wrist and forearm

Question 1

Describe the articulation of the wrist joint

Answer 1

the radius has three articular surfaces at the wrist.
The radiocarpal joint, the distal radial ulnar joint and an interface with the triangular fibrocartilage complex (TFCC).

The radius is the only bone of the forearm to articulate with the carpal bones – through its articulation with scaphoid and lunate

Question 2

Discuss the stabilizing ligaments of the wrist

Answer 2

Divided into intrinsic and extrinsic ligaments. The intrinsic ligaments interconnect the individual carpal bones where as the extrinsic ligaments connect the radius. ulnar and metacapral to the carpal bones.

The major intrinsic ligaments that maintain carpal stability are the scapholunate and lunotriquetral ligaments.

The extrinsic ligaments are divided into two v shaped ligamentous bands called the proximal and distal arcades. Volar arcades are generally stronger then the dorsal ones

Question 3

Discuss the blood supply of the carpals

Answer 3

The vascular supply to the wrist is provided by the radial and ulnar arteries which join in series to create dorsal and palmar arches. Intrinsic blood supply to most of the carples arises distally and runs proximal
placing the carpel bones at risk for avascular necrosis.

This is particularly true of the scaphoid capitate and lunate bones which receive their blood supply commonly from a single distal vessel.

Question 4

Discuss radiology of the wrist

Answer 4

Radial styloid process extends beyond the end of the articular surface of the ulna by 9-12mm.

The distal articular surface of the ulna may terminate before at or distal to the radiolunate articulation as a result of rotation, flexion, extension,anatomical variation or injury.

Radial inclination normally measure 15-25 degrees. This can be used to assess degree of radial shortening seen with some fractures.

Question 5

Discuss radiology of the carpal bones

Answer 5

Normal appearance of the carpus on the PA shows an approximately equal distance between the carpal bones 1-2 mm and three smooth curves normally can be drawn along the carpal articular surfaces (gilula’s archs). width of >3mmis suggestive of dislocation

Disruption of these curves or widening of the carpal spaces is an indication of ligament disupriton, instability or fracture.

Normal volar tilit should be evident on lateral x-rays typically measuring 10-25 degrees. Pisiform should be seen between the palmar edge of the scaphoid and the palmar surface of the capitate. Should also see the normal alignement of the radius, lunate and capitate. The cup of the radius should contain the lunate which in turn should contain the capitate. The long axis of the radius, lunate, capitate and third metacarpal should appear as a straight line on the lateral view.

Scapholunate angle should be approximately 30-60 degrees.

Question 6

Discuss soft tissues signs on lateral x-ray of injury

Answer 6

It is estimated that on 90% of normal lateral wrist x-rays. The pronatnator quadratus is visible as a linear lucent fat collection. volar displacement, anterior bowing or complete loss of this lucency is known as pronator quadratus sign

Question 7

Discuss scaphoid fractures.

Answer 7

Most commonly fractured bone of the carpus. scaphoid injury are rare under the age of 15 as the scaphoid is composed entirely of cartilage at birth and remains predominantly cartilaginous until adolescent years.

Scaphoid fractures may be divided into three group

1) fracture of the tuberosity of the distal pole
2) fracture of the waist – accounting for 70-80%
3) fracture of the proximal pole

Snuff box tenderness, and tenderness with axial depression of the 1st metacarpal are all signs of a scaphoid fracture.

All patient with suspicion of scaphoid fracture regardless of x-ray finding should be placed in a splint for repeat imaging in 1-2 weeks.,

Duration of immobilization is relative to the location of the fracture but 6-12 weeks is common with more proximal fractures typically requiring longer immobilisation.

Question 8

Discuss lunate fractures

Answer 8

Fracture of the lunate are relatively uncommon usually assoicated with congenital short ulna with the usual mechanism being a FOOSH.

Pain may be elicited with palpation just distal to the depression seen at listers tubercle. Patients have pain over the dorsum of the wirst exacerbated by axial loading of the long finger metacpral.

Difficult to appreciate on x-ray if suscpected all should be immobilised due to the risk of AVN

Question 9

Discuss triquetral fractures

Answer 9

Second most common injury of the carpal bones.
Three main forms of this injury include fractures to the body and dorsal and volar avulsions.

