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A. Halogenated anesthetic agents
B. Nitrous oxide
C. Hypothermia
D. Hypotension.
E. A, B, and C
F. All of the above.
Response (F) Halogenated anesthetic agents, nitrous oxide,
hypothermia, and hypotension all have an adverse effect on
SEPs recording [12–15].
Question 20
Why somatosensory evoked potentials (SEPs) are not con-
sidered a “real-time” intraoperative monitoring modality?
A. Need to use a stimulus frequency less than 60 Hz.
B. Low amplitude nature of the stimulus.
C. Slow conduction of electrical stimuli by the large fiber
sensory nerves.
D. High number of stimulated responses in order to aver-
age out background noise.
E. Significant decrease in baseline SEPs is required to
detect damage to the nervous system.
Response (D) SEPs are not considered to offer real- time
monitoring as a significant number of trials of signal
amplification are required in order to average out the back-
ground noise of other biologic stimuli and operating room
equipment. It has been reported that 500–1000 stimuli are
required, and the process of averaging these signals takes
several minutes [26].
Question 21
Which of the following is considered an advantage of using
motor evoked potentials (MEPs) for intraoperative moni-
toring compared to somatosensory evoked potentials?
A. Less disruption of surgical flow during obtaining
signals.
B. Decreased risk of bite injuries.
C. Changes in patient positioning while obtaining stimulus
are less likely.
D. Increased utility in patients with diabetic neuropathy.
E. Decreased risk of seizures.
Response (D) MEPs allow for a more accurate assessment
of the cortical spinal tracts than somatosensory evoked
potentials (SEPs). In addition, patients with polyneuropathies
such as diabetic neuropathy have more difficulty conducting
the low amplitude stimuli of SEPs compared to the higher
amplitude stimuli seen in motor evoked potentials. However,
there are downsides to the use of motor evoked potentials.
These revolve mainly around the consequences of
high-intensity stimulus used. The high amplitude of the signal
causes jerking motions of the muscles, which can lead to
damage from surgical instruments, tongue biting, position
changes, and seizures in rare cases. As a result, all surgical
activities are stopped to obtain motor evoked potentials. This
can disrupt the operative flow [26].
Question 22
When performing an extreme lateral interbody fusion
(XLIF), which of the following muscles is not commonly
monitored via EMG?
A. Extensor hallucis longus
B. Vastus medialis
C. Biceps femoris
D. Tibialis anterior
E. Gastrocnemius.
Response (A) All of the following muscles except extensor
hallucis longus are monitored via EMG during an XLIF.
These muscles are easily palpable and are innervated by
branches of the lumbar plexus, which is at risk of injury
during the transpsoas approach used in this procedure [27].
Question 23
Which of the following is not a disadvantage of motor
evoked potentials (MEPs)?
A. Long turn-around time for one stimulation.
B. Highly sensitive to neuromuscular blockade.
C. Highly vulnerable to inhalation anesthesia.
D. Highly intertrial variability in amplitude.
E. Possibility of seizure induction.
Response (A) MEPs monitor motor pathways by stimu-
lating corticospinal tracts. This technique has some disad-
vantages, such as high sensitivity to inhalation agents and
neuromuscular blockage and stimulation-related movement.
However, the time required for any stimulation is relatively
brief in MEPs. Meaningful monitoring information can be
obtained in a minute or less, and multiple stimulations can be
done without interrupting the ongoing flow of the surgery
[28].
5 Intraoperative Neuromonitoring 87
Question 24
A 54-year-old male with a history of a recent fall on his back
after slipping on ice presents with diminished knee jerk
reflex and has weakness in knee extension. The patient also
has diminished sensation on the medial foot. The MRI of the
lumbar spine has shown a single level central disc hernia-
tion. Which level of the lumbar spine does this patient most
likely have a decreased baseline neuromonitoring EMG
signal?
A. L2-3
B. L3-4
C. L4-5
D. L5-S1.
Response (B) This patient has all the symptomatology of
someone who has a herniated disc at the L3-L4 level. This
can be seen with weakness of knee extension, diminished
patellar reflex, and diminished sensation in the medial aspect
of the foot (L4) [29].
