Ch 34 Vertebral fractures and luxations

Question 1

causes of vertebral #

affected sites?

Answer 1

prevelence in blunt trauma 10%

nontraumatic causes of vertebral column instability include neoplasia, infection, and metabolic disease

Two retrospective studies found the thoracolumbar vertebral column to be most often affected, followed by the lumbar vertebral column

thoracolumbar and lumbosacral junctions are predisposed to injury because of stress concentration at the intersection between relatively mobile and immobile regions of the vertebral column. However, this has not been supported by other studies.

Question 2

SCI

• The severity of overall spinal cord damage reflects both primary and secondary injuries.

Answer 2

Primary injury
- mechanical insult classified as concussion, compression, shearing, laceration, or elongation.
- The spinal cord may be subject to multiple primary injuries because of ongoing instability or persistent compression or both.
- the mechanical insult directly damages neural tissue and induces a cascade of vascular and molecular events, leading to pathology > haemorrhage, ischemia, and oedema.

secondary neuronal injury
- induced and mediated via free radicals, excitatory neurotransmitters, cytokines, inflammatory mediators, ionic dysregulation, and catecholamines.
- This secondary injury may be as damaging as the primary injury itself
Olby 1999: Current concepts in the management of acute spinal cord injury. J Vet Intern Med. 13:399 1999

Question 3

goals of vertebral # tx

Answer 3

goals of management:
> prevent ongoing primary injury to the spinal cord (alignment, stabilisation and decompression)
> mitigate the effects of initial primary and secondary injuries (in combination with supportive care and medical management) help attenuate the cycle of secondary injuries

Question 4

assessment

Trauma Assessment and Stabilization

Answer 4

• 45% to 83% of them have concurrent injuries
• Thoracic 15 - 35% (contusions, rib fractures, and pneumothorax Pulmonary contusions can worsen in the 24 to 48 hour)
• Abdominal 6 - 15% (AFAST)
• Pelvic or limb Fx 14 - 48%
• Multiple vert Fx 15 - 20% (more common in dogs under 15kg)

hemodynamic resuscitation not only supports the cardiovascular system, but also ensures adequate oxygenation and perfusion to the spinal cord
- An efficient and thorough history and physical examination
- A minimum laboratory database should be obtained.
- Sedation and pain relief can aid in immobilization after the initial assessment

Question 5

neuro

neuro assessment

noxious stimulus is a brain-mediated response rather than a reflex (vocalization, turning the head toward, HR/RR)

Answer 5

-neurologic examination is critical for localizing spinal cord lesion(s), detecting concurrent neurologic disease, and prognosticating outcome
- exhibit a range of neurologic deficits similar to those seen in any patient with acute spinal cord injury: postural reaction deficits, paresis, sensory deficits, and alterations in spinal reflexes.
- - One injury may mask those of a second lesion. For example, C6-T2 may result in obscuring of a T3-L3 spinal cord lesion.

The most important prognostic factor is the presence of nociception > absence indicates a poor prognosis for return of function to the affected limbs.

• Relatively few studies have directly examined the prognosis that lack nociception > most of these cases are euthanized on presentation.
• One study reported that 2 of 17 (12%) eventually regained the ability to ambulate. However, these patients did not regain normal spinal cord function
• dogs with intact nociception can achieve good outcomes in upward of 80% to 90% of cases
  McKee 1990

Question 6

Imaging

Radiographs

sensitivity and limitations?

prognosis?

Answer 6

survey radiographs of the entire vertebral column are recommended to rule out multiple injuries
awake and remaining immobilized in lateral recumbency on a radiolucent board > maintain muscular support of the vertebral column, helping to splint dynamic instability.
- Oblique and dorsoventral views can be performed by changing the angle of the beam head.
- Radiography has limited sensitivity (72%) and negative predictive value (48%)
- poor at detecting fractures in the middle and dorsal compartments
- not sensitive for detecting the presence of fracture fragments within the vertebral canal or spinal cord compression > does not detect dynamic disease
The combination of 100% displacement and absence of nociception warrants a grave prognosis for recovery.

Myelography
- advantage over plain radiographs that it can illustrate spinal cord swelling or spinal cord compression due to intervertebral disc material, hemorrhage, or bone fragments.

Question 7

Computed Tomography

• modality of choice for diagnosing osseous lesions

Da Costa 2010

Answer 7

ability to reconstruct images in alternative planes
- more accurate than radiography in diagnosing multiple sites of injury, and it is particularly valuable in delineating the extent of damage
- Although soft tissue structural integrity may not be completely assessed, CT is helpful in evaluating the dorsal, middle, and ventral compartments

• identify mineralized intervertebral disc material, extradural hemorrhage, and vertebral canal narrowing > require decompression. Sensitivity improved by myelography
  Dennison 2010
• greater spatial resolution than MRI, which is generally thought to allow better imaging of bone.
• limits the ability to assess parenchymal changes
  CT and MRI may best be used in a complementary fashion to evaluate the osseous and soft tissue components
• good degree of accuracy to evaluate implant placement postoperatively, with respect to the vertebral canal.
  Hettlich 2010

