[Use of bone graft replacement in spinal fusions]

The rationale for the increasing use of bone graft replacement lies in the need for increased graft volume, the avoidance of typical autograft donor site morbidity, and the potential improvement of fusion rates in revision and complex reconstructive surgery.

The purpose of this work is to offer the spinal surgeon an evidence-based guide for choosing the appropriate grafting material and for using it effectively.

Evidence-based overview of physical and biological properties, clinical indications and results of osteoconductive and osteoinductive bone replacement materials.

The ideal bone replacement material should be osteoinductive and conductive, non-pathogenic, minimally antigenic, and (if required) mechanically stable. Compared to autograft, vascularization and remodeling of the fusion mass are delayed using allograft. Allogenous bone and demineralized bone matrix (DBM) possess limited osteoinductive properties and carry the risk of potential infectious disease transmission. Plasma-rich plasma (PRP) and bone marrow aspirate are commonly used in conjunction with an osteoconductive carrier materials. On-label use of bone morphogenetic proteins (BMPs) is currently restricted to mono- and bisegmental anterior lumbar fusion. The fusion rates obtained with BMPs match those of autologous bone graft. Potential risks of rhBMP in clinical use include soft tissue reactions, radiculitis and potentially increased risk of cancer. Osteoconductive ceramics (HA, CC, CS, ß-TCP) are useful graft extenders and carriers for bone growth enhancers and antibiotics.

Osteoconductive bioceramics with different mechanical and biological properties are available for use as graft extenders. In a defined group of anterior interbody fusion procedures (ACDF, ALIF), satisfactory fusion rates (> 90%) may be obtained with exclusive use of graft extenders, whereas their solitary use in posterolateral fusions is not advisable. Genuine bone replacement is currently feasible with BMPs. Their use should be restricted to specific indications such as complex revision surgery and pseudarthrosis.