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1. General Principles & Basic Science MCQs

Practice Set 11 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 201

Topic: 1. General Principles & Basic Science

During the placement of percutaneous pedicle screws for a minimally invasive fusion, the surgeon inadvertently advances the Jamshidi guidewire too far anteriorly. Which of the following complications is most likely to occur as a direct result of an anterior vertebral body breach at the L4 level?

. Injury to the common iliac artery or vein
. Laceration of the superior mesenteric artery
. Injury to the lumbar plexus
. Bowel perforation
. Ureteral transection

Correct Answer & Explanation

. Injury to the common iliac artery or vein

Explanation

At the L4 level, the bifurcation of the aorta and inferior vena cava into the common iliac vessels occurs just anterior to the vertebral body. An anterior guidewire breach carries a catastrophic risk of injuring these major vascular structures.

Question 202

Topic: Biology, Genetics & Bone Healing

The use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) has been associated with which of the following specific postoperative complications?

. Anterior thigh pain
. Postoperative radiculitis
. Aseptic meningitis
. Retrograde ejaculation
. Spontaneous dural closure

Correct Answer & Explanation

. Postoperative radiculitis

Explanation

The use of rhBMP-2 in the posterior or transforaminal lumbar space has a well-documented risk of causing postoperative radiculitis, seroma formation, and ectopic bone growth leading to neuroforaminal stenosis.

Question 203

Topic: 1. General Principles & Basic Science

During a lateral lumbar interbody fusion (LLIF) at L4-L5, which of the following intraoperative neuromonitoring modalities is most critical to prevent lumbar plexus injury during dilation and retractor placement?

. Somatosensory evoked potentials (SSEPs)
. Motor evoked potentials (MEPs)
. Spontaneous and triggered electromyography (sEMG and tEMG)
. Brainstem auditory evoked responses (BAERs)
. Electroencephalography (EEG)

Correct Answer & Explanation

. Spontaneous and triggered electromyography (sEMG and tEMG)

Explanation

Triggered EMG (tEMG) is critical during the transpsoas approach to map the proximity of the lumbar plexus to the dilators and retractor blades. sEMG detects spontaneous nerve irritation during retraction.

Question 204

Topic: 1. General Principles & Basic Science

The Wiltse paraspinal approach is frequently utilized in minimally invasive lumbar surgeries to minimize muscle morbidity. This approach utilizes an internervous and intermuscular plane between which of the following muscle groups?

. Psoas major and quadratus lumborum
. Spinalis and multifidus
. Multifidus and longissimus
. Longissimus and iliocostalis
. Intertransversarii and multifidus

Correct Answer & Explanation

. Multifidus and longissimus

Explanation

The Wiltse approach splits the fascia to access the natural cleavage plane between the multifidus (medially) and the longissimus (laterally). This avoids denervation of the multifidus, which is supplied by the medial branch of the dorsal ramus.

Question 205

Topic: 1. General Principles & Basic Science



The image demonstrates interbody cage subsidence. Which of the following technical errors most significantly increases the risk of cage subsidence following an MIS TLIF?

. Placement of a wide-footprint cage resting on the apophyseal ring
. Aggressive endplate preparation violating the subchondral bone
. Use of bilateral percutaneous pedicle screws
. Packing the disc space exclusively with autologous local bone
. Utilizing an expandable titanium interbody device

Correct Answer & Explanation

. Placement of a wide-footprint cage resting on the apophyseal ring

Explanation

Aggressive endplate scraping that violates the subchondral bone structurally weakens the vertebral endplate, drastically increasing the risk of the interbody cage subsiding into the vertebral body.

Question 206

Topic: 1. General Principles & Basic Science

During a single-level MIS TLIF using a 22 mm tubular retractor, an incidental durotomy occurs with visible cerebrospinal fluid leak. Primary suture repair is technically impossible due to limited visualization. What is the most appropriate next step in management?

. Immediate conversion to an open laminectomy for primary suture repair
. Placement of a lumbar subarachnoid drain for 7 days
. Application of a synthetic dural patch and fibrin sealant, followed by layered fascial closure
. Leave the durotomy open and place a deep subfascial suction drain
. Pack the epidural space tightly with absorbable gelatin sponge to compress the sac

Correct Answer & Explanation

. Immediate conversion to an open laminectomy for primary suture repair

Explanation

In minimally invasive tubular surgery, conversion to open is rarely mandatory for small unrepairable durotomies. Application of a dural overlay (patch/sealant) and watertight fascial closure is an accepted and effective management strategy.

Question 207

Topic: 1. General Principles & Basic Science

When counseling a patient on the long-term outcomes of minimally invasive vs open lumbar fusion, what does current literature indicate regarding the incidence of symptomatic adjacent segment disease (ASD) at 5 years?

