Survivorship and relative risk of revision in computer-navigated versus conventional total knee replacement at 8-year follow-up

Background and purpose — The long-term effects of computer- assisted surgery in total knee replacement (CAS) compared to conventionally operated knee replacement (CON) are still not clear. We compared survivorship and relative risk of revision in CAS and CON based on data from the Norwegian Arthroplasty Register. Patients and methods — We assessed primary total knee replacements without patellar resurfacing reported to the Norwe- gian Arthroplasty Register from 2005 through 2014. The 5 most used implants and the 3 most common navigation systems were included. The groups (CAS, n = 3,665; CON, n = 20,019) were compared using a Cox regression analysis adjusted for age, sex, ASA category, prosthesis brand, fi xation method, previous sur- gery, and diagnosis with the risk of revision for any reason as end- point. Secondary outcomes were reasons for revision and effects of prosthesis brand, fi xation method, age (± 65 years), and hospi- tal volume. Results — Prosthesis survival and risk of revision were similar for CAS and CON. CAS had signifi cantly fewer revisions due to malalignment. Otherwise, no statistically signifi cant difference was found between the groups in analyses of secondary outcomes. Mean operating time was 13 minutes longer in CAS. Interpretation — At 8 years of follow-up, CAS and CON had similar rates of overall revision, but CAS had fewer revisions due to malalignment. According to our fi ndings, the benefi ts of CAS at medium-term follow-up are limited. Further research may iden- tify subgroups that benefi t from CAS, and it should also empha- size patient-reported outcomes.