Question 8

Magnetic Resonance Imaging
- noninvasive modality that adequately images the spinal cord parenchyma

Answer 8

• Reliably detect edema, hemorrhage, cavitations, and lesion length within the spinal cord.
• provide useful information regarding the paraspinal soft tissues, intervertebral discs, and ligamentous supportive structures
• • Diagnose sequelae of spinal cord injury such as myelomalacia, syrinx formation, spinal cord tethering, and arteriovenous fistulas.
    Bagley 2006
• Relatively few reports dogs and cats. In canine > intramedullary T2-weighted signal hyperintensity have been associated with more severe presurgical neurologic grade and worse functional outcome. These studies have not been performed in dogs with vertebral fractures, luxations, and subluxations,
• • Cost of MRI greater, Image acquisition time for MRI is longer than for other imaging modalities, patients may have to be moved from their initial immobilization.
• In human > parenchymal hemorrhage, spinal cord transection, and increased lesion length are all associated with less favorable neurologic outcomes. Lack of MRI signal abnormality within the spinal cord is associated with superior functional recovery > the neurologic examination findings are still the single best predictor of outcome.

Question 9

Fracture Biomechanics

Treatment decisions based on the patient’s neurologic status and the biomechanical environment at the site of injury

Answer 9

• Surgery is indicated for compressive or unstable lesions.
• Each segmental spinal column unit is composed of bony and soft tissue structures that contribute to its stability.
• structures are constantly subject to external forces>dorsoventral and lateral bending, torsion, shear, and axial loading.
• Several schemes exist to help classify stability of fractures, but can only serve to guide treatment

Question 10

three-compartment model

primary downside to this classification system is that the middle compartment is difficult to assess without cross-sectional imaging.

Answer 10

dorsal compartment
-spinous processes,
vertebral laminae,
articular processes,
vertebral pedicles, and
dorsal ligamentous complex (supraspinous, interspinous, joint capsule, ligamentum flavum).

middle compartment
dorsal longitudinal ligament, the
dorsal portion of the annulus fibrosus,
dorsal portion of the vertebral body—essentially the floor of the vertebral canal.

ventral compartment
remainder of the vertebral body,
the lateral and ventral portions of the annulus fibrosus,
the nucleus pulposus,
ventral longitudinal ligament

• If more >1 compartments is compromised, the vertebral column is considered unstable and surgical intervention is indicated.

Question 11

simpler classification scheme > the intervertebral disc, the vertebral body, and the articular processes. As presented in Wheeler and sharp

IVD most important contributor rotational stability
Shires 1991

Answer 11

• • intervertebral disc contributes to stability in lateral bending
• If compromised IVD, an intact vertebral body provides some buttress stabilization in extension and flexion.
• Fracture of the vertebral body destabilizes in all modes of bending and rotation. Even with an intact intervertebral disc and articular processes > vertebral body fractures are very unstable.
• fractures of the articular processes, even bilaterally, can be relatively stable.
• Injuries with failure of >1 components—intervertebral disc, vertebral body, or articular process—should be considered very unstable, regardless of the degree of displacement seen on imaging.

Question 12

• column instability caused by specific fracture types are based on experimental models and may not reflect the clinical situation.
• The force on column by various movements are unknown, making the required strength of fixation difficult to estimate.

Question 13

What forces do the following structures withstand?
- IVD
- Vertebral body
- Articular processes

Answer 13

IVD - Rotation, lateral bending
Vertebral body - All modes of bending and rotation
Articular processes - rotation

Question 14

Treatment
Initial treatment of the patients > stabilization of the patient. Subsequent treatment of the vertebral column injury typically consists of a combination of medical and surgical therapies.
- Decisions > based on neurologic status + biomechanical characteristics of the fracture or luxation.
- Sx goal > realignment and stabilization of the vertebral column and decompression of the spinal cord.
- Medical management > minimizing secondary spinal cord injury

Question 15

Medical
true cure for spinal cord injury rests with regenerative therapies

Answer 15

• minimize secondary spinal cord injury and worsening after the primary injury
• experimental models of a concussive injury > restoration of walking requires as few as 5% to 10% of peripherally located axons to be intact (so, saving even small % beneficial)
• maintaining spinal cord perfusion (Hypoxia and ischemia worsen SCI); normal arterial oxygenation and blood pressure (crystalloid, blood transfusion, vasopressors)
• minimize anesthesia time

Question 16

Corticosteroids

pathogenesis?
human?
dog RTC?
future tx (3)?

