119 - Shoulder Trauma Flashcards
What is a dislocation?
Displacement from normal position of a joint - with complete loss of contact surfaces
What is a subluxation?
Partial dislocation - bone ends are still in contact but misaligned
In the shoulder what sort of dislocation is most common?
Anterior more common than posterior
Why does the shoulder dislocate reasonably easily?
The humeral head is bigger than the glenoid fossa - only 1/3 in contact
What complications can occur after recurrent shoulder dislocations?
Bankart lesion - damage to glenoid labrum (in 85% of traumatic dislocations)
Hill’s Sach’s lesion - Cortical depression/fracture of postero-lateral aspect of head of humerus
Auxillary nerve injury - traction as it is in contact with joint capsule
What does an auxillary nerve injury cause?
Deltoid weakness
Reduced sensation in regimental badge area
What adaptations does the shoulder have to improve stability?
Labrum - fibrocartillagenous cuff
Rotator cuff muscles - pull humerus into joint
What position makes the shoulder weakest?
When arm abducts to 90 degrees and externally rotated
What are bones?
Specialised form of connective tissue - Cells and mineralised ECM
What is the function of bones?
Framework Protection Movement Storage (Ca, Phosphorus) Blood cell production
What is the contents of bone?
40% Organic ECM
- 95% collagen (type 1)
- BMPs - bone morphogenic proteins
- Proteoglycans - secreted by osteoblasts
- Phosphoproteins + glycoproteins
60% inorganic ECM - mineral content is unique to bone
- Calcium hydroxyapatitie crystals
- Crystals either inside or outside collagen fibrils
What are the 4 main bone cell types?
Osteoprogenitor - stem cells
Osteoblasts - bone forming - control minerilsation (mesenchymal stem cells)
Osteocytes - make bone, modified osteoblasts
Osteoclasts - remove bone - macrophage like, resporb bone. (haematopoietic stem cells)
What is trabeculat/cancellous bone?
Skeletal bone
Ends of long bones
Spongy in middle
Lost 1st in osteoperosis
What is compact bone/cortical bone?
Concentric layers of dense connective tissue
Hole in middle - less weight
Lamellae structure
Low turnover
What is newly formed bone called?
Osteoid - unmineralised bone
What hormones effect bone formation/resportion?
Parathyroid hormone Calcitonin Oestrogen Testosterone Growth Hormone Vit D
How do osteoblasts and osteoclasts communicate?
RANK-ORG system
Osteoblasts detect the hormones, releases either:
-RANK - > activates osteoclasts - > increase resorption
-OPG -> blocks osteoclast activation -> reduces resportion
Where does bone growth occur?
At the ossification centre - epiphyseal plate
Or secondary eg. Greater trochanter- Apophysis
What is articular cartilage?
Shock absorbers at synovial joint
Elastic and dampening
What allows articular cartilage to have its elastic properties?
Osmotic pressure - as aggrecan holds water well
What bone type is a network of thin, bony plates separated by wide marrow spaces.
canellous bone
What is a Cavity in the bone matrix which is occupied by a bone cell.
lacuna
What bone type is Often characteristic of bone diseases and fracture repair tissue.
Woven bone
What in bone is a small channel which permeates the bone matrix and facilitates cell-to-cell communication.
Canaliculus
