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
Spinal Deviations
• Lordosis
• Kyphosis
• Scoliosis
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
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.
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 Force’s Line of
Action And The Axis
• To Maintain An Upright Position
– Torque Is Counteracted by Tension in the Back
Extensor Muscles.
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
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.
Question: How Much Torque Is Developed By
The Erector Spinae Muscles With a Fm 6 cm?
• 1 lb. = 4.448 Newtons
• Segment
Weight
–
–
–
–
Head
Trunk
Arms
Box
13 lbs. (58N)
73.75 lbs.(328N)
18.2 lbs. (81N)
24.95 lbs.(111N)
Moment Arm
25 cm
10 cm
20 cm
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.)
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 L5S1 joint center to maintain the body in a lifting
position with segment moment arms as Specified?
• Segment
– Head
– Trunk
– Arms
– Box Lifted
Weight
50 N
280 N
65 N
100 N
Moment Arm
22 cm.
12 cm.
25 cm.
42 cm.
• Torque ?
• 10,285 Ncm
• Fm = 1714 N or (393 lbs. Force)
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.
Common Injuries Of The Back
–
–
–
–
–
–
Low Back Pain
Soft Tissue Injuries
Acute Fractures
Stress Fractures
Disc Hernia ions
Whiplash Injuries
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.
BACK, SPINAL COLLUMN,
NECK
• VERTEBRAL
COLLUMN
• RIBS & STERNUM
SPINAL COLLUMN
• 7 CERVICAL
VERTEBRAE
• 12 THORACIC
• 5 LUMBAR
• 1 SACRUM - FUSED
• 1 COXCYC - 2 FUSED
JOINTS OF THE VERTEBRAL
COLLUMN
• VERTEBRAL JOINTS
–GLIDING JOINTS SLIGHTLY MOVABLE
• SEPARATED BY
INTERVERTEBRAL DISKS
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
STERNUM
• MANUBRIUM
• BODY
• XIPHOID PROCESS
MUSCLES OF THE BACK,
NECK & ABDOMEN
• DEEP POSTERIORS
• ABDOMINALS
• VERTEBRALS
• SUPERFICIAL NECK
MUSCLES
DEEP POSTERIORS
• MOVEMENT - ROTATION,
EXTENSION OF SPINAL
COLLUMN
ABDOMINALS
• TRANSVERSE ABDOMINUS
- DEPRESSION OF
ABDOMEN
• RECTUS ABDOMINUS SPINAL FEXION
• INTERNAL / EXTERNAL
OBLIQUES - ROTATION,
LATERAL FLEXION
(ABDUCTION ADDUCTION)
MUSCLES OF THE THORAX
• DIAPHRAM
• INTERNAL INTERCOSTALS
• EXTERNAL INTERCOSTALS
INJURIES TO LOWER SPINE,
PELVIS, HIP - CAUSES
• DISK DEGENERATION - Herniation or General
Degeneration
• JOINT DISFUNCTION - Primarily @ 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
PREVENTION OF INJURIES
TO
BACK
• POSTURE - STANDING
– HYPERLORDOSIS
– KYPHOSIS
• POSTURE - SITTING
– CAUSING PAIN TO LUMBO/SACRAL AREA
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
LIFTING WITH PROPER
TECHNIQUE
• BACK KEPT ERECT
• KNEES BENT
• WEIGHT CLOSE TO BODY
•
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
LUMBAR SPINE
EVALUATIONS
• STANDING EVALUATION
• FLEX FORWARD PALPATING SPINOUS
PROCESSES &
TRANVERSE PROCESSES
• SITTING ALIGNMENT
• PATELLULAR REFLEX LUMBAR 4
INVOLVEMENT
• ACHILLES REFLEX SACRAL 1
INVOLVEMENT
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
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)
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
OTHER PROBLEMS
OCCURING WITH THE SPINE
(CONTINUED)
• GROIN STRAINS
• HIP POINTE.RS
• HIP DISLOCATIONS
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)