Answer 16

use remains controversial, and their exact mechanism of action is unclear
- Acute spinal cord injury results in decreased blood flow to neural tissues.
- Reperfusion results in liberation of oxygen-derived free radicals.
- These free radicals cause destruction of neuronal and glial cell membranes via lipid peroxidation—a major component of secondary spinal cord injury
- It is believed that the primary protective effects of corticosteroids are due to their antioxidant properties.
- Methylprednisolone sodium succinate > demonstrated efficacy in controlled clinical trials in human beings BUT Evidence-based reviews have concluded that evidence is insufficient to support the use succinate as a standard treatment in acute spinal cord injury

• A multicenter, prospective, randomized, placebo-controlled clinical trial failed to show any benefit of methylprednisolone sodium succinate administration for dogs with severe acute spinal cord injury dt IVD. No difference in outcome measures
  Olby 2016

treatments that hold promise are
- metalloproteinase inhibitors
- glial cell and stem cell transplantation
- electrical field gradients to influence and guide axon regrowth > unknown clinical benefits at this stage

Question 17

Nonsurgical

• Patients with unmanageable pain or worsening neurologic status should be strongly considered for surgical intervention

Answer 17

• Cage rest is recommended for all patients +/- splint
• Usually 4 to 6 weeks of rest
• Nonsurgical treatment avoids complications associated with anesthesia, manipulation of the vertebral column, and surgical implants.
• If costs of multiple sedations, bandage changes, and treatment of complications are included in the estimate, costs may be equal to the cost for surgery.
• external coaptation may provide support for an unstable vertebral column > minimal ability to realign. Nonetheless, several studies report good outcomes for patients managed with nonsurgical treatment alone
• Some studies have shown equal long-term outcomes for recovery from spinal trauma in nonsurgically treated patient
• Objective evaluation of surgical versus nonsurgical treatment is impossible based on current data. No randomized study has directly compared and inherent biases of patient selection make retrospective studies unsuitable for this comparison.

Question 18

External coaptation
- The best candidates for coaptation > smaller animals with minimal neurologic dysfunction or at least those with normal nociception, an intact ventral buttress, and lack of concurrent thoracic, abdominal, or pelvic injuries

Answer 18

• External coaptation requires intensive management to avoid complications such as decubital ulcers, urine scalding
• displaced or malpositioned bandage or splint can act as a fulcrum or pendulum, worsening vertebral column alignment
• For lumbar > entire pelvis should be included
• Cervical > from the level of the eyes to the midthorax.
• maintain external splints for a minimum of 4 weeks, with an additional 4 weeks of cage rest

Question 19

Surgical
Surgery is the most reliable way to stabilize the vertebral column and is perhaps the only way to accurately align the vertebral column and decompress the spinal cord.

Answer 19

• Some studies report that outcomes for patients treated surgically versus those treated nonsurgically are equivalent.
  Bruce 2008, Hawthorn 1999, Selcer 1991
• These comparisons are not based on randomized, controlled studies and therefore are not reliable

recommendations are based largely on experimental, non–outcomes-based data, surgeon opinion and experience, and owner preference.
- The authors
> paretic animals with intact nociception
> worsening neurologic status
> unstable
> spinal cord compression.

• Surgery also may be indicated for animals lacking nociception whose owners are willing and able to provide long-term care for a paralyzed, incontinent animal

Question 20

How can increased abdominal pressure be detrimental when fixing spinal fractures?

Answer 20

Increased intraabdominal pressure (ie. from towels placed for positioning), can increase pressure within the low pressure, thin-walled internal vertebral venous plexus resulting in increased haemorrhage during surgery
This venous engorgement can also lead to decreased cord perfusion when combined with arterial hypotension

Question 21

List the options for stabilisation of the TL column (7)

Answer 21

Pins and PMMA
Locking plates
ESF
Vertebral body plates
Modified segmental fixation
Tension band stabilisation
Spinous process plating

Question 22

basic fracture sx princliples

Answer 22

• level of the costal fovea of the transverse process in the thoracic vertebral column or the transverse processes in the lumbar vertebral column.
• The affected articulation is identified and reduced.
• Reduction and temporary manual stabilization can be provided by distraction via towel clamps placed at the base of the spinous processes of the vertebrae adjacent to the affected articulation. Movements should be slow and deliberate
• Reduction is often most easily evaluated by assessing alignment of the articular surfaces of the zygapophyseal joints
• Once reduction is achieved, Kirschner wires can be used for temporary stabilization until definitive fixation > across the zygapophyseal joints.

Question 23

Pins and Polymethylmethacrylate

Answer 23

• With subluxations and luxations as well as with many fractures, the pins can be inserted in consecutive vertebrae
• For midbody or comminuted vertebral fractures, it may be necessary to span the fractured vertebra

Their strength in bending is also characterized by the area moment of inertia and is proportional to radius to the fourth power > a small increase in pin radius causes a large increase in bending strength; the largest reasonable pin size should be used.

• 4 pin + PMMA constructs have been shown to be as stiff in extension, flexion, and rotation as ex vivo, intact vertebral columns in biomechanical testing.

Question 24

What are the general guidelines for pin placement in the thoracolumbar vertebrae?

Answer 24

Positive profile threaded pins
20-25% of vertebral body diameter
Entry point at accessory process for thoacic, between base of transverse process and accessory process for lumbar
Aimed to exit transcortex in region of end plates to maximise bone purchase
Angled 30-60 degrees from sagittal plane

Question 25

What are the reported recommened pin insertion angles for the thoracic and lumbar vertebrae as reported by Wong et al, Wheeler et al, Watine et al?

