Achieving a Balanced Knee in Robotic TKA.

Alexander C Gordon,Michael A Conditt,Matthias A Verstraete

doi:10.3390/s21020535

Alexander C Gordon, Michael A Conditt + Show 1 more

Open Access

https://doi.org/10.3390/s21020535

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Abstract

Total knee arthroplasty (TKA) surgery with manual instruments provides a quantitatively balanced knee in approximately 50% of cases. This study examined the effect of combining robotics technology with real-time intra-operative sensor feedback on the number of quantitatively balanced cases in a consecutive series of 200 robotic-assisted primary TKAs. The robotics platform was used to plan the implant component position using correctable poses in extension and a manual, centrally pivoting the balancer in flexion, prior to committing to the femoral cuts. During the initial trialing, the quantitative state of balance was assessed using an instrumented tibial tray that measured the intra-articular loads in the medial and lateral compartments. These sensor readings informed a number of surgical corrections, including bone recuts, soft-tissue corrections, and cement adjustments. During initial trialing, a quantitatively balanced knee was achieved in only 65% of cases. After performing the relevant soft-tissue corrections, bone recuts, and cement adjustments, 87% of cases ended balanced through the range of motion. Meanwhile, this resulted in a wide range of coronal alignment conditions, ranging from 6° valgus to 9° varus. It is therefore concluded that gaps derived from robotics navigation are not indicative for a quantitatively balanced knee, which was only consistently achieved when combining the robotics platform with real-time feedback from intra-operative load sensors.

Highlights

Total knee arthroplasty has been a successful intervention to relieve pain and restore function in patients with end stage gonarthrosis
The results indicate that sensor feedback has the potential to improve the success of achieving a balanced knee through the range of motion; an increase in balanced knees was observed from 67% to 87% after considering sensor feedback, while eliminating cases with load outliers (e.g., >70 lbf per compartment)
To achieve a quantitatively balanced knee in this series, the surgeon performed a wide range of soft-tissue corrections in combination with bone recuts and cement adjustments

Summary

Introduction

Total knee arthroplasty has been a successful intervention to relieve pain and restore function in patients with end stage gonarthrosis. Computer assisted navigation systems (CAS), introduced in the 2000s, offered promise of improved alignment and outcomes. Within the available CAS systems, ligament balance data was offered to a surgeon by way of numerical gap measurements. The surgeon can adjust the placement plan of the components to provide a desired gap for each of the four measurements (extension and flexion in combination with respectively medial and lateral side of the knee) [4]. An intra-operative kinetic balancing system has been introduced to be used with a variety of total knee systems. This device offers surgeons a quantitative assessment of load across the joint throughout an arc of motion and is used after the cuts have been made and with the trial components in place [5]. The load measurement device is located in the tibial trial insert and provides the loads in each compartment throughout the range of motion (Figure 1b)

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