. MIS fusion virtually eliminates the risk of ASD
. Open fusion has a significantly lower rate of ASD due to better lordosis restoration
. The rate of symptomatic ASD is generally similar between MIS and open techniques
. MIS fusion has a higher rate of ASD due to the use of smaller interbody cages
. ASD only occurs in open fusion patients who receive BMP-2

Correct Answer & Explanation

. The rate of symptomatic ASD is generally similar between MIS and open techniques

Explanation

Long-term comparative studies and randomized trials show that while MIS techniques reduce immediate postoperative pain and blood loss, the long-term incidence of symptomatic adjacent segment disease remains statistically similar to open fusion.

Question 208

Topic: 1. General Principles & Basic Science

Compared to traditional open transforaminal lumbar interbody fusion (TLIF), minimally invasive (MIS) TLIF is most consistently associated with which of the following?

. Higher rate of pseudoarthrosis
. Increased radiation exposure to the surgeon
. Higher postoperative infection rate
. Increased intraoperative blood loss
. Longer hospital stay

Correct Answer & Explanation

. Increased radiation exposure to the surgeon

Explanation

MIS TLIF relies heavily on fluoroscopy for localization and hardware placement, leading to significantly higher radiation exposure to the surgeon. Fusion rates, infection rates, blood loss, and hospital stays are generally equal or better compared to open TLIF.

Question 209

Topic: Surgical Anatomy & Approaches

During a lateral transpsoas interbody fusion at L4-L5, the patient develops immediate postoperative ipsilateral hip flexion weakness and anterior thigh numbness. What is the most likely cause?

. Injury to the cauda equina
. Femoral nerve or lumbar plexus neuropraxia
. Sciatic nerve injury
. Spinal cord ischemia
. L5 nerve root avulsion

Correct Answer & Explanation

. Femoral nerve or lumbar plexus neuropraxia

Explanation

The lumbar plexus lies within the posterior aspect of the psoas major muscle. The transpsoas approach puts the lumbar plexus (specifically the femoral nerve components) at risk, causing temporary or permanent anterior thigh numbness and iliopsoas weakness.

Question 210

Topic: 1. General Principles & Basic Science

Compared to traditional open TLIF, studies evaluating muscle parameters post-MIS TLIF consistently demonstrate:

. Increased multifidus muscle atrophy
. Decreased multifidus muscle atrophy and fatty infiltration
. Higher incidence of paraspinal muscle denervation
. Slower recovery of paraspinal muscle cross-sectional area
. No difference in muscle volume postoperatively

Correct Answer & Explanation

. Decreased multifidus muscle atrophy and fatty infiltration

Explanation

MIS TLIF utilizes muscle-splitting approaches (like the Wiltse approach or tubular dilators) that minimize stripping of the multifidus from its bony attachments. This significantly decreases postoperative multifidus atrophy, fatty infiltration, and denervation compared to open approaches.

Question 211

Topic: 1. General Principles & Basic Science

During a minimally invasive unilateral TLIF with bilateral decompression (over-the-top technique), the surgeon undercuts the spinous process to decompress the contralateral side. Which structure must be preserved to prevent iatrogenic instability?

. Contralateral facet joint
. Ipsilateral ligamentum flavum
. Interspinous ligament
. Supraspinous ligament
. Contralateral pedicle

Correct Answer & Explanation

. Contralateral facet joint

Explanation

The over-the-top technique allows bilateral decompression through a unilateral tubular approach by undercutting the spinous process and contralateral lamina. It is crucial to preserve the contralateral facet joint to avoid creating iatrogenic instability.

Question 212

Topic: 1. General Principles & Basic Science

When performing an anterior lumbar interbody fusion (ALIF) at L4-L5, the surgeon encounters massive venous bleeding from a large vessel situated directly anterior to the L4-L5 disc space. Which vessel is most likely injured?

. Right common iliac vein
. Left common iliac vein
. Inferior vena cava
. Middle sacral vein
. Iliolumbar vein

Correct Answer & Explanation

. Left common iliac vein

Explanation

The left common iliac vein courses directly anterior to the L4-L5 disc space before joining the right common iliac vein to form the inferior vena cava. It is at highest risk during exposure for an L4-L5 ALIF.

Question 213

Topic: Surgical Anatomy & Approaches

Retrograde ejaculation is a known complication of anterior lumbar interbody fusion (ALIF). This is caused by injury to the:

. Parasympathetic pelvic splanchnic nerves
. Pudendal nerve
. Superior hypogastric plexus
. Genitofemoral nerve
. Ilioinguinal nerve

Correct Answer & Explanation

. Superior hypogastric plexus

Explanation

Retrograde ejaculation occurs due to injury to the superior hypogastric plexus (sympathetic nerves), which lies anterior to the lower lumbar vertebrae and L5-S1 disc space. Careful blunt dissection and avoiding electrocautery over the disc space minimizes this risk.