Answer 25

- Preoperative CT or MRI images can be useful for measuring insertion angles and for intraoperative reference - Fluoroscopic guidance resulted in fewer potentially life-threatening complications in a cadaver study. Complications in this study were primarily pulmonary and vascular injuries Wheeler 2002

Question 26

Hall 2015: Bending strength and stiffness of canine cadaver spines after fixation of a lumbar spinal fracture-luxation using a novel unilateral stabilization technique compared to traditional dorsal stabilization.

Answer 26

more horizontal angle via a lateral approach between the longissimus lumborum and iliocostalis lumborum muscles > equal strength to dorsal decreased dissection required and ease of closure Pins were directed away from the spinal canal at an angle 70–80° from the dorsal plane Tran 2017: Accuracy and safety of pin placement during lateral versus dorsal stabilization of lumbar spinal fracture-luxation in dogs

Question 27

sx PMMA and pins

Answer 27

- Meticulous pin insertion technique can help to minimize risk for vertebral canal penetration or iatrogenic organ damage and can maximize the strength of the construct. - Pilot holes should always be utilized > minimizes risk for bone thermal necrosis and bone microfracture - - probe is inserted into the cancellous bone. - Excessive bleeding may indicate > epidural hemorrhage - - low-speed high-torque drill, pins arranged in a cruciate pattern. - Bending the pin enables an increased amount of pin-cement interface, bent by using two hand-held bending irons - additional longitudinal pins can be added as rebar - should be irrigated while curing - In the dog, neglecting to engage the ventral vertebral body cortex may significantly reduce pin pull-out strength as well as breakout strength;

Question 28

What important structures are at risk of being traumatised during pin placement?

Answer 28

The azygous vein - lies just ventral to the right side of the thoracic vert column Aorta Pleura Lungs Caudal vena cava basivertebral vein

Question 29

What is the sensitivity of radiographs in detecting vertebral canal penetration with surgical implants?

Answer 29

May be as low as 50% CT approaches 100%

Question 30

ESF | type 1 or 1b configuration.

Answer 30

External Skeletal Fixation described in a small number of clinical cases, using both open and closed application techniques. - With the open technique the principles of pin application are similar to pin/pmma - Closed application technique requires decreased tissue dissection and disruption of paravertebral supportive soft tissue structures - In a study using canine cadavers, closed technique with fluoroscopic guidance showed a decreased likelihood of compromising thoracic pleural or vascular structures. Type 1b using spinal arches was as strong as eight pin/polymethylmethacrylate constructs in biomechanical testing.

Question 31

ESF cons? outcome?

Answer 31

Disadvantages: - postoperative pin care and construct maintenance + the risk for pin tract infection/inflammation. - Inadvertent, traumatic deinstrumentation of external skeletal fixators has been reported. - A small clinical study reported that mean time until fixator removal was 105 days > 16 weeks in a more recent study.

Question 32

**Bitterli 2021**: Minimal Invasive Fluoroscopic Percutaneous Lateral Stabilization of Thoracolumbar Spinal Fractures and Luxations Using Unilateral Uniplanar External Skeletal Fixators in Dogs and Cats

Answer 32

type 1a ESF can be successfully and minimally invasively applied to fractures and luxations of the spine in dogs and cats with minimal major complications. successfully removed 8 to 16 weeks post-surgery

Question 33

Locking Plates

Answer 33

- SOP and the locking compression plate LCP have been described in clinical and biomechanical studies - Biomechanical advantages: - more similar to those of an external skeletal fixator or pins/polymethylmethacrylate than those of a traditional bone plate (single beam construct) - Failure of locking plate constructs requires implant breakage or failure of large areas of bone in shear, rather than axial screw pull-out, as is seen with traditional bone plates. - The string of pearls plate is a locking bone plate that can be contoured in multiple planes - unilateral > advantages in simplicity of application and diminished morbidity as compared to a bilateral construct.

Question 34

What are the general guidelines for locking plate application?

Answer 34

Pin insertion at angles similar to those recommended for pin placement (30-60) Bilateral plating with minimum of three screws per vertebra Contoured to minimise lever arm while allowing offset to avoid interfering with neurovascular structures Penetration of transcortex is not essential Can also place a unilateral plate on the lateral vertebral bodies - not as strong as 4pin-PMMA construct but stronger than intact spine ex-vivo. Bilateral plating is similar in strength to 4pin-PMMA constructs

Question 35

What plates can be used for spinal process plating?

