Introduction

Robotic assisted surgery was introduced in total knee arthroplasty (TKA) to improve accuracy of implant positioning with the aim for optimizing clinical outcome. However, the targeted implant position or alignment is debated. Mechanical alignment (MA) is generally seen as the gold-standard, yet patient specific alignment strategies were introduced. Aim of this study was twofold, first to compare clinical outcome of conventional TKA vs. robotically assisted TKA in a mechanical aligned TKA series. Second, to analyze the clinical effect of introducing patient specific alignment (‘inverse kinematic alignment’, iKA) in a robotic assisted TKA cohort.

Materials And Methods

120 patients with end stage osteoarthritis of the knee were enrolled in this study. The first group (n=40) received conventional, mechanical aligned (MA) TKA. The second group (n=40) robotic assisted, mechanical aligned (MA) TKA. The third group (n=40) robotic assisted, inverse kinematic aligned (iKA) TKA. All patients received Triathlon CR TKA with a uniform surgery protocol. The robotic platform used was Mako. The three groups matched for age, gender, BMI and preoperative alignment. Preoperative and 1 year postoperative clinical outcome was documented with Oxford Knee Scores (OKS).

Results

When comparing OKS between the 2 mechanical aligned groups, no significant difference (p=0.066) was calculated between conventional TKA (group 1; 40.3 ± 6.0) and robotically assisted TKA (group 2; 42.2 ± 6.3) at 1 year postop. When comparing OKS between the 2 robotically assisted groups, no significant difference (p=0.069) was calculated between mechanical aligned TKA (group 2; 42.2 ± 6.3) and inverse kinematic aligned TKA (group 3; 44.6 ± 3.5). When comparing conventional mechanical aligned TKA (group 1; 40.3 ± 6.0) with robotically assisted, inverse kinematic aligned TKA (group 3; 44.6 ± 3.5), a significant difference is demonstrated (p<0.01).

Discussion

The results of this study suggest that the introduction of both patient specific alignment and robotically assisted surgery enhance clinical outcome in TKA surgery. Secondly, the real added value of robotic assisted surgery is performing patient specific alignment. Moreover, patient specific alignment should be the goal.