Does plantar skin abrasion affect cutaneous mechanosensation?

Abstract

In humans, plantar cutaneous mechanoreceptors provide critical input signals for postural control during walking and running. Because these receptors are located within the dermis, the mechanical properties of the overlying epidermis likely affect the transmission of external stimuli. Epidermal layers are highly adaptable and can form hard and thick protective calluses, but their effects on plantar sensitivity are currently disputed. Some research has shown no effect of epidermal properties on sensitivity to vibrations, whereas other research suggests that vibration and touch sensitivity diminishes with a thicker and harder epidermis. To address this conflict, we conducted an intervention study where 26 participants underwent a callus abrasion while an age‐matched control group ( n = 16) received no treatment. Skin hardness and thickness as well as vibration perception thresholds and touch sensitivity thresholds were collected before and after the intervention. The Callus abrasion significantly decreased skin properties. The intervention group exhibited no change in vibration sensitivity but had significantly better touch sensitivity. We argue that touch sensitivity was impeded by calluses because hard skin disperses the monofilament's standardized pressure used to stimulate the mechanoreceptors over a larger area, decreasing indentation depth and therefore stimulus intensity. However, vibration sensitivity was unaffected because the vibrating probe was adjusted to reach specific indentation depths, and thus stimulus intensity was not affected by skin properties. Since objects underfoot necessarily indent plantar skin during weight‐bearing, calluses should not affect mechanosensation during standing, walking, or running.

Relationship between deep and superficial sensitivity assessments and gait analysis in diabetic foot patients

“…By analysing the VPT and using the SWMT, we can assess the dorsal column-medial lemniscal system and identify large fibre neuropathy. 19,55,56 Prior to the assessment of each sensation, the patients were reminded that when they perceived the stimulus, they had to express this verbally. They were reminded of this procedure as many times as necessary during the examination, and we avoided asking if they noticed it every time we stimulated an area, as this could pressure the patients to answer 'yes' and misrepresent the results of the investigation.…”

“…6 (7.1%) of the participants had no treatment for diabetes. 19 A sensory neuropathy evaluation was conducted using different tools on the feet to that end (Table 3).…”

“…15 For this purpose, the Pin-Prick test was used to assess nociception (superficial sensitivity pathway) 16,17 and the deep sensitivity pathway 17 was assessed by exploring the vibration sensation using a 128-Hz Rydel-Seiffer diapason and biothesiometer 18 and light touch-pressure using a Semmes-Weinstein monofilament (SWMT). 14,19 Many studies have confirmed that reduced sensitivity in lower limbs is related to postural and gait disorders, [20][21][22][23][24] but few have studied the correlations between different alterations of sensory modalities and gait parameters. Changes in plantar sensitivity and tactile and vibratory sensitivity in lower limbs have been seen to alter human gait.…”

“…24 The cutaneous plantar surface has been defined as a 'sensory map' with skin receptors providing information about the posture of the body to the central nervous system and playing an important role in maintaining balance during standing and ambulation. 7,19 DPN patients with tactile and vibratory sensitivity impairments have slower gait speed, reduced cadence and shorter step lengths. 26 Modification of the plantar skin sensitivity by means of anaesthesia or cooling has also been seen to cause changes in gait parameters.…”

The case for considering volar skin in a “separate status” for wound healing

“…The same is true for all the suprabasal layers of the volar epidermis, such that according to one study the plantar epidermis is about 6-fold thicker than the epidermis on the dorsal foot ( 13 ). The greatly thickened volar epidermis may be expected to interfere with sensory function since mechanoreceptors in the skin are all located in the dermis, but it has been shown that foot callus thickness does not negatively affect sensitivity toward the types of tactile stimuli typically encountered during standing and walking ( 19 , 20 ). This implies that volar skin must be stiff enough to transmit mechanical forces from the skin surface to the dermal mechanoreceptors with negligible dampening.…”