Introduction

The clinical evaluation of the wrist and hand regularly results in the use of diagnostic imaging to determine the origin of the patient’s pain or complaint. Commonly, radiographs are taken to assess the osseous structures in particular; however, due to the complexity of the wrist and hand, coupled with the importance of this region in the ability to perform activities of daily living (ADLs), it is often vital that the soft tissue components can be scrutinized to achieve an accurate diagnosis.

In the past, further imaging has consisted of computed tomography (CT) and, in more recent times, ultrasound; however, the detail afforded by magnetic resonance (MR) imaging in determining the anatomical relationships of structures such as the fibrocartilage complex and the ligaments and tendons, which confer the function and stability to the wrist, and hand, has increasingly resulted in MR imaging being adopted to evaluate the detail of this region of the body.

History and examination

Much of what has already been written about the history-taking for the shoulder and elbow also holds true for the wrist and hand: it is part of a kinematic chain and clinical thinking must be directed to the other components of that chain, which may be responsible both for disrupting distal biomechanics and perpetuating symptoms and for referring proximal pathology.¹ It is also necessary to be alert for ‘double crush’ mechanisms of neural entrapment: the nerves that pass through the wrist are also subject to entrapment in the elbow, arm and thoracic outlet, which can refer pain or be comorbid with local entrapment.²

More than any other area, it is essential to enquire about the patient’s side of handedness, occupation and activities of daily living. Even in the face of an obvious precipitating cause, factors such as repetitive activity, computer use, writing and ergonomics can profoundly affect both management and prognosis.

Examination of the wrist and hand, perhaps unsurprisingly, reflects that of the ankle and foot, with emphasis on observation; active and passive ranges of motion; neurological assessment; digital palpation; and muscle testing. There is, again, a paucity of meaningful special orthopaedic tests; the one exception to this is Finkelstein’s test for stenosing tenosynovitis of the tendons of extensor pollicis brevis and abductor pollicis longus.³ This test involves the patient opposing their thumb so that it lies across the palm, then grasping it with the fingers so that it lies within a clenched fist. The examiner then forcibly adducts the thumb to recreate the patient’s symptoms. The examination should also include evaluation of the elbow, shoulder, thoracic outlet and cervical spine.⁴

The presence of obvious and persistent neurological signs and symptoms would, in the first instance, be likely to precipitate referral for nerve conduction studies; otherwise, diagnostic imaging is the next step for the inconclusive examination or unresponsive patient.^5,6

Clinical indications

MR imaging of the wrist and hand is performed in a variety of clinical scenarios. For example, in the case of trauma-induced wrist pain, MR imaging of the wrist is useful to determine damage to the soft tissues, such as the scapholunate ligament and triangular fibrocartilage complex, both crucial in maintaining the stability and, therefore, function of the wrist. The same is true of the hand, which is often comorbid with the wrist, and where lesions commonly affect the extensor and flexor mechanisms, both in cases of trauma and non-traumatic deformities.

MR imaging allows visualization of the anatomical structures that enables assessment of the anatomical and functional relationships of the area. In addition to the tissues that may be affected directly by trauma, complications may be also evaluated – such as the development of avascular necrosis, which commonly affects the scaphoid as a complication of fractures. This condition may be studied with great sensitivity using MR imaging and at an earlier stage than with radiography and this may, in some circumstances, alter the clinical prognosis and management of the patient. MR imaging is also useful in assessing the status of the median nerve, and for evaluating the presence of fibrosis, or scar tissue, that may be impeding full recovery for the patient with carpal tunnel syndrome.

Protocols

MR imaging of the wrist and hand may be performed with the patient supine or prone. The prone position is usually reserved for larger patients, where the wrist and hand are placed over the head of the patient, in the ‘Superman’ position. A surface coil will invariably be applied to the patient’s wrist or hand to improve the signal-to-noise ratio and maximize the quality of the image.

The MR imaging study will normally consist of all three imaging planes: coronal, axial and sagittal, which are normally planned from the axial scout view. T1-weighted and T2-weighted sequences are usually performed in one or more imaging planes, with a slice thickness of 1 to 3 mm being adopted. However, depending on the clinical indication for MR imaging of the wrist and hand, particular sequences or even planes may be selected. In the wrist, the imaging study includes the distal radius and ulna up to the bases of the metacarpal bones. In the hand, the imaging study will normally include the distal carpal row to just beyond the distal aspects of the fingers.⁷

For either area, contrast may be added, depending on the nature of the clinical situation being investigated. The contrast may be added via the intravenous route, to attempt to differentiate a soft tissue mass or active inflammation⁸ or, in some institutions, injected directly in to the joint to perform MR arthrography⁹; however, due to the inherent contrast from the fluid in the wrist, these procedures are not usually necessary. Some institutions have advocated imaging with varying positions of the wrist, placing the patient in pronation and supination in order to further study the ligamentous relationships in these positions¹⁰; however, this has not been adopted as standard protocol in most imaging institutions.

