Growth Plate and Pelvic Fractures

Growth plate fractures

fracture to the growth plate of developing animals; can interfere with normal bone development

Growth plate

aka physis; where cartilage is transformed into bone during development

A Growth plate is surrounded by what two bony landmarks?

epiphysis and metaphysis

What makes growth plates susceptible to injury?

because its cartilage is considerably weaker than the surrounding epiphyseal and metaphyseal bone

What is the process of a growth plate becoming a bone called?

endochondral ossification

Four components of a growth plate:

1.) outer fibrous layer

2.) cartilaginous component

3.) bony component

4.) vascular supply

outer fibrous layer of a growth plate

fibrous layer that surrounds the growth plate and provides support and protection

Two structures associated with the outer fibrous layer of a growth plate:

1.) Groove of Ranvier

2.) Ring of LaCroix

Groove of Ranvier

region of chondrocytes located around the periphery of the growth plate; contributes to cartilage growth at the physis

Ring of LaCroix

structure located between the groove of Ranvier and metaphysis; provides mechanical support to help stabilize and protect the growth plate

Cartilaginous component of the growth plate

where chondrocytes proliferate and eventually mineralize to be replaced by bone

The cartilaginous component has four zones:

1.) resting (reserve) zone

2.) proliferative zone

3.) hypertrophic zone

4.) mineralization zone

resting (reserve) zone

closest to epiphysis; contains small, immature chondrocytes that serve as a reservoir to contribute to continued bone growth

What is the clinical significance of the resting (reserve) zone?

damage to these cells can interfere with continued growth; fractures that spare this zone have a more favorable potential for continued bone growth than injuries that destroy it

proliferative zone

where chondrocytes begin actively dividing and organizing themselves into longitudinal columns

hypertrophic zone

chondrocytes become substantially larger as they mature

mineralization zone

hypertrophic chondrocytes eventually die, and the mineralized cartilage provides a scaffold for the deposition of new bone by osteoblasts

Which cartilage zone is the weakest? Why?

hypertrophic zone; as chondrocytes become larger, the supporting extracellular space decreases, making the area weaker and more susceptible to fracture

The growth plate has a relatively _________ vascular supply

limited

Which two cartilage zones do not have any blood vessels?

proliferative and hypertrophic zones

Two types of growth plates based on location:

1.) pressure growth plates

2.) traction growth plates

pressure growth plates

located at either end of long bones and are responsible for most of the bone's longitudinal growth

True or false: the contribution towards the growth of a long bone is even between a distal and proximal pressure growth plate

false!! (except rare occasions)

ex: humerus in dogs, the proximal physis contributes the majority of the growth, while the distal physis contributes only a small portion

Why is the the uneven contribution towards the growth of a long bone between pressure physes clinically important?

damage to a physis responsible for a large proportion of bone growth can produce more severe growth disturbances than damage to a physis that contributes relatively little

traction growth plates

occur at sites where muscles, tendons, or ligaments attach to bone; contribute to development of bony prominences

traction growth plates develop from _______ centers of ossification

secondary

Examples of traction growth plates

-tibial tuberosity

-olecranon

-greater trochanter

The age at which growth plates close varies according to...

species, breed, bone, and the specific physis involved.

Growth plates are relatively weak compared to the surrounding bone because...

because they consist primarily of cartilage and extracellular matrix (esp hypertrophic zone)

Therefore, a force that might not fracture mature bone can cause a fracture through an open growth plate

Growth plate injuries can occur due to _____ energy trauma or ______ energy trauma

high; low

high energy trauma

things that do substantial damage such as motor vehicle accidents, impalement injuries, and kicks from other animals

low energy trauma

injuries that occur after minor incidents, like falling from a low height, stepping off a step, or being stepped on

Salter-Harris Fracture Classification system

categorizes fractures according to which anatomical regions of the developing bone are involved

Six types of growth plate fractures according to the Salter-Harris Fracture Classification system:

1.) Salter-Harris Type I

2.) Salter-Harris Type II

3.) Salter-Harris Type III

4.) Salter-Harris Type IV

5.) Salter-Harris Type V

6.) Salter-Harris Type VI

Salter-Harris Type I fracture

fracture that passes directly through the growth plate without going into either the epiphysis or metaphysis

Salter-Harris Type I fractures commonly occur in what cartilaginous zone?

the hypertrophic zone

*but can occur at other levels within the physis

What is one benefit of a Salter-Harris Type I fracture?

