Gerich, Torsten

Kelm, Jens

Maas, Stefan

Ricci, Pierre-Louis

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Influence of pubic symphysis stiffnesson pelvis stress distribution during single leg stance1 - INTRODUCTION2 - METHODS 3 - RESULTS4 – DISCUSSION and CONCLUSIONPL Ricci, S Maas, T Gerich, J Kelmpierre-louis.ricci@uni.luLoad distribution in pelvis under physiological loading conditionsInverse dynamics :Finite Element Analysis: load distribution in pelvisMusculoskeletal model from AnyBody experimentallyvalidated [1] applied to right single leg stance:healthy volunteer62 kg, 173 cmForces applied to the pelvisSide Left RightHip joints reaction forces [N] 366 1692Muscles forces [N] 760 1 227Sum of forces [N]1126 29194045SacroIliac joints ( ESIJ = 350 MPa, vSIJ =0,495 ):• Left SI joint,• Right SI joint.Bones (averaged mechanical properties from cancellous and spongeous bones: EBones = 7000 MPa, vBones = 0,3 ):• left / right hip bones,• sacrum.Pubic Symphysis ( single component, νPS = 0,495 [2] ):o EPS = 0,5 MPa (Soft),o EPS = 5 MPa (Normal) [4],o EPS = 50 MPa (Stiff).5 - REFERENCES[1] Manders et Rasmussen, (2007) Validation of hip joint force simulation by gait analysis. Dresden, Germany.[2] Fan et al., (2015) Biomechanical analysis of the fixation system for T-shaped acetabular fracture. Computational and Mathematical Methods in Medicine, Volume 2015.Soft Pubic SymphysisEPS = 0,5 MPaNormal Pubic SymphysisEPS = 5 MPaStiff Pubic SymphysisEPS = 50 MPa23 1719 22312-461143-861465-102-120-100-80-60-40-20020406080Fx Fy FzSection force [N]Section force at PS0,5 5 50EPS =                         MPa-5667445-6464483-6762296-200-1000100200300400500600700800Fx Fy FzSection force[N]Section force at Right SI Joint0,5 5 50EPS =                         MPa-453162-376124-348210-60-40-20020406080100Fx Fy FzSection force[N]Section force at Left SI Joint0,5 5 50EPS =                        MPa8th World Congress of Biomechanics 24th Congress of the European Society of Biomechanics8-12 July 2018Dublin, IrelandBoundaryconditions:• Spherical joint at the lumbosacral joint,• Physiological forces from inverse-dynamics simulation (AnyBody),• Soft springs at lower ischial tuberosities for numerical convergence.Considered muscles: • Adductor,• Biceps Femor,• Erector Spinae,• Gemellus,• Gluteus,• Gracilis,• Iliacus,• Latissimus Doris,• Multifidi,• Obliqus Externus,• Obliqus Internus,• Obturator,• Pectineus,• Piriformis,• Psoas Major,• Quadratus Femoris,• Quadratus Lumborum,• Rectus Abdominis,• Rectus Femoris,• Sartorius,• Semimembranosus,• Semitendinosus,• Tensor Fasciae Latae.σVM (MPa)Von Mises stresses:0.0 0.00.00.0-0.30.00.1-1.3-0.2-1.4-1.2-1.0-0.8-0.6-0.4-0.20.00.2Fx Fy FzSection moment [N.m]Section moment at PS0,5 5 50EPS =                         MPa37.1-5.80.031.2-8.012.028.3-7.710.3-10010203040Fx Fy FzSection moment [N.m]Section moment at Right SI Joint0,5 5 50EPS =                         MPa2.11.58.81.04.511.91.94.713.702468101214Fx Fy FzSection moment [N.m]Section moment at Left SI Joint0,5 5 50EPS =                        MPaPelvis complex circular structure:• 3 bones: • Left/right hipbones,• Sacrum,• 3 joints:• Left/right SacroIliac joints (SI joints),• Pubic Symphysis (PS).Stability is essential to prevent lower back pain and further complications.evaluation of eventual relative motion with single leg stance radiographs.Aim of the study: to assess the influence of Pubic Symphysis (PS) stiffness on the integrity of the bony structures and joints. Numerical single leg stance model with loads from muscles and hipsSoft PS / Normal PS / Stiff PSChanges in stress distribution ? Joints reaction forces, Muscles forces.Normal PS: higher stresses at the superior ramusSoft PS:• decreases stresses at the superior ramus,• increases stresses on the sacrum.Stiff PS:• increses stresses at the superior ramus,• decreases stresses on the sacrum.e.g.: increased laxity, pregnant women, etc.  lower back pain and problems on the back ?e.g.: elderly people, bridging of the PS, etc.  superior rami more prone to fracture ?PS, experiencing more compression forces than shearing forces.essential role on the load distribution,key element of the biomechanics of the pelvis.

Influence of pubic symphysis stiffness on pelvis stress distribution during single leg stance

http://orbilu.uni.lu/bitstream/10993/36793/1/WCB2018_RICCI_PS_stiffness.pdf

Influence of pubic symphysis stiffness on pelvis stress distribution during single leg stance

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