Self-Wrinkling in Polyacrylamide Hydrogel Bilayers.

Swelling of a gel film attached to a soft substrate can induce surface instability, which results in the formation of highly ordered patterns such as wrinkles and folds. This phenomenon has been exploited to fabricate functional devices and rationalize morphogenesis. However, obtaining centimeter-scale patterns without immersing the film in a solvent remains challenging. Here, we show that wrinkles with wavelengths of up to a few centimeters can be spontaneously created during the open-air fabrication of film-substrate bilayers of polyacrylamide (PAAm) hydrogels. When the film of an aqueous pregel solution of acrylamide prepared on the PAAm hydrogel substrate undergoes open-air gelation, hexagonally packed dimples initially emerge on the surface, which later evolve into randomly oriented wrinkles. The formation of such self-organized patterns can be attributed to the surface instability resulting from autonomous water transport in the bilayer system during open-air fabrication. The temporal evolution of the patterns can be ascribed to an increase in overstress in the hydrogel film due to continued water uptake. The wrinkle wavelength can be controlled in the centimeter-scale range by adjusting the film thickness of the aqueous pregel solution. Our self-wrinkling method provides a simple mechanism for the generation of swelling-induced centimeter-scale wrinkles without requiring an external solvent, which is unachievable with conventional approaches.

Conformational deformation of a multi-jointed elastic loop.

A new class of deformation is presented for a planar loop structure made up of slender elastic bodies and joints. In demonstrating the circumferential shortening of the multi-jointed elastic loop, diverse three-dimensional (3D) deformations emerge through piecewise deflections and discrete rotations. These 3D morphologies correspond to conformations of molecular ring systems. Through image processing, the 3D reconstructions of the deformed structures are characterized by number, geometry, and initial imperfections of the body segments. We elucidate from measurements that the conformational deformation without self-stress results from a cyclical assembly of compressive bending of elastic bodies with high shear rigidity. The mechanical insights gained may apply in controlling the polymorphism exhibited by the cyclical structures across scales.

Fibula pro-tibia vs standard locking plate fixation in an ankle fracture saw bone model.

BACKGROUND: Locking plate fixation in osteoporotic ankle fractures may fail due to cut-out or metalwork failure. Fibula pro-tibia fixation was a technique prior to the advent of locking plates that was used to enhance stability in ankle fractures by achieving tri or tetra-cortical fixation. With locking plates, the strength of this fixation construct can be further enhanced. There is lack of evidence currently on the merits of tibia-pro-fibula augmented locking plate fixation of unstable ankle fractures. AIM: To assess if there is increased strength to failure, in an ankle fracture saw bone model, with a fibula pro-tibia construct when compared with standard locking plate fixation. METHODS: Ten osteoporotic saw bones with simulated supination external rotation injuries were used. Five saw bones were fixed with standard locking plates whilst the other 5 saw bones were fixed with locking plates in a fibula pro-tibia construct. The fibula pro-tibia construct involved fixation with 3 consecutive locking screws applied across 3 cortices proximally from the level of the syndesmosis. All fixations were tested in axial external rotation to failure on an electromagnetic test frame (MTS 858 Mini-Bionix test machine, MTS Corp, Eden Praire, MN, United States). Torque at 30 degrees external rotation, failure torque, and external rotation angle at failure were compared between both groups and statistically analyzed. RESULTS: The fibula pro-tibia construct demonstrated a statistically higher torque at 30 degrees external rotation (4.421 ± 0.796 N/m vs 1.451 ± 0.467 N/m; t-test P = 0.000), as well as maximum torque at failure (5.079 ± 0.694N/m vs 2.299 ± 0.931 N/m; t-test P = 0.001) compared to the standard locking plate construct. The fibula pro-tibia construct also had a lower external rotation angle at failure (54.7 ± 14.5 vs 67.7 ± 22.9). CONCLUSION: The fibula pro-tibia locking plate construct demonstrates biomechanical superiority to standard locking plates in fixation of unstable ankle fractures in this saw bone model. There is merit in the use of this construct in patients with unstable osteoporotic ankle fractures as it may aid improved clinical outcomes.

Implicit rule on the elastic function of a swollen polyacrylamide hydrogel.

