Biomech

7/1/99

• Acute pain is the first time of the pain, I know exactly when the pain start
• Chronic pain is have had it for a long time off and on
• #1 pt is going to be an exaggeration of a chronic condition
• Stresses that develop in the spine

1. Disc

• Fig 10-14
• Looking at intradiscal pressure at different postures
• Standing straight up is 100—no muscles are actually firing (soleus in leg)—pressure at L3
• Laying down drops is 1/3 or ¼--center of gravity changes
• Sitting increases a little—moment arm is longer, have to contract more increasing the pressure
• True disc problems would rather stand (or lie down is disc pain) than sit (facet pain)
• Sitting and stooping is the most pressure (tying shoes would be very painful)
• Lifting—moment arm—bending knees may help—move the weight as close to midline as possible
• Exercises—increasing abdominal strength to decrease low back pain
• Psoas muscle is the one causing problems w/discs in lumbar spine
• Put feet on a chair and it takes the psoas out
• Better exercise for disc problem

Pain

• Skin
• Capsule of facet
• Outer edge of the disc
• Dorsal root ganglion—only one sensitive to pain
• Straight leg raise is initially negative until the disc bulge pushes on the nerve root
• Borders of the facets
• Front—ligamentum flavum—like a rubber band, keeps itself from being stuck in the facet joint during motion
• W/age it looses its rubber band properties

• Post wall—multifidus muscle fibers—have negative pressure w/in a joint, like the rotator cuff muscles that become the joint capsules
• Muscle and joint capsule have the same innervation
• Multifidus action—pulls straight back (extends)
• 50% of LBP is facets
• pain cycle started in facet or muscle
• what ever you do to the muscle, you do to the facet
• pain is bilaterally equal b/c the muscles are so close together that if one fires, the other fires
• when fire the muscles, compress the facet—increased the pain