Utility of the decubitus or the supine rather than the extension lateral radiograph in evaluating lumbar segmental instability

Dynamic Instability Is Underestimated on Standing Flexion-Extension Films When Compared With Prone CT Imaging

STUDY DESIGN/SETTING

Single center retrospective cohort study.

OBJECTIVE

We performed a retrospective study evaluating the incidence and degree of L4-5 anterior spondylolisthesis in patients with standard supine MRI, standing flexion-extension radiographs, and prone CT. We hypothesize that prone CT imaging will provide greater sensitivity for instability compared with conventional flexion extension or supine positions.

SUMMARY OF BACKGROUND DATA

Dynamic lumbar instability evaluated by flexion-extension radiographs may underestimate the degree of lumbar spondylolisthesis. Despite efforts to characterize dynamic instability, significant variability remains in current guidelines regarding the most appropriate imaging modalities to adequately evaluate instability.

METHODS

We assessed single-level (L4-5) anterolisthesis between 2014 and 2022 with standing lateral conventional radiographs (CR), flexion-extension images, prone CT images (CT), or supine MRI images (MRI).

RESULTS

We identified 102 patients with L4-5 anterolisthesis. The average translation (±SD) measured were 4.9±2.2 mm (CR), 2.5±2.6 mm (CT), and 3.7±2.6 mm (MRI) (P<0.001). The mean difference in anterolisthesis among imaging modalities was 2.7±1.8 mm between CR and CT (P<0.001), 1.8±1.4 mm between CR and MRI (P<0.001), and 1.6±1.4 mm between CT and MRI (P=0.252). Ninety-two of 102 patients (90.2%) showed greater anterolisthesis on CR compared with CT, 72 of 102 (70.6%) comparing CR to MRI, and 27 of 102 (26.5%) comparing CT to MRI. We found that 17.6% of patients exhibited ≥3 mm anterior translation comparing CR with MRI, whereas 38.2% of patients were identified comparing CR with CT imaging (χ2 test P=0.0009, post hoc Fisher exact test P=0.0006 between CR and CT). Only 5.9% of patients had comparable degrees of instability between flexion-standing.

CONCLUSIONS

Prone CT imaging revealed the greatest degree of single L4-5 segmental instability compared with flexion-extension radiographs.

How Does the Slump Sitting Radiograph Increase Proportion of Segmental Instability and Kyphotic Alignment of Lumbar Degenerative Spondylolisthesis?

OBJECTIVE

Clinical and radiographic degenerative spondylolisthesis (CARDS) classification was proposed to differentiate homogenous lumbar degenerative spondylolisthesis (LDS) subgroups. The sitting radiograph exhibited lumbar malalignment with maximum lumbar kyphosis, intervertebral kyphosis, and spondylolisthesis.This study aimed to assess the sitting radiograph for distribution of clinical and radiographic degenerative spondylolisthesis classification, and to elucidate its significance for exhibiting kyphotic alignment (CARDS type D) and segmental instability.

METHODS

A cohort of 101 patients with symptomatic lumbar degenerative spondylolisthesis (LDS) between September 2018 and December 2020 were recruited. The distribution and relibility of CARDS classification with or without sitting radiograph was assessed. The translational and angular range of motion and segmental instability was also evaluated. Univariate analysis of variance was used for multiple groups, and the least significant difference for two groups. Kappa consistency test of intrarater and interrater was evaluated for CARDS classification with or without sitting radiograph. Chi-square test was used to compare paried categorical data.

RESULTS

Utility of sitting radiographs for CARDS classification revealed higher percentage of type D than that without the sitting radiograph (p < 0.001). The sitting radiograph revealed a larger slip distance than the flexion radiograph (p = 0.003), as well as a lower slip angle than flexion radiograph (p < 0.001). The sitting-supine modality demonstrated the largest translational range of motion compared to the sitting-extension (p < 0.001) and flexion-extension modalities (p < 0.001). The sitting-supine modality showed larger angular range of motion than the flexion-extension modality (p < 0.001). The percentage of flexion, extension, upright, supine, and sitting radiograph to identify translational instability was higher than that without sitting radiograph (p < 0.001), as well as taking angular motion ≥10° as an additional criterion for segmental instability (p < 0.001).

