Exam 2 Flashcards
What are the primary sources of blood for skin flaps?
The deep cutaneous artery and vein (big vessels that supply a wide area) which then branch into the deep/subdermal plexus
-provided by the skeletal musculature and panniculus muscles respectively
What are some important things to consider when handling the skin?
-extremely gentle handling
-avoid grasping skin at the reconstructive sites with thumb forceps
-use skin hooks or stay sutures to allow for gentle tissue handling
Where on a skin flap is the blood supply the most compromised?
At the tip (farthest away from blood supply)
- must be extremely delicate if using the tip of the tissue to move the flap- can use the subQ tissue to grab rather than the top of the skin
T/F: The incision always needs to be perpendicular to the tension lines
False. It needs to be parallel to the tension lines
- allows you to close with the least amount of tension
Are skin sutures ever for tension reduction?
NOO- just there to achieve nice apposition of the skin edges
Describe the concept of mechanical creep.
Mechanical creep is what happens when skin is under load for a period of time
- as stress is placed on skin, skin can release its own tension
-tension reduction and stress relaxation can be used in the OR to release tension on tissues
Where is the highest amount of tension in an incision?
At the midline
Describe biological creep
Stretching of the skin naturally over time due to pregnancy
What are the optional conditions for the wound environment?
-wound itself should have no infection and good blood supply
-the area surrounding the wound should have minimal inflammation and necrosis
What are the primary wound factors you need to consider when deciding how to close? What about patient specific factors? Owner factors?
Wound factors: size and shape of the wound, anatomic location
Patient factors: must consider species and breed, age, temperament and comorbidities
Owner factors: financial considerations, compliance
Describe the process of undermining the skin
-separate the skin from the underlying tissue
-preserve the subdermal plexus by cutting deep to the cutaneous trunci/platysa/sphincter colli muscles
-if in an area that you cannot see the above muscles, cut to the underlying muscle fascia
In what situation do you want to avoid undermining?
When resecting tumors
If placing sutures to stretch the skin, what 2 things can help to avoid damage to the patient?
Placing foam underneath the sutures so they don’t cut the underlying tissue
- placing the tissues a bit off of the tissue edge so they don’t rip out
What are the 4 examples we discussed in class of tension relieving sutures?
Cruciate sutures, far-near-near-far, and far-far-near-near, mattress sutures
What is important to consider when using walking sutures?
Don’t place too many as they can compromise the blood supply!
-make bites parallel to the direction of pull
-take strong bites of the dermis but do not penetrate the skin
How can bolsters be used for tension reduction?
You place then under vertical mattress sutures to reduce tension on the skin itself and instead put the tension over another material
What are the two different techniques for relaxing incisions?
- Single relaxing incision (bipedicle flap)
- Mesh relaxing incision (1 cm incisions inrows spaced 1 cm apart)
What is the main worry when using a mesh relaxing incision?
There is a chance that you may devitalize the skin
- therefore it is very important to be judicious with this technique
What are the main considerations when using subdermal plexus flaps?
- maintain appropriate base (larger than width of flap) in order to preserve the blood supply as much as possible
-the length needs to be sufficient to cover the defect
What are the main differences between single pedicle flaps and bipedicle flaps?
-with single pedicle flaps there are 2 skin incisions made equal in length to the defect
-with bipedicle flaps the incisions are made parallel to the long axis of the defect, and the flap length should be no more than 2X the length of the flap base
When would you use subdermal plexus rotation flaps?
In situations where there is not loose skin immediately surrounding the defect, but the skin is looser a bit more proximal or distal to the defect
T/F: With transposition flaps, the width of the flap has to equal the width of the defect
TRUE
-these flaps are performed in which one border of the flap is adjacent to the defect, and then the skin is rotated
In what areas are skin fold flaps commonly used?
Flank fold flaps and elbow fold flaps to cover defects on upper limbs
With axial pattern flaps, where does the blood supply come from?
