Pharmacophysiology of bone and spinal fusion.

Background Context: In recent years, the number of complex spinal surgeries has increased significantly in the elderly population, where the prevalence of low bone density is highest. Consequently, spine surgeons often treat osteoporotic patients who are associated with higher rates of instrumentation failure. Therefore, establishing a successful fusion requires an appropriate substrate for bone formation and local bone remodeling. The fusion process can be supported by therapies that seek to shift the balance of bone homeostasis to increased formation and reduced resorption.

Purpose: Thorough understanding of the physiology of bone formation and adjunctive therapies can help improve fusion rates. Therefore, we present a thorough review of the latest pharmacologic agents used to enhance bone strength and surgical spinal fusion.

Methods: Systematic review of literature.

Results: Current knowledge on bone physiology has led to the development of several pharmacologic agents that enhance bone formation and strengthen the human skeleton. At present, natural supplements of vitamin D and calcium or synthetic medications like bisphosphonates are widely used before and after spine surgeries to enhance bone fusion. Additional physiologic agents, including testosterone, parathyroid hormone, calcitonin, and growth hormone, have been shown to improve bone mass density or spinal fusion in both animal and human studies. As in other medical fields, gene therapy has shown viability and promise with the use of both viral and nonviral vectors.

Conclusions: Through the understanding of bone physiology, numerous natural and synthetic pharmacologic agents have been developed to enhance the body's skeleton and to improve outcomes of spinal fusion surgery.