The Experimental And Clinical Study Of Surface Hemiarthroplasty And Implantation Of Hydroxyapatite Methylmethacrylate Cement In Treatment Of The Femoral Head Osteonecrosis

Objective To study the biomeehanical effects of using surface replacement and THR prostheses on the upper femur, and observe mechanical and biological changes of polymethylmethacrylate cement modified by adding different weight ratio of hydroxyapatite. Evaluate the clinical results of surface replacement hemiarthroplasty and implantation of hydroxyapatite methylmethacrylate cement in the treatment of osteonecrosis of femoral head. Methods (1) Experimental stress-analyze methods of axial compression, pull-out and torsion tests were taken for biomechanieal comparison of surface replacement and THR prostheses in twelve fresh, adult human cadaver femora. (2) Nine hips in six patients with femoral head osteonecrosis of Ficat stagelll were treated with surface replacement hemiarthroplasty and were reviewed. (3) The mechanical and biological properties of four types of hydroxyapatite methylmethacrylate cement with different proportion by weight ratio were measured by compressive strength and bending strength. The bioactive bonding strength was taken by push-out test after implanting the specimens for 8 weeks in the distal portion of rabbit femur. (4) The patients with femoral head osteonecrosis of Ficat stagelll were operated using implantation of hydroxyapatite methylmethacrylate cement and reviewed. Results The strength and stiffness of upper femur treated by surface replacement prostheses is stronger than that by THR prostheses. It has similar biomechanical properties with original æ…” ⁽ human femur. The average Merle d扐ubigne score of patients with femoral head osteonecrosis after surface hemiarthroplasty was improved from 6 to 15.5.BMD of the upper femur was unchanged examined by DEXA. The mechanical and thermogenesis properties of 35wt0 ohydroxyapatite methylmethacrylate cement were less than methylmethacrylate cement without hydroxyapatite ,and the mechanical properties was still better than cancellous bone, and the bioactive bonding strength increased. The patients of femoral head osteonecrosis treated with hydroxyapatite methylmethacrylate cement implantation were followed up at least five years. The Merle d扐ubigne score of patients was increased from 5.5 to 14.5. Conclusion The surface replacement prosthesis is coincident with normal biomechanical pattern of human being. Surface replacement hemiarthroplasty is a rather good method in treatment for femoral head osteonecrosis of Ficat stage III. 35wt 0o hydroxyapatite methylmethacrylate cement can substitute the necrotic bone of femoral head. The medium-term results of operation by implantation of hydroxyapatite methylmethacrylate cement are satisfaction. The operation maybe also a method of choice in the treatment for osteonecrosis of femoral head of Ficat stage III. Liu Song (Specialty of Orthopeadics) Directed by Prof. Dong Tianhua...