The analysis of segmental mobility with different lumbar radiographs in symptomatic patients with a spondylolisthesis

Purpose Lumbar flexion–extension radiographs in standing position (SFE) are the most commonly used imaging method to evaluate segmental mobility. Many surgeons use SFE to disclose abnormal vertebral motion and base their decision for surgical fusion on its results. We tested the hypothesis that imaging in standing and recumbent position (SRP) reveals a higher sagittal translation (ST) and sagittal rotation (SR) in symptomatic patients than with SFE. Materials and methods We analysed images of 100 symptomatic patients with a low-grade spondylolisthesis that underwent surgical fusion. To determine the ST and SR in SRP, we compared the images taken in the recumbent position in the CT with images taken in the standing position during the routine plain radiography. Results The measurement of ST revealed an absolute value of 2.3 ± 1.5 mm in SFE and 4.0 ± 2.0 mm in SRP and differed significantly ( p = 0.001). The analysis of the relative value showed an ST of 5.9 ± 3.9% in SFE and 7.8 ± 5.4% in SRP ( p = 0.008). The assessment of ST in flexion and in a recumbent position (FRP) revealed the highest ST (4.6 ± 2.5 mm or 9.2 ± 5.7%). Comparison of SR showed the highest rotation in SFE (6.1° ± 3.8°), however, compared to SRP (5.4° ± 3.3°), it missed the level of significance ( p = 0.051). Conclusions For evaluation of ST in symptomatic patients with spondylolisthesis SRP appears to be more suitable than SFE, while a pathological SR is better revealed in SFE. The analysis of SRP might offer a complementary method to detect or exclude pathological mobility in more cases.