Microcirculation in the foot is augmented by neuromuscular stimulation via the common peroneal nerve in different lower limb postures: a potential treatment for leg ulcers

AIM

Aim of the study was to examine the effects of the geko™ device (a portable electical nerve stimulator) on microcirculatory flow on the dorsum of the foot, and whether this is influenced by lower limb postures and application of a plaster cast.

METHODS

This was a cross-sectional, healthy cohort, open label, physiological response study. In 10 healthy volunteers, aged 19 to 24 years, laser Doppler fluxmetry measurements were made on the dorsum of the foot in four postures: standing (weight bearing and non-weight bearing) and supine lying (with the lower limb horizontal and then elevated). Measurements of flux were made both at rest and during stimulation with the geko™ device applied over the common peroneal nerve, at 1 Hz for 5 minutes in each posture. Repeat measurement were made after the application of a below knee plaster cast. Measures of flux were compared to basal levels assumed to be in supine with limb horizontal, with no cast and an inactive geko™ device.

RESULTS

The geko™ device was effective in increasing microcirculation on the dorsum of the foot in all four postures (mean difference =141%, 95% CI 70%-212%, P=0.001). This effect was more pronounced than that of using a plaster alone (Mean increase in flux of 73%, 95% CI 22%-125%, P=0.01) or variances due to the hydrostatic effects of different postures (mean difference 17-27.6%, P>0.05). There was a 2 to 3 fold increase in flux when stimulation was delivered in combination with the plaster cast.

CONCLUSION

Stimulation using the geko™ device augments microcirculation in the foot. The response is greater in lying and non-weight bearing than weight bearing standing but the most striking effect is when stimulation is combined with a plaster cast. The geko™ offers a potential means of promoting conditions favourable for wound healing, where treatment using compression may be contraindicated, such as arterial/mixed aetiology ulcers.

Neuromuscular electrostimulation viathe common peroneal nerve promotes lower limb blood flow in a below-kneecast: A potential for thromboprophylaxis

Objectives

We aimed to examine the characteristics of deep venous flow in the leg in a cast and the effects of a wearable neuromuscular stimulator (geko; FirstKind Ltd) and also to explore the participants’ tolerance of the stimulator.

Methods

This is an open-label physiological study on ten healthy volunteers. Duplex ultrasonography of the superficial femoral vein measured normal flow and cross-sectional area in the standing and supine positions (with the lower limb initially horizontal and then elevated). Flow measurements were repeated during activation of the geko stimulator placed over the peroneal nerve. The process was repeated after the application of a below-knee cast. Participants evaluated discomfort using a questionnaire (verbal rating score) and a scoring index (visual analogue scale).

Results

The geko device was effective in significantly increasing venous blood flow in the lower limb both with a plaster cast (mean difference 11.5 cm/sec^-1; p = 0.001 to 0.13) and without a plaster cast (mean difference 7.7 cm/sec^-1; p = 0.001 to 0.75). Posture also had a significant effect on peak venous blood flow when the cast was on and the geko inactive (p = 0.003 to 0.69), although these differences were less pronounced than the effect of the geko (mean difference 3.1 cm/sec^-1 (-6.5 to 10)). The geko device was well tolerated, with participants generally reporting only mild discomfort using the device.

Conclusion

The geko device increases venous blood flow in the lower limb, offering a potential mechanical thromboprolylaxis for patients in a cast.

Cite this article: Bone Joint Res 2013;2:179–85.

Detection of latent tuberculosis in immunosuppressed patients with autoimmune diseases: performance of a Mycobacterium tuberculosis antigen-specific interferon assay

OBJECTIVE

To analyse the performance of a new M. tuberculosis-specific interferon gamma (IFNgamma) assay in patients with chronic inflammatory diseases who receive immunosuppressive drugs, including tumour necrosis factor alpha (TNFalpha) inhibitors.

