Comparison of Two Uncemented Trapezio-Metacarpal Cups: A Finite Element Study

Abstract

Trapezium components from two uncemented total joint replacements were compared in a three-dimensional finite element model. A 100 N axial and angular load was applied in a normal and an osteoporotic bone model. The axial deformation and maximum periprosthetic stress are greater for the Elektra than the Motec CMC cup. The Motec CMC design is less sensitive to changing bone quality. The Elektra cup transmits more stress to the cortical bone rim in all load conditions, but under angular loading the proportionate increase in stress is lower. The Motec CMC design distributes the stress and contact pressure more evenly, whereas the Elektra transfers most of the load to the cortical bone rim and the screw hole base. The design features that are believed to be of greatest significance for the differences are the raised centre of rotation of the Motec CMC cup and the collar acting as a lever arm.

Superior bone fixation of conical compared with hemispherical trapezial cup design: an experimental radiostereometry study

“…Finite element analysis has shown that conical cups with a center of rotation at the bone surface deliver less stress to the cortical bone rim during angular loading of 30° compared with conical cups with a center of rotation that is above the bone surface [30]. The extrinsic center of rotation was probably the main cause of early failures with the Motec (Swemac AB, Linköbing, Sweden) cup design [30, 31].…”

High revision rates with the metal-on-metal Motec carpometacarpal joint prosthesis

“…Design and poor primary press fit fixation leading to lack of osteointegration has been proposed as a reason for early cup loosening (Hansen and Snerum, 2008;Hansen et al, 2011;Thorkildsen et al, 2013), whereas late loosening may be caused by a local reaction to metal particles (Fabi et al, 2012;Milosev et al, 2006;Willert et al, 2005).…”

“…In previous studies, the main reason for revision was loosening of the trapezium cup, which accounts for up to 76% of revisions (Hansen and Snerum, 2008; Hernandez-Cortes et al, 2012; Klahn et al, 2012). Design and poor primary press fit fixation leading to lack of osteointegration has been proposed as a reason for early cup loosening (Hansen and Snerum, 2008; Hansen et al, 2011; Thorkildsen et al, 2013), whereas late loosening may be caused by a local reaction to metal particles (Fabi et al, 2012; Milosev et al, 2006; Willert et al, 2005).…”

Joint replacement for trapeziometacarpal osteoarthritis: implants and outcomes

“…Several techniques used for the evaluation of large joint implants have been adapted to TMC joint implants. One method is finite element analysis, which is a computer-based simulation of load transfer from implants to the adjacent bone (Thorkildsen et al., 2013). Radiostereometric analysis is another method; it allows precise in vivo assessment of implant fixation.…”

“…In this way implant designs with a high risk of later aseptic loosening and need for revision can be detected within 2 years after operation rather than having to wait longer (Ryd et al., 1995). These techniques have helped understand the reasons for failure in some implant designs and taught us that trapezium components with a collar and a high centre of rotation, such as the Motec implant (Swemac AB, Linköbing, Sweden), carry an increased risk of failure (Thillemann et al., 2016; Thorkildsen et al., 2013). At present the implants with the best results are all collarless designs with a low centre of rotation in the cup.…”