Minimally invasive total knee arthroplasty; a pragmatic randomised controlled trial reporting outcomes up to 2 year follow up

Background: We present a prospective, randomised, multi-surgeon, controlled trial comparing minimally invasive (MIS) and standard approach total knee arthroplasty (TKA).

Methods: Participants underwent unilateral TKA. Patients were randomised to Bristol, quadriceps sparing MIS or standard medial parapatellar approaches. Length of stay with secondary outcome measures including knee range of movement, Oxford Knee Score (OKS), Western Ontario and McMaster Universities Arthritis Index (WOMAC) and American Knee Society Score (KSS) up to 2 years. Radiographic and post operative assessment was blinded.

Results: 86 patients (92 knees) participated in the study. Mean operative time between MIS and control groups was 95.5 (95% CI 90.0-101.0) and 94.8 (95% CI 88.2-101.4) minutes respectively. Mean readiness for discharge was shorter in the MIS group 4.5±1.5 (95% CI, 4.1-4.9) days versus 5.9±2.7 (95% CI, 5.1-6.7) days amongst controls (p=0.004). Patients in the MIS group had fewer complications (p=0.003). One patient developed a deep vein thrombosis (DVT) and one required revision surgery, both in the control group. 83 patients completed follow up to 2 years (40 MIS, 43 controls). Range of movement and other outcome measures improved up to 1 year post-operatively with no statistically significant differences between MIS and controls. We found no evidence of radiographic loosening in either group at the 2 year follow up.

Conclusions: MIS offers reduced length of stay and fewer complications for patients following TKR without evidence of component mal-alignment. Our findings of fewer systemic complications in MIS TKR patients warrant further future study.

Level of evidence: Level 1.