'Skywalker' surgical robot for total knee arthroplasty: An experimental sawbone study

Femoral resection accuracy and precision in manual caliper-verified kinematic alignment total knee arthroplasty

Introduction

The accuracy and precision of bone resections in total knee arthroplasty (TKA) are essential to avoid poor implant positioning, which can lead to component wear, pain, and instability, reducing patient satisfaction and implant survivorship. Technology-assisted TKA techniques aim to improve accuracy but come with added costs, increased operative time, and varying success in clinical outcomes. Caliper-verified kinematic alignment (KA) attempts to restore the joint line by precisely measuring resections to equal implant thickness. We evaluated the accuracy and precision of caliper-verified KA-TKA performed with manual instruments. We hypothesised that this technique would achieve high accuracy and precision, with an average absolute difference between actual and target distal and posterior femoral resection measurements of ≤ 0.5 mm.

Methods

385 consecutive patients underwent primary unrestricted caliper-verified KA-TKA with manual instrumentation. The thickness of the distal medial (DM), distal lateral (DL), posterior medial (PM) and posterior lateral (PL) femoral condyle resections were measured with a caliper and compared to a target determined by the degree of cartilage loss, saw blade kerf, and femoral component thickness.

Results

The mean differences between the resected and target thicknesses for DM, DL, PM and PL femoral resections were 0.1 ± 0.2 mm, 0.1 ± 0.3 mm, 0.3 ± 0.5 mm and 0.2 ± 0.4 mm, respectively (mean ± std. dev.). Most femoral resections were within 0.5 mm of the target-97.7%, 94.5%, 85.7% and 89.4% of DM, DL, PM and PL resections, respectively.

Conclusion

Manual caliper-verified KA-TKA achieved highly accurate and precise femoral resections with absolute differences from target that averaged 0.175 mm. This simple, logical, efficient, and reproducible surgical technique may be an option for surgeons contemplating the use of technology-assisted options, such as patient-specific instrumentation or robotic arm-assisted TKA, and surgeons without access to such technologies.

Level of Evidence

Level II.

Robot-Based Minimally Invasive Spherical Osteotomy System Improves the Accuracy and Reproducibility of the Resulting Surface

BACKGROUND

A minimally invasive spherical osteotomy assistant system (MISOS) based on a multi-axis surgical robot was designed to improve the control and precision of manual spherical osteotomy.

METHODS

Based on human sawbone models, the feasibility of MISOS was verified by comparing the osteotomy centre deviation and the section curvature of the acetabulum, femur, and tibia.

RESULTS

Compared with freehand spherical osteotomy, the MISOS system demonstrated superior centre deviation for the acetabulum (1.48 ± 0.93 vs. 11.15 ± 3.97 mm), femur (3.12 ± 0.75 vs. 8.81 ± 3.04 mm), and tibia (1.91 ± 0.84 vs. 7.33 ± 1.53 mm) as well as superior curvature deviation for the acetabulum (1.40 ± 0.08 vs. 3.16 ± 0.56 mm), femur (0.26 ± 0.07 vs. 0.491 ± 0.21 mm), and tibia (0.21 ± 0.02 vs. 0.46 ± 0.18 mm). These results indicate that MISOS can assist surgeons in performing accurate and stable spherical osteotomy.

CONCLUSION

The MISOS system demonstrates promise as a precise assistive tool for minimally invasive orthopaedic spherical osteotomy, with potential for broader clinical applications.

Using a patient-specific cutting guide enables identical knee osteotomies: An evaluation of accuracy on sawbones

PURPOSE

It was hypothesized that using a Patient-Specific Cutting Guide (PSCG) would allow the creation of sawbones model osteotomies, identical in the 3 planes and the hinge parameters, that can be used for biomechanical studies. The aim of the study was to evaluate the accuracy of the PSCG system and to introduce and assess the new hinge parameter; the hinge area.

METHODS

Six identical sawbones tibia models were identically set up for identical osteotomy cuts by the same surgeon in the same session and with identical instruments. A medical scanner was used to evaluate the 3D configuration of all the specimens. The analyzed parameters included the cutting angles in both the coronal and sagittal planes (degrees) and the hinge and the slicing areas (cm2), and the hinge thickness (mm). The values were statistically evaluated for average, standard deviation, 95% confidence index, and delta to the expected values were calculated.

RESULTS

The mean values for the coronal and sagittal angles were 110.5̊±1̊ and 89.8̊±0.8̊, respectively. The 95% confidence index level ranged between 0.1̊, and 0.8̊ in both the coronal & the sagittal planes. The mean values for the hinge thickness, the hinge area, and the slicing area were 12.7±1.5mm, 4.2±0.9 cm2, and 18.3±1.2 cm2, respectively.

CONCLUSION

In the presented study, it can be demonstrated that mechanically identical osteotomy specimens, with regard to the cutting planes and hinge parameters, can be reliably created using the PSCG. The identical specimens can be used for biomechanical research purposes to further expand our knowledge of the factors affecting osteotomy outcomes.

