Reconsidering flexion-extension imaging: the emerging role of supine MRI and upright radiographs in isthmic lumbar spondylolisthesis

Why This Matters

Flexion-extension (FE) radiographs have long been the standard for assessing spinal instability in isthmic lumbar spondylolisthesis (ILS), often guiding surgical decisions. However, FE imaging has limitations, including patient discomfort, variability, and radiation exposure. This study evaluates whether combining routinely obtained upright radiographs with supine MRI can provide a more clinically meaningful and lower-radiation alternative.

What the Research Found

This study compared traditional flexion-extension radiographs with a combined upright–supine (US) imaging approach in patients with L5/S1 isthmic spondylolisthesis.

Segmental motion (instability) was assessed by measuring dynamic sagittal translation across imaging methods.

Key Findings:

    • Upright–supine (US) imaging detected significantly greater segmental motion than FE radiographs
    • US imaging identified more cases of radiographic instability
    • Only US-measured motion correlated with patient pain intensity
    • Greater instability was associated with less disc degeneration, suggesting earlier-stage pathology
    • US imaging may provide greater clinical relevance compared to traditional FE imaging

Clinical Takeaways

    • Recognize that traditional flexion-extension radiographs may underestimate spinal instability
    • Be aware that combining upright radiographs with supine MRI may improve detection of clinically relevant instability
    • Consider that imaging findings that correlate with pain may be more meaningful for clinical decision-making
    • Understand that instability may be more pronounced in earlier stages of degeneration
    • Consider lower-radiation alternatives when repeated imaging is needed

Where Collaborative Spine Care May Support This

Conservative spine care providers may play a role in identifying patients with potential instability through clinical evaluation and symptom patterns. Understanding how instability relates to pain and function can help guide appropriate referral, imaging decisions, and non-surgical management strategies.

Reference

Folkerts T, Schönnagel L, Hoehl B, et al. Reconsidering flexion-extension imaging: the emerging role of supine MRI and upright radiographs in isthmic lumbar spondylolisthesis. Eur Spine J. 2025.
DOI: http://dx.doi.org/10.1007/s00586-025-09692-1
PubMed: https://pubmed.ncbi.nlm.nih.gov/41428066/

Folkerts T, Schönnagel L, Hoehl B, Bürck L, Preininger I, Muellner M, Labbus K, Khakzad T, Pumberger M, Schömig F. Reconsidering flexion-extension imaging: the emerging role of supine MRI and upright radiographs in isthmic lumbar spondylolisthesis. European Spine Journal: Official Publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society, 2025 Dec 22.  doi: 10.1007/s00586-025-09692-1. Online ahead of print.

URLS: http://dx.doi.org/10.1007/s00586-025-09692-1;https://link.springer.com/10.1007/s00586-025-09692-1;https://pubmed.ncbi.nlm.nih.gov/41428066/;https://www.ncbi.nlm.nih.gov/pubmed/41428066

ABSTRACT:

Purpose Segmental instability guides surgical decision-making in isthmic lumbar spondylolisthesis (ILS). Despite concerns regarding radiation exposure, reproducibility and applicability in patients with pain or limited mobility, flexion–extension (FE) radiographs remain the standard for instability assessment. Combining upright radiographs with supine magnetic resonance imaging (MRI), both routinely obtained in clinical practice, may offer a comparable, lower-radiation alternative. This study aimed to compare segmental motion at L5/S1 between FE and upright–supine (US) imaging and to evaluate their ability to detect radiographic instability.

Methods In this retrospective cross-sectional study, consecutive patients surgically treated for isolated L5/S1 ILS were screened for eligibility. Segmental motion was assessed using FE radiographs and US imaging, including measurements of dynamic sagittal translation and the proportion of patients identified with radiographic signs of instability. Preoperative pain intensity was assessed using the Numeric Rating Scale (NRS).

Results Of 126 screened patients, 78 met inclusion criteria (59% female; median age 48.5 years; median BMI 26.4 kg/m²). Dynamic sagittal translation was significantly greater on US than on FE (p < 0.001). US imaging identified more cases of radiographic instability (p < 0.001). Only US-measured translation was associated with preoperative low back pain intensity (p = 0.025) and was inversely associated with intervertebral disc degeneration (p = 0.014).

Conclusions. US imaging detected a higher proportion of radiographically unstable ILS cases than FE radiographs. Furthermore, only US-derived translation was associated with pain intensity, suggesting greater clinical relevance. Combining upright radiographs with supine MRI may offer a practical, low-radiation alternative for preoperative instability assessment