Exam 4: Hand Worksheet Flashcards
Identify/explain the following:
Distal and proximal palmar creases
See the picture
- If there is just one crease (instead of distal and proximal) it is a sign of Down’s Syndrome.
- Usually gives us an estimation of axis of MCP (outward signs of where motions are).
- If I make a splint that is short of these creases, it allows motion.
- If I make a splint past these lines, it limits motion.
- If I make a terrible splint at these lines, it creates skin breakdown and pain.
What attaches skin to bone in the hand?
Cleland and Grayson ligaments
Identify/explain the following:
Thenar crease
where skin is moving for opposition movement (see picture)
- Same significance of hand creases
- If we want to allow opposition, we need to allow room for the size of the thenar eminence and the crease.
- If we want to prevent opposition, we need to go way past the crease.
Identify/explain the following:
Surgical no-man’s land
Portion of the hand where surgery is generally a disaster!
Dr. Bringmand said “Below proximal crease, above distal crease.” (I believe) But this dosen’t make sense.
I think we previously learned it was the distal palmar crease to the crease that goes with the PIP joint (middle finger crease?). Still confused on this one.
Zone II in the picture
Identify/explain the following:
Proximal and distal thumb creases
Finger creases (distal, middle, proximal)
Basicically important for the same reasons as the other creases:
- Must stop short or go well past (just like the other creases). DO NOT STOP RIGHT AT THE CREASE!
(we didn’t discuss thumb creases in class specifically, but this is what he said about finger creases)
Identify/explain the following:
- Wrist Creases
Same principles of the importance of going beyond crease to prevent movement, stopping well short of crease to allow motion, do not stop on crease or it will hurt and cause break down
- Special consideration for wrist is that there is a lot more force involved at the wrist. Make sure splint goes high enough on the forearm to prevent movement
Where do finger flexors form a single sheath?
From Wikipedia:
The common synovial sheath for the flexor tendons or the ulnar bursa[1] is a synovial sheath in the carpal tunnel of the human hand.
It contains tendons of the flexor digitorum superficialis and the flexor digitorum profundus, but not the flexor pollicis longus.[2]
The sheath which surrounds the flexores digitorum extends downward about halfway along the metacarpal bones, where it ends in blind diverticula around the tendons to the index, middle, and ring fingers. It is prolonged on the tendons to the little finger
Identify/explain the following:
- Thenar eminence
- Hypothenar eminence
Find the proximal, distal, and longitudinal arches of the hand (pg 396).
What supports them?
Why are they important?
- Three Arches
- Proximal transverse arch,
- Fixed arch
- made from distal row of carpal bones and taut volar carpal ligament
- Part of the carpal tunnel
- Provides mechanical advantage to the flexors, maximizing grasp function
- distal transverse arch;
- mobile arch
- because of mobile ulnar fourth and fifth CMC joints and highly mobilie thumb CMC.
- located at the level of the metacarpal heads
- allows for optimal grasping abilities
- mobile arch
- longitudinal arch
- spans the length from the metacarpal to the distal phalanx
- disruption of this arch occurs in pts who have sustained an ulnar nerve injury with resulting loss of intrinsic muscle function
- Proximal transverse arch,
- All the arches Allow spherical grasp and normal functioning of the hand
What is okay to use when rehabing spherical grasp?
what is not okay?
- Use a squishy ball (NOT A TENNIS BALL, because it splays the hand)
- Use putty
- The individual digit hand squeezer thing is great (gripmaster) (pictured)
Explain the stiffness/mobility of metacarpals
Remember Stiffness of metacarpals (metacarpals for first finger and second finger stiffest; metacarpals for ring and baby finger very mobile. If this mobility is lost, hand will be stiff and you will not be able to use spherical grasp, so we must rehab it).
Contrast skin on the palmar (volar) side of the hand to skin on the dorsal side of the hand.
Palmar skin is very thick (working side of our hand)
- Protection
- Grip
- Doesn’t move much. Fixed.
- More susceptible to contracture after injury, causes excessive flexion
Dorsal skin
- Thin
- Loose
- Allows motion
- Injury to dorsal skin, can cause contractures too limiting flexion
What are Cleland and Grason Ligaments?