A full understanding of the elastic properties of hydrogels under swelling is required for their practical application in the chemical and biomedical engineering fields. This is because hydrogels are expected to retain water during mechanical use in moist atmospheres. In the present study, we investigated the relationship between the elastic modulus and the swelling ratio in a specific type of hydrogel (a polyacrylamide gel). The elasticity and swelling data revealed that these two parameters are proportionally related in hydrogels comprising adequate amounts of monomers and crosslinkers. We also demonstrated that this proportional relationship inherently conforms to the linear elastic behaviour predicted by the Flory-Rehner free energy function (the F-R model). The implicit rule is established by the extended F-R model with two scaling exponents. The extended model is capable of representing the irregular elasticity of swollen gels formed from low- or high-molecular-weight polymers.

The importance of power, context and agency in improving patient experience through a patient and family centred care approach.

BACKGROUND: Research shows that the way that healthcare staff experience their job impacts on their individual performance, patient experience and outcomes as well as on the performance of organisations. This article builds on this literature by investigating, with multi-disciplinary clinical teams as well as patients and relatives, what factors help or hinder changes designed to improve patient experience. METHODS: Qualitative research looking at patient- and family-centred care (PFCC) on two care pathways (stroke and hip fracture) was conducted in England and Wales. A realist approach combined with participatory action research was used to account for the complexity of organisational context and power relations. Multiple methods were used, including documentary analysis, participatory steering groups with staff and patient representatives, observations of the care pathways (n = 7), staff and patient and relative focus groups (n = 8), and hospital staff, patient and PFCC staff interviews (n = 47). RESULTS: Findings highlight multiple factors that support and hinder good patient experiences. Within individual care, paternalistic values and a lack of shared decision-making and patient-centred care still exist. Supportive interdisciplinary teamwork is needed to address issues of hierarchy, power and authority amongst staff and managers. At the organisational level, key issues of waiting times, patient flow, organisational resources and timely discharge affect staff's time and capacity to deliver care. In addition, macro contextual factors, such as finance, policy, targets and measures, set particular limits for improvement projects. CONCLUSIONS: Given this context, improving patient experience needs to go well beyond small-scale projects at the micro and meso level to incorporate a more critical understanding of systems, the wider organisational context and how power operates at multiple levels to enable and constrain action. In order to more meaningfully understand and address the factors that can help or hinder activities to improve patient experiences, PFCC frameworks and methods need to account for how power inequities operate and require the adoption of more participatory co-produced and empowering approaches to involve patients, relatives, carers and staff in improving complex healthcare environments.

Evaluation of the effects of cross-linking and swelling on the mechanical behaviors of hydrogels using the digital image correlation method.

Experimental evaluation and modeling are important steps in the investigation of the mechanical behaviors of hydrogels in the small- to large-strain range. In this study, the effects of cross-linking and swelling on the true stress-strain response of a specific type of hydrogel (polyacrylamide) were evaluated using a uniaxial tensile test. The development of true strain on the surface of the hydrogel was measured using the digital image correlation method. The specimens with higher cross-link density exhibited a higher initial elastic modulus and earlier orientation hardening. The initial elastic modulus was reduced by the swelling, whereas the orientation hardening occurred in an earlier strain range in the swollen hydrogel. The mechanical responses of the as-prepared and swollen hydrogels with different cross-linker contents were fitted using a non-Gaussian statistical model. The conventional model underestimated the decrease in the elasticity owing to the swelling effect and overestimated the increase in the stress in the large-strain range. The mechanical model was suitably modified to yield an accurate reproduction of the mechanical responses. The proposed model, which was characterized by five material parameters, was found to reproduce the characteristics of the mechanical responses of the as-prepared and swollen hydrogels with different cross-linker contents.

Clinical Outcomes Following Minimally Invasive Dorsal Cheilectomy for Hallux Rigidus.

