New Method for Monitoring Partial Weight Bearing (PWB) of Outpatients with an Independent Insole Sensor System.

UNLABELLED: PURPOSE OF THE STUDY Partial weight bearing (PWB) is commonly prescribed post operatively following lower limb fractures and compliance with the weight bearing protocol is an essential element of the rehabilitation. So far it is unknown to what extent patients do comply with PWB during the healing process as instructed by the surgeon. Our aim is to assess a new device for real-time feedback and long-term measurement of PWB of outpatients. The device offers the possibility to monitor the outpatient's activity. The applicability, reliability and validity of the new device should be evaluated. MATERIAL AND METHODS 20 young, healthy subjects complete a course of 500 m that contained several stairs, with a PWB of 15 kg. During the entire test, the axial load, the acceleration and the temperature were measured with a novel insole sensor system. The results were compared with reference measurements performed with a force plate. RESULTS Altogether, the 20 subjects performed 11,106 steps during the completion of the walking circuit. In 23.6% of the steps, the subjects applied a PWB of 10 to 20 kg. In 5.5% of all steps, PWB was superior to 60 kg. The mean bias of the insole was 11,58 N. Limits of agreement were +/- 125 N and the interclass correlation coefficient was r = 0.945. CONCLUSIONS The presented sensor sole might be a useful tool to obtain more precise insight of outpatients' activity and load to the injured limb during the healing process. Furthermore, these results demonstrate that even young and healthy subjects are not able to keep the prescribed PWB. This raises the question, if patients who have been recently operated are able to follow the instructions concerning the PWB.

KEY WORDS: partial weight bearing (PWB), insole sensor system, sensor sole, monitoring, outpatients.