Introduction:    Limb salvage has become the standard practice in the management of osteosarcoma.  Limb salvage surgery represents a challenge in skeletally immature patients in whom further growth is anticipated. Several options are available for limb reconstruction in children, we report the long term results of using the freezing technique by liquid nitrogen for treatment of lower limb osteosarcoma in children using different reconstruction techniques. 
Method:  This study includes 24 children with lower limb osteosarcoma, average age was13±3.2 y (6-18 y), ten boys. The mean follow-up period was 87.3±44.7 m (28-224 m). In 14 cases the lesion was in the femur, in ten patients it was in the tibia. Joint sparing and intercalary freezing was carried in out in 15 cases, while in five cases, osteoarticular freezing was performed, and a composite technique with a tumor prosthesis was performed in four cases.
Results: Ten patients remained disease-free, eleven patients lived with no evidence of disease, one was alive with the disease, and two patients died of the disease. Five- and ten -year rates of survival were 91.76%. Graft five and ten years survival rates were 91.48% and 83.3 % respectively. Function on the Enneking scale was excellent in 19 patients (79.1%), and good in three patient (12.5%), fair in one (4.1%), and poor in two patients (8.3%), mean MSTS score was 25±5.4 (6-30). Mean union time was 8.7 m±2.1m (6-12m). Mean MSTS score was higher among children who receive a joint sparing rather than a joint sacrificing resection; 27.2 versus 21.3. Complications were recurrence in three cases (12.5%), all recurrences were from soft tissue, collapse of the osteoarticular graft occurred in two cases (8.3%). Fracture of the graft occurred in two cases (8.3%), nonunion occurred in three cases (12.5%). Leg length discrepancy occurred in seven cases, mean difference was 21.8mm±8.3mm (7-31mm), lengthening was carried out in four cases and finally got had equal leg length, in three cases, shoe lefts were enough.
Conclusion:    Reconstruction by frozen bone autograft for osteosarcoma around knee in children is easy, effective, biological, low-cost, immediate mobilization of joints, possible cryo-immune effects, with excellent long term functional outcome and with less complication.