Porous Tantalum Implant for Treatment of Early-stage Osteonecrosis of the Femoral Head: A Minimum 5-year Follow-up Study

Background: To evaluate the survival rate of porous tantalum rod implantation in the treatment of osteonecrosis of the femoral head, to evaluate its clinical effect and imaging results, and to analyze the reasons for its failure to conversion to total hip arthroplasty (THA). Methods: From January 2008 to December 2013, tantalum rod implantation for osteonecrosis of the femoral head was performed in two institutions. Statistical analysis of operation data, including operation time, blood loss and blood transfusion. Histopathological observations were performed on femoral head specimens with the tantalum rods that failed THA after tantalum rod implantation. Results: 52 hips were followed up completely, the average follow-up time was 85.7 months (60-132 months). 24 hips turned to THA at the end of follow-up (46.2%), the average time was 44.3±32.8 months, and the average Harris score before THA was 57.1±7.6. Cox proportional-hazards model revealed that ARCO stage (P=0.017), bone marrow edema (P=0.006) and age＞40 years(P=0.043)were independent risk factors for conversion to THA. Histopathological examination revealed the implant surface is in contact with sparse Island bone. There is limited bone tissue extending inward from the implant. Conclusion: The medium and long-term clinical effect of tantalum rod implantation in the treatment of osteonecrosis of the femoral head is not as satisfactory as we expected, and the osteogenic activity of tantalum rod in the femoral head is limited. ARCO stage, age and bone marrow edema were risk factors for the failure of tantalum rod implantation to THA.