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Pelvic incidence-lumbar lordosis mismatch results in increased segmental joint loads in the unfused and fused lumbar spine

Senteler, Marco ; Weisse, Bernhard ; Snedeker, Jess ; Rothenfluh, Dominique

In: European Spine Journal, 2014, vol. 23, no. 7, p. 1384-1393

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    Titre
    • Pelvic incidence-lumbar lordosis mismatch results in increased segmental joint loads in the unfused and fused lumbar spine
    Auteur
    • Senteler, Marco. Department of Orthopedics Balgrist, University of Zurich, Zurich, Switzerland
    • Weisse, Bernhard. Laboratory for Mechanical Systems Engineering, EMPA, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
    • Snedeker, Jess. Department of Orthopedics Balgrist, University of Zurich, Zurich, Switzerland
    • Rothenfluh, Dominique. Department of Orthopedics Balgrist, University of Zurich, Zurich, Switzerland
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • European Spine Journal, 2014, vol. 23, no. 7, p. 1384-1393. Springer Berlin Heidelberg
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:326053
    Summary
    Purpose: Symptomatic adjacent segment disease (ASD) has been reported to occur in up to 27% of lumbar fusion patients. A previous study identified patients at risk according to the difference of pelvic incidence and lordosis. Patients with a difference between pelvic incidence and lumbar lordosis >15° have been found to have a 20 times higher risk for ASD. Therefore, it was the aim of the present study to investigate forces acting on the adjacent segment in relation to pelvic incidence-lumbar lordosis (PILL) mismatch as a measure of spino-pelvic alignment using rigid body modeling to decipher the underlying forces as potential contributors to degeneration of the adjacent segment. Methods: Sagittal configurations of 81 subjects were reconstructed in a musculoskeletal simulation environment. Lumbar spine height was normalized, and body and segmental mass properties were kept constant throughout the population to isolate the effect of sagittal alignment. A uniform forward/backward flexion movement (0°-30°-0°) was simulated for all subjects. Intervertebral joint loads at lumbar level L3-L4 and L4-L5 were determined before and after simulated fusion. Results: In the unfused state, an approximately linear relationship between sagittal alignment and intervertebral loads could be established (shear: 0° flexion r=0.36, p<0.001, 30° flexion r=0.48, p<0.001; compression: 0° flexion r=0.29, p<0.01, 30° flexion r=0.40, p<0.001). Additionally, shear changes during the transition from upright to 30° flexed posture were on average 32% higher at level L3-L4 and 14% higher at level L4-L5 in alignments that were clinically observed to be prone to ASD. Simulated fusion affected shear forces at the level L3-L4 by 15% (L4-L5 fusion) and 23% (L4-S1 fusion) more for alignments at risk for ASD. Conclusion: Higher adjacent segment shear forces in alignments at risk for ASD already prior to fusion provide a mechanistic explanation for the clinically observed correlation between PILL mismatch and rate of adjacent segment degeneration.