biomechanics of the spine & hip

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 SpinaeMuscles

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• SegmentWeight 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.)

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 WeightMoment 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)

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)