A Two-Experiment Approach to Scaling in Biomechanics.

A new approach to scaled experimentation has recently appeared in the open literature where hitherto unknown similitude rules have been discovered. The impact of this discovery on biomechanics is the focus of this paper, where rules for one and two scaled experiments are assessed. Biomechanical experimentation is beset by problems that can hinder its successful implementation.

Zeroth-order finite similitude and scaling of complex geometries in biomechanical experimentation.

Scaled experimentation provides an alternative approach to full-scale biomechanical (and biological) testing but is known to suffer from scale effects, where the underlying system behaviour changes with scale. This phenomenon is arguably the overriding principal obstacle to the many advantages that scaled experimentation provides. These include reduced costs, materials and time, along with the eschewal of ethical compliance concerns with the application of substitute artificial materials as opposed to the use of hazardous biological agents.

Performance evaluation of surgical techniques for treatment of scapholunate instability in a type II wrist.

We investigated the performance of three tenodesis techniques, modified Brunelli, Corella, and scapholunate axis (SLAM) methods in repairing scapholunate interosseous ligament (SLIL) disruption for a type II wrist using finite element-based virtual surgery and compared the results with those of a previous investigation for a type I wrist. In addition, a comparison of the carpal mechanics of type I and type II wrists was undertaken in order to elucidate the difference between the two types. For the type II wrist, following simulated SLIL disruption, the Corella reconstruction technique provided a superior outcome, restoring dorsal gap, volar gap, and SL angle to within 3.

Effect of Femoral Head Size, Subject Weight, and Activity Level on Acetabular Cement Mantle Stress Following Total Hip Arthroplasty.

In cases where cemented components are used in total hip arthroplasty, damage, or disruption of the cement mantle can lead to aseptic loosening and joint failure. Currently, the relationship between subject activity level, obesity, and prosthetic femoral head size and the risk of aseptic loosening of the acetabular component in cemented total hip arthroplasty is not well understood. This study aims to provide an insight into this.

Impact of femoroacetabular impingement and dysplasia of the hip on hip joint sphericity.

Background: This paper presents a parametric investigation into the effect of femoroacetabular impingement (FAI) and developmental dysplasia of the hip (DDH) on the sphericity of the femoral supra-equatorial region and acetabulum.

Methods: Radiographic parameters from x-rays, sphericity calculations and visualisation and joint contact area and pressure from FE models of 10 DDH, FAI and normal hips were analysed and compared both within and between hip groups.

Results: The sphericity of the acetabulum and femoral head of both the DDH and FAI groups was found to be less than that for normal hips but the variation in sphericity was greater (range 2.

Validation of biofilm formation on human skin wound models and demonstration of clinically translatable bacteria-specific volatile signatures.

Biofilms are major contributors to delayed wound healing and there is a need for clinically relevant experimental models to assess theranostics. Microorganisms release volatile organic compounds (VOCs) and the ability to identify these in infected cutaneous wounds could lead to efficient non-invasive diagnosis. The aims here were to develop and assess bacterial biofilm formation and identify their VOC profiles in an in vitro model and validate in human ex vivo incisional and excisional cutaneous wound models.

Scaling in biomechanical experimentation: a finite similitude approach.

Biological experimentation has many obstacles: resource limitations, unavailability of materials, manufacturing complexities and ethical compliance issues; any approach that resolves all or some of these is of some interest. The aim of this study is applying the recently discovered concept of finite similitude as a novel approach for the design of scaled biomechanical experiments supported with analysis using a commercial finite-element package and validated by means of image correlation software. The study of isotropic scaling of synthetic bones leads to the selection of three-dimensional (3D) printed materials for the trial-space materials.

Cement interface and bone stress in total hip arthroplasty: Relationship to head size.

The use of larger prosthetic femoral heads in total hip arthroplasty (THA) has increased considerably in recent years in response to the need to improve joint stability and reduce risk of dislocation. However, data suggests larger femoral heads are associated with higher joint failure rates. For cemented implants, ensuring the continued integrity of the cement mantle is key to long term fixation.

