[Improvement in the primary stability of the dynamic hip screw osteosynthesis in unstable, pertrochanteric femoral fractures of osteoporotic bones by a new glass ionomer cement].

Internal fixation of unstable intertrochanteric fractures of osteoporotic femurs often leads to complications, which are primarily caused by the mechanically weak bone. The aim of this study was to test whether a new glass-ionomeric cement could reinforce the weak trabecular bone of the femoral head and thus improve the preliminary stability of dynamic hip screws (DHS) used for internal fixation. As a standardized model, a intertrochanteric osteotomy was performed on eight pairs of human, female, cadaver femora; a bony defect was also created medially to diminish support of the femoral neck. To stabilize the osteotomy a 135 degrees DHS was inserted. In one femur of each pair the glass-ionomer cement was applied to see whether this would enhance stability. The elastic and irreversible deformation of the internal fixation was measured at the osteotomy level under a cyclic load of 1400 N applied to the femoral head. In both the cemented and the uncemented cases, the femoral head shifted irreversibly in the caudal direction and tilted into a varus position. Movements of the femoral head in other directions were mainly reversible and small. The irreversible movement of the femoral head was significantly larger, approximately twice as great, following uncemented DHS fixation than after cemented fixation. Most movement occurred during the first ten load cycles; higher load cycles did not increase the irreversible deformation in the cemented group, but in the uncemented group a further increase in deformation was detected. These results indicate that internal fixation of unstable intertrochanteric femoral fractures can be significantly improved by the use of cement.(ABSTRACT TRUNCATED AT 250 WORDS)