Background The grip power is widely used as one of the physical indices indicating the activity of rheumatoid arthritis (RA), as well as hand function. However, its clinical significance has been unknown.
Objectives The objective of this study was to clarify the relationships among the grip power, level of activities of daily living (ADL) and functional disorder at the individual joints.
Methods During the period between July 2011 and August 2012, the grip power was measured in 218 inpatients with RA using a mercury dynamometer, and the independence level (0: impossible, 1: incomplete and not practical, 2: practical but the means thereof are unusual, 3: normal) for 14 ADL items was investigated. For each item, the site with the problem (shoulder, elbow, forearm, wrist, thumb, fingers, lower extremity and trunk) and cause of disability (pain, loss of power, decreased range of motion, abnormal prehensile pattern and fatigue) were investigated by interviewing the patient. There were 32 male and 186 female patients. The average age of the patients was 64.4 years, and average duration of the disease was 13.3 years. Biological therapy was given to 23% of the patients. The average grip power of the right and left hands was used.
Results For all items of the ADL, the grip power increased significantly with the increase in the independence level (p<0.001). The site with a problem was, in order of frequency, the fingers (26.1%), wrist (14.8%) and lower extremity (14.0%). The cause of disability was, in order of frequency, pain (38.8%), loss of power (32.8%) and a decreased range of motion (18.7%). Based on the results of a stepwise regression analysis, the first factor, consisting mainly of “reaching function”, including “hair dressing”, “washing one's body”, “taking on and off one's shoes”, “clipping nails”, “buttoning” etc. was most strongly related to a loss of grip power and problems at the elbow, the shoulder and the wrist. The second factor, consisting mainly of the “prehensile function”, including “opening a plastic bottle”, “opening lids”, “squeezing towels” etc., was most strongly related to a loss of grip power and problems at the wrist and the thumb. The third factor, consisting mainly of “activities involving changing body position and transfer”, including “getting in and out of the bathtub”, “standing and sitting” etc. was most strongly related to aging and problems with the lower extremities and at the elbow and the wrist. In the receiver operating characteristic (ROC) curve, the grip power with the maximal Youden index was 136.5 mmHg (11.8 kg) in the females and 152.5 mmHg (13.5 kg) in the males. The explanatory variables for the grip power in the female patients were aging, a long disease duration, a high disease activity score (DAS) 28, problems at the fingers, the thumb and the elbow, decreased flexion at the shoulder and a decreased range of forearm rotation.
Conclusions The grip power was one of the determinants of the ADL associated with upper extremity function in patients with RA. It was a simple and useful objective index that could be used in patients with multiple joint disorders and sarcopenia.
Thyberg I, Hass UAM, Nordenskiöld U, et al. Activity limitation in rheumatoid arthritis with reduced grip force regardless of sex: The Swedish TIRA project. Arthritis Rheum 2005;53:886-896.
Disclosure of Interest None declared