Fractures

Question 1

Peripheral/cortical bone

Answer 1

Highly organised, high density

Most of the weight bearing properties of long bone

Question 2

Medullary/Trabecular bone

Answer 2

More metabolically active and vascular than cortical bone

Bone marrow

Question 3

3 phases of bone healing

Answer 3

1. inflammation
2. repair
3. remodelling

Question 4

Structural damage to bone

Answer 4

Haematoma

Inflammatory mediators
○ Kinins, complement, histamine, serotonin, prostaglandins, leukotrienes
§ Vasodilation,
§ chemotaxis of white blood cells,
§ platelet aggregation and release
§ mesenchymal cell proliferation

Question 5

Inflammatory phase of bone healing

Answer 5

First 2-3 weeks

Growth factors

Cytokines

Phagocytosis

Fragment end resorption

Often associated with less pain so need to be careful

Least structural strength

Question 6

Reparative phase of bone healing

Answer 6

2-12 months

Basic patterns of bone repair
- direct repair (also called primary)
- indirect repair (also called secondary)

Question 7

Remodelling phase of bone healing

Answer 7

12+ months
Bone resorption and formation
Callus -> Haversian remodelling restores normal architecture

Question 8

Direct repair of bone (primary repair)

Answer 8

requires strict conditions (that are rarely achieved!)

1. Anatomic reduction (exact alignment)
2. Rigid fixation (usually internal fixation involving implants)
   ○ Screws only
   ○ Plates and screws
   ○ Intramedullary nails……
3. Sufficient blood supply

Also: early active and pain free mobilisation

Question 9

Indirect bone repair (secondary)

Answer 9

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

Question 10

Intergrity of soft tissue cover in fractures

Answer 10

Integrity of blood supply

Protection against infection

Maintain vitalised periosteum

Question 11

Open fractures

Answer 11

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!!

Question 12

Affects if fractures on the other limbs

Answer 12

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.

Question 13

Risk factors for weight bearing laminitis

Answer 13

Size of horse

Duration of lameness

Severity of lameness

Forelimb (60%) vs hindlimb (40%)

Question 14

Fractures due to repetitive strain injuries

Answer 14

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

Question 15

Repetitive strain injury of the proximal phalanx

Answer 15

Usually propagate from the sagittal groove in a distal direction, often leaving through the lateral cortex

Always arthrodial, sometimes diarthrodial.

CARE WITH BLOCKING!!

Question 16

Repetitive strain injury of the lateral condyle of MC3

Answer 16

Usually propagate from site of palmar osteochondral disease (POD)

Fracture propagates proximally and exits through lateral cortex

Often displaced

Early detection improves outcomes!

Question 17

Surgical repair of Repetitive strain injury of the lateral condyle of MC3

Answer 17

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.

Question 18

Carpal fractures

Answer 18

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.

Question 19

Appendicular stress fractures

Answer 19

Distal tibia

Associated with appreciable and blockable lamenesses

Characteristic clinical signs – variable lameness that improves with work

Question 20

Axial stress fractures

Answer 20

Harder to identify than appendicular fractures

Pelvis

Vertebral bodies

Clinical signs are much less specific - gait abnormalities, poor form

Question 21

Fractures due to supraphysiological events

Answer 21

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.

Question 22

Fractures of the distal phalanx

Answer 22

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).

Question 23

Splint bone fractures

Answer 23

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.

Question 24

Proximal sesamoid bone fractures

Answer 24

Often occur during fast work.

Apical, basilar, mid-body…

Comminuted, displaced, biaxial, bilateral…

Think about suspensory branches!

Need scanner to give prognosis - soft tissues

Question 25

Fractures due to external trauma

Answer 25

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!

Question 26

Cross tying for the managment of fractures

Answer 26

· 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

Question 27

Emergency fracture stabilisation

Answer 27

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

Question 28

Fractures during anaesthetic recovery

Answer 28

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!