Mechanisms of spinal stability Flashcards
Depending on their role in stabilisation, muscles of the trunk are placed into two categories, which are the:
Local muscle system &
Global muscle system
What is the local muscle system also known as?
the inner unit
What kind of muscles does the local muscle system include, and where are some of their origins and insertions?
includes deep muscles and the deep portions of some muscles which have their origin or insertion on the vertebrae
What does the local muscle systems control in relation to the spine (3 answers)
- the stiffness (this is the amount of resistance the spine provides in order resist force)
- the position of the spinal segments
- the posture of the lumbar spine.
Give some examples of these muscles? (there are 8 but give 4)
- The transverse abdominis
- Multifidus
- Internal obliques
- Quadratus lumborum medial fibres
- Intertransversarii
- Interspinalis
- Longissimus thoracis pars lumborum
- Iliocostalis lumborum pars lumborum
What is the thoracolumbar fascia and what is its role?
The thoracolumbar fascia is a sheet of connective tissue which has three layers that cover the muscles of the back and has attachments to the spine, pelvis and sacrum. It plays a valuable role in the stabilisation of the spine.
What kind of muscles does the global system consist of?
consists of the large, more superficial muscles of the trunk
What is the global system also known as?
the outer unit
Give 4 examples of the global system muscles!
- the rectus abdominis
- external obliques
- lateral fibres of the quadratus lumborum
- portions of the erector spinae
What is the main role of the global muscle system in relation to stability?
to balance the external loads applied to the trunk so that the forces transferred to the lumbar spine can be accommodated by the local muscles.
How is intra-abdominal pressure created?
by the co-contraction of the abdominal muscles, the diaphragm and the muscles of the pelvic floor.
How does the pelvic floor create stabilisation? Give a metaphoric example
Imagine the trunk as a cylinder, with the top of the cylinder being formed by the diaphragm, the bottom the pelvic floor and the walls formed by the tranverse abdominis and the internal obliques. As the abdominal wall is pulled in and up, the walls of the cylinder are pulled in.
How does the use of breath create stabilisation?
If a deep breath is taken, the diaphragm is lowered, compressing the cylinder from the top. Providing the pelvic floor, which forms the base of the cylinder, is intact, the cylinder is pressurised and made more solid. This allows the spine to resist bending stresses applied to it.
What is Thoracolumbar fascia gain (hoop tension)
The co-contraction of the transverse abdominis and internal oblique produces hoop tension through the thoracolumbar fascia (TLF). Hoop tension is the force applied circumferentially to a cylindrical object. A good example of hoop tension is the tension applied to the iron bands, or hoops, around wooden barrel.
How does hoop tension work?
In your body, the pulling of the muscles on the thoracolumbar fascia creates an extension force on the spine known as thoracolumbar fascia gain. This is thought to be important in buffering the transfer of force between the muscles and ligament systems during forward bending and rising from a bent forward position and provide passive resistance to flexion.