BACKGROUND:: Following failure of conservative treatment, a dorsal cheilectomy can be performed for patients in early stages of hallux rigidus by a traditional open approach or by a minimally invasive technique. We report our clinical outcomes following minimally invasive dorsal cheilectomy (MIDC). METHODS:: Eighty-nine patients (98 feet) with symptomatic hallux rigidus treated between 2011 and 2016 were included in this study. The average age was 54 years. Manchester-Oxford Foot Questionnaire (MOxFQ) scores and visual analog scale (VAS) pain scores were collected. The mean follow-up was 50 months. RESULTS:: The average VAS score improved from 8.0 preoperatively to 3 postoperatively. The mean MOxFQ summary index score decreased from 58.6 preoperatively to 30.5 postoperatively. All 3 MOxFQ domains also improved. Swelling took an average of 5.3 weeks to settle. There were 2 wound infections and 2 delayed wound healings. Two patients had transient nerve paraesthesia, while 2 patients had permanent numbness in the dorsomedial cutaneous nerve distribution. Twelve patients (12%) underwent reoperation, of which 7 had a first metatarsophalangeal joint arthrodesis for ongoing pain, 4 had repeat cheilectomy for residual impingement, and 1 had an open removal of loose bone. CONCLUSION:: Our results suggest that MIDC resulted in improvement in patient-reported outcome measures and was a safe technique with minimal complications. The complications were similar to open cheilectomy. There was an associated learning curve as 5 of our reoperations were due to incomplete cheilectomy. Coughlin grade 1 did well with MIDC as with open cheilectomy as none went onto an arthrodesis. However, 10% (7/65) of our grade 2 and 3 cases went on to an arthrodesis. LEVEL OF EVIDENCE:: Level IV, retrospective case series.

Minimally Invasive Dorsal Cheilectomy of the First Metatarsal: A Cadaveric Study.

BACKGROUND:: Minimally invasive dorsal cheilectomy (MIDC) for hallus rigidus is gaining in popularity. The optimal position for the stab incision for MIDC is dorsomedial to allow an ergonomic sweeping movement of the burr, potentially putting the dorsomedial cutaneous nerve (DMCN) to the hallux at risk. We aimed to quantify the risk of using this minimally invasive technique with a cadaveric study. METHODS:: A total of 13 fresh-frozen cadaveric specimens amputated below the knee were obtained for this study. After the procedure, the specimens were dissected, and structures were inspected for damage. RESULTS:: The DMCN to the hallux was cut completely in 2 specimens (15%). All the extensor hallucis longus tendons were intact, although in 1 specimen, the tendon showed some fraying on the underside of the tendon. The average distance of the stab incision from the first metatarsophalangeal (MTP) joint was 17.7 (range, 10-23) mm. The relationship of the DMCN to the stab incision was variable. The average distance of the DMCN to the incision was 3.8 (range, 0-7) mm. The danger zone for damaging the DMCN was at one-third the length of the first metatarsal proximal to the first MTP joint. CONCLUSION:: The DMCN has been well studied by several authors and has a variable course. This nerve was damaged in 15% of our specimens following MIDC. CLINICAL RELEVANCE:: We believe patients should be made aware of this risk when considering surgery. A carefully made working capsular pocket for the burr and marking this nerve before making the incision if palpable could mitigate this risk.

Orthotropic Laminated Open-cell Frameworks Retaining Strong Auxeticity under Large Uniaxial Loading.

Anisotropic materials form inside living tissue and are widely applied in engineered structures, where sophisticated structural and functional design principles are essential to employing these materials. This paper presents a candidate laminated open-cell framework, which is an anisotropic material that shows remarkable mechanical performance. Using additive manufacturing, artificial frameworks are fabricated by lamination of in-plane orthotropic microstructures made of elbowed beam and column members; this fabricated structure features orthogonal anisotropy in three-dimensional space. Uniaxial loading tests reveal strong auxeticity (high negative Poisson's ratios) in the out-of-plane direction, which is retained reproducibly up to the nonlinear elastic region, and is equal under tensile and compressive loading. Finite element simulations support the observed auxetic behaviors for a unit cell in the periodic framework, which preserve the theoretical elastic properties of an orthogonal solid. These findings open the possibility of conceptual materials design based on geometry.

Comparison of transverse wires and half pins in Taylor Spatial Frame: a biomechanical study.