Answer 35

Bilateral metal Auburn spinal plates Bilateral plastic Lubra plates (38% implant removal due to pressure necrosis of spinal processes) Nuts and bolts passed between (plastic plates) or through (metal plates) the spinal processes to connect them

Question 36

spinal stapling Beer 2020: Biomechanical comparison of ex vivo lumbar vertebral fracture luxations stabilized with tension band or polymethylmethacrylate in cats

Answer 36

- Spinal stapling and modified segmental fixation utilize steel pins placed transversely through holes at the base of the spinous processes cranial and caudal to a fracture/lux and bent 90 degrees to lie on the dorsal laminae, additionally secured to the vertebral column via encircling orthopedic wire. - - used with careful case selection > does not directly stabilize ventral compartment injuries, spinous process relatively weak. - less costly and technically easier than other procedures. However, this technique requires exposure and immobilization of at least five or six vertebrae. - failures caused by device pull-out, spinous process fracture, or ischemic necrosis of the spinous process. - Surgeons should be aware of the limited stability in extension provided by TS when it

Question 37

Decompressive Procedures Spinal cord compression plays a role in the pathology of all vertebral fractures, luxations, or subluxations.

Answer 37

relieved by realignment, distraction, and stabilization. Extradural compression may be due to hemorrhage/hematoma, intervertebral disc material, or bone fragments.. - Hemilaminectomy is preferred over dorsal laminectomy, because hemilaminectomy results in less destabilization of the vertebral column. - Removal of the articular processes results in significant decreases in rotational stability in cadaver models.

Question 38

Cervical Vertebral # most common site? why?

Answer 38

The C1 and C2 vertebrae appear to be disproportionately affected, accounting for 50% to 70% of cervical fractures. Static-kinetic relationship between the relatively stable caudal cervical vertebral column (C3-C7) and the relatively dynamic cervicocranium (skull, C1, C2) > Stress concentration

Question 39

perioperative mortality cause? wheer phrenic n. arise?

Answer 39

perioperative mortality ranges from 10% to 36%. - Cause of death in most of these cases has been indicated as cardiopulmonary arrest. - Respiratory dysfunction has been documented (resp muscle failure, disrupted feedback mechanisams) - phrenic nerve arising from C5-C7 > Cervical lesions located cranial to the origin of C5 nerve roots could affect function of the diaphragm and intercostal muscles - unclear whether mortality due to severity of the initial injury or complications of anesthesia and/or surgery

Question 40

**Schmidli 2019**: Fractures of the Second Cervical Vertebra in 66 Dogs and 3 Cats: A Retrospective Study | retrospective case series.

Answer 40

young dogs, deficits often relatively mild. Generally, very good prognosis. perioperative mortality lower than previously reported. 37/ 69 surgery 27/69 conservative therapy 5/69 were immediately euthanatized. 52/58 showed ambulatory recovery (23/25 conservatively and 29/33 surgically treated)

Question 41

What are the main two options for fixation of cervical vertebral Fx?

Answer 41

Pins and PMMA Plating

Question 42

What retractor is especially associated with over reduction of cervical spinal Fx?

Answer 42

Scoville-Haverfield

Question 43

What anatomical features make implant placement in the cervical spina particularly complex?

Answer 43

Narrow pedicles Transverse foramina (containing vertebral artery, vein, nerve) Very narrow safe corridor

Question 44

What is the average ideal insertion angle for C3-C6? What is the average width of the safe corridor? | based on preoperative cross-sectional imaging of that patient.

Answer 44

Angle of insertion 34.2 - 37.5 Safe corridor ranges from 1mm in a 4 kg dog up to 4.5mm in 50kg dog 20-35 - Several experimental studies show violation of canal of foramen frequently occurred (up to 90%) based on these angles, in general safe corridors are narrow and varies amongst animals and vertebrae Corlazzoli 2008

Question 45

What is unique about the C7 vertebra? How does this aid implant placement?

Answer 45

It lacks a transverse foramen - Implant placement is more forgiving and average safe insertion angle 47.5 degree

Question 46

What options are there for stabilising fractures of the cervical spine to avoid the risks of transverse foramen trauma

Answer 46

Transverse process screws and PMMA Ventrally applied monocrotical screw and PMMA with three screws per vertebra (biomechanically comparible to bilateral 4pin-pMMA construct) 9.7% penetrated the vertebral canal

Question 47

What is unique about C2 which must be taken into consideration when planning fracture repair

Answer 47

Thin central vertebral body providing little purchase for implants Construct stability should be increased by croseeing the AA joints with the implants (directed craniolateral, 30-35deg from sagittal plant, 40-45 degree in transverse plane, aiming for a point just medial to alar notch and transverse foramen of C1) Pins in caudal C2 can be directed laterally at 30-50 degrees

Question 48

Espadas 2018: Optimal safe implantation corridors in feline cervical vertebrae (C2–T1): CT study in 16 domestic shorthair cats

Answer 48

- Cervical vertebral safe corridors in cats are narrow and differ to those reported in dogs. Safe corridors are located in the caudal third of C2 and cranial third of the C3–T1 vertebral bodies. - Current recommendations for implant sizes should be reviewed, as 1.5–2 mm implants would be oversized for bicortical implantation in most of the feline cervical vertebrae

Question 49

What is an alternative for pins and PMMA for stabilisation of cervical Fx?

