NERVE INJURIES OF THE UPPER LIMB
A surgical neck fracture of the humerus flattens the shoulder contour and causes lateral-arm numbness; this nerve, tested by abducting against resistance from 15°, is injured.
What is the axillary nerve?
A fall on an outstretched hand in someone over 50 dorsally displaces and comminutes the distal radius, producing this named fracture with a dinner-fork deformity.
What is a Colles fracture?
Activation of this receptor on vascular smooth muscle causes vasoconstriction and raised blood pressure—and also produces mydriasis via the iris dilator.
What is the α₁ receptor?
Compression of the median nerve in the carpal tunnel wastes this muscle group, and the surgical incision is placed medially to spare the recurrent branch.
What are the thenar muscles?
This rotator cuff tendon is the most commonly torn, and its rupture prevents initiating the first 15° of abduction.
What is the supraspinatus?
A mid-shaft humeral fracture produces wrist-drop with only minimal sensory loss on the dorsum of the hand because this nerve was injured in the radial groove.
What is the radial nerve?
A fall on the palm with the hand abducted causes lateral wrist pain; this carpal bone fractures at its waist and risks avascular necrosis of the proximal fragment from poor blood supply.
What is the scaphoid?
A drug that speeds heart rate and increases contractility is working through this cardiac receptor.
What is the β₁ receptor?
Repetitive wrist extension inflames the common extensor tendon origin here, producing lateral elbow pain known as tennis elbow.
What is the lateral epicondyle?
Rupture of the long head of biceps at the supraglenoid tubercle produces this named bulge as the muscle belly balls up.
What is a Popeye deformity?
A laceration at the wrist wastes the thenar eminence and abolishes thumb opposition, but central palm sensation is spared because this nerve’s palmar cutaneous branch bypasses the carpal tunnel.
What is the median nerve?
After a mid-clavicle fracture—its weakest point at the junction of middle and lateral thirds—the SCM elevates the medial fragment while the lateral fragment drops; naming this muscle that normally holds the lateral fragment up explains the sag.
What is the trapezius?
During exercise, skeletal muscle vessels dilate while skin vessels constrict; naming the receptor driving the skeletal-muscle vasodilation—opposite the α₁ constriction in skin—is the answer.
What is the β₂ receptor?
An anterior dislocation of this carpal bone onto the palmar wrist can compress the median nerve and, from poor blood supply, undergo avascular necrosis.
What is the lunate?
An anterior glenohumeral dislocation most often occurs in young athletes from excessive extension and lateral rotation, risking injury to this nerve near the inferior capsule.
What is the axillary nerve?
A hook-of-hamate fracture or elbow injury produces a claw hand with hyperextended MCPs; naming this nerve, whose loss lets unopposed extensors and FDP deform the 4th and 5th digits, is the answer.
What is the ulnar nerve?
Long thoracic nerve injury paralyzes this muscle, producing a winged scapula and inability to abduct above horizontal because the glenoid can’t be rotated superiorly.
What is the serratus anterior?
This receptor slows the heart when stimulated, and is the one blocked at the SA node when atropine is given.
What is the M₂ receptor?
Ulnar nerve compression at the wrist occurs in this osseofibrous canal between the pisiform and hook of hamate, roofed by the pisohamate ligament.
What is Guyon’s canal (the ulnar tunnel)?
A hard fall onto the shoulder that tears both the AC and coracoclavicular ligaments produces this “shoulder separation,” making the acromion prominent.
What is an acromioclavicular joint dislocation?
A newborn delivered with excessive neck traction holds the limb adducted, medially rotated, and extended—the waiter’s tip position; naming this injury of the C5–C6 superior trunk is the answer, not the C8–T1 claw-hand palsy.
What is Erb-Duchenne palsy (upper brachial plexus injury)?
Sudden laceration of the brachial artery proximal to the deep artery of the arm causes muscle ischemia that fibroses into a permanent flexion deformity; naming this contracture is the answer.
What is Volkmann ischemic contracture?
Atropine causes dry mouth, blurred near vision, urinary retention, and constipation; naming this receptor—responsible for salivation, miosis, GI activity, and bladder contraction when active—explains the whole blockade picture.
What is the M₃ receptor?
Tenosynovitis of the little finger can spread to the forearm because this finger’s synovial sheath is usually continuous with the common flexor sheath passing through the carpal tunnel.
What is the 5th digit (little finger)?
A child jerked up by a pronated forearm cries and refuses to use the arm; naming this subluxation, caused by the radial head slipping from a torn anular ligament, is the answer.
What is nursemaid’s elbow (subluxation of the radial head)?