Midterm 1 Flashcards
MSD
Musculoskeletal Disorder
WMSD
Work related Musculoskeletal Disorder
UEMSD
Upper Extremity Musculoskeletal Disorder
CTD
Cumulative Trauma Disorder
Two ways visible disease changes?
1) How much disease there is
Changes in population body weight, major shifts in working conditions
2) Awareness of disease
Able to see more clinical disease when people are able to know and identify it - i.e. carpel tunnel syndrome
Tissue Types for UEDs
Tendon Muscle Nerve Vascular Bursal Bone & Cartilage Ligament Fascia
Approximate cost of compensated shoulder injuries in Canada?
$60,000 direct cost + $60,000 indirect cost / injury
$1,170,000 Total
Function of tendon
transmit force from a muscle to a bone (only linearly, not transverse)
Tendon Disorders
Excessive / Incorrect Loading
Results inflammation and then deformation & tears
Function of muscle
Actuators of the lever system of the skeleton:
- initiate/maintain motion/force transmission
- joint stabilization
Muscle Disorders
external forces on passive tissues
straining sarcomeres with eccentric contractions
Function of nerves
send signals throughout the body
Nerve Disorders
Entrapment from muscle, bone, tendon, ligament
Function of vasculature
Material highway to/from cells for normal function
Vasculature Disorders
Ischemia through occlusion / constriction / obstruction
Function of Bursa
sac-like body cavity to reduce stress in a joint
Bursa Disorders
Friction and trauma
Function of Bone
Form - structure & protection
Function - muscle attachment to allow motion
Factories - production of material
Function of Cartilage
Force, support, shock absorption
Bone and Cartilage Disorders
Inflammation and degeneration
Stability and Mobility of the Shoulder
Most mobile
Most instable
Stability and Mobility of Sternoclavicular Joint
SC joint has good stability - provided by costoclavicular ligament
Very limited ROM
Degrees of Freedom for SC Joint
1 - Elevation / Depression (30-35)
2 - Anterior / Posterior (35)
3 - Long Axis (40-45)
Kinematic Redundancy
able to get to distal segment through multiple proximal segments
i.e. shoulder girdle to hand
Degrees of Freedom for Scapulothoracic Gliding Plane
1 + 2 - Translational
3 - Tipping
4 - Rotation
5 - Protraction / Retraction
GH Joint Movements
Abduction - 150
Flexion - 180
External/Internal Rotation - 90
GH Stability Contributors
Muscle Action Ligaments Joint Suction Adhesion Bony Constraints
Functions of Shoulder Muscles
Position glenoid for maximum mobility
Articulate the upper arm
Ensure GH stability
provide humeral and whole arm stiffness
Bipedalism
Upper extremity functional differentation
Allows for tool use
Bone Structure of Chimpanzee compared to Human
More superior clavicle = more superior glenoid
Clavicle orients scapula posteriorly - deals with gravity forces better when quadriped
What are the benefits to a suprolateral glenoid?
What are the benefits to a lateral glenoid?
Superolateral = better at moving arms overhead, and body weight transferring (quadripedalism, swinging) Lateral = better at bringing arms together to allow for intricate tool use in field of vision
What are the benefits to a suprolateral glenoid?
What are the benefits to a lateral glenoid?
Superolateral = better at moving arms overhead, and body weight transferring (quadripedalism, swinging) Lateral = better at bringing arms together to allow for intricate tool use in field of vision
Differences in hand and forearm musculature in Humans compared to Chimpanzees
short fascicle length = decreased shortening velocity = decreased force = increased precision
physiological cross-sectional area decreased = lower force capabilities
smaller motor unit size = precision control
Differences in distal radial surface morphology?
Chimpanzees have a distal project which locks wrist in place to be able to transmit force while walking quadripedally, decrease wrist extension ability compared to humans
Hand differences between chimpanzees and humans?
Longer grasping fingers in chimps = gross grip and weight support
Long thumb length in humans = precision grip and tool usage
What are upper extremity advantages humans have?
