On New Implants - The results of five prospective, randomized RSA trials with aspects on phased introduction and continuous migration

Sammanfattning: A concern that arises with any change in design or operative technique is whether it affects the long-term implant stability or not. One way to address this is, by measuring early micromotion, to predict the future revision rate. This study was set to evaluate the early migration and the functional outcome of the Triathlon™ total knee arthroplasty system in different subsets of design. In addition, two methods of predicting the risk of future revision were investigated. Each paper consisted of 60 patients, prospectively randomized into two groups. The three-dimensional tibia component migration was measured by radiostereometric analysis at three months and at one, two, and also at five years in Paper VI. Clinical outcome was measured by the American Knee Society Score and Knee Osteoarthritis and Injury Outcome Score, with an addition of EQ-5D in Paper II, at three months and one and two years. Comparisons were made between the Triathlon™ vs its predecessor the Duracon® total knee prosthesis (Papers I and VI), with vs without perioperative tourniquet (Paper II), the posterior stabilized vs the cruciate retaining design (Paper III), the non-cemented press fit vs Peri-Apatite designs (Paper IV) and the standard tibia stem design vs the short stem (Paper V). There was no difference in mean maximum total point motion (MTPM), when comparing groups over two (Papers I-III, V) or five years (Paper VI), except for the mean MTPM reported in Paper IV. There was no major difference in patient related outcome. The predicted future risk of revision for all designs was a > 5 % risk of revision at ten years when analyzed at one year according to Pijls et al., and < 5 % when analyzed at two years according to Ryd et al. (Ryd, Albrektsson et al. 1995, Pijls, Valstar et al. 2012). The five year result of continuous migration (Paper VI) concluded that the cemented Triathlon™ CR is as safe to use as its predecessor, the Duracon® (< 5 %). Key words New total knee arthroplasty, TKA, RSA, randomized, prospective, prediction, continuously migrating, safety, stability CR, PS, PF, PA, short stem, tourniquet.