ANZCVS 2014

Question 1

a) List the tendons that comprise the common calcaneal tendon.

Answer 1

Gastrocnemius
Superficial Digital Flexor
Common tendon (Gracilis, Biceps Femoris and Semitendinosus)

Question 2

b) Name and draw three (3) suture patterns commonly used for tenorrhaphy.

Answer 2

• Locking Loop Pattern
• Three-Loop Pulley
• Bunnell Suture

Question 3

c) Describe the process of tendon healing following surgical apposition with minimal (less than one millimeter) gap. (10 marks)

Answer 3

1) Inflammatory phase (first 14 days): Hemostasis (platelet clot), Cell Migration (Leukocytes, Monocytes and lymphocytes), release of histamine and bradykinin improve vascular permeability. Fibroblasts from MSC produces a fibrin scar.
2) Proliferative phase (2 to 4 weeks): Fibroblast, myofibroblast and endothelial cell proliferation replace inflammatory tissue with granulation tissue. Tendon-bone adhesion improves. Fibroblasts begin to produce Collagen Type III after second week.
3) Maturation/Remodeling (4 to 12+ weeks): Collagen III gradually replaced with Collagen I, forming dense connective tissue. Tendon is integrated within bone.

Question 4

d) State the approximate strength (expressed as a percentage of original tendon strength) attained in a surgically repaired tendon by:

Answer 4

i. 6 weeks following repair (1 mark) : 56% (Dueland, R et al. J Am Anim Hosp Assoc. 1980)
ii. 12 months following repair. (1 mark): 79% (Dueland, R et al. J Am Anim Hosp Assoc. 1980)

Question 5

e) Discuss appropriate post-operative management and rehabilitation of a 30 kg dog following surgical repair of a common calcaneal tendon rupture. Include the rationale behind each recommendation. (9 marks)

Answer 5

The tendon will only regain 56% of its original strength in the first 6 weeks, so the tarsus must be strongly supported during this phase to prevent full dorsal flexion. Options include external coaptation (Splint) + Calcaneo-tibial screw or external fixation. Hinged splints and external fixators can be constructed in such way as to allow limited tarsal extension (not flexion) for the first 3 weeks. Tarsal range of motion can be gradually increased over 2 to 10 weeks. Activity is limited to brief leash walks for the first 10 weeks. Therapeutic ultrasound or extracorporeal shock wave therapy may improve tissue perfusion and stimulate faster healing.

Question 6

Gastric dilatation-volvulus (GDV).
In your answer consider the sequence of events that results in dilatation and volvulus of the stomach (7 marks) and the specific pathophysiologic consequences that GDV has on the circulatory system (8 marks),

Answer 6

Pathoanatomy: The pylorus and proximal duodenum move ventrally and then cranially, stretching the hepatogastric ligament. The pylorus continues to move from right to left, creating a fold in the stomach, and eventually coming to rest on the left side of the abdomen dorsal to the esophagus. This movement creates traction on the gastrosplenic ligament and short gastric vessels, which eventually rupture.

Circulatory consequences: As the stomach dilates with fluid and especially gas it applies pressure upon the caudal vena cava, significantly decreasing cardiac preload. Poor coronary blood flow and production of myocardial depressant factor lead to myocardial ischemia and cardiogenetic shock. Resultant cardiac arrhythmias are observed in 65% of cases (first 72 hours post-op) and further decrease systemic perfusion. Concurrent compression of the portal vein results in portal hypertension and venous stasis, decreasing tissue perfusion throughout the entire GI tract and creating mucosal death and bacterial translocation.

Question 7

Gastric dilatation-volvulus (GDV).
In your answer consider the consequences that GDV has on the gastrointestinal system (8 marks),

Answer 7

Gastrointestinal consequences: Gas distension compress and collapse gastric capillaries, leading to mucosal necrosis. This is compounded by systemic hypotension due to cardiogenetic shock, often leading to full-thickness gastric wall necrosis. Gastric mucosal necrosis allows bacterial translocation into the bloodstream,

Question 8

Gastric dilatation-volvulus (GDV).
In your answer consider the consequences that GDV has on the respiratory system (8 marks),

Answer 8

Respiratory system: Gastric distension applies pressure on the diaphragm, making inspiration more difficult and further decreasing oxygen delivery.

Question 9

Gastric dilatation-volvulus (GDV).
In your answer consider the systemic consequences of GDV

Answer 9

Systemic effects: Hypovolemia, metabolic and respiratory acidosis, hypoxemia and the creation of oxygen-reactive species (reperfusion injury) lead to oxidative damage to kidneys and central nervous system. The role of reperfusion injury remains debatable and further studies are needed to determine when and how it is most severe.

Question 10

a) List the major types of burn injuries experienced in small animals (2 marks) and explain the basis by which burns cause damage to tissue (2 marks).

Answer 10

Thermal burns: Exposure to temperature extremes, either high or low, sufficient to cause cellular damage. This damage occurs when heat is transferred via conduction, convection or radiation.

Chemical burns: Exposure to chemicals that cause tissue necrosis, either directly via chemical reactivity or indirectly via secondary thermal effects.

Electrical burns: Exposure to electrical current of sufficient energy that passes through the patient and causes cell necrosis along its path.