Evaluation of the performance of three tenodesis techniques for the treatment of scapholunate instability: flexion-extension and radial-ulnar deviation.

Chronic scapholunate ligament (SL) injuries are difficult to treat and can lead to wrist dysfunction. Whilst several tendon reconstruction techniques have been employed in the management of SL instability, SL gap reappearance after surgery has been reported. Using a finite element model and cadaveric study data, we investigated the performance of the Corella, scapholunate axis (SLAM) and modified Brunelli tenodesis (MBT) techniques.

Volatile organic compound detection as a potential means of diagnosing cutaneous wound infections.

Chronic cutaneous wound infections and surgical site infections (SSIs) present a huge burden on the healthcare system and can lead to increased morbidity and mortality. Current diagnostic methods of identifying and confirming infection involve culture-based and molecular methods. Both techniques are time-consuming and delays commonly lead to untargeted empirical treatment.

Analysis of tenodesis techniques for treatment of scapholunate instability using the finite element method.

Chronic scapholunate ligament (SL) injury is a common disorder affecting the wrist. Despite advances in surgical techniques used to treat this injury, SL gap re-emergence may occur postoperatively. This paper presents an investigation into the performance of the Corella, schapolunate axis (SLAM), and modified Brunelli tenodesis (MBT) surgical reconstruction techniques used to treat scapholunate instability.

3-D computer modelling of malunited posterior malleolar fractures: effect of fragment size and offset on ankle stability, contact pressure and pattern.

Background: The positioning of the fracture fragment of a posterior malleolus fracture is critical to healing and a successful outcome as malunion of a posterior malleolar fracture, a condition seen in clinical practice, can affect the dynamics of the ankle joint, cause posterolateral rotational subluxation of the talus and ultimately lead to destruction of the joint. Current consensus is to employ anatomic reduction with internal fixation when the fragment size is larger than 25 to 33% of the tibial plafond.

Methods: A 3-dimensional finite element (FE) model of ankle was developed in order to investigate the effect of fragment size (6-15 mm) and offset (1-4 mm) of a malunited posterior malleolus on tibiotalar joint contact area, pressure, motion of joint and ligament forces.

Cutaneous wound biofilm and the potential for electrical stimulation in management of the microbiome.

Infection contributes significantly to delayed cutaneous wound healing, which impacts patient care. External application of electrical stimulation (ES) has beneficial effects on wound repair and regeneration. The majority of studies to date have explored ES in relation to planktonic microorganisms, yet evidence indicates that bacteria in chronic wounds reside as antibiotic-resistant polymicrobial biofilms, which contribute to impairing wound healing.

The efficacy of electrical stimulation in lower extremity cutaneous wound healing: A systematic review.

Current gold standard lower extremity cutaneous wound management is not always effective. Cutaneous wounds generate a "current of injury" which is directly involved in wound healing processes. Application of exogenous electrical stimulation has been hypothesised to imitate the natural electric current that occurs in cutaneous wounds.

Effect of Anconeus Muscle Blocking on Elbow Kinematics: Electromyographic, Inertial Sensors and Finite Element Study.

The specific contribution of the anconeus muscle to elbow function is still uncertain. This study aimed to investigate the effect on elbow kinematics and kinetics of blocking anconeus using lidocaine. Ten healthy volunteers performed experimental trials involving flexion-extension and supination-pronation movements in horizontal and sagittal planes.

Whole genome microarray data of chronic wound debridement prior to application of dermal skin substitutes.

Clinical consensus is that debridement is necessary for successful application of dermal skin substitutes (DSS) to chronic wounds. The aim here was to identify commonly expressed genes associated with wound healing in untreated acute wounds and chronic wounds treated with wound debridement followed by DSS. Cutaneous biopsies were taken at two time points from untreated acute and chronic wounds and from chronic wounds treated with DSS following debridement.