The direct cutaneous artery and vein
-can be longer relative to the pedicle
-can be rotated up to 180 degrees at the base
-overall survival rate: 87-100%
-need to know anatomy of the vessels
What is the difference between peninsula and island flaps?
Peninsula flaps have intact skin at base vs island flaps have no connection to surrounding skin
What are the 4 processes that allow free skin grafts to survive?
Adherence: fibrin strands –> fibrous adhesions
Plasmacytic imbibition
Inosculation
Vascular ingrowth/revascularizarion
What type of free skin graft has the most ideal characteristics for survival?
A: split thickness unmeshed grafts
B: Full thickness unmeshed grafts
C: full thickness mesh grafts
D: split thickness mesh grafts
D
What are the main post-op complications of reconstruction surgery?
-necrosis
-dehiscence
-seroma
-infection
What are the main factors that contribute to reconstruction complications?
-compromised blood supply
-excessive tension
-excessive motion
-cold
What is the cutoff for acute vs chronic diaphragmatic hernias?
Acute is less than 14 days, chronic is greater than 14 days
What are the 2 different types of congenital diaphragmatic hernias?
- pleuroperitoneal and peritoneopericardial
If the diaphragm tears, is it more likely to be at the muscular or tendinous portion?
The muscular portion
Name the foramen in the diagram from ventral to dorsal?
Caval foramen, esophageal hiatus, aortic hiatus
What travels through the esophageal hiatus?
The esophagus (of course) and the vagus nerve
What is the difference between a circumferential tear, radial tear and combined tear of the diaphragm?
A circumferential tear occurs parallel to the body wall, a radial tear occurs perpendicular to the body wall and a combined tear occurs in multiple directions
What is the most common source of trauma that would cause a diaphragmatic tear?
Motor vehicle accidents
-may also see pulmonary contusions and rib fractures
-must do basic stabilization before focusing on the most ugly lesions
What can cause iatrogenic diaphragmatic tears?
Too long of an incision for abdominal exploratory, or being too enthusiastic when clearing falciform fat
-could also be from thoracocentesis
How does indirect injury cause diaphragmatic tears?
A acute increase in intraabdominal pressure can cause a diaphragmatic costal muscle rupture
What is one of the most concerning sequele to diaphragmatic tears?
Organ herniation
Rank the likelihood of the following organs to herniate through the abdomen from most likely to least likely:
1. Uterus
2. Omentum
3. Spleen
4. Liver
5. Colon
6. Stomach
7. Small intestine
8. Pancreas
Liver, small intestine, stomach, spleen, omentum, pancreas, colon, uterus
What are the main clinical signs associated with diaphragmatic hernias?
Dyspnea (most common), hypovolemic shock due to cardiopulmonary decompensation (in trauma patients), GI signs, Lethargy, difficulty lying down
T/F: You should rule out a diaphragmatic hernia if there is no history of acute trauma
NO
What are some of the complications associated with diaphragmatic tears?
- pneumothorax, hemothorax, pleural effusion
-herniated viscera, possible strangulation
-pulmonary and caval compression
-chest wall contusions, flail chest
Why are the veins the first to be affected by compressive effects after herniations?
They are thin walled and compress easily
What to you expect to hear/see/feel on your physical exam?
-Muffled heart and lung sounds (displaced heart sounds)
-Thoracic borborygmi (not reliable)
-Tucked up abdomen (in the case of chronic hernias)
-can have a normal physical exam
Which diagnostics are the most useful and readily available imaging diagnostics for diaphragmatic hernias?
Thoracic radiographs and abdominal ultrasound
Which view is most helpful for diagnosing diaphragmatic hernias via radiographs?
Lateral views
- can see loss of normal diaphragmatic outline in 66-97% of cases
-abdominal viscera in thorax is diagnostic
-obscured or displaced cardiac shadow
-excessively displaced cranial pylorus/duodenum
When does ultrasound become very helpful in cases of diaphragmatic hernias?
When there is concurrent pleural effusion
-can diagnose diaphragmatic hernias with 93% accuracy
T/F: CT scan is often indicated in diaphragmatic hernia cases
False- rarely indicated
- can be helpful in polytrauma cases
What are the treatment options for diaphragmatic hernias?