Question 25
If a disc herniation occurred at the C6-7 level, which motor
evoked potentials (MEPs) would demonstrate increased
amplitude after corrective spinal fusion?
A. Biceps
B. Deltoid
C. Triceps
D. Both A and C.
Response (C) Triceps will be the only MEPs that is
diminished when a disc herniation occurs at this level since
the C7 nerve root is compressed. The deltoid will be affected
by a C4-5 herniation, and the biceps will be diminished with
a C5-6 herniation [30].
Question 26
What is a limitation of the somatosensory evoked potentials
(SEPs)?
A. Abrupt disturbance to the surgical procedu re
B. Cannot be monitored constantly
C. Neuromuscular blocks alter the results
D. Only provides information about the posterior 2/3 of the
spinal cord.
Response (D) Providing information about the posterior
2/3 of the spinal cord is the only limitation of SEPs among
the above answers as it provides information from the sen-
sory tracts and dorsal aspects of the cord. Somatosensory
evoked potentials allow for limited disturbances during
surgery, can be monitored constantly, and neuromuscular
blocks do not impact the results [ 31 , 32].
Question 27
Which of the following locat ions is not a placement for
somatosensory evoked potentials in monitoring upper
extremities?
A. Erb’s point
B. Cz-A1 and Cz-A2
C. Over spinous process (CII)
D. Contralateral cortex (C3, C4).
Response (B) Erb’s point, over spinous process (CII), and
contralateral cortex (C3, C4) are all used for the monitoring
of upper extremities. In contrast, Cz-A1/A2 are used to
monitor lower extremities during an operation [33].
Question 28
Which of the following anesthesia gas agents cannot be used
during transcranial motor evoked potential monitoring?
A. N2O
B. Halothane
C. Isoflurane
D. Sevoflurane.
Response (A) During transcranial motor evoked potential
monitoring, N2O cannot be used as it disrupts the ability to
stimulate motor evoked potentials. All the other gases are
halogens, which do not interact with this monitoring
approach [34, 35].
Question 29
Triggered electromyography (EMG) is used to detect:
A. Anterior spinal horn injury
B. Misplacement of spinal interbody
C. Pedicle screw breach
D. Inferior nerve injury.
88 A. Khan et al.
Response (C) The triggered EMG is used to determine
whether the pedicle screw has breached through the medial
or lateral walls after their placement. The other choices
cannot be monitored by the triggered EMG [36, 37].
Question 30
What is the accurate range of normal threshold potential s for
a lumbar triggered EMG?
A. 6 to 8 mA
B. 7.6 to 10 mA
C. 7.6 to 11 mA
D. 15 to 20 mA.
Response (C) The range of 7.6–11 mA is the normal range
for lumbar triggered EMG. The range of 6–8 mA is the
normal range for thoracic thresholds, while 7.6–10 mA is
the correct range for the normal cervical thresholds. 15–
20 mA has a range that often strongly suggests a pedicle
breach has occurred [36, 38].
Question 31
If the H reflex disappeared unilaterally during surgery, this
represents which nerve roots compromise?
A. S4 and S5
B. L4 and L5
C. L1 and L2
D. S1 and S2.
Response (D) The H reflex is a monosynaptic reflex
response that can be obtained from the soleus muscle after
stimulation of the tibial nerve. Compromise of the S1 and S2
nerve roots would demonstrate a unilateral disappearance of
the H reflex intraoperatively. The other answer choices do
not have any association with the H reflex [37].
Question 32
If a surgeon wants to isolate the root of a nerve injury to a
singular spinal level, which neuromonitoring modality
should be added?
A. Dermatomal somatosensory evoked potentials (SEPs)
B. Pudendal SEPs
C. Transcranial motor evoked potentials
D. Triggered EMG.
Response (A) The dermatomal SEPs provide detailed
sensory information to isolate a single nerve root dysfunc-
tion, which is a limitation of the other answ er choices [39].
