Improved accuracy of implant placement with an imageless handheld robotic system compared to conventional instrumentation in patients undergoing total knee arthroplasty: a prospective randomized controlled trial using CT-based assessment of radiological outcomes

PURPOSE

Image-free handheld robotic-assisted total knee arthroplasty (RATKA) has shown to achieve desired limb alignment compared to conventional jig-based instrumented total knee arthroplasty (CTKA). The aim of this prospective randomized controlled trial (RCT) was to evaluate the accuracy of a semi-autonomous imageless handheld RATKA compared to CTKA in order to achieve the perioperative planned target alignment of the knee postoperatively.

METHODS

Fifty-two patients with knee osteoarthritis were randomized in 1:1 ratio to undergo unilateral CTKA or an imageless handheld RATKA. A full-length lower limb CT-scan was obtained pre- and 6-week postoperative. The primary outcomes were radiologic measurements of achieved target hip-knee-ankle axis (HKA-axis) and implant component position including varus and external rotation and flexion of the femur component, and posterior tibial slope. The proportion of outliers in above radiographic outcomes, defined as > 3° deviation in postoperative CT measurements as compared to perioperative planned target, were also noted. Knee phenotypes were compared with use of the Coronal Plane Alignment of the Knee (CPAK) classification.

RESULTS

Baseline conditions were comparable between both groups. The overall proportion and percentage of outliers (n = 38, 24.4% vs n = 9, 5.8%) was statistically significant (p < 0.001) in favor of RATKA. The achieved varus-valgus of the femoral component (varus 1.3° ± 1.7° vs valgus - 0.1° ± 1.9°, p < 0.05) with statistically significant less outliers (0% vs 88.5%, p < 0.01), the achieved HKA-axis (varus 0.4° ± 2.1° vs valgus - 1.2° ± 2.1°, p < 0.05) and the posterior tibial slope (1.4° ± 1.1° vs 3.2° ± 1.8°, p < 0.05) were more accurate with RATKA. The most common postoperative CPAK categories were type II (50% CTKA vs 61.5% RATKA), type I (3.8% CTKA vs 23.1% RATKA) and type V (26.9% CTKA vs 15.4% RATKA). CPAK classification III was only found in CTKA (19.2%). Type VI, VII, VIII, and IX were rare in both populations.

CONCLUSIONS

The present trial demonstrates that an imageless handheld RATKA system can be used to accurately perioperatively plan the desired individual component implant positions with less alignment outliers whilst aiming for a constitutional alignment.

LEVEL OF EVIDENCE

I.

Learning curve for imageless robotic-assisted total knee arthroplasty in non-fellowship trained joint replacement surgeons

Introduction

Robotic-assisted total knee arthroplasty (RA-TKA) has become increasingly popular, although an associated learning curve can be a deterrent for some surgeons. Prior studies have addressed this learning curve in fellowship-trained arthroplasty surgeons, however the learning curve among non-fellowship-trained surgeons remains unclear. The objective of this study was to investigate the learning curve for imageless RA-TKA related to operative time and rates of complications among two non-arthroplasty-trained orthopedic surgeons.

Methods

This retrospective case series included 200 RA-TKA consecutive cases performed by two non-arthroplasty-trained orthopedic surgeons (100 each). Cases were divided into 2 cohorts for each surgeon: the first 50 consecutive cases and the second 50 cases. These cohorts were then compared to assess for trends in each surgeon as well as in both surgeons combined. Mean operative times were compared, as were hospital length of stay, complications, readmission, and reoperations.

Results

For both surgeons, the mean operative time significantly decreased from the first 50 cases to the next 50 cases (116.5 vs 108.4 min for surgeon 1, P = 0.031; 125.7 vs 109.1 min for surgeon 2, P = 0.001). No significant differences were found among length of stay, complications, readmissions, or reoperations between cohorts.

Conclusion

General orthopedic surgeons can expect to optimize operative time within 50 cases, while not carrying associated risks of related complications during the early learning period.

Achieving functional alignment in total knee arthroplasty: early experience using a second-generation imageless semi-autonomous handheld robotic sculpting system

PURPOSE

In order to minimize errors during achieving the targeted alignment of the total knee arthroplasty (TKA) components, robotic-assisted surgery has been introduced with the aim to help surgeons to improve implant survival, clinical outcomes, and patient satisfaction. The primary goal of this paper is to highlight surgical tips and tricks on how to achieve functional alignment (FA) through intra-operative boney mapping, numeric gap, and alignment data, using the next generation of imageless robotic surgical systems.

