Anterior Cervical Spine Fixation: Material Technologies

New technologies have sought to address the deficiencies of autografts and allografts used over the past 40 years. Initial bone graft replacements involved titanium spacers. Titanium is stronger than bone and is easy to work with. Hard titanium can press against the soft adjacent bone and cause the bone to collapse. Additionally, when MRI and CT scans are done after surgery, titanium produces an artifact making image interpretation more difficult.

These problems led to the development of polymer interbody replacements. The most commonly available polymer is polyetheretherketone (PEEK). The PEEK graft replacements are stronger than bone but they are softer and less likely to cause the adjacent bone to collapse. (8) Additionally, the polymer is virtually invisible to CT scans and MRI, allowing for easier postoperative film interpretation and fusion assessment. We have used a PEEK interbody spacer extensively in anterior cervical fusions with excellent results.

Figure 1. Preoperative X-ray demonstrating cervical kyphosis and severe degenerative changes.

Figure 2. Preoperative MRI demonstrating multiple disc bulges and cervical kyphosis.

Figure 3. Postoperative lateral x-ray after a four level anterior cervical discectomy with PEEK interbody spacer.

Figure 4. Postoperative anterior-posterior x-ray.

Recent advances have led to the development of bioabsorbable interbody devices. (9, 10) Hydrosorb™ (MacroPore Biosurgery, Inc.) is a substance that is absorbed by the body over the course of months. A Hydrosorb™ interbody device maintains the disc height for several months until a solid fusion occurs and eventually the interbody device is completely absorbed by the body.