Chapter 97 - Humerus

Question 1

What forms the intertubercular groove in the equine humerus?

Answer 1

The greater, intermediate, and lesser tubercles.

Question 2

Answer 2

Ultrasound from left to righ you see the lateral aspect of humerus observe a little bit of fluid, biccipital bursa and great trochanter
In the middle you see intermedial tubercle and lat and medial lobes of bicipital bursa
Finally on right you see medial lobe and has a lot of muscle tissue in this are

Question 3

Answer 3

From left to right we go from distal to proximal zone of the bone we see bicipital tendon a bit less defined in the first left image (2transverse image and 1 longitudinal) in the second image the supraglenoid tuberosity and the tendon is smaller because originates here and the third image is 90º image (longitudinal) where we see the tendon going to the supraglenoid

Question 4

Which muscle is responsible for shoulder flexion and forelimb abduction and originates from the deltoid tuberosity?

Answer 4

Deltoid muscle.

Question 5

What is the primary function of the radial nerve in the equine forelimb?

Answer 5

Extension of the elbow.

Question 6

What clinical signs are observed when the radial nerve is injured proximal to the triceps branches in horses?

Answer 6

Inability to bear weight on the limb and hold the carpus and digit in the flexed position.

Question 7

Which nerves supply the flexors of the upper and lower limb in horses?

Answer 7

The musculocutaneous, median, and ulnar nerves.

Question 8

What is the primary role of the axillary artery and vein in the equine forelimb?

Answer 8

Give rise to the brachial artery and vein.

Question 9

What is the primary role of the cephalic vein in the equine forelimb?

Answer 9

Continue distad in the groove between the brachiocephalicus and descending pectoral muscles.

Question 10

What structures form the cubital joint in the equine forelimb?

Answer 10

The humeral condyle and the olecranon fossa.

Question 11

What provides lateral stability to the equine shoulder joint?

Answer 11

Supraspinatus and infraspinatus muscles.

Question 12

Which muscle serves as an adductor of the equine forelimb and inserts on the deltoid tuberosity?

Answer 12

Superficial pectoral muscle.

Question 13

What is the primary etiology of greater tubercle fractures in horses?

Answer 13

Traumatic episodes, such as kick injuries or falls.

Question 14

Which part of the humerus is identified as the palpable “point of the shoulder”?

Answer 14

The cranial part of the greater tubercle.

Question 15

What is a consistent finding on physical exams for horses with greater tubercle fractures?

Answer 15

Swelling and crepitation

Question 16

How is the diagnosis of greater tubercle fractures verified?

Answer 16

Via radiography - fractures of GT better with Caudolateral-craniomedial oblique view.

Question 17

Which patients with greater tubercle fractures may be managed with stall rest without surgical intervention?

Answer 17

Those with no to minimal displacement and adequate comfort will have stall rest of minimum 6 motnhs

Question 18

Answer 18

Delta tuberosity in the central image you see transverse image the bone is only 1 cm from skin

Question 19

What is recommended during the initial weeks of stall rest to reduce the risk of fragment displacement in horses with greater tubercle fractures?

Answer 19

Encouraging recumbency.

Question 20

What should be performed prior to transitioning horses to small paddock turnout during nonsurgical treatment of greater tubercle fractures?

Answer 20

Radiographic examination to confirm progressive healing. If no healing this horses becoms uncomfortable surgery because of fragment displacement should be performed.

2/5 managed conservatively went back to sport

Question 21

Why should patients with discomfort levels not allowing shared weight bearing between the affected and unaffected limbs be considered surgical candidates?

Answer 21

To reduce the risk of fragment displacement.

Question 22

Answer 22

Figure 97-1. (A) Caudolateral-craniomedial oblique radiographic image of a minimally displaced greater tubercle fracture in an 18-year-old Arabian stallion that became acutely grade 4/5 right front lame after a fall. (B) Cranioproximal-craniodistal oblique radiographic image demonstrating the extension of the fracture line into the intertubercular groove.

Question 23

Answer 23

Caudolateral-craniomedial radiographic view of the horse in Figure 97-1, 4 days later, demonstrating displacement secondary to distraction by the tendinous insertions of the infraspinatus and supraspinatus muscles.