Radiation burns: Exposure to ionizing radiation at levels that cause acute cell death, such as solar radiation or radiation therapy for neoplastic disease.

Question 11

b) Describe the common classification system of burns used in small animal patients. (5 marks)

Answer 11

Two common classification schemes exist:
Five-degree classification scheme based on depth:
- Overall it can be said that the amount of heat transfer into tissues, rather than its source, determines the degree of the burn

First degree: superficial. Only the epidermis is affected. No scarring
Second-degree: full thickness epidermal necrosis that extends into the underlying dermis, with resultant fluid exudation and occasionally blistering (more common in humans).
Third degree: burn extends through the dermis and into underlining subcutaneous tissue
Fourth degree: burn extends through the underlining muscle or fascia
Fifth degree: burn extends into bone.

Question 12

c) Explain the ‘rule of nines’ in relation to burn injuries. (3 marks)

Answer 12

The Wallace’s “rule of nines” was adapted from human medicine for use in veterinary burn victims. It divides the body into regions which are multiples of 9% of total body surface area.
The head and neck are counted as one “nine”, or 9%. Each forelimb is another 9% and each hindlimb is “two nines”, or 18%. The dorsal and ventral halves of the trunk are another 18% each.

Question 13

d) An adult male entire Labrador retriever is brought to your clinic following a house fire. He has sustained major burns to approximately 30% of body surface area and is suffering from smoke inhalation. Discuss the pathophysiology of these injuries at a local level

Answer 13

At a local level the severity of a burn injury radiates outward from the greatest point of energy delivery to the tissue. This leads to the formation of three distinct zones: Zone of Coagulation (inner-most zone, with no viable tissue), Zone of Stasis (reduced tissue perfusion due to increased vessel permeability, with fragile but viable cells) and Zone of hyperemia (area of inflammatory response). Local perfusion is upregulated immediately after the burn by postganglionic autonomic stimulation and NO synthesis upregulation. The inflammatory response is characterized by vasodilation, increased capillary permeability, edema and influx of inflammatory cells. Wound healing is significantly slower than surgical wounds, presumably due to very low levels of fibroblast growth factor (FGF-2, less than 5% normal).

Question 14

d) An adult male entire Labrador retriever is brought to your clinic following a house fire. He has sustained major burns to approximately 30% of body surface area and is suffering from smoke inhalation. Discuss the pathophysiology of these injuries at the pulmonary system

Answer 14

• Pulmonary System (smoke inhalation): Consists of two components, thermal and toxic. The thermal component is limited to the upper airways, therefore the majority of the injury is toxic. Housefire smoke contains more than 250 toxic compounds, like carbon monoxide (from incomplete carbon combustion), hydrogen cyanide (from nitrogen-containing products like nylon, formica, melamine, wool) and inorganic acids from Teflon, neoprene and plastics (hydrochloride, hydrogen fluoride, etc..).

Carbon monoxide reduces tissue oxygen delivery by direct binding to hemoglobin, by promoting carboxyhemoglobin formation and by binding to myoglobin.

Hydrogen Cyanide binds to mitochondrial cytochrome oxidase, preventing cell respiration.

Inorganic acids, like hydrochloride, are intensely irritating to respiratory mucous membranes promoting laryngospasm and bronchospasm.

The lung’s response to smoke inhalation consists of increased pulmonary vascular permeability, venoconstriction, rapid accumulation of fluid, mucous and neutrophils within the alveoli and airways, hallmarks of pulmonary edema. These are combined with atelectasis, deactivation of pulmonary surfactant and decreased ling compliance, resulting in Acute Respiratory Distress Syndrome. Cytokines, eicosanoids and substance P are produced by damaged tissue and the GI tract, reaching the lungs via the lymphatic system. Eicosanoid Thromboxane A2, synthesized by pulmonary macrophages, causes marked pulmonary vasoconstriction and increased vascular resistance.

Question 15

d) An adult male entire Labrador retriever is brought to your clinic following a house fire. He has sustained major burns to approximately 30% of body surface area and is suffering from smoke inhalation. Discuss the pathophysiology of these injuries at the general cardiovascular system (not heart)

Answer 15

• General Cardiovascular System (hypovolemia, vascular disfunction, generalized edema): Consists of fluid extravasation, evaporation, blood hyperviscosity and vasoconstriction. The end result being tissue hypoxia and metabolic acidosis.

Fluid extravasation into the extravascular space begins within 10 min of a burn, and is mediated by histamine, complement activation and oxygen free radical activation of myosin-contraction of endothelial cells and endothelial cell damage. Systemic extravasation rapidly overwhelms the lymphatic system and hypovolemia/edema ensue as protein-rich fluid accumulates in the interstitial space.

Evaporation through burned skin is 3 to 20% higher than through intact skin. Even a partial thickness burn (second degree) can increase evaporation by 35%.

Hyperviscosity occurs as a result of decreased erythrocyte deformability, which in combination with hypovolemia leads to hyperviscosity and compromises blood flow characteristics.

