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Extensor Mechanism of the Fingers: MR Imaging–Anatomic Correlation¹

¹ From the Department of Radiology, Diagnosis Médica, C/Corcega 345, 08037 Barcelona, Spain (J.A.C., X.A., J.M.M.); the Department of Human Anatomy and Embryology, School of Medicine, University of Barcelona, Spain (P.G., O.F.); and the Service of Orthopedic Surgery, Clínica FREMAP, Barcelona, Spain (M.E.). Presented as an education exhibit at the 2001 RSNA scientific assembly. Received April 15, 2002; revision requested May 29 and received October 3; accepted November 8. Address correspondence to J.A.C. (e-mail: clavero@creu-blanca.es).

View larger version (52K): [in a new window]   Figure 1a.  Anatomy of the extensor apparatus. (a) Drawing of the hand (dorsal view) shows the main anatomic structures. 1 = extensor digitorum muscle, 2 = extensor digiti minimi muscle, 3 = extensor carpi ulnaris muscle, 4 = abductor pollicis longus muscle, 5 = extensor pollicis brevis muscle, 6 = extensor pollicis longus tendon, 7 = extensor indicis tendon, 8 = extensor carpi radialis longus muscle, 9 = extensor carpi radialis brevis muscle, 10 = intertendinous connections, 11 = extensor retinaculum, 12 = first dorsal interosseous muscle, 13 = adductor pollicis tendon, 14 = abductor digiti minimi muscle, 15 = sagittal band, 16 = central slip, 17 = lateral conjoined tendon, 18 = medial conjoined tendon, 19 = terminal tendon, 20 = triangular ligament. (b) Drawing of the hand (dorsal view) shows the zones of the extensor system according to the Verdan classification (10). This classification was developed to categorize the lesion findings. I = DIP joint, II = middle phalanx, III = PIP joint, IV = proximal phalanx, V = MCP joint, VI = dorsum of hand, VII = wrist extensor compartment, VIII = extrinsic extensor muscles.

View larger version (40K): [in a new window]   Figure 1b.  Anatomy of the extensor apparatus. (a) Drawing of the hand (dorsal view) shows the main anatomic structures. 1 = extensor digitorum muscle, 2 = extensor digiti minimi muscle, 3 = extensor carpi ulnaris muscle, 4 = abductor pollicis longus muscle, 5 = extensor pollicis brevis muscle, 6 = extensor pollicis longus tendon, 7 = extensor indicis tendon, 8 = extensor carpi radialis longus muscle, 9 = extensor carpi radialis brevis muscle, 10 = intertendinous connections, 11 = extensor retinaculum, 12 = first dorsal interosseous muscle, 13 = adductor pollicis tendon, 14 = abductor digiti minimi muscle, 15 = sagittal band, 16 = central slip, 17 = lateral conjoined tendon, 18 = medial conjoined tendon, 19 = terminal tendon, 20 = triangular ligament. (b) Drawing of the hand (dorsal view) shows the zones of the extensor system according to the Verdan classification (10). This classification was developed to categorize the lesion findings. I = DIP joint, II = middle phalanx, III = PIP joint, IV = proximal phalanx, V = MCP joint, VI = dorsum of hand, VII = wrist extensor compartment, VIII = extrinsic extensor muscles.

View larger version (39K): [in a new window]   Figure 2a.  Extensor muscles. Drawings of the forearm show the superficial (a) and deep (b) layers. 1 = extensor carpi radialis longus, 2 = extensor carpi radialis brevis, 3 = extensor digitorum, 4 = extensor digiti minimi, 5 = extensor carpi ulnaris, 6 = supinator, 7 = abductor pollicis longus, 8 = extensor pollicis brevis, 9 = extensor pollicis longus, 10 = extensor indicis, 11 = first intersection, 12 = second intersection.

View larger version (36K): [in a new window]   Figure 2b.  Extensor muscles. Drawings of the forearm show the superficial (a) and deep (b) layers. 1 = extensor carpi radialis longus, 2 = extensor carpi radialis brevis, 3 = extensor digitorum, 4 = extensor digiti minimi, 5 = extensor carpi ulnaris, 6 = supinator, 7 = abductor pollicis longus, 8 = extensor pollicis brevis, 9 = extensor pollicis longus, 10 = extensor indicis, 11 = first intersection, 12 = second intersection.

