• To determine whether the addition of transpedicular instrumentation improves the clinical outcome and fusion rate of patients undergoing posterolateral fusion after decompression for spinal stenosis with concomitant degenerative spondylolisthesis

This prominent historical study by Fischgrund et al published in 1997, was a well-controlled randomized trial looking at both clinical and radiographic outcomes of lumbar laminectomy with arthrodesis surgery in patients with degenerative spondylolisthesis and spinal stenosis.

Patients in this study (N=68) were randomly assigned to two treatment groups; Lumbar laminectomy with posterolateral intertransverse process arthrodesis or lumbar laminectomy and arthrodesis with instrumentation.   Clinical outcomes were based on commonly utilized criteria to classify results as excellent, good, fair or poor. Radiographic outcomes (fusion status) was based on the presence of continuity of fusion mass between cephalad and caudad transverse processes.

While the clinical and radiographic outcomes can be viewed with some degree of subjectivity, the methodology of the study was bolstered by the fact that the final examiners who determined outcome were not the surgeon. Furthermore, the radiographs were reviewed by two independent orthopaedic surgeons.

The results of the study showed that while the radiographic results heavily favored the instrumented fusion group (83% vs 45%), clinical outcomes were not superior in this group.   Eighty-five (85%) percent of the patients in the non-instrumented fusion group had an excellent or good clinical outcome compared to 78% in the instrumented group.

The study materials and methods section does note the average age of patients in both groups (69 yrs. for instrumented group vs. 66 for non-instrumented group) and states that there were 7 (10.3%) patients who were smokers, but  no further analysis of these potential confounders is made.  If these 7 patients were removed from the radiographic analysis, it is unlikely that the overall fusion rates would change significantly in each group, however, the overall point estimate of fusion may differ.

In a more recent retrospective study by Nayak MT and Sannegowda RB (2015) a cohort of 56 patients was analyzed who underwent laminectomy and posterolateral fusion with instrumentation for spinal stenosis and degenerative spondylolisthesis. At 6 months post-op, 53 patients had achieved a bony fusion, whereas 3 had a pseduoarthrosis.  Those that achieved a solid fusion scored better in the category of postoperative satisfaction.  As noted by the authors, all patients noted significant pain reduction and clinical improvement which seems to be independent of fusion status at least in the short term.   One major concern with this study is that smoking was not controlled for.

Another recent study (Ghogawala Z et al 2016) looked at whether lumbar laminectomy with instrumentation fusion would benefit patients more than laminectomy alone. Oswestry Disability Index (ODI) scores at two years post-operative improved to a greater degree in the fusion group. There was a slightly greater by clinical meaningful in physical health-related quality of life for those who underwent an instrumented fusion. Despite these findings, the higher costs associated with an instrumented fusion may not be justified when compared to decompression alone for those with single level spinal stenosis with degenerative spondylolisthesis.