Question 16

d) An adult male entire Labrador retriever is brought to your clinic following a house fire. He has sustained major burns to approximately 30% of body surface area and is suffering from smoke inhalation. Discuss the pathophysiology of these injuries at the cardiovascular system (heart)

Answer 16

• Cardiovascular System – Heart (myocardial effects): large burns (50% total body surface) leads to oxidative injury to the sarcoplasmic reticulum, inducing calcium leakage into the cytoplasm. Intracellular hypercalcemia significantly decreases myocardial contractility. Toxic effects of carbon monoxide, particularly the production of carboxyhemoglobin, leads to cardiomyocyte necrosis.

Question 17

d) An adult male entire Labrador retriever is brought to your clinic following a house fire. He has sustained major burns to approximately 30% of body surface area and is suffering from smoke inhalation. Discuss the pathophysiology of these injuries at the Gastrointestinal system

Answer 17

• Gastrointestinal system: burn injuries significantly increase the apoptotic rate of gut mucosal cells, without a corresponding increase in mucosal proliferation, leading to loss of mucosal integrity. Translocation of endotoxins, gut bacteria and cytokines quickly lead to septic shock. Gastroenteric motility is also significantly impaired.

The liver is also significantly impaired by oxidative stress , leading to increased rate of apoptosis and proliferation. Acute phase protein production increases and albumin production decreases.

Question 18

d) An adult male entire Labrador retriever is brought to your clinic following a house fire. He has sustained major burns to approximately 30% of body surface area and is suffering from smoke inhalation. Discuss the pathophysiology of these injuries at the renal, hemopoietic and immune systems

Answer 18

• Renal System: Acute renal failure may occur as a result of hypovolemia, hypoalbuminemia, hemoglobinemia, myoglobinemia, sepsis and the use of nephrotoxic antibiotics.
• Hematopoietic System: Burn injury produces an immediate and persistant reduction of circulating RBC’s, known as “burn anemia. This is a result of RBC loss and decreased erythropoiesis.
• Immune system: burns produce significant negative effects on lymphocyte production and function. Lymphocyte apoptosis is upregulated by TNF-a. Sympathetic nervous system-mediated inhibition of T-cells lead to increased susceptibility to sepsis.

Question 19

d) An adult male entire Labrador retriever is brought to your clinic following a house fire. He has sustained major burns to approximately 30% of body surface area and is suffering from smoke inhalation. Discuss the pathophysiology of these injuries at the neurologic system

Answer 19

• Neurologic system: burns rapidly cause hyperalgesia through the release of prostaglandins and kinins by inflammatory cells. The resulting intense pain stimulates a massive sympathetic discharge responsible for the cardiovascular events of burn shock.

Question 20

d) An adult male entire Labrador retriever is brought to your clinic following a house fire. He has sustained major burns to approximately 30% of body surface area and is suffering from smoke inhalation. Discuss the pathophysiology of these injuries at the neurologic system

Answer 20

• Metabolic and endocrine changes: immediately following a burn injury the body enters a hypometabolic phase (“ebb phase”), followed by a hypermetabolic phase (“flow phase”). Basal metabolic rate increases by 100% during the flow phase due to increased heat loss (evaporation, increased hypothalamic set point due to inflammatory cytokines and eicosanoids). The resulting nonproductive metabolic work produces the required additional heat at a significant energy cost to the patient. Aminoacids are utilized for energy production, leading to loss of lean body mass (poor prognostic indicator).

Question 21

a) List four (4) proposed etiological factors for canine osteoarthritis. (2 marks)

Answer 21

• Genetics
• Age
• Injury
• Developmental deformity/abnormality
• Systemic factors (Obesity)

Question 22

b) The pathogenesis of canine osteoarthritis involves changes to the cartilage, synovium, synovial fluid, subchondral bone and nervous system. Describe the macroscopic and microscopic changes seen in articular cartilage. Include in your answer a brief discussion of the mediators of osteoarthritis. (9 marks)

Answer 22

The pathophysiologic process of osteoarthritis can be divided into three overlapping phases:

1. Initial phase: at a microscopic level the extracellular matrix degrades, water content increases, aggrecan molecule size decreases and the structure of collagen network is damaged. Macroscopically this process is perceived as reduced cartilage stiffness.
2. Second phase: Chondrocytes try to compensate with enhanced proliferation and metabolic activity. Chondrocyte clusters form through cloning and secrete extra matrix molecules. This phase can persist for months to years. The macroscopic result is Increased cartilage thickness.
3. Third phase: Chondrocytes are no longer able to keep up their reparative activity. Activated macrophages and fibroblast-like synoviocytes secrete inflammatory cytokines such as IL-1 and TNF-alpha, which upregulate the productions of MMP’s and other proteolytic enzymes like aggrecanases. Within chondrocytes, IL-1 and TNF-alpha stimulate the production of nitric oxide (NO), which has a major catabolic effect. COX-2 produces PGE2.These enzymes (MMP’s, aggrecanases and PGE2) degrade Type II collagen and aggrecan. These events are macroscopically perceived as cartilage loss.

Question 23

c) Damaged hyaline cartilage is typically replaced by fibrocartilage. Describe how hyaline cartilage and fibrocartilage differ in structure and function. (5 marks)

Answer 23

Hyaline cartilage and fibrocartilage are structurally different in the following ways:

• Amount of collagen fibers: Fibrocartilage contains many more collagen fibers
• Type of collagen: Fibrocartilage contains collagen Type I and II. Hyaline cartilage only contains collagen type II
• Chondrocytes: Fibrocartilage contains fewer chondrocytes in the lacunae
• Appearance: Fibrocartilage is glass-like, translucent to bluish-white. Hyaline cartilage is white.

