Fractures of the humerus

Question 1

What structures pass through the supracondylar foramen in the cat?

Answer 1

The median nerve and a branch of the brachial artery. The supracondylar foramen is located proximal to the medial epicondyle.

Question 2

What are the most common locations for humeral fractures in the dog and cat?

Answer 2

Question 3

What neurologic signs might suggest concurrent brachial plexus injury in a patient with a humeral fracture?

Answer 3

Horner’s syndrome, ipsilateral loss of cutaneous trunci reflex, neurologic deficits in the thoracic limb.

Question 4

What is the significance of the tricipital line of the humerus in fracture repair?

Answer 4

The tricipital line is the attachment of the lateral head of the triceps. The bone proximal and cranial to this line is relatively thin, caudally the bone is thicker and has greater implant holding power.

Question 5

What are the names of the medial and lateral humeral condyles?

Answer 5

Medial: trochlea (articulates with the trochlear notch of the ulna).
Lateral: capitulum (smaller, articulates with the radial head).

Question 6

What structure holds the biceps brachii muscle in the intertubercular groove of the humerus?

Answer 6

The transverse humeral retinaculum

Question 7

What major nerves are encountered in surgical approaches to the humerus?

Answer 7

Radial nerve laterally, median and ulnar nerves medially

Question 8

Which part of the humerus are most commonly fracture in the dog and cat?

Answer 8

Dog: distal
Cat: mid-diaphysis

Question 9

At what ages does the proximal humeral physis fuse in the dog and cat?

Answer 9

Dog: 7.5 - 12 months
Cat: 19 - 26 months

Question 10

What are repair options for Salter Harris type 1 or 2 fractures of the proximal humeral physis?

Answer 10

Parallel K-wires (preferred in juvenile animals with growth potential), lag screws, pins and TBW.

The physis is usually fused by 12 months in dogs and 26 months in cats.

Question 11

In instances when the greater tubercle of the humerus is fractured separately from the proximal humeral physis, what are the repair options?

Answer 11

Pin and TBW (due to pull of supraspinatous muscle). If concurrent fracture of the proximal humeral physis this can be repaired using a lag screw and anti-rotational K-wire.

Question 12

What are fractures called that enter the supratrochlear foramen?

Answer 12

Supracondylar fractures

Question 13

Into which humeral condyle should IM pins ideally be inserted for humeral fracture repair?

Answer 13

Trochlea (to increase bone purchase and length of the pins). Optimal pin diameter is 36-45% of the craniocaudal medullary canal diameter at the distal 80th percentile of the humeral length. This ensures passage through the medial epicondylar crest.

Question 14

Is the medial epicondylar crest wide enough to allow for pin passage in humeral fracture repair of the cat?

Answer 14

Typically not. Should be seated in the diaphysis just proximal to the olecranon fossa.

Question 15

What percentage of humeral pins passed in a nondirected retrograde fashion result in penetration of the shoulder joint?

Answer 15

20%

Question 16

What is the landmark for normograde IM pin insertion in the humerus?

Answer 16

Craniolateral aspect of the greater tubercle.

Question 17

Why is distal retrograde IM pin passage not recommended for fractures of the distal humerus?

Answer 17

Potential for damage to the periarticular soft tissues and articular cartilage, as well as ulnar nerve entrapment.

Question 18

In what direction is an IM pin aimed during proximal retrograde placement in the humerus?

Answer 18

Craniolateral.

Question 19

What type of ESF are appropriate for use in a humeral fracture?

Answer 19

Type I, modified type I-II, combined ESF intramedullary pin (can be tied-in).

Question 20

Describe the anatomic landmarks for placement of a transcondylar pin during ESF repair of a distal humeral fracture

Answer 20

Dogs: Craniodistal to the lateral and medial epicondyles.
Cats: Cranial to the lateral and medial epicondyles.

Question 21

What are the tension sides of the humerus?

Answer 21

Proximal: Craniolateral
Distal: Caudomedial

Therefore plates are often placed cranially or laterally for fractures of the proximal and middle humerus, and placed medially for distal diaphyseal, supracondylar, and intracondylar fractures.

Question 22

What are the benefits and disadvantages of medial humeral plating?

Answer 22

Advantages: less soft tissue coverage distally (easier approach), straighter shape of the medial epicondylar crest requires less contouring, can access the supracondylar foramen in cats to ensure retraction of the median nerve and brachial artery.

Disadvantages: inadequate access to proximal shaft due to muscular attachments.

Question 23

What are repair options for fractures of the supracondylar region of the humerus?

Answer 23

Cross-pinning (in young animals, retrograde pin placement not ideal due to articular damage), plates (uni or bilateral), type I ESF with at least 2 distal transfixation pins and IM pin, modified type I-II ESF with transcondylar pin distally.

Question 24

What is the benefit of placing a plate on the caudomedial surface of the medial epicondylar crest?

Answer 24

Screws are angled away from the olecranon fossa.

May need to place the plate medially, however, if the fracture is comminuted requiring extension of the repair up the humeral shaft.

