No differences in functional and clinical outcomes after rehabilitation between modified kinematic and mechanical alignment in total knee arthroplasty: A randomized controlled trial.

Purpose: Despite advancements in total knee arthroplasty (TKA), patient dissatisfaction remains notably high (15%-25%). This dissatisfaction will be multifactorial, one of which may be the alignment of the components. Kinematic alignment (KA), aimed at restoring pre-arthritic knee anatomy, is proposed as a promising alternative to mechanical alignment (MA), potentially offering better functional outcomes and improved gait characteristics.

[Update 2025: Biomechanics and kinematics after total knee arthroplasty (TKA)].

Background: In order to optimise clinical outcomes after primary total knee arthroplasty (TKA), research has refocused on the knee joint's biomechanical characteristics. Beyond implant design and alignment philosophy, the restoration of natural joint kinematics, functional range of motion, and stability critically depends on patient-specific anatomical conditions.

Biomechanics: Instrumented TKA systems have demonstrated the significance of coronal alignment and mediolateral load distribution.

Are current total knee arthroplasty implants tested and approved for personalised alignment?

Purpose: Total knee arthroplasty (TKA) traditionally aims for neutral mechanical alignment (MA) to ensure implant longevity. However, this approach ignores individual knee variations, potentially leading to soft-tissue imbalances and suboptimal functional outcomes. As an alternative, personalised alignment techniques (PAT) have emerged that aim to restore bony anatomy, potentially improve soft tissue balance and thus accelerate recovery.

A rig for in vitro testing of the lumbar spine and pelvis simulating posterior, anterior and oblique trunk muscles.

Numerous research questions require in vitro testing on lumbar spine and pelvis specimens. The majority of test setups apply forces and torques via the uppermost vertebral body with the lowermost vertebral body fixed and have been validated for kinematics and intradiscal pressure. Models without simulation of muscle traction may produce valid data only for testing conditions for which they have been validated.

Improved quadriceps efficiency with a medial pivot in comparison to a cruciate-retaining design in total knee arthroplasty.

Purpose: The posterior cruciate-retaining (CR) design offers rotational freedom but risks abnormal kinematics and instability. The medial pivot (MP) design mimics native joint motion with a high-conformity medial and flat lateral interface. Within clinical studies, the MP design outclassed the CR design, but biomechanical studies are lacking.

Reverse Shoulder Arthroplasty Baseplate Stability Is Affected by Bone Density and the Type and Amount of Augmentation.

Objective: This study evaluated the effects of bony increased offset (BIO) and metallic augments (MAs) on primary reverse shoulder arthroplasty (RSA) baseplate stability in cadaveric specimens with variable bone densities.

Methods: Thirty cadaveric specimens were analyzed in an imaging and biomechanical investigation. Computed tomography (CT) scans allowed for preoperative RSA planning and bone density analysis.

A reproducible representation of healthy tibiofemoral kinematics during stair descent using REFRAME - part I: REFRAME foundations and validation.

In clinical movement biomechanics, kinematic measurements are collected to characterise the motion of articulating joints and investigate how different factors influence movement patterns. Representative time-series signals are calculated to encapsulate (complex and multidimensional) kinematic datasets succinctly. Exacerbated by numerous difficulties to consistently define joint coordinate frames, the influence of local frame orientation and position on the characteristics of the resultant kinematic signals has been previously proven to be a major limitation.

Conceptual foundations of a REFRAME-based approach to discriminate across total knee implant designs based on the positions of functional centres of rotation.

In modern knee arthroplasty, surgeons increasingly aim for individualised implant selection based on data-driven decisions to improve patient satisfaction rates. The identification of an implant design that optimally fits to a patient's native kinematic patterns and functional requirements could provide a basis towards subject-specific phenotyping. The goal of this study was to achieve a first step towards identifying easily accessible and intuitive features that allow for discrimination between implant designs based on kinematic data.

Volumetric Humeral Canal Fill Ratio Effects Primary Stability and Cortical Bone Loading in Short and Standard Stem Reverse Shoulder Arthroplasty: A Biomechanical and Computational Study.

Objective: This study evaluated the effect of three-dimensional (3D) volumetric humeral canal fill ratios (VFR) of reverse shoulder arthroplasty (RSA) short and standard stems on biomechanical stability and bone deformations in the proximal humerus.

Methods: Forty cadaveric shoulder specimens were analyzed in a clinical computed tomography (CT) scanner allowing for segmentation of the humeral canal to calculate volumetric measures which were verified postoperatively with plain radiographs. Virtual implant positioning allowed for group assignment (VFR < 0.

The Influence of Kinematic Alignment on Patellofemoral Joint Biomechanics in Total Knee Arthroplasty.

: Anterior knee pain is a prevalent issue post total knee arthroplasty, often necessitating revision surgery. Various factors contribute to this complication, including patellar maltracking and excessive patellofemoral load. Kinematic alignment has emerged as an alternative, showing promising outcomes in clinical studies.

Comparison of Biological Augmentation in Rotator Cuff Repair Using Inflamed Versus Noninflamed Bursal Tissue in Rats.

Purpose: To examine how augmentation of a rotator cuff repair with inflamed versus noninflamed bursal tissue affects tendon-to-bone healing in a rat model of rotator cuff repair.

Methods: A total of 136 Sprague-Dawley rats were randomly assigned to an inflamed or noninflamed bursal tissue application group. After detachment, the supraspinatus tendon was reattached with bursal tissue sewn onto the tendon-to-bone interface.

Validation of Inertial-Measurement-Unit-Based Ex Vivo Knee Kinematics during a Loaded Squat before and after Reference-Frame-Orientation Optimisation.