When it comes to function, hyaline cartilage is richest in glycosaminoglycans which combine with a core protein to form proteoglycans. Proteoglycans retain water water, thus providing an exceedingly smooth and shock-absorbing surface for gliding between articular components. Fibrocartilage is rich in collagen I and II, with much smaller amounts of proteoglycans. When produced in response to injury, fibrocartilage is regarded as a transitional tissue between hyaline cartilage and regular connective tissue such as tendons or ligaments. These characteristics make fibrocartilage very resistant to compression but much less smooth than hyaline cartilage.

Question 24

d) List the approximate differential cell count, expressed as percentages of mononuclear cells and neutrophils, that would typically be found in synovial fluid aspirated from each of the following diseased canine joints. You may wish to present your answers in the form of a table. (6 marks) “normal”, DJD, IMPA and Septic Arthritis

Answer 24

Fluid Type

Fluid Color

WBC/uL

Neutrophils (%)

Mononuclear cells (%)

Normal

Clear pale yellow

<3K

<1.4%

>98

DJD, Trauma, hemarthrosis

Clear orange

3 to 5K

<10

>90

IMPA

Cloudy yellow-white

4 to 370K

>90

<10

Septic arthritis

Cloudy yellow-white

15 to 260K

70-95

5-20

Question 25

The proposed mechanisms of action for non-steroidal anti-inflammatory drugs (NSAIDs) (4 marks)

Answer 25

NSAID’s inhibit the cyclooxygenase enzyme (COX), required to convert phospholipid membrane-derived arachidonic acid into thromboxanes, prostaglandins and prostacyclins. There are two COX isoenzymes: COX-1 and COX-2. COX-1is constitutively expressed in the body, playing important roles in maintaining GI mucosal lining integrity, renal function and platelet aggregation. COX-2 is not constitutively expressed but rather induced during the inflammatory response.

Question 26

Potential adverse effects of NSAIDs, including reference to the mechanisms by which these occur in two (2) named organs.

Answer 26

• GI ulceration: likely due to inhibition of COX-1 (constitutive) preventing normal production of prostaglandins responsible for regulation of blood flow to the gastric mucosa, stimulation of bicarbonate and mucous secretions that protect the gastric mucosa.
• Renal adverse effect: COX-2 play a role in the production of prostaglandins that maintain renal hemodynamics. Inhibition of this enzyme is usually harmless in a normal patient, but in a patient with preexisting renal disease may lead to renal papillary necrosis and interstitial nephritis, resulting in acute renal dysfunction. COX-2 selective NSAIDS are not safer regarding the potential for renal injury.
• Hepatic adverse effect: considered an idiosyncratic reaction, possibly related to the generation of acyl glucuronide metabolites that promote a toxic immunologic response in the liver.
• Hematologic adverse effect: inhibition of COX-1 prevents platelets from forming thromboxane A2 (TXA2), a potent platelet aggregating agent. This results in prolonged clotting times, which may be significant in cased of GI ulceration, injuries of surgical procedures.

Question 27

1. A seven-year-old male entire German shepherd dog is presented to your clinic with a three-day history of lethargy and anorexia. On physical examination, he is febrile (40.4°C) and has a large, painful and fluctuant prostate. You suspect a prostatic abscess.

Answer all parts of this question:

a) Prostatic infections are uncommon in dogs. List the urinary defense mechanisms that normally prevent the development of prostatic infections. (2 marks)

Answer 27

• Shedding of pathogens bound to exfoliating urethral cells.
• Trapping of pathogens in secreted mucous
• Intermittent washout by urine
• Local production of immunoglobulins, cytokines and defensins
• Mobilization of leukocytes

Question 28

1. A seven-year-old male entire German shepherd dog is presented to your clinic with a three-day history of lethargy and anorexia. On physical examination, he is febrile (40.4°C) and has a large, painful and fluctuant prostate. You suspect a prostatic abscess.

Answer all parts of this question:

b) Describe the appropriate pre-surgical management of this case, including any additional diagnostic procedures warranted. (9 marks)

Answer 28

Pre-surgical management should include CBC/Biochemistry/Pt/Ptt, urinalysis, imaging (radiographs or ideally ultrasonography) and US-guided FNA for cytology and culture. Expected Labwork findings will likely include leukocytosis, but patients with peritonitis due to ruptured prostatic abscess may be leukopenic; elevated ALP is quite typical; elevations on ALT and globulins, as well as hypoglycemia and azotemia may be present. Urinalysis will likely reveal leukocytes, RBC’s and microorganisms.

Question 29

1. A seven-year-old male entire German shepherd dog is presented to your clinic with a three-day history of lethargy and anorexia. On physical examination, he is febrile (40.4°C) and has a large, painful and fluctuant prostate. You suspect a prostatic abscess.

c) You elect to perform prostatic omentalisation. Describe the technique of prostatic omentalisation, including any ancillary procedures you wish to perform. You may use labelled diagrams if you wish. (10 marks)

Answer 29

The prostate is accessed via a ventral celiotomy. A urinary catheter should be utilized to facilitate identification of the urethra. Stab incisions are created on the lateral aspects of the prostate, ventral to the urethra, and enlarged by excision of capsular tissue to a size sufficient for introduction of the forefinger. Abscess loculations must be careful and thoroughly broken-down using hemostats. A hemostat is introduced into one of the openings and out the other, grasping omentum and drawing it across the inner aspect of the abscess cavity. Last, the omentum is anchored to the capsular wall with one or two monofilament absorbable mattress sutures. The abdomen is lavaged and closed routinely. Castration is also highly recommended.

