Ch 34 Vertebral fractures and luxations Flashcards
causes of vertebral #
affected sites?
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.
SCI
- The severity of overall spinal cord damage reflects both primary and secondary injuries.
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
goals of vertebral # tx
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
assessment
Trauma Assessment and Stabilization
- 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
neuro
neuro assessment
noxious stimulus is a brain-mediated response rather than a reflex (vocalization, turning the head toward, HR/RR)
-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
Imaging
Radiographs
sensitivity and limitations?
prognosis?
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.
Computed Tomography
- modality of choice for diagnosing osseous lesions
Da Costa 2010
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
Magnetic Resonance Imaging
- noninvasive modality that adequately images the spinal cord parenchyma
- 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
- Diagnose sequelae of spinal cord injury such as myelomalacia, syrinx formation, spinal cord tethering, and arteriovenous fistulas.
- 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.
Fracture Biomechanics
Treatment decisions based on the patient’s neurologic status and the biomechanical environment at the site of injury
- 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
three-compartment model
primary downside to this classification system is that the middle compartment is difficult to assess without cross-sectional imaging.
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.
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
- 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.
- true determination of fracture stability can be difficult
- column instability caused by specific fracture types are based on experimental models and may not reflect the clinical situation.
- The force column by various movements are unknown, making the required strength of fixation difficult to estimate.
- When instability cannot be determined > assumed that the fracture is unstable with respect to each of these forces
- Regardless of the method used, our understanding of fracture stability remains incomplete
What forces do the following structures withstand?
- IVD
- Vertebral body
- Articular processes
IVD - Rotation, lateral bending
Vertebral body - All modes of bending and rotation
Articular processes - rotation
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
Medical
true cure for spinal cord injury rests with regenerative therapies
- the most realistic goal for treatment is to minimize secondary spinal cord injury and worsening of spinal cord damage after the primary injury
- Some studies estimate > secondary injury may be responsible for as little as 10% of the overall pathology
- 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)
importance of maintaining spinal cord perfusion
- Hypoxia and ischemia can significantly worsen spinal cord damage; maintenance of normal arterial oxygenation and blood pressure are essential for minimizing secondary spinal cord injury (crystalloid, blood transfusion, vasopressors)
- minimize anesthesia time
Corticosteroids
pathogenesis?
human?
dog RTC?
future tx (3)?
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
Nonsurgical
- Patients with unmanageable pain or worsening neurologic status should be strongly considered for surgical intervention
- 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.
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
- 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
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.
- 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
How can increased abdominal pressure be detrimental when fixing spinal fractures?
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
List the options for stabilisation of the TL column (7)
Pins and PMMA
Locking plates
ESF
Vertebral body plates
Modified segmental fixation
Tension band stabilisation
Spinous process plating
basic fracture sx princliples
- 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.
Pins and Polymethylmethacrylate
- 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.
What are the general guidelines for pin placement in the thoracolumbar vertebrae?
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
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?
- 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
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.
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
Tran 2017: Accuracy and safety of pin placement during lateral versus dorsal stabilization of lumbar spinal fracture-luxation in dogs
sx PMMA and pins
- 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;
What important structures are at risk of being traumatised during pin placement?
The azygous vein - lies just ventral to the right side of the thoracic vert column
Aorta
Pleura
Lungs
Caudal vena cava
basivertebral vein
What is the sensitivity of radiographs in detecting vertebral canal penetration with surgical implants?
May be as low as 50%
CT approaches 100%
ESF
type 1 or 1b configuration.
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.
ESF
cons?
outcome?
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.
What plates can be used for spinal process plating?
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
spinal stapling
Beer 2020: Biomechanical comparison of ex vivo lumbar vertebral fracture luxations stabilized with tension band or polymethylmethacrylate in cats
- 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
What is unique about C2 which must be taken into consideration when planning fracture repair
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
Fractures of the Second Cervical Vertebra in
66 Dogs and 3 Cats: A Retrospective Study
Fenella E. Schmidli 2019
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.
Biomechanical comparison of ex vivo lumbar vertebral
fracture luxations stabilized with tension band or
polymethylmethacrylate in cats
Patricia Beer 2020
limited stability in extension
when using TS for stabilization of thoracolumbar spinal
injuries.
TS technique may be advantageous in less
severe fracture-luxation types not involving the dorsal
compartment, while SP should be chosen
in highly unstable injures in which all compartments
are involved.
Tension band stabilization
resulted in complete or satisfactory neurological
function in 79% (30/38) of all treated cats and dogs, with
none of the cats being affected by implant- or fixationrelated
complications.
In a smaller case series, SP was
applied as a unilateral or bilateral construct in eight cats,
with six of those cats having an excellent to satisfactory
outcome within a 12-month follow-up and only one
experiencing an implant-related complication
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
Sample population: Four greyhound cadavers
Our study confirmed both FHP and 3DPG techniques
were accurate for placement of spinal fixation pins in
canine cadavers. The 3DPG technique reduced intraoperative
technique deviations in pin placement and duration
of pin placement in our study but this technique
requires greater software expertise and equipment for
guide design and manufacturing. The FHP technique
offers a very versatile and safe method of insertion of spinal
fixation pins and can be performed immediately without
potential delays associated with guide design,
printing and delivery. Further studies are required to
confirm our results in clinical cases.
Evaluation of prognostic factors
for return of urinary and defecatory
function in cats with sacrocaudal
luxation
Couper and De Decker 2020
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.
