A randomized trial on three different minimally invasive decompression techniques for lumbar spinal stenosis. Five years follow-up from the NORDSTEN-SST.

Purpose: The short-term clinical outcome for midline-preserving posterior decompression techniques was comparable. The aim of this study was to evaluate long-term clinical results after three different midline-preserving posterior decompression techniques.

Material: In the NORDSTEN spinal stenosis trial (NORDSTEN-SST) 437 patients were randomized to three different midline-retaining posterior decompression techniques: Unilateral laminotomy with crossover (UL), bilateral laminotomy (BL) and spinous process osteotomy (SPO). Primary outcome was the mean change in Oswestry disability index (ODI) score at five-years follow-up. Secondary outcomes were the proportion of patients classified as success, mean change in EQ-5D, ZCQ-score, NRS-score for leg and low back pain, a seven-point Global Perceived Effect (GPE) Scale and proportion of subsequential spinal surgery.

Results: The number of patients that completed follow-up data after five years was 358 (82%): In the UL, BL and SPO group the numbers were 122, 119 and 117, respectively. Mean age at baseline was 66.7 (SD 8.2) years, mean BMI was 27.8 (SD 4.1), and 172/358 (48%) were female. In the UL group the mean change was  -18.2 (95% CI  -21.0  -5.4), in the BL group it was  -19.0 (95% CI -21.9-16.1) and in the SPO it was  -18.6 (95% CI  -21.6-15.7) (p = 0.917). No significant differences in the secondary outcomes between the three surgical groups were found, also the subsequent spinal surgery rates were similar.

Conclusion: There were no significant differences in patient reported outcomes and subsequent spinal surgery rates after the three different decompression techniques at five-year follow-up.