Dennis Janssen

• Radboud University Medical Centre (Radboudumc)

Purpose Lateral patellofemoral ligament (LPFL) reconstruction addresses medial patellar instability, but uncertainty regarding the optimal femoral attachment site may affect isometry and increase complication rates. This study aimed to establish landmarks for the femoral attachment of the LPFL graft based on in vivo isometry during active knee exte...

Polyetheretherketone (PEEK) is of interest as implant material for cementless tibial total knee arthroplasty (TKA) components due to its potential advantages. One main advantage is that the stiffness of PEEK closely resembles the stiffness of bone, potentially avoiding peri-prosthetic stress-shielding. When introducing a new implant material for ce...

Background Medial patellofemoral ligament (MPFL) reconstruction is associated with high complication rates because of graft overloading from incorrect graft positioning. To improve clinical outcomes, it is crucial to gain a better understanding of MPFL elongation patterns. Purpose To assess MPFL length changes in healthy knees from 0° to 90° of dy...

For biomechanical simulations of orthopaedic interventions, it is imperative to implement a material model that can realistically reproduce the nonlinear behavior of the bone structure. However, a proper material model that adequately combines the trabecular and cortical bone response is not yet widely identified. The current paper aims to investig...

The objectives of the 1st EFORT European Consensus on ‘Medical and Scientific Research Requirements for the Clinical Introduction of Artificial Joint Arthroplasty Devices’ were foremost to focus on patient safety by establishing performance requirements for medical devices. The 1st EFORT European Consensus applied an a priori-defined, modified Delp...

The effect of long-term peri-prosthetic bone loss on the process of aseptic loosening of tibial total knee arthroplasty (TKA) is subject to debate. Contradicting studies can be found in literature, reporting either bone resorption or bone formation prior to failure of the tibial tray. The aim of the current study was to investigate the effects of b...

Research Topic 16

Background Accurate assessment of knee kinematics is important in the diagnosis and quantification of knee disorders and to determine the effect of orthopaedic interventions. Despite previous studies showing the usefulness of dynamic imaging and providing valuable insights in knee kinematics, dynamic imaging is not widely used in clinics due to a v...

Background: Participants in Sierra Leone received a Fused Filament Fabrication (FFF)-printed transtibial prosthetic socket. Follow-up was conducted on this group over a period of 21 months. To investigate the failure of some of the FFF-printed transtibial sockets, further strength investigation is desired. Methods: A finite element (FE) analysis pr...

The use of a more compliant material, such as polyetheretherketone (PEEK), for a cementless femoral component is a potential solution to prevent aseptic loosening caused by peri-prosthetic stress-shielding. Long-term fixation of a cementless femoral component is achieved by a proper primary fixation of the bone-implant interface, which is influence...

Accurate assessment of knee kinematics is important to investigate knee pathology and the effect of orthopaedic interventions. Anatomical coordinate systems are used to describe knee kinematics but inherently show interpersonal differences. The purpose of this study was to determine the sensitivity of an anatomical coordinate system of the knee to...

Cementless total knee arthroplasty (TKA) components have rough and porous surface coatings which can enhance bone ingrowth and stability at the bone-implant. To achieve primary stability in the postoperative period where no apposition is formed, the resistance against motions between bone and implant is optimized by increasing the friction at the i...

Sufficient primary stability through interference fit is required for bone ingrowth and subsequent long-term fixation of cementless knee replacement implants, and can be evaluated in experimental testing. In this study, primary stability of a novel posterior-stabilized (PS) femoral component (Attune PS) and a contemporary PS component (Triathlon PS...

Malignant bone tumors are usually treated by resection of tumor tissue followed by filling of the bone defect with bone graft substitutes. Polymethylmethacrylate (PMMA) cement is the most commonly used bone substitute in clinical orthopedics in view of its reliability. However, the dense nature of PMMA renders this biomaterial unsuitable for local...

Periprosthetic bone loss is an important factor in tibial implant failure mechanisms in total knee arthroplasty (TKA). The purpose of this study was to validate computational postoperative bone response using longitudinal clinical DEXA densities. Computational remodeling outcome over a population was obtained by incorporating the strain-adaptive re...

Finite element (FE) simulations can be used to evaluate the mechanical behavior of human bone and allow for quantitative prediction of press-fit implant fixation. An adequate material model that captures post-yield behavior is essential for a realistic simulation. The crushable foam (CF) model is a constitutive model that has recently been proposed...

