Migration of the Restoris MultiCompartmental Knee Implant System in robotic-assisted unicompartmental knee arthroplasty: a 5 year follow up RSA study

Patients with isolated medial compartment arthritis of the knee are commonly
treated with unicompartmental knee arthroplasty (UKA). In contrast with total
knee arthroplasty (TKA), UKA shows a higher revision rate, which might be due
to implant malpositioning and postoperative malalignment of the lower limb and
incorrect soft tissue balancing. Nowadays, robotic-assisted UKA is used to
improve accurate positioning, optimize soft-tissue balancing, optimize
radiographic alignment of the implant, which also might improve functional
outcome and survivorship in long-term.

As there is a lack in long-term results, more research is needed to the
long-term results of robotic-assisted UKA. As long-term results are related to
early migration of the implant, investigating the early migration will have
additional value to predict the long-term results of robotic-assisted UKA. In
this study, we will investigate the early migration of a unicompartmental knee
implant (Restoris MultiCompartmental Knee Implant System (Restoris MCK)) used
in robotic-assisted UKA and we will relate the migration of this implant to the
long-term results of the implant. The migration will be measured using
model-based roentgen stereophotogrammetric analysis (mRSA), which is a very
accurate, 3-dimensional method to measure the migration relative to the bone.

To measure the migration, during surgery tantalum markers will be inserted in
the host bone using a marker inserter. The displacement of the prosthesis with
reference to the host bone will be measured using model-based RSA. Both the
tantalum markers and the inserter are already used for study purposes. However,
the safety and usability are not registered before.

The primary objective is to assess the fixation and migration patterns of the
Restoris MutliCompartmental Knee Implant System (Stryker) in vivo, using mRSA,
over 5 years. Furthermore, the safety and usability of the tantalum markers and
the marker inserter will be determined. Secondary objectives are to analyse
alignment, survival, clinical scores and radiographic aspects of the Restoris
MultiCompartmental Knee Implant System (Stryker) and to relate these to the
migration patterns over 5 years.

A prospective cohort study in the Reinier Haga Orthopedisch Centrum,
Zoetermeer, the Netherlands. Patients will be asked to participate and will be
followed during 5 years. Patients will be evaluated preoperatively, at 6 weeks,
6 months, 1 year, 2 years and 5 years postoperatively.

Patients participating in the study will have the same risks when not
participating in the study. Patients are asked to spend time to fill in the
questionnaires and to have 2 extra visits to the hospital, next to the standard
visits.Participating patients have more follow up visits, which has as
advantage that possible complications might be noticed earlier compared to
normal follow up.

The markers and marker inserter are used before without any problems in
comparable studies.