Preliminary experience with an image-free handheld robot for total knee arthroplasty: 77 cases compared with a matched control group

BackgroundAchieving an optimal limb alignment is an important factor affecting the long-term survival of total knee arthroplasty (TKA). This is the first study to look at the limb alignment and orientation of components in TKA using a novel image-free handheld robotic sculpting system.MethodsThis case-controlled study retrospectively compared limb and component alignment of 77 TKAs performed with a robot (Robot-group) with a matched control group of patients who received conventional alignment with intramedular rods (Control group). Alignment and component positioning was measured on full-leg weight-bearing and standard lateral X-rays by two independent observers. The image-free handheld robotic sculpting system calculated the planned and achieved mechanical axis (MA). Outliers were defined as>3 degrees deviation from planned alignment.ResultsMean MA was 180.1 degrees (SD=1.9) in the Robot-group, compared to the Control group with a mean MA of 179.1 degrees (SD=3.1, p=0.028). We observed 5 outliers (6%) in the Robot-group and 14 outliers (18%, p=0.051) in the Control group. Fraction of outliers of the frontal tibial component was 0% in the Robot-group versus 8% in the Control group (p=0.038). There were no other statistical differences regarding the implant positioning between both groups.ConclusionThe Robot-group showed significantly less outliers compared to the conventional technique. Whether these differences are clinically relevant is questionable and should be investigated on the long term. Randomized controlled trials with larger patient series will be needed in the future to confirm our preliminary results.