Comparison of Vanguard XP and Vanguard CR Total Knee Arthroplasties. A Randomized Controlled Trial Evaluating Early Component Migration by RSA and Patient Reported Outcome.

In the history of TKA several different types of prosthetic designs have been evolved in order to optimize knee function after total knee replacement. The most common difference between the prosthetic designs revolves around issues concerning the preservation of the cruciate ligaments. The most popular prostheses have been the posterior stabilized prosthesis (PS) in which both cruciate ligaments are resected and the posterior cruciate retaining prosthesis (CR) in which only ACL is resected and PCL is preserved. Both these prosthetic designs have shown excellent clinical results in the literature.

In the knee the role of the cruciate ligaments is to insure anterior/posterior stability, but studies have also shown, that the cruciate ligaments contain proprioceptive mechanisms which control joint kinematics essential for accurate knee function. One could therefore imagine that a prosthetic design that preserves both cruciate ligaments would be superior to prosthetic designs in which ACL or ACL/PCL is resected in achieving good clinical results and patient satisfaction.

Only a few prosthetic designs, which preserve both cruciate ligaments, have been available to the market. However studies based on fluoroscopic assays and gait analysis has shown that this prosthetic design is superior to cruciate sacrificing designs in preserving normal knee kinematics during activities of daily living after TKA. Studies, in which patients have received two different types of prosthesis in each knee, have also shown that bi-cruciate retaining TKA's is preferred, when compared to more constrained prosthetic designs.

The new Vanguard XP TKA system (Biomet®, Warsaw, Indiana, USA) is a further development of the Vanguard TKA system, which has shown good clinical results in earlier studies. With the new Vanguard XP system both cruciate ligaments are preserved. In theory this should result in a more natural feeling of the knee because the stability and proprioceptive signals from both cruciate ligaments are preserved. In order to investigate the potential benefits of this new prosthetic design, the clinical and radiological results of knees receiving a Vanguard XP and Vanguard CR prostheses are compared.

In this study we wish to investigate:

1. If the use of the Vanguard XP prosthesis will influence the migration of the femur- and tibial components measured by Radiostereometric Analysis (RSA) when compared to the Vanguard CR prosthesis.
2. If the use of the Vanguard XP prosthesis will result in increased participant knee function, satisfaction and quality of life when compared to the Vanguard CR prosthesis.
3. If the use of the Vanguard XP prosthesis will influence radiologic signs of osteolysis, complication rates and revision rates when compared to the Vanguard CR prosthesis.

This project is carried out as a randomized controlled double-blinded trial, in which the clinical and radiological outcomes after treatment of knee osteoarthritis with insertion of either a Vanguard XP or Vanguard CR prosthesis is compared.