Several types of laminoplasty spacer have been used to fill bone gaps and maintain a widened canal. A 3D scaffold can be used as an alternative spacer to minimize the risk observed in allografts or autografts. This study aims to evaluate the in vivo biocompatibility and tissue–scaffold integration of a polylactic acid (PLA) scaffold with the addition of alginate/hydroxyapatite (HA) and mesenchymal stem cell (MSc) injections. This is an experimental study with a pretest and post-test control group design. A total of 15 laminoplasty rabbit models were divided into five groups with variations in the autograft, PLA, HA/alginate, and MSc scaffold. In general, there were no signs of inflammation in most samples (47%), and there were no samples with areas of necrosis. There were no significant differences in the histopathological results and microstructural assessment between the five groups. This demonstrates that the synthetic scaffolds that we used had a similar tissue reaction and tissue integration profile as the autograft (p > 0.05). We recommend further translational studies in humans so that this biocompatible fabricated scaffold can be used to fill bone defects.