Question 24

What are the surgical treatment options for great tubercle humeral fractures?

Answer 24

1. fragment removal
2. open reduction
3. internal fixation (ORIF)
4. minimally invasive internal fixation

Question 25

What are the surgical treatment options for humeral fractures?

Answer 25

Open reduction and internal fixation (ORIF) or minimally invasive internal fixation

Question 26

When is fragment removal considered as a surgical option for humeral fractures?

Answer 26

Only for small fracture fragments not intertubercular groove

Question 27

How is ORIF typically performed for humeral fractures?

Answer 27

In a recumbent patient under general anesthesia

Question 28

How is the fracture fragment stabilized during ORIF?

Answer 28

With at least three 5.5-mm cortex screws in lag fashion through washers

Question 29

Answer 29

Postoperative cranioproximal-craniodistal oblique radiograph of the horse in Figures 97-1 and 97-2. Three 5.5-mm cortex screws with washers were placed in lag fashion by a minimally invasive approach, using standing sedation and local anesthesia.

Question 30

Why is assisted recovery recommended after surgery for humeral fractures?

Answer 30

To reduce the risk of fragment displacement

Question 31

When is surgical treatment essential for humeral fractures?

Answer 31

Only in cases with displaced and unstable fragments

Question 32

Describe the incision and landmarks for the approach

Answer 32

The fracture is approached through a **lateral curvilinear incision **centered over the scapulohumeral joint and extending distally to the level of the deltoid tuberosity.

Dissection is continued between the **brachiocephalicus **and deltoideus muscle to expose the greater tubercle.

The biceps brachii muscle may be reflected medially to expose the fracture line within the** intertubercular groove.**

Reduction of the proximally displaced fracture fragment may be facilitated through distal traction on the 4.0-mm drill guide inserted into the glide hole prepared across the fragment. Following reduction, the fracture fragment is stabilized with at **least three 5.5-mm cortex screws placed in lag fashion** through washers**

Question 33

In some cases, despite successful surgical treatment, what may remain radiographically evident for months postoperatively?

Answer 33

The fracture line

Question 34

Answer 34

Figure 97-4. Caudolateral-craniomedial oblique radiographic image of an 11-year-old Thoroughbred mare presenting for evaluation of a chronic, nonhealing, traumatic injury to the brachial region. A bone sequestrum is present on the deltoid tuberosity.

Question 35

What is the ideal radiograph for diagnosis?

Answer 35

cranio45ºmedial caudolateral oblique

Question 36

Answer 36

Figure 97-5. (A) Mediolateral radiographic image of the shoulder region demonstrating significant caudoproximal periosteal reaction in a horse affected by a humeral stress fracture in that location. (B) CT scout (left) and sagittal slice (right) at the level of the caudoproximal neck of an isolated humerus (postmortem) in a horse affected by a humeral stress fracture. Note the smooth, periosteal reaction in the region of cortical bone disruption.

Question 37

Answer 37

Figure 97-7. Left and right humeri of a horse bilaterally affected by caudoproximal humeral stress fractures. The left humeral stress fracture has progressed to a complete, displaced humeral fracture resulting in euthanasia. (

Question 38

Answer 38

Question 39

What is the best radiographic view for deltoid tubercle ?

Answer 39

45º craniomedial-caudolateral oblique projection

Question 40

Deltoid tuberosity fractures in horses are considered:

Answer 40

Rare

Question 41

Answer 41

Question 42

What is a common clinical sign associated with deltoid tuberosity fractures in horses?

Answer 42

Lameness with reduced protraction of the affected limb

Question 43

What might hinder the evaluation of deltoid tuberosity fractures using ultrasonography?

Answer 43

Gas accumulation within the soft tissues

Question 44

What is the recommended treatment for associated wounds in deltoid tuberosity fractures?

Answer 44

Appropriate wound management

Question 45

Which of the following is NOT a recommended step in wound management for deltoid tuberosity fractures?

Answer 45

Fragment removal

Question 46

How long should horses with deltoid tuberosity fractures be confined to a stall during initial treatment?

Answer 46

6-12 weeks

Question 47

What type of medication may be administered during the initial weeks of stall confinement for deltoid tuberosity fractures?

