in all cases, including implants that became exposed both early and late after implantation.