The purpose of this study is to demonstrate the relative efficacy of two lumbar fusion procedures: transacral lumbar interbody fusion when used in conjunction with unilateral or bilateral posterior pedicle screw fixation as an adjunct to fusion, in comparison to transforaminal lumbar interbody fusion (TLIF) when used in conjunction with unilateral or bilateral supplemental screw fixation as an adjunct to fusion.

Subject candidates are those who had previously required and received fusion at L4-L5-S1 where these were the only lumbar levels treated for pseudoarthrosis, spinal stenosis, spondylolisthesis, or degenerative disc disease (DDD).

Consecutive subjects who were treated with the transsacral lumbar interbody fusion or TLIF procedures at least 2 years prior to the date the data is collected will be evaluated.

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

Subject candidates are those who had required fusion at L4-L5-S1 where these were the only lumbar levels treated for pseudoarthrosis, spinal stenosis, spondylolisthesis, or degenerative disc disease (DDD).