Tips and pitfalls of reduction and fixation in displaced supracondylar fractures in children

Supracondylar humeral fractures are the most common injury of the elbow in children. Compared to flexion type fractures, extension type fractures are more common, up to 98%. Gartland classification has been used to guide the management of this injury, which is based on the extent of the displacement. If not adequately managed, completely displaced (type III) fractures may have a higher incidence of concomitant injury or complications, including neurovascular injury, compartment syndrome, or cubitus varus. Closed reduction followed by percutaneous pinning has been suggested as the standard operative method for the displaced supracondylar humeral fractures. However, these fractures can be challenging to reduce, with the traditional technique of closed reduction. Lateral-entry pinning is known as a sufficient method of fixation for this injury. However, the lateral pin only fixation technique may also result in loss of reduction in some particular patterns of fractures, such as fractures with medial column comminution. We discuss and describe the reduction techniques of completely displaced supracondylar humeral fractures, including technical tips and pitfalls for closed reduction and open reduction. We also discuss indications of medial pinning, and its safe method, when the lateral-entry pins may not achieve adequate stability.

Structural basis of substrate recognition and translocation by human ABCD1

Human ATP-binding cassette (ABC) subfamily D transporter ABCD1 can transport CoA esters of saturated/monounsaturated long/very long chain fatty acid into the peroxisome for β-oxidation. Dysfunction of human ABCD1 causes X-linked adrenoleukodystrophy, which is a severe progressive genetic disorder affecting the nervous system. Nevertheless, the mechanistic details of substrate recognition and translocation by ABCD1 remains obscure. Here, we present three cryo-EM structures of human ABCD1 in distinct functional states. In the apo-form structure of 3.53 Å resolution, ABCD1 exhibits an inward-facing conformation, allowing the lateral entry of substrate from the lipid bilayer. In the 3.59 Å structure of substrate-bound ABCD1, two molecules of C22:0-CoA, the physiological substrate of ABCD1, is symmetrically bound in two transmembrane domains (TMDs). Each C22:0-CoA adopts a L-shape, with its CoA portion and acyl chain components bound to two TMDs respectively, resembling a pair of strings that pull the TMDs closer, resultantly generating a narrower outward-facing conformation. In the 2.79 Å ATP-bound ABCD1 structure, the two nucleotide-binding domains dimerize, leading to an outward-facing conformation, which opens the translocation cavity exit towards the peroxisome matrix side and releases the substrates. Our study provides a molecular basis to understand the mechanism of ABCD1-mediated substrate recognition and translocation, and suggests a unique binding pattern for amphipathic molecules with long acyl chains.

Nesting behavior of the Elegant Euphonia (Euphonia elegantissima, Aves: Fringillidae) in urban and suburban sites of east Mexico

Between 2005, 2014–2017, we studied six Elegant Euphonia (Euphonia elegantissima) nests from two sites (urban and suburban) in the city of Xalapa, Veracruz. They were located in a macadamia tree crown, under epiphytic bromeliads, and under hanging fern and Euphorbia pots. The two nests we extracted and measured (7.2 x 7.5 x 5.6 cm; 10.1 x 8.6 x 11 cm), were closed and globular, with a lateral entry and mainly made of plant fibers, leaves, and cobwebs. Our observations included nest construction, egg incubation and chick care (nestling phase). Nest construction took at least 10–11 days, while egg incubation took 14–18 days. Incubation was done by the female in all but one observation, and the male escorted the female to the nest on every occasion. Time of incubation sessions ranged from 36–88 min (mean = 62 min) with shorter out nest sessions (3–18 min, mean = 9 min). There were three eggs in two of the nests, and in one only two eggs hatched; four chicks were observed in another nest. The nestling phase lasted 20 days in two nests, with the male spending more time (35–300 s, mean = 109 s) than the female taking care of the chicks (25–99 s, mean = 53 s). Reciprocal escorting was observed during the nestling phase, with the male always arriving first. Breeding occurred in January, April, May (two nests), June, and July. Observing the male of the Elegant Euphonia escorting the female during the incubation period, corroborates previous observations of this behavior in genera Euphonia and Chlorophonia. Incubation and nestling time periods were similar to other species of these genera.

Structural basis of substrate recognition and translocation by human ABCA4

Human ATP-binding cassette (ABC) subfamily A (ABCA) transporters mediate the transport of various lipid compounds across the membrane. Mutations in human ABCA transporters have been described to cause severe hereditary disorders associated with impaired lipid transport. However, little is known about the mechanistic details of substrate recognition and translocation by ABCA transporters. Here, we present three cryo-EM structures of human ABCA4, a retina-specific ABCA transporter, in distinct functional states at resolutions of 3.3–3.4 Å. In the nucleotide-free state, the two transmembrane domains (TMDs) exhibit a lateral-opening conformation, allowing the lateral entry of substrate from the lipid bilayer. The N-retinylidene-phosphatidylethanolamine (NRPE), the physiological lipid substrate of ABCA4, is sandwiched between the two TMDs in the luminal leaflet and is further stabilized by an extended loop from extracellular domain 1. In the ATP-bound state, the two TMDs display a closed conformation, which precludes the substrate binding. Our study provides a molecular basis to understand the mechanism of ABCA4-mediated NRPE recognition and translocation, and suggests a common ‘lateral access and extrusion’ mechanism for ABCA-mediated lipid transport.