View larger version (106K): [in a new window]   Figure 3a.  Axial anatomic slice (a) and axial T1-weighted MR image (b) obtained at the proximal one-third of the forearm show the extensor muscles. 1 = extensor carpi radialis longus and brevis, 2 = extensor digitorum, 3 = extensor digiti minimi, 4 = extensor carpi ulnaris, 5 = abductor pollicis longus, 6 = extensor pollicis brevis, 7 = extensor pollicis longus, 8 = extensor indicis, 9 = brachioradialis.

View larger version (110K): [in a new window]   Figure 3b.  Axial anatomic slice (a) and axial T1-weighted MR image (b) obtained at the proximal one-third of the forearm show the extensor muscles. 1 = extensor carpi radialis longus and brevis, 2 = extensor digitorum, 3 = extensor digiti minimi, 4 = extensor carpi ulnaris, 5 = abductor pollicis longus, 6 = extensor pollicis brevis, 7 = extensor pollicis longus, 8 = extensor indicis, 9 = brachioradialis.

View larger version (96K): [in a new window]   Figure 4a.  Axial anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the distal one-third of the forearm and (c, d) sequential axial T1-weighted MR images obtained at the first intersection show the extensor tendons. The first intersection is produced when the abductor pollicis longus and extensor pollicis brevis (1) cross over the extensor carpi radialis longus (2) and extensor carpi radialis brevis (3). 4 = extensor pollicis longus, 5 = extensor indicis, 6 = extensor digitorum, 7 = extensor digiti minimi, 8 = extensor carpi ulnaris.

View larger version (124K): [in a new window]   Figure 4b.  Axial anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the distal one-third of the forearm and (c, d) sequential axial T1-weighted MR images obtained at the first intersection show the extensor tendons. The first intersection is produced when the abductor pollicis longus and extensor pollicis brevis (1) cross over the extensor carpi radialis longus (2) and extensor carpi radialis brevis (3). 4 = extensor pollicis longus, 5 = extensor indicis, 6 = extensor digitorum, 7 = extensor digiti minimi, 8 = extensor carpi ulnaris.

View larger version (117K): [in a new window]   Figure 4c.  Axial anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the distal one-third of the forearm and (c, d) sequential axial T1-weighted MR images obtained at the first intersection show the extensor tendons. The first intersection is produced when the abductor pollicis longus and extensor pollicis brevis (1) cross over the extensor carpi radialis longus (2) and extensor carpi radialis brevis (3). 4 = extensor pollicis longus, 5 = extensor indicis, 6 = extensor digitorum, 7 = extensor digiti minimi, 8 = extensor carpi ulnaris.

View larger version (105K): [in a new window]   Figure 4d.  Axial anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the distal one-third of the forearm and (c, d) sequential axial T1-weighted MR images obtained at the first intersection show the extensor tendons. The first intersection is produced when the abductor pollicis longus and extensor pollicis brevis (1) cross over the extensor carpi radialis longus (2) and extensor carpi radialis brevis (3). 4 = extensor pollicis longus, 5 = extensor indicis, 6 = extensor digitorum, 7 = extensor digiti minimi, 8 = extensor carpi ulnaris.

View larger version (93K): [in a new window]   Figure 5a.  Axial anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the proximal wrist show the extensor tendons inside the dorsal compartments (1st-6th). The tendons are fixed in the compartments by the extensor retinaculum, which is divided into a superficial part (arrowheads) and a deep part (arrow). The Lister tubercle (*) separates the second and third compartments.

View larger version (116K): [in a new window]   Figure 5b.  Axial anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the proximal wrist show the extensor tendons inside the dorsal compartments (1st-6th). The tendons are fixed in the compartments by the extensor retinaculum, which is divided into a superficial part (arrowheads) and a deep part (arrow). The Lister tubercle (*) separates the second and third compartments.

View larger version (95K): [in a new window]   Figure 6a.  (a, b) Axial anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the intercarpal joints show the second intersection. This intersection is produced when the extensor pollicis longus tendon (3) crosses over the extensor carpi radialis longus (1) and brevis (2) tendons. The extensor carpi radialis longus tendon may be divided into two or more slips (arrowheads). (c) Axial anatomic slice (close-up view) shows the second intersection. 1 and 1' = extensor carpi radialis longus tendons, 2 = extensor carpi radialis brevis tendon, 3 = extensor pollicis longus tendon.

