BACKGROUND : When auriculoplasty is performed for microtia, wire often becomes exposed during the long postoperative period. We have investigated other materials for fixing cartilage. We previously reported that absorbable sutures are more appropriate than wire. The present animal experiments investigated the reasons why fixation of transplanted cartilage is maintained when using absorbable sutures. METHODS : The costal cartilages of Sprague-Dawley rats were harvested, and three cartilage transplant models were prepared. After bending a costal cartilage into a U-shape, it was fixed by using only absorbable sutures as the control or was fixed by suturing one or two cross struts of cartilage to the U-shaped graft. Then the cartilages were subcutaneously transplanted into the backs of the rats. They were removed 8 weeks later, and the return rate of the bent cartilages was assessed. RESULTS : The return rate was 74.0%, in the suture-only group (control), 27.9% in the one-strut group, and 8.3% in the two-strut group. When the sites of contact between the U-shaped graft and the cartilage struts were observed by light microscopy, adhesion of the two cartilages by fibrous connective tissue was observed. CONCLUSIONS : U-shaped cartilage grafts demonstrated a smaller return rate when there was a larger contact area with the cartilage struts. Each strut was fixed by fibrous connective tissue at the contact site, thereby maintaining the shape of the graft. Thus, when creating a cartilage framework, it is important to fix the bent cartilage to the cartilage struts with a sufficiently large contact area.