Is There a Need for Functional Radiographs in Diagnosing Lumbar Instability?

Area of Science:

• Radiology
• Spine Imaging
• Biomechanical Analysis

Background:

• Low-grade spondylolisthesis diagnosis often relies on assessing spinal instability.
• Current methods include MRI and standing sagittal plane radiography (SP).
• The utility of functional radiography (FRF) in evaluating instability needs further clarification.

Purpose of the Study:

• To compare the diagnostic value of FRF (flexion and extension) against MRI and SP for low-grade spondylolisthesis.
• To assess the reliability of measuring sagittal translation (ST) and rotation (SR) using different imaging modalities.
• To determine the agreement between FRF, MRI, and SP in diagnosing spinal instability.

Main Methods:

• Retrospective analysis of radiological datasets from 55 patients with 165 lumbar segments.
• Measurement of ST and SR at all lumbar levels using SP, FRF, and MRI.
• Calculation of differences in ST and SR between imaging methods; assessment of lumbar lordosis, sacral slope, pelvic tilt, and pelvic incidence.

Main Results:

• Instability was detected in 12.1% of segments with SP/MRI versus 8.5% using FRF/FRE for ST.
• SR functional radiographs identified instability in 25% (SP/MRI) compared to 14% (FRF/FRE).
• Moderate to excellent agreement (ICC 0.74-0.97) for ST between SP and FRE; moderate agreement for SR (ICC 0.61-0.72). Moderate to good agreement (ICC 0.52-0.80) for ST between MRI and FRF, but poor agreement for SR (ICC 0.16-0.23).

Conclusions:

• Diagnosing instability via ST differences in SP and MRI may be sufficient without additional functional radiographs.
• FRF demonstrated translational instability more clearly than MRI in certain patients.
• FRF can be a valuable tool for diagnosing spinal instability, particularly in ambiguous or borderline cases.