They attach skin to bone
Name the proximal carpal bones (and palpate them)
- scaphoid (navicular)
- lunate,
- triquetrium
- pisiform
Name the distal carpal bones (and palpate them)
- trapezium
- trapezoid
- capitate
- hamate
What is the pneumonic that will help with remembering the carpal bones?
(and how do you use it?)
- Some (scaphoid)
- Lovers (Lunate)
- Try (Triquitrum)
- Positions (Pisiform)
- That (Trapezium)
- They (Trapezoid)
- Can’t (Capitate)
- Handle (Hamate)
Look at palmar side of hand. Start next to the thumb on the proximal row of carpals and and go across towards pinky finger as you name them.
After P, go back next to thumb, this time start at the distal row and go across again towards pinky finger as you name them.
What is the closest metacarpal to the capitate?
The third metacarpal
What bones form the CMC of the thumb?
Is there another common name for that joint?
Trapezium and first Metatarsal
trapeziometacarpal joint (TMC)
(It is unique because it is a saddle joint)
What defines the anatomic snuffbox? (upper and lower borders and floor)
Ulnar (medial) border: Tendon of the extensor pollicis longus.
Radial (lateral) border: Tendons of the abductor pollicis longus and extensor pollicis brevis. (the APL is the most radial, the EPB is longer and
Proximal border: Styloid process of the radius.
Floor: Carpal bones; scaphoid and trapezium.
Roof: Skin
What other structures can be found in the anatomical snuff box (besides the upper and lower borders and floor)?
- Cephalic Vein
- Radial Artery
- Superficial Radial Nerve
Where is the ulnar syloid?
Styloid process of ulna
where is the radial syloid?
styloid process of radius
Where is lister’s tubercle?
What does it do?
at wrist, Lister’s tubercle is palpable on dorsum of radius;
- it serves as a pulley for the EPL;
Where is the tunnel of Guyon?
What is its significance (what does it contain)?
- depression between pisiform & hook of hamate is converted into fibrosseous tunnel, the tunnel of Guyon, by pisohamate ligament;
- the ulnar nerve bifurcates within the canal into superficial and deep branches
- deep branch of the ulnar nerve (more radial) and superficial branch more ulnar
- depression between pisiform & hook of hamate is converted into fibrosseous tunnel, the tunnel of Guyon, by pisohamate ligament;
- tunnel of Guyon is clinically significant because it contains ulnar nerve and artery & is site for compression injury;
- ulnar artery is immediately adjacent and radial to the ulnar nerve;
- tunnel of Guyon is clinically significant because it contains ulnar nerve and artery & is site for compression injury;
More detail from Orthobulltes.com:
Guyon’s Canal, formed by
- roof - superficial palmar carpal ligament
- floor - deep flexor retinaculum, hypothenar muscles
- ulnar border - pisiform and pisohamate ligament
- radial border - hook of hamate
How do you find/palpate the hook of the hamate?
Put DIP of one thumb on the pisiform of the other hand, then lay the thumb down on palm in the direction of the index finger. The hook of the hamate should be palpable close to the tip of the thumb in this position.
Carpal tunnel: Location and significance (what is in it?)
Bordered by flexor retinaculum and carpal bones (trapezium, Trapezoid, Capitate, and Hamate)
Contains the median nerve and 9 flexor tendons (the tendons of the Flexor digitorum profundus [4 deepest], Flexor digitorum superficialis [two sets of two more superficial], and FPL tendon)
Can get carpal tunnel syndrome from pinching the median nerve in the carpal tunnel.
**Ulnar nerve, ulnar artery, and palmaris longus tendon run outside of carpal tunnel on palmar side.
**radial artery runs outside of carpal tunnel on dorsum of hand
**The flexor retinaculum is attached radially to the scaphoid tubercle and the ridge of trapezium, and on the ulna side to the pisiform and hook of hamate
What is the difference in function of the 2nd and 3rd metacarpals as opposed to the 4th and 5th?
2nd and 3rth mtacarpals are more stable
4th and 5th metacarpals are more flexible
This allows spherical grasp and stability in the hand
What is the most commonly fractured carpal bone?
Scaphoid
What tendon inserts on the base of the 3rd metacarpal?
I have come up with two answers:
- Tendon of Adductor Pollicis (Oblique Head)
- Tendon of Extensor Carpi Radialis Brevis
It makes more sense to me that we should remember the Adductor Pollicis Oblque head, since the thumb is a major consideration for creating hand splints.
