Anatomy - elbow and forearm Flashcards
Which direction is the distal humeral articulation angled in the axial plane?
5-7 degrees internally rotated
How much is the distal humerus rotated in the sagittal plane?
30 degrees flexed
How much varus/valgus is there at the distal humerus?
6-8 degrees valgus
What is the normal angle of the articular surface angle at the elbow?
82-84 degrees
What is the plane and flexion angle of the capitellum?
Plane: 30 degrees anteriorFlexion: 60 degrees flexed
What is the normal carrying angle in men and women?
Men: 10-15 degreesWomen: 15-20 degrees
What angles are the medial and lateral columns of the elbow at?
Medial: 45 degreesLateral: 20 degrees
What is the safe zone for radial head fixation?
90 degree arc between Lister’s tubercle & Radial styloid with the arm in neutral rotationGenerally, posterolateral forearm
Describe the bowing of the radius
Apex dorsal bow: 5 degrees (in sagittal plane)Radial bow: 10 degrees (in coronal plane)
What is the bare area of the ulna?
Non-articular portion of the ulna between the olecranon articular facet and the coronoid articular facet.Located ~2cm from triceps insertion, between the tendons of FCU/ECUImportant because you aim for there when doing olecranon osteotomies
What is the proximal ulnar dorsal angulation (PUDA)?
~5 degrees located ~50mm distal to the tip of the olecranonImportant because it is a landmark for comparing to the contralateral side in patients with comminuted or distorted anatomy
What are the components of the lateral ligamentous complex of the elbow?
Annular ligamentRadial collateral ligamentLateral ulnar collateral ligament
What are the components of the annular ligament? Its attachments?
Superior & inferior oblique bandsAnnular ligament band itself?Attachments: anterior and posterior portions of the sigmoid notch of the proximal radius
What are the attachments of the lateral radial collateral ligament?
Lateral epicondyleDistally, blends with the annular ligament above the equator of the radial head
What are the attachments of the lateral ulnar collateral ligament?
Lateral epicondyleDistally, at the supinator crest of the ulna
What are the components of the medial ligamentous complex of the elbow?
Anterior bundlePosterior bundleTransverse bundle
What are the components of the anterior bundle of the MCL of elbow?
Anterior band Posterior band Central band
What is the role of the anterior band of the anterior bundle?
It is the primary static stabilizer to valgus stress at 20-120 degrees of elbow flexion
What is the primary static stabilizer of the elbow to valgus stress from 20-120 degrees of elbow flexion?
Anterior band of the anterior bundle
What is the primary stabilizer to valgus stress at >120 degrees of elbow flexion?
Ulnohumeral articulation, specifically the intrinsic osseous restraint between the ulna and trochlea
In extension, which part of the ulnar collateral ligament is most susceptible to valgus overload?
Anterior band of the anterior bundle
In flexion, which part of the ulnar collateral ligament is most susceptible to valgus overload?
Posterior band of the anterior bundle
When is the central band tight?
It is isometric throughout the ROM
What is the role of the posterior BUNDLE (not band)?
Secondary stabilizer of the elbow at high degrees of flexion
What is the role of the transverse bundle of the ulnar collateral ligament?
Unknown - it doesn’t cross the joint (ulna-ulna)I think it’s a labrum type structure that deepens the joint
Which bundle of the ulnar collateral ligament does not play a significant role in elbow stability? Why not?
Transverse bundle of the ulnar collateral ligamentBecause it doesn’t cross the elbow joint
How does the radial head affect varus stability?
Indirectly provides varus stability by tensioning the LCL
What innervates the muscles of the deep flexor compartment of the forearm?
AIN
What is the innervation of flexor digitorum profundus?
Radial 2: AINUlnar 2: ulnar
What is the innervation of FPL?
AIN
What is the innervation of pronator quadratus?
AIN
What innervates the superficial flexor compartment of the forearm?
Median nerve
Where does ECRL insert?
2nd metacarpal
Where does ECRB insert?
3rd metacarpal (it’s shorter than ECRL)
Where does brachioradialis insert?
styloid process
What innervates ECRB?
PIN
What innervates the mobile wad, aside from ECRB?
radial nerve
What innervates ECU?
PIN
What is the Space of Parona?
Potential space in the forearm between FPL, FDP and pronator quadratus
Name the common sites of compression of the median nerve?
