Biomechanical Value of a Protective Proximal Humeral Cerclage in Reverse Total Shoulder Arthroplasty

Reverse shoulder arthroplasty (RSA) is a commonly performed salvage procedure for failed proximal humeral fracture fixation. The rate of intraoperative periprosthetic fractures is higher compared to primary RSA. The goal of this study was to investigate the biomechanical value of a protective cerclage during stem impaction in a revision surgery setting. Twenty-eight fresh-frozen human humeri were used to assess different configurations for steel wire and FiberTape cerclages. A custom-built biomechanical test setup simulated the mallet strikes during the stem impaction process with the Univers Revers prothesis stem. The mallet energy until the occurrence of a first crack was not different between groups. The total energy until progression of the fracture distally to the cerclage was significantly higher in the cerclage groups compared to the native humerus (9.5 J vs. 3.5 J, respectively; p = 0.0125). There was no difference between the steel wire and FiberTape groups (11.4 J vs. 8.6 J, respectively; p = 0.2695). All fractures were located at the concave side of the stem at the metaphyseal calcar region. This study demonstrates that a protective cerclage can successfully delay the occurrence of a fracture during stem impaction in reverse shoulder arthroplasty. A FiberTape cerclage is biomechanically equally efficient compared to a steel wire cerclage.

The Lack of Sex, Age, and Anthropometric Diversity in Neck Biomechanical Data

Female, elderly, and obese individuals are at greater risk than male, young, and non-obese individuals for neck injury in otherwise equivalent automotive collisions. The development of effective safety technologies to protect all occupants requires high quality data from a range of biomechanical test subjects representative of the population at risk. Here we sought to quantify the demographic characteristics of the volunteers and post-mortem human subjects (PMHSs) used to create the available biomechanical data for the human neck during automotive impacts. A systematic literature and database search was conducted to identify kinematic data that could be used to characterize the neck response to inertial loading or direct head/body impacts. We compiled the sex, age, height, weight, and body mass index (BMI) for 999 volunteers and 110 PMHSs exposed to 5,431 impacts extracted from 63 published studies and three databases, and then compared the distributions of these parameters to reference data drawn from the neck-injured, fatally-injured, and general populations. We found that the neck biomechanical data were biased toward males, the volunteer data were younger, and the PMHS data were older than the reference populations. Other smaller biases were also noted, particularly within female distributions, in the height, weight, and BMI distributions relative to the neck-injured populations. It is vital to increase the diversity of volunteer and cadaveric test subjects in future studies in order to fill the gaps in the current neck biomechanical data. This increased diversity will provide critical data to address existing inequities in automotive and other safety technologies.

Functionalization of Screw Implants with Superelastic Structured Nitinol Anchoring Elements

Demographic change is leading to a increase in the number of osteoporotic patients, so that a rethink is required in implantology in order to be able to guarantee adequate anchoring stability in the bone. The functional modification of conventional standard screw implants by the use of superelastic, structured Ti6Al4V anchoring elements promises great potential for increasing anchoring stability. For this purpose, conventional screw implants were mechanically machined and extended so that structured-superelastic-positionable-Ti6Al4V anchoring elements could be used. The set-up of the anchoring elements was investigated in CT studies in an artificial bone. In a subsequent handling test, the handling of the function samples was evaluated under surgical conditions. The anchorage stability to standard screw implants was investigated in a final pull-out test according to "ASTM F543".The functionalization of conventional screw implants with structured superelastic Ti6Al4V anchoring elements is technically realizable. It has been demonstrated that the anchoring elements can be set up in the artificial bone without any problems. The anchorage mechanism is easy to handle under operating conditions and the anchoring elements have no negative impact on the surgical procedure. It was shown that, compared to conventional standard screws, more mechanical work is required to remove the functional patterns completely from the bone.In summary, it was shown that conventional standard screw implants can be functionalized with Ti6Al4V structured NiTi anchoring elements and are suitable for orthopedic and neurosurgical use. A first biomechanical test showed that the anchoring stability can be increased by the anchoring elements.