Because the fracture often passes only through the hypertrophic zone, the resting or germinal zone remain intact, will will allow for continued longitudinal growth

Radiographic appearance of a Salter-Harris Type I fracture

May not be apparent on initial radiographs

-look for subtle changes like widening of physis

Common location of a Salter-Harris Type I fracture

Capital Femoral Physeal Fracture

Capital femoral physis

located at the femoral head

Salter-Harris Type II fracture

fracture across the physis and extending into the metaphysis

Salter-Harris Type II fractures are the most ___________ growth plate fractures in veterinary medicine

common!

Common location of a Salter-Harris Type II fracture

distal femoral physis

Salter-Harris Type III fracture

fracture across the physis which extends into the epiphysis (and therefore articular surface)

Why might a Salter-Harris Type III fracture be particularly concerning?

-they involve the resting or germinal zone of the physis, so damage to this zone may interfere with continued longitudinal growth

-additionally, can extend into the articular surface and could cause joint incongruity and osteoarthritis

Common locations of a Salter-Harris Type III fracture

condyles of long bones, particularly the femoral condyles and humeral condyles

Salter-Harris Type IV fracture

fracture through the metaphysis, physis and epiphysis (and therefore articular surface)

Why might a Salter-Harris Type IV fracture be particularly concerning?

same reasons as a type III

-they involve the resting or germinal zone of the physis, so damage to this zone may interfere with continued longitudinal growth

-additionally, can extend into the articular surface and could cause joint incongruity and osteoarthritis

Common location of a Salter-Harris Type IV fracture

distal humerus

What dog breed commonly experiences Salter-Harris Type IV fractures?

brachycephalic or toy breeds (Bulldogs, French Bulldogs, etc)

Salter-Harris Type V fracture

crush injury to physis that "erases" the growth plate

Why can a Salter-Harris Type V fracture be concerning?

Compression can destroy the resting or germinal zone; because these cells are responsible for supporting continued growth, damage may result in premature physeal closure and permanent growth disturbances

If the entire physis closes prematurely, longitudinal growth may stop.

If only one side closes, the unaffected side may continue growing, producing an angular deformity.

Common location of a Salter-Harris Type V fracture

distal ulna

What complication can occur from a Salter-Harris Type V fracture regarding the distal ulna?

Premature Closure of the Distal Ulnar Physis

Premature Closure of the Distal Ulnar Physis

most of the growth of the ulna comes from the distal ulnar physis, so damage and premature closure to this plate can limit it's ability to continue growing

While the ulna may stop growing normally from premature closure of the distal ulnar physis, the radius will...

continue growing normally

What might result when the ulna stops growing but the radius continues growing?

Instead of growing normally along its long axis, the radius becomes progressively curved

The ulna acts as a tether while the radius continues attempting to grow, producing a bowstring effect

Which two Salter-Harris Fractures are intra-articular?

Salter-Harris Type III and Salter-Harris Type IV (since they can both extend past the epiphysis and affect the joint)

Mnemonic to remember growth plate fracture classifications:

SALTER

S traight across (type I)

A bove (type II)

L ower (type III)

T two/through (type IV)

ER asure of growth plate (type V)

***A and L only work if looking at a distal physis; will need switched if looking at a proximal physis

Salter-Harris Type VI fracture

involve damage to the peripheral portion of the growth plate, including structures associated with the perichondrial ring (Groove of Ranvier)

Four complications of a growth plate injury:

1.) Growth arrest

2.) Valgus deformity

3.) Varus deformity

4.) Osteoarthritis

Growth arrest

Damage to the germinal zone may cause the physis to close before skeletal maturity, can resulting in a shortened bone

Valgus deformity

lateral deviation of the limb distal to deformity; occurs when only part of the physis is damaged

Varus deformity

medial deviation of the limb distal to deformity; occurs when only part of the physis is damaged

Osteoarthritis

occurs with fractures involving the joint surface (type III and IV)

Pelvic fractures

relatively common fractures that are typically associated with high energy trauma

An important concept in pelvic fracture evaluation is that the pelvis functions as a ______-like structure

box

How is the pelvis a box-like structure?

the components of the pelvis are interconnected, so displacement at one portion of the pelvis means there will likely be displacement at another location

Therefore, if a pelvic fracture is visibly displaced, there must usually be at least _______ sites of disruption

two

Exceptions to the Pelvic Box Principle

-in young animals, the pelvis is flexible, so injury can occur in one place without a second injury

-isolated acetabular stress fractures

There are often concurrent injuries associated with pelvic fractures. Why?

