Biomechanics of the Spine

1
Biomechanics of the Spine Hip

• Movements of Spine
• Flexion, Rotation, Extension, Abd, Add.
• Hip Movements
• Elevation, Anterior Posterior Tilt, Flexion,
  Extension, Abd, Add, Hyperext, Hyperflex

2
Spinal Deviations

• Lordosis
• Kyphosis
• Scoliosis

3
Forces Acting On The Spine

• Forces Acting On The Spine Include
• Body Weight
• Tension In The Spinal Ligaments
• Tension In The Surrounding Muscles
• Intraabdominal Pressure
• The Major Form Of Loading On The Spine Is
• Axial

4
Upright Position

• Spinal Compression
• Resulting From
• Body Weight Weight Held by Arms and Hands
• When Standing Upright
• Total Body Center of Gravity Is Anterior to the
  Spinal Column.
• Spine Is Placed Under Constant Forward Bending
  Moment.

5
Torque

• Defined The Rotary Effect of a Force About An
  Axis of Rotation, Measured as the Producer of the
  Force and the Perpendicular Distance Between the
  Forces Line of Action And The Axis
• To Maintain An Upright Position
• Torque Is Counteracted by Tension in the Back
  Extensor Muscles.

6
Spinal Muscles Role In Lifting

• Spinal Muscles Have Small Moment Arms With
  Respect To the Vertebral Joints.
• Have To Generate Large Forces To Counteract the
  Torque Produced About the Spine by Body Weight
  and Objects Being Lifted.

Erector Spinae Muscles
7
Why Lift With The Legs?

• Back Muscles, With a Moment Arm of Approximately
  6 cm, Must Counter The Torque Produced by the
  Weights of the Body Plus Any External Loads.

8
Question How Much Torque Is Developed By The
Erector Spinae Muscles With a Fm 6 cm?

• 1 lb. 4.448 Newtons
• Segment Weight Moment Arm
• Head 13 lbs. (58N) 25 cm
• Trunk 73.75 lbs. (328N) 10 cm
• Arms 18.2 lbs. (81N) 20 cm
• Box 24.95 lbs. (111N) 40 cm
• Torque at L5-S1
• (328N)(10cm) (81N)(20cm) (58N)(25cm)
  (111N)(40cm)
• ?
• 10,790 Ncm
• Force?
• 0 (Fm)(6cm) - 10,790 In static position, sum
• of the torques acting at any point is zero.
• Fm 1798.33 N or (404.30 lbs.)

9
Problem for a 135 lb. Person

• How much force must be developed by the erector
  spinae with a moment arm of 6 cm. From the L5-S1
  joint center to maintain the body in a lifting
  position with segment moment arms as Specified?
• Segment Weight Moment Arm
• Head 50 N 22 cm.
• Trunk 280 N 12 cm.
• Arms 65 N 25 cm.
• Box Lifted 100 N 42 cm.
• Torque ?
• 10,285 Ncm
• Fm 1714 N or (393 lbs. Force)

10
What Does The Research Show?

• Load Compression On L3 During the Upright
  Standing, Lying Down, and Sitting.
• Compression Increases More with Spinal Flexion,
  and Increases Still Further with a Slouched
  Sitting Position.

11
Common Injuries Of The Back

• Low Back Pain
• Soft Tissue Injuries
• Acute Fractures
• Stress Fractures
• Disc Hernia ions
• Whiplash Injuries

12
Low Back Pain

• 75-80 of Americans Experience Low Back Pain
  Sometime During Life.
• Second Only to the Common Cold In Causing Absence
  In The Workplace.
• Mechanical Stress Psychosocial.

13
BACK, SPINAL COLLUMN, NECK

• VERTEBRAL COLLUMN
• RIBS STERNUM

14
SPINAL COLLUMN

• 7 CERVICAL VERTEBRAE
• 12 THORACIC
• 5 LUMBAR
• 1 SACRUM - FUSED
• 1 COXCYC - 2 FUSED

15
JOINTS OF THE VERTEBRAL COLLUMN

• VERTEBRAL JOINTS
• GLIDING JOINTS - SLIGHTLY MOVABLE
• SEPARATED BY INTERVERTEBRAL DISKS

16
THORACIC COMPLEX - RIBS

• 12 SETS OF RIBS
• ARTICULATE WITH THE THORACIC VERTEBRAE AND
  STERNUM
• 7 PAIRS OF TRUE RIBS - ATTACH DIRECTLY TO STERNUM
• 5 PAIRS OF FALSE RIBS
• 2 PAIRS OF FLOATING RIBS
• 3 PAIRS ATTACH TO STERNUM VIA COSTOCHONDRAL
  CARTLILAGE