Ligament of StruthersLacertus fibrosis (bicipital aponeurosis)Pronator teres (between the 2 heads)Subliminus bridge (fibrotendinous arcade that marks the start of FDS)”Ladies Love Poontang Sauce”(then in the wrist - carpal tunnel)
Name the common sites of compression of the AIN?
Two heads of pronator teresFDSAberrant vesselsAccessory muscles of Ganzter (accessory FPL)
What are the common sites of compression of the radial nerve?
Fibrous bands anterior to radial headRecurrent radial vessels (Leash of Henry)ECRBArcade of Frohse (proximal edge of supinator)Supinator (distally as PIN exits) FREAS
What are the common sites of compression of the ulnar nerve?
Ligament of Struthers Arcade of StruthersHypertrophied medial tricepsMedial intermuscular septumAnconeus epitrochlearisCubital tunnel 2 heads of FCULigament of Spinner (aponeurosis between FDS of ring finger and humeral head of FCU)Deep flexor pronator aponeurosis
What are the two origins of FCU
Humeral head: common flexor originUlnar head: medial margin of olecranon
What is the Kocher interval?
The posterolateral interval: ECU and anconeus
What is the Kaplan interval?
EDC & ECRL
What is associated with distal radial shaft fractures occuring within 7.5cm of the radiocarpal joint?
Galeazzi fracture (DRUJ injury)
What is a Galeazzi fracture?
radial shaft fracture with a DRUJ injury
What is a Monteggia fracture?
Ulnar shaft fracture with a dislocated radial head
Where does the AIN originate?
4cm distal to medial Epicondyle, but generally quite variable where it branches off the median n proper
What is the column theory of the distal humerus?
3 columns make up distal humerus- Medial: diverges from humeral shaft at 45 deg angle- Lateral: diverges from humeral shaft at 20 deg angle- Distal: connect 2 columns. The “spool”. Is the articular part
What is the definition of the normal articular surface angle (on x-ray)?
Angle between long axis of humerus and articular surface. 82-84 deg - remember b/c there is 6-8deg valgus at elbow
What is the Baumann angle? What is the normal Baumann angle?
Angle between capitellar growth plate (of lateral condyle) and long axis of humerus64-81 deg Mean of 72deg
Where should the anterior humeral capitellar line intersect the capitellum?
Central 1/3
What are the landmarks of the coronoid?
6mm from capsule (proximal to capsule)12mm from brachialis (proximal to it)18mm from MCL (proximal and ulnar to it)
What attaches to the coronoid tip?
Nothing
What is the function of the lateral ligamentous complex of the elbow?
Key stabilizers against posterolateral rotatory instability (PLRI)
What is the function of the medial collateral ligament complex?
Provide valgus stability
What is the function of the anterior bundle of the MCL?
Primary static stabilizer to valgus stress from 20-120 deg of elbow flexion
What is the function of the posterior bundle of the MCL?
A secondary stabilizer in high degrees of flexion
What are the primary stabilizers of the elbow?
Ulnohumeral articulationMCLLCL
What are the secondary stabilizers of the elbow?
Radial headJoint capsuleCommon flexor and extensor origins
What is the primary stabilizer of axial forearm stability?
Intact radial head
What are secondary stabilizers of axial forearm stability?
Triangular fibrocartilage complex (TFCC)Interosseous membrane
Describe the axial force transmittance from wrist to elbowie. force distribution through radius and ulna at elbow vs. at wrist, and why
In ulnar neutral variance, radiocarpal joint absorbs 80% of axial load transmitted at wrist - Remaining 20% transmitted to ulna Interosseous membrane redistributes load so that at elbow, radiocapitellar joint sees 60% and ulnohumeral joint sees 40%
What are the components of the interosseous membrane?
5 ligaments:- Central band- Accessory band- Distal oblique bundle- Proximal oblique cord- Dorsal oblique accessory cord
What is Wartenberg’s Syndrome
AKA Cheiralgia parestheticaSuperficial radial nerve compressionPresent with pain or dysthesia on dorsal radial forearm radiating to thumb. - Tinel’s sign over superficial radial nerve is most common finding
How do you differentiate between radial tunnel syndrome, PIN syndrome and lateral epicondylitis?
