Ch 104 Thoracic wall Flashcards
Wha flaps can be based on the thoracodorsal artery?
- Thoracodorsal axial pattern flap
- Composite musculocutaneous flap incorporating latissimus dorsi
What muscle attaches to the manubrium?
Sternocephalicus muscle
muscular anatomy
intrinsic and extrinsic muscles of respiration, muscles of the abdominal wall, and locomotor musculature
locomotor muscles
- attach the forelimb to the trunk.
- latissimus dorsi Ithoracolaumbar vertebrae > humerus)
- serratus ventralis thoracis (first seven or eight ribs > scapula)
- superficial and deep pectoral muscles (sternum and the medial humerus)
scalenus (tendinous portions is visible at the fifth rib)
external and internal intercostal muscles
transverse thoracic muscle (pleural surface sternum to costochondral junctions)
Nerves and Blood Vessels
- Intercostal nerves: ventral branches of the thoracic spinal nerves and pass ventrally along the caudal edge of each rib + intercostal arteries and veins
- 12 intercostal arteries: first 3 or 4 are branches of the thoracic vertebral artery, and the remainder are branches of the aorta
- anastomose with ventral intercostal branches of the internal thoracic artery
- internal thoracic arteries arise from the left and right subclavian arterie
- external jugular veins and brachial veins join to form paired brachiocephalic trunks > cranial vena cava
approaches for organs (4)
Left intercostal thoracotomy
- left side of the heart
- right ventricular outflow tract and pulmonary artery
Right lateral thoracotomy
- trachea
- esophagus
- right atrium
- venae cavae
- azygous vein
Median sternotomy
- the cranial vena cava
transdiaphragmatic approach
- heart apex (epicardial pacemaker leads)
Physiology and Pathophysiology
- thoracic wall and lungs are functionally linked by negative pleural pressures,
- total pulmonary compliance is a function of the additive compliance of the thoracic wall and lungs
- Alterations in thoracic volume (wall resection or advancement of the diaphragm or tumors) have an impact on ventilation and tidal volume.
list thoracic approaches (8)
- intercostal
- rib resection (for wide access to the thoracic cavity, as part of en bloc excision of a thoracic wall tumor, or for removal of large masses)
- median sternotomy
- xiphoid resection (allowing entry to the ventral thorax just in front of the diaphragm, without entering the peritoneal cavity)
- transternal (connecting two lateral thoracotomy incisions)
- transdiaphragmatic
- paracostal
- thorascopic
Intercostal Thoracotomy
- fourth and fifth intercostal thoracotomy, the skin is incised 2 cm caudal to the scapula
- intercoastal nerve blocks
- latissimus dorsi muscle is divided or elevated
- serratus ventralis muscle is elevated from the rib caudal
- External and internal intercostal muscles are incised
- pleura is left intact
- extended dorsally to the point where the ribs angle medially (epaxial musculature) and ventrally to a point just below the costochondral junction ( internal thoracic artery, palpate)
- Finochietto retractors are inserted
- Three to four cruciate sutures, or four to six encircling sutures, of 2-0 to 1 polydioxanone suture are preplaced
What can be used as landmarks during an IC thoracotomy?
Ribs - finger can be placed uder latissimus to count back from first rib
Scalenus - attached to 5th rib
What muscle is a landmark for the internal thoracic artery?
Transverse thoracic muscle (travels dorsal to muscle)
What structures can be damaged during a cranial median sternotomy?
The brachiocephalic truncks and cranial vena cava (Sit right below the sternum and can become collapse during retraction resembling connective tissue)
median sternotomy
- choice for bilateral exploration of the thoracic cavity, wide exposure of cranial mediastinal masses
- Access to the dorsal mediastinum is limited (i.e. more difficutl for lonectomy)
- not for sx on esophagus or caudal vena cava
- morbidity reduced by ensuring the sternebrae are sectioned longitudinally without being broken
- Instability of the sternotomy causes severe postoperative pain and prolonged recovery
- partial sternotomy performed initially; completed if greater access is required
- Air embolism is common during sternotomy,
- electrocautery reduces the amount of bleeding encountered from perforating branches of the internal thoracic artery
- internal thoracic artery and vein are identified in the cranial portion of the thorax
- closed using figure of eight sutures of stainless-steel wire (in patients weighing >10 kg) or 0 polypropylene (in patients weighing <10 kg)
What instruments can be used to perform a median sternotomy?
