Objectives: The surgical approach that should be used for degenerative spondylolisthesis (DS) is a controversial issue. Decompression and posterolateral fusion (PLF) with or without lumbar interbody fusion is widely used. Many studies have compared the outcomes of these 2 approaches, but the appropriate indications for these approaches are still unclear. The authors retrospectively studied the effects of posterior lumbar interbody fusion (PLIF) after PLF for the treatment of DS.
Methods: Forty patients who underwent single level decompression and posterior instrumentation for DS at L4-5 and were followed for at least 2 years were retrospectively studied. The patients were divided into 4 groups: the stable PLF group (S-PLF, n=13); the stable PLF with additional PLIF group (S-PLIF, n=11); the unstable PLF group (U-PLF, n=8); and the unstable PLF with additional PLIF group (U-PLIF, n=8). Clinical and radiographic comparisons were carried out between the S-PLF and S-PLIF groups, and between the U-PLF and U-PLIF groups.
Results: Clinical assessments, using the improvements of the Oswestry Disability Index (ODI) and the Visual Analog Scale (VAS), were statistically significantly different between the 2 unstable groups (DeltaU-PLF <DeltaU-PLIF, P(ODI)=0.032, P(VAS)=0.004, respectively). On radiologic assessment, the slip angle increment was significantly different between the 2 stable groups (DeltaS-PLF>DeltaS-PLIF, P=0.029), and the disc height increment was significantly different between the 2 stable groups (DeltaS-PLF<DeltaS-PLIF, P=0.043) and between the 2 unstable groups (DeltaU-PLF<DeltaU-PLIF, P=0.042).
Conclusions: This study suggests that preoperative segmental instability may be a criterion determining whether an additional PLIF would be beneficial in the treatment of lumbar DS.