Fractures of the femur Flashcards
What is the main anatomic difference in the mediolateral shape of the canine as compared to feline femur?
The distal canine femur is curved caudally (retrocurvatum), whereas the feline femur is straight
What are the anatomic classifications of proximal femoral fractures?
What are the anatomic classifications of distal femoral fractures?
What is the point of attachment of the ligament of the head of the femur on the femoral head?
The fovea capitis
What anatomic structure helps to resist bending forces in the proximal femur?
The linea transversa. A bony ridge that runs from the neck to the greater trochanter.
What are normal angles of version and inclination of the proximal femur?
Inclination: 130-145 degrees
Anteversion: 27-32 degrees
What are the three protuberances of the proximal femur and their muscular attachments?
Greater trochanter: Middle/deep gluteals, piriformis.
Lesser trochanter: Ilipsoas (marks the distal limit of the metaphysis)
Third trochanter: Superficial gluteal.
The gemilli, internal and external obturator muscles attach in the trochanteric fossa.
What vessels contribute to the blood supply of the proximal femur?
Can be divided into three categories: extraosseous, intracapsular, intraosseous. Extraosseous vasculature predominantly arises from the lateral and medial circumflex femoral and cranial and caudal gluteal arteries. These form an extraosseous ring from which the intracapsular vessels arise. These traverse the capsule and form a second ring at the level of the neck from which the intraosseous vasculature arises.
Because all the arteries of the intracapsuslar and intraosseous networks propagate from the extraosseous vessels via a single extracapsular ring, the blood supply to the femoral head and neck remains susceptible to insult.
What is a major difference between the vascular supply to the proximal region of the femur in dogs and cats?
In cats the artery of the ligament of the head of the femur contributes to the epiphyseal blood supply
How much growth does the capital physis contribute to the overall length of the femur?
25%. The greater trochanteric physis does not contribute substantially to overall length.
What is the shape of the capital physis in the frontal plane?
L-shape
When do the proximal femoral physes close in dogs and cats?
Dogs: 9-12 months
Cats: 7-10 months
What approaches can be performed to access the proximal aspect of the femur?
- Craniolateral.
- Dorsal via trochanteric osteotomy.
- Dorsal via gluteal tenotomy.
- Ventral (completely avoids the epiphyseal blood supply but requires all implants be placed from the articular surface).
- Minimally invasive.
Why are repairs of the proximal region of the femur potentially challenging?
1) Concurrent trauma to the fragile vascular supply.
2) Residual growth potential of the capital physis.
3) Eccentric loading of the femoral head.
4) Limited bone stock for stabilization.
5) Potential articular surface involvement.
What are treatment options for fracture of the capital epiphysis?
Typically associated with an avulsion fracture of the ligament of the head of the femur.
Repaired using lag screws and/or k-wires. Should be countersunk beneath the articular surface. Use of lag screws has been associated with premature closure of the capital physis and femoral neck necrosis.
If there is coxofemoral instability following repair capsulorrhaphy, prosthetic joint capsule, or iliofemoral band should be considered.
Small fragments can also be removed. In cases of non-repairable damage FHO or THR could be considered.
What approach should be considered in the treatment of capital epiphysis fractures?
Ventral approach (transection of the ligament of the head of the femur is required for dorsal or craniolateral approaches)
What is the most common type of Salter Harris fracture to the proximal femoral physis?
Type 1. Concurrent separation of the trochanteric physis is seen in 11-15% of cases
At what age should osteotomy of the greater trochanter rather than gluteal tenotomy be performed for approach to the hip?
Greater than 3-5 months of age osteotomy is preferred
What are the surgical options for repair of a capital physeal fracture?
- Retrograde (better spacing of pins) or normograde (less invasive) pinning via a craniolateral approach. Lag screws also described but not recommended due to premature closure of the physis.
- Normograde pinning can also be performed from the joint surface using a ventral approach, but this inevitably results in articular cartilage damage.
- MIS techniques using fluoroscopy.
How many pins are recommended for repair of the capital physis?
Minimum of 2 pins, maximum of 3.
Additional pins do not increase the biomechanical stability of the repair and increases the likelihood of articular penetration, vascular compromise and iatrogenic fracture.
Should pins be placed parallel or divergent in repairs of the capital physis?
Parallel - allows ongoing growth potential and more even distribution between the pins as compared to divergent pin placement (making it a stronger construct).
