Related Experiment Video
Updated: Jun 1, 2026

C-arm-Free Simultaneous OLIF51 and Percutaneous Pedicle Screw Fixation in a Single Lateral Position
Published on: September 16, 2022
Paradoxical motion in L5-S1 adult spondylolytic spondylolisthesis
Jacob Yoong-Leong Oh1, Shen Liang, Danny Louange
1Department of Orthopaedic Surgery, Khoo Teck Puat Hospital, Singapore, Singapore.
Introduction:
In patients with spondylolisthesis, it is assumed that flexion accentuates anterior displacement, whereas extension causes some reduction. Paradoxical movement-where flexion causes reduction of spondylolisthesis and extension increases the anterior translation, is rarely described. In this study, we investigate the prevalence of paradoxical motion in patients with L5-S1 spondylolytic spondylolisthesis and why this abnormal motion occurs.
Materials And Methods:
Flexion and extension radiographs of 41 patients with grade I and II spondylolytic spondylolisthesis of the L5-S1 segment were analysed. Patients who had previous lumbar spine surgery, recent lumbar spine trauma, those more than 50 years of age and those with poor quality radiographs were excluded.
Results:
There were 24 male and 17 female patients. The average age was 32.7 years. Of the 41 patients, 29 (70.7%) showed no significant instability. Six (15%) patients showed anterolisthesis, where flexion accentuated the forward displacement, while further six (15%) patients showed paradoxical motion. Statistical analyses found that patients with paradoxical motion had a significantly higher slip angle.
Conclusion:
In this study, we have demonstrated that: (1) paradoxical motion in spondylolytic spondylolisthesis is more common than previously thought. (2) Patients without anterolisthesis during flexion in dynamic radiographs may still have (paradoxical) instability. (3) Paradoxical motion may be more common in patients with a low sacral slope and increased lumbosacral lordosis.
Related Concept Videos
Degenerative Disc Disease ll: Pathophysiology
Somatic Spinal Reflexes
One of the most well-known somatic spinal reflexes is the stretch reflex, which is activated by the sudden stretching of a muscle. This reflex involves the activation of specialized sensory receptors called muscle spindles, which are located in the muscle tissue and detect changes in the length and speed of muscle contractions. When a muscle is suddenly...
Degenerative Disc Disease I: Introduction
Secondary Spinal Cord Injury llI: Pathophysiology
Eccentric Axial Loading in a Plane of Symmetry
Herniated Intervertebral Disc l: Introduction