| Objective To investigate the bone marrow mesenchymal stem cells/periosteum coated (lactic acid-glycolic acid, PLGA) in promoting the healing of large bone defect in the ulna in rabbits. Methods Twenty adult New Zealand rabbits were rand omly divided to PLGA group, PLGA/periosteum group, PLGA/MSCs group, and PLGA/M SC s/periosteum group. Bone defect of 15 mm segment in length was established in the middle of the ulnar in rabbits of each group. PLGA, PLGA/periosteum, PLGA/MSCs, and PLGA/MSCs/periosteum were implanted in PLGA group, PLGA/periosteum group, PLGA/MSCs group, and PLGA/M SC s/periosteum group, respectively. After 6 and 12 weeks, the samples were evaluated with radiological and histological analysis. Results Compared with other treatment groups at each time point, a better bone quality, higher X-ray scores, and more bone mass were observed in PLGA/MSCs/periosteum group (P < 0. 05 ) . There was no significant difference ( P > 0. 05 ) between PLGA/periosteum group and PLGA/MSCs group in the X-ray score and bone mass，but the X-ray score and bone mass in PLGA/ periosteum group and PLGA/MSCs group were significantly higher than those in group PLGA (P < 0. 05). Conclusion The combined use of bone marrow mesenchymal stem cells and periosteum-coated PLGA significantly promotes the healing of large ulnar bone defect in rabbits. |