Surgery
-preop management critical- need to be stable (treat shock, provide analgesia, provide o2 supplementation, thoracocentesis or gastric decompression if indicated)
Describe some primary anesthetic considerations in the case of diaphragmatic hernias
-poor ventilation (viscera and fluid in thorax, pulmonary compression, lack of functional diaphragm)
-poor gas exchange (pulmonary contusions, V/Q mismatch)
-poor perfusion (shock, caval compression)
When should you do surgery in cases of diaphragmatic hernias?
- as soon as possible: when patient is stable and can tolerate anesthesia
-however, patient stability is critical!
-must take the time to improve the patients anesthetic status if at all possible
What are the 3 reasons you should not stabilize before surgery in diaphragmatic hernia cases?
-resistant deterioration of the patient despite appropriate management (must be realistic with the owners)
-gastric herniation with tympany (stomach accumulating with air in thoracic cavity)
-persistent abdominal pain (intestinal strangulation)
What are some anesthesia factors that can improve patient odds in diaphragmatic hernia cases?
-table tilt to elevate head and thorax
-preoxygenate
-rapid smooth induction
-rapid intubation
-avoid high inspiratory pressures (>20 cm H20) to avoid reinflation injury
Describe the surgical approach in diaphragmatic hernia cases
-abdominal and thoracic prep (median sternotomy, lateral thoracic prep for thoracostomy tube)
-ventral midline celiotomy common approach in all cases, but be prepared to extend into sternotomy
-reduce the hernia with gentle traction and be prepared to enlarge the defect
-evaluate viability of herniated organs
-place thoracostomy tube through the lateral thorax or abdomen for PRN thoracic evaluation
-debridement of defect edges (controversial)
-use absorbable monofilament with a simple continuous pattern (use caution when suturing around critical structures)
What unique considerations come with a chronic diaphragmatic hernia?
Mature adhesions, fibrosis, reperfusion injury, re-expansion pulmonary edema, loss of domain, primary apposition not possible
Where do adhesions and fibrosis usually occur with diaphragmatic hernia cases?
Between the herniated organs and thoracic wall and/or lung
- adhesions less than 7-14 days should not pose dissection challenges
-possible sequele of chronic adhesion dissections include hemorrhage and pulmonary air leak
Describe the mechanism of reperfusion injury
-vascular obstruction leads to anaerobic metabolism
-acute relief of the obstruction leads to release of free radicals, inflammatory cytokines–>SIRS
-need to resect strangulated tissue
Describe reexpansion pulmonary edema
-occurs in chronically atelectatic lungs
-acute reexpansion leads to reperfusion injury and pulmonary edema
What are the steps to prevent re-expansion injury?
Keep airway pressures under 20 cm H20
-do not force atelectic lung lobes to reinflate
-do not completely reestablish negative intrathoracic pressures during closure
What is loss of domain?
Occurs with chronic absence of viscera from the abdomen
- forcing closure risks excessive intra-abdominal pressures
-what are your options? organ resection starting with spleen, diaphragmatic advancement, abdominal wall reconstruction
What are some alternative closure methods in diaphragmatic hernia cases?
-muscle flaps with transversus abdominus or rectus abdominus
-autogenous grafts (omentum plus fascia)
-exogenous graft (natural or synthetic)
What is the prognosis for diaphragmatic hernia cases?
15% die before surgery, perioperative mortality 10-30%
-if they survive the perioperative period they have an excellent prognosis
What are the principle forces that act on fractures?
-Bending
-Torsional (rotational)
-compressional (axial load)
-distraction
What are the Arbeitgemeinschaft fur oosteosynthesefragen (AO) principles?
- anatomical reduction
- stable fixation
-preservation of blood supply
-early active movements
What was originally thought was needed for fracture repair
What was the rate of infections and nonunion associated with the AO principles?
Nonunion 20%
Infection 20-30%
Why did the AO principles fail?
