Introduction. Mechanically aligned total knee arthroplasty(TKA) relies on restoring the hip-knee-ankle angle of the limb to neutral or as close to a straight line as possible. This principle is based on studies that suggest limb and knee alignment is related long term survival and wear. For that cause, there has been recent attention concerning computer-assisted TKA and robot is also one of the most helpful instruments for restoring neutral alignment as known. But many reported data have shown that 20% to 25% of patients with mechanically aligned TKA are dissatisfied. Accordingly, kinematically aligned TKA was implemented as an alternative alignment strategy with the goal of reducing prevalence of unexplained pain, stiffness, and instability and improving the rate of recovery, kinematics, and contact forces. So, we want to report our extremely early experience of robot-assisted TKA planned by kinematic method. Materials and Methods. This study evaluated the very short term results (6 weeks follow up) after robot-assisted TKA aligned kinematically. 50 knees in 36 patients, who could be followed up more than 6 weeks after surgery from December 2014 to January 2015, were evaluated prospectively. The diagnosis was primary osteoarthritis in all cases. The operation was performed with ROBODOC (ISS Inc., CA, USA) along with the ORTHODOC (ISS Inc., CA, USA) planning computer. The cutting plan was made by single radius femoral component concept, each femoral condyles shape-matched method along the transverse axis using multi-channel CT and MRI to place the implant along the patient's premorbid joint line. Radiographic measurements were made from long bone scanograms. Clinical outcomes and motion were measured preoperatively and 6 weeks postoperatively. Results. The range of motion increased from preoperative mean 113.4 (±5.4, 85 to 130) to postoperative mean 127.3 (±7.4, 90 to 140) at last follow up. The mean knee score and functional score improved from 35.4 (±10.3, 10 to 55) and 30.1 (±7.7, 10 to 60) before surgery to 88.6 (±5.8, 60 to 100) and 90.7 (±9.6, 60 to 100) at last follow up. The WOMAC score was improved from 52(±15.5) to 20(±14.8) at last follow up. The postoperative Hip-knee-ankle alignment was −1.3±2.8. The femoral component was 2.1 valgus and tibial component was 2.8 varus along the mechanical axis in coronal plane. There were no complications and failures. Conclusion. On the basis of our results, we are cautiously optimistic about robot-assisted TKA by kinematically alignment. More anatomic alignment of the implant can be associated with better flexion and better clinical outcomes scores in the kinematically aligned method in our thinking. But, at this starting point, more comparative studies with mechanical aligned group are needed and we must explore about implant survivalship issues and implant loading issues in dynamic and static condition that someone is worrying about. If the problem can be solved, there is no use worrying about it in our thinking. And what is more, the robot-assisted surgery will be very useful especially in those cases of severely deformed knees and distorted anatomy to be aligned kinematically

Introduction and Objective. Total knee arthroplasty (TKA) is a frequently and increasingly performed surgery in the treatment of disabling knee osteoarthritis. The rising number of procedures and related revisions pose an increasing economic burden on health care systems. In an attempt to lower the revision rate due to component malalignment and soft tissue imbalance in TKA, robotic assistance (RA) has been introduced in the operating theatre. The primary objective of this study is to provide the results of a theoretical, preliminary cost-effectiveness analysis of RA TKA. Materials and Methods. A Markov state-transition model was designed to model the health status of sixty-seven-year-old patients in need of TKA due to primary osteoarthritis over a twenty-year period following their knee joint replacement. Transitional probabilities and independent variables were extracted from existing literature. Patients’ state in the transition model was able to change on an annual basis. The main differences between the conventional and RA TKA were the outlier rate in the coronal plane and the cost of the procedure. In RA TKA, it was hypothesized that there were lower revision rates due to a lower outlier rate compared to conventional TKA. Results. The value attributed to the utility both for primary and revision surgery has the biggest impact on the ICER, followed by the rate of successful primary surgery and the cost of RA-technology. Only 2.18–2.34% of the samples yielded from the probabilistic sensitivity analysis proved to be cost-effective (threshold set at $50000/QALY). A calculated surgical volume of at least 191–253 cases per robot per year is needed to prove cost-effective taking the predetermined parameter values into account. Conclusions. Robot-assisted TKA might be a cost-effective procedure compared to conventional TKA if a minimum of 191 cases are performed on a yearly basis, depending on the cost of the robot. The cost-benefit of the robotic TKA surgery is mainly based on a decreased revision rate. This study is based on the assumption that alignment is a predictor of success in total knee arthroplasty. Until there is data confirming the assertion that alignment predicts success robot-assisted surgery cannot be recommended

