ANZCVS 2013

Question 1

1. Linear external fixators can be used to stabilize comminuted mid-shaft long-bone fractures.
   a) Name the type of bone healing that occurs in the above scenario (2 marks) and briefly describe the sequence of events that occurs with this type of bone healing from injury to one year post fracture repair. (8 marks)

Answer 1

Secondary bone healing: The healing process from injury to complete union can be divided into 5 partially overlapping phases: Inflammation, Intramembranous ossification, Chondrogenesis (soft callus), Osteochondral ossification (hard callus) and Remodeling.

• Inflammation: Begins immediately after injury with the formation of a platelet clot and degranulation of activated platelets, which release cytokines and growth factors to attract neutrophils (24 hours), macrophages (48 hours, via diapedesis of monocytes) and lymphocytes. Arachidonic acid from membrane phospholipids is converted into prostanoids and thromboxans via COX, leading to vasodilation and further platelet activation. Fibroblast and platelet-derived growth factors activate progenitor mesenchymal cells from periosteum and soft tissue origin. These cells differentiate into osteoprogenitor cells, as well as provide anabolic factors to stimulate the healing process and modulate inflammation. Macrophages release chemotactic factors that recruit and activate fibroblasts, which begin to lay a fibrin meshwork to form a cell, growth-factor and matrix-rich meshwork. The “scaffold” will be quickly permeated by blood vessels and remodeled into granulation tissue, known as the “external callus”
• Intramembranous ossification: Osteoprogenitor cells derived from the periosteum begin to lay new bone between the periosteum and the cortex, for partial “ramps” on both ends of the fracture. The new bone does not cross the external callus.
• Chondrogenesis: starts with the development of granulation tissue during the inflammatory phase, which is quickly remodeled into fibrovascular tissue and finally into fibrocartilage by the production of collagen type I and III over several weeks. Local conditions (low O2 pressure, growth factors) stimulate local stem cells to differentiate into chondrocytes. These will produce extra-cellular matrix rich in collagen Type II, known as “soft callus”
• Osteochondral ossification: The cartilage callus (soft callus) produced during the previous phase is still insufficient to reduce strain enough to allow survival of osteoblasts. Chondrocytes undergo hypertrophy and begin to mineralize the extracellular matrix, downregulating the production of collagen Type II and stimulating the production of collagen Type X (marker of osteochondral ossification). Upregulation of MMP’s will degrade collagen II as it is replaced by bone. Mineralized cartilage finally possesses enough stiffness to support osteoblast/osteocyte survival. These cells proliferate from the periphery of the callus (previous zone of intramembranous ossification) towards the center, laying woven bone. Radiographically this callus looks large and misshapen.
• Remodeling: The woven bone callus formed during the previous phase is not as strong as lamellar bone, and is thus gradually replaced. Osteoclasts and osteoblasts work as Bone Multicellular units (BMU) to replace woven bone with lamellar bone known and osteons. Osteons are composed of concentric layers of bone bound by cement lines and possessing a central Harversian canal containing blood vessels. Remodeling can continue for years and follows Wolff’s law.

Question 2

2. b) Discuss advantages and disadvantages of an external fixator that has been applied in a closed manner compared to open reduction and stabilization by a dynamic compression plate applied as a buttress/bridging plate. (8 marks)

Answer 2

External fixators applied in a closed manner (Closed reduction)

Advantages (biological fixation)

• Minimal disruption of the fibrin clot/granulation tissue and mesenchymal stem cells therein contained
• Minimal disruption of the endosteal, periosteal and soft tissue blood supply
• Minimal to no exposure of the fracture to biological contaminants such as cutaneous bacterial flora
• Minimal soft tissue trauma.

Disadvantages

• Inability to more closely restore the anatomical structure of the bone (understanding that true anatomical reduction is not possible in this case)
• Less stiffness, leading to higher strain at the fracture site which may delay healing and predispose the site to nonunion. (This is highly influenced by the type of fixator utilized)

Open reduction with Dynamic Compression plate applied in buttress/bridging mode

Advantages

• Allow more adequate reconstruction of bone fragments and realignment of the anatomical axis of the bone in comparison to ExFix applied in closed fashion
• The implant is positioned close to the mechanical axis of the bone, making it superior to ExFix in its ability to counteract biomechanical forces.
• Implant stiffness is typically greater than what can be achieved with ExFix, leading to lower strain and faster rate of fracture union.

Disadvantages

• Application disrupts the fracture site and early fibrovascular callus, potentially delaying healing.
• Disrupts periosteal and soft tissue blood supply
• Exposes the fracture and implants to pathogens (open surgical wound)
• The required approach predisposes the patient to iatrogenic damage to anatomical structures (vessels, nerves, muscles).

