An assessment of co-contraction in reinnervated muscle.

Aim: To investigate co-contraction in reinnervated elbow flexor muscles following a nerve transfer. Materials & methods: 12 brachial plexus injury patients who received a nerve transfer to reanimate elbow flexion were included in this study. Surface electromyography (EMG) recordings were used to quantify co-contraction during sustained and repeated isometric contractions of reinnervated and contralateral uninjured elbow flexor muscles. Reuslts: For the first time, this study reveals reinnervated muscles demonstrated a trend toward higher co-contraction ratios when compared with uninjured muscle and this is correlated with an earlier onset of muscle fatigability. Conclusion: Measurements of co-contraction should be considered within muscular function assessments to help drive improvements in motor recovery therapies.

Neuregulin 1 Drives Morphological and Phenotypical Changes in C2C12 Myotubes: Towards De Novo Formation of Intrafusal Fibres In Vitro.

Muscle spindles are sensory organs that detect and mediate both static and dynamic muscle stretch and monitor muscle position, through a specialised cell population, termed intrafusal fibres. It is these fibres that provide a key contribution to proprioception and muscle spindle dysfunction is associated with multiple neuromuscular diseases, aging and nerve injuries. To date, there are few publications focussed on de novo generation and characterisation of intrafusal muscle fibres in vitro. To this end, current models of skeletal muscle focus on extrafusal fibres and lack an appreciation for the afferent functions of the muscle spindle. The goal of this study was to produce and define intrafusal bag and chain myotubes from differentiated C2C12 myoblasts, utilising the addition of the developmentally associated protein, Neuregulin 1 (Nrg-1). Intrafusal bag myotubes have a fusiform shape and were assigned using statistical morphological parameters. The model was further validated using immunofluorescent microscopy and western blot analysis, directed against an extensive list of putative intrafusal specific markers, as identified in vivo. The addition of Nrg-1 treatment resulted in a 5-fold increase in intrafusal bag myotubes (as assessed by morphology) and increased protein and gene expression of the intrafusal specific transcription factor, Egr3. Surprisingly, Nrg-1 treated myotubes had significantly reduced gene and protein expression of many intrafusal specific markers and showed no specificity towards intrafusal bag morphology. Another novel finding highlights a proliferative effect for Nrg-1 during the serum starvation-initiated differentiation phase, leading to increased nuclei counts, paired with less myotube area per myonuclei. Therefore, despite no clear collective evidence for specific intrafusal development, Nrg-1 treated myotubes share two inherent characteristics of intrafusal fibres, which contain increased satellite cell numbers and smaller myonuclear domains compared with their extrafusal neighbours. This research represents a minimalistic, monocellular C2C12 model for progression towards de novo intrafusal skeletal muscle generation, with the most extensive characterisation to date. Integration of intrafusal myotubes, characteristic of native, in vivo intrafusal skeletal muscle into future biomimetic tissue engineered models could provide platforms for developmental or disease state studies, pre-clinical screening, or clinical applications.

Strategies for Peripheral Nerve Repair.

PURPOSE OF REVIEW: This review focuses on biomechanical and cellular considerations required for development of biomaterials and engineered tissues suitable for implantation following PNI, as well as translational requirements relating to outcome measurements for testing success in patients. RECENT FINDINGS: Therapies that incorporate multiple aspects of the regenerative environment are likely to be key to improving therapies for nerve regeneration. This represents a complex challenge when considering the diversity of biological, chemical and mechanical factors involved. In addition, clinical outcome measures following peripheral nerve repair which are sensitive and responsive to changes in the tissue microenvironment following neural injury and regeneration are required. SUMMARY: Effective new therapies for the treatment of PNI are likely to include engineered tissues and biomaterials able to evoke a tissue microenvironment that incorporates both biochemical and mechanical features supportive to regeneration. Translational development of these technologies towards clinical use in humans drives a concomitant need for improved clinical measures to quantify nerve regeneration.

Characterising cellular and molecular features of human peripheral nerve degeneration.

Nerve regeneration is a key biological process in those recovering from neural trauma. From animal models it is known that the regenerative capacity of the peripheral nervous system (PNS) relies heavily on the remarkable ability of Schwann cells to undergo a phenotypic shift from a myelinating phenotype to one that is supportive of neural regeneration. In rodents, a great deal is known about the molecules that control this process, such as the transcription factors c-Jun and early growth response protein 2 (EGR2/KROX20), or mark the cells and cellular changes involved, including SOX10 and P75 neurotrophin receptor (p75NTR). However, ethical and practical challenges associated with studying human nerve injury have meant that little is known about human nerve regeneration.The present study addresses this issue, analysing 34 denervated and five healthy nerve samples from 27 patients retrieved during reconstructive nerve procedures. Using immunohistochemistry and Real-Time quantitative Polymerase Chain Reaction (RT-qPCR), the expression of SOX10, c-Jun, p75NTR and EGR2 was assessed in denervated samples and compared to healthy nerve. Nonparametric smoothing linear regression was implemented to better visualise trends in the expression of these markers across denervated samples.It was found, first, that two major genes associated with repair Schwann cells in rodents, c-Jun and p75NTR, are also up-regulated in acutely injured human nerves, while the myelin associated transcription factor EGR2 is down-regulated, observations that encourage the view that rodent models are relevant for learning about human nerve injury. Second, as in rodents, the expression of c-Jun and p75NTR declines during long-term denervation. In rodents, diminishing c-Jun and p75NTR levels mark the general deterioration of repair cells during chronic denervation, a process thought to be a major obstacle to effective nerve repair. The down-regulation of c-Jun and p75NTR reported here provides the first molecular evidence that also in humans, repair cells deteriorate during chronic denervation.

