Robotic Total Knee Replacement: Single-Centre, Prospective, Non-Randomised Comparative Study Comparing Restricted Kinematic Alignment Combined with a Load Sensor Versus Functional Alignment

<b>Background</b>: Total knee arthroplasty (TKA) is an effective procedure for symptomatic end-stage knee arthritis with good clinical and survivorship outcomes. However, up to 20% of patients report dissatisfaction following TKA. Recent studies have suggested that this may be at least partially due to suboptimal limb alignment or ligament imbalance. This study compared clinical outcomes at 1 year post-operatively (i.e., the 2011 Knee Society Score [KSS] and Forgotten Joint Score [FJS]) between two robotic-assisted personalised TKA techniques: functional alignment (FA) and an original technique combining restricted kinematic alignment (rKA) with a load sensor to achieve reliable ligament balancing (via bone re-cutting with a robotic arm). <b>Methods</b>: This single-centre, prospective, comparative study was performed at a robotic-assisted arthroplasty centre. The study population consisted of an FA group (43 patients) and rKA/sensor group (47 patients). Clinical outcomes were measured at 1 month post-operatively (visual analogue scale [VAS] pain score, flexion, range of motion [ROM], use of a mobility aid and stiffness) and at 1 year (2011 KSS, FJS, VAS, flexion and ROM). <b>Results</b>: There were no statistical significant differences in 2011 KSS or FJS at 1 year post-operatively between the two groups. Multivariate analysis showed no independent association of either technique with the 1-year follow-up KSS Objective Knee Indicators score (adjusted beta coefficient (aβ) = -2.371 [-7.380; 2.638], <i>p</i> = 0.357), KSS Patient Satisfaction score (aβ = -2.522 [-6.887; 1.842], <i>p</i> = 0.262), KSS Patient Expectations score (aβ = 0.629 [-0.928; 2.186], <i>p</i> = 0.431), KSS Functional Activities score (aβ = -3.399 [-10.881; 4.082], <i>p</i> = 0.377) or 1-year follow-up FJS (aβ = -5.168 [-19.887; 9.550], <i>p</i> = 0.494). <b>Conclusions:</b> There were no significant differences between the FA and rKA/load sensor groups in the 2011 KSS or FJS at 1 year post-operatively. To our knowledge, this is the first study to compare clinical outcomes between robotic-assisted FA TKA and rKA TKA. Clinical outcomes in the rKA/sensor group were similar to previous studies using rKA without robotic assistance or a load sensor. This was also the first report of the clinical outcomes of FA. The results need to be validated by larger scale studies to avoid potential type 2 errors.