Reciprocating saw
Osteotome
Special sternal saw
Sternal splitter
Bone cutters
Where are the sternal LNs located?
Where the internal thoracic arteries meet the transverse thoracic muscle
Why is an alternating figure-of-8 pattern beneficial for closure of the sternum?
Avoids distraction of the dorsal or ventral edge
Maximises boney contact
Reduces pain
Facilitates healing
transdiaphragmatic
- inspection of the caudal lung lobe, thoracic duct, caudal esophagotomy, hepatic sx
- most common > diaphragmatic hernia
- incision in either crus of the diaphragm or through the central tendon
- initial incisions should be made in the ventral portion of the diaphragm
- Air and fluid are drained from the thorax before closure of the laparotomy (ransdiaphragmatic thoracotomy tube)
- Billowing of the diaphragm during ventilation signifies residual pleural air.
What vessels may bleed during a transdiaphragmatic thoracotomy?
Branches of the phrenic artery
What can the paracostal approach be used for?
- Right sided for accessing thoracic duct, cisterna chyli and aorta
- Adrenalectomy
- Migrating FBs for abdominal and thoracic exploration
through the musculature of the lateral abdominal wall, just caudal to the last rib.
The muscular attachment of the diaphragm to the costal arch is divided, leaving enough muscle attached to the ribs to facilitate closure.
What are the 2 broad options for thoracoscopy?
- Intercostal
- Paraxyphoid (between the sternum and the diaphragm (Morgagni’s foramen)
camera is then inserted so that additional ports can be placed under direct vision
What breeds are predisposed to pectus excavatum?
Burmese and Bengal cats
- Sternum and caudal ribs fail to grow normally, possible due to shortened or hypoplastic diaphragm, resulting in concave abnormality of the caudal sternebrae
- more serious deformity, with critical restriction of thoracic volume, compression of intrathoracic structures, and impaired ventilation
How is pectus excavatum treated?
- External splinting in young animal with compliant sternebrae > immediate improvement in ventilatory function and encouraging a more natural conformation as they grow, splint 2-4 weeks
- Older animals may need an internal splint (VCP) or osteotomy of deformed sternebrae and costochondral junctions with external splinting
In what breed has a sternal cleft been described?
Along with what other congenital defects?
GSD
With PPDH and cranial abdominal hernia
Trauma
- Although the risk of damage to intrathoracic structures after blunt force trauma is high, surprisingly few patients experience serious injury to the thoracic wall, presumably because of its compliance
- group of 75 cats with traumatic rib fractures, 87% had concurrent intrathoracic injury
- carefully evaluated for flail chest, pulmonary contusion or laceration, and diaphragmatic rupture.
- With bite wounds, the skin may remain largely intact however, full-thickness tears of thoracic musculature, rib fractures, lung possible
- Patients with thoracic trauma should be stabilized initially
- thoracocentesis, ultrasound, rads
Sx
- Penetrating injury of the chest wall does not automatically signify that surgical exploration is warranted unless there is evidence of ongoing hemorrhage, pneumothorax, or sepsis.
- Thoracic drainage should be instituted and continued until pneumothorax resolves.
- If ventilation is inadequate, surgical exploration is indicated
What is a “step” sign on TFAST?
Indicates a discontinuity of the parietal pleura. Can signify IC muscle tear or rib fracture
In what animals with thoracic wounds should surgery be recommended?
Bite wounds > All those with rib fractures, pulm contusion or pneumothorax (according to a study)
Ongoing haemorrhage, pneumothorax or sepsis are indications for surgical exploration
How can multiple laceration of the IC muscles be apposed?
