Oral Presentation 51st International Society for the Study of the Lumbar Spine Annual Meeting 2025

A new scale to identify symptomatic lumbar foraminal stenosis on magnetic resonance images (115446)

Shuchen Ding 1 , Lunhao Chen 2 , Chudi Fu 1 , Junli Liang 3 , Miao Liu 4 , Yuzhen Xi 4 , Zhiyun Feng 2 , Yisheng Lu 1 , Yue Wang 2
  1. Center of Orthopedics, No. 903 Hospital of PLA Joint Logistic Support Force (Affiliated Xihu Hospital Hangzhou Medical College), Hangzhou
  2. Department of Orthopedic Surgery, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, ZHEJIANG, China
  3. Department of Anesthesiology, No. 903 Hospital of PLA Joint Logistic Support Force (Affiliated Xihu Hospital Hangzhou Medical College), Hangzhou
  4. Department of Radiology, No. 903 Hospital of PLA Joint Logistic Support Force (Affiliated Xihu Hospital Hangzhou Medical College), Hangzhou

Introduction: Lumbar foraminal stenosis (LFS) is an important spinal pathology that may lead to radiating leg pain. Meanwhile, LFS judged on magnetic resonance (MR) images is also a common age-related degenerative phenotype that is often asymptomatic. While it is clinically important to differentiate symptomatic LFS from asymptomatic ones, no image classification system of LFS has been correlated to leg pain symptom. In this study, we modified the commonly used Lee’s classification of LFS with the aim to identify symptomatic LFS on MR images.

Methods: The degree of LFS was evaluated on T2W para-sagittal MR images and a new scale of LFS was proposed based on the traditional Lee’s classification. Grade 0, a foramen with perineural fat fully surrounding the exiting nerve root, or with perineural fat obliteration in two opposing directions; Grade 1A, a foramen having perineural fat obliteration in all four directions and the nerve root is clearly without morphologic change; Grade 1B, there are morphologic changes of the nerve root, which is directly compressed in two opposing directions; Grade 2, the nerve root is compressed in all four directions, or cannot be visualized clearly (Figure 1).

A prospective study of symptomatic LFS patients was conducted. For each included patient, bilateral L3-S1 intervertebral foramina were independently evaluated using the new LFS scale by 4 raters for twice with a span of 6 weeks. Ultrasound guided nerve root block was performed for the L3-S1 intervertebral foramina on the symptomatic side. When the patient’s radiating leg pain was induced in nerve root block, it was defined as symptomatic foramina. Otherwise, it was defined as control asymptomatic foramina. The reliability of the scale, and the relationship between the new classification system with leg pain was examined.

Results: From 2022 to 2024, 112 patients with LSF were studied. The new scale showed excellent inter-rater reliability (κ=0.90-0.91) and intra-rater reliability (κ=0.94-0.96). With nerve root block, 126 foramina were classified as having symptomatic LFS. None of grade 0 foramina were symptomatic, and all grade 2 foramina were symptomatic. Fourteen (23.0%) and 49 (70.0%) foramina with grade 1A and grade 1B LFS were symptomatic, respectively. Two weeks after nerve root block, the degree of pain relief was significantly lesser in Grade 2 group than in Grade 1A and Grade 1B groups (median ΔNRS -2.0 vs -4.0, p<0.001 for both comparisons).

Conclusion: The new LFS scale can help to differentiate symptomatic LFS from asymptomatic ones. While Grade 0 represented asymptomatic foramina, Grade 2 reflected painful LFS and had a poor prognosis following nerve root block.

 

Figure 1. Schematic illustrations of the new scale of LFS and typical MR image examples. White arrows indicate the direction of stenosis or nerve root compression. Stenosis refers to perineural fat obliteration, and nerve root compression refers to morphologic change of nerve root. NR: nerve root; V: vertebral body; D: intervertebral disk; LF: ligamentum flavum; FJ: facet joint.

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