Elbow/Forearm Anatomy Flashcards
radial fossa
coronoid fossa
olecranon fossa
trochlea
trochlea
capitellum
at what angles do the medial and lateral columns of the elbow diverge from the humeral shaft?
medial 45°
lateral 20°
describe the humeral-ulnar joint
trochlea articulates with semilunar notch and is covered by 300° of cartilage
normal sagittal radius of the capitellum
10-12 mm
normal angles of elbow articulation
5° radial inclination
6° valgus
30° anteverted
radial tuberosity
interosseous border
ulnar notch
interosseous border
normal coronal bow of radius
10° apex lateral
normal sagittal bow of radius
only proximal, but 4.66° apex volar
where is it safe to put radial head screws?
in the 110° of arc that does not articulate in pronation and supination
you find this between lister’s tubercle and the radial styloid
radial notch
ulnar tuberosity
interosseous edge
crest for supinator
space for the meniscoids
space for the meniscoids
ulnar tuberosity
radial notch
2 alignments to check on lateral elbow
radiocapitellar
anterior humeral
*both should bisect the capitellum
what is normal proximal ulna dorsal angulation?
5.7° located 47 mm distal to tip of olecranon
normal distal humerus articular surface angle
82-84°
normal carrying angle
female 15-20°
male 10-15°
what is baumann angle?
humeral shaft and a line along the lateral condyle
normal ~72°
what are the orders and ages for ossification of the elbow?
Capitellum = 1
Radial head = 3
Internal (meaning medial epicondyle) = 5
Trochlea = 7
Olecranon = 9
External (meaning lateral epicondyle) = 11
what does the angle X show?
this is the anterior angulation of the articular surface of the distal humerus
normal is ~30° (what you called anteversion in the last card)
where is the coronoid in relation to local structures?
6 mm from joint capsule
12 mm from brachialis
18 mm from MCL
anterior capsule
radial collateral ligament
annular ligament
lateral ulnar collateral ligament
posterior capsule
transverse ligament (part of medial ulnar collateral ligament)
anterior bundle (part of medial ulnar collateral ligament)
posterior bundle (part of medial ulnar collateral ligament)
what does the annular ligament do?
attaches to the anterior and posterior margins of the sigmoid notch of the proximal ulna to hold down the radial head
where does the radial collateral ligament insert?
annular ligament!
where does the lateral ulnar collateral ligament insert?
tubercle of supinator crest
where does the anterior bundle of the medial ulnar collateral ligament insert?
sublime tubercle
the primary stabilizer to valgus stress from 20-120°
describe the anterior bundle of the MUCL
anterior (more susceptible at extension), central and posterior (more susceptible at flexion) bands
what is the role of the transverse band of the MUCL?
unknown - it doesn’t span the joint
which ligament can be released without causing instability in a stiff elbow?
the posterior bundle of MUCL
what provides valgus stability at <20° or >120° if the MUCL does the range between?
osseous interaction between the olecranon and trochlea
list 3 primary stabilizers of the elbow
ulnohumeral articulation
MUCL
LUCL
list 3 secondary stablizers of the elbow
radial head
joint capsule
common flexor and exensor origins
what is the primary stabilizer of axial stability in the forearm?
intact radial head
2 secondary stablizers of the forearm
TFCC (responsible for 8% of the forearm stiffness)
interosseous membrane
how is force transmitted through the wrist and elbow?
at the wrist the radiocarpal joint takes 80% of the brunt, however, the interosseous membrane redistributes this load so that by the elbow the split is only 60% radiocapitellar
what makes up the interosseous membrane of the forearm?
5 kinds of ligaments:
central band
accessory band
distal oblique bundle
proximal oblique cord
dorsal oblique accessory cord
anterior superficial muscles of the forearm (5)
PT
FCR
PL
FCU
FDS
anterior deep muscles of the forearm (3)
FDP
FPL
PQ
mobile wad muscles (3)
BR
ECRL
ECRB
posterior superficial muscles of the forearm (4)
anconeus
ED
EDM
ECU
posterior deep muscles of the forearm (5)
supinator
APL
EPB
EPL
EI
course of the radial artery
on pronator teres deep to brachioradialis
enters the wrist between FCR and brachioradialis
course of ulnar artery
deep to pronator teres
between FDS and FDP
enters wrist between FDS and FCU
where does the common interosseous artery come from?
a branch of the ulnar artery, gives off the:
- posterior interosseous artery which runs down the posteior compartment between superficial and deep layers
- anterior interosseous artery which runs on the volar aspect of the interosseous membrane deep to FDP with AIN
list the 4 recurrent arteries of the forearm
radial recurrent
anterior ulnar recurrent
posterior ulnar recurrent
recurrent interosseous
course of median nerve in forearm
medial to brachial artery at elbow
passes between 2 heads of pronator teres
runs between FDS and FDP
gives off AIN as it passes 2 heads of PT, then runs on the volar surface of the interosseous membrane
muscles AIN supplies
FPL
lateral half of FDP
PQ
order of supply of median nerve
PT
FCR
PL
FDS
*gives off AIN
APB
FPB
OP
lumbricals 1/2
4 sites of potential compression of the median nerve
1) supracondylar process of humerus and ligament of struthers
2) lacertus fibrosis (thick bicipital aponeurosis)
3) PT
4) sublimis bridge - the fibrotendinous arch that represents the origin of FDS
where could AIN be impinged?
