A multicenter retrospective study of artificial joint replacement on giant cell tumor in distal femur

Objective To analyze clinical efficacy of artificial prosthesis in giant cell tumor in distal femur, and to inves-tigate risk factors affecting prosthesis failure and functional outcomes. Methods 42 patients with giant cell tumor of bone in dis-tal femur, who had undergo prosthesis replacement from January 2002 to May 2015, were enrolled in this study. There were 24 males and 18 females, with an average age of 38.53±12.87 years. There were 28 primary patients and 14 relapsed patients, includ-ing 11 cases of recurrence once and 3 cases of twice. Three-dimensional finite element model was used to analyze the effect of different angles of deviation of the spinal needle on the deformation of the bone wall. The correlations between the factors such as age, sex, occupation, prosthesis type, and other factors on prosthesis loosening were compared. Biomechanical effect of lower limbs caused by prosthesis offset angle was analyzed through gait analysis. Analyzed the effects of primary tumor or recurrence, prosthesis service status, and length of surgical osteotomy on joint function. Results A total of 42 patients were followed up by 20-158 months, with an average of 68.7 months. The 3 year survival rate of prosthesis was 83.33% for 3 years and 57.14% for 5 years. The major reason of prosthesis failure was loose (18/42, 42.8%).X-ray films showed 19 cases of prosthetic intramedullary nail and sagittal bias of medullary force line angle >3° in the first follow-up. Osteotomy length (OR=0.132, P=0.0027) and offset angle of needle (OR=25.000, P=0.000) were significantly correlated to prosthesis loose. A length more than 12 cm and angle more than 3° were easier to result in prosthesis loose. There were no significant correlation between prosthesis failure and patients age, gender, occupation and prosthesis type. Gait analysis shows that the unsuitable bias angle of the prosthesis can significantly change the joint force of the prosthesis. The average score of MSTS 93 function evaluation was 25.43±4.256, excellent in 33 cases, good in 7 cases and poor in 2 cases. Function of patients with primary GCT were better than that of recurrent ones. Patients with one 1 times recurrence were better than that of recurrence twice (P=0.003). Patients without prosthesis loosening and revision were better than that with loosening (P=0.001). Patients with an osteotomy length less than 12 cm had a poorer function than that with more than 12 cm (P=0.002). Conclusion The main factors affecting distal femoral prosthesis replacement therapy of GCT is loosening, which was caused by broach and medullary cavity mismatch, osteotomy length, prosthesis rotation, prosthesis position. The function of the prosthesis is mainly affected by operation times, prosthesis status, osteotomy length and low patella. Key words: Giant cell tumor of bone; Femur; Prosthesis; Multicenter study