Basket-weave pattern
flail chest
- current thought is that respiratory problems in patients with flail chest are most commonly from underlying pulmonary trauma rather than the presence of the flail segment
- no significant difference in outcome between stabilized and unstabilized cases
- percutaneous fixation of the ribs within the flail segment to an external brace
- around the ribs within the flail segment and at least one rib cranial and caudal to the flail segment
List the most common thoracic wall neoplasias
Chondrosarcoma
OSA
FSA
Other spindle cell tumours (haemangiopericytoma, PNST, Schwannoma)
HSA infrequent
MCT
Neoplasia
- Most thoracic wall tumors are malignant
- rom the ribs are immobile and usually firm
- survival times after thoracic wall tumor removal vary greatly according to tumor type
- obvious mass or may develop signs of respiratory compromise
- sequele > vena cava compression, chylothorax, lameness
- ultrasound
- CT provides cross-sectional information that allows anatomic localization and better evaluation of the nature and extent of the pathologic process
- biopsy should be performed
- Surgical resection should be considered for all STS and chondrosarcomas because of their relatively low metastatic rate
- OSA > palliation of pain and pleural effusion +/- chemo
MST
- median of 17 weeks for osteosarcoma
- 250 weeks for chondrosarcoma
What are the recommended margins for thoracic wall tumours?
3 cm
- including at least one unaffected rib cranial and caudal to the lesion.
What is considered the maximum thoracic wall resection for adequate reconstruction?
6 ribs
Resection of Thoracic Wall Tumors
- Cutaneous and subcutaneous tumors that do not involve the ribs or intercostal muscles may be resected with a deep margin by excising the layered thoracic musculature
- If the tumor involves deep structures only, with a fascial layer between it and the skin, it may be possible to preserve skin to simplify wound closure.
- ## thorocotomy for inspection of the intrathoracic component to confirm that the proposed excision will, indeed, provide adequate surgical margins
List options for sternal reconstruction
- Deep pectoral muscle flaps
- Sanwiches of mesh and PMMA
- Kiel bone
Thoracic Wall Reconstruction
main goals
- restore integrity of the pleural space (negative pressure)
- ensure sufficient rigidity of the thoracic wall
- ensure epithelial coverage
- Experimental and clinical studies have shown that a small section of flail chest does not adversely affect ventilatory function in dog
- 4 ribs > reconstructed using readily available tissues
- Larger or defects of the sternum or diaphragm > planning to avoid flail chest, mediastinal shift, and undue postoperative pain
What muscle flaps can be used for thoracic wall reconstruction?
- Latissimus dorsi
- External abdominal oblique
- Transversus abdominis
- Diaphragmatic advancement (ribs 8-13) (may require caudal lung lobectomy)
List options for reconstruction with commercial products
- Polypropylene mesh
- PTFE mesh/sheet ($$, strong and occlusive)
- Polyglactin mesh (absorbable, good for infected sites)
- Porcine SIS
Infection rates with polypropylene mesh 0-5.7%. Can be minimised by covering with well vascularised tissue (omentum, muscle)
Muscle Flaps
- Thoracic wall defects arising from resection of the caudal ribs (8 through 13) are best reconstructed by ipsilateral diaphragmatic advancement
- Occasionally, animals may require caudal lung lobectomy with diaphragmatic advancement because of a reduced pleural cavity size
- costochondral junctions > closed with a latissimus dorsi muscle flap
- dorsi muscle is transected at its origin along the vertebral spinous processes,
- skin: advancement flaps, or H-plasty.
Commercial Products Available for Reconstruction
- Prolene mesh resists stretching in all directions
- PTFE is strong, and the sheets (as opposed to the mesh) provide an occlusive layer that allows maintenance of an airtight seal.
- polyglactin mesh is absorbable and therefore indicated for infected or contaminated sites.
- associated with persistent postimplantation wound infection, low rate in dogs
- Infection rates are reduced in dogs and humans if the mesh is covered by well-vascularized tissue
- polypropylene mesh can first be closed with porcine small intestinal > pleural seal and protect organs from mesh
Postoperative Care
- if pneumothorax or pleural effusion is of concern, a thoracic drain is maintained for at least 12 hours after surgery.
- Pleural effusion is a major complication of thoracic wall resection and reconstruction
- patients should be carefully monitored for respiratory and cardiovascular sequelae
- Abnormal function, lung atelectasis, hypoventilation from pain or medications may all result in abnormal blood gas values
- may require Oxygen supplementation
- Patients with hypotension should be evaluated for underlying causes, such as hemorrhage, hypovolemia
- infiltrative blocks of bupivacaine administered in the intercostal spaces of the surgery site
- Systemic agents include intermittent bolus or constant rate infusions of opioids
How often should the thoracostomy tube be suctioned in the post-op period?
