Background:

In posterior decompression for lumbar spinal stenosis, preservation of the posterior elements appears to provide patients with long-term favorable outcomes. To confirm this assumption, we evaluated the impact of spinous process integrity, i.e., osseous continuity between the spinous process and the lamina, on short to long-term outcomes.

Methods:

As a model for the study of spinous process integrity, we retrospectively reviewed the cases of forty-eight patients who underwent open-door laminoplasty using a spinous process-splitting approach without disrupting attachment sites of the multifidus muscle. In those patients, thirty-nine of the 103 spinous processes achieved spontaneous osseous union with the laminar flap, while the others did not achieve osseous union. The association between the number of ununited spinous processes, as well as baseline characteristics, and the outcomes were analyzed by primary and fully adjusted multivariate linear regression. Outcome measures were the Oswestry Disability Index (ODI) and a numeric rating scale (NRS) for symptoms at two, four, and ten to twelve years.

Results:

The number of ununited spinous processes was significantly associated with ten to twelve-year scores for the ODI (β = 0.24, p = 0.030), low back pain NRS (β = 0.32, p = 0.030), and leg pain NRS (β = 0.50, p = 0.0012) in the fully adjusted models, but was not associated with two or four-year scores for each scale. The number of decompression levels was significantly associated with ten to twelve-year scores for low back pain and leg pain NRS in the primary models, but was not retained in the fully adjusted models.

Conclusions:

Osseous continuity between the spinous processes and the lamina after posterior decompression of the lumbar spine is important for maintaining the positive surgical benefit. Deleterious effects of osseous discontinuity on the outcomes were obvious at ten to twelve years, but not at two or four years.