Percent articular exposure of the distal humerus with triceps fascial tongue approach compared with olecranon osteotomy.

BACKGROUND: Distal humerus fractures are common and can be difficult to treat. No one approach to the distal humerus has been shown to be superior to another; however, the olecranon osteotomy remains the gold standard for complex, intra-articular fractures. Understanding the percent of articular exposure with approaches to the distal humerus is important for success. The goal of this study is to show the percent of articular exposure of the triceps fascial tongue approach as compared with the olecranon osteotomy. METHODS: Twelve fresh frozen cadavers were separated randomly into 2 groups of 6 each. The first group of 6 specimens was allocated to the triceps fascial tongue approaches with the collaterals maintained and with the collaterals released off the ulna and elbow dislocated. The second group of 6 was allocated to the triceps fascial tongue approach while maintaining the collaterals followed by an olecranon osteotomy. The articular exposure was marked after performing each approach, and the percent of articular exposure was quantified by using 3D scanning. Standard deviations were calculated for each. RESULTS: The average percent visualization of the distal humerus articular surface in the fascial tongue approach while maintaining the collaterals was 36% in the first cohort and 37% in the second cohort with a standard deviation of 5% in both cohorts. The average percent of the distal humerus articular surface exposed in the fascial tongue approach with the collaterals released off the ulna and elbow dislocated was 85.09% with a standard deviation of 4%. The average percent of the distal humerus articular surface exposed in the olecranon osteotomy group was 57.9% with a standard deviation of 5%. CONCLUSION: The triceps fascial tongue approach allows for visualization of about one-third of the joint, which may be adequate for many intra-articular distal humerus fractures. For added exposure of the articular surface, the collaterals may be elevated from the ulna and the elbow dislocated allowing for a substantial increase in percent of articular exposure compared with the collateral retaining fascial tongue approach and the olecranon osteotomy.

Mapping the subcellular distribution of α-synuclein in neurons using genetically encoded probes for correlated light and electron microscopy: implications for Parkinson's disease pathogenesis.

Modifications to the gene encoding human α-synuclein have been linked to the development of Parkinson's disease. The highly conserved structure of α-synuclein suggests a functional interaction with membranes, and several lines of evidence point to a role in vesicle-related processes within nerve terminals. Using recombinant fusions of human α-synuclein, including new genetic tags developed for correlated light microscopy and electron microscopy (the tetracysteine-biarsenical labeling system or the new fluorescent protein for electron microscopy, MiniSOG), we determined the distribution of α-synuclein when overexpressed in primary neurons at supramolecular and cellular scales in three dimensions (3D). We observed specific association of α-synuclein with a large and otherwise poorly characterized membranous organelle system of the presynaptic terminal, as well as with smaller vesicular structures within these boutons. Furthermore, α-synuclein was localized to multiple elements of the protein degradation pathway, including multivesicular bodies in the axons and lysosomes within neuronal cell bodies. Examination of synapses in brains of transgenic mice overexpressing human α-synuclein revealed alterations of the presynaptic endomembrane systems similar to our findings in cell culture. Three-dimensional electron tomographic analysis of enlarged presynaptic terminals in several brain areas revealed that these terminals were filled with membrane-bounded organelles, including tubulovesicular structures similar to what we observed in vitro. We propose that α-synuclein overexpression is associated with hypertrophy of membrane systems of the presynaptic terminal previously shown to have a role in vesicle recycling. Our data support the conclusion that α-synuclein is involved in processes associated with the sorting, channeling, packaging, and transport of synaptic material destined for degradation.

Deconstructing complexity: serial block-face electron microscopic analysis of the hippocampal mossy fiber synapse.

The hippocampal mossy fiber (MF) terminal is among the largest and most complex synaptic structures in the brain. Our understanding of the development of this morphologically elaborate structure has been limited because of the inability of standard electron microscopy techniques to quickly and accurately reconstruct large volumes of neuropil. Here we use serial block-face electron microscopy (SBEM) to surmount these limitations and investigate the establishment of MF connectivity during mouse postnatal development. Based on volume reconstructions, we find that MF axons initially form bouton-like specializations directly onto dendritic shafts, that dendritic protrusions primarily arise independently of bouton contact sites, and that a dramatic increase in presynaptic and postsynaptic complexity follows the association of MF boutons with CA3 dendritic protrusions. We also identify a transient period of MF bouton filopodial exploration, followed by refinement of sites of synaptic connectivity. These observations enhance our understanding of the development of this highly specialized synapse and illustrate the power of SBEM to resolve details of developing microcircuits at a level not easily attainable with conventional approaches.

Investigating synapse formation and function using human pluripotent stem cell-derived neurons.

A major goal of stem-cell research is to identify conditions that reliably regulate their differentiation into specific cell types. This goal is particularly important for human stem cells if they are to be used for in vivo transplantation or as a platform for drug development. Here we describe the establishment of procedures to direct the differentiation of human embryonic stem cells and human induced pluripotent stem cells into forebrain neurons that are capable of forming synaptic connections. In addition, HEK293T cells expressing Neuroligin (NLGN) 3 and NLGN4, but not those containing autism-associated mutations, are able to induce presynaptic differentiation in human induced pluripotent stem cell-derived neurons. We show that a mutant NLGN4 containing an in-frame deletion is unable to localize correctly to the cell surface when overexpressed and fails to enhance synapse formation in human induced pluripotent stem cell-derived neurons. These findings establish human pluripotent stem cell-derived neurons as a viable model for the study of synaptic differentiation and function under normal and disorder-associated conditions.

A Novel Technique for a Successful Closed Reduction of a Bosworth Fracture-Dislocation of the Ankle.

The Bosworth fracture is defined as a bimalleolar fracture-dislocation of the ankle, with entrapment of the fibula behind the posterior tubercle of the distal tibia. In the current orthopedic literature, not only is this fracture pattern rare, but this type of fracture-dislocation has also been reported to be near impossible to close reduce, with the majority requiring early open reduction and internal fixation to prevent complications and poor clinical outcomes. Reported early complications include compartment syndrome and soft tissue complications from repeated closed reduction attempts. Complications associated with delayed operative intervention include post-traumatic adhesive capsulitis of the ankle and ankle stiffness. We present a case study of a 34-year-old male who sustained a Bosworth fracture-dislocation of the right ankle after a skateboarding accident. We describe a successful closed reduction performed in the emergency department, with a novel closed reduction technique. The patient tolerated the procedure well, with no complications. He was then scheduled for open reduction and internal fixation five days afterward, and upon post-operative follow-up, he recovered well with no complications. This technique focuses on reduction forces applied to the proximal fibular fragment, which is entrapped behind the posterolateral portion of the tibia. We believe that the key to successful reduction is applying an anterolateral/internal rotation force to this entrapped fragment. If successful, this fracture pattern may not require admission for compartment checks or early open reduction and internal fixation, thereby preventing complications and poor clinical outcomes. Our technique allows for a successful closed reduction of Bosworth fractures; however, further research exploring this reduction technique is warranted.