Paper Submission & Registration
8th Dutch Bio-Medical Engineering Conference
15:20   Knee
Chair: Bart Verkerke
15 mins
Musculoskeletal simulation of cruciate-retaining total knee arthroplasty to predict the biomechanical effects of tibial polyethylene thickness
Periklis Tzanetis, Marco Marra, René Fluit, Bart Koopman, Nico Verdonschot
Abstract: Introduction: Selection of an optimum tibial polyethylene (PE) thickness in total knee arthroplasty (TKA) is important to achieve soft-tissue balance. However, there remains a paucity of information about the relationship between PE thickness and kinetic patterns across knee joint articulations and surrounding ligaments. This study aims to investigate the influence of PE thickness on ligament forces and compressive tibiofemoral and patellofemoral contact forces in a cruciate-retaining TKA. Methods: A previously validated subject-specific musculoskeletal model of TKA was configured to integrate a Triathlon (Stryker, Kalamazoo, Michigan) cruciate-retaining implant1. PE thickness was varied with 2-mm increments compared to the baseline (9 mm), with three cases in total; 9, 11, and 13 mm. The effect of PE thickness was evaluated by simulating a chair-rise activity, comprising sit-to-stand and stand-to-sit movements, using the AnyBody musculoskeletal simulation software. Results: Increasing PE thickness produced higher ligament forces both in flexion and extension, although the effect in the posterior cruciate ligament was more perceivable in the flexed knee. Medial collateral, lateral collateral, and posterior cruciate ligament forces increased by 128%, 207%, and 45%, on average, respectively, as PE thickness changed from 9 to 11 mm; the corresponding average percentage increase for 4 mm more PE thickness relative to the reference case was 370%, 529%, and 111%. The tibiofemoral contact force increased on average by 17% and 44% for each incremental change, respectively, denoting a marked effect at 90° of knee flexion angle. Conversely, the patellofemoral contact force showed a slight average decrease of 4% (11 mm) and 7% (13 mm) compared to baseline. Conclusion: Overstuffing the tibiofemoral joint space generates higher ligament forces and consequently increased tibiofemoral loads. However, thicker tibial inserts can be beneficial for the patella since the Quadriceps transfer more load to the femur as the patellar relative position moves distally. This methodology provides orthopedic surgeons with quantitative data on the sensitivity of ligament and contact forces to PE thickness variations and can be developed to further optimize navigated or robotically-assisted TKA. References: 1. Marra, M.A., et al., A subject-specific musculoskeletal modeling framework to predict in vivo mechanics of total knee arthroplasty. 2015. 137(2).
15 mins
Oğulcan Güldeniz, Periklis Tzanetis, Marco A. Marra, René Fluit, Nico Verdonschot
Abstract: ABSTRACT Articular geometrical features of the knee present significant variability amongst a population. Statistical shape modelling (SSM) is a promising tool that captures this variability in the morphological knee phenotype [1]. Shape modes are the principal components in SSM and represent the main sources of variability in the articular geometry. Success rates of total knee implants have not been correlated to these shape modes [2], e.g. the effects of shape modes on the outcomes of total knee arthroplasty (TKA) has not yet been investigated. The aim of this study is to assess the potential effects of shape modes on the simulated outcomes of TKA, using a combination of statistical shape modelling of the knee and computational musculoskeletal simulation. Musculoskeletal models for the first five knee shape modes will be generated (instances including the mean shape mode and ± 1.5 standard deviations). Mechanical soft-tissue properties will be assigned based on literature and kept equal throughout the study. Intact as well as implanted joint models will be created for each shape mode, providing a proxy for the pre- and post-operative scenarios. To assess the effects of shape modes on the outcomes of TKA, tibiofemoral and patellofemoral joint contact forces, contact point trajectories, muscle and ligament forces, and patella trajectory for the intact and TKA cases will be simulated using a previously established methodology [3]. The results of pre- and post-TKA will be compared with each other for each shape mode. Differences will be quantified using the root-mean-square error (RMSE), correlation analysis and Sprague and Geers metrics. This study aims at providing a better understanding of the effects of the tibiofemoral morphological phenotype on the outcomes of TKA using SSM and musculoskeletal simulations. The results of this study will provide important insights as to how each morphological phenotype may influence the outcomes of surgical interventions. Furthermore, it may provide useful information for pre-operative planning, and be a valuable parameter for improving implant design. REFERENCES 1. Clouthier AL, et al. The effect of articular geometry features identified using statistical shape modelling on knee biomechanics. Med Eng Phys 2019; 66: 47–55. 2. Anijs T, et al. Population-based effect of total knee arthroplasty alignment on simulated tibial bone remodeling. J Mech Behav Biomed Mater 2020; 111: 104014. 3. Marra MA, et al. A subject-specific musculoskeletal modeling framework to predict in vivo mechanics of total knee arthroplasty. J Biomech Eng 2015; 137: 020904.
