The human metacarpophalangeal joint: quantification of stiffness and the effects of treatment

Abstract

A horizontal finger arthrograph has been developed to measure stiffness in the human metacarpophalangeal joint of the index finger. Data from the arthrograph has been shown to have reasonable reproducibility. Stiffness is quantified in terms of dissipated energy, equilibrium position and absolute resistive torque measured from the equilibrium position. Three groups of experiments are reported. The first investigates the circadian variation of stiffness in normal subjects. The second investigates stiffness in normal subjects and patients with rheumatoid arthritis and the third looks at the effects of various techniques of physiotherapy in altering stiffness. The results show a circadian variation of stiffness with increased stiffness in the early hours of the morning. Male subjects exhibit higher dissipated energy than female subjects though no statistically significant differences could be found in other stiffness parameters. Within the range of values tested no statistically significant differences could be found between controls and patients in dissipated energy, resistive torque or equilibrium position. Correlation of these characteristics with other parameters, for example, grip strength and limb circumference has identified differences between controls and patients, and it is concluded that, in rheumatoid arthritis, stiffness mainly results from the involvement of immediate soft tissue periarticular structures. The effects of physiotherapeutic techniques, usually administered to alleviate stiffness, are shown to be variable. Short wave diathermy and ultrasound effected a reduction in dissipated energy in the patient group and it is concluded that a reduction in the viscous and frictional properties of periarticular structures produces this effect. A shift in the equilibrium position is also shown to occur in this group following the application of short wave diathermy. Paraffin wax baths, ice and exercises had no effect on stiffness in the patient group and no treatment technique produced significant effects in the control group.