Normal and abnormal imaging appearances of the wrist and hand

Perhaps it is because of the wealth of structures contained in a very limited space that it is, unlike in all of the previous chapters, easier to consider normal and abnormal pathology together on a topic-by-topic basis: it is useful to develop a standard order in which to evaluate these structures so as to be methodical for each imaging study that is presented to the practitioner.

Osseous structures

The coronal imaging study will provide information regarding a number of areas, including the overall gross alignment (Figure 10.01, Box 10.01). On these images, the convex head of the ulna and the articular surface of the distal radius should be at the same level; any variance from this can indicate abnormal stresses being placed on the wrist, and is associated with a number of syndromes (Table 10.01).^11–15

Figure 10.01 • Coronal T1-weighted MR imaging of the wrist demonstrating the proximal and distal carpal rows in detail. Note the alignment of the carpal bones in both carpal rows as well as the homogeneous signal intensity in this patient where the bony structures are normal. In addition, the triangular fibrocartilaginous complex is seen as a low signal region just proximal to the lunate and triquetrum (oval).

Box 10.01 Key to anatomical structures in annotated figures

c Capitate

h Hamate

l Lunate

p Pisiform

s Scaphoid

td Trapezoid

tm Trapezium

tq Triquetrum

* Hook of the hamate

# Triangular fibrocartilage complex

I, II, III, IV, V – metacarpals

1. Interosseous muscles

2. Dorsal intercarpal ligament

3. Extensor retinaculum

4. Abductor pollicis longus tendon

5. Extensor pollicis brevis tendon

6. Extensor carpi radialis brevis tendon

7. Extensor carpi radialis longus tendon

8. Extensor carpi ulnaris tendon

9. Extensor pollicis longus

10. Extensor digitorum & indicis tendons

11. Extensor digiti minimi

12. Flexor carpi ulnaris tendon

13. Flexor digitorum superficialis

14. Flexor digitorum profundus

15. Flexor pollicus longus

16. Flexor carpi radialis

17. Radial artery

18. Ulnar artery and nerve

19. Median nerve

20. Thenar muscles

21. Flexor & abductor digiti minimi

22. Flexor retinaculum

23. Extensor digitorum and tendon

24. Flexor tendons of the digits

25. Dorsal digital vein

26. Palmar digital artery

27. Radial collateral ligament

Table 10.01 Syndromes associated with distal radioulnar misalignment

Ulna proximal to radius > 2 mm	Radius proximal to ulna > 2 mm
Avascular necrosis of the lunate (Kienböck’s disease) or scaphoid Epiphyseal injury Rett syndrome Chondromalacia of the ulnar head Scapholunate disassociations

Impaction between ulna and lunate

Triangular fibrocartilage complex tear

Distal radial growth-plate injury (most commonly associated with child gymnasts)

It is also essential to determine that all the carpal bones are present in the proximal and distal carpal rows (Figure 10.01). Carpal coalition is a condition whereby incomplete segmentation has occurred, resulting in two or more of the carpal bones appearing fused; most commonly, the lunate and triquetrum or the capitate and hamate,^16–18 although any adjacent bones may seemingly be involved.^19–25 The distal carpals may also be congenitally fused with the metacarpals, the most common coalition being between the second metacarpal and trapezoid.²⁶ Accessory ossicles may be present, which represent a normal variation, usually without clinical consequence to either the patient or physician; one exception to this is the presence of an os styloideum, a common bony protuberance located on the dorsal surface of the base of the second and third metacarpals, which may be associated with degenerative changes, bursitis or ganglia.^26,27 In patients with a history of trauma, ossification may occur in and around tendons, resulting in the appearance of osseous lesions about the wrist and hand, a form of myositis ossificans (Figure 10.02).²⁸

Figure 10.02 • MR imaging of the wrist in the coronal (A) and axial (B) planes using T1-weighted sequences. The circles outline a region of increased signal intensity corresponding to bony marrow, owing to the presence of ossification within the extensor carpi ulnaris tendon from a previous trauma. Also of note is the apparent widening of the scapholunate joint distance (arrow), although this may be normal and needs to be verified on the surrounding slices. A follow-up radiograph (C) demonstrates the large regions of increased density located just distal to the ulnar styloid process, most likely due to the previous injury to this region, forming myositis ossificans around the extensor carpi ulnaris.