View larger version (114K): [in a new window]   Figure 6b.  (a, b) Axial anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the intercarpal joints show the second intersection. This intersection is produced when the extensor pollicis longus tendon (3) crosses over the extensor carpi radialis longus (1) and brevis (2) tendons. The extensor carpi radialis longus tendon may be divided into two or more slips (arrowheads). (c) Axial anatomic slice (close-up view) shows the second intersection. 1 and 1' = extensor carpi radialis longus tendons, 2 = extensor carpi radialis brevis tendon, 3 = extensor pollicis longus tendon.

View larger version (93K): [in a new window]   Figure 6c.  (a, b) Axial anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the intercarpal joints show the second intersection. This intersection is produced when the extensor pollicis longus tendon (3) crosses over the extensor carpi radialis longus (1) and brevis (2) tendons. The extensor carpi radialis longus tendon may be divided into two or more slips (arrowheads). (c) Axial anatomic slice (close-up view) shows the second intersection. 1 and 1' = extensor carpi radialis longus tendons, 2 = extensor carpi radialis brevis tendon, 3 = extensor pollicis longus tendon.

View larger version (95K): [in a new window]   Figure 7a.  (7) Axial anatomic slice (a) and corresponding sequential T1-weighted MR images (b) obtained at the distal radioulnar joint show the double tendon of the extensor digiti minimi (arrow).

View larger version (53K): [in a new window]   Figure 7b.  (7) Axial anatomic slice (a) and corresponding sequential T1-weighted MR images (b) obtained at the distal radioulnar joint show the double tendon of the extensor digiti minimi (arrow).

View larger version (60K): [in a new window]   Figure 8a.  Axial anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the dorsum of the hand show the extensor digitorum tendons (arrowheads) and extensor digiti minimi tendons (arrow), which are arranged on the same level. Note the difficulty of identifying the tendon for each finger owing to tendon multiplicity and variability.

View larger version (90K): [in a new window]   Figure 8b.  Axial anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the dorsum of the hand show the extensor digitorum tendons (arrowheads) and extensor digiti minimi tendons (arrow), which are arranged on the same level. Note the difficulty of identifying the tendon for each finger owing to tendon multiplicity and variability.

View larger version (69K): [in a new window]   Figure 9a.  Conventional (a) and transilluminated (b) anatomic specimens (dorsal view) show the extensor tendons of the dorsum of the hand (removed from their location). Note the intertendinous connections (arrowheads). 1 = extensor digitorum tendon for the index finger, 2 = extensor digitorum tendon for the middle finger, 3 = extensor digitorum tendon for the ring finger, 4 = extensor digiti minimi tendon.

View larger version (58K): [in a new window]   Figure 9b.  Conventional (a) and transilluminated (b) anatomic specimens (dorsal view) show the extensor tendons of the dorsum of the hand (removed from their location). Note the intertendinous connections (arrowheads). 1 = extensor digitorum tendon for the index finger, 2 = extensor digitorum tendon for the middle finger, 3 = extensor digitorum tendon for the ring finger, 4 = extensor digiti minimi tendon.

View larger version (61K): [in a new window]   Figure 10a.  (a, b) Axial anatomic slice (a) and corresponding T1-weighted MR image (b), obtained at the distal dorsum of the hand, show the C-type intertendinous connections (arrow) to the extensor digiti minimi (arrowhead). (c) Sequential axial T1-weighted MR images show the direction of the C-type intertendinous connections (arrow) from the extensor digitorum for the fourth finger to the extensor digiti minimi.

View larger version (92K): [in a new window]   Figure 10b.  (a, b) Axial anatomic slice (a) and corresponding T1-weighted MR image (b), obtained at the distal dorsum of the hand, show the C-type intertendinous connections (arrow) to the extensor digiti minimi (arrowhead). (c) Sequential axial T1-weighted MR images show the direction of the C-type intertendinous connections (arrow) from the extensor digitorum for the fourth finger to the extensor digiti minimi.

View larger version (156K): [in a new window]   Figure 10c.  (a, b) Axial anatomic slice (a) and corresponding T1-weighted MR image (b), obtained at the distal dorsum of the hand, show the C-type intertendinous connections (arrow) to the extensor digiti minimi (arrowhead). (c) Sequential axial T1-weighted MR images show the direction of the C-type intertendinous connections (arrow) from the extensor digitorum for the fourth finger to the extensor digiti minimi.

