Hand Radiology ABC 4 Hojas

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doi:10.1136/bmj.330.7499.10732005;330;1073-1075BMJ

Otto Chan and Tudor Hughes

Hand

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ABC of emergency radiologyHandOtto Chan, Tudor Hughes

The hand is exposed and at risk of injury. It is therefore notsurprising that hand injuries are the commonest skeletalinjuries, and they account for 10-20% of attendances at accidentand emergency departments. Fractures of the phalanges aremore common than fractures of the metacarpals. Fractures ofthe distal phalanx account for half of all phalangeal fractures.Metacarpal injuries occur most commonly in the thumb andlittle finger.

Most injuries of the hands are easy to detect and correlatewell with clinical findings. Identification of injuries is essentialbecause early detection and appropriate management usuallyleads to recovery of normal function. Conversely, delay indiagnosis of what seems to be a minor abnormality can lead to

a severe disability. Surgery is rarely necessary and only indicatedfor specific injuries. Clinical examination determines whichradiographic views should be obtained.

AnatomyEach finger consists of one metacarpal and three phalanges,and the thumb consists of one metacarpal and two phalanges.Each bone has a head, a shaft, and a base. Strong ulnar andradial collateral ligaments prevent sideways movement of the

joints. The joint capsule of the interphalangeal andmetacarpophalangeal joints is thickened on the palmar (volar)aspect and forms a dense fibrous structure (volar plate). This

attaches to the base of the phalanx. Each finger has two flexortendons and one extensor tendon. Sesamoid bones may befound on the palmar aspect of the hand, most commonly in theflexor tendons of the thumb at the level of themetacarpophalangeal joint.

ABCs systematic approachAssessment of radiographs should follow the ABCs system:x Adequacyx Alignment

x Bonex Cartilage and jointsx Soft tissues

Distal phalanx

Common extensor tendon

Distal interphalangeal joint

Middle phalanx

Proximal phalanxProximal

interphalangealjoint

Ulnarcollateralligament

Metacarpal

Radial collateral ligament

Middle slip

Volar plate

Dorsal (left) and lateral (r ight) view of left index finger

Anteroposterior (left) and lateral (middle left) view of thumb.Anteroposterior (middle right) and lateral (right) view of finger

Anteroposterior (left) view of index finger showing soft tissue swelling overthe proximal interpharangeal joint. The lateral view (right) confirms adislocation

This article is adapted from the 2nd edition of the ABC ofEmergency Radiology, which will be published in theautumn

Anteroposterior (left) and oblique (right) view of the hand

Clinical review

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AdequacyAnteroposterior and lateral views should be obtained for fingerinjuries, and anteroposterior and oblique views are needed forhand injuries. Special views may be necessary for specificinjuries, such as thumb injuries.

AlignmentCheck the alignment of each finger and thumb on two views.

BoneExclude a fracture by carefully following the bony contour ofeach digit on two views. Then check the bone density andtrabecular pattern. Occasionally, a vascular groove can beconfused with a fracture.

Cartilage and jointsThe joint space should be uniform in width. Overlap of bonemargins may indicate a dislocation, and a second view shouldconfirm this.

Soft tissuesAlways use a bright light to look for soft tissue swelling. Thismay be the only sign of an injury. When radiographs are takento detect foreign bodies a metallic marker should always beplaced at the site of the injury, tangential to the site of entry.Foreign bodies may be visible on one view only.

InjuriesDistal phalanges

Crush fractureThis is an extremely common injury in which the tuft issquashed and sustains a marginal chip or a comminutedfracture. Generally, a nail bed or pulp soft tissue injury is

associated with a crush fracture.

Mallet finger (baseball finger)Often caused by a direct blow to the extended digitthere is anavulsion of the extensor tendon at its insertion to the base ofthe distal phalanx. A less common injury is an avulsion of asmall fragment of bone from the dorsal aspect of the base ofthe distal phalanx. The diagnosis is clinical and obviousaflexion deformity of the distal interphalangeal joint.

Radiography is done to assess the size of the bony fragment.Most of these injuries heal with simple splinting of the joint(with a mallet splint), but complete tears of the tendon mayneed surgery.

Middle phalanges

Boutonnire deformityThis is a deformity of the digit with extension of the distalinterphalangeal joint, flexion of the proximal interphalangeal

joint, and no associated bony abnormality on the radiograph.The extensor mechanism attachment is torn, and splinting inhyperextension of the proximal interphalangeal joint isindicated to prevent a long term fixed flexion deformity.

