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

Purpose: Often used in facial and ocular reconstruction, biointegratable materials, such as hydroxyapatite and high density porous polyethylene, can be associated with migration, exposure, and infection. Complications are less likely after implants become fibrovascularly integrated. A model was sought 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 paraspinous skeletal muscles in rabbits. The cubes were explanted at weekly intervals using survival surgery. The number of fibroblasts at the center of each cube was counted, generating a time-dependent standard curve of cell accumulation. Porous polyethylene cubes uncoated, coated with agarose (a plant-derived 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 implantation 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, coating 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 fibrovascular ingrowth into implants treated under a variety of conditions. Modification of current surgical techniques may increase the rate of porous polyethylene implant biointegration.