Question 30

1. A seven-year-old male entire German shepherd dog is presented to your clinic with a three-day history of lethargy and anorexia. On physical examination, he is febrile (40.4°C) and has a large, painful and fluctuant prostate. You suspect a prostatic abscess.
   d) Describe the properties of the omentum that allow this technique to be successful. (3 marks)

Answer 30

The omentum has a high absorptive capacity and is able to efficiently remove exudate. It also functions as a conduit for additional blood supply, delivery of macrophages and leukocytes. The omentum is also able to quickly produce fibrin and seal the affected area, preventing further abdominal contamination.

Question 31

1. A seven-year-old male entire German shepherd dog is presented to your clinic with a three-day history of lethargy and anorexia. On physical examination, he is febrile (40.4°C) and has a large, painful and fluctuant prostate. You suspect a prostatic abscess.

e) List three (3) alternative procedures that may be used to treat prostatic abscessation. (3 marks)

Answer 31

• Marsupialization – The abscess is drained and the capsular all is anchored to a parapenile stoma site for continuous drainage. Rarely performed, multiple complications.
• Ventral Drainage – Penrose drain placed through the prostatic capsule and caudal ventral abdominal wall. Ideally two separate drains should be placed into each lobe to avoid urethrocutaneous fistulas (associated with circumurethral placement). Closed drains may be beneficial. Requires hospitalization. More successful than marsupialization but still associated with 20% mortality rate.
• Partial prostatectomy – Facilitated by temporary occlusion of blood supply using a tourniquet distal to the renal arteries and use of vessel sealing device to control capsular bleeding. The use of an ultrasonic aspirator also greatly improves the accuracy of the procedure. Approached via two ventral prostatic capsulotomies. Care is taken to avoid trauma to the urethra and dorsal neurovascular structures. The urethra is pressure-tested at the end of the procedure and any leaks are oversewed. The ventral aspect of the capsule is left open, closed or omentalized. Main complications include considerable blood loss and urinary incontinence.

Question 32

1. A seven-year-old male entire German shepherd dog is presented to your clinic with a three-day history of lethargy and anorexia. On physical examination, he is febrile (40.4°C) and has a large, painful and fluctuant prostate. You suspect a prostatic abscess.
   f) State which empiric antibiotics would be appropriate for this case. Include your reasoning for this selection. (3 marks)

Answer 32

The most common pathogens associated with prostatic infections include E. coli, Staphylococcus spp, Streptococcus spp, Proteus mirabilis, Klebsiella spp., Mycoplasma and Pseudomonas spp. Empiric antibiotic choices must must have know efficacy against these pathogens as well as good blood-prostate barriers penetration. Previous theories regarding prostatic lipid barrier have been more recently questioned, based on the argument that the inflammatory response to infection disrupts the lipid barrier and significantly improves antibiotic penetration. Traditionally good options include fluoroquinolones, Trimethoprin-Sulfas and Chloramphenicol.

Question 33

1. An eight-year-old male golden retriever presents to your clinic with a raised, non- pigmented, firm three-centimeter diameter mass arising from the gingiva in the rostral third of the left maxilla that has grown over the last two months.

Answer all parts of this question:

1. a) List the four (4) most common malignant oral tumours in dogs, in order from most to least common, stating the approximate percentage incidence for each.

Answer 33

1. Malignant Melanoma (40%)
2. SCC (30%)
3. Fibrosarcoma (20%)
4. Osteosarcoma (10%)
5. Canine Acanthomatous Ameloblastoma – CAA (5%)

Question 34

1. An eight-year-old male golden retriever presents to your clinic with a raised, non- pigmented, firm three-centimeter diameter mass arising from the gingiva in the rostral third of the left maxilla that has grown over the last two months.

Answer all parts of this question:

1. b) List the two (2) most common oral tumors in cats.

Answer 34

1. SCC
2. Fibrosarcoma

Question 35

1. An eight-year-old male golden retriever presents to your clinic with a raised, non- pigmented, firm three-centimeter diameter mass arising from the gingiva in the rostral third of the left maxilla that has grown over the last two months.

Answer all parts of this question:

1. c) Describe the appropriate diagnostic approach to investigate the described mass prior to any definitive treatment.