Volar plate avulsionThis fracture is quite common. It is secondary to ahyperextension injury and sometimes associated with adislocation of the proximal interphalangeal joint. The avulsedfragment of bone is often very small and difficult to identify.

The fragment is sometimes seen only on an oblique view as atiny flake of bone, and the clue to its presence is soft tissueswelling.

ABCs systematic approach

Adequacy and alignmentx Two views are needed to exclude dislocation of a fingerx Oblique or lateral view is needed to detect a Bennetts fracturex Ultrasonography is needed to detect gamekeepers thumb

Bone

The commonest sites of injury are:x Finger tip (crush fracture)x Base of distal phalanx (mallet finger)x Neck (base or shaft) of fifth metacarpal (boxers fracture)

Cartilage and jointsx Look for overlapped joint space indicating subluxed or dislocated

jointfor example, Bennetts fracture

Soft tissuesx A marker of soft tissue exposure is needed to detect foreign bodiesx Radiography can localise soft tissue injury

Anteroposterior view ofindex finger showingcrush fracture (left) andvolar plate avulsion(right)

Mallet finger without(left) and with (right)fracture

Boutonnire deformity

Clinical review

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Proximal phalanges

Spiral or transverse fractureIn this fracture the digit is often shortened and rotated; theinjury is usually caused by of a direct blow. The deformity isgenerally more obvious when patients flex their fingers.

Angulation is best evaluated with a true lateral view or oblique

view. The anteroposterior view usually underestimates thedegree of angulation and shortening.

Metacarpal bones

Punch fracture (boxers fracture)This is the direct result of a punch. The neck of the metacarpalis fractured, and there is volar displacement of the head. Usuallythe fifth metacarpal is damaged, but injury can also occur at thehead of the fourth or other metacarpals. The history andclinical findings are characteristic (although patients often denythey have been in a fight) with flattening of the knuckle. Adegree of angulation is accepted as this causes negligiblefunctional disability. The original description of a boxersfracture was a fracture of the base of the fifth metacarpal.

Other metacarpal injuriesOblique or even transverse fractures of the shaft or base of themetacarpals can occur in one or more metacarpals. Sometimesthe fracture occurs at the base and the carpometacarpal joint,and there is the possibility of an associated dislocation orsubluxation of the joint. These fractures are sometimes besttreated with pin fixation.

Thumb injuries

Bennetts fracture and dislocationThis is an oblique fracture of the base of the first metacarpaland dorsal dislocation or subluxation of the first metacarpal.

The fracture extends to the carpometacarpal joint and thedisplacement is made worse and more unstable by the abductormuscles of the first metacarpal. The management of this injury

is controversial. It can be treated by closed reduction withsplinting, closed and percutaneous pin fixation, or openreduction and pinning. Referral to a specialist orthopaedicsurgeon is mandatory.

Gamekeepers thumb (skiers thumb)An abduction injury of the thumb occurs when there is outwarddistraction of the thumb and an avulsion of the attachment ofthe ulnar collateral ligament (which can be associated with a

bony avulsion fracture). Stress films may show further wideningof the joint space on the ulnar aspect, but these films are notrecommended as they can aggravate the injury.Ultrasonography should confirm the diagnosis. These injuriesmay be treated conservatively, but complete tears of the ulnar

collateral ligament may require surgery.

Key pointsx History is important because the mechanism of injury oftenprovides a clue to diagnosisx Clinical examination will give a strong clue to the diagnosisx Early diagnosis and appropriate management is essential forfull recoveryx ABCs systematic approach should be used to reviewradiographs

Tudor Hughes is professor of radiology, University of California SanDiego Medical Centre, San Diego, USA

TheABC of Emergency Radiologyis edited by Otto Chan, consultant

radiologist, Royal London Hospital, London([email protected])

BMJ2005;330:10735

Punch fractures of fifth metacarpalhead (left) neck (middle), andbase (right)

Anteroposterior view of the ring finger seems almostnormal (left), but the oblique view shows an obliquefracture of base of fourth and fifth metacarpals (arrow)

Bennetts fracture and dislocation

Gamekeepers thumb (skiers thumb). Arrow shows fracture attached toulnar collateral ligament (note the sesamoid)

Clinical review

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Hand Radiology ABC 4 Hojas

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