Biomechanical role of posterior cruciate ligament in total knee arthroplasty: A finite element analysis

Influence of posterior cruciate ligament tension on tibiofemoral and patellofemoral joint contact mechanics in cruciate-retaining total knee replacement: a combined musculoskeletal multibody and finite-element simulation

The influence of posterior cruciate ligament (PCL) tension on the clinical outcome of cruciate-retaining total knee replacement (CR-TKR) remains controversial. Various numerical approaches have been used to study this influence systematically, but the models used are limited by certain assumptions and simplifications. Therefore, the objective of this computational study was to develop a combined musculoskeletal multibody and finite-element simulation during a squat motion to 90° knee flexion with a CR-TKR design to overcome previous limitations regarding model inputs. In addition, different PCL tensions (tight, lax, resected) were modeled and the influence on tibiofemoral and resurfaced patellofemoral joint dynamics and contact stresses was evaluated. The effect of the PCL on knee joint dynamics and contact stresses was more pronounced at higher flexion angles. Tibiofemoral joint dynamics were influenced and a tight PCL induced increased posterior femoral translation during flexion. The maximum contact stress in the tibial insert increased from 20.6 MPa to 22.5 MPa for the resected and tightest PCL at 90° knee flexion. Patellofemoral joint dynamics were only slightly affected by PCL tension. However, the maximum contact stress in the patellar component decreased from 58.0 MPa to 53.7 MPa for the resected and tightest PCL at 90° knee flexion. The combination of musculoskeletal multibody and finite-element simulation is a sufficient method to comprehensively investigate knee joint dynamics and contact stresses in CR-TKR. The PCL tension after CR-TKR affects joint dynamics and contact stresses at the articulating implant surfaces.

Biomechanical comparison of all-polyethylene total knee replacement and its metal-backed equivalent on periprosthetic tibia using the finite element method

BACKGROUND

Total knee arthroplasty (TKA) with all-polyethylene tibial (APT) components has shown comparable survivorship and clinical outcomes to that with metal-backed tibial (MBT). Although MBT is more frequently implanted, APT equivalents are considered a low-cost variant for elderly patients. A biomechanical analysis was assumed to be suitable to compare the response of the periprosthetic tibia after implantation of TKA NexGen APT and MBT equivalent.

METHODS

A standardised load model was used representing the highest load achieved during level walking. The geometry and material models were created using computed tomography data. In the analysis, a material model was created that represents a patient with osteopenia.

RESULTS

The equivalent strain distribution in the models of cancellous bone with an APT component showed values above 1000 με in the area below the medial tibial section, with MBT component were primarily localised in the stem tip area. For APT variants, the microstrain values in more than 80% of the volume were in the range from 300 to 1500 με, MBT only in less than 64% of the volume.

CONCLUSION

The effect of APT implantation on the periprosthetic tibia was shown as equal or even superior to that of MBT despite maximum strain values occurring in different locations. On the basis of the strain distribution, the state of the bone tissue was analysed to determine whether bone tissue remodelling or remodelling would occur. Following clinical validation, outcomes could eventually modify the implant selection criteria and lead to more frequent implantation of APT components.

Model Properties and Clinical Application in the Finite Element Analysis of Knee Joint: A Review

The knee is the most complex joint in the human body, including bony structures like the femur, tibia, fibula, and patella, and soft tissues like menisci, ligaments, muscles, and tendons. Complex anatomical structures of the knee joint make it difficult to conduct precise biomechanical research and explore the mechanism of movement and injury. The finite element model (FEM), as an important engineering analysis technique, has been widely used in many fields of bioengineering research. The FEM has advantages in the biomechanical analysis of objects with complex structures. Researchers can use this technology to construct a human knee joint model and perform biomechanical analysis on it. At the same time, finite element analysis can effectively evaluate variables such as stress, strain, displacement, and rotation, helping to predict injury mechanisms and optimize surgical techniques, which make up for the shortcomings of traditional biomechanics experimental research. However, few papers introduce what material properties should be selected for each anatomic structure of knee FEM to meet different research purposes. Based on previous finite element studies of the knee joint, this paper summarizes various modeling strategies and applications, serving as a reference for constructing knee joint models and research design.

