Analgesic effect of etidronate on degenerative joint disease.

In the present study, 80 patients with degenerative joint disease, spondylosis deformans, and/or osteoarthritis of the knee with back or joint pain, especially on movement and strain, were randomly divided into four groups. Group A received no etidronate, while groups B, C and D received 66, 133 and 200 mg/day etidronate, respectively, for 12 months. Every 3 months, after evaluating subjective pain on a visual rating scale (VRS), skin impedance was measured with subjects in a quiet sitting position and with the application of various strains on the spine and knee, including standing up from quiet sitting on a chair, bending forward to flex the spine, squatting to flex the knee, walking 20 paces on a flat floor, ascending 10 stair steps and descending 10 stair steps. A dose related improvement of subjective pain on the VRS with a parallel decrease in the percentage fall in skin impedance was noted. The intra-individual coefficients of variation (CV) of L1-L4 bone mineral density (BMD) on dual-energy X-ray absorptiometry were calculated as a possible index for spondylotic changes before and after treatment as an indication of spondylotic deformity, because no established method is yet available to evaluate such changes objectively. A dose-related decrease in CV of BMD was also noted, parallel to the analgesic effect.

Fall of skin impedance and bone and joint pain.

Pain is a complex neurophysiological and psychological process associated with various electrodermal phenomena, including Galvanic skin response, a fall of resistance to Galvanic current. Because skin impedance, an alternative current counterpart of direct current resistance, is readily measured and is probably more sensitive and stable in reflecting the state of the skin, the relationship between changes in pain and skin impedance was evaluted in the present study. Baseline skin impedance was stable and reproducible within a short time of less than 1 h and on consecutive days with a coefficient of variation of 1%-4%, but it may vary more widely over a longer period of 1 year. Baseline skin impedance gradually rose with advancing age, and females tended to show higher values than males. A highly significant correlation was noted between the percentage fall in skin impedance in response to strain on the joint, such as standing, bending, squatting, walking on a flat floor, and ascending and descending stairs, and pain scores obtained by a visual rating scale according to the Spearman's rank correlation coefficient test. Measurement of the fall in skin impedance may be a useful index of pain-associated somatic changes for a better understanding of the overall manifestations of pain as a step toward to an objective evalution of pain.