| BACKGRUUNDSkin graft and tangential excision are considered to be reliable and effective operative techniques for various wound care.With the application of Negative Pressure Wound Therapy,skin graft has been using more frequently for wound repair.Skin grafts are classified as split-thickness and full-thickness skin according to the depth of skin harvest.More elaborate classification of split-thickness skin in depth was processed in accordance with the requirements of various wound closure and donor site healing.Inadequate depth of skin harvest would induce donor site healing disorder such as scar formation,pigmentation,itching,pain and other morbilities.The selection of depth is also a common and important issue in operative treatment of burn wounds.According to the classic three-quarter-dividing method of evaluation,burn wound were classified as superficial burn(1st degree),superficial partial-thickness burn(superficial 2nd degree),deep partial-thickness burn(deep 2nd degree)and full-thickness burn(3rd degree).Because of indeterminate depth,tangential excision is used as main operative treatment of deep partial-thickness burn wound.Tangential excision removes necrotic tissue while preserving as much of the underlying viable tissue as possible.So,thickness of tangential excision is crucial to the wound care.However,it is difficult to process an ideal thickness excision,and there is no objective criteria to evaluate the procedure.How to improve selection and evaluation of thickness is still important to wound care.High-frequency ultrasound technique,with high resolution and micron measuring accuracy,can clearly show the depth of the skin tissue with no invasion.Dermascope,also known as skin light transmission microscope,can observe the surface condition of skin and visualize subepidermal structure through polarization and non-polarization light modes.The combination of high-frequency ultrasound and dermoscope detection is speculated to judge both thickness and tissue vitality exactly.The aim of the present study is to establish stable and convenient models of the donor site and excision of deep second-degree burn in rats and to verify the potential value of dermoscopy and high-frequency ultrasound detection in wound evaluation.OBJECTIVE1.To establish a model of donor site and a model of deep second-degree burn wound after tangential excision in rats.2.To explore the possible application of high-frequency ultrasound in detection of thickness in both donor site skin and second degree burn wounds.3.To summerize the characteristics of dermoscopy images of split-thickness donor site wound and second degree burn wound after tangential excision.METHODPart 1.In first part,20 Sprague-Dawley rats were randomly divided into 2 groups(skins were harvested with a roller knife or a motor knife).Ten rats were used in each group.Four donor sites were set on the back of SD rats.After subcutaneous injection of swelling fluid,the skin was harvested in depth of 0.1 mm,0.2 mm,0.3 mm,and 0.4 mm respectively.Before and after skin harvest,the digital camera was used to record the general morphology;the dermoscope was used to acquire wound images.The image features including color,hemorrhage,and capillary morphology were observed,summarized and analyzed later comprehensively.Skin thickness was measured with high-frequency ultrasound apparatus.Wound specimens were taken for histological pathological examination.The relationship of all the detective data,image and histological information was analyzed subsequently.Part 2.Twenty Sprague-Dawley rats were randomly divided into 2 groups(roller knife or motorized knife)and 10 in each group.Four deep partial-thickness burn wounds on the back of each rat were induced through 8-second direct contact of boiling water immersed copper block.Burn wounds were tangential excised at depths of 0.1 mm,0.2 mm,0.3 mm,and 0.4 mm respectively.The pathological examination and detection of dermoscope and ultrasound were processed later,and data relationship was analyzed.The above mentioned procedures in part one were also proceeded in this study.Data were analyzed with the use of SAS 9.4 statistical software.RESULTS:Part 1.A total of 40 wounds with different depths were obtained,10 in each group.One of them was too deep with the subcutaneous fascia exposure.The remaining had a regular appearance and good uniformity of morphology.Image Features of Dermoscopy: wound images after 0.1mm scale skin harvesting showed pink white with scattered point bleeding.The density of bleeding point in 0.2mm wound was much higher than the former,and capillary distal showed hair-like distribution.After the 0.3mm skin was taken,the dense reticular structure was clearly visible,with a large distribution of bleeding points,visible capillary blood vessels.After the 0.4 mm skin was removed,large diffusive hemorrhage,capillaries and the subcutaneous fascia were obviously visible.Statistic analyzes showed positive correlation between the pathological depth and high-frequency ultrasound data.Among them,the epidermis correlation coefficient was 0.836 P<0.01;the dermis correlation coefficient was 0.932 P<0.01;Intact skin was 0.855 P<0.01.Part 2.Forty wounds with different depths of tangential excision were obtained,10 in each group.Among them,2 of the wounds were excised too deep and the subcutaneous fascia was exposed.The remaining 38 wounds were well created.Image Features of Dermoscopy: After 0.1mm excision,the wound surface is pale and a mesh-like shape is clearly visible.After 0.2mm excision,the wound surface was typically white and red,with visible scattered and regular point-liked vessels and partially visible reticular capillary lines.Most of the wounds appear pale red after 0.3mm tangential excision,with more density of bleeding points,extensive capillary ends and vascular lines distribution than the former.As for the 0.4mm excision wounds,the surfaces presented bright-red color,with diffuse bleeding and invisible capillary integrity.Statistic analyze showed the pathological thickness is positively correlated with the ultrasound examination.The pathological results and ultrasound image calculation results are relatively stable,and the variability is small.Ultrasound image calculations are greater than the pathological results.CONCLUSION1.With the use of roller knife,stable model of split-skin donor site and tangential excision wound after deep second-degree burns can be produced in SD rats.2.The results of high-frequency ultrasonographic measurement of the thickness of the split-skin and tangential excision of deep second-degree burns wound are positively correlated with those of pathological measurements.High-frequency ultrasonography can provide real-time,non-invasive detection and reference for personalized,accurate skin harvesting and tangential excision.3.Dermoscopy can show comprehensive information of the wound surface,which would provide an accurate and objective evaluative method in skin harvesting and tangential excision procedures. |
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