Question 25

At what age do the two separate (lateral and medial) humeral epiphysis centers of ossification fuse?

Answer 25

3 months of age (attach to the metaphysis at 5.5 - 6 months)

Question 26

Which humeral condyle is fractured more commonly?

Answer 26

Lateral (34-67%).

Intracondylar is in 26-35% of cases, and medial 7-11%.

Question 27

What is the breed at greatest risk of humeral condylar fracture?

Answer 27

French bulldog

Question 28

Why are humeral condylar fractures uncommon in cats?

Answer 28

Wider and stronger lateral and medial epicondyles, absent olecranon fossa.

Question 29

What are surgical repair options for humeral condylar fractures?

Answer 29

Transcondylar screw + antirotational pin, screw, or bone plate.

Question 30

What percentage of growth is the distal humeral growth plate responsible for?

Answer 30

20%. This likely explains the absence of humeral shortening following humeral condylar fracture repair, even when implants cross the growth plate.

Question 31

What are the two different approaches for transcondylar screw placement following humeral condylar fracture?

Answer 31

Out to in: less soft tissue dissection, but blind placement and less exposure, need to estimate length of glide hole, accidental intra-articular placement is possible.

In to out: more dissection, difficult to place screw at appropriate transcondylar angle (tendency for exit point on the lateral cortex to be too distal).

Question 32

How is reduction assessed during humeral condylar fracture repair?

Answer 32

Either via alignment of the epicondylar crest fragments, or direct visualization of the articular surface using a craniolateral approach to the condyle.

Question 33

True or false? Fractures of the lateral humeral condyle stabilized with a transcondylar screw and supracondylar K-wire are more likely to have major complications than stabilization with a transcondylar screw and supracondylar screw or lateral epicondylar plate.

Answer 33

True

Question 34

What was associated with an increased risk of fixation failure following humeral condylar fracture repair?

Answer 34

Presence of an intracondylar fracture gap. Interestingly accuracy of fracture reduction is not associated with outcome.

Question 35

Which breed is most commonly affected by ununited medial epicondyle?

Answer 35

Labrador retrievers. Should be reattached with a bone screw or pin and TBW

Question 36

What are options for improved exposure to the elbow joint for intracondylar T-Y fractures?

Answer 36

Olecranon osteotomy (37% complication rate), tenotomy of the triceps brachii tendon (may be preferred in juvenile dogs to avoid damage to the ulna growth plate), combined lateral and medial approaches.

Question 37

How are T-Y fractures typically repaired?

Answer 37

Transcondylar lag screw and bilateral plates (order of placement depends on approach; typically the medial epicondylar crest is repaired initially).

If the fracture is comminuted the fragments should ideally be reconstructed with a combination of screw, cerclage or K-wires to reduce the multifragment fracture to 3-pieces.

Question 38

What is incomplete ossification of the humeral condyle?

Answer 38

Failure of the lateral and medial humeral condyles to fuse (centers of ossification should be fused by 3 months)

Question 39

Which breed is predisposed to IOHC?

Answer 39

Spaniel breeds. Typically middle aged, male dogs.

Question 40

Is IOHC typically unilateral or bilateral?

Answer 40

Bilateral

Question 41

How frequently is a FCP of the elbow diagnosed in conjunction with IOHC?

Answer 41

25% of cases

Question 42

What additional radiographic view is required for diagnosis of IOHC?

Answer 42

15 degree craniomedial to caudolateral oblique projection

Question 43

Describe the 3 different possible presenting complaints for a dog with IOHC

Answer 43

Question 44

What diagnostics could be considered for work-up of a suspected case of IOHC?

Answer 44

Radiography, scintigraphy (not specific), CT (partial or complete fissure), arthroscopic evaluation

Question 45

What percentage of dogs managed medically for IOHC resulted in fracture?

Answer 45

Partial radiolucent line: 43%
Complete radiolucent line: 8%

Surgical intervention generally preferred.

Question 46

What size transcondylar screw is recommended for treatment of IOHC?

Answer 46

4.5mm (for standard size adult Spaniels).

Can be combined with transcondylar tunnels +/- autogenous bone grafting to promote vascular ingrowth.

Question 47

Does medial-to-lateral or lateral-to-medial drilling have a greater risk of inadvertently penetrating the joint in surgical repair of IOHC?

Answer 47

Medial to lateral

Question 48

According to Villamil 2020 in Vet Surg, how much more likely were French Bulldogs as compared to other breeds to suffer from a medial humeral condylar fracture? Was epicondylar plating or lag screws and K-wires associated with a reduced rate of complications?

Answer 48

6.58 times as likely.

Epicondylar plate fixation of humeral condylar fractures associated with a lower rate of complications.

Question 49

In patients with humeral intercondylar fissure what were two lesions identified by Danielski 2021 in Vet Surg on elbow arthroscopy that were not present in dogs without fissuring?

Answer 49

Focal cartilage lesion on the caudal aspect of the humeral condyle, humeroanconeal incongruity.