Answer 35

• Thoracic radiographs must be obtained for any dog with suspected oral tumors due to high incidence pf pulmonary metastasis.
• Oral radiographs obtained under anesthesia can help determine the extent of the tumor but may grossly underestimate bone involvement. This is because bone must lose a significant amount of mineral content before acquiring lytic radiographic appearance. CT and MRI are far superior, and highly recommended for caudal maxillary and mandibular lesions.
• Incisional biopsy: the most common oral malignancies have variable metastatic potential but similar potential for local invasiveness. Biopsies rarely influence the surgical plan but are still recommended to confirm malignancy and plan post-operative care (radiation therapy). Biopsies must be obtained via a deep wedge of tissue as superficial samples are usually non-diagnostic (usually inflammatory or necrotic tissue).
• Regional Lymph Node Assessment: Palpation for lymphadenopathy is an unreliable indicator of metastasis (sensitivity 70%; Specificity 51%). Fine needle aspirate cytology of mandibular LN is usually performed, but may only identify 54% of metastatic cases. A simple surgical technique that allows excision of all three nodes draining the oral cavity as been described (Smith MM, A Am Anim Hosp Assoc 1995) – mandibular, parotid and medial retropharyngeal. This significantly improves the accuracy of regional LN assessment in these cases.

Question 36

1. An eight-year-old male golden retriever presents to your clinic with a raised, non- pigmented, firm three-centimeter diameter mass arising from the gingiva in the rostral third of the left maxilla that has grown over the last two months.

Answer all parts of this question:

d) The histopathology report describes the mass as a low grade fibrosarcoma. Given the patient signalment and case history, describe the suspected biological characteristics of this tumor.

Answer 36

Fibrosarcomas may occur as histologically low grade, biologically high grade. They are composed of fibrous connective tissue that aggressively invades bone, requiring wide excisions. Metastasis is rare but possible.

Question 37

1. An eight-year-old male golden retriever presents to your clinic with a raised, non- pigmented, firm three-centimeter diameter mass arising from the gingiva in the rostral third of the left maxilla that has grown over the last two months.

Answer all parts of this question:

e) Briefly outline the preferred treatment option in this case. (1 mark)

Answer 37

Wide surgical excision via rostral partial maxillectomy. Adjuvant therapy, likely radiation, if surgical margins were narrow of incomplete.

Question 38

1. An eight-year-old male golden retriever presents to your clinic with a raised, non- pigmented, firm three-centimeter diameter mass arising from the gingiva in the rostral third of the left maxilla that has grown over the last two months.

Answer all parts of this question:

f) Describe the technique for partial maxillectomy, including relevant landmarks.

Answer 38

Partial maxillectomy – The procedure is performed within the oral cavity, and begins with selection of the appropriate margins based on pre-operative imaging, ideally CT. Soft tissues are sharply incised to the level of the bone, including labial mucosa, gingiva and palate. Electrocautery is used to control diffuse hemorrhage. Osteotome is used to transect the thin maxillary and palatal bones. Major vessels are not encountered during rostral maxillectomies. If the excision is extending into the mid 1/3 of the maxilla, particularly caudal to the infraorbital foramen, the major palatine and infra-orbital arteries and the infraorbital nerve will have to be transected. This can prove challenging and is best achieved once the section containing the tumor is expediently removed. Bleeding from nasal turbinated is controlled with pressure, hemostatic gelatin and topical epinephrine (1mg/ml diluted 10X with NaCl, applied to the nasal cavity and drained after 60 sec). Closure is accomplished by apposing the buccal mucosa to the edge of the palatal mucosa using monofilament absorbable suture.

Question 39

1. An eight-year-old male golden retriever presents to your clinic with a raised, non- pigmented, firm three-centimeter diameter mass arising from the gingiva in the rostral third of the left maxilla that has grown over the last two months.

Answer all parts of this question:

g) Discuss the prognosis for oral fibrosarcomas in dogs.

Answer 39

The prognosis is variable and highly depends on early diagnosis and aggressive therapy. White et al, 1991 reported a 50% 1 year survival for FSA after surgical treatment.

Reported 1 year survival with surgery alone for the 4 most common malignancies are as follows (from Tobias, p.1673-1674)

MM 0%

SCC 85%

FSA 50%

OSA 40%

Question 40

A five-year-old female neutered Border Collie presents to your clinic 24 hours after a road traffic accident. She is non-weight-bearing on the left forelimb but otherwise well. Radiographs of this limb demonstrate a lateral luxation of the antebrachium relative to the humerus.

Describe, using labelled diagrams, the functional anatomy of the normal canine elbow, including relevant neural structures. (12 marks)

Answer 40

Question 41

A five-year-old female neutered Border Collie presents to your clinic 24 hours after a road traffic accident. She is non-weight-bearing on the left forelimb but otherwise well. Radiographs of this limb demonstrate a lateral luxation of the antebrachium relative to the humerus.

b) Explain why the majority of traumatic elbow luxations are lateral luxations - ie the radius and ulna luxate laterally relative to the humerus. (1 mark)

Answer 41

Most of the elbow luxations are lateral because the distal slope and large size of the trochlea (medial humeral condyle) prevent medial displacement of the radius and ulna. Reportedly 92% to 100% of elbow luxations are lateral. The relatively larger size of the lateral collateral ligament in comparison to the medial collateral may also offer greater resistance to medial luxation.

