Summary

No difference in patient reported outcome measures at 6 months follow-up between restricted kinematically aligned and mechanically aligned bilateral simultaneous Total knee arthroplasty.

Abstract

Introduction

A recent focus on total knee arthroplasty (TKA) is primarily directed toward restoring natural knee kinematics, thereby improving the gait parameters and targeting better patient-reported outcomes. However, it has also been considered that correcting the full varus by kinematic alignment may lead to more stress on the medial tibial insert in severe varus-aligned knees, increasing the chances of early failure. The restricted kinematic alignment (rKA) technique is thus a midway between true kinematic and conventional mechanical alignment. Restoring some amount of varus alignment by the rKA technique will allow the patient a native feel of the joint without the expense of excess stress on the implants and thus may improve the overall outcomes after knee arthroplasty. This study aims primarily to compare patient-reported outcome measures (PROMs) for conventional Mechanically Aligned (MA-TKA) with restricted Kinematically Aligned (rKA-TKA). Methodology: A prospective double-blinded split body, non-inferiority trial was conducted following CONSORT protocol among 38 patients (76 knees) undergoing simultaneous bilateral TKA. Each blinded patient had one knee operated by crKA-TKA and the contralateral by MA-TKA. The trial was registered in the clinical trial registry of India. The institutional ethics board approved the study, and all patients consented to participate before enrolling. Group 1 had 38 knees operated by crKA-TKA, and Group 2 had 38 knees operated by cMA-TKA. A blinded observer collected all patient-reported outcome measures. We used MediCAD Hectec Gmbh (Germany) software for pre-operative planning for all our patients before randomisation. A single orthopaedic trainee resident doctor performed all pre-operative planning on the software, with each knee being planned for both MA and rKA protocols. Tibial cuts and femoral alignments were planned using this software so that coronal angular alignment can be achieved post-operatively. The randomisation plan and the allotment sequence were concealed from the operating surgeon until the morning of surgery. All patients received Attune Cemented PS implants (Depuy Synthes) without patellar resurfacing. PROMs for each patient were analysed according to either knee being in MA or rKA protocol. The minimum follow-up duration was six months post-surgery. Results : No statistically significant difference between PROMs like VAS score for knee pain (p=0.609), ROM (p=0.501), knee society score (p= 0.08), OKS (p=0.648), WOMAC (p= 0.18), FJS-12 score (p = 0.66), and Satisfaction level Scale between the two knees (p=0.194). Post-operatively UCLA activity score (p = 0.02) and Quality of life score like SF-36 (p = 0.014) showed statistically significant improvement from its pre-operative values. Conclusion: This present clinical trial highlights non-inferior patient reported outcomes of rKA-TKA when compared to standard conventional MA-TKA at a short-term follow-up of six months. The study further establishes that the method of callipered technique in TKA using a routine digital templating software and standard instrumentations is an alternative low cost method of achieving rKA in an era of sophisticated technologies like computer aided navigation systems or robotics with accuracy.