WK10 - Shoulder Injuries Flashcards
What joints makes up the shoulder?
- ACJ
- GHJ
- SCJ
- scapulothoracic joint
How do the 4 shoulder joints work together for movement?
- motion (how articular cartilage articulates with glenoid)
- stability
- strength
- smoothness
Why is shoulder movement // treatment so complex?
Not simple ball and socket joint like the hip (that’s why hip replacements work so well)
Shoulder have variable congruity, need muscles to help with control
During movement, it is important that there is restoration/maintenance of GHJ contact patterns
What happens during shoulder ABD?
requires movement at all 4 joints
Rotation through scapula and thus through clavicle for restoration and maintenance of contact patterns
Higher degree of abduction = require less muscular stability because there is more bony stability + glenoid provides more depth for the humeral head to sit properly
What position results in the least amount of contact between the humeral head and glenoid?
At rest
* requires most amount of compression ot hold HH in place
As arm ABD, more SA in contact –> less need for muscular support
Describe the labrum and characteristics of its structure.
is like a shallow saucer - labrum provides more depth for HH to sit
What are the characteristics of the humeral head ball and socket joint?
-Neutral position has least amount of contact surface area with articular cartilage at GHJ
-Concavity compression + rotator cuff hold the humerus into the socket, allowing for better movement of the shoulder allow for abduction to be initiated
-Deltoid is better able to abduct once the humerus head is held in the socket
Define congruity.
bone fits bone perfectly but nowhere for synovial fluid to sit
What are the dynamic and static stabilisers?
dynamic = rotator cuff
static = bones, labrum
What is the role of the rotator cuff in the shoulder?
Doesn’t have total circumferential support doesn’t cover the whole socket
* Bottom of the glenoid is not covered by muscle, only inferior GHL
What is not covered by rotator cuff has ligaments to hold
* Inferior glenohumeral ligament at the bottom
Consider stability vs mobility in the shoulder.
-GHJ has minimal bony constraint, allowing it the largest ROM of any major diarthrodial joint in the human body
-Great mobility of shoulder but must sacrifice stability
What are considerations made towards shoulder replacements?
-Not as simple as a hip replacement due to the complexity of the joint
-Reverse shoulder replacement
*When RC is badly torn/inadequate
*No point putting HH back the way it was if there is no muscular stability
List some labrum shapes.
- inverted comma shaped
- pear shaped
- oval shaped
What is the bare spot on the glenoid and where?
-Not erosion but a developmental area
-Rare in young kids
-Potentially because during shoulder development, it needs more articular cartilage support in the periphery where contact areas are
-Known as the Tubercle of Assaki
*Area of thinning cartilage
Located in the centre of the glenoid - some discolouration
What does the slope of the glenoid contribute to?
how stable the shoulder is
What position does the shoulder sit in?
Doesn’t sit in pure frontal place but in the scapular plane
* glenoid sits in retroversion with SUP tilt
* designed so HH doesn’t slip out easily
Variable congruency requires complex muscular action. T or F?
TRUE!
-As shoulder is ABD, HH becomes more congruent with the glenoid, increasing the contact area and decreasing pressure
-When arm is by your side, deltoid is not well positioned to ABD the arm
* Once RC is recruited, places arm in slightly ABD position for deltoid to do the rest of the work
-RC initiates ABD, deltoid does the rest
What % of gen. population is believed to have rotator cuff disease at any given time?
16%
What does the rotator cuff muscle do?
Initiates the first part of abduction
*Painful arc is between 70-120deg of active ABD
*Not specific or sensitive but increases likelihood of a RC disorder
*Not just 1 diagnostic test which will tell you about the problem, usually a cluster
*Painful arc can be used as a criteria for RTS – should see resolution/restoration of shoulder complex
What is the common RC muscle to be teared and consider the mechanism?
-Usually supraspinatus
-Acute – indirect force in abduction
*Lift tendon off bone partially
*PASTA – partial articular supraspinatus tear with avulsion
–> Usually in younger persons
What does PASTA lesion stand for?
Partial
Articular
Supraspinatus
Tendon
Avulsion
What are the implications of surgical Tx of PASTA lesions?
usually indicated in cases of failure of non-operative treatment or involvement of at least 50% of tendon thickness
Gauge damage from MRI scans
Improves function, relieve pain, and prevents progression and enlargement of tear
Once detached, can retract and make it hard to put it back
What is the prevalence, cause and symptom of chronic tendonitis and degeneration of the shoulder joint?
