Nerve injuries
A 19-year-old college student sustains a midshaft humerus fracture after a cycling crash. On physical exam, he is unable to extend his wrist or digits, resulting in a wrist drop. What nerve is affected here?
What is the Radial nerve? (following the A-R-M mnemonic: Surgical neck = Axillary, Midshaft = Radial, Supracondylar = Median)
- Midshaft humeral fractures damage the radial nerve in the spiral groove, paralyzing forearm extensors while usually sparing the triceps.
During a cadaver lab review, an instructor asks which forearm bone directly articulates with the proximal carpal row at the radiocarpal joint?
What is the Radius?
- radius articulates with the articular disc, scaphoid, lunate, and triquetrum.
- the radiocarpal joint is formed by the distal radius and triangular fibrocartilage disc, and the ulna is separated by this disc.
A 3-year-old child screams in pain after being suddenly lifted by her hand while stepping off a curb. She holds her arm in slight flexion and pronation. What is this and how do you treat it?
What is Nursemaid's Elbow, aka radial head subluxation, aka annular ligament displacement? and... What is Hyper-pronation or supination of child's forearm with elbow flexion?
- axial traction on an extended, pronated forearm pulls the radial head distally, allowing the annular ligament to slip over the head of the radius.
Fill in the blank... In the lower forearm, the ulnar artery lies between the tendons of the
What is the flexor carpi ulnaris and ulnar nerve and tendons of the flexor digitorum superficialis.
- ulnar artery enters the palm of the hand anterior to the FLEXOR RETINACULUM with the ulnar nerve and ends by forming the SUPERFICIAL PALMAR ARCH.
A patient presents with a midshaft clavicle fracture. What is the structure at highest risk?
What is the subclavian artery and vein, and also the brachial plexus.
Two patients present with median nerve deficits. Patient A cannot flex their index and middle fingers when asked to actively make a fist. Patient B displays thenar eminence atrophy at rest and cannot oppose the thumb. What are these classical symptom displays of and where are their nerve injuries?
What are Hand of Benediction (proximal median nerve injury near the elbow) and Ape Hand (distal median nerve injury at the wrist/carpal tunnel).
- Hand of Benediction is an active deficit when making a fist due to loss of FDS and lateral FDP function. Ape Hand is a resting deformity with flattened thenar muscle.
A typist complaining of nocturnal hand paresthesia undergoes an anatomical evaluation of the space deep to her flexor retinaculum. What is this space?
What is the carpal tunnel?
- 9 flexor tendons (4 FDS, 4 FDP, 1 FPL)
- median nerve travels inside the carpal tunnel
- flexor retinaculum attaches laterally to the trapezium and medially to the pisiform and hook of hamate. Compression of the median nerve leads to THENAR ATROPHY
Which muscles of the forearm are specifically innervated by the AIN branch of the median nerve?
What are the flexor pollicis longus, FDP (2nd and 3rd digits), and pronator quadratus?
- Deep layer of the anterior compartment muscles.
A patient has pain in their elbow and after palpation, you determine that they have proximal displacement of the radius. They said they FOOSH the other day and that's when the pain started. You suspect they might have an injury in their
What is the Interosseous Membrane?
- IM is a strong ligament attaching the interosseous borders of the radius and ulna, uniting them. Its fibers resist proximal displacement of the radius.
The extensor expansion on the posterior surface of each finger splits into three parts near the proximal interphalangeal (PIP) joint. The central part of this expansion inserts into the base of the...
- the central split inserts into the base of the middle phalanx while the two lateral splits insert into the base of the distal phalanx.
An adult patient presents with weakness in wrist extension, but without sensory loss over the dorsal hand, following entrapment of a nerve within a muscle. What is this?
What is Supinator Syndrome (deep branch of the radial nerve / posterior interosseous nerve entrapment).
- The deep branch of the radial nerve pierces the supinator muscle; compression leads to motor weakness of extensors without superficial cutaneous sensory loss
A patient experiences severe pain upon deep palpation in the depression on the lateral side of the wrist after a fall on an outstretched hand, commonly known as the anatomical snuff box. What are the borders and floor of this space?
What is the lateral border: abductor pollicis longus and extensor pollicis brevis and medial border: extensor pollicis longus and the floor of the snuff box is: scaphoid, trapezium, and the floor is crossed by the radial artery.
- tenderness indicates a scaphoid fracture
Two patients come to your clinic. Patient A has a femoral shaft fracture and Patient B has a femoral neck fracture. What are the complications of each of these fractures?
