Baastrup’s disease and sagittal alignment: a scoping review of direct evidence and biomechanical context

Abstract Background Baastrup’s disease, also known as kissing spine syndrome, is a degenerative disorder characterized by approximation and repetitive contact of adjacent spinous processes, most commonly in the lumbar spine. Although it is a recognized cause of extension-related midline low-back pain, its relationship with segmental sagittal alignment, pain-related postural adaptation, and global sagittal imbalance remains poorly defined. Clarifying this relationship may improve the interpretation of imaging findings and support more appropriate treatment selection. This scoping review aimed to map the available clinical, radiological, and surgical evidence concerning the potential association between Baastrup’s disease and sagittal malalignment. Methods A scoping review was conducted using PubMed, Scopus, and Google Scholar, supplemented by manual reference screening. Two complementary search approaches were used: a broad disease-specific search without mandatory sagittal terminology and a focused search combining Baastrup-related terms with sagittal alignment, posture, spinopelvic, and treatment concepts. Evidence was classified as direct Baastrup-specific sagittal evidence, Baastrup-specific supportive evidence, secondary evidence, or indirect biomechanical and surgical evidence. Primary studies were appraised using design-specific Joanna Briggs Institute checklists. Results Twenty-five publications were included: one provided direct Baastrup-specific sagittal evidence, 18 provided Baastrup-specific supportive primary evidence, four were disease-specific secondary publications, and two provided indirect biomechanical or surgical evidence. Direct quantitative evidence was limited to a single, substantially confounded case report. Supportive studies characterized prevalence, CT and MRI findings, interspinous bursitis, epidural extension, associated degeneration, and symptomatic treatment, but generally did not include standardized standing sagittal measurements. The certainty of the direct evidence was considered very low. Conclusion Baastrup’s disease is a recognized cause of extension-related midline low-back pain, but current evidence is insufficient to establish an independent causal relationship with global sagittal imbalance. Local posterior-element impingement, degenerative loss of lumbar lordosis, compensatory pelvic mechanisms, and pain-related postural changes may coexist but should not be considered equivalent processes. Baastrup-targeted treatment may relieve concordant mechanical pain in carefully selected patients, whereas its effect on global sagittal alignment remains preliminary and hypothesis-generating. Prospective studies using standing full-spine radiographs, standardized spinopelvic measurements, validated clinical outcomes, and adequate follow-up are required.