Question 42

A five-year-old female neutered Border Collie presents to your clinic 24 hours after a road traffic accident. She is non-weight-bearing on the left forelimb but otherwise well. Radiographs of this limb demonstrate a lateral luxation of the antebrachium relative to the humerus.

c) Describe how to perform a closed reduction of a lateral elbow luxation. Include any subsequent management in your answer. (9 marks)

Answer 42

The reduction technique is influenced by the position of the anconeal process. In most cases it is positioned lateral to the olecranon fossa. The primary goal is to “hook” the anconeal process in the olecranon fossa and use it as a fulcrum point for radial head/ulnar reduction. This is initially accomplished by flexing the elbow beyond 90 degrees and internally rotating (pronating) the antebrachium over a soft support such as a rolled towel. Medially directed pressure is applied upon the lateral aspect of the olecranon while stabilizing the distal humerus. A large towel clamp or Lewin bone clamp can be applied through the skin to the olecranon to allow additional caudal traction. Once the anconeal process is back into the olecranon fossa, the elbow is slightly extended with the antebrachium supinated and adducted. Medially directed pressure is applied to the radial head to force it medially while continuously extending the elbow joint. This process may be slow and takes patience to overcome muscular tension and capsular contraction. Once reduction is achieved the elbow is placed throught several gently range-of-motion cycles to remove blood clots and synovial capsule folds from the articular space.

Following reduction, the joint should be radiographically evaluated. Mild redial head subluxation may be observed as a result of anesthesia-induced muscle relaxation. Extended projections with varus/valgus stress will help document further instability. The Campbell test can be performed to evaluate collateral ligament integrity. This is done by flexing the elbow and carpus to 90° to release the anconeal process from the olecranon fossa, forcing the elbow joint to rely upon the collateral ligaments for stability. Mild instability will likely resolve spontaneously, while easy dislocation should prompt open reduction and ligament reconstruction. The same applies to gross varus/valgus instability. Range of motion and angles of pronation/supination vary significantly between individuals, and therefore should be compared to the opposite joint. Traumatic luxations can be associated with elongation rather than rupture of the collateral ligaments and carries a relatively good prognosis.

Last, following either closed or open reduction the elbow should be stabilized via external coaptation (Spica splint) for 3 weeks. This is done to keep the anconeal process engaged with the olecranon fossa and prevent recurrence of luxation. Following splint removal, exercise restriction should be strictly enforced for at least 4-6 weeks. Passive ROM exercises can be used to maintain/regain ROM.

Prolonged joint immobilization (3+ weeks) decreases synovial fluid production, cartilage stiffness and thickness. It also leads to loss of muscle mass, decreased bone density and osteoarthritis. For these reasons flexible external fixation has been proposed as an alternative to external coaptation.

Question 43

A five-year-old female neutered Border Collie presents to your clinic 24 hours after a road traffic accident. She is non-weight-bearing on the left forelimb but otherwise well. Radiographs of this limb demonstrate a lateral luxation of the antebrachium relative to the humerus.

d) Closed reduction is unsuccessful in this case. Briefly describe the surgical approach to the elbow that would permit open reduction of this luxation. Do not discuss surgical fixation. (4 marks)

Answer 43

Open reduction is indicated in cases of avulsion fracture of the attachments of the medial collateral ligament, articular fractures, intra-articular interposition of tissues, marked instability/reluxation following closed reduction and chronic luxations. Salvage procedures may be considered for cases of severely degenerative joints or irreducible chronic luxations.

Caudolateral approach to the elbow: A skin incision is performed from the distal third of the humerus to the proximal third of the ulna, cranial to the olecranon. The incision is positioned so that it DOES NOT overlay the tuber olecranon after closure, as this may result in incisional complications. The lateral humeral epicondyle may be difficult to palpate due to lateral displacement of the radial head. A myotomy of the anconeal muscle is performed if the muscle hasn’t been lacerated during the luxation, but hemorrhage can be minimized if the muscle can be subperiosteally elevated from the olecranon. The articular surfaces are inspected and the anconeal process is repositioned within the olecranon fossa following a similar maneuver described for closed reduction.

Question 44

A five-year-old female neutered Border Collie presents to your clinic 24 hours after a road traffic accident. She is non-weight-bearing on the left forelimb but otherwise well. Radiographs of this limb demonstrate a lateral luxation of the antebrachium relative to the humerus.

e) List four (4) potential long-term complications of chronic elbow luxation.
(2 marks)

Answer 44

• Chondromalacia
• Articular cartilage loss
• Loss of range of motion due to periarticular fibrosis
• Secondary DJD

Question 45

A five-year-old female neutered Border Collie presents to your clinic 24 hours after a road traffic accident. She is non-weight-bearing on the left forelimb but otherwise well. Radiographs of this limb demonstrate a lateral luxation of the antebrachium relative to the humerus.

f) Briefly describe how the anatomical features of the feline elbow and distal humerus differ from the canine elbow and distal humerus. (2 marks)

Answer 45

In the dog the median nerve and associated branch of the brachial artery are located beneath the pronator teres muscle on the craniomedial aspect of the joint. In the cat these structures run through the supratrochlear foramen. The dog also does not have a radial fossa (also called coronoid fossa) on the cranial aspect of the olecranon fossa, and the supratrochlear foramen may be absent when the humerus is small.

Question 46

4. A two-year-old female toy poodle presents to you with a two-week history of neck pain with moderate ataxia and paresis affecting all four limbs.
   a) Contrast the expected neurological examination findings for a spinal cord lesion that localizes to C1-C5 with findings expected for a C6-T2 spinal cord lesion.