Answer 47

Nonsteroidal anti-inflammatory drugs (NSAIDs)

Question 48

What complications are horses at risk of if they cannot bear weight on the affected limb during stall confinement?

Answer 48

Laminitis

Question 49

What is the prognosis for horses with deltoid tuberosity fractures treated with local wound care and stall rest?

Answer 49

Excellent

Question 50

How many horses in a case series with deltoid tuberosity fractures returned to athletic function without lameness after treatment?

Answer 50

13 out of 14

Question 51

What is the recommended course of treatment for deltoid tuberosity fractures associated with a fracture of the greater tubercle?

Answer 51

Surgery, same approach as discussed before for GT

Question 52

In cases where the deltoid tuberosity is fractured alone, what is the recommended treatment?

Answer 52

Wound care and stall rest

Question 53

What complication was experienced by one horse in the case series with deltoid tuberosity fractures who did not return to athletic function?

Answer 53

Bone sequestration

Question 54

What is the success rate of surgical intervention in horses with deltoid tuberosity fractures?

Answer 54

Good

Question 55

What is the primary factor influencing the prognosis for horses with deltoid tuberosity fractures? a) Age of the horse
b) Breed of the horse
c) Type of fracture
d) Timeliness of treatment

Answer 55

c) Type of fracture

Question 56

What is the main cause of stress remodeling in the humerus of racehorses?

Answer 56

Intense exercise

Question 57

Which locations in the humerus are susceptible to stress-related injury in racing and training horses?

Answer 57

Caudoproximal, cranioproximal, caudodistal, and craniodistal cortex

Question 58

What is a consequence of intense exercise in horses regarding humeral stress remodeling?

Answer 58

Stress fractures

Question 59

In one case series, when were Thoroughbred racehorses at greater risk of complete humeral fracture?
a) After a 1-month rest period
b) After an increase in exercise following a 2-month or longer rest period
c) After a winter break
d) After a decrease in exercise

Answer 59

b) After an increase in exercise following a 2-month or longer rest period

Question 60

What is the typical timing of complete humeral fractures in Thoroughbred racehorses after returning to race training?
a) Within 6 months
b) Within 1 year
c) Within 10 days
d) Within 30 days

Answer 60

c) Within 10 days

Question 61

How does intense exercise contribute to the risk of complete humeral fractures in horses?

Answer 61

It temporarily weakens the bone during the healing process.

Question 62

What is the primary clinical sign of humeral stress fractures in horses?

Answer 62

Lameness - Stress fractures result in acute, moderate to severe lameness that may be exacerbated by manipulation of the upper limb. Clinical signs improve quickly with rest

Question 63

In contrast to tibial stress fractures, which horses are more likely to experience humeral stress fractures?

Answer 63

Horses with more extensive race histories in 3 years old vs tibia that is younger (>2yo) and without any or few race records

Question 64

What was the most commonly fractured bone among 129 instances of proximal limb and pelvic fractures in Hong Kong racehorses?

Answer 64

Humerus

Question 65

What percentage of horses with proximal limb and pelvic fractures in Hong Kong returned to racing?
a) 40%
b) 60%
c) 71.2%
d) 90%

Answer 65

c) 71.2%

Question 66

What is the diagnostic modality of choice when localizing clinical signs are present for humeral stress fractures?
a) Nuclear scintigraphy
b) Ultrasonography
c) Computed tomography (CT)
d) Radiography

Answer 66

d) Radiography

Question 67

What radiographic findings suggest a humeral stress fracture?

Answer 67

c) Periosteal bone formation and medullary sclerosis

Question 68

For humeral stress fractures there is sex, limb or seasonal predisposition?

Answer 68

No there is no prediposition

Question 69

Which zone of the bone is associated with more severe and complete fractures of the humerus?

Answer 69

Caudoproximal humeral stress remodeling lesions are **more severe **and are associated with most of the complete fractures (Figure 97-7).

Question 70

What is the recommended diagnostic modality when significant radiographic abnormalities are not identified?

a) Ultrasonography

b) Computed tomography (CT)

c) Magnetic resonance imaging (MRI)

d) Nuclear scintigraphy

Answer 70

d) Nuclear scintigraphy

Question 71

Answer 71

Figure 97-6. Lateral nuclear scintigraphic image of the shoulder region demonstrating increased radiopharmaceutical uptake in the caudoproximal humeral region in a horse affected by a humeral stress fracture.

