For a proper rehabilitation of the knee following knee arthroplasty, a comprehensive understanding of bony and soft tissue structures and their effects on biomechanics of the individual patient is essential.
Introduction. Fretting corrosion at the taper interface of modular connections can be studied using Finite Element (FE) analyses. However, the loading conditions in FE studies are often simplified, or based on generic activity patterns. Using
Introduction. Total knee replacement (TKR) is an established and effective surgical procedure in case of advanced osteoarthritis. However, the rate of satisfied patients amounts only to about 75 %. One common cause for unsatisfied patients is the anterior knee pain, which is partially caused by an increase in patellofemoral contact force and abnormal patellar kinematics. Since the malpositioning of the tibial and the femoral component affects the interplay in the patellofemoral joint and therefore contributes to anterior knee pain, we conducted a computational study on a cruciate-retaining (CR) TKR and analysed the effect of isolated femoral and tibial component malalignments on patellofemoral dynamics during a squat motion. Methods. To analyse different implant configurations, a
Introduction. Dislocation of total hip replacements (THRs) remains a severe complication after total hip arthroplasty. However, the contribution of influencing factors, such as implant positioning and soft tissue tension, is still not well understood due to the multi-factorial nature of the dislocation process. In order to systematically evaluate influencing factors on THR stability, our novel approach is to extract the anatomical environment of the implant into a
Introduction. Unicompartmental Knee Replacement Arthroplasty (UKA) is a treatment option for early knee OA that appears under-utilised, partly because of a lack of clear guidance on how to best restore lasting knee function using such devices. Computational tools can help consider inherent uncertainty in patient anatomy, implant positioning and loading when predicting the performance of any implant. In the present research an approach for creating patient-specific finite element models (FEM) incorporating joint and muscle loads was developed to assess the response of the underlying bone to UKA implantation. Methods. As a basis for future uncertainty modelling of UKA performance, the geometriesof 173 lower limbs weregenerated from clinical CT scans. These were segmented (ScanIP, Simpleware Ltd, UK) to reconstruct the 3D surfaces of the femur, tibia, patella and fibula. The appropriate UKA prosthesis (DePuy, U.S.) size was automatically selected according to tibial plateau size and virtually positioned (Figure 1). Boolean operations and mesh generation were accomplished with ScanIP. A patient-specific
Introduction. Although total knee arthroplasty (TKA) is generally considered successful, 16–30% of patients are dissatisfied. There are multiple reasons for this, but some of the most frequent reasons for revision are instability and joint stiffness. A possible explanation for this is that the implant alignment is not optimized to ensure joint stability in the individual patient. In this work, we used an artificial neural network (ANN) to learn the relation between a given standard cruciate-retaining (CR) implant position and model-predicted post-operative knee kinematics. The final aim was to find a patient-specific implant alignment that will result in the estimated post-operative knee kinematics closest to the native knee. Methods. We developed subject-specific
Introduction. Recent studies have challenged the concept that a single ‘correct’ alignment to standardised anatomical references is the primary driver of TKA performance with regards to patient satisfaction outcomes. Patient specific variations in musculoskeletal anatomy are one explanation for this. Virtual simulated environments such as rigid body modelling allow for the impact of component alignment and variable patient specific musculoskeletal anatomy to be studied simultaneously. This study aims to determine if the output kinematics derived from consideration of both postoperative component alignment and patient specific
Introduction. Reverse Shoulder Arthroplasty (RSA) improves the mechanics of rotator cuff deficient shoulders. To optimize functional outcomes and minimize failures of the RSA manufacturers have recently made innovative design modifications with lateralized components. However, these innovations have their own set of biomechanical trade-offs, such as increased shear forces along the glenoid bone interface. The objective of this study was to develop an efficient
INTRODUCTION. The burden of Musculoskeletal (M-S) diseases and prosthetic revision operations is huge and increasing rapidly with the aging population. For patients that require a major surgical intervention, procedures are unsafe, uncertain in outcome and have a high complication rate. The goal of this project is to create an ICT-based patient-specific surgical navigation system that helps the surgeon safely reaching the optimal functional result for the patient and is a user friendly training facility for the surgeons. The purpose of this paper is to demonstrate the advancements in personalized
