| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1991: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1990: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
The perforation of nerves of the sacral plexus through the piriformis muscle was studied macro- and stereo-scopically and statistically.
1. Multiple relations between the nerves and the piriformis muscle were classified into 13 types, each occurring equally in both sexes and both sides of 257 human bodies. The perforating position of the nerves was divided into lateral and medial types.
2. A tight connection among the nerves was revealed at the second sacral nerve and was related to their having the same course. passing through or over the piriformis muscle. Although the priority for perforation of the-nerves depended on their origins in the plexus, -there was a reverse order of perforation and an upside-down distribution of the inferior gluteal nerves in the medial type, because of perforation of the lower segmental components of the nerves.
3. The perforation of the nerves was independent of segmental structures such as the number of presacral vertebrae, and the features of the promontorium and of the furcal nerve.
4. As muscular bundles of the piriformis, including the dorsal part of the gluteus medius and an aberrant muscle between the tibial nerve, were distributed by muscular branches which shifted the origins in succession from the superior gluteal nerve to the tibial nerve, it was suspected that the muscles had been derived from a common muscular anlage, developmentally.
5. When a muscular anlage of the piriformis appears surrounding the common peroneal nerve, such a condition might be continued to keep the nerves passing through the piriformis. When the ventral anlage does not appear or degenerates during development, a condition occurs' in normal cases in which the nerves do not perforate the piriformis. Those cases in which the nerves pass over the piriformis, most likely occur due to a complete union of the upper part of the piriformis muscle with the dorsal part of the gluteus medius muscle.
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