Abstract
From 1985 through 1997, 56 isolated tibial insert exchange revisions were performed at our institution. Fifty-five patients with wear or instability were included. Those with loosening of any of the components, history of infection, severe knee stiffness or problems with the extensor mechanism were excluded. There were 29 males (1 bilateral) and 26 female patients with a mean age of 66 years (range 35 to 83 years) at the time of revision surgery. Twenty-seven inserts were exchanged based on ligamentous instability, 24 because of insert wear or breakage including two cases of polyethylene dislodgment from the tibial base-plate and 5 for other reasons. Twelve knees had one to three prior revisions. Surveillance from index arthroplasty averaged 8.3 years (range 1.6 to 16.2 years) and since revision 4.6 years (range 2 to 14 years).
Knee Society and Function Scores improved from 56 and 50.9 prior to revision to 76 and 59 at final surveillance respectively. Fourteen (25%) of the 56 knees subsequently required re-revision after a mean of only three years (0.5–6.8) from tibial insert exchange. The cumulative survival at 5.5 years was 63.5% (95%CI=+/−14.4, n=19). Of the 27 patients with pre-operative instability, eight were revised and another four were considered as failures due to severe pain. Of the 24 failed inserts, five were re-revised, one was amputated as a result of chronic ankle osteomyelitis concomitant to a chronically painful arthroplasty, and another two inserts failed due to severe pain.
Isolated tibial insert exchange led to a surprisingly high early failure rate. Tibial insert exchange should therefore be undertaken with caution as an isolated method of total knee revision surgery even in those circumstances for which the modular insert was designed and felt to be of greatest value.
