Use of an Interspinous Device above the Level of Interbody Fusion: Does it Reduce the Worsening of Adjacent Segment Degeneration?

Abstract

Introduction Lumbar fusion in degenerative conditions has universally provided good results. However, adjacent segment degeneration, either afresh or worsening of a low grade degeneration in the segment above has been indicated for the pain and low functional outcome on long term follow-ups. Interspinous implants have been used to off load the facets and prevent spinal canal narrowing in stenosis with good results. This paper analyses the novel idea of using an interspinous device above the level of fusion to decelerate the physiologic process and reduce the incidence of adjacent segment degeneration (ASD). Material and Methods 12 patients were analyzed in the study. The inclusion criteria for the study was degeneration of the disc above the level of intended fusion with no or less than 50% disc height reduction and no nerve root compression. Patients with more than 50% height reduction or severe arthritic facet joints underwent fusion at two levels and were excluded from the study. Patients with failed back syndrome and significant osteoporosis were also excluded from the study. Coflex (Paradigm) interspinous device was used in the level above the fusion in all cases. Clinical and radiographic criteria for ASD was assessed at the latest followup. VAS and ODI functional outcome was analyzed. Results 12 patients with mean age of 63 years who underwent surgery between September 2012 and March 2014 were analyzed in the study. Mean followup was 27 months (Range 18–36 months). Single level fusion was performed in 9 cases and Two level fusion in 3 cases. Coflex device was implanted at L3–4 in 8 cases and L4–5 in 4 cases. All 12 patients had a good fusion in the 6 months radiograph. Disc height improvement was seen in the level above, with no evidence of stenosis or listhesis at the latest followup. Worsening of already existant ASD in one patient was noticed but did not require surgical intervention. VAS and ODI showed significant (p < 0.05) improvement postoperatively. No infection or reoperation was needed in any of the 12 patients. Conclusion ASD remains a significant reason causing failed back syndrome requiring reoperations in lumbar fusion. Use of interspinous device not only preserves a motion segment from fusion, but also shows promise in reducing the incidence of degeneration above the level of fusion. Further studies with larger sample size and long term followup is necessary to support the conclusion.