Triangular fibrocartilage complex

Familiarity with the soft tissue structures of the wrist and hand is particularly important, owing to their role in maintaining the stability of the wrist. In the coronal plane, the triangular fibrocartilage complex (TFCC) is well demonstrated with its contributing structures, including the meniscus and ulnar collateral ligament (Figure 10.01). The TFCC is a biconcave structure located in the region of the wrist between the ulna and the proximal carpal row, with attachments to the ulnar styloid process by bands of tissue and similarly attached to the radius (Figure 10.03). It stabilizes the ulnocarpal and radioulnar joints, facilitates complex movements at the wrist and distributes loads from the carpus to the ulna.^29,30 Between the TFCC and the radius is a region of intermediate signal on MR images, which represents hyaline cartilage.

Figure 10.03 • MR imaging of the wrist in the coronal plane, three-dimensional volume acquisition using a gradient echo sequence in a 22-year-old male with pain in and about the wrist. This imaging study demonstrates the triangular fibrocartilage complex in exquisite detail, with visualization of the meniscus homologue, which then has fibres that continue to insert onto the ulnar styloid process (oval). Disruption anywhere along this region may result in instability to the wrist.

Tendons

The tendons of the wrist can be best evaluated in the axial plane; in the hand, the sagittal plane is, initially, the primary plane for diagnostic information. The normal appearance of a tendon in the wrist and hand is that of a low signal intensity structure that is both linear and continuous. About the wrist, the tendons are divided into compartments for both anatomical and imaging description. The two main regions for the tendons of the wrist are the extensor and flexor groups (Figure 10.04). The median nerve lies amongst the flexor tendons as they travel through the wrist and may be involved in the development of symptoms and signs of carpal tunnel syndrome (Figure 10.05).³¹ The extensor tendons run along the dorsal aspect of the wrist towards the hand and may cross over each other, leading to friction syndromes. These tendons may vary in their shape, with the extensor carpi radialis brevis appearing rather elongated in the axial plane (Figure 10.06). The tendons are normally surrounded by a small degree of fluid, which can accumulate in conditions such as tenosynovitis. This can be caused by direct trauma or by systemic disorders that promote a generalized inflammatory process, such as rheumatoid arthritis (Figure 10.07) and are often accompanied by osseous involvement such as erosions.

Figure 10.04 • Axial T1-weighted MR image of the wrist demonstrating the relationship between the bony structures of the distal radius and ulna with the compartmentalized tendons. Note the extensor group (rectangle) and the flexor compartment (oval).

Figure 10.05 • Axial T2-weighted MR image of the wrist at the level of the hook of the hamate [*]. The tendons within the carpal tunnel, small oval regions of low signal intensity, are noted; the superficial volar-placed tendons are those of flexor digitorum superficialis. Those deeper and more posterior represent the tendons of flexor digitorum profundus.

Figure 10.06 • Axial T1-weighted MR imaging of the wrist at the level of the hook of the hamate demonstrating the tendons about the wrist, in particular those of the carpal tunnel (oval). In addition, along the dorsum over the wrist, regions of low signal intensity overlying the carpal bones represent the tendons of the extensors, including that of extensor carpi radialis brevis.

Figure 10.07 • Axial, T1-weighted, fat-saturated sequence of the fourth finger (A), where the tendons are noted as low signal intensity structures. In this patient, whereas the flexor tendons of the second and third digits are of normal signal intensity and size, the flexor tendons about the fourth digit are larger than normal and a moderate amount of soft tissue swelling is noted around this region. A similar region is seen about the extensor tendons of the third finger. This patient has rheumatoid arthritis, which may result in a synovitis, as well as rupture of tendons. In the sagittal plane, the T1-weighted fat-saturated image (B) shows thickening of the flexor tendon (rectangle) due to a synovitis stimulated by rheumatoid arthritis. Figure (C) shows a T1-weighted, coronal plane image of a 20-year-old female patient with a diagnosis of rheumatoid arthritis and demonstrates multiple, low signal lesions affecting the carpus. On the fluid-sensitive STIR sequence (D), these lesions, particularly obvious in the lunate, are of high signal and fairly well demarcated.

