[Sacral Skin Elasticity - Establishing a Non-Invasive Mechanical Method for Measurement]

Some patients with sacral scars, e. g. those developing after pilonidal sinus surgery, report discomfort when sitting or putting strain on the scars. In order to establish objective criteria for the assessment of this kind of discomfort and for the evaluation of scar quality after various types of surgical interventions, it is of interest to provide a method which enables physicians to assess skin quality in the sacral region. For this purpose, we developed a mechanical, non-invasive, fast and cost-neutral method for the measurement of skin distensibility and mobility. We examined a healthy sample of 100 study participants to establish benchmark values for scar-free skin in the sacral region and to identify the factors which impact skin quality, e. g. age, weight and sex.

With the participant in a standing position, 4 vertically arranged measurement points, which are exactly spaced in cranial to caudal direction by 10 mm-100 mm-10 mm, are marked in the lumbar and sacral region, respectively. The participant is then asked to bend forward and - with arms and legs fully stretched on both sides - to touch both their patellae with the balls of their hands so that the distance between the measurement points can be measured in this position as well. Then, with the participant standing upright again, another measurement is taken to establish the distance by which the lowest point can be manually moved in cranial direction.

The sacral-lumbar skin distension quotient (lumbar skin distension / sacral skin distension×100), which can easily be calculated from the measurements, is independent of age and BMI and has a standard range of about 80-93%. Sacral skin mobility ranges from 11 to 18 mm, but is slightly negatively influenced by a high BMI.

By comparing lumbar and sacral skin distension in the same study participant, we are able to obtain intraindividually valid findings about possible changes in skin and scar quality. Owing to the lack of known published data about sacral skin elasticity, the proposed measurement method, while restricted to a number of special cases, seems to be practicable and independent of the patient's general condition. Compared with devices that have been used for the measurement of elasticity in other skin areas, our procedure is generally available and cost-neutral.