220 INFERIOR EXTREMITY 



the crest of the ilium at a point corresponding to the lateral 

 limit of the attachment of the sacro-spinalis to the innominate 

 bone. They pass distally and slightly anteriorly in the 

 superficial fascia, and run in different planes, the larger 

 trunks being placed deeper than the smaller branches. They 

 communicate with one another and with the sacral nerves. A 

 few twigs may be followed as far as the greater trochanter. 



The cutaneous twigs which come from the anterior branches 

 of the spinal nerves may be classified under three headings 

 (i) those which pass distally over the crest of the ilium; 

 (2) those which pass dorsally over the insertion of the 

 glutaeus maximus into the fascia lata ; (3) those which turn 

 proximally round the distal margin of the glutaeus maximus. 



The nerves which cross the crest of the ilium are (i) 

 ramus cutaneus lateralis of the ilio-hypogastric nerve; and (2) 

 the ramus cutaneus lateralis of the last thoracic nerve. 



The lateral cutaneous branch of the ilio-hypogastric nerve 

 pierces the external oblique muscle close to its insertion into 

 the ilium. It usually crosses the iliac crest opposite a 

 tubercle which projects from the lateral lip of the crest, about 

 two and a half inches from the anterior superior spine, but it 

 may emerge at any point between this tubercle and the anterior 

 border of the iliac origin of the latissimus dorsi. The lateral 

 cutaneous branch of the last thoracic nerve pierces the external 

 oblique muscle of the abdominal wall, a short distance in front 

 of the branch of the ilio-hypogastric, at a point situated from 

 one to two inches above the iliac crest. Both nerves, after 

 crossing the iliac crest, run distally in the thick superficial 

 fascia over the upper part of the glutaeus medius, and spread 

 out into a great number of fine twigs, which ramify over the 

 insertion of the glutaeus maximus. Some of them reach 

 distally as far as the level of the greater trochanter. 



The nerves which pass dorsally over the insertion of 

 the glutaeus maximus are a few small twigs of the posterior 

 branches of the lateral cutaneous nerve of the thigh. They 

 are found above the level of the greater trochanter. 



The cutaneous twigs which hook round the distal margin 

 of the glutaeus maximus muscle, to reach the skin over this 

 region, are a few offsets from the posterior cutaneous nerve of 

 the thigh and the perforating cutaneous branch of the fourth 

 sacral nerve. The former appear lateral to the tuberosity of 

 the ischium, and are accompanied, in some cases, by twigs 