Nerves

Median nerve

Neural structures can be assessed well with MR imaging. When a patient presents with symptoms and signs of carpal tunnel syndrome, differentiation from proximal neuropathies can be challenging and the MR image may be useful to determine the presence and extent of any local irritation to the median nerve.³² The median nerve should normally be of a slightly grey or higher signal intensity as compared with the surrounding tendons in the carpal tunnel of normal dimension.³¹ In the proximal carpal tunnel, the nerve is slightly flatter than the surrounding tube-like flexor tendons. As it travels more distally through the carpal tunnel, it becomes even flatter in shape.

Carpal tunnel syndrome may arise due to a number of conditions, but is primarily considered a compressive neuropathy.³³ Such compression may occur due to a simple local lesion, such as a ganglion within the carpal tunnel, or from a tenosynovitis of the flexor tendons, causing a decrease in the space that the median nerve occupies within the tunnel.^34–36 Relevant imaging findings from carpal tunnel syndrome may therefore include the presence of tenosynovitis of the flexor tendons, which will appear as areas of increased signal intensity about the tendons on the T2-weighted sequences. The addition of intravenous contrast may enhance a T1 sequence. The nerve may demonstrate an increase in its size and signal intensity on the fluid-sensitive sequences (Figure 10.08). MR imaging is not used routinely in the primary diagnosis of carpal tunnel syndrome,⁶ but is best employed to determine the cause of symptoms and signs in persistent cases or to evaluate scar tissue formation following surgery, which can itself be a cause of median nerve irritation (Figure 10.09).^37,38

Figure 10.08 • T2-weighted, fat-saturation MR imaging of the proximal carpal row in the axial plane, in which the region of the carpal tunnel is diffusely high-signal, particularly around the tendons. Also of note is the high signal intensity and deformation of the median nerve situated within the carpal tunnel (oval). These findings are consistent with carpal tunnel syndrome.

Figure 10.09 • Axial T1-weighted MR imaging of the right wrist of a 41-year-old female who had refractory symptoms following carpal tunnel surgery. The imaging was performed before the second intervention to determine the presence and extent of any scar tissue and to confirm the cause of her continuing symptoms. Thickening and fibrosis is noted about the median nerve (circle) and retraction of the tendons within the carpal tunnel in the volar direction is also seen.

Because of the potential complications of surgical intervention, conservative care is recommended; steroid injections and splinting can often be effective and both manual therapy and acupuncture have shown some benefit to patients.^39–42

Ligaments

Game-keeper’s thumb is an avulsion injury of the base of the proximal phalanx, commonly related to a forced abduction movement in sports such as skiing or from the recoil of a gun (hence the eponymic name) whereby the ulnar collateral ligament is disrupted along with a small fragment of bone from its insertion into the proximal phalanx. This ligament is important for conferring stability to the thumb, and, although basic imaging may be used to demonstrate the bony lesion, MR imaging depicts the bony and soft tissue injury with exquisite detail, which is important in the prognosis and most appropriate clinical management of the patient (Figure 10.10).

Figure 10.10 • Imaging of a patient with severe pain and limitation in the range of movement of the thumb following injury. The plain film radiograph (A) demonstrates a small, bony fragment at the base of the proximal phalanx. Ultrasound of the same region (B) again demonstrates the presence of a region of echo due to the bony fragment (oval); however, MR imaging of the first digit in the coronal plane using a T1-weighted sequence (C) demonstrates not only the bony fragment but also the disruption to the ligamentous complex (rectangle) surrounding this lesion, which is clinically much more significant and which often requires surgical intervention to repair and restore the normal biomechanics to the thumb.

MR imaging may also be used to determine the presence of radiographically occult fractures (Figure 10.11). The scaphoid is the most commonly fractured bone in the wrist, and, if initial radiographs are negative, options may consist of immobilizing the patient and re-radiographing 10 days later, or, if such facilities exist, performing MR imaging to determine the presence of any fracture and also to follow the development of potential complications such as avascular necrosis. This condition can also develop spontaneously in the paediatric lunate (Kienböck’s disease) (Figure 10.12).^44,45

Figure 10.11 • (A) Posteroanterior plain film radiograph of a patient describing wrist pain focused over the anatomical snuff-box. There was a recent history of a fall onto the outstretched hand; these films were taken a few days after the incident. No evidence of a fracture is noted in the carpal bones. (B) MR image of the wrist of the same patient. In this image, a coronal plane, STIR sequence, a large area of increased signal intensity is noted in the distal aspect of the scaphoid due to the presence of a fracture; the exact location is difficult to confirm on this single slice.

