Thoracic wall

Question 1

According to Blondel 2021 in Vet Surg, was pre-operative ultrasound or CT/MRI associated with a higher rate of subcutaneous migrating foreign body detection? Was intra-operative ultrasound helpful in facilitating foreign body removal?

Answer 1

Pre-operative ultrasound associated with a higher sensitivity for FB detection (88%) compared to MRI/CT (57%).

Using intraoperative ultrasound the success of FB removal was increased (90%, compared to 59% without).

Question 2

In a study by Nutt 2021 in Vet Surg, what was the difference in post-operative symmetry index (lameness of the ipsilateral thoracic limb) following either sparing or transection of the latissimus dorsi during lateral thoracotomy?

Answer 2

3 x greater with transection of the latissimus dorsi.
Post-operative pain scores were also increased.

Question 3

In a study by Pilot 2022 in Vet Surg, was wire or suture closure of a median sternotomy associated with an increased risk of closure related complications? What additional factor was identified as a risk for closure related complications?

Answer 3

No difference between groups. Size of dog was the only factor associated with an increased risk of closure related complications.

Question 4

What novel muscle flap was used for defect reconstruction following rib resection for chondrosarcoma in a case study by Cronin 2021 in JSAP?

Answer 4

Internal abdominal oblique (previously described flaps include diaphragm, external abdominal oblique, transversis abdominus, latissimus dorsi)

Question 5

In study by Cordella 2023 in VRU, what were the most commonly reported primary bone neoplasms of the thoracic wall? For which tumour types was sternal lymphadenopathy most frequent? Which tumour showed lower mineral attenuation grades?

Answer 5

Osteosarcoma (56%), chrondrosarcoma (24%), hemangiosarcoma (20%). Most were ventral (72%) and right sided (59%). Primary sternal tumours were uncommon (mainly arising from the ribs).

Osteosarcoma and hemangiosarcoma were more frequently associated with sternal lymphadenopathy as compared to chondrosarcoma.

Hemangiosarcoma showed the lowest mineral attenuation.

Question 6

In a study by Hennet 2022 in JFMS, what was the rate of closure related complications in cats undergoing median sternotomy?

Answer 6

8%, both related to sternebrae closure, no seromas, SSI or wound dehiscence occurred. Sternebrae were closed in all cases with suture.

Question 7

In a study by Klainbart 2022 in JFMS, what were negative predictors for survival in cats suffering from dog bite wounds (9)?

Answer 7

High animal trauma triage score, high injury severity score, penetrating injuries, elevated ALT, multiple body area injuries, vertebral body fractures, body wall abnormalities, hypoproteinemia, more aggressive treatments (i.e. surgery).

Question 8

What structures travel through the thoracic inlet?

Answer 8

Trachea, esophagus, great vessels, vagus, recurrent laryngeal and phrenic nerves.

Question 9

What flaps can be made based on the thoracodorsal artery?

Answer 9

Thoracodorsal axial pattern flap, composite musculocutaneous flap including the latissimus dorsi.

Question 10

What muscle attaches to the manubrium?

Answer 10

Sternocephalicus.

Question 11

What is the origin and insertion of the latissimus dorsi muscle?

Answer 11

Origin: lumbodorsal fascia and thoracolumbar vertebrae.
Insertion: proximal humerus.

Question 12

What is the origin and insertion of the serratus ventralis muscle?

Answer 12

Origin: caudal aspect of the first seven or eight ribs.
Insertion: medial serrate surface of the scapula.

Question 13

The tendinous portion of the scalenous muscle is visible at which rib?

Answer 13

The fifth.

Question 14

Which muscles must be separated during a median sternotomy?

Answer 14

The pectoral muscles. Branches of the internal thoracic artery and vein perforate between the left and right deep pectoral muscles and should be avoided or ligated.

Question 15

The transverse thoracic muscle is an important landmark for which structure?

Answer 15

The internal thoracic artery (travels dorsal to the muscle).

Question 16

Describe the anatomy of the rib cage.

Answer 16

Question 17

On which aspect of the rib do the intercostal nerves and vessels travel?

Answer 17

Caudal edge of each rib.

Question 18

The intercostal arteries are branches of which arteries?

Answer 18

First 4 are branches of the thoracic vertebral artery, the remainder are branches of the aorta. Ventrally they anastomose with branches of the internal thoracic artery.

Question 19

The internal thoracic arteries are branches of which vessels?

Answer 19

The left and right subclavian arteries.

Question 20

What vessels fuse to form the cranial vena cava?

