Crimped fiber composites: mechanics of a finite-length crimped fiber embedded in a soft matrix.

Composites comprising crimped fibers of finite length embedded in a soft matrix have the potential to mimic the strain-hardening behavior of tissues containing fibrous collagen. Unlike continuous fiber composites, such chopped fiber composites would be flow-processable. Here, we study the fundamental mechanics of stress transfer between a single crimped fiber and the embedding matrix subjected to tensile strain. Finite element simulations show that fibers with large crimp amplitude and large relative modulus straighten significantly at small strain without bearing significant load. At large strain, they become taut and hence bear increasing load. Analogous to straight fiber composites, there is a region near the ends of each fiber which bears much lower stress than the midsection. We show that the stress-transfer mechanics can be captured by a shear lag model where the crimped fiber can be replaced with an equivalent straight fiber whose effective modulus is lower than that of the crimped fiber, but increases with applied strain. This allows estimating the modulus of a composite at low fiber fraction. The degree of strain hardening and the strain needed for strain hardening can be tuned by changing relative modulus of the fibers and the crimp geometry.

Dynamic Luminal Topography: A Potential Strategy to Prevent Vascular Graft Thrombosis.

AIM: Biologic interfaces play important roles in tissue function. The vascular lumen-blood interface represents a surface where dynamic interactions between the endothelium and circulating blood cells are critical in preventing thrombosis. The arterial lumen possesses a uniform wrinkled surface determined by the underlying internal elastic lamina. The function of this structure is not known, but computational analyses of artificial surfaces with dynamic topography, oscillating between smooth and wrinkled configurations, support the ability of this surface structure to shed adherent material (Genzer and Groenewold, 2006; Bixler and Bhushan, 2012; Li et al., 2014). We hypothesized that incorporating a luminal surface capable of cyclical wrinkling/flattening during the cardiac cycle into vascular graft technology may represent a novel mechanism of resisting platelet adhesion and thrombosis. METHODS AND RESULTS: Bilayer silicone grafts possessing luminal corrugations that cyclically wrinkle and flatten during pulsatile flow were fabricated based on material strain mismatch. When placed into a pulsatile flow circuit with activated platelets, these grafts exhibited significantly reduced platelet deposition compared to grafts with smooth luminal surfaces. Constrained wrinkled grafts with static topography during pulsatile flow were more susceptible to platelet accumulation than dynamic wrinkled grafts and behaved similar to the smooth grafts under pulsatile flow. Wrinkled grafts under continuous flow conditions also exhibited marked increases in platelet accumulation. CONCLUSION: These findings provide evidence that grafts with dynamic luminal topography resist platelet accumulation and support the application of this structure in vascular graft technology to improve the performance of prosthetic grafts. They also suggest that this corrugated structure in arteries may represent an inherent, self-cleaning mechanism in the vasculature.

Injuries in Cricket.

CONTEXT: Cricket is a popular global sport that requires a combination of physical fitness, skill, and strategy. Although a noncontact sport, overuse and impact injuries are common since players engage in a wide range of physical activities, including running, throwing, batting, bowling, catching, and diving. Significant or match time-loss injuries are defined as those that either prevent a player from being fully available for selection in a major match, or during a major match, cause a player to be unable to bat, bowl, or keep wicket when required by either the rules or the team's captain. This review describes the various region-wise injuries sustained in cricket along with their epidemiology, biomechanics, treatment, and prevention. EVIDENCE ACQUISITION: Data were collected from peer-reviewed articles (obtained via PubMed search) published through November 2016 that involved the medical, biomechanical, and epidemiological aspects of cricket injuries. STUDY DESIGN: Clinical review. LEVEL OF EVIDENCE: Level 4. RESULTS: Cricket was one of the first sports to publish recommended methods for injury surveillance in 2005 from England, South Africa, Australia, the West Indies, and India. While the incidence of injuries is about the same, the prevalence of injuries has increased due to game format changes, increasing number of matches played, and decreased rest between matches. Bowling (41.3%), fielding, and wicket keeping (28.6%) account for most injuries. Acute injuries are most common (64%-76%), followed by acute-on-chronic (16%-22.8%) and chronic ones (8%-22%). The most common modern-day cricket injury is hamstring strain, and the most severe is lumbar stress fracture in young fast bowlers. CONCLUSION: With improved understanding of the scientific and medical aspects of cricket, along with advances in surgical and nonsurgical treatment techniques, the time to return to play has shortened considerably. While the prevalence of cricket injuries has increased, their severity has decreased over the past decades.