Generating intrafusal skeletal muscle fibres in vitro: Current state of the art and future challenges.

Intrafusal fibres are a specialised cell population in skeletal muscle, found within the muscle spindle. These fibres have a mechano-sensory capacity, forming part of the monosynaptic stretch-reflex arc, a key component responsible for proprioceptive function. Impairment of proprioception and associated dysfunction of the muscle spindle is linked with many neuromuscular diseases. Research to-date has largely been undertaken in vivo or using ex vivo preparations. These studies have provided a foundation for our understanding of muscle spindle physiology, however, the cellular and molecular mechanisms which underpin physiological changes are yet to be fully elucidated. Therefrom, the use of in vitro models has been proposed, whereby intrafusal fibres can be generated de novo. Although there has been progress, it is predominantly a developing and evolving area of research. This narrative review presents the current state of art in this area and proposes the direction of future work, with the aim of providing novel pre-clinical and clinical applications.

Evaluation of functional outcomes after brachial plexus injury.

Major nerve injuries such as those of the brachial plexus present a significant challenge for both rehabilitation and evaluation of outcome. With these often complex and multi-faceted injuries, correct selection of outcome measures is important. Healthy nerve function in humans heightens our interactions with the world, creating quality and enjoyment through our experiences of movement and touch. Therefore, assessments should be holistic and representative of all of these features. This article considers the assessment and evaluation of all of the features of nerve injury: sensorimotor, sensation (including that of pain), function and the psychosocial aspects. Current practice is described and combined with clinical experience and research findings to provide suggestions and recommendations for the selection of the most appropriate tools for use with this patient group.

Development of a "Surgical Shadowing Scheme" to improve undergraduate experiences of surgery.

PURPOSE: To establish a sustainable model for a "Surgical Shadowing Scheme" (SSS) and assess how this affects undergraduate attitudes to surgical careers. PATIENTS AND METHODS: Surgeons at university teaching hospitals associated with UCL Medical School and UCL Partners, United Kingdom, were approached for their willingness to participate in the scheme. Medical students were then invited to apply for the scheme, where students were individually matched to operating theater sessions with surgeons in their specialty of choice. Feedback was subsequently obtained, evaluating experiences of the placement and the effect this had on future career aspirations. RESULTS: After running for four consecutive years, approximately 220 students have participated in the scheme across a range of surgical units and specialties. A total of 91.5% of the students were pre-clinical (years 1-3), whilst the remainder were clinical (years 4-6). Fifty-four percent were female and 46% male. Eighty-three percent of the students did not have any previous experience of the specialty that they shadowed, and 67% agreed that participating in the scheme had either "increased" or "strongly increased" their desire to pursue a surgical career. Ninety-four percent said they would "recommend" or "strongly recommend" the SSS to a peer. Over a third of students reported scrubbing-up during their placements and 35% of these directly assisted the lead surgeon. Traditionally male-dominated surgical sub-specialties recruited a high proportion of female students. CONCLUSION: This is the first published example of an established "Surgical Shadowing Scheme" for medical undergraduates. Our SSS has been highly valued by students and indicates that even a single high-quality surgical exposure is sufficient to increase the desire of undergraduates to pursue a surgical career. We hope that this SSS will act as a blueprint for other centers to develop their own shadowing schemes, in turn helping to ensure that surgery continues to inspire and attract the very best candidates for the future.

The Effects of Surgical Antiseptics and Time Delays on RNA Isolated From Human and Rodent Peripheral Nerves.

