Keywords
cine-mode MRI - triangular fibrocartilage complex - radioulnar deviation - changes
in shape
The triangular fibrocartilage complex (TFCC) plays an important role in the stability
and mobility of the ulnar side wrist.[1]
[2] Patient with TFCC tear usually claims ulnar-sided wrist pain, click, instability
of the distal radioulnar joint (DRUJ), decrease of power grip, and loss of range of
wrist and forearm motion. Clinically, the ulnocarpal stress test is widely used for
evaluation of TFCC tear, in which the wrist is forced ulnar deviated simultaneously
with the forearm forced pronated or supinated.[3] Patient often claims pain only with forced ulnar deviation. As the TFCC is a soft
tissue insertion between the radius, ulna, and carpal bones, changes in its shape
should occur during radioulnar deviation.[4] When the TFCC is torn, positional changes also may induce changes in strains around
the TFCC, which may induce pain.
Several biomechanical studies have described changes in the shape of the TFCC during
rotation.[5]
[6]
[7]
[8] Shape of the triangular fibrocartilage (TFC) does not demonstrate obvious changes
during forearm rotation in vitro.[8] One study attempted to demonstrate the dynamic changes of the TFCC during forearm
rotation in vivo,[4] in which very small changes in the shape of the TFC were recognized with the exception
of thinning of the TFC in coronal plane of pronation. However, dynamic changes of
the TFCC during radial–ulnar deviation were uncertain, especially in vivo.
Magnetic resonance imaging (MRI) is a useful diagnostic tool for delineation of the
TFCC.[9] High-resolution and fat suppression MRI can demonstrate the TFCC well.[9]
[10]
[11] Recent technology in MRI achieved faster imaging with precise delineation that made
cine-mode MRI possible. Cine MRI may provide further information on joint motion and
changes in shape or length of the soft tissues.[12]
[13]
In this study, using custom positioning device and cine-mode MRI, changes in the shape
of the TFCC during radioulnar deviation plane were studied in healthy volunteers and
in patients with TFCC tear and ulnar styloid nonunion to reveal how and what kind
of changes in shape occurred in the normal and injured TFCC.
Subjects and Methods
Ten right wrists of normal healthy volunteer with a mean age of 23.5 years (range:
23–25), 5 wrists with isolated TFCC tears with a mean age of 32 years (range: 23–46;
3 right and 2 left), and 5 wrists with nonunion of the ulnar styloid process with
a mean age of 22 years (range: 18–27; 4 right and 1 left) were studied. The institutional
ethical board approved this study. Ulnar variance of the volunteers and patients ranged
within ± 1 mm. Patients of isolated TFCC tear were diagnosed by positive physical
examination, arthrogram, “static” fat suppression T1-weighted MRI, and T2*-weighted
MRI. Two patients had radial to central slit tear in the fibrocartilaginous disc that
was described as class 1A tear in the Palmer's classification and the other three
had the horizontal type (intraregional fibrocartilage) tear in the TFCC, which was
not described in the Palmer classification.[14] Additional detachment of the TFCC at the ulnar fovea origin was seen in two of five
ulnar styloid nonunion patients. Three patients with isolated horizontal TFCC tear
and four patients with ulnar styloid nonunion demonstrated moderate to severe instability
of the DRUJ, click, and slacking of the wrist. These diagnoses were confirmed subsequently
by arthroscopy at the time of repair surgery.
A 1.0T superconductive MRI (Magnex 1.0α, Shimadzu Corporation, Kyoto, Japan) with
surface coil (round type, 5 cm of diameter) was used for MR acquisition. The wrist
was fixed in a custom acrylic device ([Fig. 1]), which could be set every 5 degree of radial and ulnar deviation using ratchet
gear, and did not allow any changes in the flexion–extension angle of the wrist against
the motion plane. The examination was started from 15 degrees of radial deviation
to 25 degrees of ulnar deviation with 5 degrees interval. Three or four coronal images
at nine radial–ulnar deviation positions (every 5 degree) were obtained. Three pulse
sequences of fast spin echo (SE) T1-weighted (repetition time [TR] = 150 ms, echo
time [TE] = 18 ms), fast SE T2-weighted (TR = 3,000 ms, TE = 125 ms), and fat-suppression
T1-weighted images (TR = 200 ms, TE = 18 ms) were used. Matrix size of 256 × 256,
16 cm field of view, 2 number of excitation, 1 mm slice thickness, and 1 mm slice
gap were used. Acquisition time was 8 to 10 seconds for 1 position, thus 90 seconds
for total acquisition. The images were recorded in close-loop video format from cine-mode
display, which was programmed in the MR system.
Fig. 1 All acrylic positioning device which allows 15 degrees radial deviation and 25 degrees
ulnar deviation without any positional changes on flexion–extension.