17
STERNUM

• MANUBRIUM
• BODY
• XIPHOID PROCESS

18
MUSCLES OF THE BACK, NECK ABDOMEN

• DEEP POSTERIORS
• ABDOMINALS
• VERTEBRALS
• SUPERFICIAL NECK MUSCLES

19
DEEP POSTERIORS

• MOVEMENT - ROTATION, EXTENSION OF SPINAL COLLUMN

20
ABDOMINALS

• TRANSVERSE ABDOMINUS - DEPRESSION OF ABDOMEN
• RECTUS ABDOMINUS - SPINAL FEXION
• INTERNAL / EXTERNAL OBLIQUES - ROTATION, LATERAL
  FLEXION (ABDUCTION - ADDUCTION)

21
MUSCLES OF THE THORAX

• DIAPHRAM
• INTERNAL INTERCOSTALS
• EXTERNAL INTERCOSTALS

22
INJURIES TO LOWER SPINE, PELVIS, HIP - CAUSES

• DISK DEGENERATION - Herniation or General
  Degeneration
• JOINT DISFUNCTION - Primarily _at_ Sacroiliac
• Usual Cause - Lack of Normal Movement - Often
  Disputed
• STRETCHED OR STRAINED LIGAMENTS - ie
  Supraspinous Ligaments
• LACK OF STRENGTH
• Hamstrings, Erector Spinae, Abdominals, Hip
  Flexors

23
PREVENTION OF INJURIES TO BACK

• POSTURE - STANDING
• HYPERLORDOSIS
• KYPHOSIS
• POSTURE - SITTING
• CAUSING PAIN TO LUMBO/SACRAL AREA

24
PROPER SITTING TECHNIQUE - Should Not Be Done
Over Long Periods Of Time

• HIPS SHOULD BE FLEXED
• LEGS SHOULD NOT BE EXTENDED
• BACK SHOULD NOT BE OVERLY ARCHED

25
LIFTING WITH PROPER TECHNIQUE

• BACK KEPT ERECT
• KNEES BENT
• WEIGHT CLOSE TO BODY

26
STRENGTHENING EXERCISES

• MANY BACK PROBLEMS ARE CAUSED BY WEAK MUSCLES
  ABOUT THE HIP AND ABDOMINALS
• WEAK MUSCLES PREDISPOSE BACK TO HYPERLORDOSIS
• INCORRECT SIT-UPS MAY CAUSE HYPERLORDOSIS -
  CAUSED BY SHORTENED ILIOPSOAS
• STRETCHING - HAMSTRINGS - ILIOPSOAS - QUADRICEPS

27
LUMBAR SPINE EVALUATIONS

• STANDING EVALUATION
• FLEX FORWARD - PALPATING SPINOUS PROCESSES
  TRANVERSE PROCESSES
• SITTING ALIGNMENT
• PATELLULAR REFLEX - LUMBAR 4 INVOLVEMENT
• ACHILLES REFLEX - SACRAL 1 INVOLVEMENT

28
LYING ON BACK

• TEST ABDOMINALS - RECTUS ABDOMINUS , ILIOPSOAS
  (HIP FLEXORS)
• (STATIC W/ STABILIZED THIGHS - HIP FLEX AT 45
  DEGREES
• STRAIGHT LEG RAISE
• PAIN WHEN TESTING UNAFFECTED SIDE - POSSIBLE
  HERNIATED DISK
• PAIN WHEN TESTING AFFECTED SIDE - POSSIBLE
  SCIATIC NERVE STRETCHED

29
LYING ON BACK (CONTINUED)

• BOWSTRING SIGN
• TO TEST FOR SCIATIC NERVE - USE PRESSURE TO
  POPLITEAL (BACK OF KNEE)
• GAINSLENS SIGN
• TO TEST SACRO-ILIAC LESSIONS (SWITCHBLADE LEGS
  WHILE ON SIDE)

30
OTHER PROBLEMS OCCURING WITH THE SPINE

• SOFT TISSUE TRAUMA - CONTUSIONS
• NERVE INFLAMATION OR COMPRESSIONS - FROM DISK
  PROTRUSIONS
• FRACTURES TO THE SPINOUS OR TRANSVERSE PROCESSES
• SPONDYLOLYSIS (FRACTURE TO INTERARTICULAR PROCESS
• SPONDYLOLISTHESIS (FORWARD SLIPPAGE OF THE
  VERTEBRA

31
OTHER PROBLEMS OCCURING WITH THE SPINE (CONTINUED)

• GROIN STRAINS
• HIP POINTE.RS
• HIP DISLOCATIONS

32
REHABILITATION OF BACK AND HIP INJURY

• ICE MESSAGE
• MOVEMENT TO REGAIN FLEXIBILITY RANGE
• STRENGTHENING EXERCISES
• SIT UPS CRUNCHES (WORK OBLIQUES AS WELL)
• PELVIC TILTS - (FLATTENING OF BACK AGAINST FLOOR)
• HIP LIFTS - (FROM LYING ON BACK POSITION)
• BACK EXTENTIONS - TO 90 DEGREES
• PSOAS HAMSTRING STRETCH - (KNEES TO CHEST)