Question 72

What is the primary treatment for humeral stress fractures in horses?

Answer 72

Rest for 1 month

Question 73

When can a horse with a humeral stress fracture be allowed hand walking?

Answer 73

When no lameness is evident

Question 74

What percentage of horses with humeral stress fractures developed complete humeral fractures in two case series?

a) 0%

b) 5%

c) 10%

d) 15%

Answer 74

a) 0%

Question 75

What is the prevalence of humeral stress fracture recurrence in horses after rest and rehabilitation?

Answer 75

c) 15%

Question 76

In cases of humeral stress fracture recurrence, where does the recurrence often involve?

a) Contralateral limb

b) Proximal limb

c) Pelvic region

d) Head and neck

Answer 76

a) Contralateral limb

Question 77

Henderson VS 2020 Postinjury performance for differing humeral stress fracture locations in the racing thoroughbred - Which stress fracture location resulted in significantly greater postfracture earnings per start?

a) Caudodistal

b) Craniodistal

Answer 77

a) Caudodistal

Question 78

What was the median time it took for horses to return to racing post humeral stress fracture?

Answer 78

244 days

Question 79

What is essential for horses returning to training after rest and rehabilitation to prevent stress fracture recurrence?

a) Increased exercise intensity

b) Continued clinical observation and appropriate management

c) Medication

d) Dietary supplements

Answer 79

b) Continued clinical observation and appropriate management

Question 80

What conclusion can be drawn from the study regarding the prognosis for return to racing for thoroughbred racehorses?

a) Age significantly affects the prognosis.

b) Fracture location has no impact on the prognosis.

c) Return-to-race time varies significantly by location.

d) Prognosis for return to racing is good regardless of fracture location.

Answer 80

d) Prognosis for return to racing is good regardless of fracture location.

Question 81

Johnston et al 2021 EVJ The effect of stress fracture occurring within the first 12 months of training on subsequent race performance in Thoroughbreds in Hong Kong What were the most common sites for stress fractures among the horses in the study?

a) Femur and radius

b) Tibia and metacarpus

c) Humerus and tibia

d) Pelvis and spine

Answer 81

c) Humerus and tibia

Question 82

How did the race performance of horses with stress fractures compare to matched controls within the 12 months following diagnosis?

a) They had more race starts and higher earnings.

b) They had fewer race starts and lower earnings.

c) There was no significant difference in race performance.

d) They had fewer race starts but higher earnings.

Answer 82

They had fewer race starts and lower earnings.

Question 83

What was the effect of stress fractures on the overall career length of racehorses in the study?

Answer 83

It had no impact on their career length.

Question 84

Which type of humeral fracture is considered rare, involving the proximal humeral physis?

a) Type I fracture

b) Type II fracture

c) Type III fracture

d) Type IV fracture

Answer 84

d) Type IV fracture

Question 85

Answer 85

Question 86

How many reported cases of type IV fracture of the distal humerus have involved the lateral condyle?

Answer 86

d) Three

Question 87

What is the prognosis for distal physeal humeral fractures?

Answer 87

Grave

Question 88

How many of the reported cases of distal physeal humeral fractures survived, whether treated with stall confinement or internal fixation?

a) None

b) All

c) Some

d) Only one

Answer 88

a) None

Question 89

In the cases of avulsion fracture of the medial epicondylar physis managed with stall confinement, how many horses survived and became sound?

a) None

b) One

c) Two

d) All

Answer 89

b) One

Question 90

What is a common cause of humeral fractures in foals?

a) Accumulated stress remodeling

b) Traumatic events

c) Age-related degeneration

d) Genetic predisposition

Answer 90

Traumatic events

Question 91

Answer 91

Figure 97-11. Medial to lateral oblique radiograph of a complete, middiaphyseal, displaced, and overriding humeral fracture.

Question 92

A 6-month-old Quarter Horse filly presented for left diaphyseal humeral fracture demonstrating a dropped elbow appearance and the limb held in flexion.

Answer 92

left diaphyseal humeral fracture demonstrating characteristic marked swelling of the left humeral and shoulder region.