Answer 20

The external jugular and brachial veins join to form paired brachycephalic trunks which then merge into the cranial vena cava in the cranial sternum. Care should be taken not to damage these structures during median sternotomy.

Question 21

Are the right ventricular outflow tract and pulmonary artery best accessed via a right or left intercostal thoracotomy?

Answer 21

Left

Question 22

Via what approach is the left ventricular apex most accessible?

Answer 22

Transdiaphragmatic

Question 23

What determines total pulmonary compliance?

Answer 23

Combined compliance of the thoracic walls and lungs

Question 24

Describe the surgical technique for intercostal thoracotomy.

Answer 24

Question 25

When separating the serratus ventralis during intercostal thoracotomy a branch of what vessel is encountered?

Answer 25

Intercostal artery supplying the muscle that requires ligation.

Question 26

What is the ventral and dorsal extent of an intercostal thoracotomy?

Answer 26

Dorsal: where the ribs angle medially. Extension of the incision can damage the epaxial musculature. Ventral: costochondral junction. Additional extension ventrally should only be performed after confirming the location of the internal thoracic artery.

Question 27

Describe the surgical closure of an intercostal thoracotomy.

Answer 27

Question 28

What is the importance of sectioning sternebrae longitudinally during median sternotomy?

Answer 28

Reduced postoperative morbidity.

Question 29

Describe the surgical approach for a median sternotomy.

Answer 29

Question 30

During median sternotomy where can the sternal lymph nodes be located?

Answer 30

Where the internal thoracic vessels reach the transverse thoracic muscle.

Question 31

What materials are used for closure of a median sternotomy?

Answer 31

Figure-of-eight sutures of stainless steel wire (>10 kg) or 0-polypropylene (<10 kg). Figure-of-eight stainless steel sutures have been shown to be mechanically superior to double-loop cerclage.

Question 32

During closure of a median sternotomy why is alternating the orientation of the sutures/wire recommended?

Answer 32

To avoid distraction of the dorsal or ventral edge during tightening and to maximise bony contact.

Question 33

What are surgical options for approach to the thorax?

Answer 33

1. Intercostal thoracotomy. 2. Median sternotomy. 3. Xiphoid resection thoracotomy. 4. Transsternal thoracotomy. 5. Transdiaphragmatic thoracotomy. 6. Paracostal approach. 7. Thoracoscopy.

Question 34

When performing thoracoscopy why is the transxiphoid rather than cervical approach preferred?

Answer 34

The cervical approach is associated with a high risk of hemorrhage due to perforation of the great vessels.

Question 35

Which vessel is divided during a paracostal approach to the thorax?

Answer 35

The phrenicoabdominal vein. This approach provides access to the cisterna chyli, aorta, and thoracic duct as it passes from the abdomen into the thorax.

Question 36

What are the sequelae of severe pectus excavatum?

Answer 36

Restriction of thoracic volume, compression of intrathoracic structures, impaired ventilation. If severe enough can produce dynamic right ventricular outflow obstruction.

Question 37

What breeds of cat are predisposed to pectus excavatum?

Answer 37

Burmese and Bengals.

Question 38

What are the treatment options for pectus excavatum?

Answer 38

1. External splinting for 2-4 weeks. 2. Internal splinting with a veterinary cuttable plate (may be required in older patients). Care should be taken during pulmonary inflation due to risk of pulmonary reexpansion injury.

Question 39

Based off the radiograph, what is your diagnosis?

Answer 39

Question 40

What imaging techniques might be useful for the work-up of infected lesions of the thoracic wall?

Answer 40

Radiography, fistulography, ultrasound, CT.

Question 41

When evaluating thoracic wall trauma using point-of-care ultrasound, what does a 'step-sign' indicate?

Answer 41

Discontinuity of the parietal pleural surface, which can signify a rib fracture or intercostal muscle tear.

Question 42

What additional injuries might be present with thoracic wall trauma?

Answer 42

Pulmonary contusions, flail chest, diaphragmatic rupture.

Question 43

What signs might indicate that surgical exploration of a penetrating injury to the chest is warranted?

Answer 43

Ongoing hemorrhage, pneumothorax, or sepsis.

Question 44

How should sucking wounds of the thoracic wall be treated?

Answer 44

Immediate debridement and direct suturing to reestablish pleural space integrity + ongoing drainage. Muscle flaps or omentum may be required for extensive wounds.

Question 45

When should thoracic bite wound injuries be explored?

Answer 45

If there are concurrent rib fractures, pulmonary contusions, or pneumothorax.

Question 46

What is the mortality rate for extensive bite wound trauma?

