Evaluation of anterior cruciate ligament surgical reconstruction through finite element analysis

Development of a novel geometrically-parametric patient-specific finite element model for anterior cruciate ligament reconstruction

PURPOSE

A personalized model of the knee joint, with adjustable effective geometric parameters for the transplanted autograft diameter in Anterior Cruciate Ligament Reconstruction (ACLR) using the bone-patella-tendon-bone (BPTB) technique, has been developed. The model will assist researchers in understanding how different graft sizes impact a patient's recovery over time.

METHODS

The study involved selecting a group of individuals without knee injuries and one patient who had undergone knee surgery. Gait analysis was conducted on the control group and the patient at various time points. A 3D model of the knee joint was created using medical images of the patient. Forces and torques obtained from the gait analysis were applied to the model to perform finite element analysis.

RESULTS

The results of the finite element (FE) analysis, along with kinetic data from both groups, indicate that models with diameters of 7.5 mm and 12 mm improved joint motion during follow-up after ACLR. Additionally, a comparison of the stress applied to the ACL model revealed that a 12 mm autograft diameter showed a more favorable trend in patient recovery during the three follow-up intervals after ACL reconstruction surgery.

CONCLUSION

The development of a personalized parametric model with adjustable geometric parameters in ACLR, such as the transplanted autograft diameter, as presented in this study, along with FE using the patient's kinetic data, allows for the examination and selection of an appropriate autograft diameter for Patella Tendon grafting. This can help reduce stress on the autograft and prevent damage to other knee joint tissues after ACLR.

Surgical parameters influence paediatric knee kinematics and cartilage stresses in anterior cruciate ligament reconstruction: Navigating subject-specific variability using neuromusculoskeletal-finite element modelling analysis

PURPOSE

Anterior cruciate ligament (ACL) rupture is increasingly common in paediatric and adolescent populations, typically requiring surgical ACL reconstruction (ACLR) to restore knee stability. However, ACLR substantially alters knee biomechanics (e.g., motion and tissue mechanics) placing the patient at elevated risk of early-onset knee osteoarthritis.

METHODS

This study employed a linked neuromusculoskeletal (NMSK)-finite element (FE) model to determine effects of four critical ACLR surgical parameters (graft type, size, location and pre-tension) on tibial articular cartilage stresses in three paediatric knees of different sizes during walking. Optimal surgical combinations were defined by minimal kinematic and tibial cartilage stress deviations in comparison to a corresponding intact healthy knee, with substantial deviations defined by normalized root mean square error (nRMSE) > 10%.

RESULTS

Results showed unique trends of principal stress deviations across knee sizes with small knee showing least deviation from intact knee, followed by large- and medium-sized knees. The nRMSE values for cartilage stresses displayed notable variability across different knees. Surgical combination yielding the highest nRMSE in comparison to the one with lowest nRMSE resulted in an increase of maximum principal stress on the medial tibial cartilage by 18.0%, 6.0% and 1.2% for small, medium and large knees, respectively. Similarly, there was an increase of maximum principal stress on lateral tibial cartilage by 11.2%, 4.1% and 12.7% for small, medium and large knees, respectively. Knee phenotype and NMSK factors contributed to deviations in knee kinematics and tibial cartilage stresses. Although optimal surgical configurations were found for each knee size, no generalizable trends emerged emphasizing the subject-specific nature of the knee and neuromuscular system.

CONCLUSION

Study findings underscore subject-specific complexities in ACLR biomechanics, necessitating personalized surgical planning for effective restoration of native motion and tissue mechanics. Future research should expand investigations to include a broader spectrum of subject-specific factors to advance personalized surgical planning.

LEVEL OF EVIDENCE

Level III.

Sensitivity analysis of paediatric knee kinematics to the graft surgical parameters during anterior cruciate ligament reconstruction: A sequentially linked neuromusculoskeletal-finite element analysis

BACKGROUND AND OBJECTIVE

Incidence of paediatric anterior cruciate ligament (ACL) rupture has increased substantially over recent decades. Following ACL rupture, ACL reconstruction (ACLR) surgery is typically performed to restore passive knee stability. This surgery involves replacing the failed ACL with a graft, however, surgeons must select from range of surgical parameters (e.g., type, size, insertion, and pre-tension) with no robust evidence guiding these decisions. This study presents a systemmatic computational approach to study effects of surgical parameter variation on kinematics of paediatric knees.

METHODS

This study used sequentially-linked neuromusculoskeletal (NMSK) finite element (FE) models of three paediatric knees to estimate the: (i) sensitivity of post-operative knee kinematics to four surgical parameters (type, size, insertion, and pre-tension) through multi-input multi-output sensitivity analysis; (ii) influence of motion and loading conditions throughout stance phase of walking gait on sensitivity indices; and (iii) influence of subject-specific anatomy (i.e., knee size) on sensitivivty indices. A previously validated FE model of the intact knee for each subject served as a reference against which ACLR knee kinematics were compared.

RESULTS

Sensitivity analyses revealed significant influences of surgical parameters on ACLR knee kinematics, albeit without discernible trend favouring any one parameter. Graft size and pre-tension were primary drivers of variation in knee translations and rotations, however, their effects fluctuated across stance indicating motion and loading conditions affect system sensitivity to surgical parameters. Importantly, the sensitivity of knee kinematics to surgical parameter varied across subjects, indicating geometry (i.e., knee size) influenced system sensitivity. Notably, alterations in graft parameters yielded substantial effects on kinematics (normalized root-mean-square-error > 10 %) compared to intact knee models, indicating surgical parameters vary post-operative knee kinematics.

