BIOMECHANICAL SUBSTANTIATION OF OPTIMAL CONTENT OF COMPOSITE USED IN PERCUTANEOS VERTEBROPLASTY

Abstract

Objectives. To specify optimal content of the injectable composite material for percutanious vertebroplasty. Material and Methods. Two sets of experiments were performed. Alimentary osteoporosis was induced in 19 rats and confirmed histologically in 3 rats. Sixteen rats underwent anterior procedure of spherical defect drilling in L6 vertebral body. The defect was filled with bone cement (Osteopol-V) in group I (n = 8) and with composite material (Osteopol-V – 80 %; hydroxiapatite (HAP) – 4 %; tricalcium phosphate (TCP) – 16 %) in group II (n = 8). Vertebral bodies were extirpated three months after vertebroplasty. Four bodies in each group were subjected to biomechanical testing, another four – to hystological one. Results. The elastic modulus of composite material is most similar to that of the cortical bone when it contains 80–90 % of bone cement with HAP/TCP ratio to be 2:8, as was confirmed by mathematical calculations. Mechanical testing of specimens have shown that the most strong composite contain 80 % of bone cement, 4 % of HAP, and 16 % of TCP. Experimental testing of intact osteoporotic vertebral bodies vs vertebral bodies 3 months after vertebroplasty with bone cement (Group I) and with composite material (Group II) has clearly shown, that composite material provides a higher strength, bone tissue ingrowth into resorbable ceramic, and a solid osteointegration. Conclusion. New injectable composite material significantly increases the strength and stiffness of both fractured and nonfractured osteoporotic vertebrae. This material can be used for restabilization of osteoporotic compression fracture and for prevention of vertebral body compression in osteoporosis.