As treatments of knee osteoarthrosis are continually refined, increasingly sophisticated methods of evaluating their biomechanical function are required. Whilst TKA shows good preoperative pain relief and survivorship, functional outcomes are sub-optimal, and research focus has shifted towards their improvement. Restoration of physiological function is a common design goal that relies on clear, detailed descriptions of native biomechanics. Historical simplifications of true biomechanisms, for example sagittal plane approximation of knee kinematics, are becoming progressively less suitable for evaluation of new technologies. The patellar tendon moment arm (PTMA) is an example of such a metric of knee function that usefully informs design of knee arthroplasty but is not fully understood, in part due to limitations in its measurement. This research optimized PTMA measurement and identified the influence of knee size and sex on its variation. The PTMA about the instantaneous helical axis was calculated from optical tracked positional data. A fabricated knee model facilitated calculation optimization, comparing four data smoothing techniques (raw, Butterworth filtering, generalized cross-validated cubic spline-interpolation and combined filtering/interpolation). The PTMA was then measured for 24 fresh-frozen cadaveric knees, under physiologically based loading and extension rates. Sex differences in PTMA were assessed before and after size scaling. Large errors were measured for raw and interpolated-only techniques in the mid-range of extension, whilst both raw and filtered-only methods saw large inaccuracies at terminal extension and flexion. Combined filtering/interpolation enabled sub-mm PTMA calculation accuracy throughout the range of knee flexion, including at terminal extension/flexion (root-mean-squared error 0.2mm, max error 0.5mm) (Figure 1). Before scaling, mean PTMA throughout flexion was 46mm; mean, peak, and minimum PTMA values were larger in males, as was the PTMA at terminal flexion, the change in PTMA from terminal flexion to peak, and the change from peak to terminal extension (mean differences ranging from 5 to 10mm, p<0.05). Knee size was highly correlated with PTMA magnitude (r>0.8, p<0.001) (Figure 2). Scaling eliminated sex differences in PTMA magnitude, but peak PTMA occurred closer to terminal extension in females (female 15°, male 29°, p=0.01) (Figure 3). Improved measurement of the PTMA reveals previously undocumented characteristics that may help to improve the functional outcomes of knee arthroplasty. Knee size accounted for two-thirds of the variation in PTMA magnitude, but not the flexion angle at which peak PTMA occurred, which has implications for morphotype-specific arthroplasty and
Introduction. Experimental testing reproducing activity specific joint-level loading has the potential to quantify structure-function relationships, evaluate intervention possibilities, perform device analysis, and quantify joint kinematics. Many recent technological advancements have been made in this field and inspire this study's aim to present a framework for the application of activity dependent tibiofemoral loading in a specific custom developed 6 degree of freedom (DOF) robotic test frame. This study demonstrates a pipeline wherein kinetic and kinematic data from subjects were collected in a gait lab, analyzed through
Introduction. Gait laboratory measurement of whole-body kinematics and ground reaction forces during a wide range of activities is frequently performed in joint replacement patient diagnosis, monitoring, and rehabilitation programs. These data are commonly processed in
Introduction. Malrotation of the tibial component would lead to various complications after total knee arthroplasty (TKA) such as improper joint kinematics, patellofemoral instability, or excessive wear of polyethylene. However, despite reports of internal rotation of the tibial component being associated with more severe pain or stiffness than external rotation, the biomechanical reasons remain largely unknown. In this study, we used a
INTRODUCTION. The magnitude of principal strain is indicative of the risks of femoral fracture,. 1,2. while changes in femoral strain energy density (SED) after total hip arthroplasty (THA) have been associated with bone remodeling stimulus. 3. Although previous modeling studies have evaluated femoral strains in the intact and implanted femur under walking loads through successfully predicting physiological hip contact force and femoral muscle forces,. 1,2,3. strains during ‘high load’ activities of daily living have not typically been evaluated. Hence, the objective of this study was to compare femoral strain between the intact and the THA implanted femur under peak loads during simulated walking, stair descent, and stumbling. METHODS. CTs of three cadaveric specimens were used to develop finite element (FE) models of intact and implanted femurs. Implanted models included a commercially-available femoral stem (DePuy Synthes, Warsaw, IN, USA). Young's moduli of the composite bony materials were interpolated from Hounsfield units using a CT phantom and established relationships. 4. Peak hip contact force and femoral muscle forces during walking and stair descent were calculated using a lower extremity
