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Modified Subgluteal Approach to the Sciatic Nerve

2003; Lippincott Williams & Wilkins; Linguagem: Inglês

10.1213/01.ane.0000077652.77618.79

1526-7598

Carlo D. Franco, Serge G. Tyler,

Genital Health and Disease

To the Editor: We have read with interest the recent article by Sukhani et al. (1) on a modification of the subgluteal approach to the sciatic nerve using muscle identifications as opposed to “bony” landmarks. We would like to make a few comments: 1. A technique that purposely misses the posterior femoral cutaneous nerve should more appropriately be compared to a popliteal block than to more proximal approaches. 2. We agree that it is usually difficult to identify bony landmarks (“particularly in overweight patients”), as needed with most of the sciatic techniques. However, it is difficult to imagine that palpating the biceps femoris high in the thigh is any easier “particularly in overweight patients.” 3. The proposed approach is based on finding the point in the gluteal crease at which the lower border of the gluteus maximus and lateral border of biceps femoris intercept. Throughout their article, the authors equate the gluteal crease with the lower border of the gluteus maximus. This is a common but erroneous belief. As the anatomy literature shows (2), the gluteal crease is a fold of the skin and subcutaneous tissue that “does not correspond to the lower border of the gluteus maximus muscle”(3). In fact, they do not even have the same direction. The inferior border of the gluteus maximus goes from medial to lateral on a steep angle to insert mainly in the iliotibial tract. The gluteal crease on the other hand goes from medial to lateral rather horizontally. Thus the biceps femoris, at the level of the gluteal crease, is under the cover of the gluteus maximus. This is especially true for the lateral border of biceps (see Fig. 1).Figure 1: Right buttock dissection performed on fresh tissue cadaver showing: (1) gluteus maximus muscle, (2) biceps femoris muscle, (B) point of interception of lateral border of biceps and gluteus maximus, (AB) lower border of gluteus maximus, (AC) gluteal crease (projection).4. An approach as the one proposed (“1 cm distal to the gluteal crease along the lateral border of the biceps femoris muscle”) must then first overcome the difficulty of locating a muscle (biceps) through a second muscle (gluteus maximus), not to mention doing so through adipose tissue. If this task were accomplished, the needle would necessarily have to pass through the substance of the gluteus maximus, because the point at which this muscle and the lateral border of the biceps intercept is located significantly more caudal. This would also defy their stated purpose of passing through an area where “the nerve is covered only by skin and subcutaneous tissue.” One way to get around it would be to try to palpate the biceps more distally in the thigh and follow it proximally to the point of real interception with the gluteus maximus, performing the technique several centimeters distal to the gluteal crease. We congratulate the authors for their contribution. When biceps can be palpated, this proposed approach could be an alternative to a popliteal approach. Carlo D. Franco, MD Serge G. Tyler, MD