INTRODUCTION: Medial open-wedge HTO is an alternative in the treatment of medial knee OA for the young and active patient. However this technique leaves an open gap that requires stable fixation to achieve bony healing. As a bone substitute injectable calcium-phosphate-cements could be an alternative to autograft.

MATERIAL AND METHODS: Biomechanical testings were performed on open wedge HTO to investigate load to failure and displacement after cyclic loading (viscous and/or damaged material response). A medial 10 mm open-wedge osteotomy was performed on 7 pairs of composite (Sawbone) left tibiaes, and 8 pairs of preserved cadaver tibiaes. Osteosynthesis where performed with the Dynafix system. In half of the bones the gap was filled with 15 g of Calcibon®. The composite tibiaes were loaded at a ramp speed of 20 mm/min and failures of the constructs were recorded visually. On the cadaver tibiaes, cyclical loading were performed with a maximum load of 2250 N.

RESULTS: Filling of the gap with Calcibon® resulted in significant different load-to-failure patterns with failure at 10.2 kN compared to 2.7 kN in the group without Calcibon®. Displacement at the end of cyclical loading was 1.2 mm in the group with Calcibon® and 2.7 mm in the group without Calcibon®. This difference also was significant.

CONCLUSION: The injectable calcium-phosphate-cement Calcibon® enhances primary stability during load to failure and during cyclical loading in open wedge osteotomies on proximal tibia. Clinical studies are performed to investigate whether Calcibon® has any clinical advantage on wedge healing and stability.