Announcements

1
Announcements

• Critiques and Midterm Exams
• Grading in progress
• Critique 2 not due till April 2nd
• Plan here on out
• Finish up Muscle and Force Production
• Shoulder Hip Biomechanics
• Knee Biomechanics

2
Biomechanics of the Upper Extremity Shoulder
and Hip

• ESS 5310-001
• Lecture 9
• Reading WZ Chapter 7 6

3
The ShoulderCommon Injuries
4
Shoulder Joint - Bones
5
Anatomical Structures

• Bursa
• Fibrous, fluid-filled sac that reduces friction
• Located between bones, tendons, and other
  structures
• Subacromial Bursae
• Bursa between acromion process and insertion of
  supraspinatus muscle
• Coracoid Process
• Curved process arising from upper neck of scapula
• Overhangs shoulder joint

6
Shoulder - Anatomical Structures

• Shoulder Girdle
• An incomplete bony ring in the upper extremity
  formed on each side by the scapula and clavicle
• Scapula
• Flat, triangular bone on the upper posterior
  thorax
• Clavicle
• Long, narrow S-shaped bone articulating with
  scapula and sternum
• Collar bone
• Glenoid Fossa
• Depression in lateral superior scapula
• Socket for shoulder joint
• Glenoid Labrum
• Ring of fibrocartilage around rim of glenoid
  fossa
• Deepens socket for shoulder joint

7
The Shoulder ComplexArticulations

• Sternoclavicular Joint
• Articulation between sternum and clavicle
• Acromioclavicular Joint (AC joint)
• Articulation between acromion process of scapula
  and lateral end of clavicle
• Scapulothoracic Joint
• Physiological joint between the scapula and
  thorax
• Glenohumeral Joint
• Articulation between the head of the humerus and
  the glenoid fossa of the scapula

8
Movements of the Shoulder Complex

• Scapula
• Rotation
• Upward Downward
• Elevation Depression
• Protraction Retraction
• Glenohumeral
• Flexion Extension
• Abduction Adduction
• Horizontal Abduction and Adduction
• Internal External Rotation
• Dislocation

9
Movement Characteristics

• - Large range of motion (ROM) at shoulder
• Extreme ROM required by many activities
• Ex. Swimming, throwing, gymnastics
• - Ligaments and muscles provide stability (and
  sometimes instability)
• - Scapular and clavicular movements accompany any
  arm movement
• - Scapulohumeral Rhythm
• Movement relationship between humerus scapula
  during arm raising movements

10
Sowhat creates stability?
11
Shoulder Joint - Ligaments
12
Shoulder Rotator Cuff
13
Muscular Actions

• Rotator Cuff (muscles)
• Holds humerus in socket
• Stabilizes shoulder joint
• Four (4) muscles surrounding the shoulder joint
• Infraspinatus
• Supraspinatus
• Teres Minor
• Subscapularis

14
Shoulder Muscle Strength

• Generate greatest strength in adduction (why?)
• Abduction used frequently in daily living
• Overhead work, lifting, reaching etc.
• Weakest movements are internal and external
  rotation (why?)
• Muscles generate high forces within joint
• 90 body weight load at 90 abduction
• What are some implications of these facts?

15
Conditioning

• Shoulder muscles easy to stretch and strengthen
• Stretching
• Active and passive
• Strength Training
• Weight training, limb/body weight exercises
• lt 5 lbs resistance (slow and controlled)
• Rotator cuff strength and flexibility important
• Stabilization of joint
• Widely used in daily living

16
Conditioning Exercises
17
Contributions of Shoulder Musculature

• Activities of daily living
• Freestyle swimming
• Overhand throwing
• Golf swing

18
Muscle Roles - Example
19
Injury to the Shoulder Complex

• Wide variety of possible injuries
• Two Main Causes
• Trauma
• Repetitive joint actions
• Certain groups are more susceptible to certain
  injuries
• Adolescents - Subluxations
• Contact sport players - Fractures

20
Injury

• Sprain
• Rupture of fibers of ligament
• Subluxation
• Partial dislocation
• Fracture
• Break in bone, often clavicle
• Ectopic Calcification
• Hardening of organic tissue through deposit of
  calcium salts in areas away from the normal sites
• Degeneration
• Deterioration of tissue

21
Injury

• Bursitis
• Inflammation of bursa
• Impingement Syndrome
• Irritation of structures above shoulder joint
• Due to repeated compression between greater
  tuberosity and acromion process
• Subacromial Bursitis
• Common from impingement syndrome
• Bicipital Tendinitis
• Inflammation of the tendon of the biceps brachii

22
Summary of Structures
23
Shoulder - Summary Questions

• What does the shoulder complex enable us to do?
• What stabilizes the structures of the shoulder?
• What are potential injuries to the shoulder?
• What causes these injuries?
• How can injuries be prevented?
• What are some exercises for stretching and
  strengthening the shoulder complex?

