[Semi-joint prosthesis replacement in treatment of malignant tumors around children's knees]

To investigate the effect of the semi-joint prosthesis replacement in treating malignant tumors around the children's knees.

Five children (aged 8-12 years) with malignant tumors around the proximal end of the tibia underwent the semi-joint prostheses replacement from March 2000 to June 2005. All the children had been diagnosed with osteosarcoma, which was graded as II B by the Enneking staging system. The pathologic changes involved the upper segment of the tibia 9-11 cm in length. Before operation all the patients underwent puncture biopsy and standard chemotherapy. The lesion extent was determined by X-ray, CT and MRI, and then the size of the prosthesis was determined. The length of the prosthesis was 1-2 cm longer than that of the excised bone. After operation the patients were given neoadjuvant chemotherapy for 2 courses and they could walk with the help of a special brace 4 weeks postoperatively.

All the 5 patients had a successful semi-joint prosthesis replacement except one patient who had a skin flap necrosis, and the wound healed after a flap grafting. The remaining patients had their wounds healed by first intention. The 12-36 months' follow-up revealed that all the patients had no metastasis or recurrence of the tumor and they were living and well except one patient who died of lung metastasis 8 months after operation.

The semi-joint prosthesis replacement in the limb salvage surgery for malignant tumors around the children's knees has advantages of avoiding a damage to the normal osteoepiphysis, stabilizing the knee joint, and facilitating elongation of the limb in future. It also creates the condition for total knee replacement in adults.