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Tobias ECVS > Ch 60 - Fractures of the Femur > Flashcards

Ch 60 - Fractures of the Femur Flashcards

1
Q

Which bone is most commonly affected by osteomyelitis and nonunion?

A

Femur

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2
Q

Describe the AO fracture classification system

A

Each bone has a number (femur = 3)
Second number denoted relative position of the fracture within the bone
- 1 = proximal
- 2 = shaft
- 3 = distal

Described with respect to its morphology
- A = Single fracture
- B = Wedge or butterfly
- C = Complex

Final number corresponding to severity and prognosis
- 1 = good to excellent
- 2 = moderate severity, guarded to good prognosis
- 3 = severe, guarded to poor prognosis

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3
Q

What are the main forms of proximal intracapsular fractures?
Extracapsular?

A

Intracapsular
- epiphyseal
- physeal
- subcapital
- transcervical

Extracapsular
- basilar neck
- intertrochanteric
- subtrochanteric

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4
Q

Where is the highest strain density observed in the femoral neck?

A

Most medial and distal portion

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5
Q

What is the normal angle of inclination?

A

130 - 145 degrees

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6
Q

What is the normal angle of anteversion?

A

27 - 32 degrees

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7
Q

What muscles attach to the greater trochanter?

A

Middle and deep gluteal muscles
Piriformis muscles

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8
Q

Where is the lesser trochanter in relation to the femoral neck?
What muscle attached here?

A
  • Distal and caudomedial
  • Iliopsoas

Represents the distal limit of the metaphysis

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9
Q

Where is the third trochanter located in relation to the greater trochanter?
What muscles attach here?

A
  • distal
  • superficial gluteal muscle
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10
Q

What muscle attach at the intertrochanteric fossa?

A
  • Internal and external obturator
  • Gemelli
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11
Q

What are the three subdivision of the proximal blood supply?
What does each subdivision include?

A

Extraosseous
- lateral and medial circumflex femoral arteries
- caudal and cranial gluteal arteries
- iliolumbar artery
- Caudal gluteal and circumflex arteries anastomose to form vascular ring at base of femoral neck

Intracapsular
- Arise from vascular ring, penetrate joint capsule at distal attachment and course subsynovially along craniodistal femoral neck
- Anastomose near capital physis to form intracapsule vascular vascular ring
- Branches off ring penetrate the physis and give rist to intraosseous arcuate network

Intraosseous
- Branches of caudal gluteal and medial circumflex penetrate the floor of the trochanteric fossa and create intraosseous network

In dogs, the artery of the ligament of the head of the femur does NOT contribute to epiphyseal blood supply. This is in contrast to the cat

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12
Q

How much of the femoral longitudinal growth is from the femoral capital physis and the trochanteric physis?
At what age do they close?

A
  • Capital physis 25%
  • Trochanteric physis 0%
  • Closure in dogs begins at 6 months, complete 9-12m
  • Closure in cats 7-10m
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13
Q

What is the Gorman approach to the proximal femur?

A

Dorsal approach via osteotomy of the greater trochanter

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14
Q

List some unique biologic and mechanical features of proximal femoral fractures which can make it challenging

A
  • Concurrent trauma to fragile vascular network
  • Residual growth potential of capital physis
  • Eccentric loading of femoral head
  • limited bone stock for stabilisation
  • potential articular surface involvement
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15
Q

What approach should be considered for fractures of the capital epiphysis?

A

Ventral approach
- Avoids requirement to transect ligament of the head of the femur which can contribute to instability

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16
Q

How often is concurrent separation of the trochanteric physis seen with capital physeal fractures?

A

11 - 15%

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17
Q

What sized K-wires are appropriate for cats and most small-medium dogs?
How many should be placed?
In what orientation?

A
  • 0.7 - 1.6mm diameter
  • minimim of 2 pins, no more than three
  • Pin should be parallel to each other (allows forces to be distribulted equally, normal loading of growth plate and dynamic compression of the fracture

2 pins shown to be as strong as intach femoral neck in one study (weaker in another). Addition of a third pin increases strength by 29%

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18
Q

What structures can be used to guide epiphyseal femoral head pin placement?

A
  • Pins located within the center of the epiphysis can be safetly advanced a distance equal to 75-80% of the contralateral epiphysis or width of the pubic bone
  • Eccentrically placed should only be advanced to 65%
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19
Q

What percentage of dogs are reported to have a moderate to poor outcome after a FHO?

A

20%

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20
Q

What is capital physeal dysplasia?
What animals are overrepresented?

A

Spontaneous seperation of the capital physis in animals after timely physeal closure
- Young, overweight, castrated-males cats overrepresented

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21
Q

What fracture plane minimised shear stresses of femoral neck fractures?

A

30 degrees or less to the transverse place

22
Q

What are the repair options of fractures of the greater trochanter?
What are the potential results of premature trochanteric physeal closure?