I emailed Dr. Bringman. Here is what he said:
“You are correct [about thinking the Adductor Pollicis Oblique Head was more important for us to remember]. Extensor carpi radialis brevis is also a prime extensor of the wrist and should be given due credit as well. As this muscle extends it also passive creates finger flexion and is of the utmost importance for individuals that would be using a tenodesis grip.”
I would remember both
How do you perform Finkelstein’s test?
what is it for?
used to diagnose De Quervain’s tenosynovitis
Perform Tinel’s Sign
What does it test?
Tinel’s sign is a way to detect irritated nerves. It is performed by lightly tapping (percussing) over the nerve to elicit a sensation of tingling or “pins and needles” in the distribution of the nerve
For example, in carpal tunnel syndrome where the median nerve is compressed at the wrist, Tinel’s sign is often “positive” causing tingling in the thumb, index, middle finger and the radial half of the fourth digit. (most associated with carpal tunnel syndrome, but can be used to test other nerves)
Perform Phalen’s test
What does it test?
Phalen’s test is a provocative test used in the diagnosis of carpal tunnel syndrome
Press dorsum of hands together (reverse prayer position) and maximally flex wrists for at least 1 minute. Positive is reproduction of symptoms (pain, tingling, etc in the median nerve distribution)
Define Dupuytren’s contracture
a condition in which there is fixed forward curvature of one or more fingers, caused by the development of a fibrous connection between the finger tendons and the skin of the palm.
Define Trigger finger
Trigger finger, also known as stenosing tenosynovitis (stuh-NO-sing ten-o-sin-o-VIE-tis), is a condition in which one of your fingers gets stuck in a bent position. Your finger may straighten with a snap — like a trigger being pulled and released.
Trigger finger occurs when inflammation narrows the space within the sheath that surrounds the tendon in the affected finger. If trigger finger is severe, your finger may become locked in a bent position.
More:
Stenosing tenosynovitis is a condition commonly known as “trigger finger.” It is sometimes also called “trigger thumb.” The tendons that bend the fingers glide easily with the help of pulleys. These pulleys hold the tendons close to the bone. This is similar to how a line is held on a fishing rod (Figure 1). Trigger finger occurs when the pulley becomes too thick, so the tendon cannot glide easily through it (Figure 2).
Purpose of palmar intrinsics (I assume he means palmar interosseous muscles)
The palmar interosseous muscles adduct the fingers towards the middle finger.
Purpose of the dorsal intrinsics (I assume he meant dorsal interosseous muscles)
the dorsal interossei abduct the fingers away from the middle finger.
Purpose of the lumbricals
The lumbricals are intrinsic muscles of the hand that flex the metacarpophalangeal joints and extend the interphalangeal joints.[1]
Swan neck deformity
(PIP joint is hyperextended, DIP is hyperflexed); caused by slippage of the flexors to dorsal side the joint line in PIP
Boutonniere deformity:
PIP is hyperflexed, DIP is hyperextended; caused by slippage of extensors to palmar side of PIP)
Mallet finger
Extensor detaches from distal phalange: forceful flexion of a fully extended finger.
Jersey Finger:
rupture flexor tendon Flexor profundus: Grabs jersey, strong extension and it pops off. Only distal phalange cannot flex. Surgery has a very very poor success rate. Better outcomes if surgery is done early.
Colles fracture
FOOSH onto wrist hyperextension extension with pronated forearm, Distal radius fractures and displaces dorsally. Typically occurs to elderly population
Smith fracture:
Reverse of Colles fracture. FOOSH. Direct blow to dorsum of hand (wrist hyperflexes, and is supinated. Typically from a backwards fall. Typically occur in elderly individuals. Volar displacement.
Scaphoid fracture
Could be FOOSH. Avascular necrosis is a risk.
Kienbock’s Disease
AVN (avascular necrosis) of lunate, Nice thing about bone is it will hang out for a while even if it doesn’t have vascularity. Will eventually break down and hand function will slowly diminish because of displacement of ray and carpals
Bennett’s fracture:
Base of the first metacarpal bone (CMC). Thumb is extended and axial force on thumb causes fracture at CMC joint. Pop someone in helmet, or shoulder pad. Horrible place to have a fracture. Thumb will be going to be out of sync for a while.
