Biomechanics of spinal motion segment instability in the lumbar spine: a systematic review

Objective. To determine the most valid biomechanical indicators of the stability of spinal motion segments in the lumbar spine, their normal values, and reproducibility for use in clinical practice of surgical treatment of degenerative diseases. Material and Methods. To identify the most significant and sensitive criteria for assessing the biomechanics of the spinal motion segments in the lumbar spine, 4784 publications were selected using the PubMed and eLibrary search systems, of which 16 articles were selected after evaluation according to the established inclusion and exclusion criteria and served as the basis for further analysis. Result. All segmental stability indices are divided into 3 groups: clinical, radiological and experimental. The rather subjective nature of clinical criteria is noted, including mainly either pain assessment during palpation or assessment of motor activity. At the same time, pain did not show a reliable connection with the presence of instability and can also be associated with radicular syndrome. Radiological instability criteria (static and functional radiography, CT) are in error against the background of severe pain syndrome due to reflex muscle spasm or due to limitations of the studies themselves. Based on preoperative examination data, it is quite difficult to predict the possible magnitude of instability after decompression during surgery. Biomechanical indices that are established under experimental conditions include the volume of angular motion, elasticity of the spinal motion segment, the size of the neutral zone and intradiscal pressure. Conclusion. An obvious limitation is the current lack of technical capability for intraoperative measurement of experimental load indices in vivo . Development of technologies in this direction with accumulation of data and analysis of specificity and reproducibility of criteria will improve diagnostic protocols, and planning the volume and options of surgical treatment.