A new concept for evaluating muscle function in the lower extremities in cases of low back pain syndrome in anamnesis.

INTRODUCTION There are difficulties in objective evaluation of activity of the muscles in the lower extremities of patients after successful treatment of sciatica and pseudosciatica, when no clear clinical symptoms are detected. However, the existence of some muscle dysfunction can be hypothesised and its detection was the aim of the study. OBJECTIVE Recordings from chosen lower extremity muscles during standing were performed as supplementary differential diagnosis in evaluation of these patients. EMG in standing positions constitutes a new methodological approach not described in detail. METHODS Twenty patients (11 after sciatica and 9 after sciatica-like episodes) were enrolled into the study. On the day of examination, clinical and electroneurographical (ENG; M and F waves tests) studies showed no pathology. The percentage of maximal voluntary contraction (MVC) defined muscle activity during standing. Mean amplitude and number of changes in muscle activity (fluctuations) were measured in surface electromyography recordings (sEMG) during normal standing and tandem positions. RESULTS AND CONCLUSIONS Activity of proximal lower extremity muscles expressed as percentage of MVC was bilaterally increased in patients after sciatica in normal standing position, compared with results from the group of healthy volunteers (N=9). Patients after sciatica were also characterized with a significant increase of mean sEMG amplitude, recorded especially in distal muscles on the affected side during tandem position. This pathological change was related to decrease in 'fluctuations' frequency in patients after sciatica (P<0.001) more than after pseudosciatica (P<0.01) groups in both standing positions, compared to parameters of healthy volunteers. Sciatica and pseudosciatica in anamnesis cause different abnormal patterns of lower extremity muscle activity during standing positions when recorded with surface EMG.