A prospective, randomized, single-blinded clinical trial is proposed to compare a
mobile-bearing total knee system with two types of fixed-bearing total knee systems in
patients undergoing cemented total knee arthroplasty. The devices to be used are FDA
approved: the Sigma Knee System (mobile-bearing), the Sigma, Pressfit Condylar posterior
cruciate substituting (fixed-bearing) system with a metal backed tibial tray, and the Sigma
press-fit condylar posterior cruciate substituting system (fixed bearing) with an all
polyethylene tibial tray.
Eighty cases will be assigned to each arm of the study. Each patient will be assessed two
months after surgery, one year after surgery, two years after surgery, five years after
surgery, and every three to five years thereafter. The principal outcome measures will be
the Knee Society Clinical rating scale and the SF-12. The result for these will be analyzed
using students' t-test analysis, taking into account classification by demographic
variables. Chi-square analysis will be used to compare the instance of mortality, revision
surgery, deep vein thrombosis, pulmonary embolus, neurovascular complication, and infection.
Other outcome measures incorporated in the Knee Society Clinical rating scale will undergo
appropriate generalized linear regression for the type of outcome involved.
Pain, weakness, instability, and progressive dysfunction are the hallmarks of arthritis of
the knee. Total knee replacement may frequently be the only therapeutic intervention to
provide adequate improvement in pain and function. Both fixed bearing and mobile bearing
knees have a long track record of clinical success. Mobile bearing designs have theoretical
advantages of decreased contact stresses on the tibial tray, decreased polyethylene wear,
and improved range of motion relative to fixed bearing designs. These theoretical
advantages may become especially important in the young patient who requires a knee
arthroplasty. This study will attempt to see if there is a clinical difference in outcome
between mobile bearing and fixed bearing knee arthroplasties in patients who require knee
- Patients 40 and 75 undergoing unilateral primary knee surgery for degenerative joint
- Age less than 40 years or 75.
- Severe deformity 20 varus, valgus malalignment.
- Osteomyelitis, septicemia, or other active infections that may spread to other areas
of the body.
- The presence of infections, highly communicable diseases, e.g. AIDS, active
tuberculosis, venereal disease, hepatitis.
- Significant neurological or musculoskeletal disorders or disease that may adversely
affect normal gait or weight bearing.
- Metastatic disease.
- Any congenital, developmental, or other bone disease or previous knee surgery that
may, in the surgeon's judgement, interfere with TK prosthesis survival or success,
e.g. Paget's disease, Charcot's disease secondary to diabetes, severe osteoporosis,
previous high tibial osteotomy, etc.
- Presence of previous prosthetic knee replacement device (any type).
- Arthrodesis of the affected knee.
- Patients not requiring patella resurfacing.