Partial weight bearing after surgery for fractures of the lower extremity--is it achievable?

Partial weight bearing is a generally accepted principle of rehabilitation following trauma or reconstructive surgery of the lower extremity. Individual dynamic loads during partial weight bearing to a given load level of 200 N were compared in 23 patients who had sustained a fracture of the lower extremity and 11 healthy volunteers using dynamic sole pressure measurements. Excessive dynamic loading compared with the statically pre-tested 200 N level was observed in all groups. Maximum force levels were up to 690 N in young patients and up to 580 N elderly patients beyond the prescribed static load. None of the healthy volunteers was able to keep within the given load of 200 N. The set load level was exceeded by at least 38 N (119%) in the elderly patient group. In comparison, elderly patients showed statistically significantly higher maximum forces than young patients during the first two test days (p=0.007 and 0.013). On the 3rd test day the maximum ground contact forces were on average 71 N higher than in the young patients group. Analysis of the force time integrals (impulses transferred to the ground) displayed higher values in the older again than in young patients. The differences were statistically significant during the first two test days (p=0.006 and 0.037). This study implies that the conventional concept of postoperative partial weight bearing starting from 200 N and a stepwise increase of the load level until full weight bearing is not valid during clinical practice.

Effects of attention and precision of exerted force on beta range EEG-EMG synchronization during a maintained motor contraction task.

OBJECTIVE: The present study was aimed at investigating the effect of attention and precision level of exerted force on beta range EEG-EMG synchronization. METHODS: We simultaneously recorded cortical electrical activity (EEG) in a bipolar manner from the contralateral sensorimotor areas and surface electromyographic (EMG) activity from the flexor digitorum superficialis muscle in 10 healthy subjects during a maintained motor contraction task at 8% of the maximal voluntary contraction (MVC) force level. The coherence between oscillatory processes in the EEG and EMG was calculated. Three different conditions were investigated: (i) performing the task with high precision (HP); (ii) performing the task with high precision and simultaneously performing a mental arithmetic task (HPAT), i.e. attention was divided between the motor task and the mental arithmetic task; and (iii) performing the task with low precision (LP). RESULTS: We have found that the amount of beta range EEG-EMG synchronization decreases below the 95% confidence level when attention is divided between the motor task and the mental arithmetic task. The results also show that the frequency of beta range synchronization is higher with a higher level of precision but still lies within the beta frequency range (15-30 Hz). CONCLUSIONS: The data indicate that beta range synchronization represents a state of the cortico-muscular network when attention is directed towards the motor task. The frequency of synchronization of this network is associated with, and possibly encodes, precision in force production.