Computed Tomography Analysis of Postsurgery Femoral Component Rotation Based on a Force Sensing Device Method versus Hypothetical Rotational Alignment Based on Anatomical Landmark Methods: A Pilot Study

The Effect of Patellar Positioning on Femoral Component Rotation when Performing Flexion Gap Balancing Using a Tensioning Device for Total Knee Arthroplasty

There is an increasing interest in new devices such as tensiometers for flexion gap balancing during total knee arthroplasty (TKA). The purpose of this study was to determine the influence of patella positioning during flexion gap balancing on femoral component rotation. We prospectively evaluated 32 consecutive knees in 31 patients who underwent primary TKA for degenerative osteoarthritis and where soft tissue balancing was performed using the same tensiometer. Preoperative measurements included valgus/varus deformation, mechanical axis, epicondylar axis, and tibial slope. Intraoperatively, measurement of femoral component rotation in 90 degrees of knee flexion was conducted in three different positions of the patella: (1) patella reduced, (2) patella dislocated but not everted, and (3) patella dislocated and everted. The femoral component had significantly higher rotation when the patella was reduced compared with a dislocated patella (4.9 ± 2.1 degrees vs. 4.2 ± 2.2 degrees; p = 0.006) and compared with a dislocated and everted patella (4.9 ± 2.1 degrees vs. 4.1 ± 2.3 degrees; p = 0.006). Varus knees (n = 22) demonstrated significantly increased femoral component rotation if the patella was reduced (5.3 ± 2.2 degrees) compared with dislocated patella without eversion (4.7 ± 2.3 degrees; p = 0.037) and with eversion (4.4 ± 2.5 degrees; p = 0.019). As such, the measurement of the mediolateral flexion gap stability with a laterally dislocated patella leads to a statistically significant overestimation of the lateral ligament stability and an underestimation of the external rotation positioning of the femoral component of approximately 1 degree, which is aggravated in varus knees. This is a Level II, prospective consecutive series study.

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.

Computed tomography is not necessary to assess rotation of the femoral component in navigation-assisted total knee replacement

Objective

To demonstrate that postoperative computed tomography (CT) is not needed if navigation is used to determine the rotational position of the femoral component during total knee replacement (TKR).

Methods

Preoperative CT, navigational, and postoperative CT data of 70 TKR procedures were analysed. The correlation between the rotational angulation of the femur measured by CT and that measured by perioperative navigation was examined. The correlation between the femoral component rotation determined by navigation and that determined by CT was also assessed.

Results

The mean femoral rotation determined by navigation was 2.64° ± 4.34°, while that shown by CT was 6.43° ± 1.65°. Postoperative rotation of the femoral component shown by CT was 3.09° ± 2.71°, which was closely correlated with the angle obtained through the intraoperative transepicondylar axis by navigation (Pearson’s R = 0.930).

Conclusions

Navigation can be used to collect the preoperative, intraoperative, and postoperative data and final position of the TKR. The rotation of the femoral component can be determined using navigation without the need for CT.