The present invention relates to an implantable vertebral arthrodesis device (1) for fusing an overlying vertebra and an underlying vertebra, the device comprising an anterior portion (2) having upper and lower bearing zones (2a, 2b) suitable respectively for receiving lower and upper portions (3, 6) of upper and lower laminae (4, 7) of the overlying and underlying vertebrae (5, 8), said zones (2a, 2b) being spaced apart by a minimum height h (h1) for maintaining intervertebral spacing； rigid retaining devices (9) arranged relative to the anterior portion (2) so as to block migration of said anterior portion (2) towards the spinal canal； a posterior portion (10) in connection with said anterior portion (2), including a main housing (11) having first and second openings (11a, 11b) facing each other and suitable for receiving in part the spinous processes (12, 13)； and a granular osteosynthesis material arranged in said main housing (11).
