[Anatomic variability of the relation of pelvitrochanteric muscles and sciatic nerve.]

The article proceeds from the preceding work published in this journal under the title "Impairment of the function of the sciatic nerve after the surgery in the region of hip joint" It studies a hypothesis for another potential cause of the impairment of the function of the sciatic nerve, i.e. overdistension of the sciatic nerve in the region of pelvitrochanteric muscles after their tenotomy. In order to verify this hypothesis the authors studied 51 cadavers. They describe first of all mutual relation of m. piriformis, m. triceps coxae and the sciatic nerve. The findings were always classified according to one of the 6 types after Beaton. The authors also studied the possibility of the occurence of the compression of the sciatic nerve or its branch after the excision of pelvitrochanteric muscles from the origin in individual types. The most frequent anatomical relation (Type I) when the undivided sciatic nerve arises distally below undivided muscle belly of m. piriformis was found in 80 % cases. Some of the variants occurred in total in 20 %. Of this, the case when the nerve bifurcates high proximally with one branch crossing the muscle belly and the other passing below the muscle (Type IV) was found in 13,9 %. Another type (Type VI) when the nerve bifurcates high proximaly. one branch procceding above the muscle and resting further on the dorsal surface of the muscle and the second proceeding distally below the muscle, was found in 3,94 %. In 1,96 % cases the undivided nerve passed through the muscle belly of m. piriformis (Type V). Other variants were not found in the mentioned group. The mentioned cadaver dissection show that the frequency of the incidence of variants of the relation of the sciatic nerve and m. piriformis is relatively high and the overdistension of the sciatic nerve after the excision of m. piriformis in some of these variants may be the cause of neurological impairment after the surgery in the region of hip joint. Key words: sciatic nerve, m. piriformis, muscle variability.