View larger version (28K): [in a new window]   Figure 11a.  Drawing (a) and transilluminated anatomic specimen (b) (dorsal view) show the extensor apparatus of the index finger (removed from its location). 1 = extensor digitorum tendon, 2 = interosseous muscle, 2' = lumbrical muscle, 3 = sagittal band, 4 = medial slip, 5 = central slip, 6 = lateral slip, 7 = medial conjoined tendon, 8 = lateral conjoined tendon, 9 = triangular ligament, 10 = terminal tendon, 11 = transverse fibers, 12 = oblique fibers, 13 = retinacular ligament.

View larger version (51K): [in a new window]   Figure 11b.  Drawing (a) and transilluminated anatomic specimen (b) (dorsal view) show the extensor apparatus of the index finger (removed from its location). 1 = extensor digitorum tendon, 2 = interosseous muscle, 2' = lumbrical muscle, 3 = sagittal band, 4 = medial slip, 5 = central slip, 6 = lateral slip, 7 = medial conjoined tendon, 8 = lateral conjoined tendon, 9 = triangular ligament, 10 = terminal tendon, 11 = transverse fibers, 12 = oblique fibers, 13 = retinacular ligament.

View larger version (55K): [in a new window]   Figure 12a.  Axial anatomic slice (a) and corresponding fat-suppressed proton-density-weighted MR image (b) obtained at the MCP joint show the circumferential distribution of the dorsal apparatus over the dorsum of the fingers. Arrows = sagittal band.

View larger version (84K): [in a new window]   Figure 12b.  Axial anatomic slice (a) and corresponding fat-suppressed proton-density-weighted MR image (b) obtained at the MCP joint show the circumferential distribution of the dorsal apparatus over the dorsum of the fingers. Arrows = sagittal band.

View larger version (68K): [in a new window]   Figure 13a.  (a, b) Axial anatomic slice (a) and corresponding fat-suppressed proton-density-weighted MR image (b) obtained at the MCP joint show the sagittal bands (arrows), which extend from the extensor digitorum tendon to the palmar plate. (c, d) Axial anatomic slice (close-up view) (c) and corresponding T1-weighted MR image (d) show the sagittal band (arrow). 1 = extensor digitorum tendon, 2 = palmar plate, 3 = flexor tendon sheath, 3' = flexor tendon, 4 = interosseous muscle, 5 = lumbrical muscle, III = third metacarpal bone, * = deep transverse metacarpal ligament. Note that the interosseous muscle is dorsal to the deep transverse metacarpal ligament and the lumbrical muscle is palmar to the ligament.

View larger version (93K): [in a new window]   Figure 13b.  (a, b) Axial anatomic slice (a) and corresponding fat-suppressed proton-density-weighted MR image (b) obtained at the MCP joint show the sagittal bands (arrows), which extend from the extensor digitorum tendon to the palmar plate. (c, d) Axial anatomic slice (close-up view) (c) and corresponding T1-weighted MR image (d) show the sagittal band (arrow). 1 = extensor digitorum tendon, 2 = palmar plate, 3 = flexor tendon sheath, 3' = flexor tendon, 4 = interosseous muscle, 5 = lumbrical muscle, III = third metacarpal bone, * = deep transverse metacarpal ligament. Note that the interosseous muscle is dorsal to the deep transverse metacarpal ligament and the lumbrical muscle is palmar to the ligament.

View larger version (111K): [in a new window]   Figure 13c.  (a, b) Axial anatomic slice (a) and corresponding fat-suppressed proton-density-weighted MR image (b) obtained at the MCP joint show the sagittal bands (arrows), which extend from the extensor digitorum tendon to the palmar plate. (c, d) Axial anatomic slice (close-up view) (c) and corresponding T1-weighted MR image (d) show the sagittal band (arrow). 1 = extensor digitorum tendon, 2 = palmar plate, 3 = flexor tendon sheath, 3' = flexor tendon, 4 = interosseous muscle, 5 = lumbrical muscle, III = third metacarpal bone, * = deep transverse metacarpal ligament. Note that the interosseous muscle is dorsal to the deep transverse metacarpal ligament and the lumbrical muscle is palmar to the ligament.

