OrthOpaediC iii: injuries tO the upper limb

Fractures and dislocations of the carpusa mahon

m a C Craigen

Abstractthis contribution is an overview of the diagnosis and management of

injuries to the carpus.

Keywords scaphoid; perilunate; carpal injuries; wrist trauma.

Injuries to the carpus are common, and usually follow a fall onto the hand, resulting in hyperextension of the wrist. Injuries range from minor sprains, to scaphoid fractures, to major disruption (e.g. perilunate dislocations).

Scaphoid fractures are the commonest carpal fractures. Tri­quetral fractures are uncommon and all other carpal fractures are rare. Displaced or multiple fractures suggest ligamentous disrup­tion within the carpus.

Ligament injuries range from disruption of the scapholunate ligament (which is common but not often diagnosed acutely) to perilunate dislocation (which is rare).

Significant injuries to the wrist can be quite subtle and should be actively sought in polytrauma, where they are often missed.

Initial assessment

History-taking includes the mechanism of injury, which is usu­ally a fall onto the outstretched hand. Employment status and hand dominance are important in injuries to the upper extremity.

Wrist examination requires a good knowledge of the surface anatomy. Deformity is not as obvious as in fractures of long bones or dislocations of other joints. Localized swelling or evi­dence of a haemarthrosis (see Smith, CROSS REFERENCES) may be present; this is often best seen and felt as fullness in the ana­tomical snuffbox when compared with the opposite wrist).

Systematic palpation for tenderness helps to localize the injury site. Patients may have minimal symptoms with normal range of motion.

A Mahon FRCSI(Tr&Orth) is a Consultant Orthopaedic and Hand Surgeon

at University Hospital of North Durham, Durham, UK.

M A C Craigen FRCS FRCS(Orth) is a Consultant Orthopaedic Surgeon and

Hand Surgeon at Royal Orthopaedic Hospital, and Selly Oak Hospital,

Birmingham, UK.

surGerY 24:12 433

Neurovascular assessment is essential. The median nerve is fre­quently compromised in perilunate dislocation due to the lunate protruding into the carpal tunnel (see Ellis, CROSS REFERENCE). The ulnar nerve is particularly at risk in fractures of the hook of hamate and pisiform.

Specific tests

If a scaphoid fracture is suspected, tenderness should be sought in the anatomical snuffbox and scaphoid tubercle; pain should be sought on longitudinal compression. These tests have a sensitivity of 100%, but are often positive in patients without a fracture.

Clinical tests to assess the integrity of carpal ligaments have been described, but are unlikely to be helpful in the acutely injured wrist.

Imaging

Good-quality radiographs are essential to diagnosis. Postero­anterior and lateral views of the wrist are the required, and other views may be needed depending on examination findings and suspected injury.

Scaphoid views should be obtained if a scaphoid fracture is sus­pected from the clinical findings. These consist of at least four views: posteroanterior, lateral and two oblique views. The posteroanterior view should be taken with the wrist in ulnar deviation because this action brings the scaphoid into extension, making it parallel with the X­ray plate; this view identifies most scaphoid fractures.

A carpal tunnel view highlights the pisiform and hook of hamate, but may be difficult to obtain in the acutely injured wrist. Oblique views may help to profile the ulnar part of the carpus. CT is often the only way to reliably image fractures on the ulnar side of the wrist.

Scaphoid fractures

Scaphoid fractures comprise about 80% of carpal fractures; about 80% occur in males and about 80% are ‘waist’ fractures. Most patients are between 20 years and 30 years of age.

Fractures are divided into: • middle third (or waist) fractures • proximal pole fractures • distal third fractures (uncommon). A displaced fracture disrupts the linkage between the proximal and distal carpal rows, it may also be part of a more major carpal disruption (e.g. trans­scaphoid perilunate dislocation).

The scaphoid is almost completely covered in articular cartilage. The blood supply enters the bone at points of ligament attachment over the distal two­thirds of the bone, with the proximal pole being dependent on the intraosseous circulation (i.e. the blood supply of the proximal fragment is at risk in proximal pole fractures).

DiagnosisA scaphoid fracture should be suspected in patients presenting with radial­sided wrist pain after hyperextension injury to the wrist; evidence of a haemarthrosis may be present. Tenderness in the anatomical snuffbox and over the scaphoid tubercle suggests a scaphoid fracture. The range of movement of the wrist is often normal.