Question 3

3. c) Name four (4) categories of linear external fixator frame configurations and draw a diagram for each to illustrate the construct. (4 marks)

Answer 3

A, Type Ia, (unilateral uniplanar).
B, Type Ib (unilateral biplanar)
C, Type I-II hybrid (unilateral uniplanar combined with a bilateral uniplanar and a diagonal connecting bar).
D, Type II modified (bilateral uniplanar with combined full and half pins)
E, Type II (bilateral uniplanar with all full pins)
F, Type III modified (bilateral biplanar). Note the addition of the diagonal augmenting the type I-II hybrid frame (C) and the proximal and distal articulations placed between the cranial and medial connecting bars of the type III frame (F, right image).”

Question 4

4. d) List strategies to increase the strength and stiffness of an external fixator frame.

Answer 4

• Pre-drill before inserting positive-profile pins
• Increase pin numbers (up to 4 pins per bone segment)
• Increase pin size (up to 25% bone diameter)
• Place pins near the joints and near the fractures
• Decrease the distance between the bone and the pin/clamp interface
• Increase the diameter of the connecting bar or use double bars/augmentation plates
• Increase the number and planes of connecting bars
• Tie the intramedullary pin into the fixator frame

Question 5

1. a) Compare the pathophysiology of Hansen type I intervertebral disc disease with that of Hansen type II intervertebral disc disease.

Answer 5

Hansen Type I: The nucleus pulposus undergoes progressive loss of proteoglycans, becoming dehydrated and mineralized (chondroid degeneration). This leads to loss of ability to distribute pressure and causes secondary degeneration and rupture of the annulus fibrosus. This usually culminates in the expelling of nucleus contents towards the dorsally located spinal cord (thinnest part of the annulus) during an episode of mechanical stress. This is know as Intervertebral Disk Extrusion. The resulting injury leads to various degrees of contusion and compression.

Hansen Type II: The nucleus pulposus becomes progressively more dehydrated and is gradually replaced by fibroid tissue. This causes a gradual transfer of stress to the annulus, which eventually degenerates over a period of months to years. The degeneration typically leads to dorsal protrusion of disk material and compression of the spinal cord.
The clinical signs associated with these conditions can be similar since both cause various degrees of spinal cord compression. The main differences pertain to the acuteness and severity of the resulting clinical syndrome. Type I is typically associated with acute or peracute clinical signs caused by severe contusion or even laceration of the Dura Mater and spinal cord in severe cases. Type II usually leads to more insidious clinical signs secondary to inflammatory changes at the site of compression. Signalment is also different between Type I and II.

Question 6

3. c) You have examined the urinary bladder of a dog with an acute thoraco-lumbar intervertebral disc extrusion and a dog with a chronic severe lumbosacral compression. For each case listed above describe: (8 marks)
   - the neurological classification of bladder dysfunction

Answer 6

Urinary bladder disfunction is classified as Upper Motor Neuron (UMN) or Lower Motor Neuron (LMN).

Question 7

3. c) You have examined the urinary bladder of a dog with an acute thoraco-lumbar intervertebral disc extrusion and a dog with a chronic severe lumbosacral compression. For each case listed above describe: (8 marks)
   - the neuroanatomic localization of the lesion

Answer 7

UMN bladder is expected with lesions between the pons and L7 spinal segment, such as in the case of the dog with thoraco-lumbar IVDE

LMN Bladder is expected with lesions caudal to and including sacral spinal segment, such as in the case of the dog with DLSS, as well as with pelvic/lumbosacral plexus lesions

Question 8

3. c) You have examined the urinary bladder of a dog with an acute thoraco-lumbar intervertebral disc extrusion and a dog with a chronic severe lumbosacral compression. For each case listed above describe: (8 marks)
   - the expected clinical examination findings pertaining to the bladder

Answer 8

UMN bladder is full, turgid and difficult to express

LMN bladder is full, flaccid and easy to express.

Question 9

3. c) You have examined the urinary bladder of a dog with an acute thoraco-lumbar intervertebral disc extrusion and a dog with a chronic severe lumbosacral compression. For each case listed above describe: (8 marks)
   - how these abnormalities affect control of micturition.

Answer 9

Patients with UMN bladder have excessive urethral musculature tone, and are either completely unable to urinate of have difficulty accomplishing bladder emptying.

Patients with LMN bladder lack detrusor reflex and have reduced urethral muscular tone. They typically dribble urine constantly, and it is difficult to confirm bladder emptying via transabdominal palpation due to overt bladder flaccidity.

Question 10

a) Draw and label a diagram of the normal microscopic layers of articular cartilage in a mature dog. (6 marks)

Answer 10

Superficial zone
Transitional zone
Deep zone
Tidemark
Zone of ossified cartilage

Question 11

b) Define osteochondrosis and osteochondritis dissecans. (2 marks)

Answer 11

Osteochondrosis is a syndrome characterized by failure of endochondral ossification, leading to cartilage retention.
Osteochondritis dissecans is the clinical syndrome caused by dislodgment of a cartilage flap due to osteochondrosis.

