GROSS DIMENSIONAL ASSESSMENT OF CUTANEOUS WOUNDS AS AN INDICATOR OF HEALING: IMPORTANCE OF CAREFUL CONSIDERATION

Sir:

Cutaneous wounds originating in the context of various daily scenarios, e.g. trauma, surgical interventions, call for efficient management strategies in order to reduce patient discomfort, tissue morbidity and economical burden imposed to health systems. Experimental studies evaluating or comparing the effectiveness of therapeutic modalities utilise different assessment methods, which can be categorised as gross clinical evaluation, quantitative/qualitative histological examinations, mechanical evaluation and physiological and biochemical approaches 1, 2, 3, 4, 5. Gross dynamic dimensional assessment (GDDA) of the healing procedure through sequential measurement of wound dimensions is used more frequently due to its application both in human and animal studies and due to the possibility of extrapolation and generalisation of research outcomes to true clinical situations (3). The lower cost and ease of manipulation are additional advantages of gross quantitative assessment (3).

GDDA is performed by successive measurements of wound length, width, depth, area or volume or a combination of these indices unified via mathematical formulations (6). Regardless of the specific mathematical approach in GDDA, the velocity of centripetal movement of wound periphery determines the relative competence of wound closure in a given time period and quantified to a certain numerical value (6). Reestablishment of macroscopical anatomical integrity of cutaneous wounds is accomplished via collaborative and synchronised action of contraction and reepithelialisation 7, 8. Wound contraction accounts for approximately 20–30% reduction in wound size in humans and 80–90% in animals with mobile skin like rats 9, 10. Considering the ultimate goal of the healing procedure, which is restoration of functional and anatomical properties closely mimicking that of original unwounded tissue, epithelialisation conforms to the this general concept, while contraction collides it (7).

During early stages of healing, fibrin clot forms, and besides its several biological functions, helps maintain the initial mechanical integrity of the injured tissue. However, the cascade of events occurring after clot formation is highly complicated and meanwhile interesting. Epithelialisation advances underneath the clot, thus producing a ‘transient pseudolag effect’, whereby epithelial proliferation is masked by superficial clot until shedding of it. Consequently, during early stages of healing procedure, to be more precise prior to the sloughing of clot, GDDA measures the dynamic changes in cutaneous wound dimensions resulting from contraction. However, the scenario gets more complex considering the fact that contraction and thus wound closure is affected by clot. Contraction procedure exerts a certain amount of compressive stress to the wounded area and tensile stress to the adjacent normal tissue owing to the stiffness of wound clot and resistant nature of it 11, 12. A part of these strains would be dissipated due to the irreversible deformation of the tissue over time, the so‐called viscous strain (13). However, elastic strain would be maintained. The amount of this viscous strain is proportional to the exerted contractile forces (13). Since various therapeutic approaches influence the contraction procedure, any reinforcing or inhibitory impacts that affect the amount of contractile forces and thus viscous/elastic strain ratio may result in partially biased interpretations of GDDA results during the transient pseudolag phase. After sloughing of the clot, a sudden increase in closure velocity would be registered due to the simultaneous release of accumulated elastic strain and unmasking of the underlying regenerated epithelium. Taken together, the internal validity of GDDA as an indicator of cutaneous wound healing may be questioned. Also, the extrapolation of these results for different mammalian genus and various wound types may be considered an important source of bias.