Long-term implant failure in the form of aseptic loosening and periprosthetic fracture is the most common cause of revision procedures in total knee arthroplasty (TKA). While early loosening can often be attributed to failure of primary fixation, late implant failure could be associated with loss of fixation secondary to bone resorption, as a resul...

Cementless total knee arthroplasty (TKA) implants rely on interference fit to achieve initial stability. However, the optimal interference fit is unknown. This study investigates the effect of using different interference fit on the initial stability of tibial TKA implants. Experiments were performed on human cadaveric tibias using a low interferen...

Due to their high stiffness, metal femoral implants in total knee arthroplasty may cause stress shielding of the peri-prosthetic bone, which can lead to loss of bone stock. Using a polymer (PEEK) femoral implant reduces the stiffness mismatch between implant and bone, and therefore has the potential to decrease strain shielding. The goal of the cur...

Cementless femoral total knee arthroplasty (TKA) components use a press-fit (referred to as interference fit) to achieve initial fixation. A higher interference fit could lead to a superior fixation, but it could also introduce more damage to the bone during implantation. The purpose of the current study was to investigate the effect of interferenc...

The fixation of press-fit orthopaedic devices depends on the mechanical properties of the bone that is in contact with the implants. During the press-fit implantation, bone is compacted and permanently deformed, finally resulting in the mechanical interlock between implant and bone. For the development and design of new devices, it is imperative to...

Periprosthetic bone loss is an important factor in tibial implant failure mechanisms in total knee arthroplasty (TKA). The purpose of this study was to determine the effect of postoperative knee alignment and population variation on tibial bone remodeling, to assess long-term stability of a knee replacement. Strain-adaptive finite element (FE) remo...

Despite all the efforts to optimize the meniscus prosthesis system (geometry, material, and fixation type), the success of the prosthesis in clinical practice will depend on surgical factors such as intra-operative positioning of the prosthesis. In this study, the aim was therefore to assess the implications of positional changes of the medial meni...

Background: In ACL-reconstructed patients the postoperative knee biomechanics may differ from the intact knee biomechanical behavior which can alter knee kinematics and kinetics, and as a result lead to the progression of knee osteoarthritis. The aim of this study was to demonstrate the potential of finite element models to define the optimal choi...

Fretting and corrosion at the taper-head interface in total hip arthroplasty has been reported as a potential cause of early failure of the implant system. The finite element (FE) method can be used to study the mechanics at the taper junction that are difficult to assess experimentally. Taper mismatch is one of the factors that can influence the p...

Primary press-fit fixation of femoral knee prostheses is obtained thanks to the inside dimensions of the implant being undersized with respect to the bone cuts created intra-operatively, dictated by a press-fit specified by the implant design. However, during prostheses press-fit implantation, high compressive and shear stresses at the implant-bone...

Characterization of the main tibiofemoral ligaments is an essential step in developing patient-specific computational models of the knee joint for personalized surgery pre-planning. Tensile tests are commonly performed in-vitro to characterize the mechanical stiffness and rupture force of the knee ligaments which makes the technique unsuitable for...

INTRODUCTION During prostheses press-fit implantation, high compressive and shear stresses at the implant-bone interface are generated. Permanent bone damage occurs [1], but the extent remains unknown. The aim of this study is to quantify, using high-resolution peripheral quantitative computed tomography (HR-pQCT) and Digital Volume Correlation (DV...

Current finite element (FE) models predicting failure behavior comprise single vertebrae, thereby neglecting the role of the posterior elements and intervertebral discs. Therefore, this study aimed to develop a more clinically relevant, case‐specific non‐linear FE model of two functional spinal units able to predict failure behavior in terms of a)...

Purpose: When downsizing the femoral component to prevent mediolateral overhang, notching of the anterior femoral cortex may occur, which could be solved by flexing the femoral component. In this study, we investigated the effect of flexion of the femoral component on patellar tendon moment arm, patellofemoral forces and kinematics in posterior-re...

Background: Some studies have revealed an increased risk of early aseptic loosening of cementless stems in THA when inserted through an anterior or anterolateral approach compared with a posterior approach, whereas approach does not appear to be a risk factor in others. Stem design, whether "anatomic" (that is, stems with a curved lateral profile...

In finite element models of the either implanted or intact human knee joint, soft tissue structures like tendons and ligaments are being incorporated, but usually skin, peripheral knee soft tissues, and the posterior capsule are ignored and assumed to be of minor influence on knee joint biomechanics. It is, however, unknown how these peripheral str...