Question 12

c) Describe the pathophysiology of osteochondritis dissecans in a dog. (12 marks)

Answer 12

OCD begins with failure of osteochondral ossification at either the level of the physis or the articular epiphyseal complex responsible for epiphyseal bone growth. The cause of this failure is not well understood, and proposed etiologies include a combination of management, nutritional and genetic factors. The unossified cartilage becomes progressively thicker (osteochondrosis) and eventually outgrowths its nourishment sources (synovial fluid and subchondral bone). This end result is chondrocyte necrosis and loss of cartilage viability, leading to the formation of clefts between the deep zone and the zone of ossified cartilage. Normal activity eventually leads to the formation of vertical fissures in the cartilage, which communicate with the horizontal clefts to form flaps. This communication exposes the synovial fluid to cartilage fragments and inflammatory mediators, inducing joint inflammation which eventually leads to DJD.

Question 13

d) List four (4) recognised risk factors for development of osteochondritis dissecans in the dog. (4 marks)

Answer 13

• Age (4 to 8 months of age)
• Gender (Males)
• Breed (Large and Giant breeds)
• Rapid Growth
• Nutrient Excess

Question 14

e) List three (3) joints in which osteochondritis dissecans lesions occur in the dog. Identify the specific anatomic location most commonly affected within those joints. (6 marks)

Answer 14

• Shoulder – Caudal aspect of the humeral head
• Elbow – distal aspect of the medial humeral condyle
• Stifle – distal aspect of medial or lateral femoral condyles
• Tarsus – medial or lateral trochlear ridges

Question 15

1. a) Describe, with the aid of diagrams, the normal anatomy of the canine diaphragm. Include in your answer the muscular divisions and their attachments and the spatial relationship of the diaphragm to adjacent organs. (11 marks)

Answer 15

The diaphragm is a musculotendinous plate located between the thoracic and abdominal cavities. It is composed of a central tendinous region surrounded on all sides by muscles that stream in a radial pattern to attach to various arear of the thoracic ad abdominal walls. This muscular region is divided into Lumbar part, Costal part (on each side) and Sternal part. The diaphragm is convex on the thoracic side and concave on the abdominal side.
The central tendon occupies 21% of the canine diaphragm and consists of a triangular central area with dorsal extensions on each side. It contains the foramen of the caudal vena cava, located to the right of the midline as viewed from the abdominal surface.
The Lumbar part is formed by the right and left diaphragmatic crura which surround the aortic hiatus. The hiatus contains the aorta, azygous vein, hemiazygous vein and thoracic duct. The right crus is much larger than the left. They arise from a long bifurcate tendon located medial to the psoas minor muscle. The long part of this tendon arises from the cranial aspect of the body of L4 and the shorter part from the body of L3. The muscle fibers that arise from the lateral aspects of this tendon parallel the dorsal thoracic wall and extend ventral to the psoas muscles to form the lumbocostal arch. After crossing the lumbar musculature the fibers coalesce with those of the costal parts. Seen from the abdominal cavity, each crus is a triangular muscle plate that give rise to tendinous portions. The sympathetic trunk and splanchnic nerves cross dorsal to the lumbocostal arch. The musculature of the medial portion of the right crus is the thickest (5 to 6 mm) and originates from the terminal portion of the right column of the aortic hiatus. It extends ventrally to surround the esophageal hiatus and blends ventrally with the central tendon.
The costal part is composed of muscle fibers originating from the eighth (ventral portion) to the thirteenth ribs (dorsal part) which irradiate centrally to blend with the central tendon.
The sternal part may not exist in the dog. It is an unpaired medial part that originates on the base of the xiphoid cartilage and extends dorsally to blend with the central tendon.
The convex thoracic side of the diaphragm is lined with fascia endothoracica and pleura. It lies against the surface of the lungs. On the dorsal part of the mediastinum the aorta, azygous vein, hemiazygous vein and thoracic duct cross through the aortic hiatus. The esophagus passes through the esophageal hiatus together with the dorsal and ventral vagal nerve trunks. The caudal vena cava and right phrenic nerve reach the diaphragm in the plica vena cava and cross through the foramen of the caudal vena cava. The stomach and liver attach to the concave peritoneal surface via ligaments.

Question 16

2. b) Name the nerve that provides motor supply to the diaphragm. (1 mark)

Answer 16

Phrenic nerve (C5,6,7)

Question 17

3. c) Name the abdominal organ that is most commonly displaced into the thoracic cavity in cases of traumatic diaphragmatic rupture in small animals. (1 mark)

Answer 17

Liver (88% cases)

Question 18

4. d) Describe the pathophysiological processes that occur as sequelae to traumatic diaphragmatic hernia in the following body systems:

Respiratory system

Answer 18

Dyspnea is the most common clinical sign associates with diaphragmatic hernias. Parietal pleural contact with the lungs is typically maintained by negative intrapleural pressure of 0.5 to 1 mm Hg. Diaphragmatic rupture leads to loss of contact and equalization between pleural and peritoneal pressure, forcing the abdominal and thoracic muscles to take over the function of the diaphragm. Herniated abdominal organs compress the lungs, which become atelectatic and lead to hypoventilation, ventilation-perfusion mismatch and hypoxia.