The Biomechanics of Cartilage—An Overview

Articular cartilage (AC) sheathes joint surfaces and minimizes friction in diarthrosis. The resident cell population, chondrocytes, are surrounded by an extracellular matrix and a multitude of proteins, which bestow their unique characteristics. AC is characterized by a zonal composition (superficial (tangential) zone, middle (transitional) zone, deep zone, calcified zone) with different mechanical properties. An overview is given about different testing (load tests) methods as well as different modeling approaches. The widely accepted biomechanical test methods, e.g., the indentation analysis, are summarized and discussed. A description of the biphasic theory is also shown. This is required to understand how interstitial water contributes toward the viscoelastic behavior of AC. Furthermore, a short introduction to a more complex model is given.

A model to differentiate WAD patients and people with abnormal pain behaviour based on biomechanical and self-reported tests

The prevalence of malingering among individuals presenting whiplash-related symptoms is significant and leads to a huge economic loss due to fraudulent injury claims. Various strategies have been proposed to detect malingering and symptoms exaggeration. However, most of them have been not consistently validated and tested to determine their accuracy in detecting feigned whiplash. This study merges two different approaches to detect whiplash malingering (the mechanical approach and the qualitative analysis of the symptomatology) to obtain a malingering detection model based on a wider range of indices, both biomechanical and self-reported. A sample of 46 malingerers and 59 genuine clinical patients was tested using a kinematic test and a self-report questionnaire asking about the presence of rare and impossible symptoms. The collected measures were used to train and validate a linear discriminant analysis (LDA) classification model. Results showed that malingerers were discriminated from genuine clinical patients based on a greater proportion of rare symptoms vs. possible self-reported symptoms and slower but more repeatable neck motions in the biomechanical test. The fivefold cross-validation of the LDA model yielded an area under the curve (AUC) of 0.84, with a sensitivity of 77.8% and a specificity of 84.7%.

Investigation of a Modified Novel Technique in Bilateral Sagittal Splitting Osteotomy Fixation: Finite Element Analysis and In Vitro Biomechanical Test

Purpose. To evaluate the biomechanical properties of the modified novel 2-hole monocortical plate fixation (2HMCPf) and traditional 4-hole monocortical plate fixation (4HMCPf) techniques in bilateral sagittal splitting osteotomy (BSSO) synthesis using a finite element analysis (FEA) and an in vitro biomechanical test with the application of a shearing loading force on a sawbone mandible model. Materials and Methods. A three-dimensional mandible models were generated using the geometry obtained from the computerized tomography image of a sawbone mandible. Plates and screws were generated and combined with the mandible in a CAD environment. The 2HMCPf and traditional 4HMCPf techniques for BSSO osteosynthesis were then analyzed under the occlusal load using the FEA. An in vitro biomechanical test was executed to verify the result of FEA. The force on fixation failure and pattern of failure were recorded. Results. The results revealed that the von Mises Stress on the mandible cortical bone (75.98 MPa) and the screw/plate (457.19 MPa) of the 2HMCPf group was lower than that of the 4HMCPf group (987.68 MPa, 1781.59 MPa). The stress concentrated on the central region of the 4HMCPf group and the distal set of the 2HMCPf group. In vitro study using the sawbone mandible model showed mechanical failure at the region of the proximal segment near the osteotomy site with the 4HMCPf group (average 32.198 N) but no failure on the fixation sites with the 2HMCPf group. Instead, the mandible sawbone fractured on the condyle neck region (average 44.953 N). Conclusion. From the biomechanical perspective, we proved that the 2HMCPf method was able to withstand a higher shearing loading force than the 4HMCPf fixation method in BSSO osteosynthesis.

Torsional comparative biomechanical test of modified tibial-plateau-leveling osteotomy plate and locking plate in canine synthetic tíbias

ABSTRACT The objective of this study was to develop a locked tibial-plateau-leveling osteotomy (TPLO) plate and to compare this implant with the conventional bone fixation method using a locked plate to determine bone stabilization against torsion forces. Maximum force, angle at peak torque, and stiffness values were determined. Ten synthetic tibias were used, divided into 2 groups. The results in Group 1 (modified TPLO plate) and Group 2 (locked plate) were assessed using analysis of variance and the means were compared using Tukey’s test at 5% probability. There were significant differences in the angle at peak torque and stiffness. The group Modified TPLO plate had higher mean values of stiffness compared with Group locked plate. Group locked plate showed a greater angle at peak torque compared with Group modified TPLO plate. All constructs failed due to tibial fractures distal to the plate. The modified TPLO plate presented higher stiffness indexes than conventional locked plate in torsion. The locked plate presented greater elasticity than modified TPLO plate having greater angle at the peak of torque.