Background Conventional total knee replacement designs show high success rates but in the long term, the stiff metal components may affect bone quality of the distal femur. In this study we introduce an all-polymer total knee replacement device containing a PEEK femoral component on an UHMWPE tibial implant and study its mechanical integrity, fixat...

We propose an experimental setup and protocol able to induce targeted failure of the middle vertebra in 3-segment spinal units and to capture the specimens’ deformation in their post-failure state. Sixteen 3-segment spinal units with and without artificial metastases were destructively tested in axial compression using one of two failure criteria;...

The aim of this study was to introduce a novel method to provide the knee surgeon with the patient-specific ACL reconstruction optimal surgical variables, prior to the surgery, and based on the surgeon's graft type preference. Based on MRI and CT a detailed computational Finite Element (FE) model of cadaveric human intact knee joints was developed...

The current study was designed to investigate the mechanical response of a polyetheretherketone-on-polyethylene total knee replacement device during a deep squat. Application of this high-demand loading condition can identify weaknesses of the polyetheretherketone relative to cobalt-chromium. This study investigated whether the implant is strong en...

Anterior cruciate ligament (ACL) injuries are among the most common knee injuries, which makes the following ACL reconstruction surgery one of the most performed orthopedic surgeries. Arthroscopic single bundle hamstring reconstruction is of interest for many orthopedic surgeons for many years, where some others believe implementing double bundle r...

Background: The purpose of this study was to compare the mechanical stability of a relatively thin locking plate (FlexitSystem implant) with a relatively firm locking plate (TomoFix implant), both used for opening wedge high tibial osteotomy. Methods: Seven fresh frozen paired human cadaveric tibiae were used. The opening wedge high tibial osteo...

The use of modular components in total hip arthroplasty introduced an additional interface with the potential for fretting and corrosion to occur. Fretting and corrosion at this interface have been reported as a potential cause of early failure of the implant system. Using finite element (FE) analyses the mechanics at the taper junction can be stud...

Background: During implantation of an uncemented femoral knee implant, press-fit interference fit provides the primary stability. It is assumed that during implantation a combination of elastic and plastic deformation and abrasion of the bone will occur, but little is known about what happens at the bone-implant interface and how much press-fit in...

In finite element (FE) models knee ligaments can represented either by a group of one-dimensional springs, or by three-dimensional continuum elements based on segmentations. Continuum models closer approximate the anatomy, and facilitate ligament wrapping, while spring models are computationally less expensive. The mechanical properties of ligament...

Stress shielding-related bone loss occurs after total hip arthroplasty because the stiffness of metallic implants differs from that of the host femur. Although reducing stem stiffness can ameliorate the bone resorption, it increases stress at the bone-implant interface and can inhibit fixation. To overcome this complication, a novel cementless stem...

Introduction Introducing polyetheretherketone (PEEK) polymer as a material for femoral components in total knee arthroplasty (TKA) could potentially lead to a reduction of the cemented fixation strength. A PEEK implant is more likely to deform under high loads, rendering geometrical locking features less effective. Fixation strength may be enhanced...

To achieve long-lasting fixation of cementless implants, an adequate primary stability is required. We aimed to compare primary stability of a new cementless femoral knee component (Attune®) against a conventional implant (LCS®) under different loading conditions. Six pairs of femora were prepared following the normal surgical procedure. Calibrated...

It is essential to calculate micromotions at the bone-implant interface of an uncemented femoral total knee replacement (TKR) using a reliable computational model. In the current study, experimental measurements of micromotions were compared with predicted micromotions by Finite Element Analysis (FEA) using two bone material models: linear elastic...

Fretting corrosion at the taper interface of modular hip implants has been implicated as a possible cause of implant failure. This study was set up to gain more insight in the taper mechanics that lead to fretting corrosion. The objectives of this study therefore were (1) to select experimental loading conditions to reproduce clinically relevant fr...

4th annual Academic Poster Showcase at Global SIMULIA User Conference

Purpose: In total knee arthroplasty (TKA), the posterior tibial slope is not always reconstructed correctly, and the knee ligaments may become too tight in flexion. To release a tight flexion gap, surgeons can increase the posterior tibial slope using two surgical resection techniques: the anterior tibial cortex (ACR) or the centre of tibial plate...

Knowing the forces in the human body is of great clinical interest and musculoskeletal models are the most commonly used tool to estimate them in vivo. Unfortunately, the process of computing muscle, joint contact and ligament forces simultaneously is computationally highly demanding. The goal of this study was to develop a fast surrogate model of...

