Abstract
Introduction
Active robotics for total knee Arthroplasty (TKA) uses a CAD-CAM approach to plan the correct size and placement of implants and to surgically achieve planned limb alignment. The TSolution One Total Knee Application (THINK Surgical Inc., Fremont, CA) is an open-implant platform, CT-based active robotic surgical system. A multi-center, prospective, non-randomized clinical trial was performed to evaluate the safety and effectiveness of robotic-assisted TKA using the TSolution One Total Knee Application. This report details the findings from the IDE.
Methods
Inclusion criteria for patients receiving robotic TKA were: primary unilateral TKA; Kellgren-Lawrence OA grade 3 or 4; BMI < 40 kg/m2; coronal plane deformity < 20° varus; sagittal flexion contracture < 15°. In addition to monitoring all adverse events (AE), a pre-defined list of relevant major AEs were specifically identified to evaluate safety (Healy et al, 2013): medial collateral ligament injury; extensor mechanism disruption; neural deficit; periprosthetic fracture; patellofemoral dislocation; tibiofemoral dislocation; and vascular injury. Bleeding complications were also assessed. Malalignment rate, defined as the percentage of patients with more than a ± 3° difference in varus-valgus alignment from the preoperative plan, was used to determine accuracy of the active robotic system. Knee Society Scores (KSS) and Short Form 12 (SF-12) Health Surveys were assessed as clinical outcome measures. For each outcome, results were compared to published values associated with manual TKA.
Results
A total of 115 patients were enrolled at 6 US centers and followed for a maximum of 12 months after surgery. Mean surgical time (incision to close) improved consistently as the technique evolved (first 10 cases = 131.5 min, first 20 cases = 122.4 min), with mean robot time = 45.8 min. The incidence of pre-defined AEs identified was 0%, serving as a measure of safety of the procedure. Outside of the pre-defined list, only one AE was definitely associated with the use of the device; a metal pin was left inside the knee joint but no reoperation was performed. No patients required a blood transfusion. Alignment outside of the ± 3° goal was 11.2% with a difference of 0.5° ± 1.9° (mean ± STD), which represents a 45% statistically significant (posterior probability > 0.95) reduction in malalignment compared to the literature (Mason et al, 2007). Mean KSS Functional scores improved from 40.5 at baseline to 65.3 at 3 months, mean KSS Objective scores improved from 36.8 to 81.0, mean KSS Patient Satisfaction scores improved from 14.4 to 30.6, and mean SF-12 Physical Component scores improved from 32.9 to 43.5.
Discussion
The TSolution One Total Knee Application is descended from an active robotic system used in >8000 cases outside the United States since 2002. This trial represents the first US based study of this technology for primary TKA. The clinical study demonstrated positive safety outcomes as none of the seven pre-defined AEs were observed and there were no cases requiring transfusion. A positive effectiveness outcome was also demonstrated as the malalignment rate found in this study showed a substantial reduction from the 32% malalignment rate published in the literature for conventional instruments. KSS and SF-12 scores were comparable to other published TKA series.
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