LEVEL OF EVIDENCE

IV.

Evaluating the accuracy of a new robotically assisted system in cadaveric total knee arthroplasty procedures

BACKGROUND

Robot-assisted total knee arthroplasty (TKA) has been shown to facilitate high-precision bone resection, which is an important goal in TKA. The aim of this cadaveric study was to analyze the accuracy of the target angle and bone resection thickness of a recently introduced robotic TKA system.

METHODS

This study used 4 frozen cadaveric specimens (8 knees), 2 different implant designs, navigation, and a robotic system. The 4 surgeons who participated in this study were trained and familiar with the basic principles and operating procedures of this system. The angle of the bone cuts performed using the robotic system was compared with the target angles from the intraoperative plan. For each bone cut, the resection thickness was recorded and compared with the planned resection thickness.

RESULTS

The mean angular difference for all specimens was less than 1°, and the standard deviation was less than 2°. The mean difference between the planned and measured angles was close to 0 and not significantly different from 0 except for the difference in the frontal tibial component angle, which was 0.88°. The mean difference in the hip-knee-ankle axis angle was - 0.21°± 1.06°. The mean bone resection difference for all specimens was less than 1 mm, and the standard deviation was less than 0.5 mm.

CONCLUSIONS

The results of the cadaveric experimental study showed that the new TKA system can realize highly accurate bone cuts and achieve planned angles and resection thicknesses. Despite the limitations of small sample sizes and large differences between cadaveric and clinical patients, the accuracy of cadaveric experiments provides strong support for subsequent clinical trials.

Can Robotic Arm-assisted Total Knee Arthroplasty Remain Cost-effective in Volume-based Procurement System in China? A Markov Model-based Study

OBJECTIVE

The volume based procurement (VBP) program in China was initiated in 2022. The cost-effectiveness of robotic arm assisted total knee arthroplasty is yet uncertain after the initiation of the program. The objective of the study was to investigate the cost-effectiveness of robotic arm-assisted total knee arthroplasty and the influence of the VBP program to its cost-effectiveness in China.

METHODS

The study was a Markov model-based cost-effectiveness study. Cases of primary total knee arthroplasty from January 2019 to December 2021 were included retrospectively. A Markov model was developed to simulate patients with advanced knee osteoarthritis. Manual and robotic arm-assisted total knee arthroplasties were compared for cost-effectiveness before and after the engagement of the VBP program in China. Probability and sensitivity analysis were conducted.

RESULTS

Robotic arm-assisted total knee arthroplasty showed better recovery and lower revision rates before and after initiation of the VBP program. Robotic arm-based TKA was superior to manual total knee arthroplasty, with an increased effectiveness of 0.26 (16.87 vs 16.61) before and 0.52 (16.96 vs 16.43) after the application of Volume-based procurement, respectively. The procedure is more cost-effective in the new procurement system (17.13 vs 16.89). Costs of manual or robotic arm-assisted TKA were the most sensitive parameters in our model.

CONCLUSION

Based on previous and current medical charging systems in China, robotic arm-assisted total knee arthroplasty is a more cost-effective procedure compared to traditional manual total knee arthroplasty. As the volume-based procurement VBP program shows, the procedure can be more cost-effective.

Semiactive robotic-arm system versus patient-specific instrumentation in primary total knee arthroplasty: Efficacy and accuracy

OBJECTIVE

To compare the difference in efficacy and accuracy during total knee arthroplasty (TKA) among robotic-arm system, patient-specific instrumentation (PSI) and conventional TKA (COTKA).

METHODS

Retrospective analysis of 90 advanced knee osteoarthritis (OA) patients in our hospital between June 2019 and December 2020 was conducted. Patients were divided into robotic arm-assisted (RA)TKA (group A), PSITKA (group B) and COTKA (group C), 30 cases in each group. The operation time, intraoperative bleeding, and length of hospital stay were counted. Imaging data of hip-knee-ankle angle (HKA), posterior condylar angle (PCA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and sagittal tibial component angle (sTCA) were statistically analyzed. The postoperative recovery of the patients was evaluated by Knee Society Score (KSS) and the Western Ontario Mac Master University Index Score (WOMAC).

RESULTS

Group A had the least intraoperative bleeding. For operation time, group A was the longest compared with group B and group C (P < 0.05), while group B was longer than group C (P < 0.05). There was no significant difference in HKA, LDFA, and MPTA among the three groups, and the lower limb alignments were all restored to the neutral position. PCA of group A and B were both smaller than that of group C and closer to 0° (P < 0.05), but the difference between group A and B was not statistically significant. The sTCA in group A was significantly better than group B, and group B was significantly better than group C (P < 0.05). There were no significant differences in function scores among the three groups.

CONCLUSION

Compared to the PSI and CO, RA is more minimally invasive and more accurate in radiographic results.