Severe Spondylolisthesis in Adolescence. Treatment by Reduction or Fusion In SITU. – Long-term Clinical, Radiological and Functional Outcome

Summary: A retrospective comparison of two matched cohorts of high-grade spondylolisthesis was performed. Eleven patients underwent circumferential fusion in situ and eleven patients were reduced with transpedicular device and fused circumferentially. Long-term follow-up revealed that fusion in-situ group performed better in almost all measured clinical parameters.

Introduction: In severe isthmic spondylolisthesis, in-situ fusion is usually performed, but modern surgical techniques and instrumentation allow the reduction of a severely slipped fifth lumbar vertebra. No long-term results of the reduction maneuver exist. We aimed to assess long-term effects of reduction vs. fusion in-situ on lumbar spine in young patients with severe isthmic spondylolisthesis.

Methods: 22 adolescents with severe (>60%) slip were surgically treated. 11 were reduced with Magerl/Dick transpedicular device and fused posteriorly from L4 or L5 to S1 and anteriorly L5-S1. The other 11 were fused in-situ posteriorly from L4 (n=7) or L5 (n=4) to S1 and anteriorly L5-S1. Radiographs were obtained preoperatively, postoperatively and at the final follow-up. MRIs were obtained at the final follow-up visit. Outcome was assessed at the last follow-up by physical examination, spinal mobility and non-dynamometric trunk strength measurements, and Oswestry Disability Index (ODI) and Scoliosis Research Scores (SRS) scores.

Results: Mean ODI was 7.2 (range, 0-20) in the reduction, and 1.6 (0-4) in the fusion in-situ group (p=0.0096). The SRS total score averaged 90.0 (range, 39-107) in the reduction group and 103.9 (93-120) in the in situ fusion group (p=0.046). In the reduction group, mean vertebral slip was reduced from preoperative 90% to 57% at the last follow-up. Corresponding values were 80% and 78%, respectively, in the in situ fusion group. In MR images, disc degeneration was more common in the reduction group (p=0.004). None of the patients had spinal stenosis above fusion. Nerve root canal impingement at L5-S1 level was more common in fusion in-situ group (p=0.03), but all patients were free of radicular symptoms. There was no difference in spinal mobility and trunk strength measurements between groups.

Conclusions: Fusion in-situ group seem to performed better almost in all measured clinical parameters. Based on these findings, in-situ fusion must be considered as a method of a choice in severe L5 isthmic spondylolisthesis.