1. Department of Orthopaedic
Trauma Medicine
Year 1, Sem. 2
Subject – Biomechanics
Topic – Biomechanics of the
Spine & Hip
By
Mr. Oduor Wafulah
11th November, 2021.

2. 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

3. Spinal Deviations
Lordosis
Kyphosis
Scoliosis

4. 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

5. 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.

6. 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.

7. 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
Erector Spinae
Muscles

8. 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 Newton’s
 Segment
Head
Trunk
Arms
Box
Weight
13 lbs. (58N)
73.75 lbs.
18.2 lbs. (81N)
24.95 lbs.
Moment Arm
25 cm
(328N) 10 cm
20 cm
(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)
What Does The Research
• % Load Compression On
L3SDuhrinog twhe ?Upright Standing,
Lying
Down, and Sitting.
• Compression Increases More with
Spinal Flexion, and Increases
Still Further with a Slouched Sitting
Position.

10. 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.

11. Back, Spinal Column, Neck
Vertebral Column
Ribs & Sternum
SPINAL COLLUMN
7 Cervical Vertebrae
12 Thoracic
5 Lumbar
1 Sacrum - Fused
1 Coccyx - 2 Fused

12. Joints of The Vertebral Column
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
Cartilage

13. Sternum
Manubrium
Body
Xiphoid Process
Muscles Of The Back, Neck &
Abdomen
Deep Posteriors
Abdominals
Vertebral
Superficial Neck Muscles

14. 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

15. 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

16. 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 &
Transverse Processes
Sitting Alignment
Patellar Reflex - Lumbar 4 Involvement
Achilles Reflex - Sacral 1 Involvement

17. 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
Occurring With The Spine
Soft Tissue Trauma - Contusions
Nerve Inflammation Or Compressions - From Disk
Protrusions
Fractures To The Spinous Or Transverse Processes
Spondylolysis (Fracture To Interarticular Process
Spondylolisthesis (Forward Slippage Of The Vertebra

18. Other Problems Occurring 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 Oblique's As Well)
Pelvic Tilts - (Flattening Of Back Against Floor)
Hip Lifts - (From Lying On Back Position)
Back Extensions - To 90 Degrees
Psoas & Hamstring Stretch - (Knees To Chest)

19. Questions