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Thoracolumbar Spine & Deformity MCQs

Practice Set 2 of 49

This practice set contains high-yield board review questions covering key concepts in Thoracolumbar Spine & Deformity. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 21

Topic: Thoracolumbar Spine & Deformity

Which of the following equations correctly defines the relationship between spinopelvic parameters?

. PI = PT - SS
. PI = PT + SS
. PT = PI + SS
. SS = PI + PT
. PI = SS - PT

Correct Answer & Explanation

. PI = PT + SS

Explanation

Pelvic incidence (PI) is a fixed morphological parameter defined as the sum of pelvic tilt (PT) and sacral slope (SS). Therefore, PI = PT + SS.

Question 22

Topic: Thoracolumbar Spine & Deformity

Which of the following spinopelvic parameters is considered a fixed morphological parameter that does not change with posture after skeletal maturity?

. Pelvic tilt
. Sacral slope
. Lumbar lordosis
. Pelvic incidence
. Sagittal vertical axis

Correct Answer & Explanation

. Pelvic incidence

Explanation

Pelvic incidence is a fixed anatomical parameter dictated by the morphology of the pelvis. It remains constant regardless of posture, unlike pelvic tilt and sacral slope which act as dynamic compensatory parameters.

Question 23

Topic: Thoracolumbar Spine & Deformity

When planning surgical correction for adult spinal deformity, the generally accepted target for lumbar lordosis (LL) relative to pelvic incidence (PI) is:

. LL should equal PI + 20 degrees
. LL should be within 10 degrees of PI
. LL should be exactly half of the PI
. LL should equal PI - 20 degrees
. LL is independent of PI

Correct Answer & Explanation

. LL should be within 10 degrees of PI

Explanation

For optimal sagittal balance, the lumbar lordosis should be matched to the patient's pelvic incidence. The widely accepted target for correction is to have PI minus LL be less than or equal to 10 degrees.

Question 24

Topic: Thoracolumbar Spine & Deformity

As a patient develops positive sagittal imbalance due to age-related degenerative loss of lumbar lordosis, which of the following compensatory mechanisms initially occurs at the pelvis?

. Decreased pelvic tilt
. Decreased sacral slope
. Increased sacral slope
. Decreased pelvic incidence
. Increased pelvic incidence

Correct Answer & Explanation

. Decreased sacral slope

Explanation

To compensate for a loss of lumbar lordosis and an anterior shift of the sagittal vertical axis, the pelvis retroverts. This pelvic retroversion results in an increased pelvic tilt and a reciprocally decreased sacral slope.

Question 25

Topic: Thoracolumbar Spine & Deformity

Which of the following spinopelvic parameter profiles is most characteristically associated with a high risk of progression in L5-S1 isthmic spondylolisthesis?

. Low pelvic incidence and high sacral slope
. High pelvic incidence and high sacral slope
. Low pelvic incidence and low sacral slope
. High pelvic incidence and low pelvic tilt
. Low pelvic tilt and high sacral slope

Correct Answer & Explanation

. High pelvic incidence and high sacral slope

Explanation

High pelvic incidence forces a correspondingly high sacral slope, which exponentially increases anterior shear forces at the L5-S1 junction. This specific profile is strongly associated with the development and progression of isthmic spondylolisthesis.

Question 26

Topic: Thoracolumbar Spine & Deformity

In an individual standing upright, if the pelvic incidence is 50 degrees and the pelvic tilt is 15 degrees, what is the orientation of the sacral endplate relative to the horizontal plane?

. 15 degrees
. 35 degrees
. 50 degrees
. 65 degrees
. 0 degrees

Correct Answer & Explanation

. 35 degrees

Explanation

The sacral slope (SS) is defined as the angle of the sacral endplate relative to the horizontal plane. Since Pelvic Incidence = Pelvic Tilt + Sacral Slope, the SS must be 35 degrees (50 - 15 = 35).

Question 27

Topic: Thoracolumbar Spine & Deformity

According to the Roussouly classification of sagittal alignment, a Type 1 spine is typically characterized by which of the following features?

. High pelvic incidence and high sacral slope
. Low sacral slope (<35 degrees) with a long thoracolumbar kyphosis and short lumbar lordosis
. Normal sacral slope with an evenly distributed lumbar lordosis
. High pelvic incidence (>60 degrees) with severe global kyphosis
. Normal pelvic incidence but a completely flat lumbar spine

Correct Answer & Explanation

. Low sacral slope (<35 degrees) with a long thoracolumbar kyphosis and short lumbar lordosis

Explanation

In the Roussouly classification, Type 1 is characterized by a low sacral slope (less than 35 degrees) and a low pelvic incidence. The lumbar lordosis is notably short and concentrated distally, coupled with a prominent thoracolumbar kyphosis.

