MSKForearmWrist

8/7/2019 MSKForearmWrist

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Forearm/Wrist Radiology Jamie Wilson

Radiology of the Forearm, Wrist and Hand

FOREARMSimple Anatomy

The forearm essentially comprises of only 2 bones (radius and ulna) and the joints which they form with each other and articulate with at either end. On plain

radiographs the radius and ulna stand alone, but appearances are deceptive. It isimportant to remember that both bones do not stand alone, but are functionally andanatomically secured at both proximal and distal ends by ligamentous attachmentsThis, in real terms, means that traumatic injury to one bone or one end is VERYLIKELY to be associated with a fracture or dislocation at the other end.Golden Rule = The forearm should be thought of as one unit, and if a recognisedpattern of injury emerges then you always need to rule out pathology at the OTHERend. (DONT FORGET THIS WITH COLLES/WRIST FRACTURES!!)

Normal Radiological AppearanceAP and lateral views are the standard. Run through the OCSEP system as for

any x ray, then start on ABCS. A normal lateral radiograph example is given above.For Alignment Focus on articulation at proximal and distal ends, or any obviousdisplacement.

1. Scaphoid2. Lunate3. Distalend of radius4. Styloidprocess ofulna5. Head ofulna

6. Ulna7. Radius

8. Olecranon9. Tuberosityof radius10. Neck ofradius11. Head of

radius12. Trochlea


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For Bone Be systematic, start at one end and bear in mind the hx when looking atBOTH ends for each bone.For Cortex Be especially wary of changes in the cortex that occur on both sides ofthe bone, this is likely to be fracture. Small lines only on one side of the cortex areprobably nutrient arterial canals and arent important.

Fracture of the ForearmThere are only two fractures of the forearm worth mentioning, and they are both

Italian sounding; Galeazzi and Monteggia.

Galeazzi: Usual hx of FOOOSH (fall on outstretched hand) that leads to distaradius fracture with a dorsally dislocated distal ulna (from disruption to the distaradioulnar ligament.

Monteggia: Hx of FOOSH or direct trauma to proximal forearm leading to fracture ofproximal ulnar shaft with associated dislocation of radial head. View should becentered on the elbow, so check radiocapitellar and radiohumeral lines as well aslooking for anterior fat pad sign (present in most cases). This is also called the Night-stick or side-swipe injury due to its association with self defence or hanging armsfrom car windows on hot days!!

Monteggia

Galleazi


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WRISTSimple Anatomy

Wrist injuries are very common, especially in osteoporotic elderly women whotry and high-five the pavement. Sportsmen and martial arts followers are alsocommon culprits.

In anatomical terms, the wrist is the joint between the distal radius and ulna and

the carpal bones but a wrist x ray will also incorporate much of the hand. In thisrespect, you not only need to know the general pattern of the carpal bones (ANDTHEIR NAMES!!), but also have a good appreciation for their articulation with themetacarpals.

Learning the names and locations of all the carpal bones is absolutely VITAL ifyou dont want to get sued in the next 2/3 years. As an SHO in A+E, you will beexpected to be able to confidently confirm or exclude fractures in the wrist veryquickly you might as well get a head start! Begin with familiarising yourself with thenormal anatomical appearance of the carpal bones in the AP and LATERAL views.

AP

Lat


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Mnemonic for the Carpal Bones (and it isnt rude):

Some Lawyers Take Physicians To The Court House LEARN AND CHERISH

Normal Radiological AppearanceAP and lateral views are necessary in all cases, although you can use other

positions (i.e. full ulnar deviation of hand) to open up the scaphoid more easily.For Alignment Always start with radial/ulnar styloid processes. Then check the 2rows of carpal bones (as indicated in the above diagram carpal blackspace lines)have smooth gaps between them of about 2mm and articulation with metacarpals.For Bone Same as normal, start with radius/ulna, but pay close attention to thescaphoid (most common fracture). Also, look for erosions, joint space, increaseddensities etc.For Cortex Most abnormalities seen in distal radius/ulna, most are fractures (espchildren with greenstick/torus).For Soft Tissue Swelling / Oedema

Fractures Proximal to Wrist

Colles fractures are the most notorious in this region, but there are some othersto be aware of.Colles: Usually a FOOSH leading to fracture of distal radius with dorsadisplacement of the DISTAL fragment => Dinner-Fork deformity on the lateral viewBear in mind, it can be associated with ulnar styloid fracture, impaction and degreesof comminution.Smiths: A reverse Colles fracture. Hx of fall onto back of the hand leads to distasegment being forced ventrally.