they generally result from high energy trauma, so the force responsible can also injure other body systems

In what region of the body will there be an especially high chance of concurrent injury associated with a pelvic fracture?

the thorax

*should always radiograph thorax in addition to pelvis

Examples of thoracic concurrent injuries with pelvic fractures:

-Pneumothorax

-Rib fractures

-Hemothorax

-Diaphragmatic hernia

Other common concurrent injuries associated with pelvic fractures:

-Urinary tract trauma --> ruptured bladder, ruptured urethra, bladder herniation

-GI tract trauma --> ruptured GI tract, spleen, liver

-Orthopedic trauma --> spinal fractures, long bond fractures

-Integument --> full thickness wounds

For patient evaluation of a pelvic fracture, what should be prioritized?

pelvic fractures are generally not life threatening, so instead should focus on treating shock or other life threatening injuries (such as pneumothorax, bladder rupture, etc)

Important landmarks to palpate during pelvic evaluation:

1.) palpate ilial wings

2.) assess stability of sacroiliac joint

3.) palpate greater trochanter and location within pelvis (acetabulum)

4.) palpate ischial tuberosities for asymmetry

When performing radiographs for a pelvic fracture, it is important to ALWAYS take _____ views

two

Lateral radiographs of a pelvic fracture are performed how?

with the affected side down

-down hip is flexed, while upper hip extended ("running man" position)

V/D radiographs of a pelvic fracture are performed how?

either "frog leg" where legs are spread apart, or have legs fully extended

An important consideration when determining whether a pelvic fracture requires surgery is...

whether the fracture involves the weight-bearing axis of the pelvis

weight-bearing axis of the pelvis involves three structures:

1.) acetabulum

2.) iliac body

3.) sacroiliac joint

Fractures of the pelvis usually will or will not heal well? Why?

will!

the pelvis is surrounded by a large muscle mass that:

-provide stability and support

-provide substantial blood flow to the pelvis

additionally, the ilium contains a large amount of cancellous bone, which is rich in blood supply

Seven injuries of the pelvic bones:

1.) Pelvic canal narrowing

2.) Sacroiliac Luxation

3.) Iliac Wing Fractures

4.) Iliac Body Fractures

5.) Acetabular Fractures

6.) Ischial Fractures

7.) Pubic Fractures

Pelvic canal narrowing

occurs when fracture fragments heal in an abnormal position, reducing the diameter of the pelvic canal

Conditions that can result due to pelvic canal narrowing

-constipation

-dystocia

-urethral obstruction

Sacroiliac Luxation

traumatic separation of the ilium from the sacrum at the sacroiliac joint

For a sacroiliac luxation, the ilium typically becomes displaced _______ to the sacrum

craniodorsally

Sacroiliac Luxations can be associated with concurrent _______ damage

nerve

Two nerves located near the sacroiliac joint

Sciatic nerve and lumbosacral nerve roots

Neurologic deficits associated with sacroiliac luxations:

-pelvic limb weakness

-sciatic nerve deficits

-reduced anal tone

-urinary dysfunction

What is found on physical examination of a sacroiliac luxation?

asymmetry/abnormal movement of the iliac wings

What is found on radiographs of a sacroiliac luxation?

V/D radiographs are useful!!

Normally, a smooth line can be followed along the medial aspect of one ilium, across the ventral aspect of the sacrum, and onto the opposite ilium.

With SI luxation, this smooth line is disrupted.

Iliac Wing Fractures

non weight bearing, non articular, and not associated with any nerves; therefore, typically usually managed conservatively rather than surgically

Iliac Body Fractures

major component of the weight bearing axis, and commonly long oblique fractures

What type of fracture is common with an Iliac body fracture?

oblique fracture with craniomedial displacement

Treatment of Iliac body fractures

Require surgical stabilization involving plate fixation

Iliac body fractures are associated with three other fractures:

1.) ischium

2.) publis

3.) acetabulum

Acetabular Fractures

major component of the pelvic weight-bearing axis AND involve an articular surface; will feel crepitation on palpation of the hip

Acetabular Fractures typically have a more _______ prognosis. Why?

gaurded; a fracture involving the acetabulum can disrupt the articular cartilage, so the femur no longer articulates smoothly with the acetabulum

Can produce degenerative joint disease and lameness!

Ischial Fractures

not part of the primary weight-bearing axis, so of less concern; may return to normal alignment without on their own when other pelvic fractures are surgically repaired