Role of the proximal tibiofibular joint on the biomechanics of the knee joint: A three-dimensional finite element analysis

PURPOSE

The proximal tibiofibular joint (PTFJ) is easily ignored, although many diseases of the knee are caused by PTFJ injuries. Therefore, studying PTFJ biomechanics is very important. The effects of PTFJ injury on ankle function have been reported. However, few studies have assessed the effects of PTFJ injury on the knee joint. This study was performed to describe the biomechanical effects of PTFJ on the knee joint according to a three-dimensional finite element model.

METHODS

The knee joint of a healthy volunteer was scanned by CT and MRI. CT and MRI scanning data in DICOM format were imported into Mimics software. Subsequently, 3D models of the normal and PTFJ injured knee, including the bone, cartilage, meniscus and ligament structures were established, and their validity was verified on the basis of available studies in literature. The biomechanical changes in the two knee models under different conditions were compared.

RESULTS

The validity of the intact model was verified. No significant difference was observed in tibial mobility in the two models under the conditions of 134 N forward, 10 N·m internal rotation and 10 N·m valgus load. After application of 134 N backward, 10 N·m varus and external rotation load with respect to the tibia, the posterior movement of the tibia and the varus and external rotation angles of the tibia were 3.583±0.892 mm, 4.799±0.092° and 18.963±0.027° in the normal knee model, and 5.127±1.224 mm, 5.277±0.104° and 21.399±0.031° in the PTFJ injury model, respectively, and a significant statistical difference was observed.

CONCLUSIONS

PTFJ played an important role in maintaining the posterolateral stability of the knee joint and thus deserves more attention in clinical operations.

Biomechanical analysis of all-polyethylene total knee arthroplasty on periprosthetic tibia using the finite element method

BACKGROUND AND OBJECTIVE

Total knee arthroplasty (TKA) with modern all-polyethylene tibial (APT) components has shown high long-term survival rates and comparable results to those with metal-backed tibial components. Nevertheless, APT components are primarily recommended for older and low-demand patients. There are no evidence-based biomechanical guidelines for orthopaedic surgeons to determine the appropriate lower age limit for implantation of APT components. A biomechanical analysis was assumed to be suitable to evaluate the clinical results in patients under 70 years. The scope of this study was to determine biomechanically the appropriate lower age limit for implantation of APT components.

METHODS

To generate data of the highest possible quality, the geometry of the computational models was created based on computed tomography (CT) images of a representative patient. The cortical bone tissue model distinguishes the change in mechanical properties described in three parts from the tibial cut. The cancellous bone material model has a heterogeneous distribution of mechanical properties. The values used to determine the material properties of the tissues were obtained from measurements of a CT dataset comprising 45 patients.

RESULTS

Computational modeling showed that in the majority of the periprosthetic volume, the von Mises strain equivalent ranges from 200 to 2700 με; these strain values induce bone modeling and remodeling. The highest measured deformation value was 2910 με. There was no significant difference in the induced mechanical response between bone models of the 60-year and 70-year age groups, and there was <3% difference from the 65-year age group.

CONCLUSIONS

Considering in silico limitations, we suggest that APT components could be conveniently used on a bone with mechanical properties of the examined age categories. Under defined loading conditions, implantation of TKA with APT components is expected to induce modeling and remodeling of the periprosthetic tibia. Following clinical validation, the results of our study could modify the indication criteria of the procedure, and lead to more frequent implantation of all-polyethylene TKA in younger patients.

Biomechanical analysis of femoral stems in hinged total knee arthroplasty in physiological and osteoporotic bone

BACKGROUND AND OBJECTIVE

Adequate fixation is a requisite for hinged Total Knee Arthroplasty (TKA): consequently, several stem solutions are currently available. However, there are no evidence-based biomechanical guidelines for surgeons to determine the appropriate stem length and whether to use cemented or press-fit fixation. The objective of this study is therefore to compare, using a validated finite-element model, bone stresses and implant micromotions in different configurations.

METHODS

The 3D bone geometries were obtained from CT-scans reconstruction and the 3D model components of an Endo-Model Rotating Hinge (WALDEMAR LINK GmbH & Co. KG, Hamburg, Germany) were generated from industrial designs provided by the manufacturer. Sixteen configurations were investigated considering four stem lengths (50, 95, 120, 160 mm), cemented and press-fit fixation and physiological and osteoporotic bone properties. A further configuration without stem was analyzed as control. Average Von-Mises stresses, risk of fracture and micromotions were extracted in several regions of interest at 0° and 90° of flexion, under physiological load conditions.

