Low effectiveness of prescribed partial weight bearing. Continuous recording of vertical loads using a new pressure-sensitive insole.

To enable objective measurements of weight bearing in hip replacement patients a portable instrument set-up with an on-line registering pressure-sensitive insole was developed. Six men and 9 women, median age 58 (48-67) years, who had been operated on with a cementless or hybrid hip arthroplasty were studied. All patients were independent and functional. A physiotherapist instructed the patients to use crutches in order to support 30% of their body weight. The patients then walked a standardized distance with crutches over five different types of terrain: level, uphill, downhill, upstairs and downstairs. The trial was repeated once. In both men and women most of the steps taken resulted in a load of >30% of body weight. None of the patients managed to comply with the directive, even though five of them thought they did. The type of terrain had no significant influence on the pattern of load. Our findings indicate that the effectiveness of prescribing limited weight bearing is questionable.