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 spinal problems Study questions for exam (do not submit, just do on your own): 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 possible Facets and discs share load bearing Question #5, p 306

Facet Orientation – related To movement capability

Segmental Movements Question #1, P 305

The Spine: Muscles Spinal flexors – abdominal muscles Spinal extensors 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 pelvic girdle 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

Lifting recommendations (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 MMG – Website for musculoskeletal disorders

Two common causes of low back pain Compressive, or neurogenic: Symptoms are referred due to Spinal nerve compression Mechanical - localized pain due to Damage to facets, discs, and/or soft tissue

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 Spondylolisis – separation of vertebra Spondylolisthesis – forward movement of vertebral body Disc degeneration

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.