24
Part 2Hip
25
Hip StructureHow does it differ from the
shoulder?
26
The HipCommon Injuries
27
Hip FunctionHow do we use it?
28
Overview

• Part 1
• Structure
• Function
• Kinematics
• Range of motion (ROM)
• Surface joint motion

• Part 2
• Kinetics
• Statics
• Single Leg Stance, Two-leg Stance, Influence of
  body COM
• JRF Calculation
• Dynamics
• JRF during gait and locomotion
• Ambulatory Aides

29
Hip Joint

• Largest and most stable joint in human body
• Intrinsic Stability
• Rigid ball and socket
• Mobility in three planes
• Sagittal
• Frontal
• Transverse
• Regularly endures very large forces

30
Hip Joint Structure

• Hip Joint
• Head of femur
• Acetabulum of pelvis
• Recall pelvis is three fused bones
• Loose joint capsule
• Large ROM

31
Hip Joint Structure

• External Iliac artery
• Psoas major
• Iliacus muscle
• Iliac crest
• Gluteus medius
• Gluteus minimus
• Greater trochanter
• Vastus lateralis
• Femoral shaft
• Vastus medialis
• Profunda femoris vessels
• Adductor longus
• Pectineus
• Medial circumflex femoral vessels
• Capsule of the hip joint
• Femoral neck
• Zona orbicularis of capsule
• Head of femur
• Acetabular labrum

32
Structure and Function

• Muscles of hip joint (previous slide)
• Identify muscles
• Locations of origin and insertion
• Distinguish function
• Bones and capsular structure (next slide)
• Muscle-Tendon
• Ligaments
• Cartilage

33
Joint Capsule
34
Hip Joint Structure
35
Hip Joint Structure
36
Hip Musculature
37
Acetabulum

• Alignment of cavity
• Obliquely, forward, outward and downward
• Deep
• Provides static stability
• Deepened further by labrum and transverse
  acetabular ligament
• Flat rim of fibrocartilage
• Unloaded
• Smaller diameter than femoral head
• Loaded
• Deforms about the femoral head
• Elastic deformation

38
Femoral Head

• Ball of the ball and socket
• Convex component
• Shape forms 2/3 of a sphere
• Variation in articular cartilage thickness
• Due to variation in loading patterns
• Results in different strength and stiffness
  across different regions of the joint

39
Femoral Neck

• Angular relation with femoral shaft
• Neck to Shaft Angle
• Angle of inclination of neck to shaft in frontal
  plane
• Freedom of motion
• Adults 125º (90º-135º)
• Angle of Anteversion
• Angle of inclination in transverse plane
• Projection of the long axis of femoral head and
  transverse axis of femoral condyles
• Adults 12º

40
Neck to Shaft Angle

• Coxa Valga
• Angle gt 125º
• Coxa Vara
• Angle lt 125º
• Excess angle
• Affects moment created by gravity
• Affects muscle moment arm
• Affects muscle effort

41
Angle of Anteversion

• Angle gt 12º
• Anteversion
• Portion of head is uncovered
• Internal rotation during gait
• To keep femoral head in cavity
• Angle lt 12º
• Retroversion
• Tendency toward external rotation during gait
• Anteversion and retroversion are common in
  children
• Typically outgrown during maturation

42
Hip Joint Loading

• Medial and Lateral Trabeculae Systems
• JRF of femoral head parallels the trabeculae in
  femoral neck
• Epiphyseal plates are perpendicular to trabeculae
  of medial system
• Thus, perpendicular JRF in femoral head
• Abductor group contraction resists compressive
  forces in lateral region
• Gluteus medius, Gluteus minimus, Tensor fascia
  latae
• Aging Femoral Neck
• Cortical bone thins
• Trabeculae is resorbed
• May predispose neck to fracture

43
Hip Joint Kinematics

• Range of Motion (ROM) in 3 planes
• Sagittal
• 0-140º Flexion
• 0-15º Extension
• Frontal
• 0-30º Abduction
• 0-25º Adduction
• Transverse
• 0-90º External rotation
• 0-70º Internal rotation (with hip flexed)

