A Novel Musculoskeletal Joint Modeling for Orthopaedic Applications

Abstract

The  objective  of  the  work  carried  out  in  this  research  was  to  develop  analytical  and computational  tools  to  model  and  investigate  musculoskeletal  human  joints. It  was recognised  that  the  FEA  was  used  by  many  researchers  in  modelling  human musculoskeletal  motion,  loading  and  stresses.    However  the  continuum  mechanics played  only  a minor  role  in  determining  the  articular  joint motion,  and  its  value was questionable.  This  is  firstly  due  to  the  computational  cost  and  secondly  due  to  its  impracticality for  this application.   On  the other hand,  there  isn’t any suitable software  for  precise  articular  joint motion  analysis  to  deal with  the  local  joint  stresses  or  non  standard  joints.   The main  requirement  in  orthopaedics  field  is  to  develop  a modeller  software  (and  its  associated  theories)  to  model  anatomic  joint  as  it  is,  without  any  simplification  with  respect  to  joint  surface  morphology  and  material  roperties  of  surrounding  tissues.    So  that  the  proposed  modeller  can  be  used  for  evaluating  and  diagnosing different  joint abnormalities but  furthermore  form  the basis  for performing  implant  insertion and analysis of  the artificial  joints.   The work which  is presented  in  this  research  is  a  new  frame  work  and  has  been  developed  for  human  anatomic  joint  analysis  which  describes  the  joint  in  terms  of  its  surface  geometry  and  surrounding  musculoskeletal  tissues.    In  achieving  such  a  framework  several  contributions  were  made  to  the 6DOF  linear and nonlinear  joint modelling,  the mathematical definition of  joint stiffness, tissue path finding and wrapping and the contact with collision analysis. In  6DOF  linear  joint modelling,  the  contribution  is  the  development  of  joint  stiffness  and damping matrices. This modelling approach is suitable for the linear range of tissue stiffness and damping properties.    This  is  the  first  of  its  kind  and  it  gives  a  firm  analytical basis  for  investigating  joints with  surrounding  tissue and  the cartilage.   The  6DOF nonlinear  joint modelling  is a new scheme which  is described for modelling  the  motion  of  multi  bodies  joined  by  non-linear  stiffness  and  contact  elements.  The  proposed method requires no matrix assembly for the stiffness and damping elements or  mass  elements.    The  novelty  in  the  nonlinear  modelling,  relates  to  the  overall  algorithmic  approach  and  handling  local  non-linearity  by  procedural  means.