MRI Wrist and Hand
MRI of the wrist and hand is the best test for the carpal bones, ligaments, triangular fibrocartilage complex, tendons, nerves, cartilage and synovium. It also shows the small joints of the fingers and thumb, the flexor and extensor tendons and the soft tissues of the hand.
The study uses a 1.5 or 3 tesla scanner with a dedicated wrist or small joint coil. The patient lies prone with the arm overhead or sits with the arm at the side. Prone positioning centres the wrist but is uncomfortable, and a side position improves tolerance in elderly patients.
Slices are 2 to 3 mm thick with a small field of view. The core sequences are coronal and axial proton density or T2-weighted images with fat suppression, coronal T1-weighted images, and sagittal images for the lunate and capitate. Three dimensional isotropic sequences allow reformatting.
The examination takes 20 to 30 minutes.
Contrast is used for synovitis, infection and tumour. Direct MR arthrography (gadolinium injected into the radiocarpal joint, often with the midcarpal and distal radioulnar joints) improves detection of ligament and triangular fibrocartilage tears.
Wrist pain is a common problem after falls, sport and repetitive work. Scaphoid fractures account for about 60% of carpal fractures, and 10 to 20% are not seen on the first radiographs.
MRI has a sensitivity and specificity of about 95 to 100% for occult scaphoid fracture within 24 to 48 hours of injury.
In inflammatory arthritis, MRI shows synovitis, bone marrow oedema and erosions months before they appear on radiographs.
Indications.
- Suspected scaphoid or other carpal fracture with normal radiographs.
- Chronic wrist pain: ligament injury, instability, triangular fibrocartilage tear, ulnar sided pain.
- Osteonecrosis of the scaphoid (after fracture) or the lunate.
- Inflammatory arthritis (rheumatoid arthritis, spondyloarthritis), crystal disease and synovitis.
- Infection of bone, joint, tendon sheath and soft tissue.
- Soft tissue masses (ganglion, giant cell tumour of tendon sheath, lipoma, sarcoma) and bone tumours.
- Tendon disorders: tenosynovitis, tendon tears, and impingement.
- Nerve compression (carpal tunnel, ulnar tunnel) when the cause is unclear.
- Post-operative and post-traumatic assessment, and malunion.
- Hand injuries: collateral ligament injury of the thumb and fingers, pulley injury, and volar plate injury.
Not for typical carpal tunnel syndrome with a clear clinical and electrophysiological picture, or for fractures that are clear on radiographs.
Contraindications and precautions.
- The usual MRI safety screen. Most orthopaedic hardware is safe, but metal causes artefact.
- Gadolinium: renal precautions apply. Intra-articular injection requires sterile technique.
- Pregnancy: non-contrast MRI is acceptable.
- Claustrophobia: the arm overhead position places the head near the bore, and the arm-at-side position is preferred.
- Patients unable to keep the wrist still: sedation is rarely needed.
Preparation and technique.
No preparation is needed. The wrist is placed in neutral position, slightly extended, with the hand flat and the fingers extended. Movement is limited with padding and straps.
Coronal images are aligned along the radial and ulnar styloid, and axial images are taken from the distal radioulnar joint to the metacarpal bases. Fat suppressed sequences show marrow oedema and fluid. Small field images of the finger or thumb use a dedicated coil.
For arthrography, the joint is injected under fluoroscopy or ultrasound with 2 to 3 mL of dilute gadolinium and local anaesthetic, and the scan follows within 30 minutes.