44
Hip Joint Motion During Gait

• Flexion-Extension (35-40º)
• Max flexion in late swing
• Max Extension at heel off
• Abduction-Adduction (12º)
• During swing
• Max abduction just after toe-off
• Max adduction at heel strike through late stance
• External-Internal Rotation ( 13º)
• ER through swing
• IR into heel strike through late stance

45
Hip Joint Motion During Gait
46
Aging and Hip Joint Motion

• ROM decreases with age
• During gait
• Shorter stride
• Decreased hip flexion-extension
• Decreased plantarflexion
• Decreased heel-floor angle of tracking limb
• Decreased dorsiflexion
• Decreased elevation of toe on forward limb

47
ROM During Daily Activities

• Necessary Hip ROM
• Flexion 120º
• ER 20º

48
Surface Joint Motion

• Gliding of femoral head in acetabulum
• Incongruence in femoral head
• Abnormal gliding
• Abnormal compression and/or distraction
• Increased wear
• Pain and degeneration

49
SummaryPart 1 Structure, Function Kinematics

• Structure
• Function
• Kinematics
• Range of motion (ROM)
• Surface joint motion

50
Part 3Kinetics and Ambulatory Aids
51
Hip Joint Kinetics

• Abductor group is main stabilizer during single
  leg stance
• Implications for lower extremity injury?
• i.e., weakness in abductor group

52
Statics

• 2-leg stance
• Gravity line passes through pelvic girdle
• Thus, hip joint is fairly stable
• No muscle force necessary to maintain stance
• Assume each leg is 1/6 body weight
• What is the magnitude of JRF on each hip?
• So, what function would muscle force serve?
• Would it increase or decrease JRF?

53
Statics

• Single leg stance
• COM shifts (line of gravity) in all 3 planes
• Thus, moments are created
• These moments are controlled by muscle force
• COM shift is position dependent
• Shift in gravity line
• Shift in moment arm of gravity (through COM)
• Change in muscle torque required to hold position
• Thus, change in JRF

54
Frontal Plane COM (gravity line)

• Single Leg Stance
• A Neutral stance
• B Max tilt toward support limb
• C Tilt away from support limb
• D Pelvic sagging away from support limb
• Trendelenburgs Test (sign)

55
Frontal Plane COM (gravity line)
56
JRF Calculation

• Two general methods
• Simplified FBD
• JRF in frontal plane acting on femoral head
  during single leg stance
• Equilibrium with neutral pelvis
• Box 8-1
• Use equilibrium equations
• JRF on femoral head using equilibrium equations
  for single leg stance with pelvis level
• Box 8-2

57
Necessary Information

• Location of external forces
• Gravitational force of body (GRF)
• Stance leg and remaining
• Two free bodies
• Divided across hip joint
• Coplanar forces acting on these two bodies are
  then determined
• Box 8-2-2

58
Simplified FBD

• Two moments are required for stability
• A Muscle
• W VGRF
• J - JRF
• ?M 0
• MAbductors MBodyweight

59
Equilibrium Calculation
Textbooks slight of hand Magnitude of A was
found by ((5/6)Wb)/c where b and c were
determined by imaging Direction of A (30º) was
determined by imaging
60
JRF Calculation
?Fx 0 ?Fy 0 Known W and A Find Jx and
Jy Find J Find ?
61
Influence of Moment Arms

• Abductor Moment Arm (c)
• Gravitational Moment Arm (b)
• Ratio c/b
• Low ratio
• Small c
• Large b
• Yields greater JRF
• Short Abductor Moment Arm
• Typical in Coxa Valga
• Small ratio
• Elevated JRF
• Hip Replacement Surgery
• Movement of greater trochanter laterally
• Increases muscle moment arm
• Decreases JRF (adding life to new joint)

62
Dynamics

• JRF during walking
• Lower JRF in women
• Wider pelvis
• Different inclination of femoral neck-to-shaft
• Different general gait pattern

63
DynamicsMuscle Action
64
Peak JRFDuringGait

• Stair Gait
• 2.6 to 5.5 BW
• Running Skiing
• 8 BW
• JRF Peaks
• Hip flexion 100º
• Stair decent
• Low chair rise

65
Hip Joint Loading and Injury

• Abductor group contraction resists compressive
  forces in lateral region
• Gluteus medius, Gluteus minimus, Tensor fascia
  latae
• Aging Femoral Neck
• Cortical bone thins
• Trabeculae is resorbed
• May predispose neck to fracture

