Abstract: BACKGROUND: The prosthesis replacement with tumors of the proximal tibia will lead to complications such as local prosthesis exposure and infection. The transfer of the medial gastrocnemius muscle flap to cover the surface of the tibial prosthesis can effectively reduce the risk of postoperative complications. However, in the replacement of the long-segment proximal tibia prosthesis, the transfer of the gastrocnemius muscle flap to cover the tibia is only used. The area of the prosthesis is limited, and it needs to be reconstructed with other repair methods.  
OBJECTIVE: To investigate the clinical effect of applying gastrocnemius muscle flap and soleus muscle flap to repair the soft tissue defect after tibial prosthesis replacement.
METHODS:  From March 2017 to June 2020, 17 patients with proximal tibia malignant bone tumor admitted to the Shengjing Hospital of China Medical University. All tumors were treated by tumor segment resection and tumor knee prosthesis replacement. The medial gastrocnemius muscle flap alone was used to reconstruct the anterior tibial soft tissue defect, when the difference between the length of the tibia prosthesis and the maximum width of the gastrocnemius muscle flap was less than or equal to the maximum width of the gastrocnemius muscle flap. The medial gastrocnemius muscle flap combined with the soleus muscle flap could effectively cover the tibial prosthesis without tension, when the difference between the length of the tibia prosthesis and the maximum width of the gastrocnemius muscle flap was greater than the maximum width of the gastrocnemius muscle flap. Patients were followed up regularly after surgery, and lower limb function was evaluated by the Musculoskeletal Tumor Society scoring system.  
RESULTS AND CONCLUSION: (1) All 17 patients were followed up, with a mean of (17.5±9.8) months. (2) The incisions were healing by first intention in all patients without infection, skin flap necrosis and other complications. One patient with osteosarcoma underwent amputation due to periprosthesis infection after chemotherapy one year after knee prosthesis replacement, and there was no case of revision of tumor prosthesis, metastasis or death. (3) Musculoskeletal tumor society score was averagely 24 points, of which 10 cases were excellent, 2 cases were good and 5 cases were fair. The knee flexion angle was (84.76±12.88)°. (4) Above data confirmed that during limb salvage treatment of tumor prosthesis of proximal tibia, gastrocnemius muscle flap and soleus muscle flap were selected to repair soft tissue defects according to the difference between the length of tibia prosthesis and the maximum width of gastrocnemius muscle flap, which could fully cover the prosthesis surface without tension and effectively reduce local complications.

Key words: bone, proximal tibia, bone tumors, tumor knee prosthesis, soft tissue defect, gastrocnemius muscle flap, soleus muscle flap, apparatus of extention knee, limb salvage