Unanticipated study design flaw; PCO evaluator interrater reliability was not performed.

The purpose of this study is to compare the physical capability outcomes of patients who undergo single-level ProDisc-L disc replacement with those of patients who undergo stand-alone, single-level anterior lumbar interbody fusion (ALIF). This study will be the first multi-center clinical study to use clearly measurable outcomes from physical tests to compare the results of lumbar disc arthroplasty with disc fusion.

Physical capability testing will be conducted once before surgery and at 6 months and 1 year after surgery. Physical capability testing assesses the ability to perform a number of common tasks: the distance a subject can walk comfortably in 6 minutes; the amount of weight a subject can lift, push, pull, and carry; and the ability to squat and work bending forward in the kneeling and standing positions. The results of this testing will be evaluated to determine whether the subject's physical capability meets the physical requirements of their job, based on their responses to a pre-study questionnaire. Each physical capability testing session will require from 1 to 1 ½ hours of the subject's time. Physical capability testing will be provided without charge.

Inclusion Criteria:

Eligible patients will meet the following criteria based on clinically appropriate criteria per standard of care at individual institutions which may include but are not limited to

• skeletally mature; BMI < 40
• suffered from low-back pain with or without leg pain for 6 months or longer
• no evidence of spinal deformity on plain radiograph
• no evidence of angular instability on flexion extension radiographs
• severe and incapacitating low-back pain, defined as a score of 40% or greater on the Oswestry Disability Questionnaire
• a single level of degenerative disc disease at L34, L45, or L5-S1 on magnetic resonance imaging (MRI) scan
• discography, if indicated, reproduces pain at the level of degeneration noted on the MRI scan and is negative for pain reproduction at adjacent levels
• bone mineral density T-Score by DEXA Scan >-1.0 for any skeletal region
• computed tomographic (CT) scan demonstrates the absence of pars defect at the index level
• CT scan demonstrates the absence of significant facet arthropathy at the index level
• considered reasonable candidates for surgery in regard to psychological factors as determined according to the standard of care at each participating center

Exclusion Criteria:

• active systemic infection
• evidence of alcoholism
• spondylolisthesis of greater than grade 1
• clinically significant lumbar spinal stenosis
• allergy to implant materials
• isolated radicular syndrome
• vertebral body compromised by trauma at the index level.

The target study population are those meeting all the FDA criteria for ProDisc-L. Patients with third-party coverage for ProDisc-L that received surgical implantation of this device will be in one group. Patients without third-party coverage for ProDisc-L that underwent stand-alone ALIF with a device that incorporates fixation of the superior vertebral body to the inferior vertebral body, and where an osteoinductive biologic agent is placed within the device will be in the other group.