The efficacy of electrical stimulation in experimentally induced cutaneous wounds in animals.

Background: Complicated cutaneous wounds and their subsequent management can be a clinical challenge in veterinary medicine. There is still an unmet need for an ideal wound healing therapy that is able to stimulate efficiency and quality of repair. Skin wounds generate large and persistent endogenous electric currents and fields termed the "current of injury".

Optimization of an ex vivo wound healing model in the adult human skin: Functional evaluation using photodynamic therapy.

Limited utility of in vitro tests and animal models of human repair, create a demand for alternative models of cutaneous healing capable of functional testing. The adult human skin Wound Healing Organ Culture (WHOC) provides a useful model, to study repair and enable evaluation of therapies such as the photodynamic therapy (PDT). Thus, the aim here was to identify the optimal WHOC model and to evaluate the role of PDT in repair.

Skin substitute-assisted repair shows reduced dermal fibrosis in acute human wounds validated simultaneously by histology and optical coherence tomography.

Skin substitutes are heterogeneous biomaterials designed to accelerate wound healing through provision of replacement extracellular matrix. Despite growing evidence for their use in chronic wounds, the role of skin substitutes in acute wound management and their influence on fibrogenesis remains unclear. Skin substitute characteristics including biocompatibility, porosity, and elasticity strongly influence cellular behavior during wound healing.

Ex vivo evaluation of the effect of photodynamic therapy on skin scars and striae distensae.

Background: Skin scars and striae distensae (SD) are common dermal disorders with ill-defined treatment options. There is emerging clinical evidence for use of photodynamic therapy (PDT) in treating skin fibrosis. Therefore, the aim here was to investigate the effect of PDT on skin scars and SD in an ex vivo model of human skin scarring.

Acute cutaneous wounds treated with human decellularised dermis show enhanced angiogenesis during healing.

Background: The influence of skin substitutes upon angiogenesis during wound healing is unclear.

Objectives: To compare the angiogenic response in acute cutaneous human wounds treated with autogenic, allogenic and xenogenic skin substitutes to those left to heal by secondary intention.

Methods: On day 0, four 5mm full-thickness punch biopsies were harvested from fifty healthy volunteers (sites 1-4).

Identification of biomarkers involved in differential profiling of hypertrophic and keloid scars versus normal skin.

Among raised dermal scar types, keloid (KS) and hypertrophic scars (HS) are considered to present clinical similarities, but there are no known specific biomarkers that allow both scar types to be easily distinguished. Development and progression of raised dermal scars comprises the activation of several molecular pathways and cell defence mechanisms leading to elevated extracellular matrix component synthesis, delayed apoptosis, altered migration and differentiation. Therefore, the aim here was to identify biomarkers that may differentiate between KS and HS compared to normal skin (NS).

Physico-chemical characteristics of coated silicone textured versus smooth breast implants differentially influence breast-derived fibroblast morphology and behaviour.

Capsule formation is an inevitable consequence of silicone breast implantation. Clinically challenging dense fibrocollagenous capsular contractures occur at different rates between smooth compared to textured surfaces. Host response is influenced by several factors including implant surface texture, chemistry and interactions between cells and the extracellular matrix (ECM).

Characterisation of breast implant surfaces and correlation with fibroblast adhesion.

Introduction: Capsular contracture formation is a common complication following breast augmentation surgery. Breast implant shells have either a smooth or a textured surface. Smooth surfaces demonstrate a higher incidence of contracture formation.

Up-regulation of tension-related proteins in keloids: knockdown of Hsp27, α2β1-integrin, and PAI-2 shows convincing reduction of extracellular matrix production.

Background: Keloid disease is a fibroproliferative disorder, with an ill-defined treatment that is characterized by excessive extracellular matrix deposition. Mechanical tension promotes deposition of extracellular matrix and overexpression of tension-related proteins, which is associated with keloid disease. The aim of this study was to investigate the effect of tension-related proteins on extracellular matrix steady-state synthesis in primary keloid fibroblasts.