Prospective randomized evaluation of posterior lumbar interbody fusion in degenerative spondylolisthesis patients over 60 years old

Abstract

Scott H. Kitchel, MD, Richard E. Matteri, MD, Eugene, OR, USAAnterior column support in lumbar fusion has an important role in degenerative conditions of the lumbar spine. Its role in the form of a posterior lumbar interbody fusion (PLIF) has been supported for the treatment of degenerative spondylolisthesis by some authors. The results of simple decompression and posterolateral fusion for this disorder have been excellent. This study evaluates in a prospective randomized fashion the outcomes of these two procedures in a patient population over 60 years of age.Sixty-two patients with Grade 1/2 degenerative spondylolisthesis and accompanying spinal canal stenosis were randomized into one of two surgical groups after the failure of conservative treatment. Thirty-two patients received decompression and posterolateral fusion with pedicle screws and autologous graft (PL group). Thirty patients received decompression, posterolateral fusion with pedicle screws and autologous graft plus posterior interbody fusion with machined allograft (PLIF group). The only surgical variable was the addition of the posterior interbody fusion in the PLIF group. Patient demographics including age, sex, duration of symptoms and radiographic finding are reviewed and not statistically significantly different between groups. Follow-up was 24 months or greater in all patients averaging 32.6 months.Results are presented broken down into surgical variables (surgery time, blood loss, length of stay and complications) and outcomes (fusion, Oswestry disability index, Short Form [SF}-36 and visual pain analog scores). Surgery time (121 minute average [PL] versus 161 minute average [PLIF], p=.05), blood loss (470 cc average [PL] versus 820 cc average [PLIF], p=.01) and intraoperative complications (n=3 [PF] versus n=6 [PLIF], p=.05) were all statistically significantly greater in the PLIF group than the PL group. Length of stay was not different between groups.Fusion was assessed using flexion-extension radiographs and reconstructed computed tomography scans. Fusion was diagnosed in 28 of 32 patients (87.5%) in the PL group and 26 of 30 patients (86.7%) in the PLIF group. These were not statistically significantly different. Oswestry disability index improvement of 15% or more occurred in 26 of 32 patients (81.2%) in the PL group and 24 of 30 patients (80%) in the PLIF group. SF-36 scores and visual pain analog scores improved in both groups with no statistically significant differences between groups.The results show no difference in outcomes with the addition of a PLIF in degenerative spondylolisthesis (Grade 1/2) for patients over 60 years of age but significantly longer surgery time, higher blood loss and higher complication rates in this group. Based on this, the authors do not believe PLIF with allograft is indicated in patients over 60 years of age with Grade 1 or Grade 2 degenerative spondylolisthesis.