499 - Radiographic and Clinical Outcomes at 1 Year after Spinous Process Fix...

#499 Radiographic and Clinical Outcomes at 1 Year after Spinous Process Fixation and PLF in an Elderly Population

Lumbar Therapies and Outcomes

Poster Presented by: R. Tatsumi


R. Tatsumi (1)

(1) Pacific Spine Specialists, Tualatin, OR, United States


Background and Hypothesis: Interspinous Process (ISP) fixation for lumbar fusion has gained attention as a less invasive option for patients undergoing posterior lumbar fusion surgery for the treatment of degenerative disc disease, spinal stenosis, spondylolisthesis, and/or instability of the lumbar spine. Minimally invasive techniques have become of particular interest in the elderly population. Our hypothesis in this retrospective cohort study was that elderly patients undergoing decompression and posterior fusion with spinous process fixation would have clinically (at least a 15 point improvement as previously defined in the literature as the minimal clinically important difference) and statistically significant improvement in disability as measured by Oswestry disability index (ODI). Our secondary hypothesis was that posterior fusion rates with ISP fixation would be comparable to published rates for pedicle screw fixation.

Methods: A retrospective cohort study including all patients with at least 1 year follow up, with single level spinous process fixation for posterior lumber fusion was performed. Baseline and post operative ODI scores were collected as well as diagnosis, smoking status, and demographic data. A paired t-test with a type I error rate of 0.05 was performed to evaluate if ODI scores were reduced from baseline at 1 year and 2 years after surgery. Facet fusion and interlaminar posterior fusion rates were examined via upright, neutral and lateral, flexion and extension radiographs. The Lenke criteria and ≤ 2mm of motion were used to assess posterolateral fusion.

Results: 42 patients had baseline and 1 year ODI scores. 28 patients had two year ODI scores. One year fusion data was retrospectively available on 32 patients. All patients had a diagnosis of degenerative spondylolisthesis. The mean patient age was 72.7 years (SD=7.1). 43% were female. Mean baseline ODI was 50.9 (SD=12.3). Mean 1 yr ODI was significantly reduced by 24.7 points (95% CI=18.3-31.10, p=< 0.0001) from baseline and by 28.2 points (95% CI=20.4-35.9, p=< 0.0001) at 2 years. Facet fusion rate at 1 year (n=32) was 90.6%, and 91.3% at two years (n=23). Posterior/Interlaminar fusion rate was 84.4% at one year (n=32) and 82.6% at two years (n=23). This compares well to a recent meta analysis of posterior fusion rates with pedicle screw fixation which showed an average of 86% fusion in 124 patients across 3 studies.

Conclusions: In this elderly cohort, ISP fixation results in clinically and statistically significant improvement in ODI scores with a fusion rate comparable to rates previously published for pedicle screw fixation.