Do We Have Adequate Flexion-extension Radiographs for Evaluating Instability in Patients With Lumbar Spondylolisthesis?

Abstract

Study Design. A retrospective cohort study of consecutive patients. Objective. To investigate whether adequate flexion-extension was acquired in standard functional radiographs in lumbar spondylolisthesis. Summary of Background Data. In lumbar spondylolisthesis, flexion-extension radiographs taken in the standing position are most commonly used to evaluate spinal instability. However, these functional radiographs occasionally depend on the patient's effort and cooperation, they can provide different results. Methods. This study included 92 consecutive patients diagnosed with L4-5 degenerative lumbar spondylolisthesis. We analyzed the flexion-extension radiographs taken with the patient being led by the hand (LH) and those taken without LH (NLH). Sagittal translation (ST), segmental angulation (SA), posterior opening (PO), and lumbar lordosis (LL) were measured on functional radiographs taken in both tests. Then, ST, SA, PO, detection rate of instability, and LL observed in LH were compared with those observed in NLH. Furthermore, the correlation of the difference was evaluated between ST, lumbar angulation, and LL. Results. A relative value of ST was 9.5% ± 4.3% in LH and 5.6% ± 3.3% in NLH, which differed significantly (P < 0.001). SA and PO were also significantly greater in LH than in NLH. The detection rate of instability was 71.7% in LH and 30.4% in NLH (P < 0.001). LL measurement on flexion showed 17.6° ± 13.5° in LH and 28.2° ± 12.2° in NLH, which differed significantly (P < 0.001). However, no significant difference was found in LL on extension between LH and NLH. There was a moderate correlation between the difference of ST, SA, PO, and LL on flexion. Conclusion. Flexion with physical assistance was useful for the detection of abnormal lumbar mobility. Taking radiation exposure into consideration, physical assistance such as using a table in front of a patient could lead the similar evaluation of the segmental instability. Level of Evidence: 2

Intermodal Detection of Lumbar Instability in Degenerative Spondylolisthesis is Superior to Functional Radiographs

“…Mean ST was significantly smaller in CT and MRI compared to each functional radiograph, while there was no difference between indicating a tendency for inadequate flexion due to pain or a sense of insecurity, which could lead to underestimation of lumbar instability ( 25 ). A similar phenomenon has been described by Morita et al, where greater flexion was acquired in functional radiographs if patients were led by hand compared to images where they were not ( 26 ). Leading patients through the motions during radiograph acquisition might help to overcome back pain and mental uneasiness about falling to a certain degree, albeit not being able to fully outweighing muscle tension counteracting segmental movement ( 25 ).…”

“…Furthermore, we were able to demonstrate that the comparison of plain radiographs to either CT scans or MRI images is more sensitive for the detection of increased sagittal translation than functional X-rays alone. As there is a multitude of different functional radiographs that lack standardized routines and depend on compliance and effort of patients and examiners alike, different results due to impaired specificity have to be expected ( 18 , 26 , 30 ). Simplifying the diagnostic process reduces interpatient and interexaminer differences and might help avoid misdiagnosis.…”

Radiological Definitions of Sagittal Plane Segmental Instability in the Degenerative Lumbar Spine – A Systematic Review

“…As mentioned, 8% of the studies in the present review included a kyphotic angle or posterior opening in flexion in their definition of instability. 22 , 28 , 34 - 41 …”

“…16,26,27 Studies have shown that other radiographic protocols might be more sensitive or accurate than standing flexion and extension radiographs. 25,26,[28][29][30] Recently, Liu et al 25 compared flexion-extension radiographs to an upright lateral radiograph and supine MRI (upright-supine method) and showed that the slip percentage difference was significantly higher in the upright-supine method than that observed by the flexionextension method. Other studies support these findings regarding dynamic changes in alignment from upright to supine images.…”

“…As mentioned, 8% of the studies in the present review included a kyphotic angle or posterior opening in flexion in their definition of instability. 22,28,[34][35][36][37][38][39][40][41] Posner et al 17 also investigated slip percentage difference and reported a threshold of >8% in their checklist. This was later confirmed by Boden and Wiesel.…”