![]() The repair stage is the point at which fibroblasts lay down a stroma that supports vascular ingrowth. 29 The result is a formulation of granulation tissue, vascular ingrowth, and migration of mesenchymal cells. 35 During the inflammatory stage, which encompasses the first week of bone healing, a hematoma develops with subsequent infiltration of fibroblasts and inflammatory cells such as macrophages, monocytes, lymphocytes, and polymorphonuclear cells. Bone healing occurs in three stages the early inflammatory stage, the repair stage, and the late remodeling stage. The mechanism by which a spinal arthrodesis occurs is very similar to the healing of long bone fractures via secondary bone healing except for the fact that a bone graft is used in spinal fusion. To understand how smoking affects the process of bone healing in a spinal fusion, it is first crucial to understand how a healthy bone fusion heals. 26 This correlation was demonstrated to an even greater degree than patients with hip or long bone fractures, suggesting that smoking may have a greater weakening effect on vertebral bone than other parts of the skeleton. were able to show that smoking significantly increased the risk of a lumbar spinal fracture. The cumulative effect of all of these changes is to increase bone resorption and decrease bone formation. In these patients, levels of estrogen are low to begin with, and smoking decreases estrogen levels further. In addition, downregulation of estrogen is responsible for decreased bone density, especially in post-menopausal women. Inhibition of calcitonin is also a contributing factor to decreased bone formation. 28 Cortisol has also been shown to downregulate the synthesis of collagen. 14- 27 By increasing the levels of cortisol in the body, smoking decreases bone formation by inhibiting periosteal cell proliferation. 13 Smoking increases cortisol, causes estrogen imbalance, kills osteoblasts, impedes calcitonin, decreases oxygen supply, and decreases calcium absorption. Due to its osteoporotic effects, smoking causes increased vertebral and endplate porosity and decreased trabecular thickness. Smoking causes changes in vertebral bone that result in conditions requiring surgical intervention with spinal arthrodesis. Recommendations are made regarding the time frame of smoking cessation and other therapies that may improve outcomes in patients who continue to smoke. ![]() Smoking’s effects on fusion rate are also wide-ranging and depend on many factors, including the type of arthrodesis procedure, spinal location and number of levels of the procedure, and type of graft used among other variables. The molecular effects range from inflammatory mediators and other cytokines to osteoinductive proteins and extracellular matrix components. To fully appreciate these effects, it is first necessary to understand how smoking affects vertebral bone, the biology of how fusions heal, and how smoking affects this process at the level of gene expression. Smoking influences spinal fusion surgical outcomes in many ways. With a full understanding of the systemic and local effects of smoking and their influence on specific complications associated with spinal fusion surgery, surgeons can be better prepared to devise customized treatment plans for patients and explain to patients how smoking affects their surgical outcomes. 3 This article provides a comprehensive and updated review of how smoking affects spinal fusion surgery, including the effect on the rate of fusion success and associated complications, as well as recommendations on how to minimize or eliminate the negative effects of perioperative smoking. ![]() In addition to being a well-established risk factor for a variety of medical conditions such as hypertension, coronary artery disease, cancer, and hyperlipidemia, smoking has deleterious effects on the spine and musculoskeletal system. One of the most prevalent of these co-morbidities is cigarette smoking. 2 There are a number of risk factors and co-morbidities that have the potential to negatively influence the outcome of the procedure. 1 It is an effective method for reducing pain, increasing stability, and correcting deformity in patients with conditions such as spondylolisthesis, spinal stenosis, tumors, vertebral fractures, scoliosis, kyphosis, and other degenerative disc diseases causing myelopathy and radiculopathy, among other symptoms. Spinal arthrodesis (fusion) surgery is performed about half a million times per year in the United States and millions more worldwide.
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