This trial aims to investigate the effect if any, of the patient's own bone marrow stem cells quadriplegic patients. The trial is being conducted at General Hospital of Chinese People's Armed Police Forces in Beijing and seeks to enrol 40 patients who have had C4-6 level complete quadriplegia for at least one year. Participants will be divided into an experimental group who will receive mesenchymal stem cells obtained from their own bone marrow by an open surgical transplantation. The other participants will receive no intervention. Participants will be monitored for complications and changes in their condition, including bladder function. This institute has also conducted a similar trial (ChiCTR-ONC-12002005) in paraplegics.