A

Repair
- Conservative if minimally displaced
- Pins and tension band

Results of early physeal closure
- 5 deg increase in both inclination and anteversion

23
Q

What is essential in providing stability of the proximal fragment of a subtrochanteric fracture when using a bone plate?

A

Transcervical screw

24
Q

What is the reported rate of femoral neck resorption after open reduction and internal fixation?

A

Up to 70% within 3-6 weeks

Subsequent collapse is rare

25
Q

Why are pins for femoral neck/capital physeal fractures recommended to be removed?

A
  • Allows remodelling and more complete healing
  • Decreased interference with residual growth
  • Eases revision options if sevre OA develops
  • May help to reduce the risk of neck resorption
26
Q

In what region of the femoral diaphysis is the medullary cavity narrowist?

A

Proximal 1/3

27
Q

Most of the femoral diaphysis lacks muscular attachment except for the proximal and caudal surfaces. What muscles are attached?

A

Subtrochanteric region
- Vastus lateralis
- Vastus medialis
- Vastus intermedius
- Adductor longus

Caudal surface
- Adductor magnus et brevis (allow the narrow facies aspera / linea aspera)
- Pectineus and semimenbranosus on distal 1/3 caudomedially

28
Q

What vessel enters the principle nutrient foramen of the femur?

A

Branch of medial circumflex femoral artery

29
Q

What is the sole blood supply to bone fragments in comminuted or segmental fractures?

A

The periosteal arteries along the facies aspera

30
Q

What percentage of longitudinal growth is the distal physis responsible for?

A

75%

31
Q

List some factors which make femoral diaphyseal fracture repair challenging in young animals

A

Weak mechanical properties of immature bone
- thick periosteum
- thin cortex
- higher compliance
- lower cortiomedullary ratio

32
Q

What is the tension surface of the femur?

A

The lateral cortex

33
Q

How many cortices need to be engages with using a non-locking plate and a locking plate in combo with an IM pin?

A
  • Non-locking: minimum of 4 cortices per side
  • Locking: minimim of 4 cortices per side
34
Q

Why is an IM pin contraindicated in young, growing animals?

A

Can cause abnormal development of the proximal femur and subsequent hip dysplasia

35
Q

What are the reported success rates using a conventional interlocking nail for correction of diaphyseal femoral fractures?

A

83 - 96%

Likely higher with angle stable nails

36
Q

What is the reported rate of quadriceps contracture when using femoral ESF?

A

33% in dogs
7% in cats

37
Q

What are the proximal and distal anatomical landmarks for assessing rotational alignment of the femur during MIO?

A

Proximal: Intertrochanteric crest
Distal: Femoral trochlea

38
Q

When should a Targon nail not be used?

A

When the ratio of the between the diameters of the cortical drill hole and the diaphysis exceeds 56%

39
Q

What % shortening of the femur can dogs compensate for?

A

20%

40
Q

What is the reported rate of sciatic neuroproxia with retorgrade pinning?

A
  • 23% cats
  • 14% dogs
41
Q

What muscles and ligaments attach to the supracondylar region of the femur?

A
  • Medial and lateral heads of the gastrocnemius (origniate from caudally located supracondylar tuberosities)
  • Superficial digital flexor muscle (lateral supracondylar tuberosities)
  • Collateral ligaments (epicondyle)
  • Popliteus (lateral condyle)
  • Long digital extensor muscle (Between lateral epicondyle and lateral ridge of trochlear groove
42
Q

Why are chondrodystrophic dogs predisposed to supracondylar and condylar fractures?

A

The distal epiphysis is relatively elongated and caudally oriented creating greater bending moments

43
Q

What vessels supply blood to the distal femur?

A
  • Branches from saphenous and descending genicular artery (enter all sides of metaphysis)
  • Caudal genicular artery arborise to supply caudal joint capsule
  • Terminal medullar branches
44
Q

How is the distal physis shaped?
When does it close?

A
  • 4 pyramidal grooves which interdigitate with 4 similarly shaped epiphyseal pegs
  • Closure in dogs begins at 6m, complete 9-12m
  • Closure in cats begins 4m, completel 7-9m
45
Q

Where should the distal tip of an interlocking nail be advanced to?

A

Blumensaat’s line - represents proximal extent of the intercondylar notch

46
Q

What is the most commonly fractured physis in the dog?

A

Distal femoral physis

47
Q

What is the landmark and angle of pin insertion for a lateral distal femoral cross pin?
What angle would you use if Rush pinning?

A
  • Inserted just caudal and distal to the origin of long digital extensor muscle
  • 30 - 45 degree angle
  • Rush pinning: 15 - 20 degrees
48
Q

What is the reported rate of premature closure of a distal femoral physeal fracture?

A

83% (usually due to the inciting trauma)

49
Q

What forces tend to cause a condylar fracture?

A

Synergistic compressive and torsional forces applied to the stifle

50
Q

What are the main three options for fixation of bicondylar fractures?

A
  • Interfragmentary screws or k-wires alone
  • Interfragmentary screws and cross pins
  • Interfragmentary screws combined with a buttress plate

Tobias ECVS (110 decks)

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