wrist and forearm Flashcards
Describe the articulation of the wrist joint
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
Discuss the stabilizing ligaments of the wrist
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
Discuss the blood supply of the carpals
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.
Discuss radiology of the wrist
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.
Discuss radiology of the carpal bones
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.
Discuss soft tissues signs on lateral x-ray of injury
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
Discuss scaphoid fractures.
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.
Discuss lunate fractures
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
Discuss triquetral fractures
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
Discuss pisiform fractures
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
Discuss hamate fracture.
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
Discuss trapezium fractures
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
Discuss capitate fracture
Lies in the central postion of the distal carpal row and due to its protected area is very rarely fractured.
Discuss trapezoid fractures
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.
Discuss scapholunate dissociation
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)
Discuss perilunate disolcation
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
Differentiate lunate and perilunate dislocation
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
Discuss stage 3 mayfield carpal instability
Injury appears the same as stage two but includes a dislocation of the triquetrum that is seen best on the PA view
Discuss lunate dislocation
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.
Discuss mechanisms for carpal instability and clincial features
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
Discuss IX of carpal insability
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
Describe a Colle’s Fracture
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
Discuss Smiths Fracutre
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
Describe Barton’s Fracture
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
Describe Hutchinsons fracture
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
Discuss carpal tunnel syndrome
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.
Discuss risk factors for CTS
Obesity Female Coexisting conditions -diabetes -pregnancy -RA -Connective tissue disease Genetic predisposition -Aromatase inhibtor use
Discuss clinical features of CTS
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
Discuss clinical grading of CTS
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
Discuss management of CTS
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
Discuss acute CTS
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.
Describe the monteggia fracture
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
Describe Galeazzis fractures
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
Describe the essex-lopresti lesions
Triad of fracture/dislocation of radial head, interosseous memrbane violation and DRUJ instabilty
Discuss indications for reduction of distal radius fracture in the ED
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
List factors associated with instability of the distal fragment and failure to maintain reduciton
1) presence of intra-articular component
2) shearing fractures
3) palmarly displaced fractures
4) greater magnitude of initial displacment or comminution
