Bone Grafting

Gregory J. Zipfel, MD, Bernard H. Guiot, MD, Richard G. Fessler, MD, PhD

Disclosures

Neurosurg Focus. 2003;14(2) 

In This Article

Abstract and Introduction

Abstract

In recent years our understanding of spinal fusion biology has improved. This includes the continued elucidation of the step-by-step cellular and molecular events involved in the prototypic bone induction cascade, as well as the identification and characterization of the various critical growth factors governing the process of bone formation and bone graft incorporation. Based on these fundamental principles, growth factor technology has been exploited in an attempt to improve rates of spinal fusion, and promising results have been realized in preclinical animal studies and initial clinical human studies. In this article the authors review the recent advances in the biology of bone fusion and provide a perspective on the future of spinal fusion, a future that will very likely include increased graft fusion rates and improved patient outcome as a result of the successful translation of fundamental bone fusion principles to the bedside.

Introduction

Spinal fusion is a critical element in many spinal procedures. The incidence of nonunion ranges from 5 to 35%,[7,8,20,38] and failed spinal fusions are a significant contributor to the morbidity associated with spinal surgery. In recent years our understanding of spinal fusion biology has improved, including the identification and characterization of various local and systemic growth factors. This argues well for improved spinal fusion rates in the future. Investigators of recent in vivo studies have shown the utility of this growth factor technology in multiple spinal fusion models,[3,24,32,34] thus underscoring its bright future.

The aim of this article is to describe and illustrate the chronology of events occurring during the incorporation of bone grafts into a stable spinal fusion. First, the crucial topics of bone formation, bone graft physiology, and typical bone graft options are reviewed. Second, the step-by-step cellular and molecular events involved in the prototypic bone induction cascade are delineated. Third, a lumbar spinal fusion animal model is sequentially described, illustrating the bone induction cascade as it relates to the clinically relevant setting of spinal fusion. Finally, conclusions are drawn regarding the potential application of bone fusion principles, particularly the use of growth factors, in the clinical setting of spinal fusion.

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