Nociception at the diabetic foot, an uncharted territory

Table 1 Early studies of cutaneous pain perception thresholds (pressure, heat) at the diabetic foot, using various, non-standardised methods[29,55,56,57]

Test	Diabetic subjects under study		Healthy	Ref.
	Diabetic foot	Neuropathy	controls
CPPPT	1001	100	0	[29]
CPPPT	1001	631	-	[55]
CPPPT	68	30	2	[56]
Heat	1001	100	0	[29]
Heat	1001	100	0	[57]

Percentages of supranormal results are shown.

¹Above upper limit of measurement. CPPPT: Cutaneous pressure pain perception threshold.

Table 2 Simultaneous measurements of pressure pain perception thresholds at the foot in subjects with and without painless diabetic neuropathy, with and without diabetic foot

Subject populations	Diabetic foot1	Healthy2	PLDN3	DM-controls4
No. of subjects	46	43	13	21
% of subjects with CPPPT > 512 mN at toe skinfold	98%	4%	46%	5%
% of subjects with DPPPT > 1400 kPa at m. abductor hallucis	22%	0%	0%	0%
% of subjects with DPPPT > 1400 kPa at metatarsophalangeal joint	50%	2%	0%	5%

¹With previous or active ulcer/arthropathy;

²Non-neuropathic, healthy;

³PLDN, no ulcer;

⁴Diabetes, no neuropathy, no ulcer. Percent subjects with thresholds above the safety limit of measurement are shown. Adapted from ref. [58-60]. CPPPT: Cutaneous pressure pain perception threshold (512 mN upper limit of measurement); DPPPT: Deep pressure pain perception threshold (1400 kPa upper limit of measurement).

Table 3 Percentages of subjects with active diabetic podopathy (ulcer, arthropathy) according to loss of nociception

Foot morbidity	Degree of loss of nociception			Ref.
	None	Mild/moderate	Severe
	(CPPPT1 approximately 100 mN)	(CPPPT1 < 512 mN)	(CPPPT1 > 512 mN)	[59]
Past/present painless ulcer	0%	0%	100%	[28,59,77,86-101]
Foot ulcer, incidence per year	Approximately 0%-1%	Approximately 6%-15%	Approximately 20%-100%2	[28,77,86-101]
Charcot-foot, prevalence	Approximately 0%	Approximately 0.05%	Approximately 2%	[102]

¹Cutaneous pressure pain perception threshold, pinprick stimulator, upper limit of measurement 512 mN, measured at a plantar digital skinfold;

²Depending on compliance with prophylactic podiatry and/or special footwear. CPPPT: Cutaneous pressure pain perception threshold.