Question 28

Topic: Thoracolumbar Spine & Deformity

A 65-year-old woman presents with progressive low back pain and leaning forward while walking. Radiographs reveal a pelvic incidence (PI) of 60 degrees. Which of the following formulas correctly defines the relationship between pelvic incidence, pelvic tilt (PT), and sacral slope (SS)?

. PI = PT - SS
. PI = SS - PT
. PI = PT + SS
. PT = PI + SS
. SS = PI + PT

Correct Answer & Explanation

. PI = PT + SS

Explanation

Pelvic incidence is a fixed morphological parameter defined as the sum of pelvic tilt and sacral slope (PI = PT + SS). It dictates the required lumbar lordosis for a patient to achieve sagittal balance.

Question 29

Topic: Thoracolumbar Spine & Deformity

In surgical planning for an adult patient with severe sagittal imbalance, the surgeon calculates the patient's pelvic incidence (PI) to be 55 degrees. To achieve optimal postoperative sagittal alignment and minimize the risk of adjacent segment disease, the target lumbar lordosis (LL) should be:

. 15 to 25 degrees
. 25 to 35 degrees
. 45 to 65 degrees
. 75 to 85 degrees
. Matched to the thoracic kyphosis exactly

Correct Answer & Explanation

. 45 to 65 degrees

Explanation

For optimal sagittal balance, the lumbar lordosis (LL) should match the pelvic incidence (PI) within 10 degrees (PI - LL < 10 degrees). Therefore, a PI of 55 degrees requires an LL of approximately 45 to 65 degrees.

Question 30

Topic: Thoracolumbar Spine & Deformity

Which of the following compensatory mechanisms occurs FIRST in a patient developing progressive positive sagittal spinal imbalance?

. Knee flexion
. Hip flexion
. Pelvic retroversion
. Ankle plantarflexion
. Cervical kyphosis

Correct Answer & Explanation

. Pelvic retroversion

Explanation

The initial compensatory mechanism for positive sagittal imbalance is pelvic retroversion, which increases pelvic tilt (PT) and decreases sacral slope (SS). As the deformity worsens and pelvic compensation is exhausted, knee flexion and hip extension occur.

Question 31

Topic: Thoracolumbar Spine & Deformity

Which of the following radiographic parameters is considered a rigid, position-independent morphological feature of the pelvis that does NOT change with patient posture?

. Pelvic Tilt (PT)
. Sacral Slope (SS)
. Sagittal Vertical Axis (SVA)
. Pelvic Incidence (PI)
. T1 Pelvic Angle (T1PA)

Correct Answer & Explanation

. Pelvic Incidence (PI)

Explanation

Pelvic incidence (PI) is an anatomical parameter fixed at skeletal maturity and does not change with posture. Pelvic tilt, sacral slope, and SVA are dynamic parameters that alter with the patient's positional compensatory mechanisms.

Question 32

Topic: Thoracolumbar Spine & Deformity

Which of the following spinopelvic profiles is most classically associated with the development and progression of high-grade isthmic spondylolisthesis (e.g., L5-S1) in an adolescent?

. Low Pelvic Incidence (PI)
. High Pelvic Incidence (PI)
. Low Pelvic Tilt (PT)
. Negative Sagittal Vertical Axis (SVA)
. Decreased Lumbar Lordosis

Correct Answer & Explanation

. High Pelvic Incidence (PI)

Explanation

High pelvic incidence (PI) is a primary predisposing factor for the development and progression of isthmic spondylolisthesis. A higher PI requires a higher sacral slope and compensatory lumbar lordosis, increasing the shear forces across the L5-S1 pars interarticularis.

Question 33

Topic: Thoracolumbar Spine & Deformity

Which of the following describes the mathematical relationship between pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS)?

. PI = PT - SS
. PI = PT + SS
. PT = PI + SS
. SS = PI + PT
. PI = (PT + SS) / 2

Correct Answer & Explanation

. PI = PT + SS

Explanation

Pelvic incidence is a fixed morphological parameter determined by the equation PI = PT + SS. As an individual changes position, PT and SS vary inversely to maintain a constant PI.

Question 34

Topic: Thoracolumbar Spine & Deformity

In an aging patient developing progressive sagittal imbalance (positive sagittal vertical axis), which of the following is the primary initial compensatory mechanism at the pelvis?