Background. Clinical and anatomical complications from total knee replacement (TKR) procedures are debilitating, and include weakness, damage, and the loss of native anatomy. As the annual number of primary TKR surgeries in the United States has continued to rise, to a projected 3.48 million in 2030, there has been a concomitant rise in revision surgery. Damage to or loss of native knee anatomy as a result of TKR revision can leave the patient with irreversible knee dysfunction, which is a contra-indication for most TKR systems on the market. This leaves the multi-revision patient with limited medical options. Complete fusion of the joint, known as arthrodesis, is indicated in some cases. Arthrodesis is also commonly indicated for traumatic injury, bone loss, quadriceps extensor mechanism damage, and osteosarcoma. While this treatment may resolve pain and allow a patient to walk, the inability to flex the knee results in considerable functional complications. Patients with arthrodesis are unable to drive, sit in close-quarter spaces, or engage in a significant number of activities of daily living. Product Statement. The authors have developed and patented the Engage Knee System, a novel TKR system that allows a patient to lock and unlock the knee joint by means of a handheld, non-invasive device. An internal locking mechanism is constructed of materials that have been used in orthopedic joint replacements that have been approved through the FDA 510(k) process. A lightweight, handheld magnetic device is used to actuate the locking mechanism. No percutaneous components are required or present. This device allows a patient to lock their knee joint in full extension to ambulate with the functional equivalence of an arthrodesis, but allows a patient to unlock the device and bend the knee to engage in passive activities that would be otherwise difficult or impossible. The IP portfolio for this technology is owned by Clemson University, and they are seeking a partner/licensee to pursue further technology development and validation. Methods. A literature review of knee arthrodesis incidence and prevalence has been published by the inventors. Three- dimensional gait analysis was used to characterize rigid-knee gait kinematics and kinetics to verify potential implant design loads. Multiple physical prototypes of the design were created and implanted in Sawbones synthetic knee models, and a final prototype using industry-standard arthroplasty materials was contract-manufactured. Results. The Engage system is capable of locking and unlocking in full extension with the use of a non-invasive hand-held device. The device will support the loading patterns and magnitudes during stiff knee gait, as estimated through gait analysis and
Introduction. Many finite element (FE) studies have been performed in the past to assess the biomechanical performance of TKA and THA components. The boundary conditions have often been simplified to a few peak loads. With the availability of personalized
Component alignment cannot fully explain total knee arthroplasty [TKA] performance with regards to patient reported outcomes and pain. Patient specific variations in musculoskeletal anatomy are one explanation for this. Computational simulations allow for the impact of component alignment and variable patient specific musculoskeletal anatomy on dynamics to be studied across populations. This study aims to determine if simulated dynamics correlate with Patient Reported Outcomes. Landmarking of key anatomical points and 3D registration of implants was performed on 96 segmented post-operative CT scans of TKAs. A cadaver rig validated platform for generating patient specific rigid body
Background. Though many advantages of reverse total shoulder arthroplasty (RTSA) have been demonstrated, a variety of complications indicate there is much to learn about how RTSA modifies normal shoulder function. This study assesses how RTSA affects deltoid muscle moment arms post-surgery using a subject-specific computational model driven by in vivo kinematic data. Methods. A subject-specific 12 degree-of-freedom (DOF)
Introduction. A deep squat (DS) is a challenging motion at the level of the hip joint generating substantial reaction forces (HJRF). As a closed chain exercise, it has great value in rehabilitation and muscle strengthening of hip and knee. During DS, the hip flexion angle approximates the functional range of hip motion risking femoroacetabular impingement in some morphologies. In-vivo HJRF measurements have been limited to instrumented implants in a limited number of older patients performing incomplete squats (< 50° hip flexion and < 80° knee flexion). On the other hand, total hip arthroplasty is being increasingly performed in a younger and higher demanding patient population. These patients clearly have a different kinetical profile with hip and knee flexion ranges going well over 100 degrees. Since measurements of HJRF with instrumented prostheses in healthy subjects would be ethically unfeasible, this study aims to report a personalised numerical solution based on inverse dynamics to calculate realistic in-silico HJRF values during DS. Material and methods. Thirty-five healthy males (18–25 years old) were prospectively recruited for motion and morphological analysis. DS motion capture (MoCap) acquisitions and MRI scans with gait lab marker positions were obtained. The AnyBody Modelling System (v6.1.1) was used to implement a novel personalisation workflow of the AnyMoCap template model. Bone geometries, semi-automatically segmented from MRI, and corresponding markers were incorporated into the template human model by an automated procedure. A state of-the-art TLEM 2.0 dataset, included in the Anybody Managed Model Repository (v2.0), was used in the template model. The subject-specific MoCap trials were processed to compute kinematics of DS, muscle and joint reaction forces in the entire body. Resulting hip joint loads were compared with in-vivo data from OrthoLoad dataset. Additionally, hip and knee joint angles were computed. Results. An average HJRF of 274%BW (251.5 – 297.9%BW; 95% confidence interval) was calculated at the peak of DS. The HJRF on the pelvis was directed superior, medial and posterior throughout the DS. Peak knee and hip flexion angles were 112° (108.1° – 116.5°) and 107° (104.6° – 109.4°) on average. Discussion and conclusions. A comprehensive approach to construct an accurate personalised