Wrist radiography

Assessment of anatomical relationships and instability

When reading wrist radiographs, it is critically important to assess bone alignment (carpal alignment). Any disruption in the smoothness and integrity of Gilula's arcs (arcs of Gilula) signals traumatic displacement or ligamentous injury. Pathology of the extrinsic ligaments leads to non-dissociative instability—a problem localized between the carpal rows.

If the intrinsic scapholunate ligament is ruptured, dorsal intercalated segmental instability (DISI) develops. Radiologically, this appears as follows:

• On the anteroposterior (AP) view: scapholunate diastasis (pathological widening of the joint space) is identified.
• On the lateral view: the scapholunate angle pathologically increases to exceed 60 degrees (with the normal range being 30 to 60°). Meanwhile, the lunate bone itself exhibits a pronounced dorsal tilt.

Differential diagnosis of carpal bone dislocations

Carpal dislocations account for about 2% of all traumatic dislocations. The area around the lunate bone is most commonly affected. The main danger is misinterpreting a severe dislocation as a simple "ligamentous injury".

1. Perilunate dislocation: occurs from indirect trauma (falling on an outstretched hand with the wrist in dorsiflexion). The lunate bone maintains its correct articulation with the radius, while the rest of the carpal mass and the hand are displaced dorsally. A bayonet-shaped deformity is clinically noticeable.
2. Lunate dislocation: develops upon maximum dorsiflexion. Under pressure from the capitate and radius, the lunate is "squeezed" in a volar direction, completely losing its connection with both the radius and the rest of the carpus.

On the anteroposterior radiograph, the displaced lunate acquires an abnormal triangular shape. However, the lateral view is absolutely essential for accurate differential diagnosis. Both types of dislocations are frequently accompanied by scaphoid fractures.

Wrist fractures and Kienböck's disease

Fractures of the lunate bone are less common than scaphoid fractures and occur when falling on an abducted hand toward the ulnar side. A characteristic clinical sign: when the hand is clenched into a fist, a depression is palpable on the volar surface over the radius. Conservative treatment requires prolonged immobilization in a cast — from 6 to 10 weeks.

A formidable specific complication of fractures is avascular necrosis of bone fragments. Isolated avascular necrosis of the lunate is classified as Kienböck's disease (Kienböck’s disease).

• Radiography (AP): the bone is reduced in size, sclerotic, with signs of subchondral fragmentation.
• MRI: T1-weighted images show low signal intensity from the bone marrow (a sign of osteosclerosis). On fat-suppressed T2 sequences, bone marrow edema may already be absent.

Injuries of the triangular fibrocartilage complex (TFCC)

The TFCC consists of fibrocartilage and normally yields a low signal on all MRI sequences. Clinically, its tears manifest as pain on the ulnar side of the wrist.

• Degenerative tears: often lead to central cartilage perforation. They are associated with a relatively long ulna (positive ulnar variance) and ulnar impaction syndrome—painful abutment of the ulna against the triquetrum.
• Traumatic tears: involve the attachment sites of the TFCC to the ulna. They are frequently combined with ulnar styloid fractures and involve the radioulnar ligaments, leading to distal radioulnar joint (DRUJ) instability.

Imaging findings in juvenile idiopathic arthritis (JIA)

The wrist joint is affected in 61% of patients with polyarticular JIA (ranking second after the knee). The pathogenesis is associated with the proliferation of inflamed synovial tissue—the formation of a pannus that aggressively destroys cartilage and bone, potentially leading to ankylosis.

• Radiography: reveals osteoporosis, erosions, and joint space narrowing. In children, there are specific features: inflammation-induced hyperemia causes osteopenia, local hypertrophy of the condyles, and premature closure of epiphyseal growth plates. Since pediatric joints contain abundant cartilage, X-rays show only late, already established destructive changes.
• MRI and ultrasound: Contrast-enhanced MRI is the most sensitive method for early detection of inflammation and assessment of cartilage perfusion. Doppler ultrasound outperforms clinical examination in detecting occult synovitis and effusion without requiring pediatric sedation.

Class and exam questions

What else to study on this topic

• Technique for closed reduction of a perilunate hand dislocation
• Timing and rules of immobilization in fractures of various carpal bones
• Median and ulnar neuropathy as a complication of fractures
• MRI findings in juvenile dermatomyositis (acute and chronic phases)
• Chronic recurrent multifocal osteomyelitis (CRMO) as a diagnosis of exclusion

Other topics in the "Additional Topics" section

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