Boxer’s fracture:
More common than Bennett’s fracture. Drunk friend punches wall (and hits stud). Breaks head of the metacarpal (most commonly fourth or fifth)
Gamekeeper’s thumb:
pops thumb UCL. Repetative stress. Or skiing. Also called Skier’s thumb. Causes instability and decreased ability to hold on to things.
What are two main categories of grips?
Precision grip
Power grip
Details about precision grip (5)
- fine motor,
- strength mostly from intrinsic muscles,
- performed in functional wrist position,
- a little ulnar drift at wrist
- requires thumb)
Details about Power Grip (3)
- hand is in neutral so we can
- use extrinsic muscles
- doesn’t always require thumb
Four types of Precision grips
- Tip to tip
- Pulp to pulp
- Key (pulp to hand)
- Pencil grip, three fingered pinch, chuck, digital prehension (chuck is a painter)
alternate name for key grip
pulp to hand
alternate names for pencil grip
- Pencil grip,
- three fingered pinch,
- chuck, (remember chuck is a painter)
- digital prehension
Four types of Power Grip
- Hook (does not require thumb)
- Cylinder, Darth Vader choke (need a thumb)
- Spherical (door knob)
- Fist grip, hammer, pistol grip
two alternate names for fist grip
- hammer,
- pistol grip
Motor Distribution of the radial Nerve
Basic:
Motor: Innervates the triceps brachii, responsible for extension at the elbow. Innervates the majority of the extensor muscles in the forearm, responsible for extension of wrist and fingers and supination of the forearm
More Detail:
The radial nerve innervates muscles located in the arm and forearm.
In the arm, it directly innervates the three heads of the triceps brachii. This muscle performs extension at the elbow. In the forearm, the deep branch of the radial nerve innervates the muscles in the posterior compartment of the forearm. These muscles generally extend at the wrist and finger joints.
Sensory Distribution of the Radial Nerve
Basic;
Sensory: Innervates most of the skin of the posterior side of forearm, and the dorsal surface of the lateral side of the palm, and lateral three and a half digits.
Nerve roots: C5-T1.
Detailed:
Sensory Functions
There are four branches of the radial nerve that provide cutaneous innervation to the skin of the upper limb:
- Lower lateral cutaneous nerve of arm – Innervates the lateral aspect of the upper arm, below the deltoid muscle.
- Posterior cutaneous nerve of arm – Innervates the posterior surface of the upper arm.
- Posterior cutaneous nerve of forearm – Innervates a strip of skin down the middle of the posterior forearm.
- Superficial branch of the radial nerve – Innervates the dorsal surface of the lateral three and half digits, and their associated palm area.
Motor distribution of midian nerve
Basic:
Motor functions: Innervates the flexor muscles in the anterior compartment of the forearm (except the flexor carpi ulnaris and part of the flexor digitorum profundus, innervated by the ulnar nerve). Also supplies innervation to the thenar muscles and lateral two lumbricals in the hand.
Detailed:
The median nerve innervates the majority of the muscles in the anterior forearm, and some intrinsic hand muscles.
The Anterior Forearm
In the forearm, the median nerve directly innervates muscles in the superficial and intermediate layers:
- Superficial layer: Pronator teres, flexor carpi radialis and palmaris longus.
- Intermediate layer: Flexor digitorm superficialis.
The median nerve also gives rise to the anterior interosseous nerve, which supplies the deep flexors:
- Deep layer: Flexor pollicis longus, pronator quadratus, and the lateral half of the flexor digitorum profundus (the medial half of the muscle is innervated by the ulnar nerve).
In general these muscles perform pronation of the forearm, flexion of the wrist and flexion of the digits of the hand.
Sensory distribution of median nerve
Basic:
Sensory functions: Gives rise to the palmar cutaneous branch, which innervates the lateral part of the palm, and the digital cutaneous branch, which innervates the lateral three and a half fingers on the anterior (palmar) surface of the hand.
Nerve roots: C5 – T1.
Detailed:
The median nerve is responsible for the cutaneous innervation of part of the hand. This is achieved via two branches:
- Palmar cutaneous branch – Arises in the forearm and travels into the hand. It innervates the lateral aspect of the palm. This nerve does not pass through the carpal tunnel, and is spared in carpal tunnel syndrome.