There was too much emphasis placed on mechanics, the soft tissues and bones were neglected
Where does blood supply to a fracture initially come from?
The surrounding soft tissues
What is the main difference between a non-locking plate and a locking plate?
With a non-locking plate, you can increase the contact between the plate and the bone- over time cases micromotion and fretting
- with a locking plate, the forces are transmitted through the screw and the blood supply to the bone can be preserved. less traumatic and more versatile, stronger screw to bone interface. Can be mono-cortical preserving more of the bone
Where does the majority of blood supply in a bone lie?
In the periosteum
- must be preserved
Which is more important for fracture healing: anatomic reduction or overall alignment?
Alignment -joints must be in correct orientation with one another
What are some important considerations when getting radiographs of fractures?
-you want multiple orthogonal views
-you need to look at the distal segment in relation to the proximal to determine which way it is subluxated
T/F: cerclage wire can be used as a principle means of fixation
False- it is an ancillary treatment, cannot be used alone
- can be used ancillary to IM pin to neutralize rotational instability
T/F: IM pin has no action against rotational/torsional movement
True
What forces does the bone plate neutralize?
All of them!!
- number one means of fixation
T/F: the closer fracture fragments are to one another the quicker they will heal
True
What type of bone healing does the majority of fracture healing undergo?
Secondary
Why should you not use cerclage wire in a comminuted fracture?
It will crush all the bones together
What side of the bone should you place the plate?
On the tension side of the bone, not compression
What are the main advantages and disadvatages to monocortical locking?
Advantages: reduced vascular damage, very versatile (can use double plating and plate rod combo)
Disadvantages: risk of screw pullout in thin cortices, compromise in torsional stability
What is the equation of stress?
Stress= force/unit area
-force=ground reaction force. cant be changed
-can change unit area (increase it)
How can you affect strain?
Strain=change in length/original length
-in order for strain to go down you want the change in length to be very small
With trauma wounds, what is another system of the body that always needs to be assessed?
The nervous system! Always must look for nerve damage!
What is the best way to preserve blood supply while fixing a fracture?
Minimally invasive plate osteosynthesis
- closed approach with interlocking nail
What are the main advantages of using interlocking nails?
- reduces the bending moment as it goes through the mechanical axis of the bone
What is the most common cause of hindlimb lameness in the dog?
The cranial cruciate ligament rupture
How can you tell the right from the left meniscus?
The groove of the lateral digital extensor, and the size (medial condyle is larger than the lateral condyle)
T/F: the stifle is a hinge joint
False. it flexes, extends, internally rotates and hyperextends
What are the functions of the CCL?
Limiting cranial translocation of the tibia with respect to the femur (cranial drawer and cranial tibial thrust)
-prevents hyperextension of the stifle joint
-limits internal rotation of the tibia
-limited degree of valgus-varus support to the flexed stifle
-mechanoreceptors provide proprioceptive feedback
What is the co-contraction theory?
One of the main reasons it is believed that CCL ruptures occur
-as quadraceps start to lose force and the gastroc being a stronger muscle starts pulling the tibia into caudal translation damaging the CCL
What are the muscles that surround the stifle?
The medial crural fascia (caudal belly of the sartorius, gracillus, semitendinosis)
-function: stifle flexion, internal rotation
What is the external rotator of the tibia?
Biceps femoris
What are the passive restraints of the stifle?
-cranial and caudal cruciate ligaments
-medial and lateral menisci
-medial and lateral collateral ligaments
What is the typical signalment for CCL rupture?
Plump Labrador or Pitbull/rottweiler
-higher incidence in females than males
-young to middle aged dogs most affected
-straight legged dogs
What is the rightening of the cranial and caudal ligaments during flexion and extension also called?
The screw holm technique
When should you spay or neuter an animal from an orthopedic standpoint?
At 2 years of age
What is the etiology behind CCL ruptures?