View larger version (115K): [in a new window]   Figure 13d.  (a, b) Axial anatomic slice (a) and corresponding fat-suppressed proton-density-weighted MR image (b) obtained at the MCP joint show the sagittal bands (arrows), which extend from the extensor digitorum tendon to the palmar plate. (c, d) Axial anatomic slice (close-up view) (c) and corresponding T1-weighted MR image (d) show the sagittal band (arrow). 1 = extensor digitorum tendon, 2 = palmar plate, 3 = flexor tendon sheath, 3' = flexor tendon, 4 = interosseous muscle, 5 = lumbrical muscle, III = third metacarpal bone, * = deep transverse metacarpal ligament. Note that the interosseous muscle is dorsal to the deep transverse metacarpal ligament and the lumbrical muscle is palmar to the ligament.

View larger version (71K): [in a new window]   Figure 14.  Anatomic slice (medial view) shows the MCP joint level of the third finger. In this area, the extensor digitorum tendon (1) receives the intrinsic contribution of the interosseous muscle (2). This contribution consists of the transverse fibers (3) and oblique fibers (4). 5 = deep transverse metacarpal ligament, 6 = sagittal band.

View larger version (47K): [in a new window]   Figure 15.  Drawings show the locations and insertions of the different interosseous muscles: the first palmar (1), second palmar (2), third palmar (3), first dorsal (4), second dorsal (5), third dorsal (6), and fourth dorsal (7). 8 = abductor digiti minimi muscle.

View larger version (59K): [in a new window]   Figure 16a.  Axial anatomic slice (a) and axial T1-weighted MR image (b) obtained at a near level along the dorsum of the hand show the interosseous muscles (1), which are located in the intermetacarpal spaces. The lumbrical muscles (2) are located on the radial sides of the flexor digitorum profundus tendons. 3 = abductor digiti minimi, 4 = adductor pollicis.

View larger version (89K): [in a new window]   Figure 16b.  Axial anatomic slice (a) and axial T1-weighted MR image (b) obtained at a near level along the dorsum of the hand show the interosseous muscles (1), which are located in the intermetacarpal spaces. The lumbrical muscles (2) are located on the radial sides of the flexor digitorum profundus tendons. 3 = abductor digiti minimi, 4 = adductor pollicis.

View larger version (54K): [in a new window]   Figure 17a.  Axial anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the proximal phalanx show a dorsal condensation of fibers (arrows), which corresponds to the extensor digitorum tendon, and lateral and medial fibers (arrowheads), which correspond to the intrinsic contribution to the extensor apparatus by the interosseous and lumbrical tendons.

View larger version (84K): [in a new window]   Figure 17b.  Axial anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the proximal phalanx show a dorsal condensation of fibers (arrows), which corresponds to the extensor digitorum tendon, and lateral and medial fibers (arrowheads), which correspond to the intrinsic contribution to the extensor apparatus by the interosseous and lumbrical tendons.

View larger version (98K): [in a new window]   Figure 18a.  (a, b) Sagittal T1-weighted MR image (a) and corresponding anatomic slice (b) obtained at the PIP joint show the insertion of the central slip (arrow) on the base of the middle phalanx. (c) Axial T1-weighted MR image obtained at the head of the proximal phalanx shows the relationship between the central slip (arrow) and the medial and lateral slips (arrowheads).

View larger version (69K): [in a new window]   Figure 18b.  (a, b) Sagittal T1-weighted MR image (a) and corresponding anatomic slice (b) obtained at the PIP joint show the insertion of the central slip (arrow) on the base of the middle phalanx. (c) Axial T1-weighted MR image obtained at the head of the proximal phalanx shows the relationship between the central slip (arrow) and the medial and lateral slips (arrowheads).

View larger version (134K): [in a new window]   Figure 18c.  (a, b) Sagittal T1-weighted MR image (a) and corresponding anatomic slice (b) obtained at the PIP joint show the insertion of the central slip (arrow) on the base of the middle phalanx. (c) Axial T1-weighted MR image obtained at the head of the proximal phalanx shows the relationship between the central slip (arrow) and the medial and lateral slips (arrowheads).

View larger version (130K): [in a new window]   Figure 19.  Axial T1-weighted MR image obtained at the PIP joint of the third finger shows the transverse retinacular ligament (arrows), which fixes the conjoined tendons to the C1 pulley.

