The treatment of bone defects is still a challenging problem in the orthopedics field. Autograph is the gold standard of bone defect treatment. However, the bone that is used as a scaffold in this procedure is limited. Bovine hydroxyapatite (BHA) and gelatin (GEL) composites are osteoconductive biomaterials suitable as bone scaffolds. In addition, alendronate can be added to these composites to increase osteogenesis from osteoblasts and the expression of osteogenic markers. The scaffold was made of a BHA-GEL composite added with alendronate of 0.1%, 0.5%, and 1%  concentration and were formed as cylindrical pellets having physicochemical characteristics as a good scaffold. Furthermore, the animal groups were divided into five groups: the negative control, BHA-GEL, ALE 0.1%, ALE 0.5%, and ALE 1%. The in vivo was performed in weeks 2, 4, and 8 by evaluating the callus growth with X-Ray radiography, the histopathology with Hematoxylin-eosin (HE) staining for osteoblasts, osteoclasts, osteocytes and new bone matrix. Bone marker analysis was also conducted by using alkaline phosphatase (BALP), osteocalcin, and Bone Morphogenetic Protein 2 (BMP-2). Based on the physicochemical characteristics, all of the scaffolds worked well for the bone defects. The bone formation analysis  showed that the scaffold increased osteoblasts and osteocytes in all groups in 2, 4, and 8 weeks.New bone matrix in all group increased insignificantly in 2, 4, and 8 weeks. The number of osteoclasts in groups of BHA-GEL and ALE 0.1% increased in 2 and 4 weeks. The BALP level in BHA-GEL and ALE 0.1% groups, increased in week 2. The increase of osteocalcin level occurred in all groups in 8 week while the increase of BMP2 level in the groups of BHAGEL and ALE 0.1% occurred in 2 and 4 weeks. The healing mechanism occurred in 2 pathways: (1) the increase of BMP2 level, followed by the increased number of osteoblast cells and osteocyte cells triggering the increase of new bone matrix and (2) the increase of BMP2 level, continued by the increase of the number of osteoblast cells, osteocalcin level, and the number of osteocyte cells resulting in new bone matrix increase. The BHAGEL-ALE scaffold resulted in the acceleration of the healing of bone defects with the best scaffold of ALE 0.1%. 

 Keywords: bone defect, bovine hydroxyapatite, gelatin, alendronate, scaffold