Spine Journal - 2026-06-23 - Journal Article
Diagnostic Value of Upright-Supine Imaging and Its Association with Postoperative Outcomes in Degenerative Lumbar Spondylolisthesis - A Two-Year PROM Based Comparison with Flexion Extension Radiographs.
Folkerts T, Wimmer J, Schönnagel L, Mielke AM, Verna B, Torres PR, Köhli P, Zhu J, Shue J, Duculan R, Sama AA, Girardi FP, Cammisa FP, Mancuso CA, Burkhard MD, Hughes AP
Topics
Key Takeaway
Upright-supine imaging (USI) detected instability in significantly more DLS segments than flexion-extension radiographs, and a ΔRT_USI threshold of 7.9% predicted worse outcomes after decompression-only while thresholds of 5.3–5.7% predicted better outcomes after fusion.
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Key Limitation
Non-randomized surgical allocation means patients selected for fusion likely had higher baseline instability, making the inverse outcome associations between surgical groups susceptible to unmeasured confounding despite multivariable adjustment.
Original Abstract
BACKGROUND CONTEXT
The optimal surgical treatment of degenerative lumbar spondylolisthesis (DLS) is a subject of ongoing debate, particularly regarding the choice between decompression-only and fusion surgery. Flexion-extension radiographs (FER) are commonly used to assess segmental instability and guide this decision, but in symptomatic patients their reliance on active patient motion can lead to underestimation of instability that may be associated with postoperative outcomes. Upright-supine imaging (USI), which compares upright radiographs with supine MRI, assesses translational slip dynamics under physiological loading conditions and may offer a more sensitive alternative. However, the clinical and outcome relevance of USI-based instability assessment across different surgical strategies is unclear.
PURPOSE
To compare the association of USI- and FER-derived instability measures with postoperative improvement in disability and low back pain (LBP) and to evaluate whether the clinical impact of instability differs between decompression-only and fusion surgery in patients with DLS.
DESIGN
Retrospective cohort study.
PATIENT SAMPLE
Two hundred fifty-four patients with DLS treated by decompression-only surgery or fusion surgery.
OUTCOME MEASURES
Functional disability and LBP were assessed using the Oswestry Disability Index (ODI) and numeric rating scale (NRS) preoperatively and at two-year follow-up.
METHODS
Slip dynamics were quantified on FER and USI as the between-position difference in relative translation (ΔRT). Associations between ΔRT on FER (ΔRT_FER) and USI (ΔRT_USI) and postoperative outcomes were evaluated using multivariable regression models. Interaction analyses were performed to assess procedure-dependent effects. Receiver operating characteristic (ROC) analyses explored procedure-specific ΔRT_USI thresholds for clinically meaningful improvement.
RESULTS
USI identified a significantly higher proportion of unstable segments than FER in both decompression-only and fusion cohorts (both p < 0.001). ΔRT_USI was significantly associated with both absolute and relative postoperative improvement in ODI and LBP (both p<0.001), whereas ΔRT_FER showed no significant association with outcomes in this cohort (all p > 0.2). The effect of USI-derived instability demonstrated inverse associations by surgical strategy, with greater ΔRT_USI associated with less improvement after decompression-only surgery and greater improvement after fusion (p<0.001 for both ODI and LBP). ROC analyses identified exploratory procedure-specific ΔRT_USI thresholds, with a cutoff of 7.9% for decompression-only surgery and cutoffs of 5.7% (ODI) and 5.3% (LBP) for fusion.
CONCLUSIONS
In this cohort, USI detected segmental instability that was not captured by conventional FER and was associated with postoperative outcomes. The impact of instability on clinical improvement differed according to surgical strategy, suggesting that USI-derived slip dynamics may help risk-stratify patients in preoperative assessment. Procedure-specific ΔRT_USI thresholds identified in this study may support a more stratified approach to surgical decision-making; however, these findings should be considered hypothesis-generating and warrant prospective validation in independent cohorts.