Three pulse sequences, spin echo T1-weighted image, fast spin echo T2-weighted image,
and fat suppression T1 weighted image, were compared to confirm which pulse sequences
delineated the TFCC best in health volunteers. Then the cine-mode MR was assembled
in MPEG format files, and transferred to personal computer for observation. Details
of changes in the shape of the TFCC were analyzed in plain films of each healthy volunteer
and patient as well.
Results
Cine MRI of the Intact TFCC in Healthy Volunteers
The TFCC was delineated as a low-intensity structure in all pulse sequences. Because
of its contrast with high-signal intensity of fat in the bone marrow, fat-suppression
T1 MRI is the best for TFCC delineation ([Fig. 2]).
Fig. 2 Magnetic resonance delineation of the wrist. (A) Fast spin echo T2-weighted image. (B) Spin echo T1-weighted image. (C) Fat suppression T1-weighted image.
In normal wrists, cine-mode coronal MRI demonstrated the scaphoid extended with ulnar
deviation, and flexed with radial deviation. The lunate rotated approximately 22 degrees
around the capitate during the radial–ulnar deviation. The ulnar side of the TFCC
was elongated by an average of 15 mm in length in 15 degrees of radial deviation and
shortened by an average of 8 mm in 25 degrees of ulnar deviation ([Fig. 3]). Normal changes in the shape of the proximal half of the TFC were stable with radial–ulnar
deviation ([Fig. 3]), in contrast the distal half of the TFC demonstrated compression from the ulnar
edge of the lunate, radial edge of the triquetrum, and ulnotriquetral interosseous
ligament. Intensities of the TFC, lunate, triquetrum, and ulnar head were slightly
higher on ulnar deviation and lower on radial deviation ([Figs. 3] and [4] and [Video 1]).
Fig. 3 Sequential cine-mode magnetic resonance imaging of the healthy volunteer.
Fig. 4 Normal changes in the shape of the triangular fibrocartilage complex during radial–ulnar
deviation in a healthy volunteer. Ulnar side of the TFCC is stretched in radial deviated
position and is shortened in ulnar deviated position (arrowheads). High signal intensity
in the disc, due to increasing pressure is shown. Note small changes in the shape
of the disc during radial–ulnar deviation (white arrow).
Cine MRI of the TFCC tears
Wavy deformities in the TFC with radioulnar deviation were observed in three horizontal
TFCC tear patients ([Figs. 5] and [6]). At maximum ulnar deviation, the TFC was compressed in radioulnar direction ([Fig. 5] and [Video 2]). Intensity of the disc was slightly higher on ulnar deviation and lower on radial
deviation and this tendency was obvious than the normal volunteers. The changes in
the shape of the TFCC in two patients with traumatic radial slit tear of the TFC were
identical to normal changes in shape of healthy volunteers.
Fig. 5 Sequential cine-mode magnetic resonance imaging of horizontal-type triangular fibrocartilage
complex tear patient.
Fig. 6 Changes in the shape of the triangular fibrocartilage complex with its intrahorizontal
slit tear during radial–ulnar deviation. Wavy deformity is demonstrated especially
in ulnar deviation (arrows).
Cine MRI of Ulnar Styloid Nonunion
In the two patients with ulnar styloid nonunion, snapping of the ulnar styloid fragment
was detected at maximum ulnar deviated position ([Figs. 7] and [8], and [Video 3]). These two patients demonstrated relatively larger fragment of the ulnar styloid.
The triquetrum, hamate, and 5th metacarpal indicated high signal intensity at ulnar
deviation. The other three wrists with relatively smaller ulnar styloid nonunion demonstrated
elongation of the space between the fragment and ulna; however, no special changes
in the shape of the TFCC were found during radioulnar deviation compared with those
in intact TFCC ([Video 4]).
Fig. 7 Sequential cine-mode magnetic resonance imaging of nonunion of the ulnar styloid.
Fig. 8 Changes in the shape of the triangular fibrocartilage with nonunion of the ulnar
styloid during radial–ulnar deviation is same as normal volunteers. Sudden dorsal
snapping of the un-united ulnar styloid is seen in maximum ulnar deviation (white
arrow).
Discussion
As the TFCC is a soft tissue, it may demonstrate changes in its shape during wrist
motion and/or forearm rotation.[4]
[5]
[7]
[8] When the TFCC is torn, it may further demonstrate abnormal dynamic changes in various
wrist motions, which may induce pain, click, or slack. Clinically, patients usually
claim pain with forced pronation–supination, such as twisting doorknob, and with ulnar
deviation, such as gripping or knocking hummer. In the physical examination, the wrist
is forced ulnar deviation with pronation–supination, and if the tear exists, there
may be severe pain and/or click in TFCC tear patients.[3] With the ulnar deviation of the wrist, pressure around the TFCC may increase, and
forced pronation–supination may produce traction and tension on the TFCC, thus inducing
ulnar-sided wrist pain.