PT
FDS
aberrant vessels
accessory muscles like Gantzer’s FPL
so how do you tell the difference between pronator (median nerve) and AIN syndrome?
no paresthesia in AIN syndrome
tinel at anterior elbow in pronator syndrome
pain is more proximal in pronator syndrome
exacerbated by resisted pronation (AIN should still be strong in pronation)
what is the ligament of struthers?
a vestige in ~2% of the population on the distal medil humerus that has a fibrous connection to the medial epicondyle. this can entrap the median nerve causing a palsy. you can tell the difference between this and other median nerve entrapments if there is weakness in pronation
what is the sublimis bridge?
an abberant arch of FDS that originates on the medial epicondyle and inserts proximal to pronator teres on the proximal radius which can entrap the median nerve
what is Gantzer’s accessory FPL
an extra FPL that originates on the medial epicondyle and coronoid process and can entrap the median nerve
course of the ulnar nerve
descends anterior to the medial intermuscular septum
passes posteriorly through the intermuscular septum
passes through arcade of struthers
travels posterior to medial epicondyle in cubital tunnel
passes into forearm between humeral and ulnar heads of FCU
penetrates deep flexor/pronator aponeurosis
travels with ulnar artery deep to FDS and FCU on FDP
order of supply for ulnar nerve
FCU
FDP 3/4
abductor DM
opponens DM
flexor DM
lumbricals 3/4
FPB (deep head only)
adductor P
interossei
7 potential sites of ulnar nerve compression
1) medial intermuscular septum
2) arcade of struthers
3) hypertrophied medial triceps muscle
4) cubital tunnel (arcuate ligament of osborne)
5) anconeus epitrochlearis
6) 2 heads of FCU
7) deep flexor pronator aponeurosis (>5 cm distal to medial epicondyle)
what is the arcade of struthers?
~70% of population
thickening of the deep investing fascia of distal arm from medial head of triceps to the intermuscular septum
1.5 - 2 cm width
8 cm proximal to medial epicondyle
what is the cubital tunnel?
the space through which the ulnar nerve passes at the elbow bounded by the MCL, joint capsule and olecranon and the arcuate ligament of osborne (an aponeurosis really, from the humeral and ulnar heads of the FCU
what is the anconeus epitrochlearis?
an anomalous muscle found in ~10%
arises from medial olecranon to medial epicondyle
can be muscular or fibrous
3 signs of low ulnar nerve palsy
froment (pinch paper)
clawing (lumbricals not working)
wartenberg (unopposed EDM)
what is a Martin-Gruber anastomosis?
15-32% of population
essentially, fibres normally in the ulnar nerve travel all the way to mid forearm before joining the ulnar nerve from the median nerve. usually these are the nerves for:
1st DI
adductor pollicis
abductor DM
course of the radial nerve
through triangular interval
into spiral groove between lateral head and medial head of triceps
penetrates lateral intermuscular septum 10-12 cm proximal to elbow
between brachioradialis and brachialis
bifurcates into PIN and superficial radial nerve 3-4 cm proximal to leading edge of supinator
superficial radial travels under brachioradialis then subcutaneously in distal 1/3 of forearm
PIN courses deep to supinator
order of supply radial nerve
triceps
lateral 1/3 brachialis
anconeus
brachioradialis
ECRL
*then PIN*
ECRB
supinator
ECU
ED
EDM
APL
EPL
EPB
EI
which muscle is last to regain function after a PIN palsy?
EI
5 sites of compression of PIN
1) fibrous bands of tissue anterior to radiocapitellar joint between brachialis and brachioradialis
2) Lease of Henry (recurrent radial vessels near neck of radius)
3) leading edge of ECRB
4) arcade of Frohse (the proximal edge of the superficial portion of supinator
5) distal edge of supinator muscle as PIN exits
what is the chief complaint in PIN syndrome?
motor loss of wrist and digit/thumb extension
what is the chief complaint in radial tunnel syndrome?
proximal lateral forearm pain
how do you tell the difference between lateral epicondylitis and radial tunnel syndrome?
the location of pain is on the lateral epicondyle versus 3-4 cm distal in the radial tunnel
*you can also test radial nerve stretch by extending elbow, pronating and flexing wrist
where is the SRN most vulnerable to compression?
as it exits the deep tissue at the posterior border of brachioradialis
patient presents with pain and dysesthesia on the dorsal radial forearm radiating to the thumb and index finger
this is wartenberg syndrome - entrapment of the superficial radial nerve
contents of the cubital fossa from medial to lateral
median nerve
brachial artery
biceps tendon
radial nerve/PIN
PT
brachioradialis
ECRL
anconeus
FDS
PT
brachioradialis
supinator
ECRL
anconeus
FCU