Question 33
During an L4-5 posterior lumbar interbody fusion, a
decreased amplitude on dermatomal somatosensory evoked
potentials (SEPs) due to nerve injury while performing the
interbody cage placement can be demonstrated by loss of
sensation to which anatomical location of the lower limb,
most commonly?
A. Lateral foot
B. Posterior Calf
C. Lateral Calf
D. Medial Calf.
Response (D) The L4 nerve root exits at the L4-5 level to
innervate the lateral thigh, patellar region, and medial calf to
the medial foot and big toe. The posterior calf and lateral
foot are innervated by the S1 nerve, while the L5 nerve
innervates the lateral calf [40].
Question 34
Which of the following is NOT A TRUE statement
regarding Spinal Cord Injury without Radiographic Abnor-
mality (SCIWORA)?
A. SCIWORA is more commonly seen in the pediatric age
group, with a predilection for the cervical spine.
B. The most important factor in SCIWORA prognosis is
age.
C. Cord hemorrhage is not an expected finding on MRI of
patients with SCIWORA.
D. The mainstay treatment for SCIWORA is cervical brace
or collar and restriction of high-risk activities.
E. Within the diagnostic algorithm of SCIWORA,
somatosensory evoked potentials are considered a spe-
cial rather than routine test.
Response (B) In general, most SCIWORA patients show
remarkable improvement in neurological status after the
injury, and operative management is rarely justifiable. The
most significant predictor of prognosis after SCIWORA is
the initial neurological status. Pediatric patients with com-
plete spinal cord injury rarely improve, and those with
severe but incomplete spinal cord injury often improve but
seldom regain normal function. Patients with mild to
5 Intraoperative Neuromonitoring 89
moderate initial neurological deficits, on the other hand,
have a higher chance of attaining full recovery [41].
Question 35
Which of the following is NOT a consensus-based best
practice guideline for Intraoperative Neurophysiological
Monitoring in pediatric and adult spine deformity surgery in
the United States?
A. Transcranial motor evoked potentials and/or descending
neurogenic evoked potentials should be used in all
spine deformity cases.
B. A 50% decrease in somatosensory evoked potentials
(SEPs) signal amplitude from baseline and/or a sustained
decrease in transcranial motor evoked potentials signal
amplitude, and/or a decrease in descending neurogenic
evoked potentials signal of >60% constitutes ‘‘ significant
warning criteria’’ in spine deformity surgery.
C. Spontaneous and triggered electromyography should be
used in all spine deformity cases.
D. Intraoperative neuromonitoring is best performed with a
team approach: surgeon, anesthesiologist, and qualified
neuromonitoring personnel should all be involved in
identifying and communicating neuromonitoring changes.
E. A wake-up test should always be considered in spine
deformity cases with persistent signal degradation or in
all patients who cannot be monitored.
Response (C) Somatosensory evoked potentials, not
spontaneous and triggered electromyography, should be
used in all spinal deformity surgeries. The consensus-based
checklist for intraoperative neurophysiological monitoring
was developed to improve patient care quality and minimize
the risk of the neurological deficit through optimization of
clinical decision-making. This checklist also contains several
prompts for items that could be easily overlooked during a
crisis response, such as checking limb positioning and
anticipating the need for future actions such as a wake-up
test [42].
Question 36
During an anterior cervical discectomy and fusion, the
neurophysiologist notices a sudden change in the waveform
at Erb’s point. Which of the following structure is most
likely affected?
A. P14: cervico-medullary junction
B. N22: ulnar nerve
C. N13: radial nerve
D. N9: brachial plexus
E. N8: popliteal fossa.
Response (D) Somatosensory evoked potent ials are
recorded from the upper and/or lower extremity nerve to
identify impending permanent damage to neurologic struc-
tures. N9, also known as Erb’s point, reflects the sensory
contributions of the brachial plexus. Ulnar nerve and radial
nerve are typically not monitored. N22 is the nomenclature
for the post-synaptic dorsal horn of the lumbar spinal cord,
and N13 refers to the post-synaptic dorsal horn of the cer-
vical spinal cord [43].