When is pleural effusion most common after thoracic wall reconstruction?
- Suctioned every hour until 3 consecutive negative results have been obtained. Then every 4 hours for 12 hours
- Pleural effusion after reconstruction within forst 48hr and then declines sharply within 4-5 days
Parasternal thoracotomy via sternocostal disarticulation: a novel surgical approach to the canine thorax
Weiland 2024
rib disarticulation at the sternocostal joint
93 client-owned dogs
Eighty-three dogs (89.2%) survived to discharge from the hospital
Thoracostomy tube duration significantly decreased the likelihood for survival to discharge
viable alternative to median sternotomy
Postoperative complications and short-term outcomes are comparable to those reported for the traditional median sternotomy approach
Closure was performed with a nonabsorbable monofilament suture in a simple interrupted pattern engaging the periosteum of the rib to the sternocostal cartilage.
neoplasia (45.2% total; 37.6% with histopathologic confirmation), followed by pulmonary bullae
There were no reported complications of hemorrhage associated with the PT approach.
Thirty dogs (32.3%) experienced postoperative complications.
thoracic limb lameness not initially documented on presentation (dogs 5 and 30). Three dogs (3.2%) experienced major complications
Previous studies6,11,12,19 have reported wound healing complications for sternotomy closure ranging from 31% to 55%. The total postoperative complication rate in our study was 32.3%. The
only 7 dogs (7.5%) had incisional complications
Parasternal thoracotomy may provide fewer closure-related complications than the traditional MS approach
high postoperative complication rate, ranging from 14% to 78%.7,11–13,15,18 The reported postoperative complications include pain, lameness, infection, dehiscence, draining tracts, internal thoracic artery compromise, and osteomyelitis
71% of MS patients developing wound complications compared to only 23% of ICT patients
Surgical treatment and outcome of primary rib tumours in cats: eight cases (2016-2023)
F. Cinti 2024
three had hemangiosarcoma, two had osteosarcoma and one cat each had chondrosarcoma, osteochondroma and osteoma
Three minor and one major complication developed during the immediate post-operative period.
Wide surgical excision and adjuvant chemotherapy is recommended for cats with hemangiosarcoma and osteosarcoma, but the prognosis remains guarded. Prognosis appears to be fair for the other tumour types.
chest wall reconstruction with polypropylene mesh in combination of latissimus
dorsi and superficial pectoral muscles flap and ometalization
paradoxical rep movement > suspect this post-operative
complication may have resulted from
inappropriate tensioning of the muscle flap created
preoperative incisional biopsy should be performed to discriminate
between benign and malignant tumours as this will allowto plan the appropriate surgery..
no clear benefit for chemo
Biomechanical comparison of bone staple
fixation methods with suture material for median
sternotomy closure using 3D-printed bone models
YG Park 2024
NZVJ
polydioxanone suture (group PDS, n = 30), stainless steel bone staples (group SS, n = 30),
and nitinol bone staples (group NS, n = 30).
tensile force in one of three ways (longitudinally, laterally, or torsionally
NS and SS staple repairs required
application of significantly greater force than PDS across all displacement criteria
NS had a higher failure load than PDS under lateral, longitudinal,
and torsional distraction.
Clinical relevance: These study results imply that bone staples can be considered as an
alternative surgical method for median sternotomy closure in dogs.
Using this mathematical
model, a force of 346 N was calculated to act on the
sternotomy site during coughing in a 30-kg greyhound
(Gines et al. 2011). Based on our study, a force of 346 N
applied during coughing is capable of causing 1- and 2-
mm displacement in the PDS group during lateral distraction;
however, it is insufficient to cause even 1-
mm of displacement in the bone staple groups.
Using this mathematical
model, a force of 346 N was calculated to act on the
sternotomy site during coughing in a 30-kg greyhound
(Gines et al. 2011). Based on our study, a force of 346 N
applied during coughing is capable of causing 1- and 2-
mm displacement in the PDS group during lateral distraction;
however, it is insufficient to cause even 1-
mm of displacement in the bone staple groups.
Biomechanical comparison of canine median sternotomy
closure using suture tape and orthopedic wire cerclage
Rachel E. Rivenburg 2023
Ex vivo.
Animals: Twelve large-breed canine cadaveric sternums.
