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
greatest risk after posterior laminectomy and instrumented fusion?
C5 nerve palsy (occurs in approx 7% of cases)
what is chief mechanism of action of parathyroid hormone in tx of osteoporosis?
- stimulates osteoblastic bone formation and reducing osteoblastic apoptosis
- tx reduces vertebral fxs by 65%
surgical indications for thoracolumbar burst fractures?
- neurologic deficit
- PLC injury
- polytrauma (relative indication)
medical management of ankylosing spondylitis?
- PT and NSAIDS in conjunction w/ GI protective therapy
- after adequate trial of therapy w/ two NSAIDs exceeding 3 months or limited by med toxicity, the pt may undergo TNF-a blockade therapy (eg INFLIXIMAB)
The risk of spinal cord ischemia is higher in pts w/ renal disease, because they are thought to be less able to compensate for the changes in spinal cord blood flow
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Pseudoarthrosis of the tibia is common in pts w/ what?
Neurofibromatosis (NF-1)
what spine condition routinely requires early surgical intervention in pts w/ Marfan syndrome?
-Progressive scoliosis
The mechanism of action of etanercept in the treatment of rheumatoid arthritis is based on its ability to act as an…
Antagonist of TNF-a
what mJOA score represents severe cervical spondylotic myelopathy?
mJOA score LOWER than 12
In patients with severe cervical spondylotic myelopathy (mJOA score lower than 12), how is the quality of life expected to change following decompressive surgery?
A large prospective study analyzed the quality of life after surgery compared with preoperative levels for patients with cervical myelopathy. Fehling and associates found that the quality of life statistically improved after surgery even when patients were analyzed based on their preoperative mJOA scores (mild, medium, or severe myelopathy). All groups had statistical improvement in quality of life after surgery, regardless of disease severity.
rate of C5 nerve root palsy after cervical decompression?
C5 nerve root palsy occurs relatively commonly after cervical decompression, with an incidence of about 5% (Lim and associates). One study by Lee and associates reported the rate to be 28.9% after posterior decompression and fusion. Most patients (92%) improve by 2 years after surgery. Risk factors for persistent symptoms included a motor grade of less than or equal to 2 of 5, multisegment dysfunction involving more than C5, and loss of sensation with pain (Lim and associates).
Is periop infection more common with an anterior or posterior cervical approach
POSTERIOR (risk increased by presence of diabetes)
Increased risk of periop complications after cervical decompression in which groups?
A recent prospective study by Tetreault and associates revealed an increased risk of perioperative complications in patients with diabetes mellitus, ossification of the posterior longitudinal ligament, longer surgical duration, and more medical comorbidities.
which factors are associated w/ a poorer clinical outcome after surgical decompression for cervical spondylotic myelopathy?
The authors found that certain patient factors were associated with a poorer clinical outcome, including older age, a worse baseline myelopathy score, impaired gait, more medical comorbidities, smoking, and a longer duration of symptoms.
which structure is at greatest risk of injury during anterior midcervical spine exposure?
Recurrent laryngeal nerve
-can lead to post-op dysphagia
which structure is at greatest risk of injury during cervical corpectomy or posterior C1 arch exposure?
Vertebral artery
-Increased risk to the vertebral artery occurs during cervical corpectomy due to an aberrant course of the vertebral artery. The incidence of midline migration of the vertebral artery is 7.6%. The vertebral artery is also at increased risk during posterior C1 arch exposure, which should be limited to 1.5 cm lateral to the midline!
which structure is at greatest risk of injury during bicortical fixation w/ either a C1 lateral mass or C1-2 transarticular fixation?
Internal carotid artery
-The internal carotid artery lies just anterior to the anterior arch of C1
which structure is at greatest risk of injury during posterior laminectomy and instrumented fusion?
C5 nerve palsy
- During posterior laminectomy and instrumented fusion, multiple structures are at low risk, but the greatest risk is of C5 nerve palsy, which occurs in approximately 7% of cases and has reported rates ranging from 0% to 30%.
- 90% have resolution by 2 yrs
When to treat lumbar disc herniations?
- The Spine Patient Outcomes Research Trial (SPORT) showed that after 6 weeks of failed nonsurgical treatment, surgical intervention is indicated.
- A microdiskectomy is indicated, and evidence shows that removal of disk debris within the canal is the most important step to alleviate symptoms. Further debridement into the disk space can result in early Modic changes, increased analgesic requirements, and decreased health-related quality-of-life scores.
