Abnormalities of somatosensory perception in patients with painful osteoarthritis normalize following successful treatment.

To investigate the effect of chronic nociceptive pain on somatosensory perception, quantitative sensibility testing was performed in the most painful area and the homologous contralateral side in 14 patients with painful osteoarthritis of the hip. Twelve patients were reassessed in a painfree state 6-14 months following surgery. Von Frey filaments were used to test low-threshold mechanoreceptive function. Pressure pain sensitivity was assessed with a pressure algometer and thermal sensitivity with a Thermotest. Sex- and age-matched controls were examined in the corresponding areas at similar time intervals. There was no statistically significant difference between groups in the sensitivity to light touch and innocuous cold in either session. Compared to controls, patients had increased sensitivity to pressure pain in the most painful area (p < 0.002), bilaterally increased sensitivity to innocuous warmth (p < 0.03), cold pain (p< 0.05) and a tendency toward bilaterally increased sensitivity to heat pain (p = 0.054) before surgery. In the painful area, patients' sensitivity to pressure pain decreased (p < 0.04) and, remaining within normal limits, sensitivity to light touch increased (p < 0.006) compared to values prior to surgery. No statistically significant differences between the groups were seen following surgery, indicating that the sensibility changes had been maintained by chronic nociceptive pain.