Kinetic study of the replacement of porcine small intestinal submucosa grafts and the regeneration of meniscal-like tissue in large avascular meniscal defects in dogs

Porcine small intestinal submucosa (SIS) was used to replace large, avascul ar defects in the medial menisci of dogs. Twelve dogs received SIS grafts a nd 3 dogs were left untreated as controls. Dogs were evaluated at 4, 8, and 12 weeks by means of lameness scoring and ultrasonography. Dogs were sacri ficed at 1, 6, or 12 weeks after implantation, and the tissue at the site o f meniscal resection was evaluated for gross and histologic appearance, cro ss-sectional and surface area, and collagen types I and II. The femoral and tibial condyles were assessed for articular cartilage damage. Control dogs were significantly more lame than grafted dogs 8 and 12 weeks after instru mentation. Grafted dogs' replacement tissue appeared meniscal-like when eva luated grossly and ultrasonographically 12 weeks after instrumentation. The amount of replacement tissue was significantly greater in both cross-secti onal and surface area for grafted dogs than for controls at all time points . Histologically, the SIS biomaterial could be identified in all grafted do gs at 1 week post-implantation, but in none at 6 weeks post-implantation. S ubjectively, grafted dogs' replacement tissue was histologically superior t o that of controls with respect to tissue type, organization, and architect ure. Collagen types I and II immunoreactivity in grafted menisci were simil ar to that of normal menisci. Control dogs had significantly more articular cartilage damage than grafted dogs. SIS appears to induce regeneration of meniscal-like tissue in large, avascular meniscal defects in dogs, resultin g in superior clinical function and articular cartilage protection compared to ungrafted controls.