Fine motor control = material manipulation and tool use
Long range, high speed throwing = distance protection
Prevalence of Proximal Humerus Fractures
Low risk
Increases with age
Women at an increased risk - osteoporosis
Mechanisms of Humerus Fractures
FOOSH
Trauma
Classification types of Humerus Fractures
Kocher - based on location of break (greater tuberosity, lesser tuberosity, head, shaft)
Neer - based on number of fragments (2 part vs. 3 part vs. 4 part and classes based on what area fractured)
AO - based on vasculature supply (absence, partial isolation and complete de-vascularization)
Clinical Features of Proximal Humerus Fractures
Pain Swelling Tenderness Crepitis Ecchymosis
Diagnosis of Proximal Humerus Fractures
X-Ray - 3 views
Treatment of Proximal Humerus Fractures
Initial immobilization - cast Closed reduction Skeletal Traction ORIF Internal prosthesis (complete joint replacement)
Complications of Humeral Fractures
Vascular injury Brachial Plexus injury Frozen shoulder avascular necrosis nonunion malunion
Prevalence of Scapula Fractures
Very rare
Hard to get to, very well protected by muscle + able to compensate for force by moving in 5 planes of motion
Typically at body or glenoid neck
Mechanisms of Scapular Fractures
Lots of force required
How does damage to glenoid occur with scapula fractures?
Glenoid rim = combination of compression and shear force
Glenoid fossa = lots of compression only
Clinical Features of Scapular Fractures
Pain
Local tenderness
Swelling
Crepitus
Diagnosis of Scapula Fracture
X-ray
Classification of Scapula Fractures
Fractures at glenoid neck categorized by location
Type 1 = minimal displacement (more popular)
Type 2 = displacement
Treatment of Scapula Fractures
Typically conservatively when nondisplaced
Scapula Fractures and Double Displacement of the SSSC
Superior Shoulder Suspensory Complex makes a ring at the GH joint
Major instability of the shoulder occurs when ring becomes broken and incomplete
Prevalence of Clavicle Fractures
Frequent fracture and shoulder injury
Mechanisms of Clavicle Fractures
Direct and indirect force
FOOSH - main cause
Buckling of clavicle - forces applied at shoulder towards sternum
Stress Fractures
Clinical Features of Clavicle Fractures
Skin tenting Drooping shoulder Pain Ecchymosis Angled head to reduce trapezius pull Fully supported arm weight
Diagnosis of Clavicle Fractures
X-ray
Classification of Clavicle Fractures
Group 1 = break at S bend (most common)
Further broken down to (A=transverse, B=Wedge, C=comminuted)
Group 2 = break at AC joint side
Further broken down to (Type 1 = intact AC, Type 2 = torn AC)
Group 3 = Break at SC joint side
Treatment of Clavicle Fractures
Sling support
ORIF
OREF
Typically conservative
Complications of Clavicle Fractures
Nonunion
Malunion
Neuro-vascular Sequelae
Post-traumatic arthritis
Humeral Head Differences
Humans have lower torsion = increased internal/external rotation = increased angular displacement = increased throwing velocity
Clavicle Differences
Chimps = thicker clavicle = increased force absorption = better at weight bearing
Scapula Differences
Chimps = superiolateral glenoid = increased arm flexion / decreased arm extension = better overhead reaching
Superiolateral glenoid = pec major pulls medially + inferiorly = overhead reaching
humans = lateral glenoid = pec major horizontally adduction
Supraspinatus Differences
Chimps = bigger = better at weight bearing through U.E.
Forearms Differences
Primates able to supinate = tool use overall
Humans = less curves + lighter = less force required to move = increased precision movements
Elbow Differences
Humans = increased moment arm with flexed elbow Chimps = increased moment arm with extended elbow Chimps = deeper trochlear notch = increased stability with extended arm / decreased ROM of arm
Laxity vs Instability
Laxity = asymptomatic, passive translation in joint Instability = pathological, pain/discomfort/excessive translation
Laws of GH Stability
1 - Dislocations will not occur if the Net Humeral Joint Reaction Force (NHJRF) is directed within the effective glenoid arc
2 - Humeral head will remain centred in the glenoid fossa if the glenoid and humeral joint surfaces are congruent and NHJRF is directed within the effective glenoid arc
Net Humeral Joint Reaction Force (NHJRF)
Combination of:
Active Muscle Contraction + Passive Muscle Stretch + Inertial Forces + Gravitational Forces + External Forces
Effective Glenoid Arc
Arc of the glenoid available to support the head of the humerus in a given direction
Components of GH Stability
Statically: Articular Version Articular Conformity Labrum Intra-Articular Pressure Ligaments Adhesion Suction Cup Dynamically: Active Muscle Contraction & Proprioception
Articular Version
Orientation of glenoid
- 30 degrees frontal plane
- 3 degree upward rotation = small shelf for removing gravity force
Articular Conformity
radii differences between humeral head and glenoid articular surface
Labrum
Increases surface area = provides concavity compression
concavity compression = compression of labrum creates a deeper fossa for increased stability
Intra-articular Pressure
limits translation + controls rotation
vital stability while inactive
medium pressure is desired
Ligaments and Shoulder Stability
mostly passive - increasing ROM
keep joint in position
active during extreme postures - deviations from scapular plane and elevation