*Over 45y
*Persistent and night time pain
*Build-up of small damage can lead to an acute tear but it is due to the accumulation of damage
What is Codmans Critical Zone?
-Anastomotic ends
* Blood comes from one end proximally and distally
-Areas that are not well served by blood supply
-Tendons generally don’t have a lot of blood
* Would cause weakness in areas = more tears
How to interpret the graph depicting the effect of angiogenesis-related cytokines on RC disease?
Blood levels of cytokines
Blue – proinflammatory
Red – anti-inflammatory
Green – vascular endothelial growth factors (VEGF)
Purple – opposite of ^
Normal tendon – blue and red are balanced
Tendonitis – blue higher, encouraging blood supply to healing area of tendon
Degeneration and ruptured – large increase in cytokine levels
^ Biomarker can be used to determine severity of RC damage and recovery
What are cytokines?
-Messenger type products
-Produced by macrophages, granulocytes, lymphocyte, mast cell, endothelial cells, fibroblasts
-^ produce cytokines which have Target cells replicate, develop, fight disease, cause cells to stop functioning, involved in cascade responses
What are implications of VEGF?
required for healing but can also weaken the mechanical stability of the tendon
As VEGF (green in above graph) increases, pain also increased
^ associated/correlation?
Factors upregulating VEGF expression in tenocytes: hypoxia, inflammatory cytokines, mechanical load
While VEGF-mediated angiogenesis contributes to repair and remodelling of degenerative tendons, invasion by endothelial cells may also weaken the mechanical stability of the tendon
Why might PRP injections not be worth it?
if you’re reinjecting their own blood back, it doesn’t have the profile you want
What does VEGF have the potential to stimulate?
stimulate expression of matrix metalloproteinases and inhibit expression of tissue inhibitors of matrix metalloproteinases (MMPs) in various cell types
-MMPs initially remove dead tissue then help with breaking down of damaged collagen then aid in reorganization of new tissue in ECM
But MMPs ^ can start to go ‘crazy’, need TIMP (tissue inhibitors) to control/counteract and inhibit MMP activity
-4 known TIMPs
-If VEGF stimulates MMP and inhibits TIMPs = can inhibit healing
Why is a vascular area ideal?
good structural integrity, good ability to stretch (young)
What is hypervascularity?
-Tendon more at risk of tearing, not at footplate but further up
* Delaminates and falls apart
-Differs from acute injury, different injury same tendon structure
Degenerative evidence on picture with pink muscle - long lines of pink and white
Why does the angle of “golf tee” affect amount of acromio-humeral distance/space?
Golf tee - consider HH as golf ball, the tee that articulates with the glenoid
-Increases chance of pain developing during abduction arc (from above) from tubercle bumping into acromion
*As you rotate upwards, need to have sufficient clearance space for everything to move smoothly
*Inadequacy of RC may cause upward migration = decrease amount of space
What is profiling? Consider black and blue lines.
Profiling involves measuring distance of humeral head to greater tuberosity
- Black line should be shorter than blue line
- Need to have the clearance space for abduction
- Ratio should be <1 – closer to 1 means more at risk for bumping
Tear in bone (fracture) instead of RC
- Blood tracking down arm can be indicative of fracture, tendon tear won’t have bruising to such an extent
What is the most common cause of shoulder disability?
RCT - this injury is possibly the most commonly diseased tendon in human body
What is Advanced Glycation End Products (AGE)?
-63% of those with a RCT had elevated serum cholesterol
-Influence of cytokines on tendon tissue
*Infiltration of increased vascularity affect extensibility/expansibility nature of tendon
*Mature person’s tendon won’t be as extensible/expansible/elastic as young person
- Especially with smoking, drinking, diabetes mellitus
While holding the humeral head with the fingers, what does the thumb represent?
= subscapularis
Thumb has 2 ‘blocks’
*In some situations, half of SS is sufficient for function and holding on to humerus
-Some patients (80%) can manage with just subscapularis and supraspinatus
-Will struggle with only supra and infraspinatus
-Pseudo-paralysis – need help with initiation but can manage rest of motion
