RESUMEN
BACKGROUND: Motor weakness occurs frequently after piriformis injection and it could put patients at risk of falls. We investigated the appropriate concentration and volume of ropivacaine required to minimize motor dysfunction. METHODS: A total of 120 patients who received piriformis injection were included in this study. Piriformis injections of triamcinolone 10 mg in various concentrations (0.1%, 0.075%) and volumes (8, 10, 12 ml) of ropivacaine were administered in 20 patients, respectively. One hour after the injection, we compared motor function according to the concentrations and volumes of ropivacaine. RESULTS: There were significant differences (P < 0.05) in the occurrence of motor dysfunction according to body mass index (BMI) and the concentration of ropivacaine. No significant differences were found in terms of gender, age, weight, height, or the volume of ropivacaine. Logistic regression analysis showed that the likelihood of motor dysfunction with administration of 0.1% ropivacaine was 58.249 times greater than that with administration of 0.075% concentration (P < 0.001), while BMI did not have a significant effect on motor dysfunction. CONCLUSIONS: According to the results of this study, 0.075% ropivacaine rather than 0.1% ropivacaine is appropriate in terms of reducing motor dysfunction after piriformis injection.