Peripheral Nerve Injury (PNI) is common following blunt or penetrating trauma with an estimated prevalence of 2% among the trauma population. The resulting economic and societal impacts are significant. Nerve regeneration is a key biological process in those recovering from neural trauma. Real Time-quantitative Polymerase Chain Reaction (RT-qPCR) and RNA sequencing (RNA seq) are investigative methods that are often deployed by researchers to characterize the cellular and molecular mechanisms that underpin this process. However, the ethical and practical challenges associated with studying human nerve injury have meant that studies of nerve injury have largely been limited to rodent models of renervation. In some circumstances it is possible to liberate human nerve tissue for study, for example during reconstructive nerve repair. This complex surgical environment affords numerous challenges for optimizing the yield of RNA in sufficient quantity and quality for downstream RT-qPCR and/or RNA seq applications. This study characterized the effect of: (1) Time delays between surgical liberation and cryopreservation and (2) contact with antiseptic surgical reagents, on the quantity and quality of RNA isolated from human and rodent nerve samples. It was found that time delays of greater than 3 min between surgical liberation and cryopreservation of human nerve samples significantly decreased RNA concentrations to be sub-optimal for downstream RT-qPCR/RNA seq applications (<5 ng/µl). Minimizing the exposure of human nerve samples to antiseptic surgical reagents significantly increased yield of RNA isolated from samples. The detrimental effect of antiseptic reagents on RNA yield was further confirmed in a rodent model where RNA yield was 8.3-fold lower compared to non-exposed samples. In summary, this study has shown that changes to the surgical tissue collection protocol can have significant effects on the yield of RNA isolated from nerve samples. This will enable the optimisation of protocols in future studies, facilitating characterisation of the cellular and molecular mechanisms that underpin the regenerative capacity of the human peripheral nervous system.

Iatrogenic posterior tibial nerve division during a combined anterior ankle arthroscopy with an additional posterolateral portal.

Ankle arthroscopy is an important diagnostic and therapeutic technique in the management of ankle disorders. Nowadays ankle arthroscopy provides good to excellent results (up to 90%) in the treatment of certain intra-articular disorders. Due to the superficial location of ankle joint and the abundance of overlying neurovascular structures, complications reported in ankle arthroscopy are greater than those reported in other joints. We present the first reported case of a complete division of the posterior tibial nerve during an anterior ankle arthroscopy combined with an additional posterolateral portal. This was due to a poorly controlled use of the arthroscopic instruments.

Near-infrared spectroscopy for detection of vascular compromise in paediatric supracondylar fractures.

Children suffering supracondylar fractures of the humerus are at risk of vascular compromise, which is currently assessed clinically, although other modalities such as angiography, pulse oximetry, Doppler ultrasound and magnetic resonance angiography have been used. We sought to ascertain whether tissue haemoglobin oxygenation (StO2) measurement could distinguish between patients with and without clinical vascular compromise following supracondylar fractures of the humerus. We prospectively observed StO2 using near-infrared spectroscopy in 29 paediatric patients with supracondylar fractures requiring operative manipulation. The injured and uninjured volar forearm compartments were monitored immediately before and after fracture reduction. The relationship between StO2 in the injured and uninjured limb, and the presence of pre-operative vascular compromise was assessed. Seven out of 29 children presented with vascular compromise. Patients with clinical vascular compromise had significantly lower pre-reduction StO2 (63.5% ± 15%, mean ± standard deviation), compared to those without compromise (80.9% ± 10%). StO2 normalized following surgery in all children with vascular compromise. These improvements in muscle StO2 were associated, in all patients, with the clinical return of pulses and resolution of neurological symptoms if present. StO2 monitoring can identify patients with clinical vascular compromise, can identify the return of adequate perfusion following operative correction of supracondylar fractures, and may be a useful adjunct to clinical assessment.

Classification of congenital anomalies of the hand and upper limb: development and assessment of a new system.

The Oberg, Manske, and Tonkin (OMT) classification of congenital hand and upper limb anomalies was proposed in 2010 as a replacement for the Swanson International Federation of Societies for Surgery of the Hand classification system, which has been the accepted system of classification for the international surgical community since 1976. The OMT system separates malformations from deformations and dysplasias. Malformations are subdivided according to the axis of formation and differentiation that is primarily affected and whether the anomalies involve the whole limb or the hand plate. This review outlines the development of classification systems and explores the difficulty of incorporating our current knowledge of limb embryogenesis at a molecular level into current systems. An assessment of the efficacy of the OMT classification demonstrates acceptable inter- and intraobserver reliability. A prospective review of 101 patients confirms that all diagnoses could be classified within the OMT system. Consensus expert opinion allowed classification of those conditions for which there is not a clear understanding of the mechanism of dysmorphology. A refined and expanded OMT classification is presented.

An olecranon chondral flap and osteochondral coronoid fracture in a spontaneously reduced elbow dislocation in a child.

Elbow injuries in children are very common and radiographs are often difficult to interpret because of the radiolucency of the cartilaginous anlage and the progressive appearance of multiple secondary ossification centres. Elbow dislocations are rare injuries in children. Coronoid fractures can occur during dislocation or relocation of the elbow and can be the only hallmark of a severe injury. The understanding of the mechanics of these injuries has undergone considerable evolution over the past decade. Intra-articular chondral flap fractures are a traumatic elevation of the hyaline cartilage from the subchondral bone. They are also rare injuries in children but should be included in the differential when examining an injured joint. The infrequency of these injuries provides little opportunity to become accustomed to the radiographic signs. We present a case report of a 4-year-old boy with both an olecranon chondral flap and coronoid cartilaginous fracture after a joint dislocation. We present his plain radiography and MRI with illustrated photographic records of the operative findings. This injury has been little described in the literature and never with such imaging to aid understanding of both the pathology and the injury mechanism.