Review
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Diabetes. Apr 15, 2015; 6(3): 391-402
Published online Apr 15, 2015. doi: 10.4239/wjd.v6.i3.391
Nociception at the diabetic foot, an uncharted territory
Ernst A Chantelau
Ernst A Chantelau, Diabetic Foot Clinic, Heinrich-Heine-University Düsseldorf, 40001 Düsseldorf, Germany
Author contributions: Chantelau EA solely contributed to this article.
Conflict-of-interest: None.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Ernst A Chantelau, Professor, Diabetic Foot Clinic, Heinrich-Heine-University Düsseldorf, Moorenstraße 5, 40001 Düsseldorf, Germany. chantelau@gmx.de
Telephone: +49-421-637196
Received: July 23, 2014
Peer-review started: July 25, 2014
First decision: September 16, 2014
Revised: September 18, 2014
Accepted: January 18, 2015
Article in press: January 20, 2015
Published online: April 15, 2015
Abstract

The diabetic foot is characterised by painless foot ulceration and/or arthropathy; it is a typical complication of painless diabetic neuropathy. Neuropathy depletes the foot skin of intraepidermal nerve fibre endings of the afferent A-delta and C-fibres, which are mostly nociceptors and excitable by noxious stimuli only. However, some of them are cold or warm receptors whose functions in diabetic neuropathy have frequently been reported. Hence, it is well established by quantitative sensory testing that thermal detection thresholds at the foot skin increase during the course of painless diabetic neuropathy. Pain perception (nociception), by contrast, has rarely been studied. Recent pilot studies of pinprick pain at plantar digital skinfolds showed that the perception threshold was always above the upper limit of measurement of 512 mN (equivalent to 51.2 g) at the diabetic foot. However, deep pressure pain perception threshold at musculus abductor hallucis was beyond 1400 kPa (equivalent to 14 kg; limit of measurement) only in every fifth case. These discrepancies of pain perception between forefoot and hindfoot, and between skin and muscle, demand further study. Measuring nociception at the feet in diabetes opens promising clinical perspectives. A critical nociception threshold may be quantified (probably corresponding to a critical number of intraepidermal nerve fibre endings), beyond which the individual risk of a diabetic foot rises appreciably. Staging of diabetic neuropathy according to nociception thresholds at the feet is highly desirable as guidance to an individualised injury prevention strategy.

Keywords: Foot ulcer, Neuroarthropathy, Insensitivity to pain, Pain perception, Diabetes mellitus, Amputation, Diabetic neuropathy

Core tip: The diabetic foot is characterised by painless ulcers and/or arthropathy. Although painless diabetic neuropathy is known as the underlying condition, little is known quantitatively about the pain evoked by noxious stimuli (nociception) at the diabetic foot. Preliminary evidence shows that pinprick pain perception threshold at plantar digital skinfolds is supranormal, beyond the upper limits of measurement. It is suggested that measuring nociception at the foot in diabetes could specify the individual risk of painless ulcers and/or arthropathy and, thereby, provide the basis of an individualised graded injury prevention strategy.