Posterior tibial slope and anterior post-cam contact can change knee kinematics in extension in bi-cruciate stabilized total knee arthroplasty

Preoperative tibiofemoral contact point on standing lateral radiograph predicts anteroposterior knee kinematics in total knee arthroplasty

Purpose

This study investigated the tibiofemoral contact point (CP) on standing lateral radiographs in knee osteoarthritis and assessed the relationship between CP and pre- and postoperative knee kinematics in total knee arthroplasty (TKA).

Methods

The intraoperative knee status of 46 knees with varus deformity that underwent bicruciate stabilized TKA using a navigation system was investigated. The intraoperative anteroposterior (AP) position of the femur relative to the tibia at maximum extension, 15°, 30°, 45°, 60° and 90° was evaluated by the navigation system before and after TKA. The CP, defined as the CP between the femur and tibia, was assessed on standing lateral radiographs at the maximum extension of the knee before and 1 year after TKA. CP was expressed as the ratio of tibial plateau distance on a scale of 0-1, with 0 indicating the most anterior position of the femur relative to the tibia.

Results

The mean CP on standing lateral radiographs was 0.54 ± 0.12 and 0.46 ± 0.08 before and after TKA, respectively. The postoperative CP was significantly more anterior than the preoperative CP (p = 0.0002). The mean AP position of the femur relative to the tibia moved anteriorly during early knee flexion both before and after TKA, representing nonanatomical AP movement. The preoperative posterior CP group (CP > 0.54) showed more nonanatomical AP movement from 15° to 60° before and after TKA compared with the preoperative anterior CP group (CP < 0.54).

Conclusion

Preoperative posterior deviation of the femur relative to the tibia in the standing position was a predictive factor for nonanatomical AP knee kinematics. Biomechanical analysis of postoperative knees will be necessary; however, surgeons should focus on preoperative tibiofemoral CP on standing lateral radiographs to predict knee kinematics.

Level of Evidence

Level Ⅲ.

Changes in the anteroposterior position of the femur relative to the tibia impact patient satisfaction in total knee arthroplasty

BACKGROUND

In this study, we aimed to investigate the preoperative and postoperative anteroposterior position (AP) of the femur relative to the tibia in total knee arthroplasty (TKA) and assess the influence of change in the AP position on clinical outcomes.

METHODS

We evaluated 49 knees that underwent bi-cruciate-substituted TKA using a navigation system. The preoperative and postoperative AP position of the femur relative to the tibia at maximum extension, 15°, 30°, 45°, 60°, 90°, 105°, and 120° and maximum flexion angles were calculated. The 2011 Knee Society Score was evaluated preoperatively and 1 year postoperatively. The Wilcoxon signed rank and Spearman's rank correlation tests were performed, with statistical significance set at P < 0.05.

RESULTS

The postoperative AP position was significantly correlated with the preoperative AP position at each measured angle. The postoperative AP positions were statistically more anterior than those preoperatively. Furthermore, the changes in the AP position after TKA negatively correlated with the symptom (P = 0.027 at 30°, P = 0.0018 at 45°, P = 0.0003 at 60°, P = 0.01 at 90°, and P = 0.028 at 105°) and patient satisfaction (P = 0.018 at 60° and P = 0.009 at 90°) scores at 1 year postoperatively.

CONCLUSION

The postoperative AP position of the femur relative to the tibia was strongly influenced by the preoperative those in TKA. Postoperative anterior deviation of the femur relative to the tibia from mid-flexion to deep flexion could worsen clinical outcomes.

Risk Factors for Postoperative Knee Stiffness in Patients with Anteromedial Knee Osteoarthritis Undergoing Unicompartmental Knee Arthroplasty with Cemented Prostheses: A Short-Term, Retrospective, Case-Control Study

