The purpose of this study is to compare the early migration of two uncemented total knee arthroplasties with different metalcoating. 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.

Condition	Intervention
Osteoarthritis	Device: NexGen TKA; tantalum monobloc vs modular titanium fibermesh.

Further Study Details: 

Primary Outcomes: Tibial prostesis part migration evaluated by RSA.
Secondary Outcomes: Micromotion of the polyethylen liner in the modular titanium fibermesh prostesis versus the monobloc tantalum prostesis evaluated by RSA.
Expected Total Enrollment:  50

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 metalcoating and fixationmethod. 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 polyethylen 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 polyethylen-prosthesis micromovements metal markers have been placed on the prosthesis pre-operatively and furthermore into the tibial bone and into the tibial polyethylen intra-operatively 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 and 2 years post-surgery.

Ages Eligible for Study:  18 Years   -   70 Years,  Genders Eligible for Study:  Both

Criteria

Inclusion Criteria:

1. Patients with one- or double-sided primary kneearthrosis.
2. Patients with a sufficient bone quality for implantation of an uncemented prosthesis.
3. Informed and written patient consent.

Exclusion Criteria:

1. Patients with neuromuscular or vascular diseases in the affected leg.
2. Patients who peroperatively are estimated unsuitable for an uncemented knee arthroplasty e.g. due to bone cysts or dilution of the bone mass.
3. Patients who use non-steroid anti-inflammatory drugs (NSAID) and cannot refrain from taking them postoperatively (this includes COX-2-inhibitors).
4. Patients with osteoporosis estimated from the preoperative x-ray or former diagnosis of osteoporosis.
5. Patients with fracture sequelae.
6. Women, who are pregnant or are at risk of getting pregnant.

Denmark
      Orthopaedic Center, Aarhus University Hospital., Aarhus,  8000,  Denmark

Study chairs or principal investigators

Kjeld Søballe, MD, Prof.,  Principal Investigator,  Orthopaedic Center, Aarhus University Hospital, Tage-Hansens Gade 2, 8000 Aarhus C, Denmark.   

Study ID Numbers:  20030119
Last Updated:  August 29, 2005
Record first received:  August 29, 2005
ClinicalTrials.gov Identifier:  NCT00138853
Health Authority: Denmark: The Danish National Committee on Biomedical Research Ethics
ClinicalTrials.gov processed this record on 2005-08-30