The Peripheral Lymphatic System Is Impaired by the Loss of Neuronal Control Associated with Chronic Spinal Cord Injury.

Spinal cord injury (SCI) is associated with venous vascular dysfunction below the level of injury, resulting in dysregulation of tissue fluid homeostasis in afflicted skin. The purpose of this study was to determine whether loss of neuronal control in chronic SCI also affects the skin lymphatic system. Morphology of lymphatics was characterized by immunohistochemistry and lymphatic gene expression profiles determined by DNA microarray analysis. In SCI, skin lymphatic function appeared to be impaired, because the ratio of functionally dilated versus collapsed lymphatic vessels was decreased 10-fold compared with control. Consequently, the average lumen area of lymphatic vessels was almost halved, possibly due to the known impaired connective tissue integrity of SCI skin. In fact, collagenases were found to be overexpressed in SCI skin, and dermal collagen structure was impaired. Molecular profiling also suggested an SCI-specific phenotype of increased connective tissue turnover and decreased lymphatic contractility. The total number of lymphatic vessels in SCI skin, however, was doubled, pointing to enhanced lymphangiogenesis. In conclusion, these data show, for the first time, that lymphatic function and development in human skin are under neuronal control. Because peripheral venous and lymphatic vascular defects are associated with disturbed fluid homeostasis, inappropriate wound healing reactions, and impaired skin immunity, they might contribute to the predisposition of afflicted individuals to pressure ulcer formation and wound healing disorders.

Cellular and molecular changes that predispose skin in chronic spinal cord injury to pressure ulcer formation.

Patients with spinal cord injury have a predisposition to develop pressure ulcers. Specific characteristics of the patients' skin potentially involved have not yet been identified. The purpose of this investigation was to determine whether loss of neuronal control affects cellular and molecular homeostasis in the skin. Intact afflicted skin, wound edge of pressure ulcers, and control skin were analysed. Platelets, transforming growth factor-ß1, and activin A were identified by immunohistochemistry. Transforming growth factor-ß-like activity was determined by bioassay, and gene expression by DNA microarray analysis or RT-PCR. In afflicted skin, enhanced platelet extravasation was detected. Transforming growth factor-ß1 and activin A accumulated in the dermal-epidermal junction zone. Transforming growth factor-ß-like activity and activin A expression were increased in intact afflicted skin (compared to control skin) and were further enhanced in pressure ulcers. In vitro, activity was generated by fibroblast-epithelial cell interactions, which also induced activin A. Thus, loss of neuronal control in spinal cord injury appears to trigger inappropriate wound healing processes in the patients' skin. Plasma leakage and increased transforming growth factor-ß-like activity combined with shear forces potentially enhance the risk for pressure ulcer formation.

Long-term decoding of movement force and direction with a wireless myoelectric implant.

OBJECTIVE: The ease of use and number of degrees of freedom of current myoelectric hand prostheses is limited by the information content and reliability of the surface electromyography (sEMG) signals used to control them. For example, cross-talk limits the capacity to pick up signals from small or deep muscles, such as the forearm muscles for distal arm amputations, or sites of targeted muscle reinnervation (TMR) for proximal amputations. Here we test if signals recorded from the fully implanted, induction-powered wireless Myoplant system allow long-term decoding of continuous as well as discrete movement parameters with better reliability than equivalent sEMG recordings. The Myoplant system uses a centralized implant to transmit broadband EMG activity from four distributed bipolar epimysial electrodes. APPROACH: Two Rhesus macaques received implants in their backs, while electrodes were placed in their upper arm. One of the monkeys was trained to do a cursor task via a haptic robot, allowing us to control the forces exerted by the animal during arm movements. The second animal was trained to perform a center-out reaching task on a touchscreen. We compared the implanted system with concurrent sEMG recordings by evaluating our ability to decode time-varying force in one animal and discrete reach directions in the other from multiple features extracted from the raw EMG signals. MAIN RESULTS: In both cases, data from the implant allowed a decoder trained with data from a single day to maintain an accurate decoding performance during the following months, which was not the case for concurrent surface EMG recordings conducted simultaneously over the same muscles. SIGNIFICANCE: These results show that a fully implantable, centralized wireless EMG system is particularly suited for long-term stable decoding of dynamic movements in demanding applications such as advanced forelimb prosthetics in a wide range of configurations (distal amputations, TMR).

Acquisition of myoelectric signals to control a hand prosthesis with implantable epimysial electrodes.

The acquisition of myoelectric signals from the Musculus deltoideus of a rhesus monkey is described. Such signals are aimed to be used as control signal for an active myoelectric hand prosthesis. For recording, implantable flexible, polyimide-based multi-site microelectrodes were placed epimysially on the muscle. EMG signals were recorded during voluntary goal-directed movements of the arm, and analyzed with respect to signal amplitude and frequency.

Use of the reverse latissimus muscle flap for closure of complex back wounds in patients with spinal cord injury.

STUDY DESIGN: Our study was designed as a retrospective review of spinal cord patients with complex back wounds in whom the reverse latissimus muscle flap was used for closure. OBJECTIVES: The objective was to evaluate the efficacy and outcomes in these patients. SUMMARY OF BACKGROUND DATA: Earlier publications give only anecdotal reports on the treatment of complex back wounds in patients with spinal cord syndrome. The data so far available do not allow any comparison of the various methods used. METHODS: Fourteen patients with congenital or acquired spinal cord syndrome and with an average age of 31.2 years (range 12-76 years) had complex back wounds in the thoracic and lumbar regions, which were closed in each case with a reverse latissimus dorsi muscle flap. The patients had deep wound infection and wound dehiscence following spondylodesis (n = 6), dead space and wound dehiscence following laminectomy (n = 6), or decubitus ulcers over the spine (n = 2). The spinal cord syndrome was chronic in nine patients and acute in five. The pre- and postoperative treatment and the actual operation were all done in a spinal cord injury center. In nine patients, the back wound was closed in a primary procedure, and in five, a split-thickness skin graft was used to close it. In 11 patients, primary wound healing was achieved with no complications after closure, whereas in 3 patients, complications with the back wound or the donor site led to disturbances of wound healing lasting up to 25 weeks. Five operations had to be performed specifically because of these complications. RESULTS: At follow-up 27.4 months (mean; range 8-114 months) after the operation, all back wounds were closed, free of irritation, and completely healed. The patients did not report any handicaps in everyday life, loss of strength in the upper extremities, or functional restrictions. One patient had a deep vein thrombosis in one leg. No further complications linked with the spinal cord syndrome were ascertained. The instrumentation used during the spondylodesis operation was left in place in four cases. The spondylodesis became solidly fused in each of these cases. CONCLUSION: Use of the reverse latissimus muscle flap is a reliable method of closing complex back wounds in patients with spinal cord syndrome. Should there be complications in the area of the flap, secondary wound healing can be achieved by wound debridement and closure of the wound by means of split-thickness skin grafting. There is no loss of function in the upper extremities. The complications typically seen in spinal cord patients can be avoided when the treatment is carried out in the conditions that obtain in a specialized spinal cord injury center.