Table 2.

Summary of Studies Using US, MRI, and CT in Diagnostics of A2 Pulley Injuries

Authors	Year	Imaging Modality	Clinical System	Finger Positioning	Resistance Applied	Diagnostic Criteria	TP Location/Measurement	Sensitivity/Specificity
Cadaver studies
Hauger et al. 15	2000	CT	2 mm slices, 1 mm increments	MCP: full extension PIP: 60° flexion DIP: 10° flexion	500 g weight with traction	Complete tear: 2–5 mm Incomplete tear: 0–3 mm Combined tear: 5–8 mm	Junction of proximal two‐thirds and distal one‐third of the proximal phalanx	NT
		MRI	1.5‐T with a phased array wrist coil	MCP: full extension PIP: 60° flexion DIP: 10° flexion	500 g weight with traction	Complete tear: 2–5 mm Incomplete tear: 0–3 mm Combined tear: 5–8 mm	Junction of proximal two‐thirds and distal one‐third of the proximal phalanx	NT
		US	12 MHz transducer	MCP: full extension PIP: 60° flexion DIP: 10° flexion	500 g weight with traction and simultaneous counter‐pressure at the fingertip	Complete tear: 2–5 mm Incomplete tear: 0–3 mm Combined tear: 5–8 mm	Junction of proximal two‐thirds and distal one‐third of the proximal phalanx	NT
Leeflang & Coert 17	2014	US	Frequency band 20–60 MHz, center frequency 40 MHz transducer	MCP: 15° flexion PIP: 15° flexion DIP: 15° flexion	FDP loaded to 100 N, FDS preloaded to 5 N	Area between flexor tendon and palmar side of proximal phalanx	10 mm distal to MCP; Size of area (mm2) between proximal phalanx and flexor tendon >5 mm	NT
Bayer et al. 28	2015	MRI	1.5 T with a dedicated eight channel orthopedic foot coil	Crimp Grip and Neutral	10 N–1.0 kg weight attached to a pulley system to the FDS and FDP	*Complete tears: 2.29 ± 1.82 mm (crimp grip) 1.10 ± 0.67 mm (neutral)	50% length of the proximal phalanx	.93/1.0 in crimp and .79/.86 in neutral dissection
Schoffl et al. 18	2017	US	14 MHz transducer	MCP: NS PIP: full available flexion DIP: up to 30° flexion	10 N flexor tendons	Complete tear: >1.9 mm	Over A2 pulley	1.0/.94 Dissection
Schoffl et al. 19	2018	US	18 MHz transducer	MCP: NS PIP: 30° flexion DIP: full available flexion	10 N flexor tendons	Complete tear: >2 mm	Middle of proximal phalanx	.94/1.0 Dissection
Clinical studies
Parellada et al. 29	1996	MRI	1.5 T	Finger at full extension and 30–45° flexion a	None	Bowstringing b	NT	NT
Le Viet et al. 34	1996	CT	1.5 mm slices	MCP: NS PIP: flexion DIP: extension	Manual NS c	Bowstringing	NT	NT
Gabl et al. 30	1998	MRI	1.5 T with surface coil	MCP: full extension PIP: 60° flexion DIP: 10° flexion	Manual Subject	Complete tear: Bowstringing from PIP joint to base of proximal phalanx Incomplete tear: Bowstringing less than to base of proximal phalanx	NT	NT
Bodner et al. 35	1999	MRI	1.5 T with surface coil	MCP: NS PIP: 40° flexion DIP: 10° flexion	Manual subject	Complete tear: ≥3 mm extended, ≥5 mm flexed	Midpart of proximal phalanx, at bony attachment of the check rein ligament	1.0/1.0 Surgical visualization d
		US	10 MHz transducer	MCP: NS PIP: 40° flexion DIP: 10° flexion	Manual examiner	Complete tear: ≥3 mm extended, ≥5 mm flexed	Midpart of proximal phalanx, at bony attachment of the check rein ligament	1.0/1.0 Surgical Visualization