BACKGROUND: The aim of this study was to compare the stiffness characteristics of Taylor Spatial Frame (TSF) fixed with transverse wires and half pins. DESIGN & METHODS: Experiments were carried out at the biomechanics laboratory at Cardiff University. All mechanical testing was performed with a servo hydraulic test frame (MTS 858 Mini Bionix II(R), MTS Corp., Mineapolis, USA). Custom built mounts were used to attach the bone rigidly to the one end of machine and the TSF ring to the other. Rings were fixed with 1.8 mm transverse wires or hydroxy-apatite coated 6.5 mm half pins in 45 degrees, 60 degrees, 75 degrees and 90 degrees divergence angles. Bone was loaded with axial load to 400 N and torque to 20 Nm in an indestructible manner. Load/displacement curve data were analyzed for slope and axial and angular displacements. RESULTS: For larger diameter rings (180 mm), for axial stiffness there was no statistically significant difference between the transverse wires (4 wires with 2 rings) and the half pins (2 pins with 1 ring) (p > 0.05). For 155 mm internal diameter rings, half pins provided statistically higher axial stiffness than transverse wires (p = 0.036). The half pins show significantly more torsion stiffness in both ring diameters (p < 0.05) in comparison to transverse wires. As in axial stiffness, small diameter rings show increased stiffness in torsion. There is increase in axial and torsion stiffness with the increase in the divergence angle between the wires or pins (p < 0.05). CONCLUSION & CLINICAL RELEVANCE: Half pins provide greater stiffness to TSF frames and allow for axial micro motion as well. This work provides a rationale for clinical decision making about the use of tensioned transverse wires in comparison to half pins in construction of a TSF frame.

Slipped upper femoral epiphysis in a 19-year-old male.

The authors present a case of unilateral slipped upper femoral epiphysis (SUFE) in a 19-year old-male patient. An accompanying hypogonadism was noted on physical examination and laboratory tests. Extensive endocrinological work up revealed constitutional delay in puberty as the cause of hypogonadism. This is the first reported case of constitutional delay in puberty presenting with SUFE in English literature. There were six cases of SUFE reported in the literature at an age older than the typical age range (10-16 years), of which five cases were the result of hypopituitarism and one case of radiation-induced hypooestrogenism. Our case highlights the importance of thorough history taking, clinical examination and early involvement of the endocrinology team in SUFE presenting at an age older than the typical age range to prevent delay in diagnosis and appropriate treatment.

Revisiting the concept of talar shift in ankle fractures.

BACKGROUND: In 1976, Ramsey and Hamilton published a classic experiment investigating the biomechanical effects of talar shift in a simple ankle fracture model. Their finding was that 1 mm of talar shift resulted in a 42% decrease in tibiotalar contact surface area. Based on this conclusion, 1 mm of talar shift became the recognized indication for operative fixation. METHODS: Twelve cadaver ankles were dissected and the distal tibia coated with carbon powder. A 70-kg load was applied to the distal tibia that resulted in transference of the carbon onto the talus. The contact surface area was determined at 0, 1, 2, 4 and 6 mm of talar shift using spacers fixed in the medial gutter. Tracing paper was used to mark the outline of the contact area and measured using graph paper. RESULTS: Our results were similar to Ramsey and Hamilton's original experiment. One millimeter of lateral talar shift resulted in 40% loss of contact surface area compared with 42% in the original experiment. A large variance was seen in talar contact surface area depending on the morphology of the ankle joint. CONCLUSION: Ramsey and Hamilton's original experiment was valid.

Tumor-dendritic cell fusion as a basis for cancer immunotherapy.

OBJECTIVE: To establish the basis for use of allogeneic dendritic-tumor fusion cells. STUDY DESIGN: Fusion cells were created by electrofusion. We used 2 allogeneic murine tumor lines (D5 and 4T1) that were virally transduced to express the antigen (beta-galactosidase) as a surrogate tumor marker. RESULTS: Cross-immunization was achieved with irradiated allogenic tumor cells. Successful electrofusion of dendritic cells and tumor cells was confirmed by using fluorescence-activated cell sorting and cytospin. Significant responses were shown in immunized mice against tumor challenge and established 3-day pulmonary metastasis with fusion cells. CONCLUSIONS: Allogeneic tumor sharing a common tumor antigen can immunize against syngeneic tumor challenge. Fusion cells showed successful immunization against tumor challenge and showed regression of 3-day established pulmonary metastasis. SIGNIFICANCE: These preclinical studies provide evidence that an allogenic tumor-dendritic cell fusion vaccine is a valid approach for head and neck cancer immunotherapy.