Clinical implications of the variations of sciatic nerve bifurcation on the popliteal nerve block

[摘要] ENGLISH ABSTRACT: The sciatic nerve (SN) is a major nerve of the lower limb, innervating the posterior thigh, thehip and knee as well as structures below the knee through its branches. The SN division occursin the popliteal fossa (PF) at the level of the knee. However, various studies report greatvariations in the level of division of the SN, ranging between 3.3 and 65.1%. These variationswere suggested as a possible cause in failures of the popliteal block (PB). Therefore, the aimof this study is to describe the level of division of the SN in a South African cohort and toevaluate the success rate of three approaches to the PB. Following the simulation of the PB in22 lower limb specimens, the popliteal fossae of 61 cadavers were dissected and the sciaticnerve properly exposed. The level of division was described and the location and distance between the dye and the nerve measured. Variations represented only 11.48% of cases, similarto textbooks' description (12%). The bifurcation pattern of the SN in this South African cohortwas therefore comparable to the standard one. The distance between the SN and the PC variedbetween 20 mm and 405 mm, with a median of 55 mm, close to 60 – 70 mm found in moststudies. The prevalence of variations was higher in females (ratio F:M=2.78) and 55.56% werebilateral. With the SN dividing in the PF, the simulation predicted a 100% success rate with nodifference between the approaches used. Nevertheless, a higher division of the SN wouldcompromise the success of the block. Overall, the SN division in our study population followsthe normal pattern with a lesser degree of variations (11.48%). The division of the nerve in the PF might ensure a successful block in 95 to 100% of cases, in contrast to cases of highvariations. Nevertheless, a preoperative imagery is strongly recommended, especially in women for early identification of variations to avoid failures of the PB, irrespective of the approach used.

[发布机构] Stellenbosch University