Biomechanical analysis of patient specific cone vs conventional stem in revision total knee arthroplasty.

Background: In revision total knee arthroplasty, addressing significant bone loss often involves the use of cemented or press-fit stems to ensure implant stability and long-term fixation. A possible alternative to stem was recently introduced utilizing custom-made porous metaphyseal cones, designed to reconstruct the missing tibial and femoral geometries. Early clinical and radiological assessments have shown promising results.

Biomechanical analysis of different levels of constraint in TKA during daily activities.

Background: Numerous total knee prosthetic implants are currently available on the orthopedic market, and this variety covers a set of different levels of constraint: among the various models available, a significant role is covered by mobile bearing cruciate-retaining design with an ultra-congruent insert, mobile bearing cruciate-retaining design, fixed-bearing posterior stabilized prosthesis and fixed-bearing constrained condylar knee. A biomechanical comparative study among them could therefore be helpful for the clinical decision-making process. This study aimed to compare the effect of these different levels of constraint in the knee biomechanics of a patient, in three different configurations representing the typical boundary conditions experienced by the knee joint during daily activities.

Biomechanical Analysis of the Use of Stems in Revision Total Knee Arthroplasty.

Adequate fixation is fundamental in revision total knee arthroplasty; consequently, surgeons must determine the correct set-up for each patient, choosing from numerous stem solutions. Several designs are currently available on the market, but there are no evidence-based quantitative biomechanical guideline yet. Therefore, several stems were designed and analyzed using a previously-validated finite-element model.

Three-dimensional analysis of the gap space under forearm casts.

Purpose: Secondary displacement represents a frequent complication of conservative treatment of fractures, particularly of the distal radius. The gap space between skin and cast may lead to a certain degree movements and this increased mobility might favor redisplacement. The aim of this study was to develop a new 3D method, to measure the gap space in all 3 geometrical planes, and to validate this new technique in a clinical setting of distal radius fractures.

Use of porous custom-made cones for meta-diaphyseal bone defects reconstruction in knee revision surgery: a clinical and biomechanical analysis.

Introduction: Although the practice of metaphyseal reconstruction has obtained successful clinical and radiological results in revision total knee surgery, off-the-shelf devices aren't an effective solution for all patients as they do not cover the full range of clinical possibilities. For this reason, during severe knee revisions, custom-made porous titanium cementless metaphyseal cones are nowadays employed as alternative to traditional surgeries. The aim of this study is to understand the benefits gained by the use of the custom-made cones against the performance of more traditional techniques, such as the use of cemented or cementless stems.

Analysis of Biomechanical Differences Between Condylar Constrained Knee and Rotating Hinged Implants: A Numerical Study.

Background: Different levels of constraint for total knee arthroplasty can be considered for revision surgeries. While prior studies have assessed the clinical impact and patient outcomes of condylar constrained knee (CCK) and rotating hinged (RTH) implants, nowadays little is known about the biomechanical effects induced by different levels of constraint on bone stress and implant micromotions.

Methods: CCK and RTH implant models were analyzed using a previously validated numerical model.

Inter-rater reliability and variability of ultrasound measurements of abdominal muscles and fasciae thickness.

Ultrasound (US) imaging is being increasingly used by Physical and Rehabilitation Medicine (PRM) specialists to measure the thickness of abdominal muscles. The current study set out to assess the inter-rater reliability of US measurements of the thickness of the abdominal muscles/fasciae. Three raters (1 = orthopedic specialist, expert on fasciae; 2 = PRM resident; 3 = PRM specialist) with different levels of US training examined the abdominal muscles and fasciae of a healthy volunteer under supine resting and dynamic conditions following a standard US protocol.

3D surface imaging of abdominal wall muscular contraction.

Background And Objective: The biomechanical analysis of the abdominal wall should take into account muscle activation and related phenomena, such as intra-abdominal pressure variation and abdomen surface deformation. The geometry of abdominal surface and its deformation during contraction have not been extensively characterized, while represent a key issue to be investigated.