Answer 49

Locking plates! (Human cervical spin locking plate (CSLP, Synthes), human maxillofacial locking plate (ComPack UniLock, Synthes), veterinary locking plates (SOP, Orthomed)(LCP, Synthes) A standard 3.5mm LCP applied ventrally using monocortical screws provides similar stability to 4pin-PMMA constructs. All pins had purchase of over 50% vertebral body

Question 50

- The true frequency and consequence in clinical cases are unknown > unclear how important minor violations - - Estimates of the rate of pedicle screw misplacement in human beings are as high as 25%; however, most of these cases are asymptomatic

Question 51

Locking plate fixation - Several plating systems have been used in clinical cases, including a human and vet locking plate (SOP) > many look at its use for CSM not fracture models

Answer 51

- Clinical outcomes in these reports are good. The primary complication reported is implant loosening, which most often is asymptomatic. - PROS:  sustained strength without the need for bicortical  minimizes concerns over iatrogenic trauma to neurovascular.  heat generation and potential tissue damage, release of circulating methylmethacrylate monomer, and hypersensitivity reactions - CONS; o implant loosening and screw pull-out may occur as a result of shearing of bone >“bone slicing” and may be of increased concern when screws do not engage a trans-cortex. o Use of monocortical screws in vertebral fracture?

Question 52

What is the classical LS fracture orientation?

Answer 52

Cranioventral displacement of sacrum and small caudoventral wedge of L7 body

Question 53

WHat is unique about the L7 vertebrae?

Answer 53

The pedicles are considerable thicker and can accomodate pins or screws

Question 54

What are the landmarks for LS screw placement?

Answer 54

L7 pedicle screws - Enter just caudal to the base of the cranial articular process - Directed ventrally, as well as slightly cranially and medially Sacral - Enter just caudal to cranial articular process - Placed ventrally, slightly ventrolaterally or slightly ventromedially - Caudal pins may engage ilium by directing caudoventrolaterally through sacrum and across SI joint and into long axis of the body of the ilium

Question 55

Fractures/Luxation Lumbosacral Articulation - less severe neurologic deficits have a better prognosis > may have up to 100% displacement without major neurologic deficits; degree of dorsoventral vertebral displacement should not be used as a prognosticator

Answer 55

- Many dogs nonambulatory primarily because of severe pain rather than neurologic dysfunction. Clinical signs: - such as sensory and motor deficits in sciatic nerve, urinary and fecal incontinence, perineal and tail hypalgesia/anesthesia, and absent tail and external anal sphincter tone. - absent external anal sphincter tone, absent perineal sensation, or pelvic limb paresis, warrant a guarded prognosis for return to full function.

Question 56

LS PMMA

Answer 56

PMMA - with pins or screws/polymethylmethacrylate resist significant bending loads placed and enable rapid bone healing - Four-pin/polymethylmethacrylate used with good clinical results. - These constructs consist of two pins engaging the L7 vertebra and two pins engaging the sacrum or sacrum and ilium. - - Biomechanical studies have described six-pin/polymethylmethacrylate constructs

Question 57

**Nel 2015:** Biomechanical comparison between pins and polymethylmethacrylate and the SOP locking plate system to stabilize canine lumbosacral fracture-luxation in flexion and extension

Answer 57

- SOP and pin-PMMA fixation of simulated L7-S1 fracture-luxation resulted in similar biomechanical behavior of the L7-S1 junction

Question 58

Pedicle screws generally applied using bilateral two-screw/bar constructs

Answer 58

 cranial implants inserted into the intact pedicles and body of the L7 vertebra, and  caudal implants inserted into the sacrum, tuber sacrale, or body of the ilium  significant comminution, implants can be placed in the pedicles and body of the L6 vertebra and sacrum, spanning the L7 vertebra.  vertebral column, pelvis, and pelvic limbs rest in a neutral position, representative of weight-bearing stance.  The sacrum typically appears telescoped beneath the L7 vertebra, obscuring the interarcuate space.  Reduction with periosteal elevator, hemostatic forceps, or Senn retractor placed carefully in the interarcuate space to lever the sacrum  Adequacy of reduction > zygapophyseal joint. temporarily maintained by placing K-wires across each L7-S1 joint.  Landmarks for placement of pins or screws in the L7 vertebra have been described (WEH 2007)  Placing pins across the sacroiliac joint decreases range of motion at that joint; long-term implications of doing this are not known

Question 59

alternative Tx for LS #

Answer 59

Percutaneous transilial pinning - treatment of seventh lumbar vertebral body fracture > more recent 2016 study shows using 2 offers good clinical outcome (as compared to older reports) still no align L7 body fracture Decompressive dorsal laminectomy - easily performed in conjunction with PMMA/SOP/rod > An intact dorsal lamina is not needed for stability of these constructs. - The nerve roots at the laminectomy site should be protected with Gelfoam or fat graft before polymethylmethacrylate placement to prevent thermal injury

