Spine Flashcards
What is the average lumbar lordosis?
60 degrees in sagittal plane
Where is the apex of lordosis in lumbar spine?
L3
Pars interarticularis
- mass of bone between superior and inferior articular facets
- site of spondylolysis (consistent with the “collar” on the “Scotty dog projection)
Facet orientation in lumbar spine
-facets start as more sagittal and become more coronal as you move inferior in the axial plane
What is the pedicle orientation in the lumbar spine?
-pedicles angularity more medial as you move distal
what are the smallest pedicles in the entire spine?
T4
Nerve root anatomy in lumbar spine
- nerve root exits foramen under same numbered pedicle
- central herniations affect traversing nerve root
- far lateral herniations affect exiting nerve root
At what level does the spinal cord terminate?
L1-L2
At what spinal level is the iliac crest?
L4-5
Pelvic incidence formula
Pelvic tilt + sacral slope = pelvic incidence
How is pelvic incidence measured?
- a line is drawn from the center of S1 endplate to the center of the femoral head
- a second line is drawn perpendicular to a line drawn along the S1 endplate, intersecting the point in the center of the S1 endplate
- the angle between these 2 lines is the pelvic incidence
What is the formula for pelvic tilt?
Pelvic incidence - sacral slope = pelvic tilt
How do you measure pelvic tilt?
- a line is drawn from the center of the S1 endplate to the center of the femoral head
- a second vertical line (parallel w/ side margin of radiograph) line is drawn intersecting the center of the femoral head
- the angle between these two lines is the pelvic tilt
What is the formula for sacral slope?
Pelvic incidence - pelvic tilt = sacral slope
How do you measure sacral slope?
- a line is drawn parallel to the S1 endplate
- a second horizontal line (parallel to inferior margin of radiograph) is drawn
- the angle between these 2 lines is the sacral slope
Surgical approaches to lumbar spine
Posterior:
-posterior midline (used for PLIF or TLIF)
-Wiltse paraspinal approach
Anterior:
-retroperitoneal (anterolateral) approach
Lateral:
-transposable approach (lumbar plexus moves dorsal to ventral moving down lumbar spine; L4-L5 is lowest accessible disc space and highest risk of iatrogenic nerve injury; ilioinguinal and iliohypogastric nerves most likely injured at this level)
what are the surgical indications for vertebral osteomyelitis?
- progressive neuro deficit
- standard is non-op tx with IV abx and lumbar orthosis
risk factors for proximal junctional kyphosis in setting of instrumented fusions performed for degenerative scoliosis?
- advanced age
- 360 deg fusions
- extension of fusion constructs to sacrum
- upper instrumented vertebrae at level of T1-3
known risk factors for post-surgical infection following spine fusion procedure?
Diabetes, obesity
most frequent complication following revision surgery for proximal junctional kyphosis?
need for further surgery
triggered EMG testing of pedicle screw values
- > 10mA indicated a well-placed screw
- < 4-6 mA indicated a screw directly contacting a neural structure
- 9-10mA suggest a breach of the pedicle may be present
what structure is at greatest risk during a cervical corpectomy?
- vertebral artery
- due to aberrant course w/ midline migration in 7.6% of cases
- vertebral artery also at increased risk during posterior C1 arch exposure, which should be limited to 1.5 cm lateral to midline (7.25mm on each side of midline)
when is the recurrent laryngeal nerve at risk?
during anterior midcervical spine approaches
-can lead to post-op dysphagia
when is internal carotid artery at risk?
-lies just anterior to anterior arch of C1 and is at risk during bicortical fixation w/ either a C1 lateral mass or C1-2 transarticular fixation