Figure 10.12 • MR imaging of the wrist in a patient with a recent history of trauma complaining of pain in the region of the anatomical snuff-box. The T1-weighted sequence (A) clearly demonstrates a region of low signal intensity in the proximal pole of the scaphoid bone. A linear region of low signal intensity is also noted in the waist of the scaphoid. On the T2-weighted sequence (B), a region of increased signal intensity is seen in the distal pole of the scaphoid as well as an area of cortical disruption along the lateral aspect of the scaphoid, owing to the presence of a fracture. The MR imaging confirms the presence of a fracture with the development of avascular necrosis of the proximal pole, a complication of the trauma.

Falls on the outstretched hand (FOOSH) may also affect the ligaments about the wrist, which need to be scrutinized, particularly on the coronal sequence. The ligaments, such as the scapholunate ligament, should be seen as a linear low-signal continuous structure connecting the scaphoid and lunate. In the case of disruption of the ligament, a slightly increased distance may be noted between the scaphoid and lunate (normal range is 2 to 4 mm) as well as disruption of the linear signal, which appears discontinuous or irregular (Figure 10.13).^43,45

Figure 10.13 • Coronal, T1-weighted (A) and T2-weighted (B) MR imaging of a post-traumatic wrist. The patient complained of pain and a sensation of clicking about the lateral aspect of their wrist. The T1-weighted imaging demonstrates a lack of continuity of the scapholunate ligament (ovals) with a possible retraction of the insertion of the triangular fibrocartilage complex insertion onto the ulnar styloid process (arrow). On the T2-weighted sequence, again the discontinuity is noted between the scaphoid and lunate where there should normally be a linear low signal intensity representing the ligament. This finding is due to a tear of the scapholunate ligament, which may cause instability in the wrist.

Lacerating injuries to the hand or wrist may result in damage to soft tissue or bony structures. A commonly sustained injury is laceration of the fingers, whereby the tendons of the fingers may be partially or completely ruptured (Figure 10.14). The patient usually presents with a history of acute trauma, commonly involving a sharp utensil, with clinical deformity of the finger and the inability to perform flexion or extension. Whereas ultrasound may be useful to determine the extent of injury, it is highly operator-dependent.⁴⁶ MR imaging will provide superior information with respect to both bony and soft tissue damage, providing important information regarding the clinical diagnosis and management of the patient.

Figure 10.14 • Sagittal T2-weighted sequence in a patient who had been attacked with a knife and who, shortly after the incident, noted that she was unable to move her finger normally. After the physical examination, MR imaging was ordered. This shows that there is discontinuity of the flexor digitorum profundus tendon, which has been lacerated and retracted to the level of the proximal interphalangeal articulation (rectangle). This lesion will require surgical intervention in order to repair the extent of retraction so as to restore the mechanics of the digit.

Tumours

The majority of neoplasms in the wrist and hand are benign; the most common cause of such growths are ganglia, fibrous-walled masses attached to ligaments, joint capsules and tendon sheaths. More commonly found in females, they only become painful when pressing against adjacent structures; their cause appears to relate to chronic irritation.⁴⁷ MR imaging will reveal ganglia as low intensity structures on T1-weighted imaging; on T2-weighted imaging, the signal intensity is higher though generally diffuse with characteristic thin, low signal lines representing septa that subdivide the internal architecture of the ganglion. The most common differential is the presence of accessory, anomalous muscles, most commonly extensor digitorum manus brevis, found on the dorsum of the wrist medial to the tendon of extensor indices. The characteristic location helps to differentiate it from a ganglion.^29,43

The second commonest soft tissue mass about the wrist is the giant cell tumour of the tendon sheath; a localized form of pigmented villonodular synovitis, characteristically noted on the volar digital surfaces; their differentiation is further helped by their appearance as low signal intensity structures on both T1- and T2-weighted images.⁴³

Arthritis and infection

Infectious and arthritic processes commonly affect the hand and wrist and MR imaging allows for superb contrast of soft tissue and bone marrow changes, showing in exquisite detail changes that remain occult on other imaging modalities. These typical changes have been well detailed in the previous chapters.