CLINICS 2011;66(10):1835-1838 RAPID COMMUNICATION DOI:10.1590/S1807-59322011001000026 Implantation of platelet-rich fibrin and cartilage granules facilitates cartilage repair in the injured rabbit knee: preliminary report Tzong-Fu Kuo,I Ming-Fang Lin,II Yun-Ho Lin,III Ying-Chun Lin,II Rou-Jen Su,IV Hui-Wen Lin,V Wing P. ChanII,IV* I Graduate Institute of Veterinary Medicine, National Taiwan University, Taiwan, Republic of China. II Department of Radiology, Wan Fang Hospital, Taipei Medical University, Taiwan, Republic of China. III Department of Pathology, School of Medicine, Taipei Medical University, Taiwan, Republic of China. IV Department of Radiology, School of Medicine, Taipei Medical University, Taiwan, Republic of China. V Biostatistic Research and Consulting Center, Taipei Medical University, Taiwan, Republic of China. Email: wingchan@tmu.edu.tw Tel.: 886 2 2930-7930 Ext. 1300 *Contact author: Wing P. Chan INTRODUCTION Autologous chondrocyte implantation has become the current principal procedure for cell-based cartilage repair.1,2 However, the disadvantages of autologous chondrocyte implantation include the necessity to perform two surgical procedures: isolation of the chondrocytes from a tissue sample that has been extracted from the patient, which is time-consuming, and implantation of the harvested chon- drocytes after expansion in vitro,3 which has the potential to induce chondrocyte leakage.4 Platelet-rich fibrin (PRF) is a new generation of platelet concentrate that, without anticoagulant, activates the plate- lets of a blood sample and induces degranulation and cytokine release.5 The preparation of PRF is simple and can be completed during one procedure. In dental procedures, when a cystic cavity is filled with PRF, the physiological healing period can be reduced to two months instead of the usual 6 to 12 months.6 The aim of this study was to investigate the regeneration of articular cartilage defects of the knee following the implanta- tion of PRF with cartilage granules in a one-step procedure in rabbits using T2-map magnetic resonance imaging (MRI) and histology to assess the rabbits’ response to the procedure. MATERIALS AND METHODS The Institutional Animal Care and Use Committee at the National Taiwan University and Taipei Medical University approved the breeding of the animals and the protocol. A total of 12 New Zealand white rabbits (age: 10-12 weeks; weight: 2-3 kg) were divided into two groups. In group A (n = 6), a cartilage defect was created with no implantation. In group B (n = 6), a cartilage defect was created, and a mixture of PRF and cartilage granules was implanted. In Copyright 2011 CLINICS – This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http:// creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non- commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. No potential conflict of interest was reported. 1835 group B, one rabbit’s unoperated left hind leg was used as a positive control and as a tissue morphological reference for histology. The PRF was prepared using the technique described by Dohan et al.7 Immediately after 3 cc of blood had been drawn from the jugular vein of each rabbit during surgery, the blood sample was centrifuged in a 5-mL sterile tube (without anticoagulant) at 400 g for 10 min using a PC-02 laboratory centrifuge (Process, Nice, France). Using forceps, the PRF gel (Figure 1) was removed from the middle layer of the sample in the tube; this layer was located between the red corpuscles at the bottom of the tube and acellular plasma at the top of the tube. The total volume of PRF was 3 calculated to be 0.77 cm . The PRF gel was sectioned into two to three pieces, mixed with the cartilage fragment that was obtained from the created cartilage defect and ground into small granules (approxi- mately 1 mm in diameter) to fill in the excision defect. Surgery was performed under general anesthesia by a senior surgeon (T-F. K) using magnifying loupes (2.56, Heine HR, Germany). The rabbits were injected intramus- cularly with a mixture of ketamine (100 mg/mL, 0.6 mL/kg body weight) and xylazine (20 mg/mL, 0.3 mL/kg body weight). In each animal, a hollow cylindrical scoring device with a graduated diameter was used to create a cartilage defect surgically (diameter: 3 mm; depth: 0.5 mm) in the weight-bearing portion of the medial femoral condyle of the right hind leg knee. In both groups, the holes were covered with a periosteal patch and secured with sutures. The periosteal patch that corresponded to the size of the area of cartilage damage had been harvested from the tibial shaft. Suturing was started from the medial side using a four- corner technique with a 7-0 absorbable suture (Prolene, Ethicon, Johnson & Johnson). The area between the 9 o’clock and 3 o’clock positions was left unsutured for the purpose of PRF and cartilage implantation. Once the implantation was performed, the suturing was completed. Three months after surgery, the animals were scanned using MRI, which was performed using a 1.5-T magnet (Signa Horizon LX, GE Medical Systems, Milwaukee, WI, USA.) with a commercial 3-inch surface coil on anesthetized animals. The T2 measurements used a multislice multi-echo