Both body and avulsion fractures are commonly associated with perilunate and lunate dislocations.

Fracture of the triquetral bone is best seen on AP and urgent ortho involvement is needed if seen.

Should be immoblised in an ulna gutter

Question 10

Discuss pisiform fractures

Answer 10

Pisiform is unique in the carpal bones as it is the only sesamoid like bone – articulating with the triquetrium and attaching to the FCU

rare fracture occur in less then 1% of carpal injuries. Is important as forms one of the walls of the canal of guyun and ulnar artery or neuropraxia can be present with these fractures.

May occur in foosh or with direct blows to the hypothenar emminence

pain to the ulnar aspect of the wrist just distal to the volar crease

Parasthesia in the ulnar nerve region and hand clusminess can occur due to intrinsic muscle dysfunction

Difficult on x-ray. Most will heal well with immobilisation however if assoicated with neuropraxia should be referred to hands for decrompresion

Question 11

Discuss hamate fracture.

Answer 11

Rare and account for 5% of carpal fractures.
The hook of the hamulus is the most commonly fractured portion.

FOOSH or direct impact
Typically hook fractures occur in those playing club sports or work using hammers and vibration equipment.

Immoblisation unless there is signs of ulnar nerve or artery compromise

Question 12

Discuss trapezium fractures

Answer 12

Rare representing 4% of carpal fractures.
Two main region that fractures occur including the body and the trapezial ridge.
A direct blow to the adducted thumb can cause trapzial ridge fracture.
On exam patient report pain on moving the thumb and tenderness in the snuff box just distal to the scaphoid.

Immbolisation

Question 13

Discuss capitate fracture

Answer 13

Lies in the central postion of the distal carpal row and due to its protected area is very rarely fractured.

Question 14

Discuss trapezoid fractures

Answer 14

Rare and usually seen with fracture of the other carpal bones. typical mechanism is a direct blow down the long axis of the index metacarpal whcih may cause isolated fracture of the trapezoid or cause a dorsal fracture dislocation.

Immobilization.

Question 15

Discuss scapholunate dissociation

Answer 15

Mayfield classification
Stage 1: scapholunate disslocation results in characteristic widening of the scapholunate joint on the PA view.
This injury pattern may be seen endon with the cortex of the distal pole appearing as a ring shadow.
-may not be demonstrated on routine radiographs so when the clinical exam revelas tenderness a clenched fist x0ray can accentuate the widening

Usual presentaiton is after a fall with minimal swelling and pain localised over teh dorsal scapholunate region. Can be delayed if nil other associated fracutre

Radiographic findings
Scapholunate interval of >4mm on PA
-exacerbated by clenched fist view
Increased scapholunate angle on liateral view

Treatment and prognosis

• acute non displaced and chronic asymptomatic SLIL may be treated conervatitvely with NSAIDS
• Surgical repair or reconstruction of the scapholunate interossesous ligament is normally required to prevent long term complciations -namely proximal migration of the capitate between the scpahoid and lunate with a resultant degenrative disease known as SLAC wrist (scapholunate advanced collaspe)

Question 16

Discuss perilunate disolcation

Answer 16

Stage 2 of the mayfield classifcation of carpal instability

Seen best on lateral view: the lunate remains articualted to the distal radius the capitate is dorsally dislocated. The AP shows overlap of the distal and proximal carpal rows and also may show an assoicated scaphoid radial styloid or capitate fracture.

