Oral Presentation 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

Dural Sac Cross-sectional area change from preoperatively and up to 2 years after decompressive surgery for central lumbar spinal stenosis. - investigation of operated levels, data from the NORDSTEN study (#MP-7b)

Erland EH Hermansen 1 , Tor Åge TM Myklebust 1 , Ivar Magne IMA Austevoll 2 , Christian CH Hellum 3 , Kjersti KS Storheim 3 4 , Hasan HB Banitalebi 5 , Kari KI Indrekvam 2 , Helena HB Brisby 6
  1. HELSE MØRE OG ROMSDAL HF, ÅLESUND, Norway
  2. Orthopedic Dep, Helse Bergen, Bergen, Norge
  3. Orthopedic Dep, Oslo University Hospital, Oslo, Norge
  4. Communication and Research Unit for Musculoskeletal Health , Oslo University Hopsital, Oslo, Norge
  5. Department of Diagnostic Imaging, Akershus University Hospital, Oslo, Select an option, Norge
  6. Dept of Orthopedics, Sahlgrenska University Hospital, Gothenburg, Sverige

INTRODUCTION: 

Abstract

Background: Decompressive surgery for lumbar spinal stenosis is the most common spine surgery procedure of today. There is scarce knowledge about if there are diagnosable patient specific and/or surgical factors that may influence spinal canal area changes in MRI over time. The aim of the present study was to investigate how canal area size changed from preoperatively values up to two years after decompressive lumbar surgery for surgically treated segment(s). Further, to investigate if an area change postoperatively (between 3 months to 2 years) was associated with any preoperative demographic, clinical or MRI variables or surgical method used.


METHODS: 

The present study is a secondary analysis of data from the NORDSTEN- SST trial where 437 patients were randomized to one of three mini-invasive surgical methods for lumbar spinal stenosis; unilateral laminotomy with crossover, bilateral laminotomy, or spinous process osteotomy. The patients underwent MRI of the lumbar spine before surgery, and three months and two years after surgery. For all operated segments the dural sac cross-sectional area (DSCA) was measured in mm2. Baseline factors collected included age, gender, BMI and smoking habits. Furthermore, perioperative parameters, like surgical method, number of levels operated, specific index level, all levels operated on and baseline Schizas grade were also included in the analysis. 


RESULTS: 

Of the 437 patients that were randomised in the NORDSTEN-SST trial, where of 322 (74%) had both MRI postoperatively and were included in the present analysis. The mean age was 66.3 (SD 8.5), and 170/322 (52.3%) were men. The mean DSCA at index level was 52.3 mm2 (SD 21.2) at baseline, at three months it increased to 117.3 mm2 (SD 43.0) and after two years the area was 116.2 mm2 (SD 52.5). We found the same findings of values of achieved DSCA when analysing for number of levels, surgical method, index level, all operated levels, and Schizas grade at baseline.


DISCUSSION: 

The spinal canal area after lumbar decompressive surgery for lumbar spinal stenosis increased from baseline to three months after surgery and remained thereafter unchanged two years postoperatively. The observed increase in area was not affected by patient characteristics or any matters investigated related to the surgery.