module 10

Question 1

what are the key biomechanical concepts of the lumbar spine and how it fuctions?

Answer 1

1. orientatin of the facets determines type of motion possible (transverse and frontal plane) - each segment contributes to the flexion/extension
2. loading of lumbar IV disk is influnenced by posture (standing up has less IV force than seated or slouched b/c of where mass of UB goes through with respect to the joint)
3. flexion-extension movement of the lumbar spine - motion between two vartebrae is small, always a combined motion of several segments, intersegmental kinetics
   - the amount of strain on each ligament depends on the type of motion (flexion: supraspinal ligament, capsule, flavum; extension: longitudian anterior lig; rotation: capsular lig; lat flextion: transverse ligament)

Question 2

explain the flexion-relaxation phenomenon

Answer 2

first 50-60 deg occurs in the lumbar spine
* at full flexion, the lumbar ES are turned off
- active muscular actions are relieved of thier supporting role
role is transferred to the ligaments of the lumbar spine ad passive properties of muscles
possible because the force of the passive structures increases when lengthened: new eq bw the flexor moment by gravity and the extensor moment by the stretched passive structures

*relaxation of the lumbar muscles occurs in an electrical sense
- lumbar muscles still develop substantial elastic force contributing to extensor moment
- the elastic muscle force is developed through stretching of the muscle (PEC and SEC)
- the absence of electrical activity means the muscle is not performing an action at this point (ecc, iso, con)

*the biomec of tissues tells us that the myoelastic silence of the lumbar extensor during trunk flexion is due to load transfer from active to passive structures - when passive structures can bear the load, the muscles turn off

Question 3

what are common pathologies in the spine?

Answer 3

1. scoliosis, thoracic hyperkyphosis
2. lower back pain
3. spinal deformities

Question 4

what is the working hypothesis of low back pain?

Answer 4

• single or cumulative microtrauma to the spinal ligaments or disks causes a subfailure injury of the structures
• ligaments and external layers of annulus fibrosus are richly innervated with nociceptors and mechanoreceptors
• generates a cascade of events leading to poor control of the spinal musculature - and subsequent higher stresses to the spinal ligaments and disks

Question 5

what is the clinical relevance of the FR phenomenon?

Answer 5

FR disappears in persons with mechanical low back pain
- kinematics: intervertebral motions are greatly reduced - both rotation and translation in LBP patients
- explanation: decreased IV movement to protect the injured spinal ligaments of disk
(if injured, additional stretching of posterior ligaments or disk may cause further injury or pain)