The interface between ionomer cement and bone in the porcine cervical spine

The interface between bone and ionomer cement has been studied in twelve young adult pigs 1-6 months after anterior cervical discectomy, removal of adjacent end plates and grafting of the bone defect with ionomer cement. Methods used to study the interface were fluorescence microscopy, 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 the amount of residual movement within the motion segment: animals undergoing anterior plating after reconstruction of the bone defect presented with more or less compactly organized collagenous tissue. Sequential fluorochromic marking of osteoid formation revealed a vital bone bed around the interface but no signs of direct bone apposition to the ionomer 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 density in the porcine cervical spine.