Question 93

How can humeral fractures be differentiated from ulnar fractures?

Answer 93

By the location of swelling

Question 94

Answer 94

Figure 97-12. (A) Medial to lateral postoperative radiograph demonstrating fixation of a diaphyseal humeral fracture with an intramedullary, interlocking nail with cerclage wire. (B) Caudolateral-craniomedial oblique radiographic postoperative image. Antibiotic-impregnated beads are present adjacent to the fracture line, and skin staples can be seen.

Question 95

Why is splinting the carpus in extension contraindicated for humeral fractures?

Answer 95

It encourages weight bearing on the affected limb.

Question 96

what are the types of humeral fractures?

Answer 96

proximal physeal fractures (rare and can be conservaitve or fixation
diaphyseal fracture ( fracture fixation
distal humera physis (++ common 65%, poor prognosis)

Question 97

in what type of fracture configurations may conservative management of humeral fractures be considered?

Answer 97

Long, oblique fractures with interdigitating fragments with stall confinement 4-6months or incomplete fractures if <300 kgs (but beter results with internal fixation

Question 98

Which type of humeral fractures are typically poor candidates for conservative management?

Answer 98

Short oblique to spiral fractures with marked overriding

Question 99

What is the preferred surgical approach for ORIF of diaphyseal humeral fractures in foals, according to the authors?

Answer 99

Modified lateral approach

Question 100

Describe the modified lateral incision/approach

Answer 100

modified lateral approach
LR - limb uppermost - incision beginning approximately** 4 cm proximal to the greater tubercle and extending distally to the level of the lateral epicondyle.**

The brachiocephalicus muscle is incised along its fibers in the proximal part of the incision to expose the** craniolateral surface of the greater tubercle** and proximal humeral metaphysis.

The** tendon of the biceps brachii muscle** may be retracted medially to expose the cranial aspect of the proximal humerus.

The deltoideus muscle is transected from its insertion on the deltoid tuberosity.

Distally, the origin of the** extensor carpi radialis muscle is elevated** from the craniolateral aspect of the lateral epicondyle.

If the brachialis muscle appears severely damaged, the radial nerve should be identified along its caudal border and its integrity confirmed prior to completing the fixation.

If the nerve is severed, the patient should be euthanized.

Question 101

Which fixation method provides resistance to bending but offers limited axial or rotational stability?a) Stacked pin fixation

b) Rush pin fixation

c) Plate fixation

d) Intramedullary interlocking nail (IIN) fixation

Answer 101

a) Stacked pin fixation

Question 102

in what type of equine patient has plate fixation alone been rarely successful for diaphyseal humeral fractures?

a) Foals with simple fractures

b) Large foals with complex fractures

c) Adult horses with complete fractures

d) Horses with minimal displacement fractures

Answer 102

b) Large foals with complex fractures

Question 103

What advantages are associated with intramedullary interlocking nail (IIN) fixation for humeral fractures?

Answer 103

Close proximity to the neutral axis of the bone

Question 104

Which of the following factors dictates the choice of fixation method for diaphyseal humeral fractures in foals?

Answer 104

The age and weight of the foal

Question 105

What type of plate fixation has been successfully reported as the primary method of repair for humeral fractures in equine patients?

Answer 105

Cranial plate fixation

Question 106

What is the main advantage of intramedullary interlocking nail (IIN) fixation in treating humeral fractures?

Answer 106

It allows for a less invasive surgical approach.

Question 107

What is the recommended number of interlocking screws in both the proximal and distal fracture fragments in ideal IIN fixation?

Answer 107

Three screws in each fragment

Question 108

What is the complicating factor associated with open fractures of the humerus?

Answer 108

They are a negative prognostic indicator.

Question 109

What is the most common complication in the support limb associated with conservative management of humeral fractures in adults?
a) MCP joint hyperextension
b) Tendon contracture
c) Radial nerve injury
d) Laminitis

Answer 109

d) Laminitis

Question 110

In foals, what type of angular deformity may result from support limb complications during conservative management of humeral fracutre?

a) Valgus deformity

b) Varus deformity

c) Hyperextension deformity

d) Flexural deformity

Answer 110

b) Varus deformity

Question 111

Answer 111

Figure 97-13. Medial to lateral postoperative radiograph of a diaphyseal humeral fracture repaired with an intramedullary, interlocking nail, cranially applied LCP, and cerclage cable. Antibiotic-impregnated beads are present adjacent to the fracture line, and skin staples can be seen.