CONCLUSION

The CARDS classification was reliable for LDS. The sitting radiograph showed maximal slip distance and kyphotic slip angle. Application of the sitting radiograph was necessary for evaluating segmental instability and kyphotic alignment of LDS.

The Relationship Between Endplate Defect Scores and Lumbar Sagittal Translation Stability in Lumbar Spondylolisthesis Patients

BACKGROUND

Lumbar instability and endplate defects are commonly seen in patients with spondylolisthesis. However, little is known about associations between segmental stability and endplate defects. The present study explored associations between stability-related radiographic parameters and endplate defect scores and assessed whether endplate defect scores can predict lumbar stability in lumbar spondylolisthesis.

METHODS

Neutral, flexion, and extension radiographs of 159 patients with monosegmental lumbar spondylolisthesis were analyzed. Radiographic parameters included average intervertebral disc height (IDH), slip distance, sagittal translation (ST) and sagittal angulation (SA). Correlation analysis and linear regression analysis were used to explore associations between endplate defect scores and radiographic parameters. Logistic regression analysis was used to assess associations between endplate defect scores and ST stability. Receiver-operating characteristic curve (ROC) analysis was used to evaluate the value of the endplate defect score in predicting ST stability.

RESULTS

A total of 11.9% of patients had ST ≥ 4 mm, and 30% of patients had SA ≥ 10°. Endplate defect scores were negatively correlated with ST and IDH and positively correlated with slip distance in isthmic spondylolisthesis but not in degenerative spondylolisthesis. In multiple regression analysis, endplate defect scores were significantly associated with ST, slip distance, IDH, and disc degeneration. ST instability was associated with endplate defect scores in isthmic spondylolisthesis (OR=0.460, P = 0.010). The AUCs for using the endplate defect score to evaluate ST stability in overall patients and isthmic spondylolisthesis patients were 0.672 and 0.774, respectively. The optimal threshold of the endplate defect score constructed by the Youden index was 7.5 for predicting ST stability.

CONCLUSIONS

Endplate defect scores increase with a reduction in IDH, progression of slippage and a decrease in ST in isthmic spondylolisthesis but not in degenerative spondylolisthesis. ST instability was associated with endplate defect scores in isthmic spondylolisthesis, and endplate defect scores could be used to reflect lumbar stability at the slippage segment.

Utility of Flexion-Extension Radiographs with Brackets and Magnetic Resonance Facet Fluid for the Assessment of Lumbar Instability in Degenerative Lumbar Spondylolisthesis

OBJECTIVE

To propose a new standardized technique for evaluating lumbar stability in degenerative lumbar spondylolisthesis using lumbar lateral flexion-extension radiographs with brackets and magnetic resonance facet fluid.

METHODS

A retrospective analysis of 57 patients diagnosed with lumbar (L4-5) spondylolisthesis was performed. We analyzed lateral flexion-extension radiographs obtained with a bracket (LFEB) and without a bracket (LFE). Sagittal translation, segmental angulation, posterior opening, lumbar instability, and changes in lumbar lordosis were compared using functional radiographs. The mean width and maximum width of the facet fluid, mean facet joint length, and facet fluid index (FFI) of the 2 groups were compared using sagittal translation.

RESULTS

The average value of sagittal translation was 1.68 ± 0.96 mm in LFE and 3.07 ± 1.29 mm in LFEB, and the difference was significant (P < 0.05). Segmental angulation, posterior opening, and changes in lumbar lordosis were significantly greater in LFEB than in LFE. The instability detection rate was 14.0% in LFE and 35.1% in LFEB. The FFI, maximum width, and mean width were significantly increased in the unstable lumbar spondylolisthesis group compared with the stable group in LFEB. The FFI and maximum width of the facet fluid were significantly increased in the unstable lumbar spondylolisthesis group compared with the stable group in LFE.

CONCLUSIONS

Lumbar lateral flexion-extension radiographs with brackets can standardize the operation process and provide sufficient hyperflexion and hyperextension images. The width of the facet fluid and FFI are significant factors in the evaluation of lumbar stability in patients with lumbar spondylolisthesis.