Among many factors that influence the outcomes of Total Knee Arthroplasties (TKAs), the mechanical alignment has played major roles for the success of TKA, the survival rates of the implants, and patient functionality. Most, but not all, studies have shown that alignment of the mechanical axis in the coronal plane within a range of 3° varus/valgus is associated with improved long-term function and increased survival rates. Robot-assisted TKA has been developed to improve improves the accuracy and precision of component implantation and mechanical axis (MA) alignment. We hypothesised that robot-assisted TKA would lead to a more accurate leg alignment and component implantation, and thus, improve radiological and clinical outcomes. Between January 2003 and December 2004, a total of 98 primary TKA procedures were compared: 49 using a robotic-assisted procedure and 49 using conventional manual techniques. The cohorts were followed for 121.2 and 119.5 months on average, respectively. Radiographic assessments of the patients were performed preoperatively and at final follow-up and made according to the Knee Society Roentgenographic Evaluation System (KSRES) which included measurements of the coronal mechanical axis and sagittal and coronal inclinations of femoral and tibial components. The radiographic measurements were made using a PACS (Picture Archiving and Communication System). Clinical assessments were performed preoperatively, and at a final follow-up date that was a minimum of postoperative nine years. The clinical results included ranges of motion (ROM), Hospital for Special Surgery (HSS) scores, Western Ontario and McMaster University (WOMAC) scores (for pain and function). The radiographic results showed no statistical differences when comparing the means of the two groups. When considering outliers (defined as error ≥ ±3°) for the mechanical axis, femoral coronal and sagittal inclinations, and tibial coronal and sagittal inclinations, the ROBODOC group had zero outliers for all measurements except for one in tibial sagittal inclination. On the other hand, the conventional group had 12 outliers for mechanical axis, 2 for femoral coronal inclination, 3 for femoral sagittal inclination, 3 for tibial coronal inclination, and 4 for tibial sagittal inclination. However, there were no statistically significant differences between groups for ROM, HSS, or WOMAC scores at the final follow-up. The results of this study support previous work and demonstrate that the ROBODOC-assisted implantation of TKA results in better radiographic outcomes and better ligament balance with equivalent safety when compared to conventional TKA at a minimum follow-up of nine years

An intelligent bone cutting tool as well as a navigation system is of high potential to provide great assistance for the surgeons in computer assisted orthopedic surgery. In this paper we designed a coordinated controller for the surgical robot to perform bone cutting more safely, easily and fast compared with being performed by manual bone saw. Coordinated control is in an outer control loop and determines suitable parameters of the inner control loop of the robot. The inner control loop is an admittance controller for the master site and a compliance controller for the slave site. Coordinated control consists of three modes, i.e. automated cutting, cautious cutting and automated prevention depending on bone cutting conditions and human intention. In automated cutting mode, the coordinated control will set larger admittance gain and smaller compliance gain to provide an assistant force to the human for completion of bone cutting. In cautious cutting mode, smaller admittance gain and larger compliance gain will be set and a resistant force will be provided to the operator for micro progress of bone cutting. In emergence mode, the robot will stop the cutter going forward.

Experimental result shows that in automated mode of the proposed coordinated control was able to assist bone cutting at the same time to avoid undesired large cutting force and cutter breakage. The moving speed of cutter slowed down as the cutting forces increased due to the cutter hitting harder bone, thus alleviated sawblade bouncing up and achieved less deviation from designed cutting plane. In cautious cutting mode the cutting forces were magnified to be felt by the operator. The operator was able to perform micro progress of bone cutting with intensive monitoring of the cutting forces. This functionality is especially useful as the cutter approaches the critical area where the surgeon regards as dangerous region. The emergent mode was also successfully triggered by calculating the defined apparent admittance. The apparent admittance is more reliable than using the cutting force only in detection of cutting boundary.

A hand's on robot under coordinated control is demonstrated in conjunction with surgical navigation system in computer assisted orthopedic surgery. This paper experimentally showed that the coordinated control can effective provide assistive and resistant forces to achieve safe and accurate bone cutting in total knee arthroplasty.

Background/Introduction

As a new generation of robotic systems is introduced into the world of arthroplasty, Robotic-Assisted Total Knee Arthroplasty (TKA) represents a growing proportion of a reconstructive surgeon's operative volume. This study aims to compare the post-operative readmission rate, pain scores, costs, as well as the effects on surgeon efficiency one year after adoption of these technologies into clinical practice.

Aims

The aims of this study were: 1) to describe extended restricted kinematic alignment (E-rKA), a novel alignment strategy during robotic-assisted total knee arthroplasty (RA-TKA); 2) to compare residual medial compartment tightness following virtual surgical planning during RA-TKA using mechanical alignment (MA) and E-rKA, in the same set of osteoarthritic varus knees; 3) to assess the requirement of soft-tissue releases during RA-TKA using E-rKA; and 4) to compare the accuracy of surgical plan execution between knees managed with adjustments in component positioning alone, and those which require additional soft-tissue releases.

