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

Mady-Goma, Chancy Rosine (2018-12)

Thesis (MSc)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: The sciatic nerve (SN) is a major nerve of the lower limb, innervating the posterior thigh, the hip and knee as well as structures below the knee through its branches. The SN division occurs in the popliteal fossa (PF) at the level of the knee. However, various studies report great variations in the level of division of the SN, ranging between 3.3 and 65.1%. These variations were suggested as a possible cause in failures of the popliteal block (PB). Therefore, the aim of this study is to describe the level of division of the SN in a South African cohort and to evaluate the success rate of three approaches to the PB. Following the simulation of the PB in 22 lower limb specimens, the popliteal fossae of 61 cadavers were dissected and the sciatic nerve 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, similar to textbooks’ description (12%). The bifurcation pattern of the SN in this South African cohort was therefore comparable to the standard one. The distance between the SN and the PC varied between 20 mm and 405 mm, with a median of 55 mm, close to 60 – 70 mm found in most studies. The prevalence of variations was higher in females (ratio F:M=2.78) and 55.56% were bilateral. With the SN dividing in the PF, the simulation predicted a 100% success rate with no difference between the approaches used. Nevertheless, a higher division of the SN would compromise the success of the block. Overall, the SN division in our study population follows the 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 high variations. 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.

AFRIKAANSE OPSOMMING: N. ischiadicus is 'n hoof senuwee in die onderste ledemaat, wat die posterior kompartement van die dy, en die heup en knie voorsien, asook strukture onder die knie deur takke afkomstig vanaf die senuwee. Verdeling van n. ischiadicus vind plaas in die popliteale fossa (PF) op die vlak van die knie. Verskeie studies toon egter ʼn groot aantal variasies, wat wissel tussen 3.3% en 65.1%, ten opsigte van die vlak van verdeling van die senuwee. Daar is voorgestel dat hierdie variasies moontlik die oorsaak van mislukte toediening van ʼn popliteale blok (PB) kan wees. Die doel van hierdie studie is dus om die vlak van verdeling van n. ischiadicus in 'n Suid-Afrikaanse kohort te beskryf, en die voorkoms van sukses ten opsigte van drie benaderings tot die toediening van ʼn PB te evalueer. Na simulasie toediening van ʼn PB in 22 onderste ledemaatmonsters, is die popliteale fossa in 61 kadawers oopgedissekteer en n. ischiadicus blootgelê. Die vlak van verdeling is beskryf, en die ligging van die kleurstof en afstand tussen die kleurstof en die senuwee bepaal. Variasies het slegs in 11.48% van die gevalle voorgekom, vergelykbaar met gemiddelde aanduidings in handboeke (12%). Die bifurkasie patroon van n. ischiadicus in hierdie Suid-Afrikaanse kohort is dus vergelykbaar met die aanvaarde standaarde. Die afstand tussen n. ischiadicus en die popliteale plooi (PC) wissel tussen 20 en 405 mm, met 'n mediaan van 55 mm, in vergelyking met 60 tot 70 mm in die meeste studies. Die voorkoms van variasies was hoër by vroue as by mans (verhouding V : M = 2.78 : 1), en in 55.56% was die voorkoms van variasies bilateraal. Met verdeling van n. ischiadicus in die PF, het simulasie van ʼn PB 'n 100% voorspelde suksessyfer, met geen verskil ten opsigte van die benadering wat gebruik word nie. 'n Hoër verdeling van n. ischiadicus kan die toediening van ʼn PB moontlik nadeling beïnvloed. Oor die algemeen volg die verdeling van n. ischiadicus in ons studiepopulasie die normale patroon met 'n lae voorkoms van variasies (11.48%). Verdeling van die senuwee in die PF kan 'n suksesvolle blok in 95 tot 100% van gevalle waarborg, in teenstelling met hoër variasies. Beelding word preoperatief aanbeveel, veral by vroue, vir vroeër identifikasie van variasies om mislukking met toediening van ʼn PB te vermy, ongeag die benadering wat gebruik word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/104922
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