Treatment and prognosis
-Left untreated there is a high risk of median nerve palsy, pressure necrosis, compartment syndrome and long term wrist dysfunction. Should be reduced as soon as possible with prompt open reduction with ligmanetous repair is necessary

Despite treatment long term risk of degenreative arthirtis is high, dissociated and non dissocaiteve carpal instability can occur with DISI or VISI pattern

Question 17

Differentiate lunate and perilunate dislocation

Answer 17

DDX:
in a lunate dislocation, the radiolunate articulation is disrupted and the lunate is dislocated in a palmar direction
in a perilunate dislocation, the radiolunate articulation is maintained

Question 18

Discuss stage 3 mayfield carpal instability

Answer 18

Injury appears the same as stage two but includes a dislocation of the triquetrum that is seen best on the PA view

Question 19

Discuss lunate dislocation

Answer 19

Stage 4 mayfield carpal instability
Results in characteristic triangular appearance of the lunate on the PA view caused by the roation of the lunate in a volar direction.
-Dislocation is often overlooked
-increase in radiolunate space
Also viewed in the lateral where the lunate looks like q cup tipped forward and spilling its contents referred to as a spilled teacup sign

Treatment
-urgen surgical repair of disrupted liagments is required to prevent long term joint dysfunction.

Question 20

Discuss mechanisms for carpal instability and clincial features

Answer 20

Usually foosh
Tenderness to palpation is usually noted over the dorsum of the wrist with limited ROM
Perilunate and lunate disocation often have visible deformity of the wrist and two point sensation in the median nerve distrubtion is often diminished

Question 21

Discuss IX of carpal insability

Answer 21

Can be missed
X-ray features as above
MRI has relatively low sensitivity and specificity for the diagnosis of scapholunate injury
Arthroscopy is considered to have superior detection and remains the gold standard

Question 22

Describe a Colle’s Fracture

Answer 22

Transverse fracture of the distal radial metaphysis which is dorsally displaced and angulated
usually located within 2cm of the radial articular surface
Commonly associated fracture of the ulnar stylis

Many colles fractures require ED reduction for restoration of radial length correction of dorsal angulation especially when greater than 20 degrees and optimally restoration of anatomic volar tilt.

Common emergent indications for Colles fracture reduction include any neyurovascular compromise, significant deformity, soft tissue tension or tenting, significant dorsal angulation >20 degrees

Complications - most commonly seen in older patients and those with comminution displacement and inadequate fracture reduction

• Median nerve injury most common however radial and ulnar can be involved
• acute carpal tunnle syndrome

Question 23

Discuss Smiths Fracutre

Answer 23

Transver fracutre of the metaphysis of the distal radius with associated volar displacement and angulation
Usually from direct trauma or fall onto dorsum of the hand resulting in extreme palmar flexion

Much more likely to be unstable compared to Colles fracture and require operative repair and splint reduction

It also has an increased tendency to cause neurovascular compromise

Delayed tendon complications including extensor pollicis longus entrapment and rupture ahve been documented

Question 24

Describe Barton’s Fracture

Answer 24

Oblique intra-articular fracutre of the rim of the distal radius with displacement and dislocation of the carpus along with the fracture fragment.

May involve either the dorsal rim (classic) or volar rim( volar baron’s fracutre)

Rare accounting for only 1% of radius fractures. Mechanisms for these fractures is a high velocity impact across the articular surface of the radiocarpal joint with the wrist in either volar or dorsi flexion

Reduction in ED but almost always need ORIF or percutaneous pinning

Complciations include arthritis of the radiocarpal joint and delayed carpal instability

Question 25

Describe Hutchinsons fracture

Answer 25

Intra-articular fracture of the radial styoloid - caused by direct blow or fall resulting in trauam to the radial side of the wrist. Most can be successfully treated in short arm sling. - displcaed fractures however are often asscoiated with scapholunate ligmanet disruption and require ORIF As the radial styloid is the attachment site of many ligaments of the wrist accurate fracture reudction and union are crucial for wrist function

Question 26

Discuss carpal tunnel syndrome

Answer 26

The most common entrapment neuropathy it occurs at the wrist and results in compression of the median nerve. CTS is typically chronic progressive repetitive overuse syndrome The transverse carpal ligament and volar surfaces fo the carpal bones form the caparl tunnel. It is a rigid compartment that contains nine flexor tendons (flexor pollicis longus, and the profondus and superficialis) and the median nerve.