Important consideration in pts w/ NF-1 and shortness of breath or fatigue?
Aortic stenosis requiring cardiac eval!
-the new onset of cardiac symptoms should prompt an urgent cardiology evaluation for aortic stenosis, which occurs in approximately 2% of cases.
What is the most common sequela of vertebral fracture in patients with an ankylosed spinal disorder such as ankylosing spondylitis?
Spinal cord injury
-In a retrospective study of 112 patients with spinal fractures and an ankylosing spinal disorder, ankylosing spondylitis or diffuse idiopathic hyperostosis spinal cord injury was present in 58% of all patients. Of the total, 19% experienced a delay in the diagnosis of fracture. During the follow-up period, 32% of the patients died (Caron and associates). The radiographic findings of an ankylosed spine are readily apparent, but the specific diagnosis of ankylosing spondylitis is often absent owing to the lack of a unified method of diagnosis (Taurog and associates).
Tandem stenosis
Tandem stenosis is the occurrence of concurrent cervical and lumbar stenosis. The prevalence has been estimated to be from 5% to 25%. Symptomatic tandem stenosis can present with a confusing scenario of both neurogenic claudication and myelopathy symptoms.
- The association of cervical and lumbar stenosis was found to be statistically significant (p < .05). Stenosis in one part of the spine positively predicts for stenosis in the other area of the spine 15.3% to 32.4% of the time.
-Tandem stenosis should be considered when evaluating a patient with mixed claudication and myeloradiculopathy symptoms.
Surgical versus nonoperative treatment for lumbar disc herniation: four-year results for the Spine Patient Outcomes Research Trial (SPORT).
In a combined as-treated analysis at 4 years, patients who underwent surgery for a lumbar disc herniation achieved greater improvement than nonoperatively treated patients in all primary and secondary outcomes (bodily pain, physical function, disability) except work status (equivalent)
Spinal osteotomies
- The aims of spinal deformity surgery are to achieve balance, relieve pain and prevent recurrence or worsening of the deformity.
- The main types of osteotomies are the Smith-Petersen osteotomy (SPO), pedicle subtraction osteotomy (PSO), bone-disc-bone osteotomy (BDBO) and vertebral column resection (VCR), in order of increasing complexity.
- SPO is a posterior column osteotomy in which the posterior ligaments and the facet joints are removed and correction is performed through the disc space. A mobile anterior disc is essential. SPO is best in patients with +6-8 cm C7 plumbline. The amount of correction is 9.3° to 10.7°/level (1°/mm bone).
- PSO is a technique where the posterior elements and pedicles are removed. Then a triangular wedge through the pedicles is removed and the posterior spine is shortened using the anterior cortex as a hinge. The ideal candidates are patients with a severe sagittal imbalance. A single level osteotomy can produce 30° 40° of correction. A single level osteotomy may restore global sagittal balance by an average of 9 cm with an upper limit of 19 cm.
- BDBO is an osteotomy done above and below a disc level. A BDBO provides correction rates in the range of 35° to 60°. The main indications are deformities with the disc space as the apex and severe sagittal plane deformities.
- VCR is indicated for rigid multi-planar deformities, sharp angulated deformities, hemivertebra resections, resectable spinal tumours, post-traumatic deformities and spondyloptosis. The main indication for a VCR is fixed coronal plane deformity.
- The type of osteotomy must be chosen mainly according to the aetiology, type and apex of the deformity. One may start with SPOs and may gradually advance to complex osteotomies.
Degenerative spondylolisthesis
Degenerative spondylolisthesis is a radiographic sign of substantial degeneration of a disk space and is often associated with spinal stenosis. The primary procedure typically planned to address a degenerative spondylolisthesis is a laminectomy. An adjacent-level degenerative spondylolisthesis is typically instrumented and fused to the previous fusion construct.
-The degeneration of the adjacent disk is also associated with a loss of disk height. A concern in this patient is the development of kyphosis at the L5-S1 disk space. Kyphosis at the lumbosacral junction can lead to sagittal imbalance issues.
Patients with sagittal imbalance are at increased risk for proximal junctional kyphosis or a more acute complication of proximal junctional failure.
