Influence of unfractionated and low-molecular-weight heparin on bone healing: an animal model

The inhibition of bone metabolism and development of osteoporosis under treatment with unfractionated heparins (UFH) have been discussed, whereas the pathomechanism and the question of whether low-molecular-weight heparins (LMWH) have an influence on bone healing as well remain unclear. In a blinded trial,three groups of ten rabbits received subcutaneous injections of an unfractionated heparin (sodium heparin), a low-molecular-weight heparin (certoparin), or normal saline over a period of 6 weeks after a standardized bone defect had been applied to both femur condyles. Healing of the defects was investigated in a depth of 1 and 2 mm and the remaining volume of the bone defects was measured. After therapy with UFH,the volume of the defects remained significantly larger in a depth of 1 mm (UFH/control: p<0.001; UFH/LMWH: p<0.005) and in the total depth (UFH/control: p<0.005; UFH/LMWH: p<0.025). After therapy with LMWH,there was no inhibition of defect healing (p>0.05). This study shows that the influence of heparins on fracture healing can be reduced significantly by using LMWH instead of UFH.