The relation of the sciatic nerve to the piriformis muscle in American whites and negroes.код для вставкиСкачать
THE RELATION O F THE SCIATIC NERVE TO THE PIRIFORMIS MUSCLE I N AMERICAN WHITES AND NEGROES1 MILDRED TROTTER Department of Anatomy, Washington University, St. Louis, Missouri I n the majority of cases the relation of the sciatic nerve to the piriformis muscle is a deep one, the nerve lying ventral to the muscle and emerging from its inferior border to continue distalward. Variations from this relationship are chiefly the partial or complete division of the muscle by a part or the whole of the nerve. These variations have been noted by many anatomists and the incidence is usually found to be between 10 per cent and 20 per cent; e.g., Eider, 18 per cent ; Paterson, 13 per cent ; LeDouble, 17 per cent ; Bardeen and Elting, 10 per cent. These reports have all been based on whites except for that by Bardeen and Elting. Their observations from the Anatomical Laboratory of Johns Hopkins University were made on dissecting-room material composed of both white and negro bodies-material quite similar to that of this laboratory. They found that “neither sex, race, side of body nor skeletal conditions seemed to have intimate association with the natural separation of the sciatic nerve. ’’ The dissecting-room material in this laboratory affords an opportunity to compare further the incidence of variation of the relations of these structures in whites and negroes. Both the nerve and muscle are large enough to eliminate the possibility of destruction during routine dissection. With the cooperation of the students, records of this relationship in ‘Aid in helping to carry out this research was received from the Rockefeller Research Fund. 321 322 MILDRED TROTTER the cadavers have been kept for the past six years. A summary of the incidence of variations in the relative positions of the nerve and muscle is given in the table; differences between race, sex, and side of the body are included. The incidence of bilateral and unilateral variation is approximately the same. However, unilateral variation occurs TABLE 1 Variation f r o m the usual relationship between the sciatic n e r m and the piriformis muscle in cadavers with reference t o race, sex, and side of body SIDES BODIES KACE SEX __- White Male Negro Male White Female Yumher Per cent Incidence Both sides only, 11 Right only, 5 102 Left only, 6 Total bodies, 2 22 ____ ~ _ Both sides only, 6 Right only, 31 8 1 Left only, 5 -I 5 17 Total bodies, .~ Both sides only, 1 Right only, 0 204 -~ 162 - ~ 30 IBoth sides only, 3 Right only, 1 2 34 Left only, Negro Female -. Total bodies, 6 18 ~. -__ Total %-: __,__-- Both sides only, 21 Right only, 9 232 Left only, 33 Total bodies, 19 68 1 Per cent Incidence ~ Both sides only, 22 Right only, 5 Left only, 6 Total sides, 33 16 _ _ _ ~ _ _ Both sides only, 12 Right only, 3 5 Left only, Total sides, 201 12 ~ _ _ _ -21 Both sides only, Right only, 0 0 Left only, Total sides, 2 7 - -1 'Both sides only, 61 Right only, 1 2 Left only, ~ ~ -~ Total sides, 9 13 _ Both sides only, 42 Right only, 9 13 464 Left only, __ Total sides, 64 14 _ slightly more often on the left side than on the right in all the groups except the white female group, which is too small for statistical comparisons. The number in this group is inadequate also for a racial comparison of females. A comparison between whites and negroes in the male group shows the whites to be somewhat more variable than the negroes. This is interesting because of the assertion of Rosenmiiller, ~ RELATION OF SCIATIC NERVE AND PIRIFORMIS MUSCLE 323 questioned by both Testut and LeDouble, that a premature bifurcation of the sciatic nerve (which almost invariably is the case in an altered relationship of the nerve and the piriformis muscle) occurs more often in northern races than in meridional (southern) races. The findings on this material (excluding the white female group which is too small for comparison) may be summarized as follows: the whites are more variable than the negroes; no sex difference is present in the negroes; and the left side is very slightly, but consistently, more variable than the right. LITERATURE CITED EISLER,P. 1892 Der Plexus lumbo-sacralis des Menschen. Halle. PATERSON, A. M. 1894 The origin and distribution of the nerves to the lower limb. J. Anat. and Phys., vol. 28, pp. 84-95. BARDEEN, C. R., AND ELTING, A. W. 1901 A statistical study of the variations i n the formation and position of the lumbo-sacral plexus in man, p a r t 11. Anat. Anz., Bd. 19, S. 209-239. LEDOUBLX,A.-F. 1897 Trait6 des variations du systhne musculaire de 1’homme, T. 2. Paris. TESTTJT, L. 1884 Les anomalies musculaires chez l’homme. Paris.