151 survivorship analysis of total knee arthroplasty: effect of anatomic vs mechanical alignment

Purpose of study Longevity of implant survival following total knee arthroplasty (TKA) depends on a variety of factors, with implant alignment being a major element. It is a long-held belief that a neutral mechanical knee alignment will maximise implant survival. However, 32% of men and 17% of women have constitutionally varus knees prior to surgery and may have discomfort with or without implant failure when placed in a neutral alignment. This thought has led to increasing interest in a more anatomic approach to knee implantation. This retrospective study examined long-term survivorship of total knee implants in relation to their pre- and post-operative alignments. Methods used Chart reviews were conducted on patients who previously underwent a total knee arthroplasty between 1999 and 2013. Pre- and post-operative long-standing anteroposterior radiographs were reviewed and the following measurements were made on each radiograph: Summary of results There were 300 knees included in this study. Out of the 32 implants that were identified as failure, 14 were excluded because the need for revision was not mechanical in nature. A statistically significant difference was found between the post-operative mechanical alignment and survivorship (p=0.025), which favours a more neutral alignment. The post-operative anatomic tibiofemoral alignment and survivorship was also significant (p=0.011), favouring a more natural valgus alignment. Conclusions Total knee implant survivorship is improved with a natural mechanical knee alignment for the mechanical angle and anatomic tibiofemoral angle.