USMLE Step 1 Question 338

Question:

A 71-year-old man presents to his primary care provider complaining of nonradiating lower back pain over the past several months.
On review of symptoms, he mentions feeling shorter than previously. Physical exam reveals a slight abnormal curve of the spine.
Radiographic studies show anterior vertebral wedging and vertebral end-plate irregularity.
What is the most likely underlying pathology of this process?

Correct Answer: A.  Decreased osteoblast activity, normal osteoclast activity

This patient is suffering from a compression fracture secondary to osteoporosis. Decreased osteoblast activity with normal osteoclast activity (choice A) will result in an overall decrease in bone density. This process occurs in primary osteoporosis type 2 (“senile osteoporosis”), which occurs in patients over 60 of both genders.
Increased osteoblast activity with decreased osteoclast activity (choice B) will result in an overall increase in bone density. This process is not associated with vertebral compression fractures.
Intervertebral disc degeneration (choice C) leads to disc herniation. This condition can cause lower back pain secondary to nerve root compression, classically radiating to the upper legs (“sciatica”). This pathology is inconsistent with the observed radiographic studies.
Intervertebral disc space calcification (choice D) typically affects preadolescent children. It usually is found in the thoracic and lumbar spine, and the course is self-limited.
Decreased osteoblast activity with increased osteoclast activity (choice E) will result in an overall decrease in bone density and may lead to a vertebral compression fracture. This process occurs in primary osteoporosis type 1 (“postmenopausal osteoporosis”), which is six times more common in women. In this process, loss of estrogen is thought to increase cytokine levels promoting osteoclast activity.