We really dont know
- might have to do with chronic degenerative changes, acute trauma (rare-often degenerative changes present on presentation) or conformation
Compare and contrast acute trauma and chronic degenerative changes and their presentations on CCL rupture
Acute trauma: small percentage of dogs, acute history, distinct traumatic event, avulsion in young dogs (typically failure of the tibial attachment site)
Chronic degenerative changes: episodic lameness, declining strength of CCL with age, loss of fiber bundle organization and metaplastic changes of cellular elements (more marked in central core of ligament)
How does conformation play a role in CCL tear development?
-postural arthrosis
-stifle hyperextension (straight rear limbs)
-narrowing of intercondylar notch on femur
-internal rotation of tibia, abnormal slope of TPA (anatomy and posture- has not been associated clinically), obesity, excessive stress on CCL, chronic deterioration, eventual rupture
What is the worst conformational forces you can have on the stifle?
Hyperextended and internal rotation
What is the typical history for CCL?
Acute- sudden onset non weight bearing lameness followed by improvement (may not improve if concurrent meniscal tear)
Chronic: prolonged weight bearing lameness, difficulty rising and sitting, sit with affected limb out to the side of the body
Partial tear: mild weight bearing lameness associated with exercise, may resolve with rest, may last for months
Bilateral injury possible- must differentiate from neurologic disease
What are some common physical exam findings in CCL cases?
Pain, joint effusion, cranial drawer, tibial thrust, periarticular fibrosis, medial buttress, sitting posture, weight shifting during standing, thigh muscle atrophy, crepitus during joint flexion and extension
-may need to sedate or anesthetize to complete examination, compare with opposite limb if unsure
-click during walking
Will arthocentesis of a CCL joint have inflammatory cells present?
NOO
What is the sit test?
If tuber calcaneous is outside of tuber ischii when animal sits, this is strongly suggestive of a CCL rupture
-BUT can also be seen with a tarsal injury
Describe the cranial drawer motion test
-should be performed in extension with a standing angle of 135 degrees (to diagnose complete tear) and 90 degrees of flexion (to diagnose partial tear)
***can diagnose both a partial and a complete tear
-young dog may have a small amount of movement with normal stifle
Which of the CCL bands is taught in both extension and flexion?
The craniomedial band
The caudolateral band is taught in extension and relaced in flexion
How long does it usually take for a partial tear to progress to a complete tear?
usually within 1 year of the onset of lameness
Can surgery on a CCL halt the progression of OA?
NO- but it does slow it down
What test allowed for us to have the founding principle to develop all of our surgical CCL repair techniques?
Cranial tibial thrust
-mimics dog walking - with hock flexed and gastrocnemius contracted
Is it possible to have negative cranial drawer and positive tibial thrust?
NO
What are some common radiographic findings in CCL rupture cases?
cranial displacement of the infrapatellar fat pad
-articular cartilage degeneration
-periarticular osteophyte development (on trochlear ridge, caudal tibial plateau, distal pole of patella)
-capsular fibrosis
-joint effusion (cranial compression of fat pad)
- subchondral sclerosis
-thickening of medial fibrous joint capsule
-may see evidence of avulsion
-can rule out other causes of stifle lameness
Describe some of the normal arthocentesis findings in CCL cases
-anticollagen antibodies and immune complexes
-non inflammatory arthopathy (WBC < 5000)
-synovitis (lymphoplasmacytic)
-elevated collagenase (produced by cartilage cells, inhibited by doxycycline)
Indicated when joint palpations and radiographs are inconclusive
-mianly used to evaluate the meniscus
What can arthroscopy be used for?
To confirm the presence of CCL pathology, determine if meniscal pathology is present, cultures, biopsy if indicated
-therapeutic- removal of CCL remnants, assisted CCL reconstruction, treatment of meniscal injury, joint lavage
Which meniscal injury is injured most frequently?
Medial- firm attachment to tibial plateau, no femoral attachment, caudal pole often wedges between medial femoral condyle and tibial plateau
The lateral is more moveable, has a femoral attachment
What is the most common injury of the medial meniscus?
