20. participation in another investigational study within 30 days *Osteoporosis will be assessed at the time of the preoperative evaluation based on the patient‟s history, physical examination and review of the radiographic evaluations. All patients at risk for osteoporosis must obtain a DEXA scan of the spine and hip to determine if the patient has severe osteoporosis. The definition of a patient at risk used by the National Osteoporosis Foundation includes the following: i. Premature menopause (< 45 years) ii. Prolonged amenorrhea (> one year) iii. Maternal history of hip fracture iv. Primary hyperparathyroidism or hyperthyroidism v. Chronic renal failure vi. Previous fragility fractures, particularly of the hip, spine or wrist vii. Patients who have ever taken corticosteroids in doses >7.5 mg/day for one year or more. Patients will be excluded if their bone mineral density (BMD) in the spine or hip is more than 1.0 standard deviation (SD) below the mean of normal adults in the presence of one or more fragility fractures indicating severe osteoporosis. If severe osteoporosis is diagnosed, the patient must be excluded from the investigational study. If the patient has osteoporosis or osteopenia, they may be included in the study if he or she meets the rest of the inclusion and exclusion criteria.