Methods: In this work, the antero-lateral abdominal wall surface of ten healthy volunteers in supine position is acquired via laser scanning in relaxed conditions and during abdominal muscles contraction, repeating each acquisition six times.

The effects of the muscular contraction on the abdominal biomechanics: a numerical investigation.

Abdominal wall biomechanics is strongly affected by muscular contraction and intra-abdominal pressure (IAP) which characterize different physiological functions and daily tasks. However, the active muscular behavior is generally not considered in current computational models of the abdominal wall. The aim of this study is to develop a numerical model mimicking muscular activation and IAP.

Lessons learned from 227 biological meshes used for the surgical treatment of ventral abdominal defects.

Purpose: The advantages of biological meshes for ventral hernia repair are still under debate. Given the high financial cost, the proper indications for biological meshes should be clarified to restrict their use to properly selected patients.

Methods: A retrospective database was instituted to register all cases of abdominal wall defect treated with biological meshes from 1/2010 to 3/2016.

Asymmetric polyethylene inserts promote favorable kinematics and better clinical outcome compared to symmetric inserts in a mobile bearing total knee arthroplasty.

Purpose: This study aims at comparing the effects of symmetric and asymmetric designs for the polyethylene insert currently available and also for mobile bearing total knee arthroplasty (TKA). The investigation was performed both clinically and biomechanically through finite element analysis.

Methods: 303 patients, with a mobile bearing TKA, were analyzed retrospectively.

Biomechanical Analysis of Augments in Revision Total Knee Arthroplasty.

Augments are a common solution for treating bone loss in revision total knee arthroplasty (TKA) and industry is providing to surgeons several options, in terms of material, thickness, and shapes. Actually, while the choice of the shape and the thickness is mainly dictated by the bone defect, no proper guidelines are currently available to select the optimal material for a specific clinical situation. Nevertheless, different materials could induce different bone responses and, later, potentially compromise implant stability and performances.

Sensitivity analysis of the material properties of different soft-tissues: implications for a subject-specific knee arthroplasty.

Introduction: While developing a subject-specific knee model, different kinds of data-inputs are required. If information about geometries can be definitely obtained from images, more effort is necessary for the properties. Consequently, such information are recruited from the literature as common habit.

Automatic characterization of soft tissues material properties during mechanical tests.

Introduction: The estimation of the non-linear viscoelastic characteristics of human soft tissues, such as ligaments and tendon, is often affected by the implemented procedure. This study aims at developing and validating a protocol, associated with a contactless and automatic procedure, enabling the determination of the material behavior and properties of any soft tissues.

Methods: Several markers were drawn onto the soft tissue specimen analyzed under uniaxial tensile test.

Computational modeling of abdominal hernia laparoscopic repair with a surgical mesh.

Purpose: Although new techniques and prostheses have been introduced in ventral hernia surgery, abdominal hernia repair still presents complications, such as recurrence, pain, and discomfort. Thus, this work implements a computational method aimed at evaluating biomechanical aspects of the abdominal hernia laparoscopic repair, which can support clinical research tailored to hernia surgery.

Methods: A virtual solid model of the abdominal wall is obtained from MRI scans of a healthy subject.

In vivo kinematics of knee replacement during daily living activities: Condylar and post-cam contact assessment by three-dimensional fluoroscopy and finite element analyses.

In total knee replacement, the investigation on the exact contact patterns at the post-cam in implanted patients from real in vivo data during daily living activities is fundamental for validating implant design concepts and assessing relevant performances. This study is aimed at verifying the restoration of natural tibio-femoral condylar kinematics by investigating the post-cam engagement at different motor tasks. An innovative validated technique, combining three-dimensional fluoroscopic and finite element analyses, was applied to measure joint kinematics during daily living activities in 15 patients implanted with guided motion posterior-stabilized total knee replacement.