INTRODUCTION: Tibial slope can affect the outcomes of Total Knee Arthroplasty (TKA). More posterior slope potentially helps releasing a too tight flexion gap and it is generally associated with a wider range of post-operative knee flexion. However, the mechanism by which tibial slope affects the function of TKA during dynamic activities of daily li...

INTRODUCTION: Increasing the amount of posterior tibial slope in Total Knee Arthroplasty (TKA) was suggested as a manner to release a tight flexion gap. However, an excessive tibial slope could jeopardize the knee stability in flexion. The effects of varying tibial slope on the amount of laxity of the knee joint remain unclear. The aim of this stud...

Purpose: The objective of this study was to investigate the effect of a medial open-wedge osteotomy (OWO) and the release of the superficial medial collateral ligament (MCL) on the tibiofemoral cartilage pressure, the MCL tension and the valgus laxity of the knee. Methods: Seven fresh-frozen, human cadaveric knees were used. Medial and lateral m...

Post-operative changes in trabecular bone morphology at the cement-bone interface can vary depending on time in service. This study aims to investigate how micromotion and bone strains change at the tibial bone-cement interface before and after cementation. This work discusses whether the morphology of the post-mortem interface can be explained by...

Isocyanate-terminated adhesive amphiphilic block copolymers are attractive materials to treat meniscus tears due to their tuneable mechanical properties and good adhesive characteristics. However, a drawback of this class of materials is their relatively long curing time. In this study, we evaluate the use of an amine cross-linker and addition of c...

Aseptic loosening of the tibial component remains the leading cause for revision surgery in total knee arthroplasty (TKA). Understanding the mechanisms leading to loss of fixation can offer insight into preventative measures to ensure a longer survival rate. In cemented TKA, loosening occurs at the cement-trabecular interface probably due to a stre...

Introduction: Tibial slope was shown to majorly affect the outcomes of Total Knee Arthroplasty (TKA). More slope of the tibial component could help releasing a too tight flexion gap in cruciate-retaining (CR) TKA and is generally associated with a wider range of post-operative knee flexion. However, an excessive tibial slope could jeopardize the kn...

PurposeThe purpose of this study was to investigate stability and strain distribution of a tibial plateau reconstruction with a trabecular metal cone while the tibial component is implanted with and without a stem, and whether prosthetic stability was influenced by bone mineral density. Trabecular metal cones are designed to fill up major bone defe...

The finite element (FE) method has been widely used to investigate knee biomechanics. Time integration algorithms for dynamic problems in finite element analysis can be classified as either implicit or explicit. Although previously both static/dynamic implicit and dynamic explicit method have been used, a comparative study on the outcomes of both m...

Aseptic loosening of the tibial component in cemented total knee arthroplasty remains a major concern. We hypothesize that micromotion between the cement and trabeculae leads to increased circulation of interstitial fluid which in turn causes fluid-induced resorption of the trabeculae. Another mechanism for implant loosening is trabecular strain sh...

INTRODUCTION: Simultaneous prediction of body-level dynamics and detailed joint mechanics in the frame of musculoskeletal (MS) modeling represents still a highly computationally demanding task. Marra et al. (2014) recently presented and validated a MS model capable of concurrent prediction of muscle forces, knee ligament forces, tibiofemoral (TF) a...

INTRODUCTION: One of the main goals in Total Knee Arthroplasty (TKA) is to restore natural knee kinematics and physiological loads in tibiofemoral (TF) and patellofemoral (PF) joint. The extent to which this is achieved may differ substantially, depending on many factors. Adding extra flexion of the femoral component (FFC) in the sagittal plane dur...

The modular taper junction in total hip replacements has been implicated as a possible source of wear. The finite element method can be used to study the wear potential at the taper junction. For such simulations it is important to utilize and representative contact parameters, in order to achieve accurate results. One of the main parameters in fin...

In this study the in-situ tensile behavior and slackness of the anterior cruciate ligament (ACL) was evaluated at various knee flexion angles. In four cadaveric knees the ACL was released at the tibial insertion, after which it was re-connected to a tensiometer. After pre-tensioning (10 N) the ACL in full-extension, the knee was flexed from 0° to 1...

The initial fixation of cemented Total Knee Replacements (TKRs) relies on mechanical interlock between cement and bone, but loss of interlock occurs with in vivo service. In this study, cement-trabeculae gap morphology and micromechanics were measured for lab prepared (representing post-operative state) and postmortem retrieval (with in vivo remode...