A functional total knee replacement has to be well aligned, which implies that it should lie along the mechanical axis and in the correct axial and rotational planes. Incorrect alignment will lead to abnormal wear, early mechanical loosening, and patellofemoral problems. There has been increased interest of late in total knee arthroplasty with robot assistance. This study was conducted to determine if robot-assisted total knee arthroplasty is superior to the conventional surgical method with regard to the precision of implant positioning. Twenty knee replacements of ten robot-assisted and another ten conventional operations were performed on ten cadavers. Two experienced surgeons performed the surgery. Both procedures were undertaken by one surgeon on each cadaver. The choice of which was to be done first was randomized. After the implantation of the prosthesis, the mechanical-axis deviation, femoral coronal angle, tibial coronal angle, femoral sagittal angle, tibial sagittal angle, and femoral rotational alignment were measured via three-dimensional CT scanning. These variants were then compared with the preoperative planned values. In the robot-assisted surgery, the mechanical-axis deviation ranged from −1.94 to 2.13° (mean: −0.21°), the femoral coronal angle ranged from 88.08 to 90.99° (mean: 89.81°), the tibial coronal angle ranged from 89.01 to 92.36° (mean: 90.42°), the tibial sagittal angle ranged from 81.72 to 86.24° (mean: 83.20°), and the femoral rotational alignment ranged from 0.02 to 1.15° (mean: 0.52°) in relation to the transepicondylar axis. In the conventional surgery, the mechanical-axis deviation ranged from −3.19 to 3.84°(mean: −0.48°), the femoral coronal angle ranged from 88.36 to 92.29° (mean: 90.50°), the tibial coronal angle ranged from 88.15 to 91.51° (mean: 89.83°), the tibial sagittal angle ranged from 80.06 to 87.34° (mean: 84.50°), and the femoral rotational alignment ranged from 0.32 to 4.13° (mean: 2.76°) in relation to the transepicondylar axis. In the conventional surgery, there were two cases of outlier outside the range of 3° varus or valgus of the mechanical-axis deviation. The robot-assisted surgery showed significantly superior femoral-rotational-alignment results compared with the conventional surgery (p=0.006). There was no statistically significant difference between robot-assisted and conventional total knee arthroplasty in the other variants. All the variants were measured with high intraobserver and interobserver reliability. In conclusion, Robot-assisted total knee arthroplasty showed excellent precision in the sagittal and coronal planes of the three-dimensional CT. Especially, better accuracy in femoral rotational alignment was shown in the robot-assisted surgery than in the conventional surgery despite the fact that the surgeons who performed the operation were more experienced and familiar with the conventional surgery than with robot-assisted surgery. It can thus be concluded that robot-assisted total knee arthroplasty is superior to the conventional total knee arthroplasty

Introduction. Robot-assisted total knee arthroplasty (RA-TKA) is theoretically more accurate for component positioning than TKA performed with mechanical instruments (M-TKA). Furthermore, the ability to quantify soft tissue laxity and adjust the plan prior to bone resection should reduce variability in polyethylene thickness. This study was performed to compare accuracy to plan for component positioning and polyethylene thickness in RA-TKA versus M-TKA. Methods. 199 consecutive primary TKAs (96 C-TKA and 103 RA-TKA) performed by a single surgeon were reviewed. Full-length standing and knee radiographs were obtained pre and post-operatively. For M-TKA, measured resection technique was used. Planned coronal plane femoral and tibial component alignment, and overall limb alignment were all 0° to the mechanical axis; tibial posterior slope was 2°; and polyethylene thickness was 9mm. For RA-TKA, individual component position was adjusted to assist balance the gaps but planned coronal plane alignment for the femoral and tibial components and overall limb alignment had to remain 0+/− 3°; planned tibial posterior slope was 1.5°. Planned values and polyethylene thickness for RA-TKA were obtained from the final intra-operative plan. Mean deviations from plan for each parameter were compared between groups (ΔFemur, ΔTibia, ΔPS, and polyethylene thickness) as were distal femoral recut and tourniquet time. Results. In RA-MKA versus M-TKA: the ΔFemur (0.9 ° v. 1.7 °), ΔTibia (0.3 ° v. 1.3 °), and ΔPS (−0.3 ° v. 1.7 °) all deviated significantly less from plan (all p<0.0001); significantly fewer knees required distal femoral recut (10% vs. 23%, p=0.033); and deviation from planned polyethylene thickness was significantly less (1.4mm vs 2.7mm, p<0.0001. However, tourniquet time was longer (99 minutes v. 89 minutes, p<0.0001). Conclusion. RA-TKA is both significantly more accurate to plan for component positioning and final polyethylene thickness. The greater accuracy and reproducibility of RA-TKA may be important as precise new goals for component positioning are developed

