Evaluation of pressure pain sensitivity in the forefoot of healthy individuals

Abstract

Background: The evaluation of musculoskeletal pain in podiatric medical practice is mainly based on anamnesis and manual examination. However, when manual palpation is performed, the digital pressure necessary to adequately explore the different structures of the foot is unknown. We evaluated the pressure pain threshold in forefoot structures to determine the intensity and duration of the stimulus as clinically relevant and representative.

Methods: In a transversal analytical study of 15 healthy individuals, 16 forefoot points were explored with a handheld pressure palpometer calibrated to exert maximum pressing force of 1.0 or 2.0 kilogram-force (kgf) applied during 5 or 10 sec. The combinations of the different pressures and intervals were selected randomly. Participants had to self-rate the pressure pain sensitivity of each stimuli on a 100-mm horizontal line (0–100 numeric rating scale), setting the pain threshold to 50 (100 being pain as bad as it could be). Likewise, aftersensation and referred pain patterns were recorded.

Results: All participants indicated painful stimuli at some of the 16 forefoot points studied in the experimental protocol when pressure was applied with the 2.0-kgf palpometer; 53.3% showed evidence of pain at any forefoot point when the 1.0-kgf palpometer was used. The odds of evoking a painful sensation are 9.8 times higher when using a 2.0-kgf palpometer versus a 1.0-kgf palpometer. In addition, referred sensations were observed with a significantly higher frequency when applying the 2.0-kgf palpometer.

Conclusions: Bone and soft structures show differences in pressure sensitivity, increasing significantly when applying higher pressure force. Soft structures, specifically intermetatarsal spaces, showed the lowest pain pressure thresholds. More research is needed to better understand pressure pain response.