- Palmar digital cutaneous branch – Arises in the hand. Innervates the palmar surface and fingertips of the lateral three and half digits.
Motor Distribution of the Ulnar Nerve
Basic:
Motor functions: Innervates the muscles of the hand (apart from the thenar muscles and two lateral lumbricals), flexor carpi ulnaris and medial half of flexor digitorum profundus.
Detailed:
The ulnar nerve innervates muscles in the anterior compartment of the forearm, and in the hand.
The Anterior Forearm
In the anterior forearm, the muscular branch of the ulnar nerve supplies two muscles:
- Flexor carpi ulnaris – Flexes and adducts the hand at the wrist.
- Flexor digitorum profundus (medial half ) – Flexes the fingers.
The remaining muscles in the anterior forearm are innervated by the median nerve.
The Hand
The majority of the intrinsic hand muscles are innervated by the deep branch of the ulnar nerve.
The hypothenar muscles (a group of muscles associated with the little finger) are innervated by the ulnar nerve. It also innervates some other muscles of the hand:
- Medial two lumbricals
- Adductor pollicis
- Interossei of the hand
The other muscles in the hand (such as the thenar eminence) are innervated by the median nerve.
Sensory Distribution of Ulnar nerve
Basic:
Sensory functions: Innervates the anterior and posterior surfaces of the medial one and half fingers, and the associated palm area.
Spinal roots: C8-T1.
Detailed:
There are three branches of the ulnar nerve that are responsible for its cutaneous innervation.
Two of these branches arise in the forearm, and travel into the hand:
- Palmar cutaneous branch: Innervates the skin of the medial half of the palm.
- Dorsal cutaneous branch: Innervates the skin of the medial one and a half fingers, and the associated palm area.
The last branch arises in the hand itself:
- Superficial branch – Innervates the palmar surface of the medial one and a half fingers.
Name the Three Grades of Nerve Injury
Grade 1: Neuropraxia
Grade 2: Axonotmesis
Grade 3: Neurotmesis
Grade One Nerve Injury: Neuropraxia
- What characterizes it?
- What could cause it?
- Recovery time
- Anyting else?
- Grade One: Neuropraxia,
- Slight myelin disruption
- Crush injury
- Recovery 0 days -3 months
- How do I know it will get better in 3 months? (do nerve conduction velocity exam). Great diagnostic tool.
- PTs can do this (if they get certified)!!
- Expect pt to still have some ability
- Saturday night palsy falls under this
- Football player who hangs on crutches (brachial plexus injury)
Grade Two Nerve Injury: Axonotmesis
- What characterizes it?
- What could cause it?
- Recovery time
- Anyting else?
- Grade Two: Axonotmesis
- Axon damage
- Neural sheath is still intact
- Important because it guides regrowth (will not be lost wandering)
- Recovery 3-6 months
- Waiting on nerve to re-grow. Can grow at 1 mm/day
- We worry about atrophy, but don’t wear out stuff that is super weak (something below 3/5). Can do a bit more if there is no other neuro issues going on, but go easy on 1-2/5
- Contractures, ROM issues
- Work all the stuff around it and above it to preserve function
- NMES could help, but make sure they have sensation
Grade Three Nerve Injury: Neurotmesis
- What characterizes it?
- What could cause it?
- Recovery time
- Anyting else?
- Grade Three: Neurotmesis
- Cut, Avulsion
- Fracture (especially worried if it was an open fracture)
- Crush injury
- Stab/gunshot
- Recovery time
- 6 months – 18 months – to never
- will continue to grow, but can get lost now because there is no neural sheath
- Could get axonal sprouting (but he said this doesn’t matter that much)
- Current research: making neural sheaths with 3D printing.
- 6 months – 18 months – to never
- Cut, Avulsion
Carpal Tunnel Syndrome: what nerves, what muscles may become weak/flacid?
Compression of median nerve occurs beneath the transverse carpal ligament.
The carpal tunnel is a fibro-osseous tunnel formed by the tubercles of the scaphoid and trapezium laterally, the pisiform and hook of the hamate medially, the carpal bones dorsally, and the flexor retinaculum volarly (Fig. A6-16).
The median nerve supplies the thenar muscles (abductor pollicis brevis, opponens pollicis, and superficial part of flexor pollicis brevis) and the first and second lumbricals in the hand. Sensory branches supply the palmar surface of the lateral three and one-half fingers.
