Background: Durable long-term independent results with the Low
Contact Stress rotating-platform (mobile-bearing) and the Insall Burstein-II
(fixed-bearing) total knee prostheses have been reported, but no studies
describing either the mid-term or long-term results and comparing the two
prostheses are available, to our knowledge.
Methods: Thirty-two patients who had bilateral arthritis of the knee
with similar deformity and preoperative range of motion on both sides and who
agreed to have one knee replaced with a mobile-bearing total knee design and
the other with a fixed-bearing design were prospectively evaluated.
Comparative analysis of both designs was done at a mean follow-up period of
six years, minimizing patient, surgeon, and observer-related bias. Clinical
and radiographic outcome, survival, and complication rates were compared.
Results: Patients with osteoarthritis had better function scores and
range of motion compared with patients with rheumatoid arthritis. However,
with the numbers available, no benefit of mobile-bearing over fixed-bearing
designs could be demonstrated with respect to Knee Society scores, range of
flexion, subject preference, or patellofemoral complication rates. Radiographs
showed no difference in prosthetic alignment. Two knees with a mobile-bearing
prosthesis required a reoperation: one had an early revision because of
bearing dislocation and another required conversion to an arthrodesis to treat
a deep infection.
Conclusions: We found no advantage of the mobile-bearing
arthroplasty over the fixed-bearing arthroplasty with regard to the clinical
results at mid-term follow-up. The risk of bearing subluxation and dislocation
in knees with the mobile-bearing prosthesis is a cause for concern and may
necessitate early revision.
Level of Evidence: Therapeutic Level II. See Instructions
to Authors for a complete description of levels of evidence.