The design and application of microprocessor based systems for clinical measurement of joint stiffness and grip strength.

Abstract

The overall aim of the project was to further the research into the objective measurement of the symptoms of arthritic disease. There were three major parts to this study. The first part was to design a measurement system capable of making large scale, objective measurements of the stiffness of the human metacarpophalangeal joint. The second part was to design a new device to measure the grip strength of the human hand objectively. The last part was to use these two measurement systems to conduct research into the clinical manifestations of arthritic disease and study the effects of some therapeutic agents. A new, microcomputer controlled arthrograph system was developed to measure the stiffness of the metacarpophalangeal joint of the index finger. The system proved to be reliable, easy to use and sufficiently accurate to quantify changes in joint stiffness. A new design of grip machine was produced which enabled the forces developed during a power grip to be analysed. Measurement was made of the force contributions of individual digits and the maximum total gripping force. The machine was portable and extremely easy to use. A study of the circadian variation of joint stiffness and grip strength, over a full twenty four hour period, was carried out. Measurements were made every two hour in both healthy and arthritic subjects. A circadian variation of stiffness was observed in the joints of arthritic subjects. Joint stiffness was elevated in the early morning and for some subjects the degree of change was profound. No significant circadian variation was observed in the joint stiffness of healthy subjects. A circadian variation of grip strength was observed in arthritic subjects. Grip strength reached a minimum value between 2.00 and 4.00 a.m. in the majority of subjects. No consistent relationship was found between changes in joint stiffness and changes in grip strength. The effect of several forms of physiotherapy on the joint stiffness of arthritic subjects was studied in both the short and long term. The subjects were measured before, and then immediately after, treatment each time they visited a physiotherapy hand clinic. Only the results of those patients who attended the clinic for a minimum of five weeks were used in any subsequent analysis. Four different treatments were studied: hot wax and ultrasound, hot wax alone, ultrasound alone and exercise. The combination of hot wax baths and ultrasonic therapy effected temporary reductions in all joint stiffness parameters. The reductions in energy dissipation and torque range were highly significant ( p < 0.05 and p < 0.001 respectively ). No significant reductions were found for hot wax, ultrasound alone or exercise. In the long term, no significant change in joint stiffness was found for any of the treatments considered.