Porous polyethylene implant fibrovascularization rate is affected by tissue wrapping, agarose coating, and insertion site

Purpose: Often used in facial and ocular reconstruction, biointegratable ma terials, such as hydroxyapatite and high density porous polyethylene, can b e associated with migration, exposure, and infection. Complications are les s likely after implants become fibrovascularly integrated. A model was soug ht to study the influence of multiple factors on the rate of fibrovascular ingrowth into porous implants. Methods: High density porous polyethylene cubes were implanted into paraspi nous skeletal muscles in rabbits. The cubes were explanted at weekly interv als using survival surgery. The number of fibroblasts at the center of each cube was counted, generating a time-dependent standard curve of cell accum ulation. Porous polyethylene cubes uncoated, coated with agarose (a plant-d erived carbohydrate), or coated with nonperforated sclera (human or rabbit) were implanted into suprascapular adipose and paraspinous skeletal muscle in other rabbits. Results: Fibrovascular ingrowth occurred more rapidly with cube implantatio n into skeletal muscle versus adipose, with increased surface area contact between implants and muscle, and with removal of muscle capsules. While the rate of fibroblast accumulation decreased in cubes coated with sclera, coa ting the cubes with agarose increased the fibrous capsule formation without altering the rate of biointegration. Conclusions: This study provides a novel approach for the study of fibrovas cular ingrowth into implants treated under a variety of conditions. Modific ation of current surgical techniques may increase the rate of porous polyet hylene implant biointegration.