Comparison of a mobile with a fixed-bearing unicompartmental knee implant.
Two well-matched groups of patients with unicompartmental knee arthroplasties were compared. The first 51 knees were treated with a fixed-bearing knee implant and the second 50 knees were treated with a mobile meniscal-bearing implant. Followup was 7.7 years for the patients with fixed-bearing implants and 6.8 years for patients with mobile-bearing implants. Both groups functioned well clinically. Radiographic analysis with 3-foot standing views taken preoperatively showed both groups had an average varus alignment of -2 degrees. Postoperatively patients with fixed-bearing implants had an average +2.6 degrees alignment and the patients with mobile-bearing implants had +5.5 degrees alignment, which was significantly different. Survivorship analysis based on component loosening and revision showed a 99% survival for the meniscal-bearing implant and 93% survival for the fixed-bearing implant at 11 years. However, the fixed-bearing knee implants failed significantly more often because of tibial component failure, in six of eight knees, at an average of 6.3 years. The mobile-bearing implants showed a trend to fail because of arthritic degeneration in the lateral compartment, at an average of 10 years, although not statistically significant. The mobile-bearing implants had no tibial component failures. These differences may be attributable to implant design or surgical technique.
Emerson
Roger H
RH
Texas Center for Joint Replacement, Plano, 75093-7732, USA. rhemersonjr@msn.com
Hansborough
Thomas
T
Reitman
Richard D
RD
Rosenfeldt
Wolfgang
W
Higgins
Linda L
LL
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016019:Survival Analysis