Pressure pain thresholds at the diabetic Charcot-foot: an exploratory study.

Objective: Painless mechanical trauma is believed to induce neuroosteoarthropathy at the neuropathic foot in diabetes (diabetic Charcot-foot). To investigate pressure nociception at the diabetic foot, we measured the pain perception thresholds for deep pressure (DPPPT, using Algometer II®) and cutaneous pressure (CPPPT, using calibrated monofilaments).

Methods: In 24 diabetic patients with painless neuropathy (11 with a chronic, inactive Charcot-foot and a history of foot ulcer, and 13 control patients who never had an ulcer), and in 20 healthy subjects, CPPPT (at palmar and plantar digital skinfolds) and DPPPT (over musculus abductor pollicis, musculus hallucis longus, and over metacarpophalangeal and metatarsophalangeal joints) was measured.

Results: At the hands, DPPPT and CPPPT were similar in patients and healthy subjects. At the feet, CPPPT was above the upper safety limit of measurement (512 mN) in 2/20 healthy subjects, and in 11/11 Charcot patients compared to 6/13 neuropathic controls (p=0.005). At the feet, median DPPPT was similar in all groups. In Charcot patients only, DPPPT was higher over metatarsophalangeal joint than over m. hallucis longus (p=0.048).

Conclusion: Perception thresholds for cutaneous pressure pain, but not for deep pressure pain, may be extremely elevated at the diabetic neuropathic foot, and particularly at the Charcot-foot.