Question 112

What is the recommended duration of stall rest for horses following diaphyseal humeral fracture repair?

a) 30 days

b) 60 days

c) 90 days

d) 120 days

Answer 112

b) 60 days

Question 113

When may horses begin a controlled daily hand walking regimen after diaphyseal humeral fracture repair?

Answer 113

After 90 days of stall rest

Question 114

In cases of carpal contracture resulting from radial nerve paresis or pain, what corrective procedure may be required?

Answer 114

Tenotomy of ulnaris lateralis and flexor carpis ulnaris insertions

Question 115

What is the primary reason for radial nerve paresis or paralysis in cases of diaphyseal humeral fractures?

Answer 115

Proximity to the humeral diaphysis

Question 116

What type of fixation method has documented a good prognosis for survival and an excellent prognosis for athletic performance among patients surviving to discharge?

a) Intramedullary interlocking nail (IIN) alone

b) Cranially applied dynamic compression plate (DCP) alone

c) Rush pins alone

d) Stacked pinning

Answer 116

a) Intramedullary interlocking nail (IIN) aloneor in conjunction with cranial bone plate

Question 117

most humeral fractures are open or closed?

Answer 117

Fortunately, the vast majority of humeral fractures are closed at presentation because the humerus lies deep within the soft tissue and muscular envelope, which prevents the fracture fragments from penetrating the overlying skin.

Question 118

what is particular in case of humeral fracture regarding immobilization?

Answer 118

There are no techniques that support or limit instability for humerus neither scapula - attempts to encourage weight bearing prior to fracture stabilization may compound injury to these structures and should be avoided.

Question 119

In diaphyseal fractures the method of fixation is dictated by

Answer 119

Weight of ofal
Age
Aavailable implants
Fracture configuration
Experience fo surgeon

Question 120

which types of humeral fractures exist?

Answer 120

1) Proximal humeral head (epiphysis and metaphysis
in foals)
2) Greater tubercle
3) Deltoid tuberosity
4) Mid‐diaphysis
5) Distal metaphysis
6) Distal condyle and epicondyle.

Question 121

describe the surgical tx for proximal humeral head epiphysis and metaphysis surgical tx in foals

Answer 121

LR - affected limb uppermost
10-15 cm skin incision is made
from the distal end of the scapula spine, parallel to the cranial edge of the deltoid muscle, to expose a tissue plane between the brachiocephalic muscle and the deltoid muscle border overlying the infraspinatus tendon attachment on the greater tubercle. Elevation and retraction of portions of** deltoid and brachiocephalic muscles expose the lateral surfaces of the proximal diaphysis of the humerus. Manipulation of the humeral shaft is used to align the humeral head. Secure fixation of complete fractures** of the proximal humerus is
achieved by dynamic compression plate (DCP) fixation on the craniolateral border of the humerus. A narrow 4.5 mm DCP is applied to the **humerus, extending from the cranial portion of the greater tubercle to the distal end of the deltoid tuberosity (Figure 31.9). The sheath of the biceps tendon should not be opened. Cortical screws** are used to secure the plate to the humeral head and humeral shaft, similar to plate repair of deltoid tuberosity fractures described in the next section. Additional cortical or lag screws can also be utilized to add better stabilization.

Question 122

what does literature say about middle and distal diaphyseal fractures?

Answer 122

series describing repair of humeral fractures in
horses. Most diaphyseal fractures in horses and
foals are short to long oblique spiral fractures, with some fracture end overriding (Figure 31.12).

Question 123

what is the treatment for displaced middle or distal diaphyseal humeral fractures?

Answer 123

Displaced fractures in adults are difficult to treat by
internal fixation and the principal decision has to be
between euthanasia, extended stall rest, or an attempt at internal fixation
Generally, smaller adults, and younger
horses less than a year of age, are better treated by open reduction and double plating.