In previous biomechanical studies, changes in the shape of the TFCC during forearm
rotation were described.[4]
[5]
[7]
[8] Nakamura et al[4] investigated in vivo changes in the shape of the TFC with high-resolution MRI, where
minimal change in shape was noted. Makita et al[8] later confirmed this by biomechanical cadaver study. However, changes in the shape
of the TFC during radial and ulnar deviation had not been investigated.
MRI is a noninvasive diagnostic tool, especially useful for musculoskeletal soft-tissue
problems. Although clinical application of MRI for TFCC tear has been widely accepted
recently, delineation of the TFCC itself and its tear has been controversial. Arthrogram
is another diagnostic imaging tool for TFCC tear, whose diagnostic specificity is
considered superior to that of MRI.[15] Kato et al[16] found that high-resolution MRI is not appropriate for delineation of details of
the TFCC, whereas several researchers indicated advantage of high-resolution MRI for
diagnosis of TFCC injuries.[10]
[11] Nakamura et al[9] indicated that fat suppression T1-weighted MRI delineated the TFCC best, followed
by gradient echo T2*-weighted images and the quality of these images may be suitable
to delineate the TFCC.
In this study, fat suppression fast SE T1-weighted MR image demonstrated the TFCC
well. The reasons of well delineation of the TFCC in fat suppression MRI are: (1)
contrast differences between the high signal of hyaline cartilage and low signal intensity
of the fibrocartilage and ligaments; (2) contrast differences between high signal
of joint fluid and low signal of fibrocartilage; (3) high signal gain; and (4) less
influence of chemical shift artifact.[9]
We successfully obtained cine-mode MRI in radial–ulnar deviated motion in this study
using the custom setting device. In cine MRI, intact TFCC demonstrated little changes
in the shape of the TFC with stretching of the ulnar side of the TFCC (so-called meniscus
homologue and ulnar joint capsule recognized as 6U-portal) from ulnar to radial deviated
motion. Change in the shape of the TFC was minimal with radial and ulnar deviation.
This is in line with the finding that the TFC simultaneously supports the ulnar carpus,
induces smooth gliding of the carpus, and simultaneously transfers load between the
ulnar carpus and ulna especially in the radial and ulnar deviation.
Increase of MR signal intensity inside the TFCC, lunate, triquetrum, and ulnar head
with ulnar deviation in healthy volunteers was seen in this cine-mode MRI study, which
may be due to increase of pressure in the ulnar space of the wrist.
Wavy deformity in the TFC was demonstrated during radioulnar deviation in three horizontal
TFCC tear patients. Horizontal tear from ulno-distal side of the TFCC extends into
the TFC. This tear was not described in the Palmer classification system.[14] Radiocarpal arthroscopy usually examines distal surface of the TFCC and cannot directly
visualize inside injury of the TFCC. MRI only can delineate inside tear of the TFCC.
When the wrist was ulnar deviated, the proximal carpal row moves radially. Forced
or active ulnar deviation increases radial directional force of the disc both by the
ulnar carpus directly and pulling effect through the ulnolunate and ulnotriquetral
ligaments. Simultaneously, increase of compressive force between the ulnar carpus
and ulna occurs. When there is a horizontal-type tear inside the TFCC, this force
will induce wavy deformity on the distal half of the TFC, which was seen on cine MRI.
This finding further suggests that wavy deformity is one of the causes of ulnar-sided
wrist pain in TFCC injury patient, where abnormal mechanical stress on the TFC induces
pain. In the other two patients with radial slit TFCC tear, the disc did not demonstrate
severe changes in its shape. This may suggest other cause of pain in the radial slit
tear of TFCC.
Snapping of the large nonunion ulnar styloid at maximum ulnar deviation was also delineated
in cine MRI in two patients with relatively larger fragment. Increasing pressure between
the ulnar carpus and ulna may snap out the large un-united styloid process in the
ulnar deviated position. In contrast, the relatively smaller nonunion of the ulnar
styloid process demonstrated only elongation of the space between the fragment and
the ulna in radial deviated position. Different pathomechanics were suggested in ulnar
styloid nonunion patients.
The intact TFCC may normally distribute increased load and pressure in ulnar deviated
position. When the structure of the TFCC is damaged in the inside or outside, such
as horizontal tear of the TFCC or ulnar styloid nonunion, abnormal changes in the
shape of the TFCC may occur, such as the wavy deformity on the TFC, or snapping of
the un-united ulnar styloid, and increased pressure or tension in the ulnar side of
the wrist. These abnormal stresses in the TFCC in ulnar deviation position may correlate
with positive ulnocarpal stress test.[3]