Question 50

In a study by Anderson 2023 in Vet Surg, how frequently was a humeral intercondylar fissure identified in the contralateral elbow of French Bulldogs presenting for humeral condylar fracture? How much more likely was repair with a transcondylar screw and K-wire to have complications as compared to other methods?

Compare to studies by Mella 2022 in VCOT, Franklin 2022 in VRU, and Davenport 2023 in VRU.

Answer 50

58% of French bulldogs had a fissure of the contralateral elbow.
Patients repaired with a transcondylar screw and K-wire were 7.6 times as likely to have a complication as compared to other methods of repair.

Interestingly in a study by Mella 2022 in VCOT, there were no intracondylar fissures identified in a population of non-lame French bulldog elbows (although 1/3 had intracondylar sclerosis).

In another study by Franklin 2022 in VRU, the prevalence of humeral intercondylar fissures in French bulldogs (12%) and pugs (11%) were not different from the general population (5%).

In a study by Davenport 2023 in VRU, 44% of French bulldogs presenting for humeral condylar fracture had intracondylar fissures of the contralateral elbow (compared to 58% of spaniels). Additional MCP pathology (29%), elbow incongruency (4%) and periarticular osteophytes (20%) were observed in spaniels but not french bulldogs.

Question 51

In a study by Carwardine 2024 in Vet Surg, was the complication rate with transcondylar screw placement for canine intracondylar fissures higher for screws placed medial-to-lateral or lateral-to-medial? What other factor was a risk for major complications?

Answer 51

Lateral-to-medial (62% complication rate as compared to 19%). Majority of complications were seromas and SSIs.

A lower area moment of inertia normalized to body weight was associated with increased risk of major complications.

Compare to Potamopoulou 2023 in VCOT who found no difference in SSI between laterally or medially placed screws.

Question 52

In a study by Danielski 2024 in Vet Surg, what was the rate of healing of humeral intracondylar fissures following proximal ulna osteotomy? Major complications due to lack of healing of the fissure was observed in what percentage of cases?

Answer 52

80% healed, major complication rate of 8%.

Question 53

In a study by Pierrot 2024 in JAVMA, what percentage of dogs with humeral condylar fractures also had suspected fracture of the medial coronoid process on radiographs?

Answer 53

50%. Comminution of the humeral condylar fracture was associated with an increased likelihood.

Question 54

What system was designed by Walton 2020 in JSAP for treatment of humeral intracondylar fissures?

Answer 54

The humeral intracondylar repair system

Question 55

What are the two most common surgical approaches for repair of Y-T humeral condylar fractures?

Answer 55

Osteotomy of the olecranon, or combined medial and lateral approaches.

Question 56

In a study by Castaldo 2021 in VCOT which of the following constructs was stronger for stabilization of a canine cadaveric supracondylar fracture in a gap model?
1) Double plating
2) Intramedullary pin tie-in

Answer 56

Double plating was stronger, although no differences in stiffness were observed between constructs.

Question 57

In a study by Eayrs 2021 in VCOT, what was the perioperative outcome in skeletally mature dogs treated for fracture of the lateral humeral condyle?

Answer 57

10% (all fractures treated with transcondylar screw and epicondylar plate).

A large proportion of dogs had a persistent intracondylar fracture line post-operative (20/26), but this didn’t seem to affect clinical function. The majority of dogs were spaniels.

Question 58

In a study by Schettler 2022 in VCOT, how much more likely were French bulldogs to suffer a humeral condylar fracture as compared to the general population?

Answer 58

49 times as likely.

Question 59

In a study by Fuchter 2023 in VCOT, did insertion of a positional or lag screw in a humeral condylar fracture model result in greater force and area of compression?

Answer 59

Insertion of a lag screw resulted in greater force and area of compression.

Question 60

In a study by Condon 2024 in VCOT, what was the most common humeral condylar fracture configuration in the French bulldog? What was the overall complication rate post-operatively? Was surgical fixation technique associated with the rate of complications?

Answer 60

The lateral humeral condyle was fractured in 2/3 of cases. Fractures were more likely to occur in skeletally immature cases, and a fall was the most common inciting cause.

The complication rate was 22%, of which 33% were major. These included seroma formation, implant migration/irritation, lameness, SSI, radial neuropraxia (implant migration and seroma were most common).

Surgical fixation technique was not correlated with complication rate, however, comminution was.

Question 61

According to Nickel 2022 in VRU, is periosteal reaction of the cranial aspect of the humerus an incidental finding in some dogs? Which dogs are predisposed?

Answer 61

Yes - thought to be associated with the enthesis of the superficial pectoral muscles.

German shepherds and Rottweilers are predisposed. More likely in large breed older dogs.

Question 62

In a study by Simpson 2022 in JFMS, was there a greater angle tolerance for transcondylar screws drilled lateral-to-medial or medial-to-lateral in cats?

Answer 62

Lateral-to-medial.
The lateral entry point is craniodistal to the lateral epicondyle and the medial exit point is craniodistal to the medial epicondyle. Both are around 0.3 x the humeral condylar diameter cranial, and 0.16 x distal.