A Roentgen Stereophotogrammetric Analysis on Migration of Knee Prostheses.
Condition: Osteoarthritis
MeSH terms: Osteoarthritis
Study type: Interventional

Summary: 
      The purpose of this study is to compare the early migration of two uncemented total knee
      arthroplasties with different metal coating. Only the tibial prosthesis plateau varies. One
      is made out of tantalum and has two short pegs for fixation into the tibia while the other is
      covered by titanium fiber-mesh on the bone-near site and has 4 short pegs for screw fixation
      into the tibia.
    

Detailed description: 
      Around 4% of total knee arthroplasties (TKA) are revised 15 years after the primary
      operation, most due to loosening of the implant. The use of uncemented prostheses are
      expected to extend the fixation time and thereby the years of TKA survival. When a cementless
      implant is inserted, direct bone ingrowth to the implant depends on a complete primary
      stabilisation. Movement between the bone and implant will cause a fibrous membrane leading to
      micromotions. Micromotions can be evaluated by radiophotogrammetric analysis (RSA) in early
      follow-up and they have been shown to be a prognostic marker for painful loosening of the
      implant.

      Tantalum is a fairly new biomaterial designed with a high and bone-binding porosity. Tantalum
      has already proven to be a good prosthesis material facilitating fast bone-ingrowth and
      supplying mechanical qualities in the bone-prosthesis interface that surpasses the qualities
      of regular prosthesis materials by uncemented method. Titanium on the other hand has been
      used as a prosthesis coating for years and also promote prosthesis fixation by
      osteointegration.

      The purpose of this study is to compare the early migration of two uncemented total knee
      implants with different metal coating and fixation method. Only the tibial prosthesis plateau
      varies in design. One plateau is a 2 pegged tantalum monobloc and the other plateau is a
      modular titanium fiber-mesh coating with 4 short pegs for screw fixation into the tibia.

      Furthermore the extend of the expected micromovements between the polyethylene liner and the
      metal backing of the titanium plateau will be compared to the stable tantalum monobloc.

      Theoretically tantalum should allow a more optimal coating for bone ingrowth, but as primary
      stability is also important for longterm prostheses survival the method of primary fixation
      could alså play a role.

      To evaluate both the plateau-bone micromotions and the polyethylene-prosthesis micromovements
      metal markers have been placed on the prosthesis pre-operatively and furthermore into the
      tibial bone and into the tibial polyethylene during surgery allowing us to evaluate stereo
      x-rays by a photogrammetric analyses called RSA at the Orthopaedic Center, Aarhus University
      Hospital. Follow-up stereo x-rays will be scheduled for 1 week, 3 months, 6 month, 1 years, 2
      years and 5 years post-surgery.
    

Intervention name(s): Tibial component
Intervention type(s): Device
Intervention description(s): Tibial component inserted at the time of surgery
Other intervention name(s): NexGen Tantalum Tibial Plate; NexGen Titanium Tibial Plate, screw fixed
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: RSA; Genoarthrosis; Knee arthroplasty; Micromotion of polyethylene liner