Anatomy and Physiology/Biology of Bone

Surgeons must have a clear understanding of anatomy and physiology; this is especially true when dealing with the distorted anatomy of revision surgery. The purpose of this chapter is to discuss the anatomy and physiology of the lumbar spine. This discussion includes potential anatomic variants, parameters of proper lumbar spine alignment, and how alignment influences load transmission. Bone biology is reviewed through the concept of Wolff’s law and by examining the interplay between osteoblasts and osteoclasts and how they regulate themselves to provide homeostasis. In addition, lumbar fusions are characterized by fusion type and approach, with further descriptions of instrumentation, graft material, and grafting areas of interest. Aspects of revision surgery are explored such as pain generators inside and outside the spine, and interbody removal. Continued pain and disability after lumbar fusion surgery is a challenging problem for both the patient and physician. A clear understanding of the anatomy and physiology is essential when searching for sources of pain in patients.