Hands Flashcards
What area of the finger does the extensor expansion cover?
Covers the dorsum of the proximal phalanx and sides of its base
Where does the extensor expansion insert?
Attaches by central slip into the base of the middle phalanx and two lateral slips into the base of the distal phalanx
What are the borders of Guyon’s canal?
Ulnar: Pisiform, FCU tendon, abductor digiti minimi muscle
Radial: Hook of hamate
Floor: Flexor retinaculum, pisohamate ligament, hypothenar muscles
Roof: palmar carpal ligament
What does Guyon’s canal transmit?
Ulnar nerve – bifurcates within the canal into superficial (sensory) and deep (motor) branches.
Ulnar artery – located on the radial aspect of the ulnar nerve. It gives rise to a deep palmar branch and continues radially across the palm as the superficial palmar arch.
Venae comitantes of ulnar artery
Lymphatic vessels
Name some landmarks in planning an incision for a carpal tunnel release
Intersection of Kaplan’s cardinal line and the radial border of the ring finger
Describe the pathoanatomy of a swan neck deformity
Primary lesion is lax volar plate that allows hyperextension of PIP
Secondary lesion is imbalance of forces on the PIP joint (PIP extension forces that is greater than the PIP flexion force).
Causes of this include
mallet injury
FDS rupture
Intrinsic contracture
tethering of the lateral (collateral) bands by the transverse retinacular ligament as a result of PIP hyperextension
If the lateral (collateral) bands are tethered, excursion is restricted and the extension force is not transmitted to the terminal tendon, and is instead transmitted to the PIP joint
MCP joint volar subluxation
caused by rheumatoid arthritis
Describe Doyle’s classification of Mallet finger injuries
Type I
Closed injury with or without small dorsal avulsion fracture
Type II
Open injury (laceration)
Type III
Open injury (deep soft tissue abrasion involving loss of skin and tendon substance)
Type IV
Mallet fracture
A = distal phalanx physeal injury (pediatrics)
B = fracture fragment involving 20% to 50% of articular surface (adult)
C = fracture fragment >50% of articular surface (adult)
Describe the origin and insertion of the lumbricals
Originates from the tendon of the flexor digitorum profundus. Inserts onto the radial aspect of the extensor hood of each digit.
What are the borders of the carpal tunnel?
Carpal arch:
Concave on the palmar side, forming the base and sides of the carpal tunnel.
Formed laterally by the scaphoid and trapezium tubercles
Formed medially by the hook of the hamate and the pisiform
Flexor retinaculum:
Thick connective tissue which forms the roof of the carpal tunnel.
Turns the carpal arch into the carpal tunnel by bridging the space between the medial and lateral parts of the arch.
Spans between the hook of hamate and pisiform (medially) to the scaphoid and trapezium (laterally).
What lies in the carpal tunnel?
The tendon of flexor pollicis longus
Four tendons of flexor digitorum profundus
Four tendons of flexor digitorum superficialis
Median nerve
What is Elson’s test?
Have the patient rest their hand on a table, with the PIP joint of the involved finger flexed to 90 degrees over the edge of the table.
Palpate the middle phalanx of the involved finger, then ask the patient to extend the PIP while providing some resistance.
Test is POSITIVE if the patient has a weak extension at the PIP joint with (hyper)extension at the DIP.
Test is NEGATIVE if the patient has strong extension at the PIP joint, while the DIP remains floppy.
Which zone is most commonly injured in extensor tendon injuries?
VI
Which three muscles perform deforming forces at the base of the thumb?
Abductor pollicis longus
Extensor pollicis longus
Adductor pollicis
How can you classify thumb fractures?
Extra-articular oblique
Extra-articular transverse
Intra-articular Bennett
Intra-articular Rolando
Intra-articular comminuted
What is the classic MOI for thumb fractures?
Most Bennett and Rolando are fractures caused by axial force applied to the thumb in flexion
