Fractures Flashcards
Peripheral/cortical bone
Highly organised, high density
Most of the weight bearing properties of long bone
Medullary/Trabecular bone
More metabolically active and vascular than cortical bone
Bone marrow
3 phases of bone healing
- inflammation
- repair
- remodelling
Structural damage to bone
Haematoma
Inflammatory mediators
○ Kinins, complement, histamine, serotonin, prostaglandins, leukotrienes
§ Vasodilation,
§ chemotaxis of white blood cells,
§ platelet aggregation and release
§ mesenchymal cell proliferation
Inflammatory phase of bone healing
First 2-3 weeks
Growth factors
Cytokines
Phagocytosis
Fragment end resorption
Often associated with less pain so need to be careful
Least structural strength
Reparative phase of bone healing
2-12 months
Basic patterns of bone repair
- direct repair (also called primary)
- indirect repair (also called secondary)
Remodelling phase of bone healing
12+ months
Bone resorption and formation
Callus -> Haversian remodelling restores normal architecture
Direct repair of bone (primary repair)
requires strict conditions (that are rarely achieved!)
- Anatomic reduction (exact alignment)
- Rigid fixation (usually internal fixation involving implants)
○ Screws only
○ Plates and screws
○ Intramedullary nails…… - Sufficient blood supply
Also: early active and pain free mobilisation
Indirect bone repair (secondary)
Angiogenesis
○ From adjacent tissues (muscles), in early repair
○ From medullary cavity of bone, later in repair
Periosteal and endosteal callus formation
○ Goal = interfragmentary stabilisation
○ Suppressed by rigid immobilisation and excessive mobilisation
Bone union
○ Cancellous bone growth formed by 2 mechanisms:
§ Intramembranous ossification
§ Endochondral ossification
Intergrity of soft tissue cover in fractures
Integrity of blood supply
Protection against infection
Maintain vitalised periosteum
Open fractures
Poor soft tissue cover over distal limb
High impact caused high energy fracture = comminuted
Poor first aid stabilisation – often the initial treatment has big effect on outcome!!
Affects if fractures on the other limbs
Persistent non-weight bearing lameness can induce severe laminitic changes in the supporting limb.
Prolonged pressure within the hoof of the ‘non lame’ limb reduces blood flow to the laminae causing hypoxia. Hypoxia causes inflammation and MMP production.
Multimodal analgesia to get the horse weight bearing on the lame leg.
Risk factors for weight bearing laminitis
Size of horse
Duration of lameness
Severity of lameness
Forelimb (60%) vs hindlimb (40%)
Fractures due to repetitive strain injuries
Repetitive strain injuries prelude many fracture types, particularly in RACEHORSES but seen in other disciplines too.
Microdamage -> Microfracture -> Macrofracture -> Failure
Identifying these cases as early as possible will improve outcomes but is very challenging
Repetitive strain injury of the proximal phalanx
Usually propagate from the sagittal groove in a distal direction, often leaving through the lateral cortex
Always arthrodial, sometimes diarthrodial.
CARE WITH BLOCKING!!
Repetitive strain injury of the lateral condyle of MC3
Usually propagate from site of palmar osteochondral disease (POD)
Fracture propagates proximally and exits through lateral cortex
Often displaced
Early detection improves outcomes!
Surgical repair of Repetitive strain injury of the lateral condyle of MC3
recommended in most of these cases, can be achieved standing or under general anaesthesia.
Radiographic guidance is a minimum requirement.
Computed tomography is now the established gold standard and is increasingly available standing.
Carpal fractures
Most commonly frontal slab fracture of the radial facet of the third carpal bone
Associated with repeated joint medications.
○ Corticosteroids suppress bone remodelling, promotes accumulation of microdamage.
Screw fixation is indicated where possible.
Appendicular stress fractures
Distal tibia
Associated with appreciable and blockable lamenesses
Characteristic clinical signs – variable lameness that improves with work
Axial stress fractures
Harder to identify than appendicular fractures
Pelvis
Vertebral bodies
Clinical signs are much less specific - gait abnormalities, poor form
Fractures due to supraphysiological events
An acute increase in the demands of a tissue
· Beyond its safety factor
· May or may not be preluded by microdamage
Think – fast work, changes of direction, changes of surface type
Identification is usually fairly easy.
Fractures of the distal phalanx
Increased digital pulse, sensitivity on hoof testers, pain on flexion.
There are many types with different treatment options based on the location and extent of the fracture
These fractures often heal with fibrous malunion rather than cancellous bone meaning they will remain radiographically visible (navicular bone fractures often do the same).
Splint bone fractures
Splint bone fractures are very common (may also sit in the “external trauma” category)
Can be complete or partial, and often heal with a significant callus (exostosis)
Distal third of bone is not adhered to MC/MT3 – can easily remove
Proximal two thirds are adhered to MC/MT3 – interosseous ligament
Proximal end articulates with TMT/CMC joint – cannot remove!
Most respond well to rest (box or field) and NSAIDs – resolution of lameness in 4-8 weeks.
A large bony callus remains, sometimes for life.
Proximal sesamoid bone fractures
Often occur during fast work.
Apical, basilar, mid-body…
Comminuted, displaced, biaxial, bilateral…
Think about suspensory branches!
Need scanner to give prognosis - soft tissues
Fractures due to external trauma
Think about areas where large weightbearing long bones are close to the skin surface..
· Dorsomedial radius
· Dorsomedial tibia
· MC/MT3
If there is any chance there is trauma to these areas - x-ray it!
Cross tying for the managment of fractures
· Lead ropes to both sides of head collar
· Food and water raised
· MUST let head down every 4 hours
For restricting movement in a known case of long bone fracture (if non-displaced)
Preventing them lying down as getting down and up is highest risk time
For buying time until repeat imaging (10d) in cases with high suspicion but no imaging findings
Emergency fracture stabilisation
Displaced fractures above carpus/tarsus almost impossible to heal - euthanasia
Cannon bone fracture also very hard to fix in adult horse- implants just aren’t available
Fractures during anaesthetic recovery
Most long bones are at risk!
Surgical reduction is the ultimate aim if the horse is a good candidate
First aid for olecranon fractures – splint the carpus -> Acts as a crutch!
