Abstract

The aim of this new diagnostic method is to ensure a complete evaluation of the neuromuscular properties immediately after (6-8 weeks) knee surgery. In addition, a technical has been developed to allow the function of knee proprioceptors to be measured after surgery using EMG and vibratory stress of the subsultory type. Twenty-nine patients were examined after knee joint surgery, together with a group of 14 healthy subjects who acted as controls. Tests comprised a knee extension assessment, without external loading. Foot extension speed was recorded using an encoder and then used to calculate the mechanical potential. At the same time the electromyographic activity of two leg extensor muscles (lateral and medial vastus) was synchronised; the two limbs were evaluated separately. The second consisted of the electromyographic recording of external leg muscles, before and after the administration of subsultory vibratory stress. For this purpose, each subject was positioned in a half squat on a vibratory platform, guided at 40 Hz for 30s. EMG registration was performed 30s before and during the vibrations. In operated subjects, the limb undergoing surgery showed 13% less mechanical power than the healthy limb (p<0.001). This was accompanied by a parallel reduction in EMG (p<0.05). No statistically significant differences were found between the two limbs in the control group. The perturbations induced by vibrations generated an increase in electromyographic activity compared to basal conditions both in the control group and operated patients. In the latter this was statistically higher in the operated limb compared to the healthy limb, whereas the mean values of both limbs were similar in the control group. The functional recovery of the operated limb, expressed as a ratio of mechanical power between the operated/healthy limb, showed a statistically significant correlation (r=0.61, p<0.01) with the period of time after surgery. In conclusion, these new methods have allowed the functional capacity of some proprioceptors to be measured in operated limbs. This showed that although operated limbs underwent a complete recovery of neuromuscular capacity, when a voluntary movement guided by CNS was requested, the proprioceptive response capacity did not always showed signs of a full recovery. Verf.-Referat