Back Mechanics

Presented by QBE

Loss Control Services

Back Injuries Statistics• 25% of low back injuries account for 95%

of costs of low back injuries

• NIOSH- 70% of general public will have back pain in their lifetime

• 80% of back pain caused by inadequate exercise

• Back injuries account for 25% of all WC claims and 33-44% of all WC costs

Spinal Column

The spine is made up of 33 vertebrae. The upper 24 vertebrae are separated by a jelly filled layered ligaments called disks. These disks act as shock absorbers for the spine.

The facet joints are the back part of the vertebrae that form the channel for the spine.

The lumbar region are the five large vertebra composing the lower back, allowing the back to bend forward and back.

Spinal Column

Discs and Force

Herniated Discs

Lower Spine

Spine Range of Motion

0 10 20 30

L5-S1L4-5L3-4L2-3L1-2T12-

T11-12T10-11T9-10T8-9T7-8T6-7T5-6T4-5T3-4T2-3T1-2

C7-T1C6-7C5-6C4-5C3-4C2-3

Flexion/Extension

Degrees

Spine Range of Motion

0 10 20 30

L5-S1L4-5L3-4L2-3L1-2T12-

T11-12T10-11T9-10T8-9T7-8T6-7T5-6T4-5T3-4T2-3T1-2

C7-T1C6-7C5-6C4-5C3-4C2-3

LateralFlexion

Degrees

Spine Range of Motion

0 10 20 30

L5-S1L4-5L3-4L2-3L1-2T12-

T11-12T10-11T9-10T8-9T7-8T6-7T5-6T4-5T3-4T2-3T1-2

C7-T1C6-7C5-6C4-5C3-4C2-3

Rotation

Degrees

Back Mechanics

Danger Zones

Anatomy of Proper Lifting

Anatomy of Proper Lifting

If you are out of physical shape can also result in increased loads when we improperly lift.

Balance of Forces

Balance of Forces

Without Weight

? lb x 2 in = (65 lb x 9 in) + (15 lb x 15 in) + (25 lb x 24 in)

? X 2 in = 1410 lbs

Force on Back = 705 lbs

Torso Arms Head

Balance of Forces

With Weight

? lb x 2 in = (65 lb x 9 in) + (15 lb x 15 in) + (25 lb x 24 in) +(20 lb x 36 in)

? X 2in = 2130 lbs

Force on Back = 1065 lbs

Torso Arms Head Object

Equivalent Forces

Relative Disk Pressure

40

100

150150

190

0%

20%

40%

60%

80%

100%

120%

140%

160%

180%

200%

Position

Reclining

Standing

Sitting

StandingLeaningForwardSitting LeaningForward

Relative Disk Pressure Sitting Posture

100%

85% 85%75%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Position

Sitting Upright

Sitting Uprightw/Low BackSupportReclining

Recliningw/Low BackSupport