Achilles tendon, Common calcanean tendon, Paratenon, Tendon regeneration, Microenvironment, Stem/progenitor cell recruitment, Orthopedic surgery, RD701-811, Diseases of the musculoskeletal system, RC925-935

Abstract Background Limited research has focused on the correlation between an external compression and the regeneration of ruptured Achilles tendons. The aim of this study was to evaluate the influence of a constricted paratenon with external compression on the regeneration process of separated rabbit common calcanean tendon stumps. Methods A transection, establishing a 4 mm gap, was created in the right common calcanean tendon of 24 young adult male New Zealand white rabbits. The animals were assigned to two groups: In the control group, only received cast immobilization. In the constricted paratenon (CP) group, the rabbits had a local 3-dimensional printed clasp applied to mimic external compression and same cast immobilization as the control group. Morphologic, histologic and immunohistochemistry examinations were performed at 2 and 4 weeks postoperative. Results Separated tendon stumps were connected by novel granulated tendon fibrils in the control group. However, the regenerated tendon fibrils appeared insufficient in the CP group, the tendon length and the adhesion grade of the CP group was significantly larger than that of the control group at 4 weeks (P