Anatomic study of the lateral cutaneous rami of the subcostal and iliohypogastric nerves.

On the supposition that some "pseudocoxalgias" might be due to a neuralgia of the lateral rami leaving the subcostal and iliohypogastric nerves above the lateral edge of the iliac crest, the authors undertook an anatomic study of their pathways and pattern of distribution. These rami supplying the skin below the iliac crest, which they cross close together, the ramus arising from the subcostal nerve by perforating the internal and external oblique abdominal muscles, that arising from the iliohypogastric nerve a little lower, creating a bony groove palpable in thin subjects and transformed into an osseomembranous tunnel by the aponeurosis of these muscles. This arrangement may give rise to an entrapment syndrome. At this intersection, the course is either vertical or "bayonet-shaped", directly subcutaneous, and hence exposed to possible friction and microtraumata (tight clothes). The two rami are of unequal length. Frequently, the ramus arising from the subcostal nerve is short, not exceeding 10 cm, below the iliac crest, thus corresponding to the usual description. That arising from the iliohypogastric nerve descends further, passing 3 to 5 cm anterior to the great trochanter. It ends either at this level or 8 to 10 cm below. This accounts for the distribution of the pain felt when there is irritation of this ramus.