Spinal mechanics and function
Spinal mechanics and function
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Spinal Function
The elongated ‘S’ construction of the spine increases the load carrying capability giving it strength and elasticity to absorb the shocks of running, jumping, twisting etc… as well as effectively protecting the spinal cord which transmits signals from the brain throughout the body.
The spinal column consists of 33 bones (vertebrae) of which 24 are moveable.
7 cervical – neck vertebrae
12 thoracic – chest vertebrae
5 lumbar- lower back vertebrae
5 sacrum - fused
4 coccyx - fused
Vertebra
Each vertebra consists of 2 parts:
Vertebrae are interconnected above and below by the spinal facet joint as well as muscles and tendons to support the spine and enable movement
Intervertebral Disks
Vertebrae are interconnected above and below by the spinal facet joint as well as muscles and tendons to support the spine and enable movement.
The intervertebral discs are soft cushions made from cartilaginous tissue.
Facilitate movement, separate individual Vertebra and act as a shock absorber as an individual moves. Each intervertebral disc consists of 2 parts:
Nucleus Polposus – jelly like centre
Annulus Fibrosis – strong fibrous ring that attaches to the vertebra
Damage to Intervertebral Disks
Tension – applies compression to one side and tension to the other. Caused by excessive forward flexion or side flexion.
Compression – downward force on the vertebrae compresses the discs and causes them to shorten and widen. Caused by a fall e.g. diving into shallow water.
Shear – application of a load parallel to the vertebral surfaces. Caused by whiplash.
Torsional / Twisting – excessive twisting to the spine causing the fibres of the intervertebral disks to be stretched and weakened. Caused by twisting the spine while carrying weighted object.
During manual handling a combination of compression, torsional, tension and shear forces may occur throughout the activity
Good Posture
Tips for good posture:
Stand tall
Hold head straight with earlobes in line with the middle of shoulders
Shoulders back and arms hanging naturally down sides of body
Lightly draw in core abdominal muscles
Stand with weight mostly on balls of feet
Feet set shoulder-width apart for balance
Prominent foot slightly forward
Knees slightly bent
Good posture will:
Keep bones and joints in alignment
Decrease stress placed on bones and joints
Prevent backache and muscular pain
Posture Check – Stand against a wall with head, shoulders, bottom and back of feet in contact with the wall surface. This will ensure spine is aligned.
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