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OrthOpaediC iii: injuries tO the upper limb

 a plain radiograph (posteroanterior view) of the wrist failed to show the scaphoid fracture that is clearly seen on b mri (arrow).

Figure 1

Occult scaphoid fracturesMost scaphoid fractures are visible on the initial radiographs, but occult fractures can occur. The care of a patient with a suspected scaphoid fracture and a normal radiograph depends on resources. MRI using an extremity coil is the most sensitive and specific way of identifying or excluding such fractures, and may identify other injuries (Figure 1). CT can clearly define the anatomy of a fracture, but may miss a fracture if it lies parallel to the CT slices. CT should, therefore, be done in the long axis of the scaphoid. Bone scintigraphy is extremely sensitive but less specific.

Traditional teaching says that occult fractures may become apparent after 10–14 days due to bone resorption at the frac­ture site: there is little evidence for this. Immobilization in a cast for two weeks may have symptomatic benefit to patients with a wrist injury in the absence of a fracture. It may also be easier to clinically assess the patient when reviewed after this short period of immobilization. Repeat clinical and radiographic examination after this should identify most fractures, leaving a small number requiring further imaging.

Early further imaging in suspected scaphoid fractures may be more cost effective than repeat visits to clinic.

TreatmentConservative: undisplaced scaphoid waist fractures are usu­ally treated conservatively. A well­fitting below­elbow cast pro­vides adequate protection. Whether or not the thumb should be

surGerY 24:12 43

included is controversial, but there is no evidence that including the thumb is necessary.

The duration of immobilization must be sufficient to allow fracture healing, but must be balanced against the risk of stiffness. A period of 8–12 weeks’ immobilization, depending on radio­graphic evidence of union, is reasonable. There is no evidence that immobilization beyond 12 weeks is beneficial, but fractures can unite after that time without surgery. Deciding whether or not a fracture has healed by clinical examination and radiographs can be difficult and CT may be required in some cases. Fractures that are not progressing towards union after a suitable period of conservative treatment should be considered for surgery if symp­tomatic.

Surgical: relative indications for surgical treatment in the acute setting are: • fracture displacement of >1 mm (suggests an unstable frac­

ture or associated ligament disruption) • angulation at the fracture site (suggests fracture instability) • evidence of carpal instability (e.g. associated perilunate

dislocation) • previously undiagnosed non­union presenting after an acute

injury.Other indications are: • proximal pole fractures (conservative treatment requires

lengthy immobilization and the non­union rate is higher in these injuries)

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OrthOpaediC iii: injuries tO the upper limb

 a radiograph (posteroanterior view) of a wrist showing perilunate dislocation (as indicated by disruption of Gilula’s arcs) when

compared to b a radiograph (posteroanterior view) of a normal wrist.

Figure 2

• percutaneous fixation of undisplaced fractures (can lead to earlier return to work or sport, although it does not increase the union rate)

• associated injuries to bones in the hand or forearm. The commonest method of fixation is a compression screw and several types exist. Bone graft (see Marsh, CROSS REFERENCES) is not usually required in acute injuries unless there is commi­nution.

Fractures of other carpal bones

Fractures of other carpal bones are far less common than scaph­oid fractures. Triquetral fractures account for about 13% of carpal fractures, and the remaining six bones for only about 10%. A high index of suspicion is required because radiographic appearances can be subtle. A displaced fracture or fracture of more than one car­pal bone points to the possibility of carpal dislocation (about 50% of capitate fractures are associated with perilunate dislocation).

Ligamentous injuries

Most ligamentous injuries occur in an arc around the lunate and are termed perilunate injuries or dislocations. They are caused by an indirect mechanism. A hyperextension injury occurs with varying degrees of supination and ulnar deviation.

Stages of ligamentous injuryMayfield et al carried out cadaveric studies and defined four stages of injury.1

• Stage I: as the scaphoid is forced into extension and supina­tion, the scapholunate ligament tears from volar to dorsal, or alternatively, the scaphoid fractures.

surGerY 24:12 435

• Stage II: further extension results in dorsal translation of the distal row from the lunate (there is no ligament connecting lunate to capitate). This can lead to tearing of the volar wrist capsule. • Stage III: further deformation leads to tearing of the luno­triquetral ligament or fracture of the triquetrum. • Stage IV: at this stage, all of the ligaments surrounding the lu­nate have torn, apart from the radiolunate ligaments. The carpus falls back into alignment with the radius, pushing the lunate into the carpal tunnel.