Question 60

post-op vertebral # care

Answer 60

Surgical stabilization decreases pain treated preemptively to avoid central sensitization or “windup.” - Opioids cause ileus and nausea. They also may cause dose-dependent respiratory depression (Caution in cranial cervical lesions) - Opioids can cause urinary retention - NSAID > Evidence also indicates that may act directly on the spinal cord and higher centers. Adverse effects primarily as the result of simultaneous inhibition of constitutive COX-1, required for normal organ homeostasis - spinal cord injury to exhibit some type of gastrointestinal irritation means that nsaids should be used with caution. - Recumbent on soft, well-padded bedding. - Regular attention must be paid (nursing, washing, turning) to prevent pulmonary atelectasis, pneumonia, and decubital ulcers - physical therapy - The bladder must be managed to avoid ongoing distention and detrusor muscle atony from overdistention. - check for uti

Question 61

Complications

Answer 61

- iatrogenic damage - Vascular complications > vertebral arteries and veins, aorta, and azygos - - Pneumothorax - - Failure of fixation> neutralize forces for each affected compartment. When in doubt, fixation that stabilizes all three - - Inadequate reduction - - Implant-associated infection - - Excessive callous formation at the fracture site can cause spinal/nerve impingement

Question 62

prognosis

Answer 62

no nociception - The chance of regaining ambulation for animals that lack nociception must be considered low (5%) - few studies have documented outcomes past 1 month post injury - - Return of motor function and ambulation may take between 4 and 6 months - severely paretic and/or remain with a severe general proprioceptive ataxia, with urinary and/or fecal incontinence - unclear whether locomotion in these animals represents “spinal walking

Question 63

cervical px

Answer 63

- Prognosis is good. Few dogs with cervical lesions seem to present with absent nociception ambulatory on presentation have a 13 times greater chance of a functional outcome than dogs with nonambulatory return to functino 70%

Question 64

thoracolumbar px

Answer 64

- injuries carry a good prognosis, as long as nociception is intact. - Older studies report functional recovery in 80% to 100% of surgically treated - Conservative management has resulted in functional outcomes for 85% to 95% of patients (Animals that lack nociception carry a worse prognosis) - Outcomes appear similar for cats and dogs. Bruce 2008 - In fractures occurring in the more cranial part of the vertebral column, the degree of vertebral displacement is negatively correlated with the expected prognosis Bali 2009

Question 65

lumbosacral Px

Answer 65

- have a very good prognosis. - Many may have a good long-term outcome without surgery. For patients with significant pain or neurologic impairment, improvements in function and comfort are hastened dramatically by surgical stabilization - With increasing neurologic deficits, prognosis worsens. Incontinent patients with absent tail tone, external anal sphincter tone, and absent perineal sensation probably have a worse prognosis. Weh 2007

Question 66

Primary stabilisation for tail avulsion in 15 cats J. Caraty

Answer 66

Retrospective 15 no VMF and 8 urinary incontinent. Sx > 11 regain VMF within 14 to 90 days (mean 39 days). 5/8 recovered urinary continence within 1 month. comparison study required to determine if sx superior to conservative Tatton et al . ( 2009 ) 4 of the 10 cats without tail base pain sensation did not recover control of urination by day 30 tail amputation > wait until reassess 90 to 150 days Medical treatment > 72% recover VMF when pain perception at the base of the tail Neurotmesis > displacement of 100% is apparent on radiographs

Question 67

Fractures of the Second Cervical Vertebra in 66 Dogs and 3 Cats: A Retrospective Study Fenella E. Schmidli 2019

Answer 67

multi-institutional retrospective case series. Fractures of the axis commonly occur in young dogs. In many cases, neurological deficits are relatively mild. Generally, animals with a fractured axis have a very good prognosis for functional recovery. The risk of perioperative mortality is considerably lower than previously reported.

Question 68

Repair of lumbosacral fracture–luxation with bilateral twisted string-of-pearls locking plates Segal 2018

Answer 68

Six animals (four dogs and two cats) were Stabilisation was achieved using bilateral string-of-pearls plates attached to the lateral aspects of the vertebral body cranial to the fractured vertebra and the iliosacral joints. Reduction of the luxation was assessed under fluoroscopy. Outcome and complications were evaluated 24 hours, 6 weeks and 6 months postoperatively.

Question 69

Computed tomography evaluation of proposed implant corridors in canine thoracic vertebrae Schmitt 2021

Answer 69

The average corridor angles were: T1 = 38 , T2 = 32 , T3 = 27 , T4 = 26 . T5-T9 angle ranged from 23  to 24 . challenging from T1-T4 – variation and regional anatomy

Question 70

Minimal Invasive Fluoroscopic Percutaneous Lateral Stabilization of Thoracolumbar Spinal Fractures and Luxations Using Unilateral Uniplanar External Skeletal Fixators in Dogs and Cats Thomas Bitterli1

Answer 70

minimally invasive stabilisation with Type 1a ESF in dogs and cats - fluoro-guided percutaneous lateral stabilisation - insertion angle 75-90° (lateral placement as per Hall 2015) - 10/14 cases achieved full recovery - complications: hemothorax, pneumothorax, pin tract exudate and pin loosening

