This postmarket surveillance study is being conducted to evaluate the TRANSITION Stabilization System as an adjunct to fusion in the treatment of acute or chronic instabilities or deformities of the thoracic, lumbar and sacral spine. The study will involve up to 360 subjects at no more than 20 sites, to be treated with the TRANSITION Stabilization System. The data from this postmarket surveillance study will be provided to FDA in accordance with the 522 order.

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