. Pelvic anteversion (decreased pelvic tilt)
. Pelvic retroversion (increased pelvic tilt)
. Increased sacral slope
. Decreased pelvic incidence
. Hip flexion

Correct Answer & Explanation

. Pelvic retroversion (increased pelvic tilt)

Explanation

To compensate for a positive sagittal vertical axis (forward leaning), the body retroverts the pelvis, which increases pelvic tilt (PT) and decreases sacral slope (SS). Knee flexion and cervical hyperlordosis are secondary compensations.

Question 35

Topic: Thoracolumbar Spine & Deformity

Sorensen's criteria for the radiographic diagnosis of Scheuermann's disease requires anterior wedging of at least 5 degrees in how many consecutive vertebrae?

. Two
. Three
. Four
. Five
. Six

Correct Answer & Explanation

. Three

Explanation

Scheuermann's kyphosis is classically defined by Sorensen criteria, which require anterior wedging of 5 degrees or more in at least three adjacent vertebrae. It typically involves rigid thoracic hyperkyphosis and Schmorl's nodes.

Question 36

Topic: Thoracolumbar Spine & Deformity

Which pelvic parameter is typically significantly elevated in patients with high-grade dysplastic spondylolisthesis compared to the normal population?

. Pelvic tilt
. Sacral slope
. Pelvic incidence
. Thoracic kyphosis
. Lumbar lordosis

Correct Answer & Explanation

. Pelvic incidence

Explanation

A high Pelvic Incidence (PI) increases shear forces at the lumbosacral junction and is strongly associated with the development and progression of isthmic and dysplastic spondylolisthesis.

Question 37

Topic: Thoracolumbar Spine & Deformity

With normal aging, which of the following sequences best represents the typical cascade of sagittal spinal alignment changes?

. Loss of lumbar lordosis, forward shift of SVA, pelvic retroversion, knee flexion
. Increase in lumbar lordosis, backward shift of SVA, pelvic anteversion, hip extension
. Loss of thoracic kyphosis, decreased pelvic incidence, knee extension
. Increased pelvic tilt, increased sacral slope, loss of thoracic kyphosis
. Cervical hyperkyphosis, lumbar hyperlordosis, pelvic anteversion

Correct Answer & Explanation

. Loss of lumbar lordosis, forward shift of SVA, pelvic retroversion, knee flexion

Explanation

Aging typically causes disc degeneration and loss of lumbar lordosis, leading to a positive (forward) sagittal vertical axis (SVA). The body compensates sequentially via pelvic retroversion (increased PT), hip extension, and finally knee flexion.

Question 38

Topic: Thoracolumbar Spine & Deformity

When a healthy individual transitions from a standing to a seated position, how do the pelvic parameters normally adjust?

. Pelvic tilt increases and sacral slope decreases
. Pelvic tilt decreases and sacral slope increases
. Pelvic incidence increases significantly
. Both pelvic tilt and sacral slope increase
. Pelvic parameters remain completely static

Correct Answer & Explanation

. Pelvic tilt increases and sacral slope decreases

Explanation

During sitting, the pelvis undergoes retroversion to accommodate hip flexion and maintain trunk balance. This results in an increased pelvic tilt (PT) and a correspondingly decreased sacral slope (SS), while pelvic incidence (PI) remains constant.

Question 39

Topic: Thoracolumbar Spine & Deformity

According to the Meyerding grading system for spondylolisthesis, a slip of 60% of the superior vertebral body over the inferior vertebral body is classified as:

. Grade 1
. Grade 2
. Grade 3
. Grade 4
. Spondyloptosis

Correct Answer & Explanation

. Grade 3

Explanation

The Meyerding classification grades slip percentage as follows: Grade 1 (0-25%), Grade 2 (26-50%), Grade 3 (51-75%), Grade 4 (76-100%), and Spondyloptosis (>100%). A 60% slip falls into Grade 3.

Question 40

Topic: Thoracolumbar Spine & Deformity

What is the fundamental mathematical relationship between Pelvic Incidence (PI), Pelvic Tilt (PT), and Sacral Slope (SS) in spino-pelvic alignment?

. PI = PT + SS
. PI = PT - SS
. PT = PI + SS
. SS = PI + PT
. PI = (PT + SS) / 2

Correct Answer & Explanation

. PI = PT + SS

Explanation

Pelvic incidence is a fixed morphological parameter defined as the sum of pelvic tilt and sacral slope (PI = PT + SS). It dictates the required lumbar lordosis for optimal sagittal balance.

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