- Clinical findings:*
- Burning wrist pain and paresthesia in thumb, index, middle, and radial aspect of fourth finger that is worse at night and with wrist flexion or extension or during strenuous gripping
- Weakness of thenar muscles, clumsiness in hand
Gyan’s canal Syndrome: what nerves, what muscles may become weak/flacid?
Also commonly referred to as Ulnar Tunnel Syndrome, it is caused by compression of the ulnar nerve at the ulnar tunnel.
· Clinical findings:
- Depending on location of impingement, findings vary from sensory deficit in the ulnar distribution only, motor deficit of ulnar intrinsic hand muscles only, or both.
- Generally, there is decreased strength during pinching and gripping, and abduction deformity of the small finger (Wartenberg’s sign).
More on Gyan’s Canal Syndrome:
The ulnar tunnel is a triangular fibro-osseous tunnel formed by the pisiform and pisohamate ligament medially, the hook of the hamate laterally and distally, the superficial transverse carpal ligament volarly, and the deep transverse carpal ligament (or flexor retinaculum) dorsally (Fig. A6-19).
The ulnar nerve passes through the ulnar tunnel along with the ulnar artery. Proximal to the tunnel, the ulnar nerve gives off the dorsal branch, which runs superficial to the ulnar tunnel and provides sensation to the ulnar side of the dorsal hand.
Due to its superficial course to the ulnar tunnel, compression neuropathy at the ulnar tunnel spares the dorsal branch and spares sensation of the dorsal ulnar hand. This distinguishes ulnar tunnel neuropathy from ulnar nerve entrapment at the elbow.
Within the ulnar tunnel, the ulnar nerve divides into the superficial sensory and deep motor branches. The deep motor branch makes a sharp turn laterally at the hook of the hamate and passes under a fibrotendinous arch (pisohamate hiatus), where it is most vulnerable for compression.
The superficial sensory branch supplies sensation to the fifth and ulnar half of the fourth finger. The deep motor branch supplies the hypothenar muscles (abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi), adductor pollicis, third and fourth lumbricals, and all interosseus muscles in the hand.
Superficial Radial Nerve Syndrome: what nerves, what muscles may become weak/flacid?
Also known as Wartenberg’s syndrome, cheiralgia paresthetica, handcuff neuropathy, or watch-strap nerve compression, it is caused by entrapment of the sensory branch of the radial nerve.
· Clinical findings:
- Paresthesia in the distribution of the superficial radial nerve
More Information:
· Only the superficial branch of the radial nerve reaches the hand.
· The superficial branch originates from the radial nerve at the level of the lateral epicondyle and runs dorsal to the wrist in a superficial subcutaneous location (see Fig. A6-14). It supplies the radial side of the dorsal hand from the wrist to the proximal interphalangeal joint, the web space between the thumb and index, and extrinsic hand muscles. The intrinsic muscles are not innervated by this nerve.
· A lesion of the superficial radial nerve at the wrist results in loss of sensation of the radial side of the dorsal hand.
What are 4 functions of the hand?
- Reach
- Prehension (grip)
- Carry
- Release
Draw the sensory areas of the radial, ulnar, and median nerves on your hand.
What are four nerve entrapments that can happen in the forearm or elbow?
(we are at risk of causing these with our splint)
- Pronator Syndrome
- Anterior Interosseous Nerve Syndrome
- Cubital Tunnel Syndrome
- Posterior Interosseous Nerve Syndrome
Pronator Syndrome
· Compression of the median nerve occurs at the level of the pronator teres muscle.
· Potential sites of entrapment include the space between the superficial (humeral) and deep (ulnar) heads of the pronator teres muscle, at the origin of the flexor digitorum superficialis muscle where a fibrous arch exists, at the lacertus fibrosus, also known as bicipital aponeurosis, and, less commonly, at the supracondylar process of the distal anteromedial humerus (avian spur) (Figs. A6-7 and A6-8).
- Clinical findings:*
- Chronic forearm pain and paresthesias in the radial three and one-half digits
- No muscle weakness
- Pain on palpation of the pronator teres muscle
Anterior Interosseous Nerve Syndrome
· Also known as Kiloh-Nevis syndrome, it is caused by compression of the anterior interosseous nerve in the proximal forearm (Fig. A6-10).
