1. Clinical data: Male, 27 years old, left knee pain caused by car accident, with mild claudication for 2 or 5 years, unable to walk long distances and climb mountains, etc. Past history: On July 20, 2010, he had an open intercondylar fracture of the left knee joint caused by a car accident and was taken to a level II hospital in Guangzhou by a 120 car. In August 2011, he went to a tertiary hospital orthopedic department to prepare for arthroscopic surgery and removal of nail, the arthroscopic view of the left lateral knee condyle 2, 1*3, 1*1, 5CM size osteochondral defect, the central and peripheral end of the internal fixation nail can be seen, surrounded by fibers; the peripheral osteochondral bone of the main defect area is also not neat, the anterior cruciate ligament is 50% present, the medial meniscus is present, the lateral meniscus is damaged, and with fibers, the It was not possible to visualize it because it was mixed with fibers, internal fixation nails, etc. Since the patient was not well informed about the preoperative replacement to fill the bone defect, the operation was terminated and repaired in the second stage. He was later referred to our hospital for treatment. Systemic condition: normal heart, lungs, liver and kidneys; normal WBC and CRP+ESR. Specialized conditions: left knee extension +2 – 110 degrees of flexion; mild left knee swelling, reduced mobility of the knee bone. Local skin as seen in the picture. Right knee extension – 3 – 155 degrees of flexion. After completion of preoperative CT of the left knee, etc., elective surgery was performed (preoperative X-ray and CT films are shown in Fig. a,b,c,d). 2. Treatment Surgery: Arthroscopic examination was performed in the lateral knee approach first, and after evaluation, an open incision was made. The scar was excised using an incision on the anterolateral side of the knee joint, about 12 CM long (see Figure j). The original femoral condyle lateral internal fixation was removed, and after removing the internal fixation, it was seen that the lateral femoral condyle was severely defective, and the original fixation nail was removed to affect the femoral attachment point of the lateral collateral ligament; the defect area of the femoral condyle was cleaned, and the size and depth were measured, and the size was basically consistent with the original measurement (see Figure e,f,g). Then fresh wet frozen allograft osteochondral bone (specially scheduled to be provided by the Taiyuan Bone Bank in Shanxi, for fresh femoral head donor deep cryogenic sequence freezing with irradiation and rapid air transport use) was thawed in saline and soaked with ciprofloxacin 300 ml for 10-20 minutes after thawing. According to the template, larger whole grafts were repaired for large full-thickness cartilage defects; small peripheral defects were implanted using a special mosaic tool, and whole grafts were sculpted intraoperatively precisely according to defect size trimming. Anchor nails were used to fix the lateral collateral ligament femoral attachment point. The surgical opening is flushed and closed in layers without drainage. At the end of surgery sodium hyaluronate 2,5ML + Depo-Provera 1ML + lidocaine 5ML intra-articular injection (cocktail therapy) with compression bandage. After the patient could eat 6h after surgery, he was given Celecoxib 200mg, 1-2 times/day; Omeprazole 20mg, 1 time/day; Cyproheptadine 2-4mg, 1 time/day. Total 10 days. Postoperatively, a knee brace was given to restrict the knee brace to 0-40 degrees for 1-3 weeks, with non-weight-bearing double crutches for walking, and partial weight-bearing on the ground for 4-8 weeks. Regular follow-up was performed to evaluate the efficacy according to the modified Lysholm score criteria, knee radiology and pain VAS score. Figure a,b,c,d ,male, 29 years old, preoperative left knee X-ray and CT film, the internal fixation and the osteochondral defect of the lateral femoral condyle and the size of the defect are visible; Figure e intraoperative osteochondral defect of the lateral femoral condyle size 2, 1*3, 1*1, 5CM, and also the surrounding cartilage is not smooth, the cartilage surface is distorted and non-anatomical; Figure f is the osteochondral template; Figure g the general view of the osteochondral mass after transplantation; Figure h The postoperative X-rays, which differed from the gross visualization, showed satisfactory repair, but the X-rays showed unsatisfactory filling of the gap between the grafted bone and the host bone; Figure l, preoperative knee scar image; Figure k, postoperative MRI 5 months after surgery, the healing of the grafted bone block and cartilage growth, and the filling of the defect was still satisfactory. Figure l Post-operative knee joint, the scar has been removed; Figure m Post-operative knee extension and squatting at 6 months; Figure n Post-operative patient walking at 9 months. 3. Results Postoperatively, the patient was followed up for 11 months, and the pain was significantly reduced or disappeared with good function. The preoperative modified Lysholm score was 55, and the postoperative score was 87. The VAS score improved significantly; the postoperative review X-ray showed that the curvature of the joint surface could be restored; MRI examination was performed after 5 months after the operation, which showed that the cartilage surface of the original defect area was still smooth, and the transplanted osteochondral bone did not fall off. The knee extension mobility was +2-110 degrees before surgery and 0-130 degrees after surgery (see Figure l,m). 4, Discussion Currently for large area full-thickness layer osteochondral repair in China encountered legal and practical difficulties, in addition to the selection of indications is very strict; the use of allogeneic osteochondral grafts requires caution. If the bone defect is moderate in size, autologous osteochondral grafts can be performed in non-weight-bearing areas, generally less than 2 CM2;; replantation after autologous chondrocyte culture requires two surgeries and is expensive, and too large and too deep defects lack good curvature of the scaffold, which is not yet popular in China. As an alternative is the iliac bone block graft with periosteum, which is lateral to the side of the articular surface and can fill the defect, but is not a hyaline cartilage repair. Allogeneic fresh osteochondral grafts are relatively simple and straightforward, with little rejection. Indications for allogeneic osteochondral grafts: mainly repair of clinically symptomatic, focal, full-layered cartilage injuries. OCD (exfoliative osteochondritis); non-vascular necrosis; post-fracture cartilage defects; subchondral bone defects. Contraindications to allogeneic osteochondral grafts: diffuse degenerative arthritis and rheumatoid/rheumatoid arthritis. Severe hormone-related osteonecrosis. Age <50 years should also be taken into account? , expectations? postoperative rehabilitation conditions, etc. Concomitant joint instability/bad force lines and meniscal damage significantly affect the outcome. Allogeneic osteochondral donor is preferably fresh, with well preserved chondrocytes within 24 hours-4 days; frozen is second best, usually no more than 21 days in theory, so that the defect may be covered by hyaline cartilage. Of course, if there is bone healing between the two, the defect is scarified by bone tissue and the surface is flat, even if it is fibrocartilage, it is better than the defect, which can also serve the purpose of delaying osteoarthritis. 5. Conclusion It is not easy to find fresh and legally permissible allogeneic osteochondral bone in China, and special reservations are needed. Selective allograft osteochondral transplantation for the treatment of traumatic full-thickness large osteochondral defects of the knee in young people is less invasive and is an effective method for treating large, deep cartilage defects with a single site.