Question 37
Which of the following is NOT a relative contraindication
for intraoperative motor evoked potentials?
A. Increased intracranial pressure
B. Presence of pacemaker
C. Cochlear prosthesis
D. History of epilepsy
E. Morbid obesity.
Response (E) There is no absolute contraindication for any
of the techniques of intraoperative neurophysiological
monitoring. However, some relative contraindications for
motor evoked potentials exist, including a history of seizure
disorder, increased intracranial pressure or cortical lesions,
defects of the skull or skull convexity, implanted deep brain
stimulator leads, cardiac pacemakers, and other implanted
devices (i.e. cochlear prosthesis) [44].
Question 38
A 15-year-old girl was scheduled to undergo an anterior and
posterior fusion of her lumbar spine. The patient has a his-
tory of thoracic laminectomy and spinal cord astrocytoma
resection three years prior. Bilateral lower extremity weak-
ness and minimal sensation and proprioception on the left
leg were noted on preoper ative evaluation. A device was
placed to monitor the central nervous system’s response to
various surgical stimuli. Administering which of the fol-
lowing anesthetic agents during the surgery would increase
the response amplitude?
A. Propofol
B. Ketamine
C. Midazolam
D. Clonidine
E. Tubocurarine.
90 A. Khan et al.
Response (B) The described device in this vignette is
somatosensory evoked potentials (SEPs). It directly assesses
spinal cord sensory tracts while providing indirect information
about motor tracts. Anesthetics have varying effects on SEPs.
Ketamine is an N-methyl D-aspartate receptor and glutamate
receptor antagonist that affects the amplitude of cortical SEPs
without affecting the latency. Propofol and midazolam
increase SEPs latency and decrease amplitude. As an alpha-2
agonist, Clonidine does not affect SEPs; however, it severely
interferes with motor pathways neuromonitoring. Tubocu-
rarine also has no direct effect on SEPs [45].
Question 39
Which of the following is NOT a potential risk factor for
electrophysiologic and neurologic deterioration during cer-
vical surgery?
A. Long segment surgery
B. Use of instrumentation
C. Preexisting myelopathy
D. Surgery at the clivus, the atlas, or the axis
E. Surgery at lower cervical segment.
Response (E) Risk factors for electrophysiologic and
neurologic deterioration during cervical surgery are preop-
erative myelopathy, multi-segmental surgery, upper cervical
surgery, use of instrumentation, and application of corrective
forces to the neck. Among them, myelopathy is the strongest
predictor that overshadowed the effect of the other recog-
nized factors [46].
Question 40
After placing an interbody cage from a lateral approach,
there is an immediate drop in amplitude in motor evoked
potentials for the quadriceps muscle; at which level did the
surgery most likely occur?
A. L1
B. L3
C. L5
D. S1.
Response (B) The cage was placed too posteriorly in this
patient and caused either transient or permanent damage to
the nerve root at the index level. The femoral nerve origi-
nates from the dorsal divisions of the L2-L4 ventral rami. It
innervates the quadriceps muscle. The L3 nerve root is the
only one in this range, making it the correct answer.
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6
Minimally Invasive Spine Surgery
Asham Khan, Moleca M. Ghannam, Ryan M. Hess, Slah Khan,
Alexander O. Aguirre, Cathleen C. Kuo, Ali Y. Elkady, Ahmed H. Omar,
Mohammad Elbaroody, and Mohamed A. R. Soliman
Question 1
During a minimally invas ive lumbar microdiscectomy, what
complication often occurs but should be avoided when
introducing the initial dilators?
A. Penetration of the interlaminar space
B. Tear of the Ligamentum Flava
C. Vascular injury
D. Nerve root retraction
Response (A) Penetration of the interlaminar space occurs
when placing the initial dilator tube and should be avoided in
this procedure. A tear of the ligamentum flavum is not seen
in this procedure while vascular inju ry and nerve root injury
from retraction happen in less than 1% of cases [1, 2].
