Biomaterials for vertebral body repair: interior augmentation and total replacement-a literature review of bone fusion outcomes in clinical studies.

Background and Objective: Vertebral body repair comprises surgical procedures aimed at restoring height and stability of injured vertebrae, thereby re-establishing spinal structural integrity and load-bearing function. Bone fusion and biomaterial incorporation or integration are key determinants of long-term clinical outcomes, providing biological stability. The ideal biomaterial for vertebral body repair remains undefined. Despite the increasing number of available materials, achieving an optimal balance between mechanical load-bearing capacity and biological potential for progressive bone substitution-key requirements for restoring spinal biomechanics-remains a major challenge. Therefore, this narrative review examines biomaterials used in vertebral body repair, with emphasis on bone fusion outcomes. Methods: A literature review of MEDLINE/PubMed was performed using two separate searches: one on vertebral body augmentation and another on total vertebral body replacement. Original clinical studies involving the mobile spine reporting bone fusion outcomes were included, whereas studies with unclear methods for assessing bone healing were excluded. Key Content and Findings: Among the vertebral augmentation fillers analyzed, the most notable were bioactive bone cements, including calcium phosphate (16 studies), calcium sulfate (6 studies), and composite cements (3 studies). Regarding total vertebral body replacement, the most commonly reported implants were titanium mesh cages (85 studies), with bone fusion rates (BFRs) of 70-100%, and expandable titanium cages (58 studies), with BFRs ranging from 23.5% to 100% across various conditions. Other notable materials included bioactive ceramics (4 studies, 95-100%), carbon fiber (3 studies, 80-97.5%), thermoplastic polymers (8 studies, 70-100%), and carbon fiber-reinforced polymers (CFRPs) (2 studies, 100%). Porous metallic static cages (8 studies) exhibited BFRs of 76.9-100%, whereas nanohydroxyapatite/polyamide-66 (HA/PA66) cages (13 studies) showed BFRs ranging from 72.7% to 100%. Benefits and limitations of each biomaterial used in vertebral body repair were summarized and discussed. Conclusions: Current biomaterials for vertebral body repair demonstrate high BFRs; however, challenges remain concerning mechanical load-bearing capacity and biological interactions, including their potential for progressive bone substitution. Composite biomaterials that combine the most desirable properties of multiple materials represent promising solutions. Future studies on the development of optimal biomaterials are essential to achieve accurate vertebral body reconstruction from both biomechanical and biological perspectives.