THE INTERFACE BETWEEN IONOMER CEMENT AND BONE IN THE PORCINE CERVICAL-SPINE

The interface between bone and ionomer cement has been studied in twel ve young adult pigs 1-6 months after anterior cervical discectomy, rem oval of adjacent end plates and grafting of the bone defect with ionom er cement. Methods used to study the interface were fluorescence micro scopy, scanning electron microscopy, electron microprobe analysis and radiological investigation. The interface in all animals consisted of collagenous tissue. The amount of collagenous fibres was related to th e amount of residual movement within the motion segment: animals under going anterior plating after reconstruction of the bone defect present ed with more or less compactly organized collagenous tissue. Sequentia l fluorochromic marking of osteoid formation revealed a vital bone bed around the interface but no signs of direct bone apposition to the io nomer cement plug. No signs of toxicity or graft rejection were noted. Ionomer bone cement contrary to experimental and clinical experience induces the formation of a connective tissue layer of different densit y in the porcine cervical spine.