Question 124

describe surgical intervention for middle or distal diaphyseal humeral fracture

Answer 124

LR - limb uppermost
Skin incision is made over the cranial surface of the humerus, extending distally
from the cranial eminence of the greater tubercle to the cranial border of the radius, over the extensor carpi radialis muscle. The subcutaneous tissues are divided, and the superficial branch of the cephalic vein is ligated and severed. Proximally, the brachiocephalic muscle is divided parallel to the fibers of its fleshy belly to expose the deltoid tuberosity. Distally, the brachiocephalic muscle can be divided from the brachial fascia and retracted craniomedially. The attachments of the brachiocephalic muscle are severed from the humeral crest.
If a second plate is to be applied laterally, the insertion of the deltoid muscle is partially or completely severed from the tuberosity. The **biceps brachii on the cranial surface of the humerus is easily separated and retracted medially. The brachialis muscle in the musculospiral groove of the humerus is isolated from the humerus,
with care taken to avoid the radial nerve adjacent to the caudal border of the muscle.** The brachialis muscle is not divided. The origins of the extensor carpi radialis muscle on the humerus are gently severed; this muscle is retracted laterally, and the biceps and brachialis muscles are retracted medially (see Figure 31.17). Large self‐retaining retractors are placed. The radial nerve, coursing with the deep surface of the extensor carpi radialis muscle, must be identified and preserved.
The** brachialis muscle** is alternately retracted craniomedially or caudolaterally during the placement of implants. The fracture is reduced and aligned using axial traction applied by a femoral distractor attached to the greater tubercle and distal humeral condyles, or obstetric chains applied to the distal limb and attached to a winch. Fracture reduction is maintained by separate lag screws, cerclage wires, or bone‐holding forceps, and the cranial 4.5 mm broad DCP is contoured and applied (Figure 31.18). The LCP provides a more stable fixation and is preferred for most plate repairs of humeral fractures. Initial stabilization using a push–pull device in either end of the cranially applied LCP also assists in maintenance of fracture reduction
during the initial application of the plate (see
Figure 31.18). Where an LCP is being used, the initial
screws are 5.5 mm cortical screws, to assist in compressing the plate onto the cranial surface of the humerus.
The distal extremity of the cranial plate needs a marked concavity to approximate the cranial metaphyseal and epicondylar region of the distal humerus. The distal screws are directed into the medial epicondyle of the caudodistal
humerus, to avoid the olecranon fossa.
Application of a locked screw in the distalmost hole of the cranial LCP is possible (Figure 31.19), although use of a cortical screw allows better targeting of the medial epicondyle.
Use of 5.5 mm cortical screws is recommended;
6.5 mm cancellous screws are also utilized in the soft metaphyseal
bone of the proximal humerus, where the trans
cortex is not engaged. If the foal is heavier than 150 kg, a second plate is
applied on the lateral aspect of the humerus, immediately caudal to the deltoid tuberosity (see Figures 31.18 and 31.19). This plate can be an LCP, or a narrow or broad 4.5 cm DCP,or a limited‐contact dynamic compression plate (LC‐DCP), depending on the age and size of the animal. The lateral plate is generally shorter than the cranial implant and is applied so that the screws alternate with those of the cranial plate (see Figure 31.19).
Insertion of the distal‐most screws in the lateral plate
may require separate stab incisions in heavily muscled horses. Use of a laterally applied LCP introduces difficulty in inserting the locked drill guides and locking head screws through the extensive triceps musculature and into the appropriate threaded portion of the combi hole.
To facilitate this, locked screws are often applied in the central regions of the LCP, where the drill guide can be visually aligned with the threaded portion of the plate hole (see Figure 31.18). Direct visualization becomes more difficult toward the ends of the LCP, due to the limited dissection available through the lateral approach to the humerus.

Question 125

Answer 125

Figure 31.17 Cranial approach to the humerus for diaphyseal and some distal humeral fractures. A broad 4.5 mm plate has been applied
to the cranial aspect of the humerus, and a second plate over the lateral surface.

Question 126

what is the treatment for small fractures of the distal condyles and epicondylar region that occasionally occur in adults?

Answer 126

Fragments from these types of fractures
can be removed by arthroscopic means and the contamination and sepsis from the wound treated appropriately. More extensive fractures of the distal portions of the condyle and epicondyle often involve the medial portion of the humerus, and may need lag screw repair using the open approaches described for access to the medial regions of the elbow