Question 2
The trajectory of the minimally invasive transforaminal
lumbar interbody fusion (MIS TLIF) avoids the need to
perform which of the following?
A. Laminectomy/l aminotomy
B. Remove the ipsilateral facet joint
C. Retraction of the nerve root and dura
D. Remove a part of the Ligamentum Flava
Response (C) The retr action of the nerve root and the dura
are minimal compared to other approaches such as the PLIF.
All the other answers are still required during an MIS TLIF
[1, 2].
Question 3
Damage to the psoas muscle during a minimally invasive
lateral lumbar interbody fusion (LLIF) causes which of the
following postoperative complications?
A. Abdominal viscera perforation
B. Quadriceps weakness
C. Thigh numbness
D. Hip flexor weakness
Response (D) The psoas muscle is one of the contributing
muscles to flexion of the leg, which is weakened by the
trans-psoas approach often used in LLIF approaches. The
others are also complications of the LLIF approach but do
not occur because of damage to the psoas muscle [3].
A. Khan M. M. Ghannam R. M. Hess S. Khan
A. O. Aguirre C. C. Kuo M. A. R. Soliman (&)
Neurosurgery Department, University at Buffalo,
Buffalo, NY, United States
e-mail: msolim8@uwo.ca
A. Khan
e-mail: akhan@ubns.com
M. M. Ghannam
e-mail: mghannam@ubns.com
R. M. Hess
e-mail: rhess@ubns.com
S. Khan
e-mail: slahkhan@buffalo.edu
A. O. Aguirre
e-mail: aa284@buffalo.edu
C. C. Kuo
e-mail: ckuo9@buffalo.edu
A. Y. Elkady A. H. Omar M. Elbaroody M. A. R. Soliman
Neurosurgery Department, Cairo University, Cairo, Egypt
e-mail: ayousri54@gmail.com
A. H. Omar
e-mail: a.hussein.omar1990@gmail.com
M. Elbaroody
e-mail: mohammad.elbaroody@kasralainy.edu.eg
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024
C. Gragnaniello et al. (eds.), MCQs in Spine Surgery,
https://doi.org/10.1007/978-3-031-69332-8_6
93
Question 4
Damage to what nerve can cause thigh numbness after a
minimally invasive lateral lumbar interbody fusion?
A. Anterior femoral cutaneous nerve
B. Common peroneal nerve
C. Obturator nerve
D. Genitofemoral nerve
Response (A) The anterior femoral cutaneous nerve is a
branch of the femoral nerve that causes thigh numbness. No
transient weakness is seen as this branch is only isolated to
respond to sensory information [3].
Question 5
Which of the foll owing is not a complication of the thora-
coscopic approach to a thoracic corpectomy?
A. Cerebrospinal fluid leak
B. Chyle leak
C. Wrong level surgery
D. Decreased pulmonary function
Response (D) The risk of wrong level surgery is high due
to limited field exposure; while CSF and Chyle leaks are less
commonly observed, the risk during this approach is still
present. There are no changes in pulmonary function after
thoracoscopic approach to thoracic corpectomy; rather, this
is seen in scoliosis correction surgery [4].
Question 6
Which of the following is not a benefit of a minimally
invasive approach for spine surgery?
A. Less blood loss
B. Decreased operative time
C. Diminished amount of postoperative opioid use
D. Reduced risk of infection
Response (B) Less blood loss, diminished amount of
postoperative opioid use and reduction in risk of infection
are all proven benefits to the use of minimally invasive spine
surgeries [3].
Question 7
What is NOT an accepted minimally invasive approach for
spinal decompression surgery?
A. Tubular dilators
B. Microscope
C. Endoscopic approach
D. All of the above are accepted approaches
Response (D) Tubular dilators, microscopes, and endo-
scopes are all accepted instruments for minimally invasive
spine surgery [6].