· The anterior interosseous nerve is a motor branch that innervates the deep ventral muscles of the forearm, including the radial half of the flexor digitorum profundus, flexor pollicis longus, and pronator quadratus muscles.
Causes included cast pressure
· Clinical findings:
- Dull pain in volar aspect of forearm with acute onset of weakness of the thumb and index finger and weakness of the pinch mechanism.
- Inability to form an “O” with thumb and index finger (circle sign) owing to lack of innervation of flexor pollicis longus and flexor digitorum profundus muscle. Pronator quadratus also affected.
- No sensory deficit because this is a purely motor nerve. This helps to distinguish it from pronator and carpel tunnel syndromes.
Cubital Tunnel Syndrome
· Compression of the ulnar nerve occurs within the cubital tunnel at the elbow.
· The cubital tunnel is formed by the medial epicondyle anteriorly, the medial edge of the trochlea, olecranon, and ulnar collateral ligament laterally, and the cubital tunnel retinaculum (also known as the arcuate ligament or Osborne band) posteriorly as the roof (Fig. A6-11).
· The ulnar nerve innervates the skin and muscles of the ulnar side of the forearm and hand, including the flexor carpi ulnaris and ulnar half of the flexor digitorum profundus muscles.
- Clinical findings:*
- Pain and paresthesias along ulnar side of elbow, hand, and fourth and fifth fingers that are worse with elbow flexion
- Weakness in pinching of thumb and forefinger
Posterior Interosseous Nerve Syndrome
Also called radial tunnel syndrome or supinator syndrome, this is caused by compression of the posterior interosseous branch of the radial nerve within the radial tunnel (Fig. A6-14).
· The radial tunnel is formed by the capitellum posteriorly, the brachioradialis and the extensor carpi radialis longus and brevis muscles anterolaterally, and the brachialis muscle and biceps tendon medially.
· The posterior interosseous nerve supplies the supinator and extensor muscles of the forearm, including the extensor carpi ulnaris, extensor digitorum, extensor digiti minimi, extensor indicis, extensor pollicis longus and brevis muscles, and abductor pollicis longus.
· Clinical findings:
- Nonspecific forearm pain and tenderness in nerve at level of supinator muscle
- Weakness of extensor muscles with impaired ability to extend fingers and radial deviation of hand during wrist extension secondary to weakness of extensor carpi ulnaris
Pronator Syndrome: Etiology
· Etiology:
- Elbow trauma, repetitive elbow flexion, supination and pronation of forearm, or, less commonly, anatomic variants (e.g., accessory bicipital aponeurosis, accessory head of the flexor pollicis longus muscle, palmaris profundus), bicipital bursitis, and soft tissue masses
- Closed reduction of elbow dislocation can also result in intra-articular entrapment of the median nerve.
Anterior Interosseous Nerve Syndrome: Eitiology
· Etiology:
- Trauma, cast pressure
- Bulky tendinous origin of the ulnar head of the pronator teres
- Soft tissue masses such as lipoma or ganglion
- Anomalous or accessory muscles and vessels
- Fibrous bands (e.g., from superficial flexor)
Cubital Tunnel Syndrome: Etiology
- “Sleep palsy”—prolonged elbow flexion, which decreases volume of cubital tunnel, during sleep, resulting in severe symptoms
- External compression with pressure from the operating table during surgery, during unconsciousness, in wheelchair-bound patients, and in drivers who lean their elbows against hard surfaces
- Trauma (e.g., humeral fractures with loose bodies or callus formation, hematoma, elbow dislocation, avulsed medial epiphyses)
- Thickened cubital tunnel retinaculum (Osborne’s ligament)
- Anomalous muscles such as anconeus epitrochlearis
- Tumors including ganglions, lipoma, osteophytes, and osteochondroma
Posterior Interosseous Nerve Syndrome: Etiology
· Radial Nerve
- Etiology:*
- Most commonly by arcade of Fröhse (proximal edge of superficial head of supinator muscle)
- At site of exit from supinator muscle
- Abnormal recurrent blood vessels that cross the posterior interosseous nerve (leash of Henry)
- Intermuscular septum between the extensor carpi ulnaris and extensor digitorum minimi
- External compression (e.g., from crutches)
- Radial head fracture and callus formation, hematoma
- Soft tissue tumors (e.g., ganglion, lipoma)
