Minimally invasive surgery (MIS) for total knee replacement; medium term results with minimum five year follow-up

MIS TKA has been shown to offer a reduced in-patient stay, but no clinical difference at two years. Whilst there may be a benefit from earlier discharge, we need to ensure that there are no detrimental effects in the medium and long-term following MIS-TKA. To report the mid-term result from a prospective randomised controlled trial (RCT) comparing MIS-TKA with standard approach for TKA. Using knee score questionnaires, we collected patient reported outcome measures (PROMs) regarding pain and function. Sixty-six patients (from an eligible cohort of 83 patients) completed the mid-term postal follow-up. There was no significant difference between groups for change in score from pre-operative to final follow-up in all three PROMs. Mean MIS and standard group improvement was: AKSS 53 and 51 (p=0.7644), OKS 15 and 16 (p=0.2341) or WOMAC 15 and 15 (p=0.9900) respectively. Both groups showed improvement in pain and function with no significant difference between groups. There was no difference between groups for revision due to malalignment at a mean six year follow-up. In addition to the early benefits regarding hospital stay and complications, we have found that at a mean of six years there was no increase in malalignment, pain or function with MIS techniques.