2 9 o THE INFERIOR EXTREMITY 



border of the piriformis ; (2) branches of the inferior gluteal 

 artery and the inferior gluteal nerve below the level of the piri- 

 formis. The venae comites of the arteries may at once be removed, 

 but the arteries and nerves must be cleaned as they come into 

 view and followed into the substance of the glutaeus maximus. 

 Finally, in order to allow the complete reflection of the muscle, 

 the arteries and nerves must be cut, but a small portion of the 

 muscle should be left in connection with their cut ends so that 

 they may be readily recognisable during the further stages of 

 the dissection. The whole muscle can now be thrown distally 

 and laterally, and, after a little dissection, an excellent view of 

 its insertion can be obtained. 



When the reflection of the muscle is completed note 

 carefully the positions of the following parts: (i) the 

 posterior border of the trochanter major; (2) the gluteal 

 tuberosity which lies immediately distal to (i); (3) the 

 tuberosity of the ischium ; (4) the sacro-tuberous ligament. 



The trochanter major is situated in the lower and lateral 

 part of the area exposed by the reflection of the glutaeus 

 maximus. Immediately distal to it is the gluteal tuberosity 

 into which the lower deep fibres of the glutaeus maximus are 

 inserted. The ischial tuberosity lies about 7 or 8 cm. medial 

 to the distal part of the trochanter major. If the thigh is 

 rotated laterally the trochanter is approximated to the 

 tuberosity, and it recedes from the tuberosity when the thigh 

 is rotated medially. 1 The sacro-tuberous ligament extends 

 upwards and medially, from the tuberosity of the ischium 

 to the margins of the sacrum and coccyx, and to the posterior 

 inferior and superior spines of the ilium. The inferior 

 border of the ligament is relatively straight It forms the 

 posterior boundary of the ischio-rectal fossa of the perineum, 

 which has already been explored by the dissector of the 

 abdomen. Its upper margin is curved, with the concavity 

 directed forwards and upwards, and immediately in front of 

 it are the greater and lesser sciatic foramina, which are 

 separated from one another by the sacro-spinous ligament 

 The sacro-spinous ligament can be felt where it is attached 

 to the spine of the ischium, 2.5 cm. above the upper border 

 of the tuberosity of the ischium. Note also a group of 

 muscles which are attached to the tuberosity and descend 

 from it into the posterior region of the thigh. They are the 

 hamstring muscles ; do not clean them at present 



1 The thigh is said to be rotated medially when its anterior surface is 

 turned towards the median plane, and laterally when the anterior surface is 

 turned away from the median plane. 