15 mins
Modelling kinematic and kinetic changes around the knee during fatiguing run
Robbert van Middelaar
Abstract: Running is gaining popularity all over the world. However, running is associated with a high incidence of injuries: runners get up to 38 injuries per 1000 hours of running [1]. Neuromuscular fatigue is considered as a risk factor for injuries [2], suggesting that the body in a fatigued state is less able to attenuate impact forces sufficiently while landing on the ground [3]. This could lead to overloading and eventually injuries [3]. The aim of this study is model kinematic and kinetic parameters in and around the knee before and after a fatiguing run. This is done with the help of a musculoskeletal model in the open-source modelling software OpenSim, to gain insight in the shock attenuation mechanism of the knee in a fatigued state. Nine recreational runners (running >10 km per week for at least a year; no injuries in last six months; heel striking pattern and some experience with treadmill running) ran on a treadmill above their average speed of an 8 km race until exhaustion. Kinematics and kinetics were obtained overground before and after the fatigue protocol with Xsens MVN Link Inertial Measurement Units (IMUs), reflective markers of VICON Nexus and using an embedded 3D force plate. Peak breastbone acceleration (PBA) increased in a fatigued state (p = 0.005), indicating a decreased ability to attenuate impact forces while landing on the ground. In addition, a slightly smaller range of motion of the knee during stance and a higher peak net knee moment were observed (p = 0.018), whereas the knee stiffness tended to increase. A higher net knee extension moment at midstance is assumed to decrease knee stability[4] and the body is therefore less able to protect the joint from high loads while landing on the ground. It is therefore assumed that the body shifts away from an active attenuation mechanism (muscular contraction and joint motion) to a more passive mechanism (bone-on-bone, cartilage, ligaments) in a fatigued state, but further research is needed to obtain more knowledge of forces inside the knee.
15 mins
Patient Specific Instrumenation in ACL Reconstruction. A novel technique using 3D printed guides.
Mark Zee, Joep Kraeima, Alain Viddeleer, Ron Diercks
Abstract: Background: In young active patients who have suffered a rupture of the anterior cruciate ligament (ACL), ACL reconstruction is the cornerstone of treatment. Current techniques are designed to reconstruct the ACL in an anatomic position. Non anatomic placement of the ACL graft leads to increased risk of failure of the graft. Failure of reconstruction occurs in 0-14% of primary ACL reconstructions. In up to 54% of cases, technical failure is an additive cause for failure. In 80% of technical failures, malposition of the femoral tunnel is the issue. Current surgical techniques with universal guides leading the direction for tunnels seem to come short in providing a constant and reliable result for creating a femoral tunnel at the individual anatomic origin of the ACL. The need for a patient specific drill guide for femoral tunnel placement seems apparent. Purpose: To determine the in vitro accuracy of a patient specific 3D printed surgical guide, to be used for femoral tunnel positioning in ACL reconstruction. Methods: A patient specific guide for femoral tunnel positioning in ACL reconstruction was created for 4 human cadaveric knee specimens based on both routine clinical MRI and 3D MRI. Molds were created in 100%, 1mm larger and 1 mm smaller than the original. Printing accuracy was assessed. Fitting properties were judged by two orthopaedic surgeons. MRI scanning was performed both pre- and post-procedure. The planned trajectory was compared to the actual drilled trajectory. Results: High printing accuracy was achieved with a deviation of 0.1-0.3 mm (SD 0.12-0.14mm). Molds based on routine clinical MRI with an enlargement of +1mm were judged to fit best. The patient specific 3D printed guide proved to be very accurate with a deviation of 1.5 mm from the intended tunnel location. Conclusions: Usage of a patient specific 3D printed surgical guide for femoral tunnel placement in ACL reconstruction seems promising. Clinical Relevance: Using this novel instrument, femoral tunnel placement in ACL reconstruction may become more accurate and consistent, especially in low volume surgeons.

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