Prosthetic Replacement For Osteosarcoma Around The Knee:Short-term Follow-up And Functional Evaluation

Objective:To evaluate the short-term clinical outcome of prosthetic knee replacement in patients with osteosarcoma around the knee joint who have undergone the surgery, focusing on the knee joint function, survival rate and post-operation complications.Method:A total of31patients were retrospectively followed up from January2010to April2013, who were admitted in our department with tumor resection and prosthetic replacement. The31patients were divided into two groups (Distal femur group and Proximal tibia group). The follow-up ranges from12to36months (mean time21.5months), including oncology prognosis, limb function and prosthetic situation. Functional evaluation was based on the Musculoskeletal Tumor Society Scoring system(MSTS93), with numerical values from0to5points assigned for each of the following six categories:pain, function, emotional acceptance, use of supports, walking ability and gait.The t-test or rank sum test was used to compare single factor which would affect the functional scores. The survival situation of the prosthesis were analyzed by the Kaplan-Meier survival curves, and the risk factors which would affect the survival were analyzed by the log-rank test.Results:All31patients were alive when followed up, including25cases with tumor-free survival (80.6%),6cases survival with tumor (19.4%),2cases with local recurrence (6.5%),4cases with distant metastasis (12.9%). Of all the31patients alive, The result of MSTS93functional scores (after6months) was23.4±3.2, in which the distal femur group was23.6±3.6, proximal tibia group was22.9±2.5(p=0.559).The knee activity(range of motion) of distal femur group with two months after surgery was55.8°±22.3°, and proximal tibia group was26.7°±11.3°(p=0.000). The knee activity of distal femur group with6months after surgery was97.6°±10.8°, and proximal tibia group91.7°±7.5°(p=0.107).21patients were followed up for more than two years. The distal femur and proximal tibia group2-year survival rates were83.3%and77.8%(p=0.997). The rate of various types of prosthetic complication was19.0%(4/21); One patient in distal femoral group was given amputation due to local relapse, one was given debridement and irrigation due to infection; Two patients in proximal tibia group accepted amputation because of the deep infection.Conclusion:1. Prosthetic replacement for osteosarcoma around the knee has a satisfactory oncology prognosis and limb function;2. The ranges of motion of the knee joint within two months after surgery is significantly associated with tumor location. The distal femur group is better than the proximal tibia group. However, no significant difference is found in the two groups within six months after surgery. There is no significant difference between the two groups about MSTS93scores.3. There will be certain cases of complications after prosthetic replacement. The survival rate of prosthesis is significantly affected by operative region infection, but not related to tumor location, gender, age of first diagnosis, postoperative knee angle, and MSTS93function score.