Knee Dislocations in Sports Injuries.

Knee dislocations are devastating when they occur on the athletic field or secondary to motor sports. The complexity of presentation and spectrum of treatment options makes these injuries unique and extremely challenging to even the most experienced knee surgeons. An astute appreciation of the treatment algorithm is essential to plan individualized management since no two complex knee dislocations are ever the same. Moreover, attention to detail and finesse of surgical technique are required to obtain a good functional result and ensure return to play. Over the past 10 years, our service has treated 43 competitive sportsmen with knee dislocations, and this experience forms the basis for this narrative review.

Postencephalitic bilateral heterotopic ossification of the hip in a pediatric patient.

Heterotrophic ossification has been defined as abnormal formation of mature lamellar bone in soft tissues. Neurogenic heterotopic ossification has been well described in adults. However, it is uncommon in the pediatric population, where it has been noted to recede in some cases. There are very few reports of postmeningitis bilateral involvement of the hip. We describe a case of bilateral heterotopic ossification of hip in a 13-year-old female. The patient had a history of encephalitis, prolonged vegetative state, and intubation for 6 weeks. The patient had fixed deformities of both hips in 30° of flexion and 30° of external rotation. A diagnosis of Brooker stage 4 heterotopic ossification was made. The patient underwent a staged procedure for excision of the heterotopic mass. Postoperatively, the patient was administered radiotherapy and indomethacin for 6 weeks. At the 2-year follow-up, there was no recurrence and both the hips were mobile with full range of motion. The patient was satisfied with the result. The incidence of heterotopic ossification is less than that observed in the adult population and alkaline phosphatase levels are not significantly elevated unlike in adults. To our knowledge, there is no reported case of postencephalitic bilateral anterior heterotopic ossification of the hip in a pediatric patient treated with excision successfully. Postencephalitic heterotopic ossification in children is an uncommon condition. This condition can be treated successfully with surgical excision, combined postoperative protocol of radiotherapy, indomethacin, and immediate postoperative mobilization of the joint.

Correlation of posterior tibial slope with metaphysio-diaphyseal angle in total knee arthroplasty: A radiological study.

BACKGROUND: Posterior tibial slope (PTS) is an important factor affecting postoperative range of motion (ROM) following total knee arthroplasty (TKA). Metaphysio-diaphyseal angle (MDA) is a new entity defined as angle between proximal anatomical axis and metaphyseal axis of tibia. This study was undertaken to determine PTS in Indian patients and find its correlation with MDA of tibia. Accuracy of extramedullary jigs and the influence of MDA on the accuracy was also evaluated. This study is a retrospective analysis of prospectively collected data in a tertiary healthcare center. MATERIALS AND METHODS: Data of 100 consecutive patients undergoing TKA in a single center by a single surgeon was analyzed. Posterior cruciate ligament (PCL) substituting TKA was done with same jig to achieve different PTS in different patients. MDA, preoperative PTS and postoperative PTS were calculated. The data was analyzed using appropriate statistical analysis. RESULTS: Mean preoperative PTS was 11.64° and mean MDA was 23.76° with a strong correlation between them (Pearson's coefficient 0.72). Extramedullary jigs were accurate in 53% cases. In remaining 47%, postoperative PTS was less than planned PTS in 30%, and more in 17%. Mean postoperative PTS was 2.54°. In patients with MDA < 20°, postoperative PTS was significantly less (P = 0.0176) compared with those with MDA > 20°. CONCLUSIONS: The study establishes the positive correlation between MDA and PTS in Indians; and that MDA is an independent factor affecting accuracy of extramedullary jigs in TKA.

