Chapter 9 The spine: Objectives

• Explain how anatomical structure affects movement capabilities of the spine

• Identify factors influencing relative mobility and stability of different regions of the spine

• Explain the ways in which spine is adapted to carry out its biomechanical functions

• Explain the relationship between muscle location and the nature and effectiveness of muscle action in the trunk

• Describe the biomechanical contributions to common injuries of the spine

The Spine: Outline

• Structure • Muscles and movements • Low Back Pain • Strengthening exercises• Lifting guidelines• Common low pack problems• WebSite for spine and spinal problems:

MMG - Patient Education back TOC

• Study questions for exam:– Introductory problems, p 305: 1,6,7,9,10– Additional problems, p 306: 1,5,8

Structure of the Spine

Structure of Vertebrae

Note: orientation of facets largely determines amount of movement possibleFacets and discs share load bearingQuestion #5, p 306

Facet Orientation – relatedTo movement capability

Segmental Movements

Question #1, P 305

The Spine: Muscles• Spinal flexors – abdominal muscles

– Rectus abdominis– External and internal obliques

• Spinal extensors– Splenius cervicis and capitis (cervical)– Erector spinae (lumbar and thoracic)– Quadratus lumborum (lumbar)

Muscle force vectors

Flexion Exercises

• Effect of– Anchoring feet?– Bending knees?– Placement of hands and

arms?– Inclined board?

Back Extension Exercises to Avoid:

Good morning exercise:Hyperextended back:

Recommended Extension Exercise

Loads on the spine:Line of gravity for upper body passes anterior to vertebral column, creating a forward torque

It is important to keep pelvicgirdle balanced! (Question # 6, 7 p 305)

Effect of posture on lumbar compression force:

Torque while lifting

Lifting recommendations

(1)bend knees , (2) keep weight close to hips

(3) Avoid lifting while twisting and asymmetrical frontal plane loading of the trunk– it places 3 times more stress on the spine (question #9, p 205)(4) Avoid rapid, jerking motion while lifting

Lifting recommendations

Common Spinal Injuries

• Lumbar spinal injury is by far the most prevalent of all areas of the spine

• Low back pain is most common and most expensive injury in work place

• Low back pain is usually related to mechanical stress• 60% of cases are ideopathic

Stress Fractures

• Most common type of vertebral fracture is in pars interarticularis– Spondylolysis– Spondylolisthesis

• Spondylolysis and spondylolisthesis don’t tend to heal with time– Common with sports involving repeated

hyperextension of the lumbar spine.

Common low back problems

Disc degeneration

Spondylolisis – separation of vertebraSpondylolisthesis – forward movement of vertebral body

Disc Herniations

• Cause of 1-5% back pain cases• Protrusion of part of nucleus pulposus from the

annulus.• Traumatic or stress related.• Common sites: between 5th-6th and 6th-7th cervical

vertebrae and 4th-5th lumbar and 5th lumbar and 1st sacral.

• Sensory nerves supplying anterior and posterior longitudinal ligaments generate pain signals.

Two common causes of low back pain

Compressive, or neurogenic:Symptoms are referred due to Spinal nerve compression

Mechanical - localized pain due toDamage to facets, discs, and/or softtissue

•Illustrations below are from: MMG - Patient Education back TOC