Trabecular Metal Mesh Tibial Monoblock RSA
Condition: Osteoarthritis
MeSH terms: Osteoarthritis
Study type: Interventional

Summary: 
      Trabecular Metal(TM) is a relatively new technology and its use in knee replacement is quite
      different from the more conventional total knee replacement (arthroplastie). The aim of
      incorporating TMM into the material used for the knee replacement (tibial prostheses) is to
      improve initial fixation of the prosthesis at the time of implantation (surgery) and to
      improve long term prosthesis survival by encouraging and improving bone ingrowth.
    

Detailed description: 
      Hip and knee replacement arthroplasty are profoundly successful operative interventions,
      however, some joint replacements do fail and the life expectancy of a hip or knee
      arthroplasty is finite (Malchau et al. 1993, Knutson et al. 1994, Herberts et al. 1997,
      Garellick et al. 1998). This fact has largely been responsible for the continued development
      of new devices and techniques for joint arthroplasty surgery. Unfortunately, the introduction
      of new technologies and devices is not a benign process, and even subtle changes to existing
      implants can have a disastrous effect on patient outcome (Sudmann et al. 1983, Herberts P.
      1986, Ohlin et al. 1989, Wedderkopp et al. 1997, Howie et al. 1998, Nilsson et al. 1998).

      The fact that new technologies and devices can lead to poor results has led some authors to
      advocate a phased introduction of new technologies (Gross 1988, Gross 1993, Malchau 1999). A
      key component of the phased introduction approach advocates the use of roentgen
      stereophotogrammetric analysis (RSA) early in the testing process (Malchau 1999).

      RSA is a highly accurate radiographic technique developed in Lund, Sweden and has for some
      time been the gold standard in Europe for assessing the stability of implants within bone
      (Selvik 1990, Ryd 1992, Catani et al. 1998, Alfaro-Adrian et al. 1999). It is at least ten
      times more accurate than conventional radiography (Ryd et al. 1986). RSA involves the
      insertion of small tantalum markers (0.8mm) into the bone and prosthesis at the time of
      surgery (Ryd 1986, Ryd et al. 1986, Ryd et al. 1989, Selvik 1990, Ryd 1992). By using a
      calibrated cage with additional markers and simultaneous bi-planar x-rays, micromotion at the
      prosthesis-bone interface can be very precisely determined (Selvik et al. 1983). Two types of
      micromotion can be investigated: migration, i.e. gradual motion over time, and inducible
      displacement, i.e. instant motion in response to external forces (Ryd et al. 1986). The
      pattern of micromotion exhibited by various prostheses and fixation techniques within the
      first post-operative year has been shown to be predictive of the long-term fixation of the
      component to bone, especially when considering the tibial prosthesis-bone interface (Ryd
      1986, Ryd et al. 1986, Ryd 1992, Ryd et al. 1995). The value of this precise radiographic
      technique is that new technologies and techniques can be introduced in vivo while limiting
      their exposure to as few patients as possible. RSA is a proven, safe and invaluable method
      for assessing methods of tibial component fixation as well as different design concepts (Ryd
      et al. 1987, Nilsson et al. 1991, Ryd et al. 1992, Ryd et al. 1993, Hilding et al. 1995,
      Onsten et al. 1998, Nilsson et al. 1999).

      Until recently, RSA technology has been cumbersome and expensive. However, significant
      advances have made the system more applicable due to the fact that digitized films are being
      used, and computer programs have been written and can run on small personal computers that
      will allow for automatic capture and interpretation of x-ray markers and implants (Vrooman et
      al. 1998).

      Trabecular Metal(TM) is a relatively new technology and its use in tibial knee arthroplasty
      components represents a significant departure from conventional total knee arthroplasties. TM
      has a high co-efficient of friction and high affinity for bone ingrowth (Bobyn et al. 1999a,
      Bobyn et al. 1999b, Hacking et al. 2000), subsequently, the aims of incorporating TMM into
      tibial prostheses is to improve initial fixation of the tibial prosthesis at the time of
      implantation and to improve long term prosthesis survival by facilitating bone ingrowth. Such
      advantages remain, however, theoretical, and have yet to be demonstrated in vivo for total
      knee arthroplasty. With conventional study techniques, a definitive answer to the effect of
      the prosthetic design on fixation of the tibial component would require a large number of
      patients and approximately 10 years of follow-up (Ryd 1992, Ryd et al. 1995). RSA provides a
      means of accurately assessing the tibial component fixation, both immediate and long term, on
      a relatively small number of patients within two years of the onset of the study. It is
      critical at this stage to determine the long-term effect of this design concept on component
      fixation so that any deleterious effects can be addressed and any advantageous effects can be
      disseminated to the orthopaedic community.
    

Intervention name(s): Trabecular Metal Mesh Tibial Monoblock Knee Arthroplasty
Intervention type(s): Device
Intervention description(s): new porous metal tibial component with potential to result in improved bone in-growth and implant integration with proximal tibia
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: arthroplasty; RSA; Osteoarthritis; trabecular metal mesh