The 3-kilogram weight-lifting flexion radiograph: a new diagnostic method for segmental sagittal lumbar instability: a cross-sectional study.

Abstract

Study design: A cross-sectional study.

Purpose: To evaluate the diagnostic performance of a novel 3-kg weight-lifting flexion radiograph for detecting lumbar instability.

Overview of literature: Conventional flexion-extension radiographs have limited sensitivity for detecting lumbar instability, while magnetic resonance imaging (MRI) is a reliable standard. This study compares the performance of a novel weight-lifting radiograph to conventional flexion radiographs, using MRI as the reference standard.

Methods: Forty-six patients with a diagnosis of lumbar instability were enrolled. Participants underwent lateral flexion, lateral extension, and 3-kg weight-lifting flexion lumbosacral spine radiographs. MRI was also performed on all participants. Diagnostic parameters, including sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and likelihood ratios, were calculated for each lumbar level. Reliability was assessed using intraclass correlation coefficients (ICCs).

Results: The 3-kg weight-lifting flexion radiograph showed higher sensitivity for detecting spinal instability at the L3/4 and L4/5 levels (88% vs. 36% and 83.3% vs. 44.44%, respectively) but lower specificity (61.9% vs. 76.19% and 70% vs. 80%, respectively) compared to the conventional flexion radiograph. McNemar tests revealed no significant differences between the 3-kg weight-lifting flexion radiograph and MRI at these levels (p >0.05). Reliability assessments demonstrated excellent intra- and interobserver agreement (ICC ≥0.99). Furthermore, this technique was safe, with no adverse effects reported.

Conclusions: The 3-kg weight-lifting flexion radiograph enhances diagnostic sensitivity and accuracy for lumbar instability, particularly at the L3/4 and L4/5 levels, offering a reliable screening alternative.