Erland Hermansen, Ivar Magne Austevoll, Christian Hellum, Kjersti Storheim, Tor Åge Myklebust, Jørn Aaen, Hasan Banitalebi, Masoud Anvar, Frode Rekeland, Jens Ivar Brox, Eric Franssen, Clemens Weber, Tore Solberg, Knut Jørgen Haug, Oliver Grundnes, Helena Brisby, Kari Indrekvam

September 2020, Volume 29, Issue 9, pp 2254 - 2261 Original Article Read Full Article 10.1007/s00586-020-06499-0

First Online: 18 June 2020


To investigate changes in dural sac area after three different posterior decompression techniques in patients undergoing surgery for lumbar spinal stenosis.

Summary of background data

Decompression of the nerve roots is the main surgical treatment for lumbar spinal stenosis. The aim of this study was to radiologically investigate three commonly used posterior decompression techniques.


The present study reports data from one of two multicenter randomized trials included in the NORDSTEN study. In the present trial, involving 437 patients undergoing surgery, we report radiological results after three different midline retaining posterior decompression techniques: unilateral laminotomy with crossover (UL) (n = 146), bilateral laminotomy (BL) (n = 142) and spinous process osteotomy (SPO) (n = 149). MRI was performed before and three months after surgery. The increase in dural sac area and Schizas grade at the most stenotic level was evaluated. Three different predefined surgical indicators of substantial decompression were used: (1) postoperative dural sac area of > 100 mm2, (2) increase in the dural sac area of at least 50% and (3) postoperative Schizas grade A or B.


No differences between the three surgical groups were found in the mean increase in dural sac area. Mean values were 66.0 (SD 41.5) mm2 in the UL-group, 71.9 (SD 37.1) mm2 in the BL-group and 68.1 (SD 41.0) mm2 in the SPO-group (p = 0.49). No differences in the three predefined surgical outcomes between the three groups were found.


For patients with lumbar spinal stenosis, the three different surgical techniques provided the same increase in dural sac area.

Clinical trial registration

The study is registered at reference on November 22th 2013 under the identifier NCT02007083.

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