Hand Flashcards
What is the volar plate?
Fibrocartilagenious struture that overlies the volar aspect of the IP joints
Tough and thick, main purpose us to prevent hyperextension
What is cascade sign? Why does this work anatomically?
With arm flexed, palm supinated, partially closure of the hand should demonstrate gradual increase in flexion from radial to ulnar
If askew demonstrated injury with rotational deformity in digits
remember - the strongest movements you do with your hands involve grip and we want them to be the most stable. So when your fingers are extension the collateral ligaments are loose and you have more ROM. When you flex from 0 to 90 they go tight and less ROM.
This is why we splint with 90 flexion - otherwise when loose they contract
Which carpals are more fixed and why?
D1-D3 are more fixed. D4 and D5 have up to 25 degrees of movement (allows the hand to bend in and improve grip and better opposition of thumb)
What are the four arches in the hand?
Proximal, distal , longitudenal and transverse
What is the froment paper sign?
Why is this an important test to know?
It is a way to test for an ulnar nerve palsy
The ulnar nerve innervates the adductor pollicus
Test it by asking a patient to hold a piece of paper between their thumb and their index finger. If they can not hold it OR compensate by flexing the IP) it is positive
(remember flexor pollicus longus is a LOAF muscle innervated by median)
It is important because ulnar nerve innervating D4 and D5 is largely responsible for grip power
What are the extensor components on the dorsal surface of the hand
On the back of the hand you have the lateral bands which go from your distal phalax down to MCP and the central slip with goes in between these from the Middle phalax to the dista phalanx
Why do we have lateral bands a a central slip?
Allows for coordinated extension of fingers for fine motor tasks
What is a bountinerre deformity?
When you have a central slip injury. When you extend dip, the lumbricals pulls causing PIP pops through the defect. The trinagular ligament that holds lateral bands tight loosens overtime allowing for lateral band volar subluxation
Why do we do modified Elison test? (modified is two hands)
To look for a central slip rupture BEFORE the boutinerre deformity is apparant
Have the patient flex the PIP at 90 degrees over the edge of a table. If they can extend the PIP, central slip is fine
If they cant extend the PIP but the DIP extends, the lateral bands are compensating and the central slip is broken
Important pearl for extension joint injuries?
Only joint that is affected should be splinted, others should be free
What are the boarders of the anatomical snuffbox?
Abductor pollicus longus
EPB
EPL
Bervis sandwhich
What is special about the FDP?
Flexes the DIP
D2 and D3 are median (AIN specifically)
D4 and D5 are ulnar
Why AIN is a branch of the median nerve/ why the okay sign tests the median nerve
What is the PIN then?
Branch of the radial nerve that supplies the APL and EPB in the anatomical snuffbox
What nerves supply the intrinsic muscles of the hand? what are the exception?
Ulnar, except for LOAF
What are the two types of muscles that affect the hand?
Intrinsic - origins within the hand
Extrinsic - origins proximal to the hand (forearm) and just insert in the hand
What are two compartments in forearm?
Flexors and pronators - volar
Extensors and supinators - dorsal
Why do you get flexor tenosynovitis but not extensor? What other system is unique to the flexor side of the hand?
Flexors tendons have a synovial sheath that is avascular and prone to infection
You also have a pulley system that lives over the synovial part and prevents bowstringing of tendons forward
Which pulleys are the most important?
A2 (over proximal phalanx) and A4 (over middle phalanx)
Four is farther away
How do you test FDP and FDS?
FDS - flex your PIP
FDP - flex your DIP
(everything else should be held in extension)
Outline the blood supply to the hand
radial side comes in through anatomic snuffbox goes into deep and supeficial arch
Deep arch loops around the back, superficial stays on top and supplies palmar digital arteries
Where is the neurovascular bundle in the fingers?
Edge of flexor crease making its way up the finger