Spinal Biomechanics Flashcards
What is the role of the spine?
- Tolerates & transfers weight to pelvis
- Protects spinal cord
- Allows flexibility in all directions
- Key role in posture
What is the smallest functional unit of the spine?
FSU: 2 vertebrae + IVD
What components contribute to the spinal axial load?
- Gravitational forces due to mass of body segments
- External forces & moments
- Muscle tension (provides equilibrium)
List the factors that affect axial loading of spine:
- Type, rate & duration of loading
- Age
- Posture
- Condition of anatomical structures
- Integrity of nervous system
What posture has least amount of pressure on spine?
Supine (25lbs)
Almost any motion increases loads on spine.
What posture causes the greatest pressure on spine?
Flexion while lifting (>600lbs)
Almost any motion increases loads on spine. Nachemson studied pressure in L2-L3 (150lb man).
Ideal lifting posture is:
Lifting w/knees bent & back straight, with object close to body.
What is intracavitary pressure?
As it relates to spinal axial load.
The pressure within the abdomenal cavity, created by muscles.
The rigid-walled cylinder supports a portion of spine loading.
What is the implication of weakened abdominal muscles on the spine?
Weakening of the abdominal muscles causes increased spine loading & the risk of lower back pain.
What is a major anterior compressive load bearing element?
Intervertebral Disc (IVD)
What is the load carrying capacity of the spine?
Maximum load the axial spine can tolerate w/o collapse.
Influenced by: muscle & bone health
What model demonstrates the contribution of orthotic devices to the load carrying capacity?
Euler Model
1 end fixed: 8x; 2 ends fixed: 16x; Milwaukee Brace is an orthotic illustration.
What load increases LCC?
LCC = load carrying capacity
Transverse Load
All orthoses provide some form of transverse laod; braces increase LCC.
True or False: Most spinal orthoses provide some sort of intracavitary pressure.
True
What is the consequence of lifting weights?
Lifting imposes significant load on spine; contraction of back extensors produces large compressive forces, which may cause failure/fracture.
Especially true in pts w/Osteoporosis