Question 19

4. d) Describe the pathophysiological processes that occur as sequelae to traumatic diaphragmatic hernia in the following body systems:

Cardiovascular

Answer 19

Cardiac dysrhythmias, particularly ventricular tachycardia, occur in 12 % of patients. This decreases tissue perfusion and aggravates shock (present in most patients with acute traumatic hernias).

Question 20

4. d) Describe the pathophysiological processes that occur as sequelae to traumatic diaphragmatic hernia in the following body systems:

Gastrointestinal and hepatic systems

Answer 20

Herniation and incarceration of stomach and intestines quickly leads to obstruction of the flow of ingesta as well as venous return. Gastric tympany develops and leads to compression of the caudal vena cava and lungs, which may prove rapidly fatal. Vascular compression can lead to ischemic necrosis, intestinal perforation and abscessation. Gastric dilatation-volvulus may develop, including in cats, leading to severe perfusion impairment and possible gastric wall necrosis. Less severe diaphragmatic hernias involving the GI tract may lead to gastric outflow and proximal duodenal obstruction, leading to dehydration, vomiting, metabolic alkalosis, electrolyte derangements, cardiac arrhythmias and weakness.

Liver herniation leads to hepatic venous stasis, hepatic necrosis, biliary tract obstruction and icterus. Bacteria quickly proliferates in hypoxemic hepatic tissue, and systemic release of toxins after repositioning of liver lobes may lead to septic shock. Pleural effusion occurs because of hepatic venous or caudal vena caval compression, leading to extravasation of large quantities of hepatic lymph through the liver capsule. This fluid may accumulate, depending on the location of the hernia, as pleural effusion, pericardial fluid and/or ascites. This occurs in approximately 30 % of cases and may lead to cardiac tamponade and cardiogenic shock. Biliary tract injury leads to severe bile peritonitis and pleuritis.

Question 21

1. A one-year-old, male neutered cat presents to you having been hit by a car. Pelvic radiographs identify a right-sided sacro-iliac fracture/luxation, and a left-sided central acetabular fracture. You cannot identify a bladder silhouette on the radiographs.
2. a) List any additional diagnostic tests you would recommend for this patient, and justify your selection. (10 marks)

Answer 21

Thoracic radiography: Over 50% of cats who suffered vehicular trauma will sustain concomitant thoracic trauma. This may involve pulmonary contusions, hemothorax, cardiac dysrhythmias and fractures.

Point-of-care abdominal ultrasonography (FAST): Readily available, fast, non-invasive diagnostic modality that may identify the presence of abdominal effusion. If identified, effusion can be accurately sampled (abdominocentesis) to determine if compatible with urine (urinary bladder rupture), blood (splenic, hepatic, mesenteric or other vascular trauma) or feces (bowel perforation – less common). Does not require general anesthesia.

Computed Tomography: The “gold standard” for trauma patients for its ability to accurately identify effusion and create 3D reconstructions of fracture sites. This is particularly important in the case of an articular fracture. Also excellent to detect evidence of thoracic trauma. The scans are fast and progressively more available at trauma centers. Can often be performed with minimal sedation.

Complete Blood Count, Biochemistry, Urinalysis, Blood Gas Analysis and electrocardiogram: Patients who suffered vehicular trauma are frequently in shock, and may present with various metabolic abnormalities. These may include hypovolemia (internal or external hemorrhage), coagulopathies (DIC), azotemia/uremia/metabolic acidosis (urinary bladder rupture), electrolyte abnormalities and cardiac dysrhythmias ( both due to hyperkalemia)

Abdominal fluid analysis: peritoneal fluid creatinine concentration equal or greater than 2x that of blood is diagnostic for urinary tract rupture.

Cystography: more commonly performed in dogs, and typically using organic iodinated contrast media. May help identify ruptures in various areas of the urinary tract.

Question 22

1. A one-year-old, male neutered cat presents to you having been hit by a car. Pelvic radiographs identify a right-sided sacro-iliac fracture/luxation, and a left-sided central acetabular fracture. You cannot identify a bladder silhouette on the radiographs.

Name the major peripheral nerve that is most commonly injured with pelvic fractures. Explain how to evaluate the function of this nerve with a physical examination. (3 marks)

Answer 22

The lumbosacral trunk is most commonly affected, and in particular the sciatic nerve. The integrity of this nerve can be accessed via the combined testing of the patellar, gastrocnemius cranial tibial and withdrawal reflexes. Patients with sciatic nerve injury will have hypereflexive patellar reflex (pseudohypereflexia), hyporeflexive gastrocnemius (tibial nerve) and cranial tibial reflex (common peroneal nerve) and a partial withdrawal reflex (able to flex the hip and stifle but unable to flex the hock).