What is: a femoral shaft fracture will imply complications with the powerful muscles of the thigh that attach to the bone and contract upon injury. And... a femoral neck fracture impedes on the blood supply to the femoral head which causes avascular necrosis.
To prevent missing a 'silent' second injury when a patient presents with an obvious fracture of a long bone, clinicians apply the 'Rule of Twos,' which requires imaging the
What is the joint above and the joint below?
- force often travels along the length of a long bone; a blow at one end can cause a dislocation or fracture at the far end, necessitated by the rule of twos to capture the entire functional unit.
For the distal radioulnar joint, pronation rotates the head of the radius in the anular ligament, and at the distal end, the radius moves...
What is, the radial head moves around the circumference of the head of the ulna?
A patient presents following a medial epicondyle fracture with weakness in thumb adduction and prominent clawing of the 4th and 5th digits. What type of injury is this?
What is an Ulnar nerve injury (causing Ulnar Claw).
- The ulnar nerve passes behind the medial epicondyle (cubital tunnel) and through the Guyon's canal. Damage denervates the adductor pollicis (THE ONLY ULNAR-INNERVATED THUMB MUSCLE) and medial lumbricals, causing 4th and 5th digit clawing.
What are the different insertion sites of the long flexor tendons in the digit?
WHat are the Flexor Digitorum Superficialis (FDS) inserting on the middle phalanx and the flexor digitorum profundus (FDP) inserting on the distal phalanx?
- FDS flexes the PIP joints and FDP passes through the split of the FDS tendon to flex the DIP joints.
A fracture that breaks below the level where the retinacular vessels enter the femoral neck is classified as a
What is extracapsular intertrochanteric fracture?
- because the vessels enter the neck above this level, a fracture lower down (extracapsualar/intertrochanteric) leaves the dominant blood supply to the head intact.
A patient suffers an intracapsular fracture of the femoral neck. Compared to an extracapsular intertrochanteric fracture, this patient at a significantly higher risk for avascular necrosis (AVN) of the femoral head because
What is the retinacular vessels of the medial circumflex femoral artery ascend the neck deep to the capsule and are torn by the displaced bone.
List all of the carpal bones and what are the specific ones we need to know and their associated injuries.
What are the scaphoid, lunate, triquetrum, pisiform, trapezius, trapezoid, capitate, and hamate?
- scaphoid is most commonly fractured and lunate is most commonly dislocated.
- guyon's canal is for the ulnar nerve and it runs between the pisiform and hamate.
A newborn delivered after a difficult breech presentation exhibits an arm held in adduction, medial rotation, and forearm pronation ("waiter's tip" position), with absent Moro reflex on the affected side.
What is Erb-Duchenne Palsy (Upper Trunk C5–C6 injury)?
- Upper trunk traction injuries paralyze abductors (axillary), lateral rotators (suprascapular), and flexors (musculocutaneous), leaving wrist/hand movements intact.
Which intrinsic hand muscle is responsible for adducting the thumb and identifies its innervation?
What is the adductor pollicis, innervated by the deep branch of the ulnar nerve?
- thenar eminence muslces: abdutor pollicis brevis, flexor pollicis brevis, oppens pollicis (innervated by the median nerve), the adductor pollicis is innervated by the ULNAR NERVE
The CRITOE acronym stands for what and why is this important?
What is: Capitellum, Radial Head, Internal epicondyle, Trochlea, Olecranon, External epicondyle? Important because in a pediatric elbow, an ossification center is a separate island of bone that appears within cartilage and the order is always constant.
To ensure collateral circulation to the digits, branches of the radial and ulnar arteries join together in the hand to form three major anastomotic arterial arches. The ulnar artery serves as the main contribution to the superficial palmar arch, while the radial artery gives off a dorsal carpal branch as the main supply to the dorsal carpal arch and continues to form the deep palmar arch. Together, these arches send digital arteries to provide every digit with exactly four arteries.
What are the Superficial Palmar Arch, Deep Palmar Arch, and Dorsal Carpal Arch?
- each digit receives 2 proper palmar digital arteries (from the superficial arch) and 2 dorsal digital arteries (from the dorsal carpal arch).
- the radial artery additionally gives rise directly to the princeps pollicis and radialis indicis arteries to supply the thumb and index finger respectively.
The bones directly participating in the articulation of the radiocarpal wrist joint are ... (4)
What are the scaphoid, triquetrum, lunate, and radius?