A 61-year-old woman comes to the physician for a follow-up examination 1 week after undergoing right-sided radical mastectomy and axillary lymph node dissection for breast cancer. She says that she has been unable to comb her hair with her right hand since the surgery. Physical examination shows shoulder asymmetry. She is unable to abduct her right arm above 90 degrees. When she pushes against a wall, there is protrusion of the medial aspect of the right scapula. Injury to which of the following nerves is the most likely cause of this patient's condition?

Upper trunk of the brachial plexus

A 25-year-old man comes to the physician because of right wrist pain after a fall from a ladder. Physical examination shows decreased grip strength and tenderness between the tendons of extensor pollicis longus and extensor pollicis brevis. X-ray of the right wrist shows no abnormalities. This patient is at increased risk for which of the following complications?

Avascular necrosis of the scaphoid bone

Hypesthesia of the hypothenar eminence

Paralysis of the abductor pollicis brevis muscle

Contracture of the palmar aponeurosis

Osteoarthritis of the radiocarpal joint

A 32-year-old man comes to the physician because of a 1-month history of intermittent tingling of his hand. He is an avid cyclist and has recently started training for a cycle marathon. Physical examination shows decreased grip strength in the right hand and wasting of the hypothenar eminence. On asking the patient to grasp a piece of paper between his right thumb and right index finger in the first web space, there is hyperflexion of the right thumb interphalangeal joint. Which of the following additional findings is most likely in this patient?

Inability to extend the little finger at the proximal interphalangeal joints

Loss of sensation over the dorsum of the medial half of the hand

Inability to extend the ring finger at the metacarpophalangeal joint

Inability to flex the index finger at the interphalangeal joints

Loss of sensation over the palmar aspect of the middle finger

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

"Can you tell me more about the symptoms you have been experiencing?"

"Does the diarrhea typically precede the constipation, or vice-versa?"

"Is the diarrhea foul-smelling?"

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

"Are the symptoms worse in the morning or at night?"

A 67-year-old male presents to his primary care physician for evaluation of fever and an unintended weight loss of 25 pounds over the last 4 months. He also has decreased appetite and complains of abdominal pain located in the right upper quadrant. The patient has not noticed any changes in stool or urine. He emigrated from Malaysia to the United States one year prior. Social history reveals that he smokes half a pack per day and has 5-7 drinks of alcohol per day. The patient is up to date on all of his vaccinations. Physical exam findings include mild jaundice as well as an enlarged liver edge that is tender to palpation. Based on clinical suspicion, biomarker labs are sent and show polycythemia and an elevated alpha fetoprotein level but a normal CA 19-9 level. Surface antigen for hepatitis B is negative. Ultrasound reveals a normal sized gallbladder. Given this presentation, which of the following organisms was most likely associated with the development of disease in this patient?

Trematode from undercooked fish

Upper limb surface landmarks for USMLE Step 3: High-Yield Anatomy Lessons

Shoulder & Axilla - Proximal Peaks

Clavicle: Palpable S-shaped bone. Its mid-lateral junction is a common fracture site.
Acromion: The bony "tip" of the shoulder, articulating with the clavicle (AC joint).
Coracoid Process: Deep to the deltopectoral triangle; a key surgical landmark.
Greater Tubercle of Humerus: Most lateral bony point; attachment for three rotator cuff muscles (SIT).
Deltopectoral Triangle: Depression inferior to the clavicle, bordered by the deltoid and pectoralis major. Houses the cephalic vein.
Axillary Folds: Anterior (pectoralis major) and posterior (latissimus dorsi, teres major) borders of the armpit.

Clavicle and Acromion Process

⭐ A fracture of the surgical neck of the humerus, located just distal to the tubercles, can damage the axillary nerve and posterior circumflex humeral artery.

Arm & Elbow - Brachial Bends

Biceps Brachii & Tendon: Palpable in the anterior arm; tendon is felt in the center of the cubital fossa.
Brachial Artery Pulse: Medial to the biceps tendon in the cubital fossa. Key site for blood pressure cuff placement.
Cubital Fossa: Triangular space anterior to the elbow.
- Contents (Medial to Lateral): 📌 My Blood Turns Red: Median nerve, Brachial artery, Biceps tendon, Radial nerve (deep).
Humerus Epicondyles:
- Medial: "Funny bone"; ulnar nerve is posterior.
- Lateral: Common extensor tendon origin.

Upper Limb Surface Anatomy: Anterior and Posterior Views

⭐ The median cubital vein, which connects the basilic and cephalic veins, lies superficially in the cubital fossa roof and is the preferred site for venipuncture.

Forearm & Wrist - Snuffbox & Pulses

Anatomical Snuffbox: A triangular depression on the dorsolateral aspect of the wrist, best seen when the thumb is extended.
- Borders:
  - Lateral (Anterior): Tendons of Abductor Pollicis Longus (APL) & Extensor Pollicis Brevis (EPB).
  - Medial (Posterior): Tendon of Extensor Pollicis Longus (EPL).
- Floor: Scaphoid and trapezium bones.
- Contents: Radial artery.

Anatomical Snuffbox Boundaries

Pulse Points:
- Radial Pulse: Lateral to the flexor carpi radialis tendon.
- Ulnar Pulse: Lateral to the flexor carpi ulnaris tendon.

⭐ Tenderness in the anatomical snuffbox upon palpation is a classic sign of a scaphoid fracture. This injury carries a high risk of avascular necrosis due to its tenuous, retrograde blood supply from the radial artery.

Hand Landmarks - Grip & Grasp

Power Grip: Forceful grasp using extrinsic flexors (FDP, FDS) and intrinsic muscles.
- Nerves: Median & Ulnar.
Precision Grip: Fine control via intrinsic muscles.
- Thenar Eminence (Median n.): Thumb opposition.
- Interossei/Lumbricals (Ulnar/Median n.): Fine finger movements.

Hand grips: precision and power

⭐ Froment's Sign: Test for ulnar nerve palsy. Weak adductor pollicis (ulnar n.) is compensated by FPL (median n.), causing thumb IP joint flexion when gripping paper.

High‑Yield Points - ⚡ Biggest Takeaways

Axillary artery pulse is palpated in the axilla, inferiorly against the humerus.

Brachial artery pulse is found medial to the biceps tendon in the cubital fossa.

Radial artery pulse is taken lateral to the flexor carpi radialis tendon at the wrist.

Tenderness in the anatomical snuffbox strongly suggests a scaphoid fracture.

The ulnar nerve is palpable (and vulnerable) posterior to the medial epicondyle.

The deltoid muscle is a primary site for intramuscular injections.

The cephalic vein in the deltopectoral groove is a key site for IV access.

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