280 THE INFERIOR EXTREMITY 



sacrum, and it corresponds with the middle of the sacro- 

 iliac articulation. The prominence of the nates is formed 

 chiefly by the glutaeus maximus muscle, covered by a thick 

 layer of fat. A deep transverse groove, produced by a fold of 

 skin and fascia, limits the gluteal elevation below. The groove 

 is called the gluteal sulcus^ and is sometimes said to correspond 

 with the distal border of the glutaeus maximus muscle. It can 

 easily be shown that this is not the case. Its medial end lies 

 distal to the inferior margin of the muscle, but as the sulcus 

 proceeds transversely it crosses the border of the muscle, and 

 finally comes to lie on the surface of the muscle. In disease 

 of the hip joint, the buttock loses its prominence, whilst 

 the gluteal sulcus becomes faint. The tuberosity of the 

 ischium may be felt, deep to the lower border of the glutaeus 

 maximus, if the fingers are placed in the medial part of the 

 gluteal sulcus and pressed upwards. A line drawn from the 

 most prominent part of this tuberosity to the anterior superior 

 spine of the ilium is called Nelatorfs line \ it passes over 

 the top of the greater trochanter and crosses the centre of 

 the acetabulum; and it is used by the surgeon in the diagnosis 

 of dislocations and other injuries of the hip joint. The greater 

 trochanter of the femur may be felt at a point about six inches 

 below the highest part of the crest of the ilium. It can be 

 seen in thin subjects, but it does not form so projecting a 

 feature of this region as might be expected from an in- 

 spection of the skeleton, because the thick tendon of the 

 glutaeus medius is inserted into its lateral surface, and it is 

 covered also by the aponeurotic insertion of the glutaeus 

 maximus. 



Dissection. Reflection of Skin. Incisions. (i) From the 

 posterior superior spine of the ilium in a curved direction along 

 the crest of the ilium, as far forwards as the position of the body 

 will permit ; (2) from the posterior extremity of this curved 

 incision obliquely downwards and medially to the middle line 

 of the sacral region, and then perpendicularly to the tip of the 

 coccyx ; (3) from the tip of the coccyx obliquely distally and 

 laterally over the back of the thigh, to the junction of the proximal 

 and distal halves of the posterior border of the lateral area of 

 the thigh. 



A large flap of skin is thus marked out, and this must be 

 raised from the subjacent superficial fascia and thrown laterally. 

 On the right side of the body the dissector begins at the crest of 

 the ilium and works downwards and forwards ; whilst on the left 

 side he commences over the coccyx and works upwards and 

 forwards. 



