A novel intraoperative sensor for soft tissue balancing in total knee arthroplasty

Geometric Mapping Evaluation for Real-Time Local Sensor Simulation

Medical augmented reality and simulated test environments struggle in accurately simulating local sensor measurements across large spatial domains while maintaining the proper resolution of information required and real time capability. Here, a simple method for real-time simulation of intraoperative sensors is presented to aid with medical sensor development and professional training. During a surgical intervention, the interaction between medical sensor systems and tissue leads to mechanical deformation of the tissue. Through the inclusion of detailed finite element simulations in a real-time augmented reality system the method presented will allow for more accurate simulation of intraoperative sensor measurements that are independent of the mechanical state of the tissue. This concept uses a coarse, macro-level deformation mesh to maintain both computational speed and the illusion of reality and a simple geometric point mapping method to include detailed fine mesh information. The resulting system allows for flexible simulation of different types of localized sensor measurement techniques. Preliminary simulation results are provided using a real-time capable simulation environment and prove the feasibility of the method.

Current role of intraoperative sensing technology in total knee arthroplasty

PURPOSE

Sensors have been introduced within the last 10 years to quantify soft tissue balancing during total knee arthroplasty (TKA) and to give the surgeon objective data. These devices are fairly new and their impact on patient outcome remains uncertain. The aim of this systematic review was to summarize all the relevant surgical and clinical results of sensors for TKA.

METHODS

A PRISMA systematic review was conducted using five databases (PubMed, EMBASE, MEDLINE, GOOGLE SCHOLAR, and the COCHRANE LIBRARY) to identify all available literature that described the surgical and clinical results of sensors for TKA between 2000 and 2021. The main investigated outcome criteria were intraoperative data, postoperative functional and clinical outcome, knee range of motion, complications and revision rates.

RESULTS

Twenty-seven articles were finally included. The maximum reported follow-up was 26 months. A balanced knee with sensor corresponded to a mediolateral difference inferior to 15 lb and a stable posterior drawer test. The standard assessment of knee balance was a poor predictor of the true soft tissue balance when compared to sensor data. At least 60% of TKA needed an additional rebalancing procedure with the sensor, after conventional gap balancing. Achieving a quantitatively balanced knee resulted in a significantly higher patient satisfaction score. But the prospective comparative studies found no demonstrable improvement in clinical outcome, range of motion or complication rate at one year postoperatively for patients undergoing TKA using sensor-guided balancing compared with routine techniques.

CONCLUSION

Even though the use of the intraoperative sensing technology was not related to an improvement in clinical outcome, the current studies showed that using sensors facilitates the reproduction of natural joint stability, and improves the rate of achieving a balanced knee. Sensor use in complex cases could be particularly valuable, but their use in standard practice remains to be defined.

Soft-Tissue Balancing Technology for Total Knee Arthroplasty

» Improperly balanced total knee arthroplasties are at increased risk for complications including residual pain and/or instability, which are often corrected by a revision surgical procedure. » Because of the morbidity and financial burden associated with revision total knee arthroplasty, different technological applications, such as tibial insert sensors and computer-assisted gap balancing, are being used to assist with soft-tissue balancing during primary total knee arthroplasty. » Computer-assisted gap balancing increases the accuracy of mechanical alignment and improves the precision of balancing flexion and extension gaps during total knee arthroplasty. It is unclear whether this translates to improved short-term or long-term outcome measures. Considerations of this technology include increased cost, increased operative time, and a steep learning curve. » Intraoperative sensors increase the accuracy of balancing by quantifying the mediolateral intercompartmental load distribution through the range of motion, which may lead to improved outcome scores, patient satisfaction, higher activity levels, and decreased pain. The advantages of this technology compared with computer assistance include decreased cost and no disruption of operative time or workflow. Limited availability with constrained implants, limited implant choices, and a lack of long-term follow-up data have reduced utilization of intraoperative sensors. » Computer-assisted gap balancing and intraoperative sensors are not yet universally accepted, and the cost-benefit ratio associated with their use remains a consideration in today’s cost-conscious health-care environment. Future research should focus on longer-term follow-up to evaluate implant survivorship, cost-effectiveness, and clinical outcomes.

Does bone cement influence soft tissue balancing in total knee arthroplasty?

BACKGROUND

Soft tissue tension significantly affects the function of total knee arthroplasties. This study aims to evaluate if there is a difference in soft tissue tension, comparing trails to cemented definitive components in TKA.

METHODS

We prospectively compared femorotibial compartment pressures before and after cement fixation of the components in 40 primary TKA. Femorotibial pressures were measured in the medial and lateral compartment with the knee in 10°, 45°, and 90° of flexion (six measurements per TKA), and the difference in pressure between both compartments was calculated in the three positions.

RESULTS

The median femorotibial pressures were not significantly different following cement fixation. There was, however, a change in the difference between medial and lateral compartment pressures after cement fixation. The difference between both compartment pressures decreases after cement fixation. This difference is statistically significant only with the knee in 10° of flexion; mean (IQR) pressures change from 8.5 (five to 14) pounds to six (2.25-10) pounds (P = 0.01).

CONCLUSION

Compartment pressures in TKA do not significantly change after cement fixation. The number of TKA that qualifies as 'balanced' increases after cement fixation, predominantly because the differences between the medial and lateral compartment pressures decrease.

A Systematic Literature Review of Three Modalities in Technologically Assisted TKA

In effort to reduce the revision burden of total knee arthroplasty (TKA), industry emphasis has focused on replacing manual techniques—which are subject to variability—with technological implements. Unfortunately, technological innovation often continues before adequate time for critical evaluation has passed. Therefore, the purpose of this descriptive literature review was to collect a large sample of international data and report on the clinical and economic efficacy of three major types of technologically assisted TKA: navigation, patient-specific instrumentation, and sensorized trials.