No differences were observed for displacement, yield load, maximum
load, implant failure between the groups. The orthopedic wire construct was
stiffer than the suture tape construct.
Conclusion: Suture tape was biomechanically similar to orthopedic wire cerclage
for sternotomy closure in dogs, although wire constructs were stiffer.
We are not yet able to recommend
the use of suture tape over orthopedic wire as a
closure technique for canine median sternotomies but
the data presented support its clinical utility as a closure
method in clinical cases.
Comparison of median sternotomy closure-related
complication rates using orthopedic wire or suture in dogs:
A multi-institutional observational treatment effect
analysis
Mariette A. Pilot 2022
Multi-institutional, retrospective
263
Thirty-seven dogs experienced closure-related complications
(14.1%), 20 in the wire group and 17 in the suture group.
10 as severe. Treatment effect analysis
showed a mean of 2.3% reduction in closure-related complications associated
with using suture versus wire.
only factor associated with increased risk of closure-related
complications was dog size
The likelihood of developing a closure-related
complication was equivalent between sutures and wires, independent of dog
size, despite a higher proportion of complications seen in larger dogs (≥20 kg).
Clinical significance: Use of either orthopedic wire or suture appear to be an
appropriate closure method for sternotomy in dogs of any size.
The confirmed infection rate of 2.7% in
this study is within a previously reported rate of surgical
site infections
A previously performed biomechanical study has
shown that suture (four metric polydioxanone) could pro
vide
as effective closure of the sternum as orthopedic
wire (12 gauge) in 12 greyhounds.
Ten dogs
underwent revision surgery, nine due to closure-related
complication
Thoracic dog bite wounds in cats:
a retrospective study of 22 cases
(2005–2015)
Anna K Frykfors von Hekkel
Presence of ⩾3 radiographic lesions should raise suspicion of a penetrating injury
and may be suggestive of injury requiring a greater level of intervention. The treating veterinarian should have a
high index of suspicion for penetrating injury and be prepared in case thoracic exploratory surgery is necessary,
particularly in the presence of pseudo-flail chest, pneumothorax or ⩾3 radiographic lesions.
Pneumothorax was the most
common radiographic finding (11/18).
Crimped monofilament nylon leader for median
sternotomy closure in 10 dogs
Matteo Rossanese 2021
Retrospective observational study.
Animals: Dogs (n = 10)
Postoperative infection was documented in one dog,
Median sternotomies were successfully closed with crimped
MNL and were associated with a low complication rate.
Stainless-steel wire has high tensile strength and stiffness,
low tissue reactivity, and good knot security. However, it
has poor handling characteristics, with glove perforation
Stainless-steel wire fracture was reported in 20% of dogs
SSW fracture reported, histopathology results provided evidence of chondral and osteochondral bridging at the sternotomy site in comparison to fibrous unions with suture closure.
biomechanically, MNL is less stiff than SSW and
will creep under constant displacement
Influence of muscle-sparing lateral thoracotomy
on postoperative pain and lameness: A randomized
clinical trial
Anna E. Nutt 2021
Randomized, blinded, prospective clinical study.
Animals: Twenty-eight client-owned dogs.
Gait was analyzed with a force plate
preoperative and 3-daypostoperative
SI provided evidence that this change was 3.1-fold greater after
SLT compared with after MSLT (P = .009). Pain scores 1 day after surgery were
lower after MSLT (1) compared with after SLT (2.5, P < .001).
Conclusion: Lateral thoracotomies caused postoperative pain and ipsilateral
forelimb lameness, and both were reduced by sparing the latissimus dorsi
because all dogs were lame
on the ipsilateral thoracic limb to some degree postoperatively,
it can be concluded that muscle transection is not
the sole cause of pain.
Thoracic dog bite wounds in dogs: A retrospective study
of 123 cases (2003-2016)
Anna K. Frykfors von Hekkel 2020
Retrospective study.
Dogs that sustained pseudo-flail chest, rib fracture, or pneumothorax
were more likely to undergo exploratory thoracotomy. Nonsurvival was
more likely in dogs with pleural effusion or positive bacterial culture.
Some previous authors have advocated a more con
servative
approach to the management of thoracic dog
bite wounds because of higher mortality rates after thora
cotomy