Question 23

1. A one-year-old, male neutered cat presents to you having been hit by a car. Pelvic radiographs identify a right-sided sacro-iliac fracture/luxation, and a left-sided central acetabular fracture. You cannot identify a bladder silhouette on the radiographs.

List the indications for surgical stabilization of pelvic fractures in cats.

Answer 23

• Severe SI luxation – particularly if bilateral
• More than 50% pelvic canal narrowing
• Neurologic impairment
• Intractable pain
• Ipsilateral SI luxation and pelvic fracture
• Bilateral fractures/SI luxation necessitating early weight-bearing

Question 24

1. A one-year-old, male neutered cat presents to you having been hit by a car. Pelvic radiographs identify a right-sided sacro-iliac fracture/luxation, and a left-sided central acetabular fracture. You cannot identify a bladder silhouette on the radiographs.
   d) Briefly discuss the principles of screw fixation of sacroiliac fracture/luxation that minimise surgical complications. (5 marks )

Answer 24

Adequate exposure: Direct visualization of the lateral surface of the sacral wing is necessary for proper screw positioning. This is attained by elevating the middle gluteal muscle from the lateral aspect of the ilium and the sacrospinalis muscle from the medial ridge of the ilial crest. A Hohmann retractor is placed between the ilium and the ventral bony shelve of the sacrum, effectively displacing the ilium ventrally and exposing the sacral wing.

Accurate implant placement: The above-mentioned exposure allows the drilling of a threaded hole (tapped after drilling) 2mm cranial and 2 mm proximal to the center of the crescent-shaped articular cartilage. The depth of the hole must be such that the screw tip extends a minimum of 60% the distance across the sacral body. The glide hole in the ilium is determined by palpation of the articular prominence on the medial surface of the ilial wing. The ilium is then brought caudally in alignment with the articular surface of the sacroiliac joint. The screw is visually guided through the slide hole and into the threaded hole and tightened. A second screw is placed immediately dorsal and cranial to the first if space permits. This screw must be shorter to avoid the spinal canal. Placement of a transiliac bolt may be advisable in large or overweight dogs.

Imaging: Intraoperative imaging (fluoroscopy or radiographs) are not indispensable by helpful to determine if implants have been properly positioned and are adequately sized. At a minimum post-op rads must be obtained and implant position/size immediately corrected if needed.

Question 25

1. A one-year-old, male neutered cat presents to you having been hit by a car. Pelvic radiographs identify a right-sided sacro-iliac fracture/luxation, and a left-sided central acetabular fracture. You cannot identify a bladder silhouette on the radiographs.
   e) List the principles of articular fracture repair. (2 marks)

Answer 25

• Anatomical reconstruction

* Rigid stabilization

Question 26

1. A one-year-old, male neutered cat presents to you having been hit by a car. Pelvic radiographs identify a right-sided sacro-iliac fracture/luxation, and a left-sided central acetabular fracture. You cannot identify a bladder silhouette on the radiographs.
   f) Briefly describe key steps in the surgical approach to provide adequate exposure for the acetabular fracture (4 marks) and the technique you would use for stabilization. (2 marks)

Answer 26

Approach to the acetabulum: Skin incision centered over the cranial border of the greater trochanter, following the cranial border of the femur. Incise the deep leaf of the fascia lata, carrying the incision proximally through the insertion of the tensor fascia lata muscle at the greater trochanter and along the cranial border of the superficial gluteal muscle. Extend the incision distantly through the fascia communicating the tensor fascia lata and the biceps femoris. Incise through the insertion of the superficial gluteal muscle at the third trochanter, reflect the muscle proximately and the biceps femoris caudally to expose the sciatic nerve. Perform an osteotomy of the greater trochanter, positioning the osteotome just proximal to the insertion of the superficial gluteal muscle at the third trochanter. Make sure to angle the osteotome 45° to the long access of the femur to remove the trochanter with the insertion of the deep and superficial gluteal muscles. Reflect the gluteal muscles and the greater trochanter from the joint capsule. Observe the insertion of the gemellus muscle and the tendon of the internal operator, replacing a suture through the two insertions near the trochanteric fossa. Incise both structures together at the fossa, elevating the gemellus muscle from the caudo-lateral surface of the acetabulum with a periosteal elevator. Use the sutures to retract the muscle proximally and caudally. Exposure of the tuber ischium and placement of a bone holding forceps can greatly facilitate the control over the caudal fragment during fracture reduction. Make sure to incise the joint capsule to allow visual confirmation of anatomic reconstruction prior/during/after plating.

Stabilization: Ideally performed with pre-contoured locking dorsal acetabular plates. Please at least two screws on the caudal fragment and three on the cranial fragment. Certain reconstruction plates can be contoured using specially designed contouring pliers in two axis to accurately fit the dorsal aspect of the acetabulum. If available, the plate can be pre-contoured using a similarly-sized bone model prior to surgery. If iliac fractures are also present a two-plate stabilization can be employed: a DCP plate for the iliac body and acetabular plate for the acetabulum. Alternatively, a long, contourable reconstruction plate can span the entire hemipelvis. Comminuted acetabular fractures may require reconstruction with lag screws, followed by dorsal plate augmentation.