RESULTS

Generally, longer stems guarantee better fixation compared to short ones; however, they induce higher stress-shielding effect in the distal region of the femur (even greater for press-fit stems, with values up to 38.5% greater than cemented ones). The cemented configurations, especially in case of 50 mm and 95 mm lengths, induce lower micromotions (down to 16% lower) compared to their respective press-fit configurations. The osteoporotic RF values were greater than the physiological ones (up to 20.5%), but always below the bone limit of fracture.

CONCLUSIONS

According to this study, when surgeons need to select a femoral stem in a hinged TKA aiming to proper stability and bone stress, the preferable option would be short cemented stems.

A finite element study of fatigue load effects on total hip joint prosthesis

The main goal of this study was to perform a fatigue analysis and compare the results for different materials. A 72 years old patient was chosen and his hip radiographic/CT scan images were used to construct the geometry. We used four different material including Titanium, Titanium alloy, Cobalt-Chrome, and Stainless steel. The material characteristics of these prostheses were extracted from the literature. All models were exported to ANSYS software for mathematical analysis and the Von-Mises criteria, deformations, and the fatigue life were calculated for each material. Our findings showed that titanium prosthesis tolerated the lowest stress (i.e., 591 MPa for static, and 687 MPa for fatigue loading) and highest safety factor (i.e., 1.54). We found out that Titanium material could be used as the most appropriate one for the hip prosthesis due to lower stress concentration and longer life compared to other materials.

In vivo kinematical validated knee model for preclinical testing of total knee replacement

BACKGROUND AND OBJECTIVE

A computational knee model facilitates efficient component design evaluations and preclinical testing under various dynamic loadings. However, the development of a highly mimicked dynamic whole knee model with specified ligament constraints that provides high predictive accuracy with in-vivo experiments remains a challenge.

METHODS

In the present study, a musculoskeletal integrated force-driven explicit finite-element knee model with tibiofemoral and patellofemoral joints constrained with detailed soft tissue was developed. A proportional-integral-derivative controller was concurrently added to the knee model to track the boundary conditions. The actuations of the quadriceps and hamstrings were predicted via a subject-specific musculoskeletal model and matched with electromyography results.

RESULTS

Compared to in-vivo fluoroscopic results in a gait cycle, the predicted results of the kinematics of the tibiofemoral joint exhibited an agreement in terms of tendency and magnitude (anterior-posterior translation: RMSE = 1.1 mm, r² = 0.87; inferior-superior translation: RMSE = 0.83 mm, r² = 0.84; medial-lateral translation: RMSE = 0.82 mm, r² = 0.05; flexion-extension rotation: RMSE = 0.23°, r² = 1; internal-external rotation: RMSE = 1.85°, r² = 0.65; varus-valgus rotation: RMSE = 1.39°, r² = 0.08). Contact mechanics, including the contact area, pressure, and stress, were synchronously simulated on the tibiofemoral and patellofemoral joints.

CONCLUSIONS

The study provides a calibrated knee model and a kinematical validation approach that can be widely used in preclinical testing and knee prosthesis design.

A comparative finite element simulation of locking compression plate materials for tibial fracture treatment

The locking compression plate (LCP) system has several advantages in fracture fixation combining angular stability with the use of locking screws with traditional fixation techniques. However, the system is complex and requiring careful attention to biomechanical principles and good surgical technique. Due to the set of complicate stresses and strains in the LCP system after implantation, the material, which is being used here, is deemed important. However, so far the materials have been limited to the stainless steel (SS) or titanium (Ti). This study was therefore aimed at investigate the biomechanical performance of the internal tibial locked plates at different material properties, including SS, Ti, carbon/polyether ether ketone (PEEK) composite, in treating medial tibial fracture using patient-specific finite element (FE) model of the human tibia. The carbon/PEEK composite materials were used at three different fiber plies configurations. Simulated loading was applied at 60:40 ratios on the medial:lateral aspect. The model was fixed distally in all degrees of freedom. The results revealed the highest stress (307.10 MPa) and the lowest strain (0.14%) at Ti LCP system. The carbon/PEEK LCP system at configuration I and III showed low stress (∼60 MPa) and high strain (0.70%), which are suitable points for designing of an internal LCP system. On the other hand, the highest value of stress in callus region was 4.78 MPa (Carbon PEEK/Configuration I) and the strain variations of callus region were between 1.46% and 3.82% among all materials. These results implied the advantage of carbon/PEEK composite materials in LCP system as they can tolerate higher strains at lower stresses.