Biomechanical Effects of Different Varus and Valgus Alignments in Medial Unicompartmental Knee Arthroplasty.

Background: Medial unicompartmental tibial components are not always positioned following neutral mechanical alignment and a tibial varus alignment of 3° has been suggested based on several clinical follow-up studies. However, no biomechanical justification is currently available to confirm the suitability of different alignment positions.

Methods: This study aims at quantifying the effects on bone stresses, load distribution, ligament strains, and polyethylene insert stress distribution induced by a possible varus/valgus alignment in medial unicompartmental knee arthroplasty, ranging from 6° of varus to 6° of valgus, developing and using a validated patient-specific finite element model.

How accurate and reproducible are the identification of cruciate and collateral ligament insertions using MRI?

Background: At present, increasing the accuracy of identification of knee ligament insertions is fundamental in developing accurate patient-specific three-dimensional (3D) models for preoperative planning surgeries, designing patient-specific instrumentation or implants, and conducting biomechanical analyses. The accuracy and reproducibility of magnetic resonance imaging (MRI) scans in identifying cruciate and collateral ligament insertions have not been investigated thus far, despite their wide use. This study aimed to define and validate a method for this purpose.

A new graphical method to display data sets representing biomechanical knee behaviour.

Background: When researchers describe data from their studies, there is no rule defining the best way to represent results. Therefore, collecting and explaining results from personal research or understanding data from publications is not always straightforward. These issues are even worse in fields such as biomedical engineering, where researchers from different backgrounds, usually engineers and surgeons, need to interact and exchange information.

An Anthropometric-Based Subject-Specific Finite Element Model of the Human Breast for Predicting Large Deformations.

The large deformation of the human breast threatens proper nodules tracking when the subject mammograms are used as pre-planning data for biopsy. However, techniques capable of accurately supporting the surgeons during biopsy are missing. Finite element (FE) models are at the basis of currently investigated methodologies to track nodules displacement.

All-polyethylene tibial components generate higher stress and micromotions than metal-backed tibial components in total knee arthroplasty.

Purpose: Most total knee arthroplasty tibial components are metal-backed, but an alternative tibial component made entirely of polyethylene (all-polyethylene design) exists. While several clinical studies have shown that all-poly design performs similarly to the metal-backed, the objective of this study is to perform a biomechanical comparison.

Methods: Loads, constraints and geometries during a squat activity at 120° of flexion were obtained from a validated musculoskeletal model and applied to a finite element model.

Knee kinetics and kinematics: What are the effects of TKA malconfigurations?

Purpose: Total knee arthroplasty (TKA) is a very successful surgical procedure. However, implant failures and patient dissatisfaction still persist. Sometimes surgeons are not able to understand and explain these negative performances because the patient's medical images "look good", but the patient "feels bad".

Tibio-femoral kinematics in different total knee arthroplasty designs during a loaded squat: a numerical sensitivity study.

Total Knee Arthroplasty (TKA) is a very successful surgical procedure but clinical outcomes were reported to be affected by implant design, ligament balancing, alignment or patient-related anatomical factors. It was recently demonstrated that malpositioning of the TKA components and patient related anatomical factors can considerably alter tibio-femoral (TF) and patellofemoral maximum contact forces. However, up to now, how a component malpositioning and different soft-tissue anatomy changes TF knee kinematics was not yet fully investigated.

Contact forces in several TKA designs during squatting: A numerical sensitivity analysis.

Total knee arthroplasty (TKA) is a very successful procedure, but pain or difficulties during activities still persist in patients. Patient outcomes in TKA surgery can be affected by implant design, alignment or patient-related anatomical factors. This paper presents a numerical sensitivity analysis of several TKA types: a fixed bearing, posterior stabilized prosthesis, a high flexion fixed bearing guided motion prosthesis, a mobile bearing prosthesis and a hinge prosthesis.