A Study Comparing Fusion Rates of Two Lumbar Fusion Procedures

Inclusion Criteria: * Adult 18 years of age or older * Male or female subject that had previously received the transsacral two-level procedure when used in conjunction with pedicle screw or facet screw fixation or TLIF two-level procedure with unilateral or bilateral supplemental screw fixation (e.g. pedicle screws, facet screws at L4-L5-S1 to treat pseudoarthrosis, spinal stenosis, spondylolisthesis, or degenerative disc disease (DDD) * Subject that was treated no less than 2 years prior to this evaluation with an transsacral or TLIF procedure by the participating surgeons * Subject that had a diagnosis that required a transsacral or TLIF procedure at the L4-L5-S1 levels and did not require treatment at any other lumbar levels at the time of surgery Exclusion Criteria: * Subject who did not receive the transsacral or TLIF procedure for fusion of L4-L5-S1 * Subject who received lumbar fusion procedures at levels other than L4-L5-S1 at the time of surgery