Carpal ligament injury can range from minor partial tears of the scapholunate ligament to major disruptions of the carpus. Many patients diagnosed as having wrist ‘sprains’ are likely to have stage­I or ­II injuries, which may subsequently become problematic.

Injuries may be purely ligamentous or involve fracture of the radial styloid, scaphoid, capitate, triquetrum or a combination of these. Trans­scaphoid perilunate dislocation is the common­est. Other patterns include trans­styloid, trans­scaphoid, trans­ triquetral, trans­scaphoid and trans­capitate.

Radiographic evaluationA number of features should be observed when evaluating radiographs of the wrist. The wrist must be in a neutral position because deviation from this will affect the relative positions of the carpal bones.

On the posteroanterior view, there should be three smooth arcs (‘Gilula’s arcs’; Figure 2). • The first is the line of the articular surfaces of the proximal carpal row at the radiocarpal joint. • The second is the line of the articular surfaces of the proximal carpal row in the mid­carpal joint.

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OrthOpaediC iii: injuries tO the upper limb

• The third is the line made by the articular surfaces of the capi­tate and hamate at the mid­carpal joint.A step in these smooth arcs indicates a carpal disruption at that site. A gap of >2 mm between adjacent carpal bones points to the possibility of carpal disruption. Injury to the scapholunate ligament can cause the scaphoid to flex and appear shortened. This will also put the scaphoid tubercle into prominence (‘signet ring sign’).

On the lateral view, the radius, lunate and capitate should be in line. The lunate may become flexed or extended relative to the radius if disruption of carpal ligaments is present. The scapho­lunate angle, between the long axes of scaphoid and lunate, should be between 30° and 60°.

Fractures of the radial styloid, scaphoid or other carpal bones may be seen. If fractures of two or more of these bones are seen, ligament disruption is likely even if the radiographs are other­wise normal.

General points: if radiographs suggest a subtle ligament injury, one must decide if this fits with the clinical picture; a radiograph of the opposite wrist may be helpful. Ligament injuries are often asymptomatic and longstanding.

TreatmentLigamentous injuries without subluxation are rarely diagnosed acutely but repair or stabilization may be indicated if present. The patient should be treated in a plaster slab initially and referred to a hand surgeon if ligament disruption without dislocation is suspected.

Perilunate dislocations are a surgical emergency requiring urgent reduction. Opinion differs regarding definitive manage­ment, but most wrist specialists recommend open reduction and Kirschner­wire (K­wire) fixation with ligament repair or recon­struction. Internal fixation is indicated if a fracture is present. The median nerve is often compressed due to subluxation of the lunate and often requires decompression.

surGerY 24:12 43

Axial pattern injuries

Axial pattern injuries are rare high­energy injuries caused by crushing in an anteroposterior direction. This causes flattening of the carpal arch, leading to ligamentous and possible bony failure, separating a column of carpus and metacarpals from the rest of the hand (e.g. the hamate, pisiform and fourth and fifth metacarpals may separate as a unit from the rest of the carpus and metacarpus).

These are complex, often open injuries, treated by debride­ment, open or closed reduction, and fixation. ◆

ReFeRence

1 mayfield jK, johnson rp, Kilcoyne rK. Carpal dislocations:

pathomechanics and progressive perilunar instability. J Hand Surg

Am 1980; 5: 226–41.

cROSS ReFeRenceS

ellis h. the carpal tunnel. surgical and clinical anatomy for the mrCs

examination. www.surgeryjournal.co.uk

marsh jl. principles of bone grafting: non-union, delayed union.

Surgery 2006; 24(6): 207–10.

smith a, moran C. soft tissue injuries of the knee. Surgery 2006;

24(11): 376–81.

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barton nj. twenty questions about scaphoid fractures. J Hand Surg Br

1992; 17: 289–310.

Green dp, hotchkiss rn, pederson WC, Wolfe sW, eds. Green’s

operative hand surgery, 5th edn. london: Churchill livingstone,

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smith p, ed. lister’s hand diagnosis and indications, 4th edn. london:

Churchill livingstone, 2002.

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