Background: This study evaluated the application of a layered cell free poly (L-lactic acid) (PLLA) scaffold to\r\nregenerate an infraspinatus tendon defect in a rabbit model. We hypothesized that PLLA scaffold without\r\ncultivated cells would lead to regeneration of tissue with mechanical properties similar to reattached infraspinatus\r\nwithout tendon defects.\r\nMethods: Layered PLLA fabric with a smooth surface on one side and a pile-finished surface on the other side\r\nwas used. Novel form of layered PLLA scaffold was created by superimposing 2 PLLA fabrics. Defects of the\r\ninfraspinatus tendon were created in 32 rabbits and the PLLA scaffolds were transplanted, four rabbits were used\r\nas normal control. Contralateral infraspinatus tendons were reattached to humeral head without scaffold\r\nimplantation. Histological and mechanical evaluations were performed at 4, 8, and 16 weeks after operation.\r\nResults: At 4 weeks postoperatively, cell migration was observed in the interstice of the PLLA fibers. Regenerated\r\ntissue was directly connected to the bone composed mainly of type III collagen, at 16 weeks postoperatively. The\r\nultimate failure load increased in a time-dependent manner and no statistical difference was seen between normal\r\ninfraspinatus tendon and scaffold group at 8 and 16 weeks postoperatively. There were no differences between\r\nscaffold group and reattach group at each time of point. The stiffness did not improve significantly in both groups.\r\nConclusions: A novel form of layered PLLA scaffold has the potential to induce cell migration into the scaffold\r\nand to bridge the tendon defect with mechanical properties similar to reattached infraspinatus tendon model.
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