Degenerative lumbar spinal stenosis: analysis of results in a series of 374 patients treated with unilateral laminotomy for bilateral microdecompression

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Surgical decompression is the recommended treatment in patients with moderate to severe degenerative lumbar spinal stenosis (DLSS) in whom symptoms do not respond to conservative therapy. Multilevel disease, poor patient health, and advanced age are generally considered predictors of a poor outcome after surgery, essentially because of a surgical technique that has always been considered invasive and prone to causing postoperative instability. The authors present a minimally invasive surgical technique performed using a unilateral approach for lumbar decompression.


A retrospective study was conducted of data obtained in a consecutive series of 473 patients treated with unilateral microdecompression for DLSS over a 5-year period (2000–2004). Clinical outcome was measured using the Prolo Economic and Functional Scale and the visual analog scale (VAS). Radiological follow-up included dynamic x-ray films of the lumbar spine and, in some cases, computed tomography scans.


Follow-up was completed in 374 (79.1%) of 473 patients—183 men and 191 women. A total of 520 levels were decompressed: 285 patients (76.2%) presented with single-level stenosis, 86 (22.9%) with two-level stenosis, and three (0.9%) with three-level stenosis.

Three hundred twenty-nine patients (87.9%) experienced a clinical benefit, which was defined as neurological improvement in VAS and Prolo Scale scores. Only three patients (0.8%) reported suffering segmental instability at a treated level, but none required surgical stabilization, and all were successfully treated conservatively.


Evaluation of the results indicates that unilateral microdecompression of the lumbar spine offers a significant improvement for patients with DLSS, with a lower rate of complications.

Abbreviations used in this paper:AP = anteroposterior; CT = computed tomography; DLSS = degenerative lumbar spinal stenosis; LF = ligamentum flavum; VAS = visual analog scale.

Article Information

Address correspondence to: Francesco Costa, M.D., Via R. Galeazzi 4, 20100 Milan, Italy. email:

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Computer renderings. A: View of the V-shaped thinning of the superior lamina created with microdrill. B: Elevation of LF by means of dissectors and biopsy forceps, creating a neat cleavage plane with the dural layer. C: View after ipsilateral decompression of dural sac and radicular recess. D: Final view after decompression of dural sac and both nerve roots.

  • View in gallery

    A: Preoperative CT scan showing that the transverse diameter is congenitally reduced, with the consequent vertical position of the osseous canal roof. B: Computer-generated image showing the working angle of the microscope, which facilitates decompression of the contralateral LF and bone decompression (blue). C: Postoperative control CT scan. D: Preoperative CT scan revealing that the AP diameter of the spinal canal is congenitally reduced, with the horizontal position of the osseous canal roof. E: Computer-generated image showing the different working angle of the microscope (blue) required in this case to accomplish adequate contralateral decompression. F: Postoperative control CT scan.

  • View in gallery

    Axial CT scans. A and B: Preoperative and postoperative images of lumbar stenosis caused by purely hypertrophic changes of the LF. C and D: Preoperative and postoperative images of lumbar stenosis caused by marked hypertrophic bone spurs arising from the facet joints and impinging on the dural sac. E and F: Preoperative and postoperative images of lumbar stenosis caused by the combined narrowing of the canal arising from LF hypertrophy and/or calcification and osteophytic spurs.

  • View in gallery

    Representative radiographic studies. A and B: Preoperative dynamic flexion/extension x-ray films showing no evidence of segmental instability at L4–5. C and D: Postoperative dynamic flexion/extension x-ray films demonstrating mild segmental instability.



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