Question 214

Topic: 1. General Principles & Basic Science

Compared to an open Transforaminal Lumbar Interbody Fusion (TLIF), a minimally invasive (MIS) TLIF is characteristically associated with which of the following?

. Increased multifidus muscle atrophy
. Significantly reduced surgeon radiation exposure
. Lower estimated intraoperative blood loss
. Higher long-term (5-year) fusion rates
. Shorter surgical learning curve

Correct Answer & Explanation

. Lower estimated intraoperative blood loss

Explanation

MIS TLIF provides lower estimated intraoperative blood loss, shorter hospital stays, and less muscle damage compared to open TLIF. Long-term fusion rates and clinical outcomes are generally equivalent, while radiation exposure and the learning curve are increased.

Question 215

Topic: 1. General Principles & Basic Science

When performing a minimally invasive posterior lumbar approach using tubular retractors via a paramedian incision, the surgeon typically utilizes the natural intermuscular plane (Wiltse plane) located between the:

. Multifidus and Longissimus muscles
. Longissimus and Iliocostalis muscles
. Multifidus and Spinalis muscles
. Psoas major and Quadratus lumborum muscles
. Spinalis and Interspinales muscles

Correct Answer & Explanation

. Multifidus and Longissimus muscles

Explanation

The Wiltse paraspinal approach utilizes the avascular cleavage plane between the multifidus (medial) and longissimus (lateral) muscles. This minimizes denervation and ischemic injury to the paraspinal musculature.

Question 216

Topic: 1. General Principles & Basic Science

During the placement of a percutaneous pedicle screw for an MIS TLIF, what is the ideal starting point for the Jamshidi needle on the true anteroposterior (AP) fluoroscopic view before advancing into the pedicle?

. The medial border of the pedicle shadow
. The lateral border of the pedicle shadow at the 3 or 9 o'clock position
. The exact center of the pedicle shadow
. The superior border of the pedicle shadow
. The inferior border of the pedicle shadow

Correct Answer & Explanation

. The lateral border of the pedicle shadow at the 3 or 9 o'clock position

Explanation

To ensure an in-to-in trajectory without violating the medial pedicle wall early, the starting point on the AP view is at the lateral border of the pedicle (3 o'clock for right, 9 o'clock for left). The needle should not cross the medial border until it has passed the posterior vertebral body wall on the lateral view.

Question 217

Topic: 1. General Principles & Basic Science

Which of the following neural structures is at the greatest risk of iatrogenic injury during the annulotomy and disc preparation phase of a minimally invasive transforaminal lumbar interbody fusion (MIS TLIF)?

. Traversing nerve root
. Exiting nerve root
. Sympathetic trunk
. Superior gluteal nerve
. Pudendal nerve

Correct Answer & Explanation

. Traversing nerve root

Explanation

The MIS TLIF approach utilizes Kambin's triangle. The exiting nerve root forms the anterior/lateral boundary of this triangle and is highly vulnerable to injury from retractor placement and aggressive disc preparation.

Question 218

Topic: Surgical Anatomy & Approaches

A 60-year-old male undergoes a minimally invasive extreme lateral interbody fusion (XLIF) at L4-L5. Postoperatively, he presents with profound weakness in hip flexion and knee extension, along with anterior thigh numbness. Which structure was most likely injured?

. Sciatic nerve
. Superior gluteal nerve
. Lumbar plexus
. Sympathetic chain
. Ilioinguinal nerve

Correct Answer & Explanation

. Lumbar plexus

Explanation

The lateral transpsoas approach (XLIF/DLIF) risks injury to the lumbar plexus, which lies within the posterior third of the psoas major muscle. This risk is highest at the L4-L5 level.

Question 219

Topic: 1. General Principles & Basic Science

During a minimally invasive tubular decompression, an incidental durotomy occurs

. What is the most appropriate initial management step?

. Immediate conversion to an open approach for primary repair
. Application of an epidural blood patch
. Attempt primary repair through the tube or use dural sealants/patches if direct repair is impossible
. Place a subfascial drain on high wall suction
. Abandon the procedure and close the fascia

Correct Answer & Explanation

. Attempt primary repair through the tube or use dural sealants/patches if direct repair is impossible

Explanation

Incidental durotomies during MIS procedures can often be managed through the tube using specialized MIS suturing instruments, dural patches, or sealants. Conversion to an open approach is reserved for large, unmanageable tears.

Question 220

Topic: 1. General Principles & Basic Science

During an endoscopic transforaminal lumbar discectomy, accessing the L5-S1 disc space is often technically limited or prevented by which anatomical structure?

. Psoas major muscle
. Iliac crest
. Abdominal aorta
. Twelfth rib
. Sacrotuberous ligament

Correct Answer & Explanation

. Iliac crest

Explanation

A high iliac crest frequently obstructs the lateral trajectory required for a transforaminal endoscopic approach to L5-S1. Therefore, an interlaminar endoscopic approach is often preferred at this level.

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