View larger version (96K): [in a new window]   Figure 20a.  Axial T1-weighted MR images obtained at the base (a) and diaphysis (b) of the middle phalanx show the conjoined tendons (black arrows), which are located in the dorsolateral and dorsomedial parts of the phalanx. The triangular ligament (white arrows) links the conjoined tendons in the middle and distal parts of the phalanx.

View larger version (97K): [in a new window]   Figure 20b.  Axial T1-weighted MR images obtained at the base (a) and diaphysis (b) of the middle phalanx show the conjoined tendons (black arrows), which are located in the dorsolateral and dorsomedial parts of the phalanx. The triangular ligament (white arrows) links the conjoined tendons in the middle and distal parts of the phalanx.

View larger version (57K): [in a new window]   Figure 21a.  Sagittal anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the DIP joint show the insertion of the terminal tendon (arrow) on the base of the distal phalanx.

View larger version (67K): [in a new window]   Figure 21b.  Sagittal anatomic slice (a) and corresponding T1-weighted MR image (b) obtained at the DIP joint show the insertion of the terminal tendon (arrow) on the base of the distal phalanx.

View larger version (22K): [in a new window]   Figure 22a.  Drawings show the sling mechanism of extension of the MCP joint. (a) In a neutral position, the sagittal band is relaxed. (b) In the hyperextension position, the sagittal band is tensed, restricting the proximal excursion of the extensor tendon (arrows).

View larger version (24K): [in a new window]   Figure 22b.  Drawings show the sling mechanism of extension of the MCP joint. (a) In a neutral position, the sagittal band is relaxed. (b) In the hyperextension position, the sagittal band is tensed, restricting the proximal excursion of the extensor tendon (arrows).

View larger version (76K): [in a new window]   Figure 23.  Rupture of the terminal tendon in a 21-year-old basketball player. The subacute rupture was secondary to a closed injury. Sagittal T1-weighted MR image shows discontinuity of the terminal tendon (arrow) at its insertion on the base of the distal phalanx.

View larger version (53K): [in a new window]   Figure 24a.  Complete rupture of the central slip secondary to a closed injury in a 28-year-old man. Sagittal T1-weighted (a) and axial T2-weighted (b) MR images show disruption of the central slip at its insertion on the base of the middle phalanx (arrow). A classic boutonnière deformity with flexion of the PIP joint and extension of the DIP joint is seen (arrowheads).

View larger version (81K): [in a new window]   Figure 24b.  Complete rupture of the central slip secondary to a closed injury in a 28-year-old man. Sagittal T1-weighted (a) and axial T2-weighted (b) MR images show disruption of the central slip at its insertion on the base of the middle phalanx (arrow). A classic boutonnière deformity with flexion of the PIP joint and extension of the DIP joint is seen (arrowheads).

View larger version (81K): [in a new window]   Figure 25a.  Radial subluxation of the extensor digitorum tendon at the MCP joint. Axial T1-weighted (a) and T2-weighted (b) MR images show a complete laceration of the ulnar sagittal band (white arrow) with secondary radial subluxation of the extensor digitorum tendon (arrowhead) at the MCP joint. Note the normal radial sagittal band (black arrow).

View larger version (84K): [in a new window]   Figure 25b.  Radial subluxation of the extensor digitorum tendon at the MCP joint. Axial T1-weighted (a) and T2-weighted (b) MR images show a complete laceration of the ulnar sagittal band (white arrow) with secondary radial subluxation of the extensor digitorum tendon (arrowhead) at the MCP joint. Note the normal radial sagittal band (black arrow).

View larger version (100K): [in a new window]   Figure 26.  de Quervain tenosynovitis. Axial T1-weighted MR image shows increased thickness of the abductor pollicis longus and extensor pollicis brevis tendons (arrows) and increased intratendinous signal intensity. Also note the enlarged synovial sheath (arrowhead).

View larger version (125K): [in a new window]   Figure 27.  Intersection syndrome in a 25-year-old male weight lifter. Axial T2-weighted MR image shows hyperintense fluid around the radial extensors within the tendon sheath (long arrows). Note the extensor pollicis brevis tendon (arrowhead) crossing over the radial extensor tendons. Discrete fluid is also seen within the tendon sheath for the extensor pollicis longus (short arrow).