A Prospective Randomized Postmarket Clinical Study of the TRANSITION Stabilization System

Inclusion Criteria: * Any of the following acute or chronic instabilities or deformities of the thoracic, lumbar or sacral spine: * degenerative spondylolisthesis with objective evidence of neurologic impairment, * kyphosis, or * pseudoarthrosis (failed previous fusion) * Age 18 or older at the time of consent * Able to understand and sign informed consent form * Psychosocially, mentally and physically able to comply with protocol * Able to meet the proposed follow-up schedule at 6 mo, 12 mo, and 24 mo Exclusion Criteria: * Prior fusion surgery or another spinal device implanted in the thoracic, lumbar or sacral spine * Requires treatment of more than two vertebral levels * Lytic spondylolisthesis at the index level(s) * Clinically compromised vertebral bodies at the affected level(s) due to current or past trauma * Sustained pathologic fractures of the spine or hip, including prior fracture or trauma to vertebral structures at any thoracic, lumbar, or sacral level * Morbid obesity defined as a body mass index \> 40, or a weight more than 100 lbs over ideal body weight * Pregnant or interested in becoming pregnant within the next 2 years * Active systemic or local infection * Known allergy to device materials titanium, polycarbonate (PCU), polyethylene terepthalate (PET), or hydroxyapatite (HA). * Taking medications or any drug known to potentially interfere with bone/soft tissue healing (e.g., steroids, excluding routine NSAIDs) * Systemic disease including AIDS, HIV, Hepatitis C * Has an active malignancy defined as a history of any invasive malignancy (except non-melanoma skin cancer), unless he/she has been treated with curative intent and there has been no clinical signs or symptoms of the malignancy for at least 5 years * Neuromuscular disorders such as muscular dystrophy, spinal muscular atrophy, amyotrophic lateral sclerosis, etc. * Participation in an investigational device or drug clinical trials within 30 days of surgery * Acute mental illness or substance abuse * Prisoners