Describe the ideal pin trajectory for repair of capital physeal fractures.
In the absence of fluoroscopy what pre-operative measurements can be used to ensure accurate epiphyseal pin placement in capital physeal fracture repair?
Width of the contralateral epiphysis or pubic bone (can be safely advanced a distance equal to 75-80% of these measurements if central, 65% if eccentric).
Alternatively they can be advanced through the articular surface, palpated and then retracted.
What percentage of patients have poor functional recovery following FHO?
20%. Other potential complications include altered weight bearing, disuse muscle atrophy, lameness after exercise, and ankylosis.
What is capital physeal dyplasia?
Spontaneous separation of the capital physis in animals after timely physeal closure.
What is the most likely signalment of a patient with capital physeal dysplasia?
Overweight, castrated male cats
What are the treatment options for cats with capital physeal dysplasia?
- Open repair using lag screw fixation and antirotational K-wire (because femoral growth is complete).
- MIS repair using K-wires.
- FHO
Are capital physeal or cervical fractures more common in juvenile cats?
Cervical (3 x as common).
Capital physeal fractures more common in dogs.
Which femoral neck fractures are intracapsular and which are extracapsular?
Intracapsular: subcapital, transcervical.
Extracapsular: Basilar
What femoral neck fracture angle is associated with less shearing forces?
Fracture angles less than 30 degrees to the transverse plane (correlates with less than 90 degrees to the femoral neck axis)
What treatment is recommended for cervical femoral fractures?
Surgical fixation with K-wires (recommended over the use of lag screws as these fractures are common in juvenile animals and the physis is typically still open).
Which screw is the most important when repairing subtrochanteric fractures with a bone plate?
The transcervical screw
What is the cause of apple coring following femoral neck fixation?
Suspected secondary to vascular disruption and stress protection. Often self limiting and subsequent collapse is rare.
May be minimized by the use of MIS fixation and removal of the pins after 3-6 weeks. Pin removal may also aid in remodelling and make subsequent surgical intervention easier if severe OA develops.
In a medium sized dog, how much growth is complete in the capital physis at 5 months of age?
80% (compared to 95% at 7 months).
Therefore repair of proximal fractures of the femur may be associated with greater development of dysplasia in patients less than 4-6 months of age.
What percentage of femoral growth originates from the proximal and distal femoral physes?
Why is the use of intramedullary pinning of the femur contraindicated in immature animals?
It may damage the vascular supply to the proximal femur resulting in growth deformities and subsequent hip dysplasia
What surgical technique is shown?
Stacked pinning of the femur. No longer recommended due to a high rate of complications (50%), including pin migration, loss of reduction, implant failure, sciatic neuropraxia or neurotmesis.
What is a disadvantage of the Targon interlocking nail system for use in repair of femoral diaphyseal fractures?
The large size of the threaded bolts required for the system may compromise the structural integrity of the diaphysis.
During minimally invasive repair of the femur what structure can be used to ensure appropriate version of the femoral head?
Arciform crest (or intertrochanteric crest). Extends from the distal most extent of the greater trochanter to the lesser trochanter and marks the caudal edge of the femur.
The trochlea can be used distally.
Why are chondrodystrophic breeds potentially predisposed to supracondylar fractures of the femur?
Why is lag screw fixation from proximal to distal sometimes possible in supracondylar fractures of the femur in chondrodystrophic dogs?
Due to the marked angulation present in the distal femur.
What is the most common type of Salter Harris fracture of the distal femur?
Salter Harris type 2 in dogs, type 1 in cats (the caudal metaphyseal pegs are more prominent in dogs and are thus more deeply seated in the epiphysis which might predispose to type 2 rather than type 1 fractures)
What is Blumensaat’s line?
The radiographic line in the distal femur that delineates the proximal extent of the intercondylar notch.
Can be used to demarcate the distal extent of interlocking nail insertion during repair of supracondylar fractures.
According to Thompson 2020 in Vet Surg, which of the following tension band configurations had the greatest strength in a greater trochanteric osteotomy model?
1) Figure of eight with one twist
2) Figure of eight with two twists
3) Dual interlocking single loop
4) Double loop
Double loop (resisted 2 - 2.4 times greater load before failure).
In a study by De Vreught 2024 in JSAP, what was associated with an increased risk of failure for cats undergoing pinning of transcervical fractures?
A higher osteolysis score (all catastrophic complications occured in fractures with an osteolysis grade of 2 or 3).
