Implantation of porous acrylic cement in soft tissues: an animal and human biopsy histological study.

Long-term (8 and 24 month) reactions of the (hypo) dermis of the guinea pig to solid and porous (50 vol%) acrylic implants and four human biopsies from porous subcutaneous acrylic implants were studied light microscopically. The solid implants were encapsulated by dense connective tissue. Mobility was evidenced by the loss of 4 out of 36 after 2 yr and was considered the explanation for the occurrence of ectopic cartilage and mineralized material at some solid implants' surfaces after 2 yr. A dense capsule was not evident with the porous implants, instead vascularized collagenous connective tissues penetrated into and filled the pores, thus anchoring the implant to the body. None of these implants, was lost. Notwithstanding the presence of some multinucleated giant cells, scattered inflammatory cells and loosely packed inflammatory foci with both implant materials, the materials were considered well-tolerated by the body. The histology of the human biopsy did not differ significantly from the porous animal implants.