The spine is initially examined in the standing position with the hands relaxed at each side. The entire posterior aspect of the trunk should be exposed, the subject wearing small briefs and being barefooted. Observe the posture from behind and from each side (figure 7). The details of the posterior spinal muscles are shown in figure 8 and table 1 (pages 84, 86). Note the natural cervical, thoracic and lumbar curvatures. The thoracic curvature may be more pronounced with increased age, abnormal prominence is termed kyphosis. The lumbar curve is more marked in females and excessive curvature is termed lordosis. Note any scoliosis.
Bony landmarks are the spinous processes, the angles of the scapulae, the ribs, and the crests and posterior superior iliac spines of the pelvis. A shallow pit (dimple of Venus) may be present over posterior superior iliac spine, particularly in the female. The spines should be in the midline and the two sides of the body symmetrical. The vertebra prominens is the spine of C7.
Note any steps in the spinous processes, indicating abnormalities of the underlying vertebra.
1. Vertebra prominens of C7
2. First rib
3. Spine of T1
4. Superior 6. medial and 11. inferior angles of scapula
7. Spine of scapula, with medial expansion (tubercle) 8. Greater tuberosity of humerus
9. Medial border of scapula
10. Spine of T 7, extending downward by more than a vertebra in depth 12. Eleventh and 13. twelfth ribs
14. Upper pole of right kidney
15. Spine of fourth lumbar vertebra (supracristal plane)
16. Iliac crest
17. Lateral part (ala) of sacrum
18. Sacroiliac joint
19. Posterior superior iliac spine (marked by Dimple of Venus) 20. Posterior inferior iliac spine
21. Tip of coccyx
22. Ischial tuberosity
Posterior spinal muscles
Iliocostalis (green): 5. cervicis, 7. thoracis, 13. lumborum
Longissimus (red): 2. capitis, 6. cervicis, 10. thoracis
Spinalis (blue): 4. cervicis, 9. thoracis
Semispinalis (purple): 8. length of thoracic and cervical spine, 3. capitis
1. Spenius capitis
11. Levatores costarum: to adjacent or lower rib
12. Intertransverse, interspinous, rotators: close to midline, length of spine
14. Multifidus: across one or more vertebra, length of spine
The bulk of the deep extensor muscle mass of the back is formed from the erector spinae muscle group.
This produces the longitudinal bulge on each side of the midline that extends from the sacrum to the occiput and, in the thoracic region, reaches the angles of the ribs. A deeper transversospinalis group of muscles fills the groove between the spines and the transverse processes, and superiorly, the erector spinae are overlain by the two splenius muscles on each side, as well as by the superficial muscles (trapezius, latissimus dorsi, the rhomboids and serratus posterior muscles).
The following table provides a summary of the attachments of these three deep muscle groups, but there is often variation, with absence, overlap and fusion of the various parts.
The muscle mass as a whole extends the back and, on each side, rotates the trunk to the same side: similar head movements are produced by muscles from these groups that are attached to the skull. Head movements are supplemented by another group of short suboccipital muscles, passing between the skull, the atlas and the axis. Collectively, the muscle mass also plays an important role in posture and stabilising the vertebral column and rib cage. Its nerve supply is segmental, from the dorsal rami of the spinal nerves.