Question 27

2. A nine-year-old entire male rottweiler presents for straining to urinate and defecate. On examination a large left-sided perineal swelling is observed, and a perineal hernia is suspected. The hernia is to be repaired using an internal obturator muscle flap.
   Answer all of the following:

List key anatomical structures used in the repair. (5 marks)

Answer 27

• External anal sphincter
• Levator Ani (often atrophied) / coccigeus muscles
• Internal obturator muscle
• Internal Pudendal A./V./N. (Dorsal surface of the Internal Obturator M)
• Caudal Rectal N. (Within the ischiorectal fossa – branch of pudendal N., primary somatic motor to ext. anal sphincter)
• Sacrotuberous ligament (dogs only, Tuber ischum to sacrum and Cd1)

Question 28

2. A nine-year-old entire male rottweiler presents for straining to urinate and defecate. On examination a large left-sided perineal swelling is observed, and a perineal hernia is suspected. The hernia is to be repaired using an internal obturator muscle flap.
   Answer all of the following

ii. Briefly describe the surgical technique for the internal obturator muscle flap. (5 marks)

Answer 28

The hernia is identified, dissected and reduced. External anal sphincter, Levator ani, coccigeus and internal obturator muscles are identified. Internal pudendal A./V./N. are located on the caudolateral aspect of the dorsal surface of the Internal Obturator M and preserved. The Internal Obturator muscle fascia is incise along the caudolateral border and elevated off the dorsal surface of the Ilium using periostea elevators. This should include the periosteum to improve suture-holding power. The tendon of insertion of the Internal Obturator can also be identified running over the dorsal border of the ischium to insert onto the trochanteric fossa. This tendon can be transected to improve flap freedom, but this must be done medial to the dorsal border of the ischum to avoid damage to the sciatic nerve. Muscle elevation must not extend farther cranially than the caudal border of the obturator foramen to avoid damage to the obturator N./A. The Internal Obturator is then transposed dorsal and medially to enhance the hernial closure using the External Anal Sphincter, Levator Ani and Coccygeus muscles. As with a traditional repair, sutures are pre-placed in a triangulating pattern between these muscles prior to closure. Suture material is 2-0 or 0 synthetic, monofilament, long-term absorbable or non-absorbable material.

Question 29

2. A nine-year-old entire male rottweiler presents for straining to urinate and defecate. On examination a large left-sided perineal swelling is observed, and a perineal hernia is suspected. The hernia is to be repaired using an internal obturator muscle flap.
   Answer all of the following

iii. Name one (1) abdominal surgical technique that could be performed in this case in addition to the internal obturator muscle flap to address the cause of the stranguria. (1 mark)

Answer 29

Cystopexy and/or Castration / deferensopexy

Question 30

2. A nine-year-old entire male rottweiler presents for straining to urinate and defecate. On examination a large left-sided perineal swelling is observed, and a perineal hernia is suspected. The hernia is to be repaired using an internal obturator muscle flap.
   Answer all of the following

iv. Explain why the internal obturator muscle flap technique is superior to anatomical reconstructive techniques. (1 mark)

Answer 30

The muscles of the pelvic diaphragm are frequently atrophied at the time of herniorrhaphy. The Internal Obturator offers a robust and vascular myocardial graft that reduces tension and external anal sphincter distortion. Brings additional blood supply to the area.

Question 31

2. A nine-year-old entire male rottweiler presents for straining to urinate and defecate. On examination a large left-sided perineal swelling is observed, and a perineal hernia is suspected. The hernia is to be repaired using an internal obturator muscle flap.
   Answer all of the following

f) Name two (2) peripheral nerves that have the potential to be damaged during dissection or suture placement. (2 marks)

Answer 31

• Pudendal nerve
• Caudal Rectal Nerve
• Sciatic Nerve

Question 32

2. A nine-year-old entire male rottweiler presents for straining to urinate and defecate. On examination a large left-sided perineal swelling is observed, and a perineal hernia is suspected. The hernia is to be repaired using an internal obturator muscle flap.
   Answer all of the following

g) If the internal obturator muscle flap technique is not successful state two (2) alternative techniques that can be used. (4 marks)

Answer 32

• Superficial Gluteal Muscle transposition

* Semitendinosus Muscle transposition

Question 33

2. A nine-year-old entire male rottweiler presents for straining to urinate and defecate. On examination a large left-sided perineal swelling is observed, and a perineal hernia is suspected. The hernia is to be repaired using an internal obturator muscle flap.
   Answer all of the following

h) The patient develops a rectal prolapse the first day after surgery. Name one (1) procedure for initial management and one (1) procedure if the prolapse does not resolve. (2 marks)

Answer 33

• Initial management: loose anal purse string

* Long-term management if prolapse does not resolve: Colopexy or rectal resection

Question 34

1. a) List the four (4) specific conditions grouped under the heading of elbow dysplasia. (4 marks)

