Fixation of the Simpliciti stemless humeral component, a radio-stereophotogrammatic analysis

In shoulder arthroplasty the use of Roentgen Stereometric Analysis (RSA), a
highly accurate three dimensional method to quantify the motion between an
implant and the host bone (Selvik 1989), is rare. Shoulder arthroplasty has
traditionally been designed as a stemmed device relying on intramedullary
fixation for its stability. Unfortunately drawbacks in stemmed arthoplasty
devices are caused by stress-shielding1, stress risers, fractures and the need
for modularity due to variable anatomy. Therefore, in shoulder arthroplasty
short stem devices are developed. These short stem devices have been proven
that fixation of the humeral component is not compromised due to a shorter stem
(2). However, a reduced area of fixation, like the stemless design, can
hypothetically show compromised fixation in the initial or long term. To
quantify if motion between a stemless design and the host bone occurs Roentgen
Stereometric Analysis (RSA) can be used.
RSA is a highly accurate, three dimensional method to quantify the motion
between an implant and the host bone (Selvik 1989). Since its introduction RSA
have been widely used in the assessment of hip en knee joint replacements.
Using RSA the risk of implanting potentially inferior prostheses will be
reduced, resulting in better implants used in patients that needs arthoplasty.
In the assessment of RSA spherical tantalum markers are inserted into the bone.
Two radiographs are taken simultaneously for precise 3D determination of the
tantalum markers and the implant. The radiographs are then analysed by RSA
software by computer. Using reference markers, relative translations, rotations
and micromotion of the implant can be exactly measured.
In this study, we identify the fixation and migration patterns of the
Simplicity (Tornier, France) stemless humeral component using RSA. The
Simplicity stemless humeral design has already clinically been proven to be
promising design. Using RSA we can accurately and quantitative evaluate this
implant design and micromotion of the stemless component in patients that needs
shoulder arthroplasty. We hypothesise that the simplicity stemless humeral
component is a stable implant with minimal translation, rotation and
micromotion.

Primary objective:
Identifying the fixation and migration patterns of the Simplicity (Tornier,
France) stem less humeral component in vivo, using model based
radiostereophotogrammetric (mRSA) analysis.

Secondary objective:
To evaluate the mid and long term clinical results ( NRS for pain, Range of
motion, Constant score, SF-36, Dash and radiographs) in an on-going follow-up,
and correlate the clinical results to the RSA migration data.

Monocenter Prospective Cohort study
Participating centers / groups:
- Reinier de Graaf gasthuis (Delft, the Netherlands

The Simpliciti shoulder prosthesis used in primary total shoulder arthroplasty.

no risks nor burden associated with participation. Non applicable. see section
5.2 METC protocol.