Answer 46

11-16%. Wound complications occur in 11% of affected animals.

Question 47

What rib suturing technique is shown and when might it be indicated?

Answer 47

Basket weave pattern for correction of multiple lacerations of the intercostal muscles.

Question 48

Do flail chests require surgical intervention for stabilization?

Answer 48

Generally not, issues with respiration more likely related to underlying pulmonary trauma than the flail chest segment.

Question 49

If fixation of a flail chest segment is elected, what method of fixation is most frequently performed?

Answer 49

External splint fixation extending 1 rib cranial and 1 rib caudal to the flail segment and left in place for 2 weeks.

Question 50

What are the most common thoracic wall tumours?

Answer 50

Chondrosarcoma, osteosarcoma, fibrosarcoma, other spindle cell tumours (PNST, hemangiopericytoma), hemangiosarcoma (infrequent).

Question 51

What is the MST for patients undergoing thoracic wall resection for osteosarcoma and chondrosarcoma?

Answer 51

Chondrosarcoma: 250 weeks. Osteosarcoma: 17 weeks.

Question 52

What imaging techniques can be used in the work-up of thoracic wall tumours?

Answer 52

Radiography, ultrasound (can help differentiate between pleural and thoracic wall masses, facilitates FNA and needle biopsy under ultrasound guidance), CT.

Question 53

Assessment of which lymph nodes is recommended when evaluating thoracic wall tumours?

Answer 53

Sternal and axillary.

Question 54

What are the recommended surgical margins for resection of thoracic wall tumours?

Answer 54

3cm margins including at least 1 unaffected rib cranial and caudal (complete removal of the rib has been recommended by some surgeons in primary bone tumours likely to invade the bone marrow). Preservation of the skin may be possible if there is an intact fascial layer between the tumour and the skin.

Question 55

What are some options for thoracic wall reconstruction?

Answer 55

1. Muscle flaps (diaphragm, external abdominal oblique, transversis abdominus, latissimus dorsi). 2. Prosthetic mesh. 3. Biologic grafts.

Question 56

What are the three main goals of thoracic wall reconstruction?

Answer 56

1. Restore the integrity of the pleural space. 2. Ensure sufficient rigidity of the thoracic wall to restore the thoracic bellows. 3. Epithelial coverage.

Question 57

How many ribs can be safely removed during thoracic wall resection?

Answer 57

4 ribs is the upper limit for reconstruction with readily available tissues. 6 ribs is the upper limit for adequate reconstruction.

Question 58

How can defects of the sternum be reconstructed?

Answer 58

Autogenous muscle flaps (such as the deep pectoral muscle), or the use of rigid implants (i.e. PMMA, Kiel bone).

Question 59

Thoracic wall defects secondary to resection of which ribs are best repaired using diaphragmatic advancement?

Answer 59

Caudal ribs 8-13. The abdominal defect can then be repaired using muscle flaps, mesh or other surgical implants.

Question 60

The latissimus dorsi muscle is useful for repairing defects of which section of the thoracic wall?

Answer 60

Tumors close to the costochondral junctions. The skin defect can then be closed with a thoracodorsal axial pattern flap, elbow fold flap, other subdermal plexus flap (advancement flaps or H-plasty).

Question 61

What types of prosthetic mesh are available for thoracic wall reconstruction?

Answer 61

1. Polypropylene (prolene). 2. PTFE. 3. Polyglactin (absorbable). Prolene mesh resists stretching in all directions, while PTFE is strong and provides an occlusive layer that allows maintenance of an airtight seal.

Question 62

What are complications associated with use of prosthetic mesh for closure of thoracic wall defects?

Answer 62

Wound infection (0-5.7%). Infection rates can be reduced if the mesh is covered with a well vascularized tissue, i.e. muscle flaps or omentum.

Question 63

What can be used to protect the lungs from abrasion by mesh?

Answer 63

Porcine SIS and/or omental flaps. Also help to restore the integrity of the pleural space and provide a leakproof seal.

Question 64

What are some local anesthetic options of dogs undergoing thoracic wall resection?

Answer 64

Local infiltrative blocks of bupivacaine in the intercostal spaces of the surgical site and two spaces cranial and caudal, epidural anesthesia, intrapleural bupivacaine infusion through the thoracotomy tube.

Question 65

What are some complications/post-operative considerations in patients undergoing thoracic wall resection?

Answer 65

1. Pleural effusion (normally most severe for the first 4-5 days). 2. Pain. 3. Oxygenation defects (hypoventilation, atelectasis, medications). 4. Hypothermia. 5. Hypovolemia.