BACKGROUND The present study was performed to determine the potential risk factors for postoperative knee stiffness in patients with anteromedial knee osteoarthritis undergoing unicompartmental knee arthroplasty with cemented prostheses. MATERIAL AND METHODS This retrospective cohort study evaluated patients with anteromedial knee osteoarthritis who underwent medial unicompartmental knee arthroplasty at our hospital between May 2017 and May 2020. The patients were divided into 2 groups according to their prognosis: those who experienced knee stiffness after undergoing unicompartmental knee arthroplasty and those who did not. The factors associated with stiffness after UKA were identified using univariate analysis. Frequencies are used to express categorical variables, while mean±SD is used to express continuous variables. The t test and chi-square test were used. A multivariate logistic regression model was built to identify the risk factors for postoperative stiffness. RESULTS We included 590 knees in the study after unicompartmental knee arthroplasty. The overall incidence of postoperative stiffness in unicompartmental knee arthroplasty surgery was 10.17%. In terms of the radiological measurements, varus deformity (70.34% vs 29.66%) and tibial component posterior slope angle (4.8±2.0 vs 4.6±2.0, P<0.001) were significantly differences between the 2 groups. Four independent risk factors for stiffness after unicompartmental knee arthroplasty were identified: age (95% CI, 1.022-1.048), varus deformity (95% CI, 1.186-1.192), tibial component posterior slope angle (95% CI, 0.550-0.870), and preoperative maximum flexion (95% CI, 0.896-0.923). CONCLUSIONS The overall incidence of postoperative knee stiffness in patients with anteromedial knee osteoarthritis undergoing unicompartmental knee arthroplasty with cemented prostheses was 10.17%, which was at a moderate level compared to patients with other diseases undergoing unicompartmental knee arthroplasty. Four independent risk factors were identified: age, varus deformity, preoperative maximum flexion, and tibial component posterior slope angle. Awareness these risk factors might help surgeons prevent the occurrence of postoperative knee stiffness in patients with UKA.

Importance of posterior tibial slope in joint kinematics with an anterior cruciate ligament-deficient knee

Aims

To fully quantify the effect of posterior tibial slope (PTS) angles on joint kinematics and contact mechanics of intact and anterior cruciate ligament-deficient (ACLD) knees during the gait cycle.

Methods

In this controlled laboratory study, we developed an original multiscale subject-specific finite element musculoskeletal framework model and integrated it with the tibiofemoral and patellofemoral joints with high-fidelity joint motion representations, to investigate the effects of 2.5° increases in PTS angles on joint dynamics and contact mechanics during the gait cycle.

Results

The ACL tensile force in the intact knee was significantly affected with increasing PTS angle. Considerable differences were observed in kinematics and initial posterior femoral translation between the intact and ACLD joints as the PTS angles increased by more than 2.5° (beyond 11.4°). Additionally, a higher contact stress was detected in the peripheral posterior horn areas of the menisci with increasing PTS angle during the gait cycle. The maximum tensile force on the horn of the medial meniscus increased from 73.9 N to 172.4 N in the ACLD joint with increasing PTS angles.

Conclusion

Knee joint instability and larger loading on the medial meniscus were found on the ACLD knee even at a 2.5° increase in PTS angle (larger than 11.4°). Our biomechanical findings support recent clinical evidence of a high risk of failure of ACL reconstruction with steeper PTS and the necessity of ACL reconstruction, which would prevent meniscus tear and thus the development or progression of osteoarthritis.

Cite this article: Bone Joint Res 2022;11(10):739–750.

Comparison of the Tibial Posterior Slope Angle Between the Tibial Mechanical Axis and Various Diaphyseal Tibial Axes After Total Knee Arthroplasty

Background

The posterior tibial slope angle (PTS) is crucial for sagittal alignment after total knee arthroplasty (TKA). This study aimed to determine which PTS based on the lateral view of standard knee radiographs (LSKRs; 36 × 43 cm) reflects the PTS based on a full-length lateral tibial radiograph (FLTR).

Methods

A total of 290 patients (355 knees) who underwent primary TKA were retrospectively recruited. Cross-sectional views from the 3-dimensional digital model of the tibial prosthesis and bone complex in the sagittal plane were used as FLTRs and LSKRs. Considering the region 21.5 cm proximal to the site of FLTR as the spot for LSKR to determine the 5 tibial diaphyseal axes, the axis that simulates the PTS as determined by the tibial mechanical axis between the center of the tibial component and the ankle plafond in LSKR was determined and compared.

Results

PTS (α₅) defined by the line connecting the midpoints of tibial width between the region 10-cm distal to the knee joint and the distal end of the tibia based on LSKR revealed the least mean difference (0.13° ± 1.00°) and the strongest correlation (P < .001, r = 0.948) with PTS based on FLTR (α₀). The number of knees in α₅, indicating a difference of <2° from α₀, was 333 of 355 (93.8%). The equivalence test results indicated that α₀ and α₅ were statistically equivalent within a difference of 2° (P < .001).

Conclusions

PTS (α₅) can be used as a clinically reliable substitution of the true PTS on an FLTR for evaluating sagittal alignment after TKA.