Introduction

Restoration of mechanical axis is one of the main aims during Total Knee Arthroplasty (TKA) surgery. Treatment of osteoarthritis (OA) of the knee with extra-articular deformity either in femur or in tibia poses a technical challenge in achieving this aim. Insufficient correction of axis is associated with poor clinical outcome of total knee arthroplasty (TKA). Extra-articular deformity can either be addressed with compensatory intra-articular bone resection at the time of TKA or correctional osteotomy prior to or at the time of TKA.

Aim: To assess the safety and efficacy of a mini-incision surgical (MIS) approach to knee arthroplasty (TKA) compared to a traditional standard approach.

Background: TKA through less invasive approaches have become increasingly popular in recent years. These range from smaller skin incisions to the ‘quadriceps-sparing’ procedures. Claims of improved recovery time and other clinical/economic advantages have been tempered by concerns about the safety of such procedures. This study was designed to evaluate any potential advantages of a specific approach (MIS) whilst studying peri-operative, radiological and outcome data to examine procedural safety.

Patients and Methods: 80 patients undergoing TKA were randomised to a standard or MIS (mini-midvastus) approach. The latter involved patella subluxation, rather than eversion. The operative, anaesthetic and post-operative treatments were standardised including rehabilitation protocols. Strict discharge criteria were established and independently verified and patients were discharged directly to their homes capable of independent care. Specifically the study evaluated patient demographics, operative time, blood loss and hospital stay. Outcome data including Knee Society Scores, Oxford Knee Scores and SF36 were recorded regularly in the early recovery period and up to 1 year post-operatively. Independent radiological review of implant positioning and alignment was obtained.

Results: There were no significant differences in operative time, blood loss, or other intra-operative data. Accelerated discharge was achieved in both groups (compared to historic data), however the length of stay (LOS) was significantly shorter in the MIS patients (mean – 3.5 days compared with 4.4 days in the standard patients). There was no statistical difference in clinical outcome analyses between the groups.

Discussion: Less invasive approaches to TKA have been reported over recent years but most studies have been anecdotal comparing patient recovery with historic controls which potentially can exaggerate clinical and economic benefits. Concerns have also been raised regarding the safety of these modified procedures. This study demonstrates a reduction in hospital stay and recovery in all patients as a result of accelerated rehabilitation. The MIS patients benefited from an additional significant reduction length of stay compared to controls with no evidence of compromise in terms of safety or efficacy.

Conclusions: This study has demonstrated the safety of the MIS mini-midvastus approach and a clear reduction in hospital length of stay. MIS surgery can offer substantial clinical and economic benefits but procedures must be closely evaluated to ensure equivalent or enhanced outcomes are achieved.