Comparison of Mobile-Bearing and Fixed-Bearing All-Polyethylene Tibia Total Knee Designs

This study will be designed to compare prospectively, in a randomized fashion, the clinical, functional, and radiographic results of a nonmodular (all-polyethylene tibi/AP) fixed-bearing posterior cruciate substituting design with a modular posterior cruciate substituting rotating platform (RP) design for total knee arthroplasty. Comparing these two designs will afford the investigators information in the following areas:

1. Does a RP design offer improvement in range of motion over a AP design?
2. Does a RP design have improved wear characteristics over a nonmodular AP design?
3. Is there a clear clinical advantage to the RP design that justifies its increased cost?

Answering these questions will allow surgeons to use RP designs appropriately in different demand populations.

This study was designed to address the questions of whether an RP design offers improvement in ROM, Knee Society scores, Western Ontario and McMaster Universities Index of Osteoarthritis (WOMAC) scores, selected Medical Outcomes Short-Form Health Survey Short Form-36 (SF-36) scores or radiographic measures, over an APT design. The investigators' primary hypothesis was that there would be no difference in these outcome measures at a minimum two year followup. A secondary hypothesis based on the anticipated long-term followup of this group was that there would be no difference in implant survival.

• Procedure: TKA surgery with the rotating platform mobile-bearing knee design
  Depuy Sigma RP rotating platform design
• Procedure: TKA surgery with the all-polyethylene tibia knee design
  Depuy Sigma fixed-bearing design with all-polyethylene tibia

• Active Comparator: rotating-platform design TKA
  patients who were randomized to receive the rotating platform mobile-bearing TKA design
  Intervention: Procedure: TKA surgery with the rotating platform mobile-bearing knee design
• Active Comparator: all-polyethylene tibia design TKA
  patients who were randomized to receive the all-polyethylene tibial component design
  Intervention: Procedure: TKA surgery with the all-polyethylene tibia knee design

Inclusion Criteria:

• generally accepted clinical and radiographic criteria for primary total knee arthroplasty

Exclusion Criteria:

• substantial angular deformity or bony deformity requiring structural grafting or modular augmentation were excluded at the discretion of the principle investigator
• patients whose mental function precluded them from responding to our standard questionnaires