Ultrasound of the Hand and Wrist: Compartment-Based Protocol

Protocol Objective

Ultrasound of the hand and wrist involves examining superficial tendons, joints, ligaments, nerves, and soft tissues in the area of clinical interest. The AIUM Practice Parameter for the Performance of a Musculoskeletal Ultrasound Examination, 2023 emphasizes that musculoskeletal scanning should be adapted to the clinical question, include comparison with the contralateral side if necessary, and use dynamic maneuvers if they help confirm the diagnosis.

For the wrist area, a compartmental approach is most practical: first the dorsal extensor channels, then the palmar surface with the carpal tunnel and Guyon's canal, followed by joint spaces, ligamentous structures, the hand, and fingers. This order reduces the risk of missing tenosynovitis, tendon rupture, ganglion, compressive neuropathy, or synovitis of small joints.

Equipment and Basic Technique

A high-frequency linear transducer is used, selected to provide maximum resolution of superficial structures with sufficient depth of view. For very superficial tendons and fingers, abundant gel, a pad, or slight compression with the transducer is useful to avoid deforming ganglia, synovial effusions, and small vascular structures.

Longitudinal and transverse scans are mandatory. Tendons are evaluated considering anisotropy: false hypoechogenicity disappears with correction of the insonation angle. Color or power Doppler is applied when active synovitis, tenosynovitis, soft tissue hyperemia, vascular malformation, or post-traumatic complication is suspected. Dynamic scanning is performed for clicks, tendon subluxation, instability, trigger finger, and impingement.

Positioning and Examination Route

The patient places the hand on the table; the wrist is examined in a neutral position, flexion, extension, radial and ulnar deviation as indicated. It is advisable to start with the area of maximum pain, then proceed through the entire standard route. If a local finding is present, it is documented in two orthogonal planes, describing its relation to the tendon, joint, nerve, vessel, or bone.

Minimum route: dorsal surface from radial to ulnar edge, palmar surface from the carpal tunnel to Guyon's canal, distal radioulnar joint, radiocarpal and midcarpal levels, then metacarpophalangeal and interphalangeal joints upon request.

Dorsal Surface: 6 Extensor Compartments

The dorsal protocol is structured from the radial side to the ulnar side. In each channel, evaluate the contour of the extensor retinaculum, thickness and echostructure of tendons, fluid in the synovial sheath, hyperemia, partial or complete rupture, subluxation, bony irregularities, and tenderness during sono-palpation.

For the VI compartment, dynamics are especially important: the extensor carpi ulnaris tendon is evaluated during pronation-supination and ulnar deviation if there is a click or pain along the ulnar edge.

Palmar Surface: Carpal Tunnel

The carpal tunnel is examined in transverse and longitudinal sections from the proximal entrance to the distal exit. Evaluate the median nerve, tendons of the superficial and deep finger flexors, flexor pollicis longus, flexor retinaculum, and canal contents. According to AIUM, it is crucial to describe the nerve structure, its contour, echogenicity, relationship with surrounding tissues, and signs of compression if the study is conducted for neuropathy.

The protocol records: localization of maximum nerve change, flattening or deformation, disruption of fascicular pattern, hyperemia, flexor sheath synovitis, mass, ganglion, postoperative changes. Numerical thresholds for the median nerve area are not provided in the AIUM 2023 document for this protocol, so when using them in a local institution, the measurement method and source of the norm should be specified separately.

Guyon's Canal and Ulnar Edge of the Wrist

Guyon's canal is examined on the palmar-ulnar surface. Identify the ulnar nerve and vascular bundle, hook of the hamate, pisiform bone, and possible causes of compression: ganglion, post-traumatic change, thrombosis or aneurysmal dilation of the ulnar artery, fibrous changes, muscle variant.

For complaints of ulnar pain, additionally evaluate the distal radioulnar joint, the triangular fibrocartilage complex in the accessible part for ultrasound, the VI compartment, the ulnar collateral area of the wrist, and adjacent soft tissues. Ultrasound does not replace MRI evaluation of intra-articular fibrocartilaginous structures but effectively identifies effusion, synovitis, ganglia, and dynamic tendon instability.

Joints and Ligaments

Radiocarpal, midcarpal, and distal radioulnar joints are evaluated for effusion, synovial hypertrophy, erosive changes of accessible cortical surfaces, osteophytes, and intra-articular bodies. Doppler helps distinguish active vascularized synovium from inactive effusion or fibrous tissue.

Dorsal interosseous ligaments, including the scapholunate interval area, are examined in the accessible zone. In trauma, tenderness under the transducer, local effusion, fiber disruption, bony avulsion fragment, and dynamic interval widening, if visualized, are important. Negative ultrasound with strong clinical suspicion of intra-articular tear does not exclude the need for MRI or arthroscopic verification.

Hand and Fingers

At the level of the metacarpophalangeal and interphalangeal joints, examine the extensor apparatus, central slip, lateral bands, sagittal bands, collateral ligaments, volar plates, and flexor tendons. In inflammatory arthropathies, the protocol includes joint spaces and tendon sheaths in grayscale and Doppler mode.

For suspected trigger finger, perform dynamic flexion and extension, evaluate the flexor tendon, sheath, and pulley area. In finger trauma, it is important to indicate the level of injury, retraction of visible tendon ends, presence of hematoma, foreign body, bony fragment, and the defect's relation to the area of pain.

What to Include in the Report

• Side, area of examination, and clinical question.
• Which compartments and structures were examined.
• Localization of the finding: surface, compartment, joint or finger level.
• Tendon echostructure, presence of fluid, synovium, hyperemia, rupture, or subluxation.
• Condition of the median and ulnar nerves in neuropathic inquiry.
• Presence of effusion, synovitis, erosive changes, ganglion, mass, or foreign body.
• Results of dynamic tests and comparison with the opposite side if performed.

Common Mistakes

The main mistake is describing only the site of pain without systematically covering adjacent compartments. This can lead to missing a combination of ganglion with tenosynovitis, pathology of the VI compartment with ulnar pain, or flexor synovitis with carpal tunnel symptoms.

The second mistake is mistaking anisotropy for tendinopathy. Any hypoechoic area in the tendon should be rechecked by changing the transducer angle and using a longitudinal scan. The third mistake is not performing dynamics when there is a complaint of clicking: tendon subluxation, impingement, and trigger mechanism often become apparent only in motion.