The centre of gravity lies in front of the second piece of the sacrum: gravity therefore promotes flexion. Cervical flexion is also produced by the infrahyoid and sternomastoid muscles and, in the thoracic and lumbar regions, by the rectus abdominus and oblique muscles of the abdominal wall. Extension is by the powerful erector spinae muscle group (see – Table 1 Deep muscles of the back). Lateral flexion is by the abdominal wall muscles, supported by quadratus lumborum; rotation is by the abdominal wall muscles and obliquely placed muscles within the erector spinae muscle mass.
Head movements are by the suboccipital muscles, and the superficial neck muscles (sternomastoid, trapezius, splenius) produce rotation and lateral flexion.
Scoliosis may be mild and postural in nature, and can be overcome by asking the subject to place each hand on the opposite shoulder and to lean forward (figure 17). The latter movement also accentuates a pathological scoliosis. Scoliosis is produced by rotation of the bodies of the vertebrae, so that the spine points to the concavity of the curve: kyphosis and scoliosis are thus often combined.
Active and passive movements of the cervical spine are often assessed independent to the rest of the back. To test flexion, ask the patient to put their chin on their chest (normal 45 degrees) and then extension by looking upward and backwards (45 degrees). Lateral flexion is by approximating the ear to the adjacent shoulder on each side, it is approximately 45 degrees.
Rotation is by looking over each shoulder and is normally 75 degrees in each direction (figure 18a–k). Combined movements of the sternomastoid muscles of the two sides produce other head and neck movements such as looking under tables, raising the head from the horizontal and protruding the jaw (figure 19a,b).
Shrugging and bracing the shoulders is primarily brought about by the muscles of the pectoral girdle (figure 20a–d) above.
Much of the apparent flexion on leaning forwards to touch ones toes with straight leg (figure 21), takes place at the atlanto-occipital and hip joints. In the cervical region flexion straightens the cervical curve. There is little flexion in the thoracic spine but flexion is maximal in the lumbar region. The distance of the fingertips from the ground on bending forward varies with age and between individuals. This distance can be used to determine the point of onset of pain, and to monitor progress of any limitation of movement.
The spines can be marked and the distance in between any chosen levels measured with a tape measure before and after flexion (figure 22a,b).
Trunk flexion can be observed and resisted, as in sitting up from the horizontal (figure 23a,b). Assess extension by leaning backwards (figure 22c). Assess lateral flexion by asking the subject to slide a hand down each thigh in turn (figure 23d,e). Rotation can be masked by pelvic movement, and you have to hold the pelvis whilst the subject turns their head and shoulders maximally to each side; more conveniently, test the movement with the subject sitting down (figure 23f,g).
Other essential components of the examination of back pain, are a neurological assessment, and a rectal and/or vaginal examination to ensure that pathology within the pelvis is not causing the symptom. Lumbar puncture is considered on page 368.
The surgical approach to the spinal cord is through dorsal midline incisions, removing one or more laminae (laminectomy) to reach the extradural space, and the dura and its contents. With improved imaging and telescopic devices, minor disc protrusions are increasingly being managed by minimally invasive surgery, to remove the protruded annulus fibrosus and relieve nerve pressure.