Radiation Exposure in The Treatment of Pediatric Supracondylar Humerus Fractures: Comparison of Two Fixation Methods

Aim: The study aims to determine the estimated radiation exposure of two different types of fixation (crossed vs lateral-entry K-wires) for displaced supracondylar fractures at a Major Trauma Centre in London. Methods: A retrospective review was performed between 2015 and 2019 in children (<16 years old) who underwent either Closed Reduction and Percutaneous Pinning (CRPP) or open reduction and K wire fixation for a displaced supracondylar fracture (Gartland II, III and IV) of the humerus. Results: The overall mean radiation dose and duration with crossed K-wire fixation was statistically lower when compared with two lateral K-wires. The mean radiation dose increased with increasing Gartland Grade - for Gartland Grades II, III and IV respectively. Conclusion: The current study showed statistically significant decreased radiation dose in crossed K-wire fixation method, compared to lateral-entry fixation. No difference was found regarding the cosmetic/functional outcome when Flynn’s criteria were applied.

Biomechanical Analysis of Sagittal Plane Pin Placement Configurations for Pediatric Supracondylar Humerus Fractures

Anterior to posterior (AP) pinning is the recommended sagittal pin configuration in divergent lateral entry coronal pinning of pediatrics supracondylar fractures. However, there was still a lack of evidence regarding alternative sagittal pins configurations. We aimed to compare the construct stiffness of alternative sagittal pin configurations by using synthetic bone models. Sixty synthetic pediatric humeri were osteotomized to create a supracondylar fracture. After the fracture reduction, all specimens were fixed in the coronal plane with divergent lateral entry pin configurations in four different patterns in the sagittal plane: AP, crossed, divergent and parallel sagittal pin configuration. Each configuration was tested with five loading patterns. The AP sagittal pin had significantly lower construct stiffness than the divergent (p = 0.003) and the parallel sagittal pin configuration (p = 0.005) in external rotation loading tests. The divergent sagittal pin had the highest construct stiffness in extension, valgus, and external rotation loads, but the parallel sagittal pin had lower construct stiffness under extension load than the divergent and crossed sagittal pin configurations. The divergent sagittal pin configuration provides greater construct stiffness than other sagittal pin configurations due to the maximal pin spreading distance at the fracture site and the pin angle lock mechanism.

Structural basis of substrate recognition and translocation by human ABCA4

Human ATP-binding cassette (ABC) subfamily A (ABCA) transporters mediate the transport of various lipid compounds across the membrane. Mutations in human ABCA transporters have been described to cause severe hereditary disorders associated with impaired lipid transport. However, little is known about the mechanistic details of substrate recognition and translocation by ABCA transporters. Here, we present three cryo-EM structures of human ABCA4, a retinal-specific ABCA transporter, in distinct functional states at resolutions of 3.3-3.4 Å. In the nucleotide-free state, the two transmembrane domains (TMDs) exhibited a lateral-opening conformation, allowing the lateral entry of substrate from the lipid bilayer. N-retinylidene-phosphatidylethanolamine (NRPE), the physiological lipid substrate of ABCA4, is sandwiched between the two TMDs in the luminal leaflet and is further stabilized by an extended loop from extracellular domain 1. In the ATP-bound state, the two TMDs displayed an unprecedented closed conformation, which precludes the substrate binding. Our study provides a molecular basis to understand the mechanism of ABCA4-mediated NRPE recognition and translocation, and suggests a common ‘lateral access and extrusion’ mechanism for ABCA-mediated lipid transport.

Lateral Recruitment in Civil Services: Standing the Test of Merit

Keeping bureaucracy, the permanent executive, insulated from the influence of the political executive has always been the focus of administrative reforms. A transparent and fair system of recruitment based on meritocracy is a key to shield administrators from political influence. This article analyses the essential conditions required for the successful implementation of lateral recruitment in India. It contends that merit, involving transparent and fair processes in recruitment, is the bedrock of any efficient bureaucratic system. The article does not probe deeper into the question as to whether the lateral entry should be introduced or not, but assuming the lateral entry is a desirable practice for modern civil administration, it discusses the conditions that lead to its success or failure. It draws lessons for India from an exercise that already took place in its neighbouring country, Pakistan.

Accuracy and Safety of Customized Stereotactic Fixtures for Stereoelectroencephalography in Pediatric Patients

Stereoelectroencephalography (SEEG) in children with intractable epilepsy presents particular challenges. Their thin and partially ossified cranium, specifically in the temporal area, is prone to fracture while attaching stereotactic systems to the head or stabilizing the head in robot’s field of action. Postponing SEEG in this special population of patients can have serious consequences, reducing their chances of becoming seizure-free and impacting their social and cognitive development. This study demonstrates the safety and accuracy offered by a frameless personalized 3D printed stereotactic implantation system for SEEG investigations in children under 4 years of age. SEEG was carried out in a 3-year-old patient with drug-resistant focal epilepsy, based on a right temporal-perisylvian epileptogenic zone hypothesis. Fifteen intracerebral electrodes were placed using a StarFix patient-customized stereotactic fixture. The median lateral entry point localization error of the electrodes was 0.90 mm, median lateral target point localization error was 1.86 mm, median target depth error was 0.83 mm, and median target point localization error was 1.96 mm. There were no perioperative complications. SEEG data led to a tailored right temporal-insular-opercular resection, with resulting seizure freedom (Engel IA). In conclusion, patient-customized stereotactic fixtures are a safe and accurate option for SEEG exploration in young children.