Robotic-arm total knee arthroplasty (RTKA) was developed to potentially improve accuracy of bone cuts, component alignment, soft tissue balance, and patient outcomes. There is a paucity of data demonstrating that RTKA is superior to conventional total knee arthroplasty (CTKA) in terms of any of these metrics. This prospective comparative multicenter study was designed with these purposes in mind.
Patients were enrolled between June 1st, 2016 and March 31st, 2018 in a prospective, non-randomized, open-label, multicenter, consecutive comparative cohort study comparing RTKA and CTKA. Only patients who satisfied the following inclusion criteria were included: body mass index (BMI) ≤ 40kg/m2, primary unilateral TKA procedure, at least 18 years of age, and no joint infection. The following data were collected for analysis:
Preoperative data on component size prediction from CT scans
Intraoperative data on bone resection levels and joint line maintenance
Functional activity scores, patient-reported symptoms, satisfaction and expectation scores using The New Knee Society Scoring System
Radiographic results, specifically coronal alignment
For femoral components implanted, 82% were the exact size as predicted by the robotic-software and the remaining 18% were within 1 size (100% within 1 size). For tibial implants, 69% were the exact size of what the robotic-software predicted and 29% were within 1 size (98% within 1 size).
RTKAs had significantly less distal lateral femoral resection (5.55 vs. 7.11 mm), distal medial femoral resection (6.89 vs. 7.97 mm), lateral tibial resection (7.76 vs. 8.54 mm), and medial tibial resection (4.11 vs. 5.56 mm, p<0.05) compared to CTKA. Joint line restoration was comparable between RTKA and CTKA, but required less tibial bone removal when using robotic techniques.
Pre-operatively, all demographic, functional, symptom, satisfaction, and expectation measures were similar between treatment groups (all p<0.05, Tables 1–5). Those who underwent RTKA had significantly higher mean functional activity walking and standing score improvements from baseline to 4–6 weeks (1.4 vs. −1.2 points; p=0.019) and to 6 months (9.6 vs. 6.9 points; p=0.017) after surgery compared to CTKA. The mean overall functional activity score improvement from baseline to 1-year post-surgery was also higher for RTKA compared to CTKA (36.8 vs. 15.0 points; p=0.020). For all other parameters (standard activities, advanced activities, pain with walking, pain with stairs, satisfaction and expectation scores), score changes from baseline were not significantly different between groups, though many trended slightly higher for RTKA.
Radiographic evaluation of RTKA demonstrated that varus deformity was corrected to neutral in 96% of cases and valgus deformity was corrected in 100%.
To the best of our knowledge, this is the first study to prospectively evaluate outcomes of RTKA patients compared to CTKA. A number of positive early effects were seen with RTKA. This patient cohort will continue to be followed, and these findings may translate into longer-term patient reported outcomes improvement, longer component survivorship and cost savings.
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