Introduction. The success of total knee arthroplasty depends on many factors, including the preoperative condition of the patient, the design and materials of the components and surgical techniques. It is important to position the femoral and tibial components accurately and to balance the soft tissues. Malpositioning of the component can lead to failures due to aseptic loosening, instability, polyethylene wear and dislocation of the patella. In order to improve post-operative alignment, computer-aid systems have been developed for total knee arthroplasty. Many clinical and experimental studies of these systems have shown that the accuracy of implanted components can be improved in spite of the increase in costs and operating time. This may not, however, improve the outcome in the short-term. Restoration of the normal mechanical axis of the knee and balancing of the surrounding soft tissues have been shown to have an important bearing on the final outcome of knee replacement operations. In severely deformed knees, whether varus or valgus, these goals may be difficult to achieve. We compared the radiologic results of the mechanical axis and implant position of Total Knee Arthroplasty using a robot-assisted method with conventional manually implanted method in severe varus deformed knee. Materials and Methods. A data set of 50 consecutive cases that were performed from April 2007 to December 2010 using the robot assisted TKA(Group A) were compared with a data set of 50 consecutive cases from the same period that were done using conventional manual TKA(Group B). All cases had a preoperative mechanical varus deformity >15° and one brand of implant was used on all cases. The diagnosis was primary osteoarthritis in all knees. The operations were performed by one-senior author with the same robot system, ROBODOC (ISS Inc., CA, USA) along with the ORTHODOC (ISS Inc., CA, USA) planning computer. (See Figure 1.) The radiological evaluations included mechanical axis, implant position (α,β,γ,δ angle) according to the system of American Knee Society. Results. There was a significant difference in the postoperative α, β, γ angle and mechanical axis between two group(p<0.05). In group A, mechanical axis angle changed from preoperative varus 18.5±3.3° to postoperative varus 0.6±1.5° without outlier. In group B, mechanical axis angle changed from varus 19.4±4.2° to varus 2.5±3.8° with 8 outliers. In group A, the mean α, β, γ, δ angle were 96.7°, 90.1°, 1.9°, 86.8° and 93.1°, 88.3°, 3.8°, 85.9° in group B. But we found no loosening and osteolysis at last follow up in both group. Conclusion. On the basis of our results, patients with severe varus knee(>15°) tended to have more postoperative varus mechanical alignment in conventional manual TKA group than robot-assisted TKA group. We think that robot-assisted TKA is helpful in excessive varus knee in aspect of not only mechanical alignment and implant position but also long term clinical results and implant longevity. However, a long term followup evaluation will be necessary and complications in robot system

Only limited data exists concerning outcomes after total knee arthroplasty (TKA) using a surgical robot. We conducted this study to evaluate the clinical and radiographical results in robotic-assisted implantation of TKAs with a minimum follow-up of two years. A total of 50 primary TKAs using ROBODOC were included in this study. The mean duration of follow-up was 28.3 months. The radiographic measurement with regard to the change of mechanical axis, and the inclination of the femoral and tibial components were assessed. The value within ± 3° of optimum was classified to be “acceptable”, and the value exceeding more than ± 3° to be “outlier” results. Also we evaluated clinical results with the range of motion (ROM), Hospital for Special Surgery (HSS) scores, and Western Ontario and McMaster University (WOMAC) scores. The mechanical axis was changed from 6.57 varus to 0.81 valgus. Mean coronal inclination of the femoral and tibial component were 88.61 and 89.76 at the last follow up. Also, mean sagittal inclination of the femoral and tibial component were 0.82 and 85.49. On the other hand, all prostheses had no radiolucent lines. On the clinical assessment, the range of motion improved from 124.9 to 128.4, and the improvement of HSS score and Womac score were 70.06 to 95.72 and 65.64 to 28.92 in each. No major adverse events related to the use of the robotic system have been observed. However, one case of the formation of seroma around the pin track and two cases of the partial abrasion of patellar tendon occurred in relation to procedures. A surgical robot system in TKAs provides good clinical and radiographical results at least 2 years follow-up, however further study for the long term follow-up may be needed. A clear advantage of robot-assisted TKA seems to be ability to execute a highly precise preoperative planning and intraoperaive procedures. But current disadvantages such as increased operating times and inability of adjusting the preoperative planning during the procedure have to be resolved in the future

Aims

It is unknown whether gap laxities measured in robotic arm-assisted total knee arthroplasty (TKA) correlate to load sensor measurements. The aim of this study was to determine whether symmetry of the maximum medial and lateral gaps in extension and flexion was predictive of knee balance in extension and flexion respectively using different maximum thresholds of intercompartmental load difference (ICLD) to define balance.