Is a minimally invasive approach superior to a conventional approach for total knee arthroplasty? Early outcome and 2- to 4-year follow-up.

BACKGROUND: Total knee arthroplasty (TKA) has been widely applied as an effective treatment for knee arthritis for several decades. More recently, minimally invasive surgery (MIS) has been developed for TKA. The purpose of this study was to clarify the difference in clinical results between MIS and conventional TKA. We hypothesized that knee function would recover earlier with MIS than with conventional TKA without major problems, and hence the middle-term outcome would be better with MIS TKA.

METHODS: We retrospectively reviewed 48 primary TKAs performed using the same model of a posterior stabilized prosthesis by a single surgeon at our institution: 25 knees treated by a mini midvastus approach (MIS group) and 23 knees treated by a conventional midvastus approach (conventional group). Outcomes at the early stage and at the 2- to 4-year follow-up were evaluated and compared between the two groups.

RESULTS: The average length of the skin incision was 10.9 cm in the MIS group and 17.1 cm in the conventional group. The duration of the surgery did not differ significantly between the two groups. Most of the components were correctly implanted in both groups, and no complications were observed. Active straight-leg raising could be achieved significantly earlier in the MIS group. Knee function at the 2- to 4-year follow-up did not significantly differ between the two groups.

CONCLUSIONS: The early results and the wide indication encourage us to apply the MIS approach instead of the conventional technique. The limitation of this study was the small number of cases in the retrospective point of view. If the number were larger, perhaps other significant differences could be detected. Further investigations on a larger scale are required to solve this problem.