METHODS

Cellular immune responses to the M. tuberculosis-specific antigens ESAT-6, CFP-10, TB7.7 were prospectively studied in 142 consecutive patients treated for inflammatory rheumatic conditions. Results were compared with tuberculin skin tests (TSTs). Association of both tests with risk factors for latent M. tuberculosis infection (LTBI) and BCG vaccination were determined and the influence of TNFalpha inhibitors, corticosteroids, and disease modifying antirheumatic drugs (DMARDs) on antigen-specific and mitogen-induced IFNgamma secretion was analysed.

RESULTS

126/142 (89%) patients received immunosuppressive therapy. The IFNgamma assay was more closely associated with the presence of risk factors (odds ratio (OR) = 23.8 (95% CI 5.14 to 110) vs OR = 2.77 (1.22 to 6.27), respectively; p = 0.009), but less associated with BCG vaccination than the TST (OR = 0.47 (95% CI 0.15 to 1.47) vs OR = 2.44 (0.74 to (8.01), respectively; p = 0.025). Agreement between the IFNgamma assay and TST results was low (kappa = 0.17; 95% CI 0.02 to 0.32). The odds for a positive IFNgamma assay strongly increased with increasing prognostic relevance of LTBI risk factors. Neither corticosteroids nor conventional DMARDs significantly affected IFNgamma responses, but the odds for a positive IFNgamma assay were decreased in patients treated with TNFalpha inhibitors (OR = 0.21 (95% CI 0.07 to 0.63), respectively; p = 0.006).

CONCLUSIONS

These results demonstrate that the performance of the M. tuberculosis antigen-specific IFNgamma ELISA is better than the classic TST for detection of LTBI in patients receiving immunosuppressive therapy for treatment of systemic autoimmune disorders.

Association of a syndrome resembling Wegener's granulomatosis with low surface expression of HLA class-I molecules

BACKGROUND

Granulomatous syndromes, such as Wegener's granulomatosis, are defined according to complex criteria, but the underlying cause is rarely identified. We present evidence for a new aetiology for chronic granulomatous lesions associated with a recessive genetic defect, which is linked to the human leucocyte antigen (HLA) locus.

METHODS

Five adults with necrotising granulomatous lesions in the upper respiratory tract and skin, associated with recurrent bacterial respiratory infections and skin vasculitis, were identified. A diagnosis of Wegener's granulomatosis was considered in all of them, but abandoned because of an incompatible disease course and resistance to immunosuppressive treatments. Peripheral-blood samples were taken and analysed by immunohistochemistry and fluorescent-activated-cell-sorter analysis. Since all five patients were homozygous for the HLA locus, we looked for genetic defects located within the HLA-locus with PCR and restriction fragment length polymorphism.

FINDINGS

A severe decrease in cell-surface expression of HLA class-I molecule was seen in all patients. Defective expression of the transporter associated with antigen presentation (TAP) genes was responsible for the HLA class-I down-regulation, and in two patients we identified a mutation in the TAP2 gene responsible for the defective expression of the TAP complex. We showed the presence of autoreactive natural killer (NK) cells and gammadelta T lymphocytes in the peripheral blood cells of two patients. Correction of the genetic defect in vitro restored normal expression of HLA class-I molecules and prevented self-reactivity in the patients' cells. Histology of granulomatous lesions showed the presence of a large proportion of activated NK cells.

INTERPRETATION

Our findings define the cause and pathogenesis of a new syndrome that affects patients with a defective surface expression of HLA class-I molecules. The syndrome resembles Wegener's granulomatosis both clinically and histologically. Patients have chronic necrotising granulomatous lesions in the upper respiratory tract and skin, recurrent infections of the respiratory tract, and skin vasculitis. A predominant NK population within the granulomatous lesions suggests that the pathophysiology of the skin lesions may relate to the inability of HLA class-I molecules to turn off NK cell responses. Accurate genetic analysis of a defined syndrome can provide a better understanding of the cause and pathogenesis of a disease.