DEVELOPMENT OF A PATIENT-SPECIFIC FINITE ELEMENT MODEL OF A PATHOLOGICAL TRAPEZIOMETACARPAL JOINT

Ana Matos (1), António Completo (1), Abel Nascimento (2), Carlos Relvas (1), Antonio Ramos (1), Jose Simoes (1)

1. Department of Mechanical Engineering, University of Aveiro, Portugal

Introduction

One of the reasons that allows man to distinguish

himself from the other animals lies in the fact that

he possesses a hand gifted with a thumb that,

throughout evolution, has grown different from the

other fingers. Surprisingly, this particularization

lead to the development of a pathology

denominated Rhizarthrosis, which generates

instability and subsequent immobilization of the

first finger. This fact is, therefore, sufficient to

develop a study area exclusively dedicated to the

thumb and, particularly, to the

trapeziometacarpiana articulation (TMC). TMC is

an unstable articulation, from the selar type, which

involves the trapezium and the first metacarpus,

thus needing a steady ligament support and

justifying the 16 ligaments that it consists of. Its

complexity leads to the development of several

pathologies, amongst which Rhizarthrosis will be

the study core of this project [Bettinger].

Rhizarthrosis is a severe disease that aggravates

throughout the ageing process and that occurs

primarily in female patients, with ages between 45

and 65 years. It is also largely diagnosed in men

whose daily work involves the rotation movement

of the wrist. This work leads with the need to

provide a better answer to the solution of this

problem. The main goal of this study was develop

finite element models to study comparatively the

biomechanical behaviour of a health and a

pathological trapeziometacarpal joint in order to

understand the main structural differences.

Methods

With the purpose of achieving the proposed

objectives, two different CT scans of the joint were

used – one relative to a pathological joint, and the

other of an health joint. In a first step were

developed both 3D image models of the

trapeziometacarpal joint in the health and

pathological cases through a processing and

segmentation software - ScanIP. In a second step

the 3D image data were converted in volumetric

models (Figure-1) that were used to generate

volume mesh models. The mesh models generated

had automatically assigned the material properties

from grey level data of the CT scans. These ready

meshes were directly imported into a commercial

non linear FE package MSC.MARC. After that

were performed the non-linear structural analysis at

the joint, where were determined the stress-strain

fields at the joint region and the contact forces for

different load-cases. The result were compared

between the health and pathological models.

Figure 1: 3D model of the case at study.

Results

The results at the joint demonstrated different

stress-strain behaviour between the health and the

pathological models., as well as different contact

forces at the joint surfaces for the same load-cases.

The load-cases applied changes considerably the

stress-strain distributions at the joint.

Discussion

The obtained results will be utilized to guide the

development of a new concept of resurfacing

implant to this joint.

Acknowledgement

Program COMPETE through the projects

PTDC/EME-PME/103578/2008,PTDC/EME- PME

/111305/2009 and PTDC/EME TME/113039/2009.

References

Bettinger PC, Linscheid RL, Berger RA, Cooney

WP, 3rd, An KN. An anatomic study of the

stabilizing ligaments of the trapezium and

trapeziometacarpal joint. J Hand Surg [Am] 786-

798 (1999)

Presentation 1006 − Topic 27. Joint arthroplasty S355

ESB2012: 18th Congress of the European Society of Biomechanics Journal of Biomechanics 45(S1)