Answer 34

• Ununited Anconeal Process (UAP)
• Medial Compartment Disease (Fragmented Coronoid Process – FCP)
• Osteochondrosis / Osteochondritis Dissecans (OCD) – Usually affecting the trochlea.
• Elbow Incongruity

Question 35

2. b) Discuss the advantages and disadvantages of the following imaging modalities with regards to diagnosing elbow dysplasia: (10 marks) Radiology, arthroscopy, CT

Answer 35

i. radiography
• Advantages: Readily available, low cost, only requires sedation, sensitive for diagnosis of OCD; sensitive for diagnosis of UAP
• Disadvantages: Low sensitivity for Medial Compartment Disease; lower diagnostic accuracy as compared to CT

ii. arthroscopy
• Advantages: excellent visibility of articular surfaces; allows diagnosis and minimally-invasive treatment; assessment of joint congruence;
• Disadvantages: Requires general anesthesia; does not allow evaluation of subchondral bone;

iii. computed tomography
• Advantages: High sensitivity for Medial Compartment disease and incongruity; Fast – Often requiring only sedation; able to evaluate subchondral bone for sclerosis/cysts/fissure/fragmentation
• Disadvantages: Higher equipment/study cost; Still lacks standardized protocol; unable to evaluate cartilage

Question 36

3. c) Discuss the management options available for a 10-month-old rottweiler with elbow pain due to fragmented medial coronoid process of the ulna. Include the advantages and disadvantages of these treatment options. (16 marks)

Answer 36

Management options can be divided into symptom-alleviating modalities, both surgical and non-surgical, as well as disease-modifying treatments.

Surgical options include joint exploration and Medial Coronoid fragment removal via medial arthrotomy or arthroscopy (preferred method). Fragment removal and debridement of the subchondral bone (medial Coronoid) is believed to alleviate clinical signs, but is typically considered a palliative procedure. Partial Medial Coronoid Osteotomy may be performed to improve elbow congruence if positive radio-ulnar incongruence is visually confirmed (or previously via CT). A Biceps Ulnar Release can be performed with the intent of decreasing rotational radio-ulnar incongruity (considered benign but lacks supporting evidence of efficacy). The main disadvantages associated with the surgical approach to reduce symptoms include the need for general anesthesia, cost, possible complications and the ongoing lack of prospective clinical studies with objective measures of outcome to support specific treatment techniques.

Non-surgical management include weight management, physical therapy, anti-inflammatories (including NSAID’s and EPA-rich fatty acids), PGAG’s (Adequan), nutraceuticals (chondroitin sulfate, glucosamine) and intra-articular infusions of steroids and/or hyaluronic acid. PRP/Stem-cell may be helpful but supporting evidence still lacks. The main disadvantage of medical management is that it does not allow assessment of concomitant and contributing issues to FCP, such as elbow incongruence and concomitant OCD lesions.

Disease-Modifying treatments include osteotomy of the ulna (Dynamic Ulnar Osteotomy - DUO, Partial Abducting Ulnar Osteotomy – PAUL), osteotomy of the radius, osteotomy of the humerus, Unicompartmental Elbow and arthrodesis.

• Osteotomy of the Ulna: Divided into “static” and “dynamic” techniques, depending on whether or not the osteotomy is stabilized with implants. Stabilization may decrease complications but the inability to accurately quantify and execute a precise amount of lengthening/shortening poses a significant limitation to this option. Dynamic techniques like the Distal Dynamic Ulnar Osteotomy (DDUO) have shown promising results based on their ability to mitigate the development of radiographic signs of OA in comparison to untreated elbows in 4 month-old dogs (Vezzoni, 2014)
• Osteotomy of the Radius: Originally proposed by Slocum, but lacked a method to standardize the degree of radius lengthening or a way to accurately estimate the degree of incongruence. Current CT combined with the duplicate circle superimposition technique could supersede this limitation. The Canine Elbow Realignment Osteotomy (CERO) uses temporary spacers which could make it a practical procedure, but objective data is still lacking.
• Osteotomy of the humerus: Based on the principle of load shifting from the medial Coronoid to the radial head. Executed with a transversal mid-shaft humeral osteotomy stabilized with a custom stepped lateral humeral plate. Complication rate was originally high but decreased to 4.75% once better implants became available (4.0mm locking cortical screw on proximal segment)
• Canine Unicompartmental Elbow (CUE – Arthrex): Based on the application of a round polyethylene implant on the medial coronoid and a “figure of eight” cobalt chrome implant on the medial humeral condyle. The latter is slightly proud of the joint surface to reduce contact forced between the articular surfaces. Effective in 92% of cases (combined full and acceptable outcomes). Most complications associated with approach (Medial epicondyle osteotomy)
• Elbow arthrodesis: Alleviates discomfort but leads to significant functional deficits. Reserved for cases of severe medial and lateral compartment disease not amenable to CUE.

