Imaging quiz cases: imaging of the wrist (2024)

Quiz case 1. Trans-scaphoid perilunate dislocation

Question 1

A 35-year-old male falls from a height onto the outstretched hand. Radiographs of the wrist were obtained (Figures 1 and 2).

What are the radiological findings?

What treatment has been given?

Answer

There is a fracture through the waist of the scaphoid associated with a perilunate dislocation consistent with a trans-scaphoid perilunate dislocation.

This has been treated by open reduction and fixation with Kirschner wires across the lunotriquetral interval and a Herbert compression screw across the trans-scaphoid fracture.

These are extremely important injuries, 25%¹ are missed at initial presentation and may lead to serious complications. They can occur following high-energy trauma, such as road traffic accidents or sporting injuries, causing hyperextension of the wrist. 26% of injuries are associated with polytrauma.

Perilunate dislocations occur in a sequence of events involving either ligament and/or bony disruption. This injury pattern typically starts on the radial side and destabilizes either through the body of the scaphoid or through the scapholunate interval.

Mayfield et al² described the ligamentous sequence of events:

• Stage 1. disruption of the scapholunate ligament

• Stage 2. disruption of the midcarpal (lunocapitate) articulation

• Stage 3. disruption of the lunotriquetral ligament resulting in a perilunate dislocation through the “space of Poirier”, a weakness in the volar capsule.

Johnson³ described the greater arc of injury, which involves the bones around the lunate: scaphoid, capitate, hamate and triquetrum, resulting in a fracture through one or more of these bones associated with a perilunate dislocation.

Prompt treatment with adequate reduction is necessary to prevent carpal instability, post-traumatic osteoarthritis and avascular necrosis of the lunate.

Median nerve compression may be a reason for urgent surgical intervention.

Quiz case 2. Lunate avascular necrosis, negative ulnar variance and Type II lunate with hamatolunate abutment

Question 2

A 35-year-old male presents with chronic wrist pain (Figures 3 and 4). What do the radiographs demonstrate?

The patient went on to undergo an MR, what additional findings are demonstrated?

Answer

The plain film radiographs demonstrate negative ulnar variance with cystic change within the lunate consistent with avascular necrosis.

Coronal T₁ demonstrates diffuse abnormal low signal throughout the lunate with corresponding diffuse hyperintense signal on the coronal short tau inversion recovery sequence confirming avascular necrosis of the lunate with focal cystic change.

In addition, there is a Type II lunate with subchondral cystic change within the proximal hamate in keeping with hamatolunate abutment syndrome.⁴

Avascular necrosis of the lunate is associated with negative ulnar variance and is commonly seen in males between the ages of 20 and 40 years. Its cause remains unclear but has been associated with repetitive stress to the lunate as seen in pneumatic drill workers or following an acute traumatic episode.

Quiz case 3. Lipomatosis of the nerve

Question 3

A 29-year-old male presents with several months history of swelling in the hand and symptoms of carpal tunnel syndrome (Figure 5).

Describe the clinical features shown in the photograph and the radiological features on the axial T₁ weighted MR. What is the diagnosis?

Answer

The hand demonstrates macrodactyly in the median nerve distribution.

The axial T₁ MR shows the pathognomonic appearance of extensive intraneural fatty proliferation surrounding the nerve fascicles giving a cable-like appearance on axial imaging. This is evenly distributed around the thickened nerve fascicles.⁵

The diagnosis is lipomatosis of the nerve (LON).

Mason⁶ first described this condition in 1953. It is a benign, rare, congenital, slowly growing intraneural tumour with progressive proliferation of fatty tissue around the nerve fascicles.

There is a clear demarcation of the nerve from surrounding tissues. The most common location is the median nerve at the level of the wrist.

Historically, authors have used many different terms to describe this rare lesion, including extensive neuroma, lipofibromatous hamartoma, neural fibrolipoma and intraneural lipofibroma.

In an attempt to bring clarity to the confusion around nomenclature in 2002, the World Health Organization committee for the Classification of Soft Tissue Tumours renamed this lesion “lipomatosis of nerve”—in order to recognize that this is essentially an intraneural adipocytic proliferation, sometimes accompanied by a focally fibrous stroma.

Typically, LON manifests before the third decade and is most commonly seen in Caucasians. Its aetiology is unknown.

Two-thirds of patients present with macrodactyly at birth or during early childhood, often with aesthetic concerns or stiffness in the fingers due to bulkiness of subcutaneous fatty infiltration. Macrodactyly is a global enlargement of every element of the finger and can be found in the distribution of the affected nerve.

The excessive volume of fat and fibrosis within the nerve may lead to nerve compression in anatomical sites where no distension of the surrounding tissues is possible. As adults, patients may therefore present with symptoms of a compressive neuropathy, such as tingling, numbness and an aching pain.

Later in life, progressive loss of finger flexion is a common functional complaint, due to bulkiness of enlarged tissues and early degenerative process in joints of the affected fingers.

Treatment is usually conservative because of the risk of nerve injury and chronic pain.

Nerve decompression is performed in cases of carpal or cubital tunnel syndrome, and debulking and amputation are also common procedures.

Nerve excision is not recommended, as the results of grafting remain poor.

Quiz case 4. Fourth and fifth carpometacarpal joint dislocation

Question 4

A 27-year-old female falls and injures her hand. Radiographs of the wrist were obtained (Figure 6).

What are the radiological findings? How is this treated?

Answer

There is dorsal dislocation of the fourth and fifth carpometacarpal (CMC) joints with associated soft-tissue swelling. The ulnar margin of the base of the fifth metacarpal does not line up with the ulnar border of the hamate on the anteroposterior view.

This is an uncommon injury and can be easily missed. Recognition is dependent on careful physical and radiological examinations.⁷

Dislocation may be in a palmar or dorsal direction. The ring and little finger CMC joints are more susceptible to dislocation than the immobile index and middle fingers. The fifth CMC joint is the most commonly injured. They may be associated with fractures of the base of the metacarpals, dorsal aspect of the hamate or carpal bones. In dorsal dislocations of the fifth CMC joint, the extensor carpi ulnaris pulls the fifth metacarpal proximally.⁸

Most injuries may be treated successfully by closed reduction and percutaneous fixation of the joints with Kirschner wires.

References

© The British Institute of Radiology 2014