Ultrasound of the hand and wrist

1. In meta-analysis, a median nerve cross-sectional area of at least 9 mm² at the carpal tunnel inlet was the most accurate single ultrasound criterion for carpal tunnel syndrome, with sensitivity and specificity both above 80%.

True

Tai's meta-analysis of 28 studies (3995 wrists) found a larger median nerve cross-sectional area at the tunnel inlet and greater flattening at the level of the hamate in affected wrists. An inlet area of 9 mm² or more was the strongest single criterion (diagnostic odds ratio 40.4), with a sensitivity of 87.3% and a specificity of 83.3%.

• Tai TW, Wu CY, Su FC, Chern TC, Jou IM. Ultrasonography for diagnosing carpal tunnel syndrome: a meta-analysis of diagnostic test accuracy. Ultrasound Med Biol. 2012;38(7):1121-8. PMID 22542258

2. In rheumatoid arthritis, ultrasound detects more erosions of the metacarpophalangeal joints than conventional radiography, particularly in early disease.

True

Wakefield compared sonography and radiography of the metacarpophalangeal joints in 100 patients. Sonography found 127 definite erosions in 56 patients against 32 erosions in 17 patients on radiographs, and in early disease it detected 6.5-fold more erosions. Sonographic erosions not visible on radiographs corresponded to bone abnormalities on magnetic resonance imaging (MRI).

• Wakefield RJ, Gibbon WW, Conaghan PG, O'Connor P, McGonagle D, Pease C, et al.. The value of sonography in the detection of bone erosions in patients with rheumatoid arthritis: a comparison with conventional radiography. Arthritis Rheum. 2000;43(12):2762-70. PMID 11145034

3. When the Carpal Tunnel Syndrome 6 (CTS-6) clinical diagnostic score is the reference standard, ultrasound is less specific than electrodiagnostic testing for carpal tunnel syndrome.

False

In Fowler's study of 85 patients, ultrasound (cross-sectional area of 10 mm² or more just proximal to the pisiform) had a sensitivity of 89% and a specificity of 90%, against 89% and 80% for electrodiagnostic testing. The authors concluded that ultrasound can confirm the diagnosis with better specificity and equal sensitivity in patients with a positive CTS-6, although it does not replace electrodiagnosis in complicated or unclear cases.

• Fowler JR, Munsch M, Tosti R, Hagberg WC, Imbriglia JE. Comparison of ultrasound and electrodiagnostic testing for diagnosis of carpal tunnel syndrome: study using a validated clinical tool as the reference standard. J Bone Joint Surg Am. 2014;96(17):e148. PMID 25187592

4. Dynamic ultrasound can diagnose finger pulley rupture by showing an increased distance between the flexor tendon and the phalanx during forced flexion.

True

Klauser examined 64 extreme rock climbers (climbing levels 8–11) with a 12-MHz transducer, measuring the tendon–phalanx distance at the A2 and A4 pulleys in extension and forced flexion, with MRI as comparison and surgical correlation in seven cases. A distance greater than 1.0 mm was taken as positive, and dynamic ultrasound had a sensitivity of 98% and a specificity of 100% for pulley injuries.

• Klauser A, Frauscher F, Bodner G, Halpern EJ, Schocke MF, Springer P, et al.. Finger pulley injuries in extreme rock climbers: depiction with dynamic US. Radiology. 2002;222(3):755-61. PMID 11867797

5. In pooled studies of radiographically occult scaphoid fractures, ultrasound had a sensitivity below 50%.

False

Kwee's systematic review of 7 studies (314 patients), most using cortical disruption as a criterion, found a pooled sensitivity of 85.6% and specificity of 83.3%. The authors suggested that ultrasound may be used when computed tomography (CT) and MRI are not readily available.

• Kwee RM, Kwee TC. Ultrasound for diagnosing radiographically occult scaphoid fracture. Skeletal Radiol. 2018;47(9):1205-1212. PMID 29619506