CONCLUSIONS

Overall, this initial study highlights the importance of surgical parameter selection on post-operative kinematics in the paediatric ACLR knee, and provides evidence of the need for personalized surgical planning to ultimately enhance patient outcomes.

Can lateral tenodesis improve the rotational stability of the ACL reconstruction? A finite element analysis

One of the most common knee injuries is the Anterior Cruciate Ligament (ACL) rupture with severe implications on knee stability. The usual treatment is the ACL Reconstruction (ACLR) surgery where the surgeon replaces the torn ligament with a graft in an effort to restore knee kinematics. In case of excessive rotatory instability, Lateral Extra-Articular Tenodesis (LET) can be performed in combination with ACLR. Additionally, LET appears to reduce ACLR graft forces minimizing graft failure chances. However, there are concerns about overconstraining physiological rotation. To gain insight in this controversial topic, we developed an automatic, open-source tool to create a series of Finite Element (FE) models attempting to investigate the interactions of ACLR and LET through simulation. We started by creating a validated model of the healthy knee joint that served as reference for subsequent FE simulations. Then, we created FE models of standalone ACLR and combined ACLR-LET. Each model was assessed by applying a loading profile that resembles the reduction phase of the Pivot-Shift clinical exam. We measured the External Tibia Rotation (ETR), the Posterior Tibia Translation (PTT) of the lateral tibial compartment, and the ACLR graft stress developed around the femoral tunnel insertion site. We observed the following: a) LET reduces ETR and PTT compared to isolated ACLR, b) combined ACLR-LET is more sensitive to LET graft pretension with lower values showcasing performance closer to the healthy joint, c) LET reduces ACLR graft forces for the same pretension values, d) LET exhibits significant overconstraint for higher pretension values. In general, these findings are in agreement with relevant clinical studies and accentuate the potential of the developed framework as a tool that can assist orthopaedists during surgery planning. We provide open access for the FE models of this study to enhance research transparency, reproducibility and extensibility.

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.

Knee instability caused by altered graft mechanical properties after anterior cruciate ligament reconstruction: the early onset of osteoarthritis?

Anterior cruciate ligament (ACL) rupture is a very common knee joint injury. Torn ACLs are currently reconstructed using tendon autografts. However, half of the patients develop osteoarthritis (OA) within 10 to 14 years postoperatively. Proposedly, this is caused by altered knee kine(ma)tics originating from changes in graft mechanical properties during the in vivo remodeling response. Therefore, the main aim was to use subject-specific finite element knee models and investigate the influence of decreasing graft stiffness and/or increasing graft laxity on knee kine(ma)tics and cartilage loading. In this research, 4 subject-specific knee geometries were used, and the material properties of the ACL were altered to either match currently used grafts or mimic in vivo graft remodeling, i.e., decreasing graft stiffness and/or increasing graft laxity. The results confirm that the in vivo graft remodeling process increases the knee range of motion, up to >300 percent, and relocates the cartilage contact pressures, up to 4.3 mm. The effect of remodeling-induced graft mechanical properties on knee stability exceeded that of graft mechanical properties at the time of surgery. This indicates that altered mechanical properties of ACL grafts, caused by in vivo remodeling, can initiate the early onset of osteoarthritis, as observed in many patients clinically.

Isokinetic exercises in quadriceps strength and endurance recovery after anterior cruciate ligament reconstruction

Background/Aim: Muscle strength and endurance recovery of the quadriceps after anterior cruciate ligament reconstruction is necessary for normal knee function. In addition to the use of the isokinetic dynamometer for diagnostic purposes, its possible therapeutic effect is also important, ie targeted correction of the measured muscle deficit. This work was aimed to examine the level of quadriceps strength and endurance recovery 6 months after the anterior cruciate ligament reconstruction in patients who performed isokinetic training and to determine whether it is a superior therapeutic intervention compared to isodynamic training. Methods: A total of 70 patients of both sexes were monitored in a prospective clinical study. Three months postoperatively, all patients had quadriceps torque measured to body weight on an isokinetic dynamometer at angular speeds of 60 and 180 °/s. Patients were divided into two groups according to the type of applied rehabilitation protocol. Group A patients (n = 35) underwent a rehabilitation program 5 times a week using an individual kinesitherapy program (isometric and isotonic exercises for quadriceps and hamstrings) and neuromuscular electrostimulation of the quadriceps. In addition patients from group B (n = 35) were included in targeted isokinetic exercises for the quadriceps. Control isokinetic testing was performed 6 months after surgery. The comparison of the effect of the applied therapeutic procedures in groups A and B was performed with the Student t-test (p < 0.05). Results: An average age of patients was 27.29 ± 5.94 years. In patients in group B, statistically significantly higher values of the peak torque to body weight were measured at angular velocities of 60 and 180 °/s for the quadriceps of the operated knee 6 months after reconstruction of the anterior cruciate ligament with hamstring tendons (p < 0.05). Conclusion: Isokinetic training achieved significantly better quadriceps strength and endurance in patients 6 months after anterior cruciate ligament reconstruction with hamstring tendons compared to dynamic exercises.