Colles Smiths


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Bartons: Fracture on the dorsal aspect of the distal radius that extends into the wristjoint. As it is communicating with the articular surface, it carries a worse prognosis interms of cartilage damage and risk of arthritis in the future.

Torus/Greenstick: These fractures occur in children. A Torus fracture appears as a

wrinkle across the distal radius, whereas a greenstick injury has crinkling of the cortexon one side of the bone with plastic bowing on the other. More severe injuries maycause disruption of the epiphyseal growth plates refer to the Salter-Harrisclassification.

The Scaphoid90% of carpal fractures are in the scaphoid, but 20% of these fractures are NOT

visible at the first X ray. Hence it is important to treat the patient, not the X ray, inthese circumstances. A missed scaphoid fracture is at high risk of developingavascular necrosis due to the orientation of the blood supply, and may lead topremature arthritis in the wrist. Old avascular necrosis occurs in the proximal halfsince the blood supply enters from the distal pole. Tenderness in the anatomical snuffbox should alert your suspicions (+ swelling, reduced movement etc), and if no

Torus Greenstick


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fracture is seen on x ray then still suspect, put in plaster and request another x ray in7-10 days time.

The scaphoid series involves PA, Lat and 2 oblique films. MRI is becomingincreasingly popular as it has increased sensitivity in the first 2-3 days after a fracturebut is not routinely necessary. Consider MRI if persistent pain present and x-ray isnegative 10-14 days post-injury, but most will argue that it probably wont change the

management anyway.

Carpal DislocationsThese are notoriously easy to miss, but should be easy to find if you know what

to look for. Dont forget to look for fractures!Lunate: Most common dislocation in the wrist. You should become aware whenchecking the alignment of the carpal bones, specifically the 2 carpal blackspace linesYou should see 1) loss of joint space between scaphoid and lunate, 2) lunatechanges from rounded quadrilateral into triangular shape and 3) on the lateral viewthe distal radius has no close bony surface running in parallel. The rest of the carpabones remain unchanged (see above).Perilunar: In simple terms, the lunate stays still but the rest of the carpal bones areshunted posteriorly. The diagnosis has to come from the lateral view, where the C-shaped distal articulating surface of the lunate is clearly seen to be EMPTY and thecapitate hangs over the back of the lunate giving a bayonet appearance of thecarpals/metacarpals.

Evaluating the 2 carpal blackspace lines should give you a big clue towardsdiagnosing dislocations. Widening of gap between any two carpal bones (esp

Scaphoid

Fracture

Lunate

Dislocation


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scaphoid + lunate) should make you suspicious of a subluxation/dislocation, and iscalled the Terry-Thomas sign (because of the gap between his teeth!).

HAND

The fingers and thumb contain many different bones and joints, and it is

important to inspect them ALL. Just remember to be logical, and go through theABCS system (pay close attention to the joint margins and look round the edge ofevery bone!).

The ThumbBennetts Fracture: Fractured base of 1st metacarpal extending into the carpo-metacarpal joint, usually from catching the thumb in sports. The main body of the 1s

metacarpal is disconnected and displaced towards the wrist, leaving a small bonyremnant still attached to the 2nd metacarpal. Thumb is then unstable, and may requireinternal fixation.Gamekeepers Thumb: Sudden wrenching of the thumb leading to a rupture of theulnar collateral ligament of the metacarpo-phalangeal joint. This makes the jointunstable and one can use a stress view (radiographer pulls on joint) to demonstratethe extent of the injury. Also requires surgical repair.

Normal Hand


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MetacarpalsBoxers Fracture: Common fracture of the neck of the 5th metacarpal, usuallycaused by striking an opponent/object with clenched fist. It is associated with forwardangulation, and a lateral view is necessary to assess whether reduction is required.Spiral fractures are fairly common in metacarpals, with the extent of rotationadisplacement determining whether internal fixation is required.

PhalangesSmall injuries here can cause massive functional impairments in the future

Remember the important soft tissue components:1) Collateral Ligaments Bind the heads of phalanx to the base of next phalanx2) Volar Plate Thickened joint capsule on palmar aspects of IP joints3) Extensor Tendons Insert into the bases of the phalanges on their dorsa

aspects

Bennetts

Gamekeepers

Boxers

Fracture


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Be aware that each attachment is a potential site of avulsion fractureMallet Injury: Sudden bending force to tip of finger, can come in sport or tucking inbedsheets etc. The extensor tendon is avulsed from terminal phalanx (+/- bonyfragment) so that the tip of the finger droops and loses power in extension. Surgery israrely required, splinting and bandaging usually gives good results.IPJ Dislocations: Can arise from trauma or arthropathies, and some people can

have both PIP and DIP joints affected. PA and lateral views are necessary to knowfull extent and direction of injury.

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