Clinical Implication of Mid-Range Dynamic Instability in Lumbar Degenerative Spondylolisthesis

Abstract

Study Design: Retrospective evaluation.Purpose: To determine the prevalence of mid-range dynamic instability in patients with degenerative spondylolisthesis (DS) and to evaluate the clinical implication of mid-range instability (MI).Overview of Literature: Instability is identified by measuring vertebral body anterior–posterior translation on static end-range flexion and extension lateral radiographs. Mid-range kinematics could evince occult dynamic instability in which motion is not appreciated at the terminal-range of motion.Methods: In this study, 30 patients with DS with checked standing dynamic radiographs of the lumbar spine in Gwangmyeong Sungae Orthopedic Clinic were recruited. Standing lateral radiographs were evaluated in extension, 45° of flexion (mid-range) and 90° of flexion (terminal-range) of the lumbar spine. Instability was defined as sagittal translation greater than 3 mm from the extension position. Patients were divided into three groups: a control group, an MI group, and a terminal-range instability (TI) group. Radiographic outcome (stenosis grade) and clinical outcome were compared between the three groups.Results: The average sagittal translation of the lumbar spine was 5.2 mm in extension, 6.6 mm in mid-range, and 7.2 mm in endrange. MI was observed in eight patients (26.2%) and TI was seen in 12 patients (40%). Of eight patients with MI, three patients did not have instability at terminal-range (occult patients) and five patients had instability at terminal-range (typical patients). Body weight and body mass index (BMI) was significantly higher in the MI group as compared to the control group. BMI was positively correlated with slippage to mid-range. There was no significant difference in stenosis grade, Visual Analog Scale, and Oswestry Disability Index. In the TI group, there was no significant difference in radiographic clinical parameters as compared to the control group.Conclusions: MI was demonstrated in 25% of DS patients. Mid-range motion was increased with BMI. Mid-range lateral radiography can reveal occult instability in patients with DS, particularly in obese patients.

How Do Standing Neutral, Supine Lateral, Standing Flexion, and Standing Extension Radiographs Compare in Detecting the Presence and Magnitude of Stable and Dynamic Spondylolisthesis?

“…Overall, an estimated 11% of new patients had dynamic spondylolisthesis detected on standing-supine radiograph pairs alone, which may underestimate the true percentage of patients with dynamic spondylolisthesis. Other studies have reported that the percentage of patients with dynamic spondylolisthesis assessed with flexion-extension radiographs is between 10% and 25% among patients known to have degenerative spondylolisthesis [13, 19]. The estimated percentage of patients with dynamic spondylolisthesis in our study seems reasonable, given that our study used standing-supine radiographs and included patients without spondylolisthesis.…”

“…However, patients without known spondylolisthesis may still have anterolisthesis, and radiographic views may differ in detecting the presence and magnitude of listhesis in these patients. Similarly, studies that have aimed to determine the prevalence of dynamic spondylolisthesis have examined patients with known spondylolisthesis and have estimated the prevalence to be between 10% [19] and 25% [13]. Thus, these prevalence estimates may not represent patients with back and leg pain, and differences in detecting the presence and magnitude of listhesis have not been examined with the use of standing and supine radiographs among patients without spondylolisthesis.…”

The challenge of diagnosing lumbar segmental instability

“…End range vs mid-range controversy Numerous studies may support the hypothesis that the range of motion between vertebrae measured from conventional exion and extension X-rays is not as valuable as analysis of the pattern of motion between the endranges of the exion-extension cycle. (109,111,132,(151)(152)(153)(154)(155)(156)(157)(158)(159) These studies support that the greatest intervertebral rotation and translation can occur as the patient moves from exion to extension and not at the end-range of intervertebral motion. These studies also document that irregularities and discontinuities in intervertebral motion can occur during the exion-extension cycle that cannot be detected from a two-frame exion-extension study.…”

“…With upright standing exion-extension radiographs, it is known that more patient effort leads to more intervertebral motion -this is a fairly simple and intuitive concept. (68,69,111,112) Unfortunately, achieving maximum patient effort is not a simple task. For starters, it may be argued that symptomatic patients cannot be expected to exert much effort because it is painful or uncomfortable.…”

Lumbar Spinal Stenosis: Review Update 2022

“…Some provocative tests, such as the walking, fall-related, and handgrip strength tests, can also be employed to assess the current and postoperative status of patients with LSS [25][26][27][28][29][30]. The Oswestry Disability Index score and the intensity of the patients' leg discomfort were likewise connected to the neuropathic pain component [31].…”