METHOD

This retrospective case-series contains planned and achieved data on the FA and joint gap data obtained from 526 patients captured and assessed with use of a semi-autonomous imageless handheld robotic sculpting systems. All patients were operated upon by two experienced TKA surgeons.

RESULTS

The mean difference between planned and achieved alignment was 1.46° (≥ 7° varus group), 1.02° (< 7° varus group), 1.16° (< 7° valgus group), and 1.43° (≥ 7° valgus group). The mean observed planned and achieved extension and flexion gaps were below 1.47 mm for medial extension gaps, 1.12 mm for the lateral extension gaps, 1.4 mm for the medial flexion gaps, and 1.16 mm for the lateral flexion gaps.

CONCLUSION

Analysis of these first cases highlights the capability of the next generation of imageless robotic-assisted total knee replacement using a semi-autonomous handheld robotic sculpting to maintain accuracy of the desired alignment. The system allows the surgeon to choose freely their own alignment philosophy while maintaining efficiency.

Imageless robotic-assisted total knee arthroplasty is accurate in vivo: a retrospective study to measure the postoperative bone resection and alignment

PURPOSE

Conventional instruments for total knee arthroplasty (TKA) have limited accuracy. The occurrence of outliers can negatively influence the clinical outcome and long-term survival of the implant. Orthopaedic robotic systems were developed to increase the accuracy of implant positioning and bone resections. Several systems requiring preoperative imaging have shown a higher degree of precision compared to conventional instrumentation. An imageless system needs less preoperative time and preparation and is more cost effective. Aim of this study was to find out whether this system is as precise, reproduces accurately the surgeon's planning and reduces the occurrence of outliers.

METHODS

This retrospective study included the first 71 robotic-assisted TKA and 308 conventional TKA in 374 patients. Intraoperatively planned and actual bone resections were compared. Postoperative alignment, measured on full leg weight bearing radiographs, was related to the respective planning and statistically compared between the groups.

RESULTS

Baseline characteristics (age, BMI, ASA, preoperative Knee Society Score and deformity) between both groups were comparable. According to the planned alignment, the postoperative mean difference was - 1.01° in the robotic versus 2.05° in the conventional group. The maximum deviation was - 2/+ 2.5° in the robotic and - 6.6/ + 6.8° in the conventional group. According to the plan, there were no outliers above ± 3° in the robotic versus 24% in the conventional group. The mean difference between planned and measured bone resection was 0.21 mm with a maximum of 2 mm. The 95% confidence interval was at each position 1 mm or below.

CONCLUSIONS

The described imageless robotic system is accurate in terms of coronal alignment and bone resections. In precision, it is superior to conventional instrumentation and could therefore be used to evaluate new alignment concepts.

Robotics improves alignment accuracy and reduces early revision rates for UKA in the hands of low-volume UKA surgeons

PURPOSE

It is known that in uni-compartmental knee arthroplasty (UKA) low-volume surgeons have a higher complication and revision rate than high-volume surgeons. Further, robotic-assisted UKA leads to lower early revision rate as well as fewer limb and joint line outliers compared to conventional UKA. The purpose of this study was to retrospectively analyze the outliers' and revision rate of low-volume UKA surgeons with different robotic systems at short-term follow-up.

METHODS

In this case-control study, 103 robotic-assisted UKAs were included. The procedures were performed between 2016 and 2019 from two low-volume UKA surgeons with an imageless (IL) (63 patients) and image-based (IB) (40 patients) robotic system. Alignment outliers, joint line (JL) reconstruction, complication and revision rates of the two different robotic systems were analyzed. The minimum follow-up was two years. Outliers were defined as a postoperative valgus malalignment greater than 182°. The surgery time for all procedures was evaluated.

RESULTS

The overall revision rate was 3.9% (4 of 103). Two occurred in the IB group (5.0%) and two in the IL group (3.2%). No valgus malalignment outliers were observed in both groups. The mean JL was not distalized by more than 2 mm in both groups (IL: 1.3 ± 1.6 mm vs. IB: 1.8 ± 0.9 mm, p value 0.08). The IL procedures had a significant lower mean surgery time (55 ± 13 min vs. 68 ± 14, p value 0.001).

CONCLUSION

Robotic-assisted UKA is a safe procedure in the hand of low-volume UKA surgeons. Robotic-assisted UKA minimizes overcorrection into valgus mal-alignment. Low revision rates are observed at short-term follow-up for robotic-assisted UKA. The choice of the different robotic systems has no impact on the outcome.