A Review of Strategies to Improve Biomechanical Fixation in the Cervical Spine

Abstract

Study Design Systematic review. Objectives Review the surgical techniques and construct options aimed at improving the biomechanical strength of cervical constructs. Methods A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A search of the MEDLINE, Embase, and Cochrane Library databases was performed to identify all studies examining biomechanical strategies utilized in the osteoporotic cervical spine. Screening was performed in duplicate for all stages of the review process. Results An initial search returned 3887 articles. After deletion of duplications and review of abstracts and full text, 39 articles met inclusion criteria. Overall, the surgical techniques reviewed aimed at obtaining rigid fixation in the setting of poor bone quality, or dispersing the forces at the bone-implant interface. We identified 6 key techniques to improve biomechanical fixation. These include bicortical fixation, appropriate screw selection (size and trajectory), PMMA augmentation, load sharing techniques, consideration of ancillary fixation around the occipitocervical junction, and supplementing the construct with post-operative collar or halo. Conclusion The summation of the literature highlights a framework of modalities available to surgeons to improve biomechanical fixation in the cervical spine. While these may improve construct strength in the setting of osteoporosis, there is a paucity of evidence available to make recommendations in this patient population.

Regional variations in C1–C2 bone density on quantitated computed tomography and clinical implications

“…The screw trajectory for an anterior odontoid screw stabilization extends from the anterior inferior C2 body near the disc space through the lower BMD bone found in the C2 vertebral body and incorporates the higher BMD within the odontoid as the screw projects toward the distal odontoid tip. This anterior odontoid screw trajectory for type II odontoid fractures goes through better bone quality and bone with higher BMD at the distal aspect giving a more secure construct and less chance of screw loosening [9] .…”

“…Osteoporosis is rarely discussed in cervical spine except in the context of revision surgery [7] , [8] , [9] . It is characterized by a decrease in bone density and an increase in fracture risk.…”