Radial tunnel syndrome: presents with lateral forearm pain, 3-4cm distal to lateral epicondylePIN Syndrome: present with weakness or paralysis as chief complaintLateral epicondylitis: Focal tenderness on lateral epicondyle at insertion of ECRB
What are the borders of the cubital tunnel?
Floor:- MCL of elbow- Joint capsule- OlecranonRoof:- Arcuate ligament of osborne
What is the arcade of struthers?
Thickening of the deep investing fascia of the arm - Extends from the medial head of triceps to the intermusular septum Present in 70% of the population 1.5-2cm in width, 8-10cm proximal to the medial epicondyle.where the ulnar n crosses lateral IM septum to go from anterior to posterior compartment - potential site of compression
What is Froment’s sign? What does it indicate?
Indicates loss of ulnar nerve- Froment’s sign shows weak adductorsAsk patient to hold paper in 1st webspace (adduction of thumb). Patient will instead flex the IP joint to compensate for loss of adduction
Describe the pathogenesis of ulnar claw:
AKA Hand of benediction:- Hyperextension of MCPs & Flexion of IP joint- Due to loss of intrinsics and ulnar 2 lumbricalsCaused Low lesion of ulnar nerve causing above paralysis. MCP hyperextension: loss of intrinsics (MCP flexion)IP Flexion: Unopposed action of long extensors. Loss of lumbricals causes IP flexion
What is the ulnar paradox?
High ulnar nerve lesion causes a paradoxically more benign looking hand (although the pathology is worse)- High ulnar nerve lesion takes out FDP also, causes less of an IP flexion contracture and a less worse looking hand
What is a Martin-Gruber Anastomosis?
Median nerve/AIN anatamosis with ulnar nerve- Median innervates the intrinsic muscles of handPresent in 15-30% of population
In patient’s with a Martin-Gruber Anastomosis, what are the outcomes of high nerve lacerations of median and ulnar?
High ulnar nerve laceration - Preservation of intrinsic muscle function - Loss of FCU, FDP to the ulnar 2 fingers High median nerve laceration - Loss of intrinsic muscles usually innervated by ulnar
What is an anconeus epitrochlearis?
Anomalous muscle found in 10% of patients - Arises from medial border of olecranon & adjacent triceps - Inserts into medial epicondyle May be a muscular or fibrous structurelike a “muscular osborne’s ligament”
What is pronator syndrome?
Compression of median nerve at elbowMain dDx: CTS- Parasthesia in median nerve distributionDifferent from CTS b/c:- Aching pain over proximal volar forearm- Sensory disturbance over palmar cutaneous branch distribution (this arises 4-5cm proximal to carpal tunne)- Lack of night symptoms
What is a Gantzer’s accessory FPL muscle?
An accessory long head of FPL- May cause compression of AIN
What is AIN syndrome
Compression of AINWeakness of FPL, FDP to middle and index fingers, and PQCannot make OK sign
When can you see the “Hand of Benediction”
Low ulnar nerve palsyHigh median nerve palsy (Can only flex 2 ulnar fingers)
What are the borders of the cubital fossa? What are its contents?
Proximal: horizontal line connecting med/lat epicondylesUlnar: Lateral border of pronator teresRadial: medial border of brachioradialisContents:- Biceps brachii tendon- Brachial artery and branches- Median nerve
At the elbow, where do you find the:Brachial arteryRadial arteryUlnar artery
Brachial artery:- Deep to bicipital aponeurosis (lacertus fibrosis)Radial artery:- Over pronator teres, under brachioradialisUlnar artery:- Deep to pronator teres between FDS and FDP muscles
Where does the radial artery enter the wrist?
Between brachioradialis and FCR
Distally, what does the ulnar artery travel with?
With ulnar nerve, between FDS and FCU
Where is the medial antebrachial cutaneous nerve found?
3.5cm distal to the medial Epicondyle
Where can you find the posterior branch of the median antebrachial cutaneous nerve?
1.5cm distal to the medial Epicondyle
what are the boundaries and contents of the antecubital fossa?
superior: transepicondylar linemedial: pronator tereslateral: BRcontents: biceps tendon, brachial a, median n (lateral to medial)
what are the major superficial veins of the arm and forearm?
cephalic v (lateral)basilic v (medial)each give off branch at proximal forearm that joins together forming median interbrachial v