Hidden Spondylolisthesis: Unrecognized Cause of Low Back Pain? Prospective Study about the use of Dynamic Projections in Standing and Recumbent Position for the Individuation of Lumbar Instability

Introduction The execution of dynamic X-rays is commonly used and widely recognized as an effective method to detect the presence of lumbar instability and to obtain qualitative and quantitative data regarding this condition. This examination is commonly executed while the patient is in a standing position. In our opinion, the standing position works as a limit to some micromovements of the lumbar segment affected by the spondylolisthesis, hiding its presence. According to us, the paravertebral muscles act as a stabilizer of the hypermovement (which generates instability) because of its antalgic contraction and augmented muscular tone. The aim of our study is to demonstrate that flexion and extension X-rays performed in recumbent position, with the patient lying along his/her side (in a patient with low back pain or sciatic pain), reduce the augmented muscular tone of the paravertebral muscles and might discover hypermovements hidden by antalgic contractions and not evidenced in dynamic studies executed in standing position. Materials and Methods In the period between January 2011 and January 2013, in the neurosurgery department of the Sapienza University of Rome, 200 consecutive patients with lumbar degenerative disease have been studied (males 117 and females 83). All the patients have been studied with lumbosacral MRI and dynamic X-rays performed in standing and recumbent positions. The aim of our study is to find a correlation between clinical symptom (low back pain or radicular pain) and the presence of a spondylolisthesis not shown by the dynamic X-rays in standing position, but shown by the dynamic X-rays executed in recumbent position, demonstrating how an unknown spondylolisthesis, not discovered by Rx in standing position, can cause low back pain. Results We analyzed 200 patients. A total of 133 were not pathologic in the Rx executed in standing position. Of the 133, 43 patients (32,3%) showed a hypermovement in the dynamic projections executed in recumbent position ( p = 0.0001, McNemar test). The statistical analysis did not show any significant correlation between the hidden spondylolisthesis in standing position and age, sex, or level involved. The evidence of pathological hypermovement at the recumbent dynamic Rx has changed the surgical strategy, reducing the percentage of undertreatment of a degenerative and progressive clinical situation. Conclusion The aim of our study is to determine whether in the patients with lumbalgia with no evidence of pathological movements in the standing dynamic projections, the origin of the pain can be attributed to a faccettal syndrome or is linked to a spondylolisthesis not showed by the standing dynamic Rx. In our opinion, the spondylolisthesis can be identified as the pain generator. Consequence of the pain is an augmented muscular tone of the paravertebral musculature to prevent pain, which is at its major intensity in the standing position, when the intervertebral articulations are mostly solicited. The augmented muscular tone tries to inhibit the pain generator, attempting to limit the slippage of the involved segment. When the patient is examined in dynamic projections when recumbent on his/her side, the tone of the paravertebral musculature is reduced, showing, when present, the “hidden” spondylolisthesis.