Complications of fracture healing - delayed union, mal-union, non-union

Question 1

What is a delayed union?

Answer 1

Delayed union is a fracture that has not healed in the normally expected time for that particular type of fracture to heal

Influencing factors: age, breed, species, site, soft tissue, method of fixation

Question 2

What is a non-union?

Answer 2

A non-union is a fracture that stops healning and union will not occur without surgical intervention.

In hu: 3-6 months

Question 3

What are symptoms of delayed/non-union?

Answer 3

• painful motion at fracture site
• pseudoarthrosis
• progressive deformity
• muscle atrophy
• joint stiffness

Question 4

Causes of delayed union and non-union?

Answer 4

BIG RIB

Blood supply impairment
Immobilisation inadequate
General factors
Reduction inadequate
Infection
Bone loss

Question 5

“Average “ time to clinical union?

Answer 5

Question 6

What is the most common cause for delayed or non-union?

Answer 6

Inadequate immobilisation

Question 7

Radiological apperance of delayed union?

Answer 7

• Radiolucent gap between the fracture fragments
• with a feathery or chewed up appearance of the fracture ends
• a moderate callus

Question 8

Radiological appearance of non-union?

Answer 8

• radiolucent gap between the fracture fragments
• no radiological evidence of healing
• no callus
• ends of bone segments are rounded
• marrow cavity sealed with dense, sclerotic bone
• stress radiography can be used to show movement in fracture site

Question 9

Which type of non-union is most common?

Answer 9

Hypertrophic type

Question 9

What groups and subgroups can non-unions be classified into?

Answer 9

Question 10

Properties of hypertrophic non-union?

Answer 10

• usually secondary to IM pinning upper limb bone fractures
• caused by rotation, loose cerklage or sequestrae
• elephant food shaped callus which does not bridge gap

Treatment: Rigid stabilisation, preferrably compression
If debridement is necessary - cut new surface and compress

Question 11

What causes slightly hypertrophic nonunion?

Answer 11

Instability following plate fixation

Question 12

What causes an oligotrophic nonunion?

Answer 12

Fragments are usually widely separated
e.g. avulsion fracture

Question 13

What causes dystrophic nonunion?

Answer 13

Biologically inactive
Caused by complications of comminuted fractures, poorly vascularized fragment(s) impede fracture healing

Question 14

What causes necrotic nonunion?

Answer 14

biologically inactive
- seen as a complication of comminuted fractures where a non-viable fragment or sequestra impedes healing

Question 15

What causes defect type of non union?

Answer 15

A major defect in bone caused by removal of fragments or sequestrae, the gap is too big to be bridged by the normal healing process
Often seen after severe soft tissue injury or a loss of vascularity in the area

Question 16

What causes the atrophic type?

Answer 16

Most common of biologically inactive
most difficult to deal with
- complication of radius and ulna fractures in small and toy breeds
- instability at fracture site with loss of osteogenic activity leads to osteoporosis and eventually osteolysis
- shearing forces thought to predispose (rotation of antebrachium)

Tx: plate fixation and bone graft or ESF

Question 17

how many % can we reduce a long bone length without clinical signs?

Answer 17

20%

Question 18

Which implants can be used in non-unions?

Answer 18

Titanium - less stiff = less stress protection

Question 19

General treatment principles for delayed or non-union?

Answer 19

1) ensure no major nerve damage or fracture disease - decide if salveagable or not
2) primary goal in tx vascularized non-unions is to provide fixation
3) primary goal in tx avascularized non-unions is to stimulate osteogenesis -> expose, freshen up ends (maybe cut back 1-2mm) -> stabilize with a plate and bone graft
4) when infection is present if the implants are stable then these should be left in place until the fracture has healed

Question 20

Definition of malunion?

Answer 20

A fracture that has healed or is healing in an abnormal position, caused by improper immobilisation or reduction during healing

Question 21

Malunion can be divided into?

Answer 21

• overriding
• angular
• rotational
• intra-articular
• combination of above

Question 22

Malunion can be classified as?

Answer 22

Funcitonal
non-funcitonal

Question 23

What can be the consequences of malunion?

Answer 23

Axial, rotational -> predispose to DJD
External rotation not as bad as internal rotation
Craniocaudal malunion usually dont cause any problems
External rotation of femur -> patellar luxation

Question 24

Treatment of malunion, when?

Answer 24

Corrective osteotomy, as treated as possible