Recently, inertial measurement units have been gaining popularity as a potential alternative to optical motion capture systems in the analysis of joint kinematics. In a previous study, the accuracy of knee joint angles calculated from inertial data and an extended Kalman filter and smoother algorithm was tested using ground truth data originating from a joint simulator guided by fluoroscopy-based signals. Although high levels of accuracy were achieved, the experimental setup leveraged multiple iterations of the same movement pattern and an absence of soft tissue artefacts.

[Numerical simulation in musculoskeletal biomechanics : Application perspectives and possibilities].

Background: Computational research methods, such as finite element analysis (FEA) and musculoskeletal multi-body simulation (MBS), are important in musculoskeletal biomechanics because they enable a better understanding of the mechanics of the musculoskeletal system, as well as the development and evaluation of orthopaedic implants. These methods are used to analyze clinically relevant issues in various anatomical regions, such as the hip, knee, shoulder joints and spine. Preoperative simulation can improve surgical planning in orthopaedics and predict individual results.

The effect of a collar on primary stability of standard and undersized cementless hip stems: a biomechanical study.

Introduction: Aseptic loosening and periprosthetic fractures are main reasons for revision after THA. Quite different from most other stem systems, Corail cementless hip stems show better survival rates than their cemented counterpart, which can possibly be explained by the use of a collar. The study aimed to investigate primary stability with standard and undersized hip stems both collared and collarless.

Uncemented hip revision cup as an alternative for T-type acetabular fractures: A cadaveric study.

Background: The current rise in elderly patients with compromised bone quality complicates the surgical treatment of acetabular T-type fractures (AO type 62B2 fractures). There is on ongoing discussion about the treatment options, mostly consisting of an open reduction and internal fixation (ORIF) with or without primary or secondary total hip arthroplasty (THA). Yet, these patients are oftentimes unable to fulfil weight-bearing restrictions and mostly present with an unavailability of a stable anchor site.

A frame orientation optimisation method for consistent interpretation of kinematic signals.

In clinical movement biomechanics, kinematic data are often depicted as waveforms (i.e. signals), characterising the motion of articulating joints.

Strain evaluation of axially loaded collateral ligaments: a comparison of digital image correlation and strain gauges.

The response of soft tissue to loading can be obtained by strain assessment. Typically, strain can be measured using electrical resistance with strain gauges (SG), or optical sensors based on the digital image correlation (DIC), among others. These sensor systems are already established in other areas of technology.

Does Posterior Tibial Slope Influence Knee Kinematics in Medial Stabilized TKA?

Background: During total knee arthroplasty (TKA), one of the key alignment factors to pay attention to is the posterior tibial slope (PTS). The PTS clearly influences the kinematics of the knee joint but must be adapted to the coupling degree of the specific TKA design. So far, there is hardly any literature including clear recommendations for how surgeons should choose the PTS in a medial stabilized (MS) TKA.

Resistance Training Combined with Balance or Gait Training for Patients with Parkinson's Disease: A Randomized Controlled Pilot Study.

Background: Gait and balance disorders in patients with idiopathic Parkinson's disease (PD) lead to major mobility limitations. To counteract this, physical therapy such as gait, balance, or resistance training is applied. Integrative training methods, which combine these elements, could be particularly effective.

Biomechanical comparison of screw vs. cerclage refixation in orthogeriatric lesser trochanteric fractures: a cadaveric study.

Purpose: Osteoporosis-related proximal femur fractures continue to increase significantly due to demographic change. This study was designed to evaluate the biomechanical stability of two different fixation methods (cerclage vs. screw) for refixation of a trochanter minor fragment in the pertrochanteric fractures in cadaveric bones.

Toward A Regulatory Pathway for the Use of in Silico Trials in the CE Marking of Medical Devices.

In Silico Trials methodologies will play a growing and fundamental role in the development and de-risking of new medical devices in the future. While the regulatory pathway for Digital Patient and Personal Health Forecasting solutions is clear, it is more complex for In Silico Trials solutions, and therefore deserves a deeper analysis. In this position paper, we investigate the current state of the art towards the regulatory system for in silico trials applied to medical devices while exploring the European regulatory system toward this topic.

Isolated effects of patellar resurfacing in total knee arthroplasty and their relation to native patellar geometry.

The isolated effects of patellar resurfacing on patellar kinematics are rarely investigated. Nonetheless, knowing more about these effects could help to enhance present understanding of the emergence of kinematic improvements or deteriorations associated with patellar resurfacing. The aim of this study was to isolate the effects of patellar resurfacing from a multi-stage in vitro study, where kinematics after total knee arthroplasty before and after patellar resurfacing were recorded.

Influence of Treadmill Design on Gait: Does Treadmill Size Affect Muscle Activation Amplitude? A Musculoskeletal Calculation With Individualized Input Parameters of Gait Analysis.

With increasing age, gait changes often occur, leading to mobility problems and thus a higher risk of falling. Interest in training at home or at retirement homes has led to the development of "mobile treadmills." A difference in treadmill surface length may influence walking parameters (i.

Biomechanical stability of short versus long proximal femoral nails in osteoporotic subtrochanteric A3 reverse-oblique femoral fractures: a cadaveric study.

Purpose: Due to the demographic change towards an older society, osteoporosis-related proximal femur fractures are steadily increasing. Intramedullary nail osteosyntheses are available in different lengths, where the field of application overlaps. The aim of this study was to investigate whether subtrochanteric fractures can also be treated stably using a short femoral intramedullary nail in cadaveric bones.