This multicenter study compared computer-navigated TKA using either MIS or conventional surgical technique, using a CR fixed bearing knee, Stryker Navigation system and dedicated MIS instrumentation. It was hypothesized that patients would benefit from the MIS technique by shorter recovery periods, less blood loss, faster wound healing and improved mobility during early rehabilitation.

A prospective multicentre double-blind controlled trial included 69 patients matched for age, gender, BMI (MIS n=36, CONV n=33). Assessments at pre-op, 1 week, 3 and 6 months post-op included surgery time, bloodloss, range of motion, Knee Society Score (KSS) and WOMAC, Chair rise test and quadriceps strength. Radiographic analysis included radiographs for lucencies and CAT scans for alignment,

Four patients were lost to follow-up. The MIS group had significantly more prolonged surgery time and blood loss at 24 hours p<0.05. At 6 months mean flexion values for MIS (106,7°±12,91) and CONV 105,92 ±11,58) with no significant differences in flexion ROM between both groups at any time point. KSS scores showed a significant improvement (p<0,01) over time in both groups but no statistical significance between groups. WOMAC score also improved significantly (p<0,01) over time in both groups without reaching statistical significance. A significant decrease of anterior knee pain score was observed over time with no significant difference between both groups. Quadriceps strength recovery was not significant between groups but trended toward faster recovery in the MIS group. X-rays showed stable implants with no progressive radiolucent lines in all patients.

The hypothesis that patients benefit from the MIS technique in the short term was not confirmed by the results of this study. The MIS surgery technique resulted in more blood loss intra-op and in the first 24hours post op as well as an elongated surgery time. The MIS surgery technique also failed to generate clear advantages in clinical or functional outcome that persisted over time.