This digest summarises recent key papers published in the areas of pressure ulcers, skin integrity, diabetic foot ulcers and venous leg ulcers.

Pressure Ulcers
The effects of deformation, ischemia, and reperfusion on the development of muscle damage during prolonged loading

• Deep tissue injury (DTI) is a severe form of pressure ulcer in subcutaneous tissue layers, such as skeletal muscle, underneath intact skin. Tissue damage only becomes apparent at an advanced stage.
• Compression-induced ischaemia is traditionally considered to be the most important factor in the aetiology of DTI. More recently, other theories have been proposed, including ischaemia-reperfusion (I-R) injury, impaired lymphatic drainage and sustained tissue deformation.
• In this study the contributions of deformation, ischaemia and reperfusion to the development of skeletal muscle damage were examined in 16 rats during a six-hour period.
• Ischaemia caused a gradual homogeneous increase in T2 (a biological parameter used to distinguish between tissue types). Increased T2 was considered a measure of tissue damage involving oedema, necrosis, or inflammation.
• In deformation tests a variable T2 increase was observed reflecting the significant variation in deformation and ischaemia between experiments. These results imply that deformation, ischaemia and reperfusion all contribute to the damage process during prolonged loading, although their importance varies with time.
• The authors conclude that the rapid initiation and subsequent progression of DTI can be prevented by using appropriate cushioning to keep internal tissue deformations below the deformation threshold for damage. For prolonged loading, it is important to limit the period of ischaemia by repositioning strategies and pressure-relieving mattresses to prevent tissue damage related to ischaemia or I-R injury.

Loerakker S, Manders E, Strijkers GJ et al. The effects of deformation, ischaemia, and reperfusion on the development of muscle damage during prolonged loading. J Appl Physiol 2011; doi:10.1152/japplphysiol.00389.2011

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Leg Ulcers
Duration of wound fluid secretion from chronic venous leg ulcers is critical for interleukin-1α, interleukin-1β, interleukin-8 levels and fibroblast activation

• The aim was to find the optimal conditions for wound fluid collection by focusing on samples collected at different times of the day and in varying durations.
• Retentive hydrophobic polyurethane foam beneath an adhesive film dressing was used to collect prototypic cytokines (interleukin (IL)-1α, IL- 1β), a chemokine
• (IL-8) and proteinases (matrix metalloproteinase
• [MMP]-9) in 23 patients with chronic venous leg ulcers. The bioactivity of one-hour and 24-hour wound fluids and serum was also compared.
• In the first cohort (n=11), collection of wound fluids was performed over three days in each patient for three consecutive eight-hour intervals; 24 hours with the foam; or 24 hours without the foam. In the second cohort (n=12), wound fluids that accumulated for one and 24 hours were compared.
• There were no significant temporal changes in the levels of the four proteins when comparing three consecutive eight-hour intervals starting from 0800 that in turn did not differ significantly with the 24-hour collection levels. IL-1α, IL-1β and IL-8 levels were higher (p<0.05) in the 24-hour collection compared with one-hour wound fluids, whereas MMP-9 levels were insensitive to the length of collection.
• The length of collection is critical when monitoring cytokine/chemokine and bioactivity levels of chronic wound fluid. This suggests that the removal of accumulating unfavourable factors in chronic wound fluid may be important in wound management.

Zillmer R, Trøstrup  H,  Karlsmark T et al. Duration of wound fluid secretion from chronic venous leg ulcers is critical for interleukin-1α, interleukin-1β, interleukin-8 levels and fibroblast activation. Arch Dermatol Res 2011; doi: 10.1007/s00403-011-1164-6  

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Skin Integrity
The effect of aqueous cream BP on the skin barrier in volunteers with a previous history of atopic dermatitis

• The emollient aqueous cream BP is frequently used for the treatment of atopic dermatitis (AD) even though it is associated with a high rate of adverse cutaneous reactions. This study investigated the effect of aqueous cream BP on stratum corneum (SC) integrity and skin barrier function.
• Thirteen volunteers with a previous history of AD (but with no symptoms for six months) applied aqueous cream BP twice daily to the volar side of one forearm for four weeks. Permeability barrier function and SC integrity were determined before and after treatment by measuring trans-epidermal water loss (TEWL) in conjunction with tape-stripping to damage the SC experimentally. For comparison, 13 volunteers with current AD were recruited for assessment of SC integrity and skin barrier function at unaffected and untreated sites.
• Topical application of aqueous cream BP on the asymptomatic volunteers resulted in significant elevation of baseline TEWL and a decrease in SC integrity, bringing their results closer to the increased level observed in the volunteers with active disease.
• Aqueous cream BP used as a leave-on emollient caused severe damage to the skin barrier in volunteers with a previous history of AD making it similar to the level seen during active disease.  The authors conclude that aqueous cream BP should not be used as a leave-on emollient in patients with AD.

SG Danby, Al-Enezi T, Sultan A et al. The effect of aqueous cream BP on the skin barrier in volunteers with a previous history of atopic dermatitis. Br J Dermatology 2011; 165: 329–334

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Diabetic Foot Ulcers
Foot and shoe size mismatch in three different New York City populations

• The aim of this study was to determine the proportion of adults who were unaware of their own shoe size in three different New York City populations — a foot specialist’s private practice, an academic diabetic foot and ankle clinic, and a charity care centre serving homeless people.
• A shoe size mismatch was defined as a difference of at least 0.5cm in size between the measured foot and the shoe size.
• The study involved 235 adults who had not had any previous foot or ankle surgery, had no active foot or ankle ulcer or any shoe orthotics. Of these, 43 (18.3%) had a history of diabetes.
• A significant difference in the prevalence of the measured foot and shoe size mismatch (by at least one size) was found between the cohort from the private practice (15.5%) compared with both the diabetic foot and ankle clinic (42.5%) and the homeless charity clinic (43.5%) (p<0.001 and P=0.003 respectively). A significant difference was also detected (p<0.05) between the private practice and the homeless cohort when a difference of at least 1.5 sizes was present between the measured foot and the shoe size.
• Ill-fitting shoes were used by 34.9% of the patients. Some patients could need a different shoe size for each foot.
• The findings suggest that proper footwear sizing is lacking among a large proportion of patients. Proper shoe size is an important element of foot health, especially in older people and in those with diabetes. The necessity of wearing correctly sized shoes is essential, especially for patients who have a high risk of developing foot ulcers.

Schwarzkopf R, Perretta DJ, Russell TA et al. Foot and shoe size mismatch in three different New York City populations. J Foot Ankle Surg (2011) 50: 391–394

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