A 36-year-old male is taken to the emergency room after jumping from a building. Bilateral fractures to the femur were stabilized at the scene by emergency medical technicians. The patient is lucid upon questioning and his vitals are stable. Pain only at his hips was elicited. Cervical exam was not performed. What is the best imaging study for this patient?

Computed tomography (CT) scan of cervical spine, hips, and lumbar area

AP and lateral radiographs of hips

Lateral radiograph (x-ray) of hips

Magnetic resonance imaging (MRI) of hips, knees, lumbar, and cervical area

Anterior-posterior (AP) and lateral radiographs of hips, knees, lumbar, and cervical area

A 54-year-old man presents to his primary care physician for back pain. His back pain worsens with standing for a prolonged period of time or climbing down the stairs and improves with sitting. Medical history is significant for hypertension, type II diabetes mellitus, and hypercholesterolemia. Neurologic exam demonstrates normal tone, 5/5 strength, and a normal sensory exam throughout the bilateral lower extremity. Skin exam is unremarkable and dorsalis pedis and posterior tibialis pulses are 3+. Which of the following is the best next step in management?

Radiography of the lumbosacral spine

A 14-year-old boy is brought to the emergency department because of acute left-sided chest pain and dyspnea following a motor vehicle accident. His pulse is 122/min and blood pressure is 85/45 mm Hg. Physical examination shows distended neck veins and tracheal displacement to the right side. The left chest is hyperresonant to percussion and there are decreased breath sounds. This patient would most benefit from needle insertion at which of the following anatomical sites?

2nd left intercostal space along the midclavicular line

5th left intercostal space along the midclavicular line

8th left intercostal space along the posterior axillary line

Subxiphoid space in the left sternocostal margin

5th left intercostal space along the midaxillary line

A 51-year-old woman comes to the physician because of progressively worsening lower back pain. The pain radiates down the right leg to the lateral side of the foot. She has had no trauma, urinary incontinence, or fever. An MRI of the lumbar spine shows disc degeneration and herniation at the level of L5–S1. Which of the following is the most likely finding on physical examination?

Exaggerated patellar tendon reflex

Diminished sensation of the anus and genitalia

Diminished sensation of the anterior lateral thigh

A 50-year-old man presents with severe chest pain for a week. His pain increases with breathing and is localized to the right. He has tried over-the-counter medications at home, but they did not help. The patient has a 20-pack-year smoking history and currently smokes 2 packs of cigarettes daily, and he drinks 3 to 4 cans of beer daily before dinner. His temperature is 39.1°C (102.3°F), blood pressure is 127/85 mm Hg, pulse is 109/min, and respirations are 20/min. Respiratory examination shows dullness to percussion from the 7th rib inferiorly at the right midaxillary line, decreased vocal tactile fremitus, and diminished breath sounds in the same area. Chest radiograph is shown in the image. The patient is prepared for thoracocentesis. Which of the following locations would be the most appropriate for insertion of a chest tube?

Above the superior border of the 8th rib in the midaxillary line

Below the inferior border of the 7th rib in the midaxillary line

Above the superior border of the 5th rib in the midclavicular line

Below the inferior border of the 5th rib in the midaxillary line

Above the superior border of the 7th rib in the midclavicular line

Spinal radiologic landmarks for USMLE Step 3: High-Yield Anatomy Lessons

Cervical Spine - Neck Navigator

Lateral View: The most critical view for assessing alignment and stability. Check for the smooth continuity of 3 key parallel lines:
- Anterior vertebral line
- Posterior vertebral line
- Spinolaminar line
Key Measurements:
- Predental Space (ADI): Distance between the dens (C2) and the anterior arch of C1. Must be <3 mm in adults and <5 mm in children.
- Basion-Dens Interval (BDI): Distance from the basion to the tip of the dens. Should be <12 mm.
Odontoid (Open-Mouth) View:
- Crucial for C1-C2 articulation.
- The lateral masses of C1 should align perfectly with the superior articular facets of C2.

⭐ A widened predental space (>3 mm in adults) is a red flag for transverse ligament rupture and atlantoaxial instability, a potential emergency seen in severe trauma or rheumatoid arthritis.

Thoracic Spine - Rib Cage Ruler

Thoracic Spine Vertebral Levels & Mediastinal Structures

Use the rib cage and sternum as a "ruler" to locate underlying structures on imaging. Key anterior landmarks correspond to specific thoracic vertebral levels, providing a quick orientation.

T2-T3: Suprasternal (jugular) notch.
T4-T5: Sternal Angle of Louis.
T8: Caval opening for the Inferior Vena Cava (IVC) in the diaphragm.
T9: Xiphoid process.
T10: Esophageal hiatus in the diaphragm.
T12: Aortic hiatus (with thoracic duct and azygos vein).

⭐ The Sternal Angle of Louis (T4-T5 disc space) is a critical landmark. It marks the carina, aortic arch, pulmonary trunk bifurcation, and azygos vein draining into the SVC.

📌 Mnemonic for diaphragmatic hiatuses: "I 8 10 Eggs At 12" (IVC at T8, Esophagus at T10, Aorta at T12).

Lumbosacral Spine - Low-Back Locator

Key palpable and radiological landmarks for safe procedural access and diagnosis in the lower back region.

AP and Lateral Lumbosacral Spine X-ray with Labeled Anatomy

Anatomic Landmark	Typical Vertebral Level	Clinical Relevance
Iliac Crest	L4 Body or L4-L5 IV Disc	Tuffier's Line: Connects highest points of iliac crests; guides lumbar puncture.
Conus Medullaris	L1-L2	Spinal cord termination. To avoid injury, LP is performed at L3-L4 or L4-L5.
Dural Sac End	S2	End of the thecal sac containing CSF. Relevant for caudal epidural anesthesia.
PSIS	S2	Posterior Superior Iliac Spine. Surface landmark for the sacroiliac (SI) joint.

⭐ In adults, the spinal cord (conus medullaris) terminates at the L1-L2 level. A lumbar puncture needle inserted above this level risks iatrogenic spinal cord injury.

High-Yield Points - ⚡ Biggest Takeaways

C2-C3 interspace is level with the hyoid bone.

C4 vertebra corresponds to the thyroid cartilage (Adam's apple).

C6 vertebra aligns with the cricoid cartilage and carotid tubercle.

T4/T5 interspace marks the sternal angle of Louis and aortic arch.

The conus medullaris typically terminates at the L1-L2 level in adults.

Lumbar puncture is safely performed at the L3/L4 or L4/L5 interspace, level with the iliac crests.

The dural sac (thecal sac) containing CSF ends at the S2 vertebral level.

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