66
Hip Fracture

• Result from high energy forces
• Falls, automobile crashes
• Pelvic Fractures
• Not as common as femoral fractures
• 15,300 cases occur from motor vehicle crashes
• Side impacts at lower speeds compared with
  frontal
• High mortality rates

67
Femoral Fracture

• Proximal Femoral Fractures
• 250,000 fractures annually in U.S.
• Fracture rate increases with advanced age
• Women more than men
• Femoral fractures in young people
• High energy causes (e.g. motor vehicle crashes)
• Injury associated with hip luxation

68
Femoral Neck Fracture

• Mechanisms
• Direct impact to greater trochanter
• Fall (lateral rotation during backward fall)
• Injury in Young People (rare)
• Repeated loading during strenuous activity
• Injury in Older People
• Falls associated with trips or unsteady gait
• Which occurs firstfall or fracture?
• Falls resulting in hip fracture
• Only 5 of falls
• Other tissues are absorbing energy of impact
• Risk of hip fracture is lower in people with
  large BMI
• Cushion?
• Outstretched arms also may brake fall and prevent
  hip fracture
• At the expense of wrist fracture

69
Predisposing Factors for Falls
70
Osteoporosis

• Diminished strength
• Increased likelihood for fracture
• Dynamics of fall may actually be mechanism of
  fracture
• Other factors influencing hip fracture incidence
• Bone quality, muscle strength, soft tissue
  characteristics, as well as neuromuscular
  coordination

71
Hip Luxation or Dislocation

• Dislocation
• Rare due to high joint stability
• Requires tremendous force
• Motor vehicle accidents
• Falls from height
• Skiing accidents
• Often accompanied by accompanying fracture of
  acetabulum, proximal femur or both
• Mechanism
• Force applied to greater trochanter, flexed knee,
  foot with ipsilateral knee extended and rarely
  posterior pelvis
• Applied force translates and rotates femur
• Forces cause posterior dislocation of femur
  relative to acetabulum

72
Dashboard Collision

• Violent collision of occupants knee against
  dashboard
• Result
• Posterior dislocation often accompanied by
  acetabular or femoral fracture

73
Anterior Hip Luxations

• Rare
• 10-20 of all dislocations
• Forceful abduction (primary factor)
• Hip abduction, flexion and external rotation
• Femoral neck or trochanter presses against rim
  of acetabulum and leverages the head out of the
  socket forward
• Pubic-type or Iliac-type Luxation
• Hip extension coupled with abduction

74
Osteoarthritis (OA)

• Osteoarthrosis
• Degenerative Joint Disease (DJD)
• Most common joint disorder
• Does not initially manifest as inflammation
• Inflammation is secondary to tissue degeneration
• Thus DJD is more appropriate designation
• OA is progressive
• Softening of articular cartilage, with decrease
  in matrix proteoglycan
• Cartilage thins
• Surface roughens (pitting, fissures, ulcerations)
• Damage results in enzyme release which further
  breaks down the tissue
• Bone necrosis may follow in advanced stages

75
OA

• Associated with advanced age
• Common in people 75 years and up
• Onset and progression
• Feet (likely first site affected, MP joints)
• Progresses up kinematic chain to hip
• Site onset in low extremity
• MP IP Tibiofemoral Hip
• Areas of highest impact down??
• Primary cause of OA still unclear
• Idiopathic
• Overuse (acute or chronic)
• Obesity is not strongly associated with OA at hip
• But obesity is highly related with knee OA

76
External Support

• Ambulatory Aides
• Walking with a cane
• On which side should the cane be used?
• Why?

77
Ambulatory AidesProper Use
78
SummaryPart 3 Kinetics and Ambulatory Aides

• Kinetics
• Statics
• Single Leg Stance
• Two-leg Stance
• Influence of body COM
• JRF Calculation
• Dynamics
• JRF during gait and locomotion
• Ambulatory Aides

79
Overall Summary

• Hip Structure and Function
• General Kinematics and Kinetics
• Injury
• Kinetics
• JRF during gait and locomotion
• Injury and Dysfunction
• Fracture
• Luxation
• OA
• Ambulatory Aides

80
General Summary Questions

• What do the shoulder and hip joints enable us to
  do?
• What stabilizes these structures?
• What are potential or common injuries to the
  shoulder? What causes these injuries?
• What are potential or common injuries to the hip?
  What causes these injuries?
• How can injuries be prevented?
• What are some exercises for stretching and
  strengthening the hip and shoulder?

81
For Next Time

• Lower Extremity
• Thigh and Shank
• Knee