A 2008 systematic review and meta analysis of 400 papers (Evans, Conzemius Vet Comp Orth 2008) indicated the arthroscopy was superior to arthrotomy or medical management, but arthrotomy was not superior to medical therapy.

Question 37

3. A three-year-old west highland white terrier presents with a two-day history of restlessness, retching, excessive salivation and regurgitation. Plain survey thoracic radiographs reveal a mineral density opacity in the esophagus.
   a) At what single location in the oesophagus are bone foreign bodies most likely to be found? (1 mark)

Answer 37

Between the heart and the diaphragm

Question 38

3. A three-year-old west highland white terrier presents with a two-day history of restlessness, retching, excessive salivation and regurgitation. Plain survey thoracic radiographs reveal a mineral density opacity in the esophagus.
   b) List potential short-term complications of esophageal foreign bodies.

Answer 38

• Esophageal perforation
• Pneumomediastinum
• Pneumothorax
• Mediastinitis
• Pleuritis
• Pyothorax
• mediastinal abscessation
• bronchoesophageal, tracheoesophageal, or aortic esophageal fistulas
• Respiratory distress may also be associated with aspiration pneumonia or impingement of the foreign bodies on the upper airways.”

Question 39

3. A three-year-old west highland white terrier presents with a two-day history of restlessness, retching, excessive salivation and regurgitation. Plain survey thoracic radiographs reveal a mineral density opacity in the esophagus.
   c) What is the most commonly encountered major long-term complication?

Answer 39

Esophageal stricture

Question 40

3. A three-year-old west highland white terrier presents with a two-day history of restlessness, retching, excessive salivation and regurgitation. Plain survey thoracic radiographs reveal a mineral density opacity in the esophagus.
   d) List the appropriate anatomical location for a thoracotomy to remove an intrathoracic esophageal foreign body located:
   i. cranial to the heart base (2 marks)
   ii. at the level of the heart base (2 marks)
   iii. caudal to the heart base. (2 marks)

Answer 40

i. cranial to the heart base (2 marks)
Left 3rd to 4th intercostal space

ii. at the level of the heart base (2 marks)
Right 4th to 5th intercostal space

iii. caudal to the heart base. (2 marks)
Left 9th intercostal space

Question 41

3. A three-year-old west highland white terrier presents with a two-day history of restlessness, retching, excessive salivation and regurgitation. Plain survey thoracic radiographs reveal a mineral density opacity in the esophagus.
   e) Describe how an esophagotomy incision may be sutured, justifying your answer (5 marks). Explain why there is an increased risk of dehiscence in oesophageal surgery in comparison to intra-abdominal intestinal surgery

Answer 41

The mucosa and submucosa are closed as one layer of simple-interrupted sutures, with knots located within the esophageal lumen. The muscular and adventitia are closed as one layer using simple-interrupted sutures with extra luminal knots.

Question 42

3. A three-year-old west highland white terrier presents with a two-day history of restlessness, retching, excessive salivation and regurgitation. Plain survey thoracic radiographs reveal a mineral density opacity in the esophagus.
   f) Identify the appropriate location for a feeding tube to be placed in this patient. Justify your answer with reference to other possible options (2 marks). Explain one (1) technique for placement of the feeding tube. (8 marks)

Answer 42

Feeding tubes must be placed aboral to the site of disease/injury, within functional GI tract. In this case options include gastrostomy and enterostomy tubes. My choice would be a gastrostomy tube due to ease of placement, the ability to feed blenderized foods, availability of large bore tubes and the opportunity to begin oral feeding while the tube remains in place. Gastrostomy tubes can be placed transcutaneously via blind or endoscopic-guided approaches, flank or midline abdominal approaches.
For a flank incision gastrostomy tube placement, begin by placing the anesthetized patient in right lateral recumbent. The area immediately caudal to the last rib and ventral to the lumbar spine is clipped and aseptically prepared. Four quarter drapes are applied in standard fashion to create a sterile field. A non-sterile assistant introduces a rigid tube through the mouth until it can be palpated and grasped through the left flank. The tube is manipulated until centered at a spot 3 cm caudal to the last costal arch and 3 cm distal to the transverse process of L3. With the tube firmly held in place, perform an incision extending through skin, subcutaneous and musculature until the gastric serosa is exposed. Place a purse-string suture around the tube using 2-0 monofilament absorbable sutures and perform a stab incision with #11 blade into the gastric lumen. Make the incision large enough to accommodate the gastrostomy tube. Place a 20 to 24 Fr Foley catheter into the stomach and inflate the bulb. Place gentle traction on the purse-string sutures and withdraw the rigid stomach tube through the mouth. Snugly tie the purse string while applying gentle traction on the tube to assure contact between the bulb and the gastric mucosa. Apply four simple interrupted sutures using monofilament absorbable 2–0 sutures between the gastric wall and the body wall to firmly pexy the stomach. Suture the subcutaneous and skin around the tube, ouch the tube 2 cm into the stomach and secure it to the skin using a Chinese fingertrap pattern.