Imaging predictors of progression of lumbar spondylolysis to spondylolisthesis: a systematic review

BACKGROUND CONTEXT: Isthmic spondylolisthesis (IS) is defined as the anterior translation of one lumbar vertebra relative to the next caudal segment as a result of a unilateral or bilateral fracture of the pars interarticularis. These fractures are interchangeably known as "pars defects" or "spondylolysis." Many risk factors have been proposed to explain the progression of a spondylolytic defect to IS, however, none are validated. PURPOSE: This systematic review provides an overview of various radiological and imaging parameters that can help predict the risk of progression of a spondylolytic defect into IS. STUDY DESIGN: Systematic review. METHODS: Medline, Embase and Cochrane online database were searched. The various correlations between imaging features with observed spondylolisthesis prevalence or severity or spondylolysis rates of spondylolisthesis were evaluated to provide a list of imaging risk factors to predict IS. Significance of the correlations in the original article was recorded to enable comparison of the collected evidence of separate image features. RESULTS: All searches combined generated a total of 431 results of which 26 articles were included into this study. Of the 22 potential risk factors identified, 5 were found to be statistically insignificant, 8 were found to be significant and 9 had mixed results. The following features were found to be significant risk factors in at least on study: disc degeneration, transverse process width, pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, lumbar index, thoracic kyphosis, facet joint angle above the level of defect, facet joint degeneration, facet tropism, multifidus size, lateral erector spinae size, mesenteric fat thickness, subcutaneous fat thickness and soft tissue calcification. CONCLUSION: Our research suggests that only disc degeneration had moderately strong evidence with consistent significant associations with development of IS in patients with spondylolysis. Transverse process width, pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, lumbar index, thoracic kyphosis, facet joint angle above the level of defect, facet joint degeneration, facet tropism, multifidus size, lateral erector spinae size, mesenteric fat thickness, subcutaneous fat thickness and soft tissue calcification had some evidence. All other radiological factors had weak evidence. The results of this study can be used to improve early clinical decision making for patients with spondylolysis. (c) 2024 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)