The erector muscle of spine consists of the spinal muscle, the longissimus muscle and the iliocostal muscle.
A capitis, cervicis and thoracis section can be distinguished in the first two muscles above. The iliostalis muscle consists of a cervicis, thoracis and a lumborum section. Here we limit ourselves to the clinically more relevant thoracis section for each separate muscle. For the description of the thoracis longissimus muscle and the lumborum iliostalis muscle we make use of the interpretation by the author Bogduk, since this corresponds best with current anatomical practice (origin and insertion are interchanged for example).
- spinalis thoracis muscle (Gray)
- origin: spinous process T11-L2.
- insertion: spinous process T4-T8.
- longissimus thoracis muscle (author Bogduk starts from a thoracic part and a lumbar part, in contrast to Gray)
*thoracic part:
- origin: transverse process of the thoracic vertebrae and ribs
- insertion: spinous process of the lumbar vertebrae and sacral vertebrae (up to and including S3) and superior posterior iliac spine (form the medial section of the aponeurosis of the erector muscle of spine)
*lumbar part:
- origin: transverse process and accessories of the lumbar spinal column
- insertion: superior posterior iliac spine and iliac bone (forms the lumbar intermuscular aponeurosis here)
- iliocostalis thoracis muscle (Gray)
- origin: 7th-12th rib
- insertion: 1st-6th rib and transverse process C7
- iliocostalis lumborum muscle (author Bogduk starts from a thoracic part and a lumbar part, in contrast to Gray)
*thoracic part:
origin: 7th -12th rib
insertion: iliac crest, sacrum and superior posterior iliac spine (form the lateral section of the aponeurosis of the erector muscle of spine)
*lumbar part:
origin: transverse process L1-L4.
insertion: iliac crest (medially they contribute to the lumbar intermuscular aponeurosis
The aponeurosis of the erector muscle of spine is a large tendon blade connected to the iliac bone (particularly the medial part of the iliac crest), the sacrum, and the lumbar and sacral spinous processes. It forms the attachment for the lower part of the erector muscle of spine, particularly the long muscle systems that have their origin at the thoracic level (thoracic part of the longissimus thoracis muscle and the thoracic part of the iliocostalis lumborum muscle). The fibres of the lumbar part of the longissimus and iliocostalis muscles, however, are not connected to the aponeurosis of the erector muscle of spine; these lumbar fibres can function independently of the other parts of the erector muscle of spine. In the lumbar region the longissimus and iliostalis muscles are separated from one another by the lumbar intermuscular aponeurosis (= continuation of the aponeurosis of the erector muscle of the spine in the antero-posterior direction).
The erector muscle of the spine largely determines in the lower thoracic and higher lumbar regions the contours of the back muscles.
The multifidus muscle covers the spine completely and does not have any anatomical subdivisions. The various bundles of muscle each span one to three vertebrae.
In the lumbar region it is located medioventrally from the longissimus and iliostalis muscles, and it is best developed in this area. As such, the multifidus muscle therefore also contributes to the contour of the back muscles at the lower lumbar level. It is surrounded by its own fascia.
- multifidus muscle (Gray)
- origin: sacral bone (dorsally), dorsal sacro-iliac ligaments, superior posterior iliac spine, aponeurosis of erector muscle of spine, lumbar mamillary processes, transverse thoracic processes, articular processes C4-C7
- insertion: lumbar, thoracic and C2-C7 spinous processes
The iliopsoas muscle, the piriformis muscle and gluteus maximus muscle are described in “the examination of the pelvic girdle”