Answer 46

• C1-C5: UMN deficits on thoracic and pelvic limbs (normal or exaggerated spinal reflexes); normal withdrawal reflexes;
• Normal to increased muscle tone.
• Cervical pain, spasms, rigidity.
• Muscle atrophy may develop in chronic cases.
• May be associated with UMN bladder (turgid and difficult to express),
• Maybe respiratory difficulty (phrenic and intercostal nerve dysfunction)
• Maybe Horner’s syndrome (1^st order sympathetic neurons)
• C6-T2: classically LMN deficits on thoracic limbs and UMN signs on pelvic limbs, but more likely with moderate to severe compressive lesions.
• May present only with pelvic limb weakness because ascending UMN tracts for the pelvic limbs are more peripherally located than the centrally located LMN cell bodies in the ventral horn of the gray matter. This is usually the case for compressive lesions such as IVDD.
• The presence of cervical pain/rigidity will further support C6-T2 over T3-L3 myelopathy.
• Occasionally only one thoracic limb may be affected (monoparesis/monoplegia).
• Decreased withdrawal reflexes on thoracic limb/limbs (ipsilateral to lesion)
• Normal to exaggerated myotatic and withdrawal reflexes in pelvic limbs
• Early denervation atrophy of the thoracic limbs and late onset disuse atrophy in pelvic limbs.
• Possible route signature
• Decreased to absent cutaneous trunci
• Possible UMN bladder
• Possible respiratory difficulty due to LMN dysfunction to phrenic nerve and UMN to intercostal nerves
• Possible Horner’s syndrome (1^st order sympathetic neurons)

Question 47

4. A two-year-old female toy poodle presents to you with a two-week history of neck pain with moderate ataxia and paresis affecting all four limbs.
   b) List six (6) differential diagnoses that could account for a C1-C5 lesion in this case. (3 marks)

Answer 47

• Intervertebral Disk Disease (IVDD, likely chondroid, Type I)
• Atlanto-Axial Instability (AA Instability)
• Steroid-Responsive Meningitis-Arteritis (SRMA)
• Acute non-compressive Nucleus Pulposus Extrusion (ANNPE)
• Hydrated Nucleus Pulposus Extrusion (HNPE)
• Fibrocartilaginous Embolism (FCE)

Question 48

4. A two-year-old female toy poodle presents to you with a two-week history of neck pain with moderate ataxia and paresis affecting all four limbs.
   c) Radiography, computerized tomography (CT), and magnetic resonance imaging (MRI) are frequently used to image the canine spine when a myelopathy is suspected. Discuss the relative strengths and weaknesses of each of these modalities for imaging the spine. (9 marks)

Answer 48

• Radiography:

Advantages: - Readily available

• Inexpensive, sensitive for fractures and luxations
• Sensitive for discospondylitis, bony abnormalities and malformations
• Ability to obtain dynamic images

Disadvantages: - Unable to visualize nervous system directly

• Poor soft tissue resolution
• Very limited information about brain and spinal cord
• Computed Tomography:

Advantages:

• Excellent bone detail (fractures, luxations, neoplasia, malformation)
• Excellent for visualizing hemorrhage
• Less expensive that MRI
• Faster image acquisition than MRI – often able to obtain images under sedation

Disadvantages:

• Less soft tissue contrast, especially at the cerebellum/brainstem due to bony artifacts
• Unable to obtain multiple image planes, but able to generate computer 3D reconstruction
• MRI:

Advantages:

• Excellent soft tissue resolution (Modality of choice for intracranial and spinal neoplasia, encephalitis, myelitis, infarction and syringomyelia)
• Able to obtain imagen in all three body planes without moving the patient
• No ionizing radiation

Disadvantages:

• More expensive that CT
• More time consuming – studies take longer and require general anesthesia
• Mobile metal implants cannot be close to field of view due to metal artifact or potential implant movement
• Cannot be used if patient has a pacemaker or another battery-powered device (i.e. vagal nerve stimulator)
• Dynamic studies are possible but more difficult to obtain than with radiography/myelography

Question 49

4. A two-year-old female toy poodle presents to you with a two-week history of neck pain with moderate ataxia and paresis affecting all four limbs.
   d) Describe the typical radiographic findings encountered with an atlanto-axial subluxation. (3 marks)

Answer 49

AA subluxation is classically represented by an increased distance between the spine of the Axis (C2) and the dorsal arch of the Atlas (C1).

Question 50

4. A two-year-old female toy poodle presents to you with a two-week history of neck pain with moderate ataxia and paresis affecting all four limbs.
   e) List the primary stabilizers of the atlanto-axial joint. (3 marks)

Answer 50

The AA joint is primarily stabilized by the ligaments of the dens of the Axis. These are the apical ligament, alar ligaments (2) and transverse ligament.

Question 51

4. A two-year-old female toy poodle presents to you with a two-week history of neck pain with moderate ataxia and paresis affecting all four limbs.
   f) Discuss conservative management of atlanto-axial subluxation. Briefly describe when conservative management is indicated. (6 marks)

Answer 51

• Indicated in young patients with mild to moderate clinical signs
• Patients that have not reached skeletal maturity. Typically small and toy breeds with small and soft vertebrae, which increases the difficulty associated with implant placement and the risk of implant failure
• Treatment based on the use of rigid neck brace for 8 weeks, restricted activity and analgesics.