Migration of CS vs CR Insert in TKA Using RSA

Background:

The choice whether or not to preserve the posterior cruciate ligament (PCL) in total knee arthroplasty (TKA) is coupled to the us of a PCL-retaining (CR) or a condylar (CS) insert. The CS insert is anterior-lipped (AL) to prevent anterior translation of the femur on the tibia with flexion and compensate the function of the PCL. Currently both the CR and CS insert are made of highly cross-linked polyethylene (HXPLE) to theoretically reduce wear related osteolysis. However, this also might diminish the fracture toughness and crack propagation of the insert. The investigators expect that due to the high contact forces on the anterior lip of the CS insert during flexion, especially in younger and more active patients, and the lower fracture toughness of HXPLE, the CS insert insert might show more migration, wear or other damage compared to the CR insert in the long-term, which might lead to more revisions in the CS insert compared to the CR insert.

To measure the migration and wear, 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 tantalum markers ande the inserter are already used for study purposes. However, the safety and usability are not registered before.

Objective:

The primary objective is to compare the migration of both the femoral and tibial component by the use of a CS insert or CR insert both made of HXPLE using model-based roentgen stereophotogrammetric analysis (mRSA). Furthermore, the safety and usability of the tantalum markers and the marker inserter will be determined. The secondary objective is to determine the influence of the type of insert on the wear, inducible displacement, survival and clinical outcomes.

Study design:

A randomized controlled trial

Study population:

Forty-four patients scheduled to undergo primary total knee replacement, aged below 70 years with an ASA-score of 1 or 2 will be needed in total, divided in two groups of 22 patients each.

Intervention:

One group receives an uncemented TKP with a CS insert, while the other group receives an uncemented TKP with a CR insert. Both will be placed using the MAKO-robotic arm using a kinematic balancing technique.

Outcomes:

Main study parameters are migration of the femoral and tibial components measured with model-based RSA software till 10 years postoperatively. Furthermore, the stability of the markers will be determined and the complications due to the markers and/or the marker inserter will be registered. The secondary parameters are wear, inducible displacement, survival, clinical outcomes and complications up to 10 years postoperatively.