Bucket handle tear
- radial tear of caudal horn
femoral condyle crushes this area when tibial translates cranially due to the medial tibial ligament holding the meniscus against the tibia
Describe the main functions of the menisci
-load transmission across stifle
-energy absorption
-rotational and varus-valgus stability
-lubrication of joint
-joint congruity
When do meniscal injuries occur?
Either before or after surgery
-90% of time comes along with CCL rupture
T/F: the menisci should always be inspected during surgery for CCL rupture
True- through arthrotomy (not commonly performed anymore), mini arthroscopy or arthroscopy
Does clinical management of meniscal tears ever work?
NOO
What is the meniscal release procedure?
- A method to preserve the grossly normal menisci and remove damaged portions
-may prevent subsequent meniscal injury as it allows the caudal horn of the medial meniscus to remain in the caudal compartment of the joint during cranial translation of the tibia
-transection of caudal tibial ligament
-often leads to DJD over time
what are some important details to tell clients if dog presents for CCL rupture?
- 30-40% of dogs with CCL rupture will rupture the other ligament within 2 years
-increases to 60% if there are already radiographic changes in the uninjured leg
-progressive OA occurs after CCL rupture regardless of treatment method
What is so hard about the treatment of CCL disease?
We don’t know the cause, and we are trying to fix something that cannot be fixed
Describe the slocum technique?
He determined that the tibial thrust was the primary force causing problems in CCL cases
- he came up with the idea with a cranial tibial wedge- cutting a bone to fix a ligament- flattening out the tibial plateau
-later developed into the TPLO
What are the principles behind the TPLO surgery?
Cut the head of tibia, rotate it so it is perpendicular to the forces of the stifle, then plate it
-changes a shear force into a compressive force
What slobodan’s technique?
A TTA
-cut the tibial tuberosity and move it forward to move patellar ligament to be perpendicular to the tibial plateau
What are the main differences between TPLO and TTA?
With TPLO, the tibial plateau is moved to meet the force of the quadraceps
-TTA moves the force to meet the plateau
-TPLO increases joint force, TTA decreases joint force, TPLO disrupts congruency
-TPLO often accompanied by meniscal injury- helps when concurrent with meniscal release
What is the ideal amount of rotation in a TPLO surgery?
6 degrees
If a dogs tibial plateau slope is less than 25 degrees should you do a TTA or TPLO?
TTA
-especially if there is no malalignment
Why is extracapsular not a great technique?
Very far away from the center of motion, even though it addresses a lot of forces of the CCL
What are the muscular actions of the muscles surrounding the stifle?
-biceps are the external rotator
-internal rotators include the popliteus, semitendinosus, gracilus and semimembranosus
-cranial cruciate limits internal rotation
-popliteus tensions the cranial cruciate hence countering tibial thrust
-TPLO weakens the popliteus
Why are TTAs historically not as effective?
Because the training of vets performing the surgery was not as good as for those doing TPLOs
T/F: effective advancement in a TTA surgery is influenced by the cage position
True
What are the advantages to TPLO?
Easier planning, straightforward surgical technique
-repeatable intra and interoperators
-consistent outcome
-predictable clinical results
-versatile
-limb alignment
-low complication rates
Which procedure is associated with more meniscal damage based on the studies?
TTA
T/F: planning for a TTA is more diffcult than TPLO
True- because the technology and research is not as developed
Can you correct a dog with internal rotation with a TPLO? TTA?
Yes, no
What are the 4 cartilages that comprise the larynx?
Epliglottis, arytenoid, thyroid, cricoid
What is the glottic inlet?
The opening of the larynx
What is the action of the cricoarytenoideus dorsalis muscle? What is it innervated by?
When it contracts it opens up the arytenoids, it is innervated by the recurrent laryngeal nerve (branch of the vagus)
What are the functions of the larynx?
Preventing aspiration, controls airway resistance, voice production
What are some of the features of laryngeal paralysis?
Unilateral or bilateral, congenital or acquired, occurs more in males vs females
What are some of the main breeds affected by congenital laryngeal paralysis?
Dalmations, huskies, rottweilers, bouvier des flandres
-onset of clinical signs often less than 1 year of age