Question 27

Discuss risk factors for CTS

Answer 27

``` Obesity Female Coexisting conditions -diabetes -pregnancy -RA -Connective tissue disease Genetic predisposition -Aromatase inhibtor use ```

Question 28

Discuss clinical features of CTS

Answer 28

Gradual onset of numbness, parasehtesai and pain in the median nerve distribution These symptoms are often bilateral and worse during the night and after strenuous activiaties Typically patient report numbness and paresthesias on awakening that lessens when the hands are shaken or held in a dependent position Pain may radiate proximal to the carpals. and symtpoms may progress to include decreased grip strength hand clumsiness thenar atrophy and trophic ulceration of the fingertips. The most common provocative test supporting the diagnosis of CTS is the wrist flexion or Phalen test - the patient flex the wrist fully for 60 seconds while holding the forearms in a vertical position. It is positive if paraethesia or numbness develops Tinels sign elecits pain or paraesthesia with light tapping or percusion over the medial nerve Durkans test or the median nerve compression test consist of the application of pressure directly over the median nerve at the carpal tunnel and may have the highest sens and spec US, MR and CT have been used for diagnosis as well as nerve conduction studies

Question 29

Discuss clinical grading of CTS

Answer 29

Mild if there is numbness tignling or discomfort over the median nerve distribution but no sensory or weakness and nil sleep disurption Moderate if no motor but occasional sleep disturbance Severe if weakness in the median distribution or simptoms are disabling and prevent ADLS

Question 30

Discuss management of CTS

Answer 30

Conservative - Splinting wrist in a neutral position - administering cortisone injection in the carpal tunnel Factors that lesson the likelihood of successful nonoperative treatment include 1) age >50 2) symptom duration longer than 10 months 3) constant parethesias 4) stenosing flexor tenosynovitis 5) positive Phalens test NSAIDS show little benefit If conservative measures fail surgical decompression is the management of choice

Question 31

Discuss acute CTS

Answer 31

Occurs over hours rather than weeks months or years much less common ACTS is more often directly related to fractures fracture dislocation haemorrhaic conditions infections vascular disorders and oedema involving the wirst.

Question 32

Describe the monteggia fracture

Answer 32

Ulnar fracture associated with radial head dislocation Bado classification is used to subdivide the fracture into four types Classic mechanisms for monteggias is a FOOSH resulting in hyperpronation - direct trauma or a fall onto the flexed elbow has also been implicated in the mechanisms of the injury PIN injury is common and radial nerve should be evaluated Chronci irreducible radial head dislocation can occur as a result fo delay in diagnosis. Drawing the radiocapitellar line through the ehad of the capitellum can prevent over looking a proximal dislcoation. Mangement depends on age, paeds with this fracture and good reduction can be manged in a long arm cast in supination where as adults will almost invariably need fixation COmplciatiosn - malunion, non union, synostosis, stiffness and nerve palsy

Question 33

Describe Galeazzis fractures

Answer 33

Refers to fracture of the middle to distal third of the radius associated with injury to and dislocation of the DRUJ Fall or motor vehicle collision as patient braccess by stretching out the hand in hyperpronation AP and lateral films are needed of the entire forearm and wrist Besides the obvious fracture of the radius at the middle to distal third there will be other radiographic findings. On the AP view of the forearm the space between the distal radius and ulnar is widened >2mm and the radius appears relatively shortened. IN the altera view the dorsally angualted fracture of the radius can cause a dorsal dsiplacement of the ulna head Conservative management of Galeazzis fracture in adults has been asscoiated with poor otucomes. Due to deforming forces from different forarm muscles and loss of stability at the DRUJ displacement of the alignement in the cast occurs depite successful initial reduction Good outcome for children with conservative management

Question 34

Describe the essex-lopresti lesions

Answer 34

Triad of fracture/dislocation of radial head, interosseous memrbane violation and DRUJ instabilty

Question 35

Discuss indications for reduction of distal radius fracture in the ED

Answer 35

1) visible deformity in the wrist 2) loss of volar tilt of the distal radial articular surface beyond neutral 3) Loss of more than 5 degrees of the radial inclination of the distal radius 4) intra articular step of more than 2mm 5) radial shortening of more than 2-3 mm

Question 36

List factors associated with instability of the distal fragment and failure to maintain reduciton

Answer 36

1) presence of intra-articular component 2) shearing fractures 3) palmarly displaced fractures 4) greater magnitude of initial displacment or comminution