Convened under the auspicious of esteemed endorsers - ISTA

study provides in vivo measurements and non-invasive estimates of joint contact forces duringhigh flexion activities that can be used for joint simulator protocols and finite elementmodeling.FiguresFigure 1 Figure 2Friday, October 8, 2010, 13:30-14:10Session B12: Shoulder ArthroplastySurface-Contour Based Algorithm for Quantifying Glenohumeral LigamentLength Changes During Function*Hippolite Amadi - Imperial College London - London, United Kingdom*Email: hippolite.amadi00@imperial.ac.ukIntroduction: Advanced medical imaging techniques have allowed the understanding of thepatterns of relative bone motions at human joints 1 . However, poor imaging contrasts of softtissues have not allowed the full understanding of various glenohumeral ligaments (GHL)functions during glenohumeral joint (GHJ) manoeuvres. This is presently a significant limitationto research as these structures are said to be responsible for the passive stability of the GHJ 2 .Furthermore, the repairs of GHJ instability often take recourse to these structures 3 . Earlierstudies have presented a model that numerically reconstructs or simulates GHJ motions 4 andhow the locus of bony attachment points of the GHLs on a dynamic GHJ could be numericallytagged and trailed 5 . The aim of this study was to advance these previous findings by developingan algorithm that allows the quantification of GHL lengths at any instantaneous position of theGHJ.Materials and Method: CT scan of a set of humerus and scapula was reconstructed into twoindividual surface meshes of interconnected nodes, each node having a unique vectorialidentification in space. The two attachment nodes (a and b) of a GHL were identified on thebones 5 . Least squares geometric sphere was fitted upon the humeral head (HH) and its centre(c) and radius (r) quantified 6 . Vectors a, b and c were applied to represent the ‘dominantligament plane’ concomitant with the 2D 'dominant plane' of Runciman (1993) 7 . This planedefined the path through which the ligament wrapped on the HH. The point of initial or end ofcontact of GHL on the HH was defined as the point on HH where a line from c intercepts theligament at 90°. Total GHL length was calculated as the sum of its three segments, namely: (1)Proximal segment – a straight line from its glenoid attachment node to the point of initialcontact (2) Wrap segment – an arc of (r) radius of curvature from initial to end contact points(3) Distal segment – a straight line from end contact point to the humeral node of attachment.The wrap segment was further refined by adjusting ligament contacts along this path to theactual surface contour of the HH by integrating all the surface nodes along the path. Thefile:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]