Klauser et al. 20	1999	US	10 MHz transducer	MCP: extension PIP: 40° flexion DIP: 10° flexion	Manual NS c	Complete tear: >.3 cm at rest, >.5 cm forced flexion Bowstringing Tenosynovitis Tendon and pulley thickening Tendon gliding Cysts/fibrous tissue Fluid collection	NS	NT
Martinoli et al. 36	2000	MRI	MRI: 2 T with surface coil or a dedicated extremity coil	45° flexion	Manual Examiner	Bowstringing Synovial sheath effusion	At the level of the proximal phalanx/pulley	NT
		US	US: 12–5 MHz and 10–13 MHz transducers	45° flexion	Manual Examiner	Bowstringing Tenosynovitis Thickened hypoechoic pulley	At the level of the proximal phalanx/pulley	NT
Klauser et al. 21	2000	US	13–5 MHz transducer	MCP: extension PIP: 40° flexion DIP: 10° flexion	Manual NS c	Bowstringing Tendon thickening Tendon sheath cyst Fibrous tissue Fluid collection	At the level of the base of the proximal phalanx in the area of the A2 pulley	NT
Klauser et al. 14	2002	US	12 MHz transducer	MCP: extension PIP: 40° flexion DIP: 10° flexion	Manual Examiner	Complete tear: ≥3 mm Incomplete tear: <3 mm Combined tear (A2 + A3): ≥5 mm	15–20 mm from the base of the proximal phalanx where the flexor tendon lies close to the phalanx	.98/1.0 MRI
Schoffl et al. 22	2006	US	10 MHz transducer	Forced flexion and extension	Manual examiner	Complete tear: >2 mm	Middle of the proximal phalanx	NT
Guntern et al. 31	2007	MRI	3 T with a dedicated wrist coil	Flexion and extension a	None	Complete tear: ≥2 mm	Mid‐diaphysis level in sagittal plane	.88/1.0 Clinical exam
Bassemir et al. 23	2015	US	18 MHz transducer	MCP: extension PIP: extension DIP: 30° flexion	500 g weight with custom sling	N/A	Level of proximal‐ to middle‐third of the proximal phalanx	NT
Schneeberger & Schweizer 24	2016	US	17.5 MHz transducer	MCP: extension PIP: 40° flexion DIP: 10° flexion	Manual NS c	Bowstringing	Middle of the proximal phalanx	NT
Reissner et al. 25	2018	US	17 MHz transducer	Resting position	None	Bowstringing	15 mm from the base of the proximal phalanx	NT
Hoff & Greenberg 32	2018	MRI	1.5 T	Crimp grip	Subject grasped glass container	Complete tear: ≥2 mm	Middle of the proximal phalanx	NT
Schellhammer & Vantorre 33	2019	MRI	1.5 T with a dedicated knee coil	6 consecutive finger positions from extension to full flexion	None	Bowstringing	Middle of the proximal phalanx	NT
Iruretagoiena‐Urbieta et al. 26	2020	US	24 MHz transducer	MCP: neutral PIP: 40° flexion DIP: 10° flexion	Manual Examiner	Complete tear: >2 mm	Middle of the proximal phalanx	NT
Scheibler, Janig, & Schweizer 27	2021	US	NS	MCP: NS PIP: NS DIP: NS	Loading of the flexor tendon	NS	Middle of the proximal phalanx	NT

DIP, distal interphalangeal joint; FDP, flexor digitorum profundus; FDS, flexor digitorum superficialis; MCP, metacarpophalangeal joint; N/A, not applicable (not included in study); NS, not stated (not specified in study); NT, not taken; PIP, proximal interphalangeal joint; T, tesla; TP, tendon to phalanx distance.

^a When specific values for finger joints are not included, the information was not provided in the manuscript.

^b Bowstringing = qualitative.

^c Person applying resistance.

^d Gold Standard used *reported as averages.