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Tobias full > Vertebral fractures > Flashcards

Vertebral fractures Flashcards

1
Q

What percentage of dogs with vertebral fractures have concurrent injuries?
Thoracic?
Abdominal?
Pelvis or likmb fractures?
Multiple vertebral fractures?

A

45-83% have concurrent injuries
- Thoracic 15 - 35%
- Abdominal 6 - 15%
- Pelvic or limb Fx 14 - 48%
- Multiple vert Fx 15 - 20% (more common in dogs under 15kg)

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2
Q

What is the prognosis for dogs with intact nociception vs without?

A

Positive nociception - functional in upward of 80-90%
Negative nociception 12% waked again but none regained sensation

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3
Q

What is the sensitivty and NPV of radiographs for identifying vertebral trauma?

A
  • Sensitivity 72%
  • Negative predictive value 48%
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4
Q

What radiographic features are associated with poorer outcome in dogs

A

Degree of dislocation or axis deviation of the vertebral column

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5
Q

What are the three compartments of the vertebral column?
How can these help with determining instability of fractures?

A
  • Dorsal compartment - Spinous process, lamina, articular processes, pedicles, dorsal ligamentous complex (supraspinous, interspinous, joint capsule and ligamentum flavum
  • Middle compartment - Dorsal annulus, dorsal longitudinal ligament, dorsal potion of vertebral body
  • Ventral compartment - Remainder of vertebral body, remainder of annulus, nucleus pulposus, ventral longitudinal ligament

If moe than 2 of 3 compartments is compromised, considered unstable

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6
Q

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

A
  • IVD - Rotation, lateral bending
  • Vertebral body - All modes of bending and rotation
  • Articular processes - rotation
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7
Q

How does reperfusion cause secondary spinal cord injury?

A

Liberation of large numbers of oxygen free-radicals, causing destruction of neuronal and glial cell membranes via lipid peroxidation

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8
Q

List the options for stabilisation of the TL column

A
  • Pins and PMMA
  • Locking plates
  • ESF
  • Vertebral body plates
  • Modified segmental fixation
  • Tension band stabilisation
  • Spinous process plating
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9
Q

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

A

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

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10
Q

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

A
  • 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
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11
Q

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?

A
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12
Q

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

A
  • The azygous vein - lies just ventral to the right side of the thoracic vert column
  • Aorta
  • Pleura
  • Lungs
  • Caudal vena cava
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13
Q

What steps can be taken during surgery to minimise the risks of improper pin placement?

A
  • Always make a pilot hole
  • Blunt-tipped pedicle probe to gently advance through cancellous bone
  • Blunt right angel nerve hook to probe and ensure havnt broken through cortex
  • Tip of trocar pin can be cut prior to transcortex
  • Low speed, high torque drill
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14
Q

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

A

May be as low as 50%
CT approaches 100%

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15
Q

What are the general guidelines for locking plate application?

A
  • 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

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16
Q

What plates can be used for spinal process plating?

A
  • 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

17
Q

What is the preferred option if decompression is required?

A

Pediculectomy or mini-hemilaminectoym if possible

18
Q

What is the most common site for cervical Fx?
What is the perioperative mortality rate for cervical fracture fixation?

A

C1 and C2 account for 50 - 70% of cervical fractures
Perioperative mortailty rate 10 - 36%

19
Q

What is the cause of respiratory dysfunction in cervical spinal lesions?

A
  • Phrenic nerve (C5-C7) and intercostal nerves are under the UMN control of the reticulospinal tracts
20
Q

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

A
  • Pins and PMMA
  • Plating
21
Q

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

A

Scoville-Haverfield

22
Q

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

A
  • Narrow pedicles
  • Transverse foramina (containing vertebral artery, vein, nerve)
  • Very narrow safe corridor
23
Q

What is the average ideal insertion angle for C3-C6?
What is the average width of the safe corridor?

A
  • Angle of insertion 34.2 - 37.5
  • Safe corridor ranges from 1mm in a 4 kf doge up to 4.5mm in 50kg dog
24
Q

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

A

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

25
Q

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

A
  • 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
26
Q

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

A
  • 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
27
Q

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

A
  • 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
28
Q

What is the classical LS fracture orientation?

A

Cranioventral displacement of sacrum and small caudoventral wedge of L7 body

29
Q

WHat is unique about the L7 vertebrae?

A

The pedicles are considerable thicker and can accomodate pins or screws

30
Q

What are the landmarks for LS screw placement?

A

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

31
Q

What effect may NSAID have on the CNS?

A
  • May act directly on spinal cord and higher centers to modulate nociception via inhibition of prostaglandin synthesis
32
Q

What is the overall prognosis forspinal fractures?

A
  • No nociception likely around 5%
  • Cervical fractures overall 70% with 13x greater chance of recovery in ambulatory patients
  • TL fractures good prognosis with intact nocicpetion 80-100% with surgery, 85-95% with conservative management
  • LS Fx v. good prognosis. Likely worse prognosis if absent tail tone, external anal sphincter tone, and absent perineal sensation
33
Q

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

A
  • 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

Tobias full (110 decks)

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