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spinopelvic parameters
The sagittal vertical axis is a plumb line dropped from C7 and should fall behind the hip joints and within 4 to 5 cm of the posterior corner of S1 (an easily identifiable radiographic marker). Pelvic incidence is a constant that is unique to each patient’s spinopelvic anatomy. Pelvic incidence typically is within 10 degrees of the lumbar lordosis in an upright adult. Pelvic tilt (PT), on the other hand, can vary based on a patient’s stance. PT is an indicator of the amount of compensation a patient has developed by retroverting their pelvis to stand upright. In an upright patient who is not compensating for loss of spinal sagittal alignment, the PT should be less than 20 degrees.
posterior cervical decompression for cervical spondylotic myelopathy
A large prospective study analyzed the quality of life after surgery compared with preoperative levels for patients with cervical myelopathy. Fehling and associates found that the quality of life improved after surgery even when patients were analyzed based on their preoperative mJOA scores (mild, medium, or severe myelopathy). C5 nerve root palsy occurs relatively commonly after cervical decompression, with an incidence of about 5% (Lim and associates). One study by Lee and associates reported the rate to be 28.9% after posterior decompression and fusion. Most patients (92%) improve by 2 years after surgery. Risk factors for persistent symptoms included a motor grade of less than or equal to 2 of 5, multisegment dysfunction involving more than C5, and loss of sensation with pain (Lim and associates). Infection is another complication that is more common with a posterior cervical spine approach, and the risk of infection is increased by the presence of diabetes. A recent prospective study by Tetreault and associates revealed an increased risk of perioperative complications in patients with diabetes mellitus, ossification of the posterior longitudinal ligament, longer surgical duration, and more medical comorbidities. Another large, multi-institutional study by Tetreault and associates sought to predict which patients would improve after surgical decompression of cervical spondylotic myelopathy. The authors found that certain patient factors were associated with a poorer clinical outcome, including older age, a worse baseline myelopathy score, impaired gait, more medical comorbidities, smoking, and a longer duration of symptoms.
What is the advantage of percutaneous pedicle screw fixation over open instrumentation and fusion for a thoracolumbar burst fracture without neurologic deficit?
Less blood loss
-A prospective randomized study on short-segment treatment of burst fractures with and without fusion demonstrated similar outcomes at 5 years with lower blood loss in the nonfusion group. There is by definition no fusion performed with percutaneous stabilization, so patients often develop hardware failure. Some surgeons routinely remove instrumentation following percutaneous stabilization, thus revision surgery is common. Clinical outcomes are not improved compared to open methods.
For patients with rheumatoid arthritis who are undergoing surgery for symptomatic cervical myelopathy, neurologic recovery after decompression is best predicted by what presurgical measurement?
posterior atlanto-dens interval (PADI) 14 or greater
Differentiate infection from metastatic disease in the spine on imaging
Disk is spared in metastatic disease, whereas diskitis and osteomyelitis will show destructive changes in the disk and blurring of disk margins
Which condition routinely requires early surgical intervention in patients with Marfan syndrome?
Progressive scoliosis
- Rapidly progressive scoliosis in immature patients is associated with higher surgical complications, but surgery is indicated. Overcorrection is associated with significant cardiovascular complications and should be avoided.
when do you NOT need an emergent cervical MRI for a pt w/ perched or dislocated facets?
If pt is awake, oriented, and able to cooperate w/ exam, then proceed to immediate serial traction for reduction
-Cervical MRI is not always readily available and can delay reduction. MRI can be performed after facet reduction.
Factors associated w/ increased risk of complications for surgical tx of cervical spondylotic myelopathy?
the vast majority of complications were treatable and without long-term impact. Multivariate factors associated with an increased risk of complications include greater age, increased operative time, and use of combined anterior-posterior procedures.
how long should you wait to perform surgery for symptomatic lumbar disc herniation?
usually at least 6 wks of non-op treatment should be performed first
Athetoid cerebral palsy
This type of CP occurs more frequently in patients who had kernicterus during the neonatal period. These patients are more likely to develop cervical stenosis, disk degeneration, and listhetic instability with related myelopathy during their adult years. This condition’s exact cause is unknown.
Conditions seen in spastic quadriplegic CP?
Bilateral hip subluxation, scoliosis, and insufficiency fractures of the long bones are more commonly seen in spastic quadriplegic CP.
Risk factors for type 2 dens fx nonunion?
- displacement > 5mm
- angulation > 10 deg
- posterior displacement
- age > 40 yrs old
- fx gap > 2mm
- tx delay
Indications for ANTERIOR odontoid screw osteosynthesis in type 2 dens fx?
- type 2 fractures
- fx line perpendicular to path of screw
- anatomy permitting proper screw placement