Question 8
A 60-year-old male presents to the spine clinic with low back
pain, left radicular leg pain, and numbness along the sciatic
region to the calf. He reports that these symptoms started after
carrying heavy loads a week ago. His surgical history was
significant for a successful microdiscectomy at the L4-L5
level ten months ago. Physical examination reveals 3/5 left big
toe dorsiflexion strength, mild sensory loss in the left lateral
lower leg, and 45 degrees on the right straight leg raising test.
MRI shows left-sided L4-L5 paracentral disc herniation.
Conservative therapy was initiated, but the effect was poor.
What is the most appropriate next step in management?
A. Decompression with transforaminal lumbar interbody
fusion
B. Microdiscectomy through a far lateral approach
C. Microdiscectomy through a midline approach
D. Extreme lateral lumbar interbody fusion
E. Anterior lumbar interbody fusion
Response (C) The vignette is consistent with single-level
recurrent lumbar disc herniation. Nonoperative treatment is
usually the first-line therapy for most patients. However,
when it fails, revision microdiscectomy is indicated. A mid-
line approach is suggested because this patient has a para-
central disc herniation [5].
Question 9
What is an indication for the use of minimally invasive
transforaminal lumbar interbody fusion?
A. >3 levels degenerative disc disease
B. Spondylolisthesis with Meyerding grade < III
C. Recurrent lumbar disc herniation
D. All of the ab ove are correct indications for this
approach
Response (C) Recurrent lumbar disc herniation is an
appropriate indication for the use of MIS TLIF. A sin-
gle-level or 2-level surgery is an indication for the minimally
94 A. Khan et al.
invasive (MIS) approach; anything more is considered a
contraindication for MIS. Meyerding grade < III is also an
indication for MIS [7, 8].
Question 10
Which of the following outcomes is NOT TRUE regarding
the percutaneous pedicle screw insertion (PPSI) approach
performed by an experienced surgeon?
A. Reduced radiation exposure
B. Increased blood loss
C. Decreased operative time
D. None of the following are true
Response (B) A decrease in radiation exposure is seen in
the PPSI approach due to a shorter duration of fluoroscopy,
in experienced hands, needed to place the screws accurately.
PPSI does not increase blood loss, while it does decreases
operative time in general [9].
Question 11
All of the following are boundaries of the Kambin’s triangle
EXCEPT:
A. Superior endplate of the inferior vertebral body
B. Inferior endplate of the superior vertebral body
C. Superior articulating facet
D. Exiting nerve root (ENR)
Response (B) Kambin’s triangle is a three-dimensional
anatomical triangle located over the dorsolateral interverte-
bral disc of the lumbar spine. This concept is widely
accepted for not only percutaneous endoscopic lumbar dis-
cectomy (PE LD) but also epidural injection, discography
and interbody fusion techniques. Kambin’s safety zone is the
area surrounding the superior endplate of the inferior ver-
tebral body, superior articulating facet, and exiting nerve
root (ENR) [10, 11].
Question 12
After moving his parent s’ heavy furniture out of their house,
a 38-year-old man experi ences lower back pain. He pre-
sented to his doctor with tingling numbness radiating in his
right lower limb down to the medial part of his foot.
A T1-weighted MRI revealed L4-L5 intervertebral disc
herniation. The patient was operated on with percutaneous
endoscopic lumbar discectomy through the Kambin's trian-
gle. Which nerve root is at high risk of injury during this
approach?
A. S1 spinal nerve roots
B. L5 spinal nerve roots
C. L4 spinal nerve roots
D. All of the above
Response (C) In an L4-L5 disc herniation, the L4 nerve
root, exiting nerve root, forms the hypotenuse of the Kam-
bin’s triangle, which may be at potential risk for injury [12 ].
Question 13
A 60-year-old female presented with lower extremity ataxia
and back pain. Workup revealed T9-10 calcified thoracic
disc herniation with severe spinal cord compression. She
underwent a minimally invasive transthoracic decompres-
sion and removal of the calcified disc. Her symptoms
resolved, and she was discharged in an improved condition.
Removal of the head of which rib is necessary during this
approach?
