Spinal fusions: bone and bone substitutes.

Vertebral arthrodesis is one of the most commonly performed, yet incompletely understood, procedures in spinal surgery. Despite major progress in internal fixation techniques, the high rate of nonunions indicates that physiologic, biologic and molecular events that are crucial to this process are not well known. This article will analyze the general biology of bone regeneration, and particularly discuss the properties and use of various bone graft materials and graft substitutes.