A phospholipase C-γ1-independent, RasGRP1-ERK-dependent pathway drives lymphoproliferative disease in linker for activation of T cells-Y136F mutant mice.

Mice expressing a germline mutation in the phospholipase C-γ1-binding site of linker for activation of T cells (LAT) show progressive lymphoproliferation and ultimately die at 4-6 mo age. The hyperactivated T cells in these mice show defective TCR-induced calcium flux but enhanced Ras/ERK activation, which is critical for disease progression. Despite the loss of LAT-dependent phospholipase C-γ1 binding and activation, genetic analysis revealed RasGRP1, and not Sos1 or Sos2, to be the major Ras guanine exchange factor responsible for ERK activation and the lymphoproliferative phenotype in these mice. Analysis of isolated CD4(+) T cells from LAT-Y136F mice showed altered proximal TCR-dependent kinase signaling, which activated a Zap70- and LAT-independent pathway. Moreover, LAT-Y136F T cells showed ERK activation that was dependent on Lck and/or Fyn, protein kinase C-θ, and RasGRP1. These data demonstrate a novel route to Ras activation in vivo in a pathological setting.

Cariogenic potential of pediatric liquid medicaments--an in vitro study.

UNLABELLED: Pediatric liquid medicaments (PLM) are popular and are easily accepted by both parents and children. They are widely prescribed and easily available. However the sugar content and properties of these preparations determines their cariogenic potential. AIMS AND OBJECTIVES: This study assessed the pH and viscosity of pediatric liquid medicaments, type and concentration of sugars present in them and their effect on the growth of Streptococcus mutans. METHODOLOGY: PLM included two each of the most commonly prescribed analgesics, antibiotics, nutritional supplements, antitussive and antiepileptic preparations. The endogenous pH was measured using a digital pH meter and the viscosity was measured using a digital Brookefield viscometer. Analysis of sugars (sucrose, glucose and sorbitol) was performed using High Performance Liquid Chromatography. The effect of PLM on Streptococcus mutans was done by ditch plate method. RESULTS: The pH of PLM ranged from 3.70 to 7.04 and viscosity varied from 307.33cP to 2408.33cP. Fifty percent of the PLM contained sucrose, glucose and sorbitol, and sucrose was present in nine of the PLM. The antibiotic preparations showed zones of inhibition against growth of Streptococcus mutans. CONCLUSIONS: The physical properties of Pediatric Liquid Medicaments as well as the type and concentration of sugars present in them can be indicative of their cariogenic potential.

Effect of xylitol, sodium fluoride and triclosan containing mouth rinse on Streptococcus mutans.

INTRODUCTION: Prevention of dental caries is one of the main strategies in contemporary pediatric dental practice. Mouth rinses are widely used as an adjunct to maintain oral hygiene. It is important for these products to be effective and safe for regular use in children. OBJECTIVE: The aim of the study was to investigate the efficacy of a newly introduced xylitol, sodium fluoride and triclosan containing mouth rinse in reducing levels of plaque Streptococcus mutans and to compare it with that of a 0.12% chlorhexidine mouth rinse. MATERIALS AND METHODS: Thirty children were randomly divided into two groups of 15 children each. Group I (study group) was given a mouth rinse containing xylitol (5%), sodium fluoride (0.05%) and triclosan (0.03%) and Group II (control group) was given a chlorhexidine (0.12%) mouth rinse. Both mouth rinses were alcohol free. Mouth rinsing was carried out twice daily, half an hour after breakfast and half an hour following dinner, for a period of 21 days under the supervision of the investigator. RESULTS: In both groups, there was a significant reduction in the mean S. mutans count at the end of 21 days (P < 0.001). No significant difference was observed between the two mouth rinses. CONCLUSION: The use of a low fluoride-xylitol based mouth rinse appears to be a suitable choice for regular use in children.