A. 9th
B. 10th
C. 11th
D. None of the above
Response (B) The rib articulates and projects from the
superior aspect of the T10 level and would obstruct access to
the T9-T10 foramen. Therefore, removal of the 10th rib head
is necessary for identification of the ventral aspect of the
dura above the pedicle [13].
Question 14
The entry point of the percutaneous iliac screw is:
A. PSIS
B. Midway between S1 and S2
C. Superior facet of S1
D. Superior facet of L5
Response (A) The entry point of iliac screws is the pos-
terior superior iliac spine, and the trajectory is toward the
acetabulum and passes approximately 1 cm superior to the
sciatic notch. The midway between S1 and S2 is the entry
point of the S2 alar iliac screws [14].
6 Minimally Invasive Spine Surgery 95
Question 15
Relative contraindications of stand-alone anterior lumbar
interbody fusion (ALIF) include:
A. Significant prior abdominal retroperitoneal surgery with
adhesions
B. Severe osteoporosis
C. Isthmic spondylolisthesis at L5/S1
D. Solitary kidney on the side of exposure
E. High-grade spondylolisthesis
Response (C) Significant prior abdominal retroperitoneal
surgery with adhesions, severe osteoporosis, solitary kidney
on the side of exposure, and high-grade spondylolisthesis are
an absolute contraindication for ALIF. Isthmic spondylolis-
thesis at L5/S1 is considered relative contraindications for
stand-alone ALIF and should be posteriorly supplemented [3].
Question 16
The anterior lumbar interbody fusion (ALIF) approach is
suitable for all the following levels EXCEPT:
A. L4/L5
B. L5/S1
C. L2/3
D. None of the above
Response (C) The ALIF approach is suitable for levels
L4/L5 and L5/S1, primarily the latter due to vascular anat-
omy. Although rare, the ALIF approach is limited for L2/3
and L3/4 secondary to extensive peritoneal and kidney
(L2/3) retraction and the risk of superior mesenteric artery
thrombosis [3].
Question 17
Lateral lumbar interbody fusion (LLIF) is suitable for all
levels EXCEPT:
A. L3/4
B. T12/L1
C. L4/5
D. L5/S1
Response (D) This technique is not suitable for the L5/S1
level due to the location of the iliac crest that obstructs lat-
eral access. Furthermore, at more caudal levels of the lumbar
spine, the lumbar plexus courses more anteriorly, and the
iliac vessels course more laterally. This increases the risk of
injury via a lateral approach [3].
Question 18
Which one of the following MIS approaches uses the
trans-psoas approach?
A. Oblique lateral interbody fusion (OLIF)
B. Anterior lumbar interbody fusion (ALIF)
C. Lateral lumbar interbody fusion (LLIF)
D. Posterior lumbar interbody fusion (PLIF)
Response (C) The OLIF approach involves an MIS access
to the disc space via a corridor between the peritoneum and
psoas muscle. The ALIF approaches the disc space anteri-
orly. The PLIF is a posterior approach not related to the psoas
muscle, while the LLIF uses a transposes approach [3].
Question 19
All of the following are true regarding cervical posterior
keyhole foraminotomy EXCEPT:
A. Can be used for soft lateral disc herniation
B. Patient selection includes singer or speaker profession
C. The first bone to be removed is the superior facet of the
vertebrae below
D. The success rate ranges from 90 to 96%
Response (C) The first bone to be removed is the inferior
facet of the vertebrae above. The approach is best indicated
for soft lateral disc, patients with risk of injury of recurrent
laryngeal nerve and short neck patients [15].
Question 20
45-years-old female patient was diagnosed with L4-L5
spondylolisthesis. The decision was made to do minimally
invasive retroperitoneal trans-psoas interbody fusion. Which
of the following is a contraindication for this approach?
A. Pinpoint central canal stenosis
B. Disc space height is > 12 mm
C. Osteoporosis
D. All of the above
Response (D) Contraindications to this approach include
cases requiring direct decompression like pinpoint central
96 A. Khan et al.