A new method for measuring motor block in the lower extremities.

A method for determining muscle strength in the lower extremities was developed and its clinical application evaluated in ten elderly, healthy subjects, and also subsequently in one of them during spinal anaesthesia. With the subject lying in the lithotomy position on a modified operating table, muscle strength measurements were made during flexion of the hip, extension of the knee and plantar flexion of the big toe. The electromechanical performance of the apparatus was stable, and the maximum measurement errors observed at loads of 245 and 49 N were 4 and 11% of the deflections, respectively. The subjects underwent repeated muscle strength measurements during a 4-h period without any difficulty. No signs of muscular fatigue were observed. The variation of the measured isometric muscle strength was small and the average coefficient of variation roughly 10%. In the patient receiving spinal anaesthesia, the degree of motor block was determined, and the results are presented graphically. This new method for evaluation of motor block in the lower extremities is a reliable quantitative method for bilateral, three-joint muscle strength measurements, which is also applicable during regional anaesthesia.