Since anterior cervical discectomy and fusion with instrumentation (ACDFI) was first applied, it was considered a standard surgical procedure for degenerative and traumatic cervical diseases. However, clinical efficacy is closely related to the efficacy of intraoperative decompression and postoperative intervertebral fusion.[7] To achieve satisfying intervertebral fusion, it is crucial to select a suitable interbody fusion material. The commonly used materials mainly include autologous iliac bone, allogeneic bone, and synthetic materials. The autologous iliac bone is the material with the highest bone fusion rate, but additional incision is required and donor site complications cannot be avoided; the allogeneic bone has high expenses and incidence of bone graft-related complications. A cage filled with allogeneic bone or synthetic materials could avoid those disadvantages, but the bone fusion rate and the reliability are controversial.[8, 9]
In 2000, a prospective, randomized, multicenter clinical study focusing on the use of the cervical Spine Cage was published on the Spine, the intervertebral cage was then widely used in ACDFI.[10] The innovation and improvement of the intervertebral cage greatly enhanced the development of ACDFI, The type of intervertebral cage included stainless-steel cage, titanium alloy cage, and PEEK Cage.[11] PEEK cage has good biomechanical properties, and its elastic modulus is close to the vertebral body, the height of intervertebral space can also be maintained effectively. Meanwhile, PEEK Cage has the advantages of X-ray penetrability, and its hollow design can be filled with bone graft material to improve the fusion rate.[12]A lot of research articles on PEEK Cage were published and it was reported to achieve promising results in ACDFI, which is now the most popular intervertebral fusion material.[13]
The ideal PEEK Cage-filled bone grafting materials should be excellent in conductivity, induction, and osteogenesis of bone, moreover, the materials should be convenient and cheap.[14] Autologous bone is currently recognized as an ideal bone graft material. It has been reported that the intervertebral fusion rate of single-segment ACDFI using cortical iliac bone-filled PEEK Cage was over 95%, and the improvement rate of neurological symptoms was close to 80%.[15, 16] However, an additional surgical incision is needed, postoperative complications such as pain, bleeding, infection, disruption of femoral lateral cutaneous nerve and ilioinguinal nerve, and fracture of iliac frequently occurred.[17, 18] It was reported that the incidence of donor-site related complications ranged from 9.4–49%.[16, 18] The clinical applications of allogeneic bone, artificial bone, and other materials are limited due to their high price and low fusion rate.
The osteophytes extracted from local bites during anterior surgical decompression can be used as filling materials, but their clinical efficacy is limited. It was difficult to completely remove the soft tissue and fibrous tissue attached to the surface of osteophytes, the effect of bone graft fusion would be affected by the low levels of osteoblasts. Min et al conducted a study to compare the proliferation and ossification of bone marrow stem cells in autogenous vertebrae and autologous iliac bone, it was found that the proliferation and ossification of bone marrow stem cells were similar.[19] In this study, we used autogenous vertebrae as the bone graft material for the filling of the PEEK Cage. As is known from the anatomy of the cervical vertebral body, the lower endplate of the cervical vertebra is concave, while the anterior and lower margin of the vertebral body is lip-shaped. The degeneration of the intervertebral disc and the proliferation of osteophytes in the anterior margin of the vertebral body results in obvious narrowing of the vertebral space. To achieve sufficient decompression in the anterior and posterior intervertebral space and the vertebral canal, the osteophyte and the labial structure of the vertebral body were usually removed intraoperatively to expand the operative field. The anterior and posterior vertebrae of the upper and lower vertebral bodies are removed without causing significant damage to the upper and lower endplates, and the preparation of bone graft beds would also not be affected.
The clinical benefits of autogenous vertebrae mainly include: (1) No additional iliac bone extraction was performed during the operation, the operative time was significantly shortened; (2) The intraoperative blood loss was significantly fewer because no additional incision was needed; (3) Postoperative complications on donor site can be fully avoided; (4) The vertebral extracted from the body is convenient and cheap compared to the allogeneic bone; (5) At the 12-months follow-up, the bone fusion rate and functional outcomes were excellent, indicating that the autologous vertebrate filled PEEK Cage can achieve a satisfying clinical outcome.