Question 71

Biomechanical comparison of ex vivo lumbar vertebral fracture luxations stabilized with tension band or polymethylmethacrylate in cats Patricia Beer 2020

Answer 71

tension band stabilization of lumbar vert fracture luxation model vs screw/PMMA in cats - dorsal tension band construct with bent U-shaped K-wire and cerclage to dorsal spinous processes - screw-PMMA: bilateral horizontal trans-vertebral body screws, bilateral PMMA column - insertion trajectory 10° to horizontal (sagittal plane) - tension band → comparable stability to screw/PMMA limited stability in extension when using TS for stabilization of thoracolumbar spinal injuries. SP should be chosen in highly unstable injures in which all compartments are involved. only 1 complications

Question 72

Thoracolumbar Spinal Stabilization with Three Dimensional-Printed Drill Guides and Pre-Contoured Polyaxial Bone Plates Gilman 2023

Answer 72

Retrospective study, five client-owned dogs. Results Three-dimensional-printed patient-specific drill guides and drill stops allowed safe drilling and screw placement in all of the cases, with (i) 84% of the screws graded as I (ideal placement) in spine kyphosis stabilization

Question 73

Accuracy of pin placement in the canine thoracolumbar spine using a free-hand probing technique versus 3D-printed patient-specific drill guides: An ex-vivo study Ronan A. Mullins 2023

Answer 73

Four cadavers. free-hand probing technique successfully applied for safe application of pins - free-hand probing by gradual extension of drill hole, guided by goniometry, ensuring not palpable canal breach - no lag time to fabrication of 3DPG for spinal fracture/luxation - mildly increased rate of canal violation and technique deviation - no cases of full breach in either group.

Question 74

Outcomes of nine cats with urinary retention after sacrocaudal luxation managed with long-term urinary diversion **Garcia 2021** Temporary or permanent urination impairment is reported in more than 50% of cats with SCL | tone in the internal urethral sphincter via hypogastric n. may be intact

Answer 74

case series 9 cats. Sacrocaudal luxation with urinary retention. tone in the internal urethral sphincter via hypogastric n. may be intact All cats recovered normal micturition spontaneously tube dislodgement, occurred in two cats Two-thirds full urinary function < month one third > 1 month

Question 75

Evaluation of prognostic factors for return of urinary and defecatory function in cats with sacrocaudal luxation Couper and De Decker 2020

Answer 75

Seventy cats were included. Fifty-five of 61 cats (90%) regained voluntary urinary function No significant associations were found between urinary outcome and anal tone, perineal sensation, tail base sensation, degree of displacement. agreement with previous studies, neurological grade is the most important prognostic indicator for cats with sacrocaudal luxation. Determination of the severity of neurological signs can also aid in advising owners the time frame in which urinary function is expected to return. Faecal incontinence may be a more important prognostic factor than previously suspected.

Question 76

Comparison of Cervical Stabilization with Transpedicular Pins and Polymethylmethacrylate versus Transvertebral Body Polyaxial Screws with or without an Interbody Distractor in Dogs Marinho 2022

Answer 76

Ten canine cervical vertebral columns (C2–T3) were used. Four models (intact, transvertebral body polyaxial screw with interbody distractor [polyaxialþ distractor], transvertebral body polyaxial screw without interbody distractor [polyaxial  distractor] and bicortical transpedicular pins/polymethylmethacrylate [pin-PMMA Conclusion Stabilization obtained with transvertebral body polyaxial screws was comparable to that from the well-established bicortical pins/PMMA construct. Association of an intervertebral distractor did not change AROM of the polyaxial screw constructs.

Question 77

MRI has limited agreement with CT in the evaluation of vertebral fractures of the canine trauma patient Gallastegui 2019

Answer 77

MRI may be able to detect the presence of fractured vertebrae, it is not able to replace CT for the complete evaluation of the traumatized spine and documentation of fracture morphology.

Question 78

Samer 2021 – accuracy of image-guided free-hand pin placement - mean deviations: entry point 3.1mm, exit point 6.3mm, angle 7.6° - max deviations: entry point 6.3mm, exit point 11.0mm, angle 16.4° - implant corridors safe even with deviations - lateral and caudal deviations more common | VCOT

Question 79

Spinal Neuronavigation for Lumbar Plate Fixation in Miniature Breed Dogs Papacella-Beugger 2024

Answer 79

experimental cadaveric study in five miniature breed dogs. CT guided. 4-hole locking plate with four 2.0-mm locking screws 85% (17/20), screws were placed appropriately. novice surgeon resulted in surgical safe plate placement in four of the five cadavers. Therefore, we judge the method as promising

Question 80

Ex vivo comparison of pin placement with patient-specific drill guides or freehand technique in canine cadaveric spines Guevara 2023

Answer 80

3D-printed drill guides for pin placement in TL spine more accurate than freehand - 87.5% acceptable vs 69.8%, T10-T11 more likely to have unacceptable placement - 3D-PG → 64.6% grade I pin vs 48.3% free-hand