Porous and porous-compact ceramics in orthopedics.

A bioceramic material has been obtained by a group of researchers with the collaboration of bone surgeons and veterinary doctors. This material has the following properties: chemical composition, 97% Al2O3, 2.5% MgO, and 0.5% CaO; mineral composition, alpha-Al2O3 corundum, MgAl2O4 spinel; open porosity, 70-80%; pore diameter, more than 90% of pores between 100 and 800 microns; bending strength, approximately 15 MPa. Experiments performed on rats, rabbits, and sheep demonstrated good biocompatibility with the material implanted in their bone tissue. The outer and the inner pores were filled with the healthy bone tissue adherent to the ceramic material, and a strong biologic bond was created. The material penetrated by this mineralized bone tissue increased its mechanical strength by about 70%. These properties of the material may encourage its application to bone surgery. The porous ceramics were implanted in the bones of more than 200 patients. Observations revealed that the process of bone tissue ingrowth into the pores of material had been accomplished in two to three months. The application of the material included filling the bone cysts, postsurgical or trauma-related bone defects, destroyed vertebra caused by the removal of bone tumors, and in the alloplasty of the hip joint. A modification of the ceramic material described above has been developed: a porous-compact ceramic material that is integrally bonded and has mechanical strength several times greater than the porous one. It also enables the biologic connection with the bone. This type of material has been used for filling the dome of the acetabulum in the "coxa protrusa" and in the alloplasties of the hip joint.