Distinctions of introarticular force distribution between genesis-II posterior stabilized and cruciate retaining total knee arthroplasty: An intraoperative comparative study of 45 patients

Effect of posterior cruciate ligament on knee pressure and gap measured by an electronic sensor during total knee arthroplasty

PURPOSE

The purpose of this study was to evaluate the change in posterior cruciate ligament (PCL) tension by directly measuring the pressure changes in the knee joint when the ligament was released or resected during total knee arthroplasty.

METHODS

We prospectively analyzed 54 patients who underwent primary total knee arthroplasty (67 knees) from October 2019 to January 2022. An electronic pressure sensor was used to measure the pressure changes in the medial and lateral chambers on PCL retention, recession or resection.

RESULTS

At 0°, 45°, 90° and 120° of flexion, the total pressure in the knee joint of PCL retention was significantly higher than with PCL recession, and even higher than PCL resection. PCL recession or resection affected knee joint extension, and the medial/lateral pressure in the knee joint decreased. Pressure in the lateral compartment showed no significant change during knee flexion, whereas pressure in the medial compartment was significantly decreased, which also led to a change in the ratios of the medial and lateral pressures in the knee joint. After PCL resection, the flexion gap (90°) increased significantly more than the extension (0°) gap, while 46 cases displayed the same change in the flexion and extension gaps after PCL resection of the 67 cases.

CONCLUSION

The PCL retained partial function after tibial recession. PCL resection affected both the flexion and extension gaps; although the average flexion gap increased more than the extension gap, the change in most cases of these two gaps was the same.

Sensor Use in Cruciate-Retaining Total Knee Arthroplasty Compared with Posterior-Stabilized Total Knee Arthroplasty: Load Balancing and Posterior Femoral Rollback

The purpose was to investigate the proportion of severe load imbalance after appropriate conventional gap balancing and analyze the intraoperative kinematics after load balancing in cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasties (TKAs). In total, 45 sensor-assisted CR and 45 PS TKAs using NexGen prosthesis were prospectively evaluated. After appropriate conventional gap balancing, the loads at 10, 45, and 90 degrees of knee flexion were evaluated with a wireless load sensor placed in trial implants. The proportion of severe load imbalance (medial load-lateral load >75 lbs) was investigated. After load balancing, location of the femorotibial contact point was investigated at each flexion angle to analyze femorotibial kinematics. The proportion of the severe load imbalance was significantly higher in CR TKAs at the 10 degrees knee flexion (37.8 vs. 15.6%, p = 0.031). This proportion was higher in CR TKAs than in PS TKAs at the 45 and 90 degrees knee flexion angles, but without statistical significance (31.1 vs. 15.6%, p = 0.134 and 33.3 vs. 15.6%, p = 0.085, respectively). After load balancing, consistent posterior femoral rollback occurred in medial and lateral compartments during 90 degrees flexion in CR TKAs (p < 0.001), but not in PS TKAs. Medial pivot kinematics was not observed in both TKA designs. The sensor was more beneficial in CR TKAs for achieving appropriate load balancing and consistent posterior femoral rollback compared with PS TKAs. Further studies are required to identify target load distribution to restore ideal knee kinematics after TKA. This study shows level of evidence II.

Effects of the posterior cruciate ligament and tibia insert thickness on tibiofemoral joint pressure in total knee arthroplasty: a cadaveric study

Background

Emerging knowledge has highlighted the significant role of the posterior cruciate ligament (PCL) in total knee arthroplasty (TKA). However, few studies have reported how the PCL affects tibiofemoral joint pressure (TFP), and differences in the effects of the PCL and the effects of tibial insert thickness on TFP remain unknown. Thus, this study used the sensor technique to analyze and compare the effects of PCL and tibial insert thickness on TFP during knee flexion.

Methods

Cruciate-retaining total knee arthroplasty (CR-TKA) was performed in 8 cadaveric knees. The PCL was partially released and completely resected sequentially while the tibial insert thickness was increased from 10- to 12-mm at 1-mm intervals. With the optimal tibial insert in place, the effects of PCL release and resection on medial and lateral TFP during knee flexion were analyzed. Medial tibiofemoral joint pressure (MTFP) with PCL retention and a 12-mm tibial insert was set as the baseline. The effects of PCL resection without tibial insert thickness reduction on MTFP were compared to the effects of PCL retention with a 1- or 2-mm thinning of the tibial insert on MTFP during knee flexion.

Results

PCL resection significantly reduced MTFP at 90° and 120° of knee flexion (P=0.01 and P=0.03, respectively). Partial release and complete resection of the PCL did not significantly reduce lateral tibiofemoral joint pressure (LTFP) at 10°, 30°, 60°, 90° and 120° of knee flexion (P=0.68, P=0.60, P=0.62, P=0.21 and P=0.12, respectively). At 10°, 30°, and 60° of knee flexion, a 1-mm reduction in the tibial insert had a greater effect on MTFP than did the resection of the PCL. In contrast, at 90° of knee flexion, MTFP was more affected by PCL resection than by a 2-mm reduction of the tibial insert.

Conclusions

The PCL predominantly affects MTFP at 90° and 120° of knee flexion. The impact of PCL resection on MTFP at 90° flexion was higher than the impact of a 2-mm thinning of the tibial insert.

J-curve design total knee arthroplasty: the posterior stabilized shows wider medial pivot compared to the cruciate retaining during chair raising

PURPOSE

Which total knee arthroplasty (TKA) design represents the better solution to restore a correct knee biomechanics is still debated. The aim of this study was to compare posterior stabilized (PS) and cruciate retaining (CR) version of the same TKA design (femoral component with an anatomic sagittal radius-J-curve design) by the use of dynamic Roentgen stereophotogrammetric analysis (RSA). The hypothesis was that the two models influence differently in vivo knee kinematic.

METHODS

A cohort of 16 randomly selected patients was evaluated 9 months after surgery: Zimmer PERSONA® was implanted, eight with CR design and eight with PS design. The kinematic evaluations were performed using a Dynamic RSA (BI-STAND DRX 2) developed in our Institute, during the execution of the sit-to-stand motor task. The motion parameters were obtained using the Grood and Suntay decomposition and the low-point kinematics methods.

RESULTS

PS TKA lateral femoral compartment had a wider anterior translation (17 ± 2 mm) than the medial one (11 ± 2 mm), while the two compartments of CR TKA showed a similar anterior translation (medial: 9 ± 2 mm/lateral: 11 ± 2 mm). T test for comparison between CR and PS TKA of antero-posterior translation showed a statistically significant difference (p < 0.05) in the flexion range between 15° and 40°. The CR prosthesis did not anteriorly translate during flexion. The PS design translated anteriorly showing a roll-forward mechanism during extension from 80° to 18° of flexion and a posterior translation from 18° to 0°. The same significant differences (p < 0.05) between the PS and CR groups were found comparing the low-point positions of the femoral condyles in the range of flexion between 25° and 40° for the medial compartment and between 15° and 25° for the lateral compartment.

CONCLUSIONS

Dynamic RSA was able to investigate for the first time in vivo the kinematic behaviour of PS and CR version of the same TKA J-curve design. PS type showed a medial pivot during sit-to-stand motion task, while the CR type showed a cylindrical movement. Further studies are needed to evaluate the impact of different TKA designs on clinical results.

LEVEL OF EVIDENCE

IV.