33.LS_spine Flashcards
termination of the spinal cord in large dogs, average dogs, and small dogs/cats
large to giant breeds–L4dogs < 15 kg –L6toy breeds/cats–L7dural sac continues for 1-2 cm caudally
pathological changes associated with degenerative LS stenosis and contributing spinal compression (figure 33-3)
- buldging disc or annulus fibrosis2. thickening of dorsal annulus fibrosis3. mechanical instability with sublux/lux L7-S1 (can see spondylosis deformans)4. osteophyte around article processes/joints5. thickened joint capsule6. thickened ligamentum flavum
define intermittent claudication
clinical signs associated with LS diseaseparoxysmal manifestations consistent with lower back or limb cramping, pain or weakness resulting from vascular compromise or compression of nerve roots of the caudal equina
define patellar pseudohyperreflexia
dog with sciatic nerve deficits should be LMNBUT extensor or UMN nerves still intact leading to falsely exaggerated patellar reflex bc of loss of antagonistic muscle groups to the extensor m group
ddx for LS disease
- discospondylitis2. meningitis/meningomyelitis3. traumatic–fracture/luxation4. anomaly/malformation5. ortho dx –hips, ccl, mpl, iliopsoas, gracilis myopathy6. neoplasia7. polymyositis8. polyarthritis9. polyneuropathy10. degenerative myelopathy11. ischemic neuropathy12. prostatic, urethral, anorectal diseases
most informative wave on EMG studies of LS disease
F wave which evaluates motor pathways of ventral nerve roots and peripheral motor axons
radiographic imaging studies for LS disease
- survey films2. linear tomography3. venography4. myelography5. discography/epidurography__________________________6. CT (extended will accentuate compression)7. MRI
where is the most common location of osteochondrosis lesion to be seen in the LS spine
DORSAL aspect of cranial S1 end plate(figure 33-7)
percentage of good outcomes with medical mgmt 2-4 months
50%
disc related LS stenosis treated with epidural 1 mg/kg methylprednisolone outcome
79% clinical improvement3 injections given every 2weeks and 6 weeks following first injectionmethylprednisolone 1 mg/kg epidurally w fluoro guidance(VCOT 2009)
most common surgical approaches for LS disease
1. dorsal decompression L7-S1 +/- discectomy2. dorsal decompression L7-S1 +/- distraction and fusion3. foraminotomy–endoscopically assisted, thru minilaminectomy–thru ilial window (avoids dorsal destabilization)
anatomic borders for dorsal laminectomy of L7-S1
lateral limits are the axial border of the articular processcranial and caudal limits are performed until normal structures are visible
distraction of L7-S1
performed if overriding of L7-S1 articulation is seen, collapse and motion are ID’d during sx1. distract b4 fusion with lamina spreaders (distract until normal position of L7-S1 facets)2. debride cartilage3. cancellous bone graft from ilial wing placed4. stabilize with pins PMMA, lag screws, SOP, intervertebral bolt (spondylofitz bolt) w pins/screws PMMA
direction of cortical screw insertion for stabilization of L7-S1
fuse cd L7 process to cranial S1 processcortical screw should be placed in lag fashion (risk fracture of process if screw is too large)directed ventrolateral 30-45 degrees
surgical success rates of LS laminectomy and discectomy
73-79% (~75%)
