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Extrinsic Carpal Ligaments: Normal MR Arthrographic Appearance in Cadavers¹

¹ From the Department of Radiology, Veterans Administration Medical Center, 3350 La Jolla Village Dr, San Diego, CA 92161. Received October 19, 2001; revision requested January 11, 2002; revision received March 12; accepted April 2. Supported by the Swiss Radiological Society and the Swiss National Science Foundation. Address correspondence to D.R. (e-mail: dresnick@ucsd.edu).

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
PURPOSE: To describe the normal magnetic resonance (MR) arthrographic anatomy of the major carpal ligaments (excluding scapholunate and lunotriquetral ligaments) and their osseous attachments by using standard imaging planes.

MATERIALS AND METHODS: MR images of 22 wrists derived from fresh human cadaveric hands were obtained after tricompartmental arthrography. The MR arthrographic appearance of the carpal ligaments and their bone attachments were analyzed and correlated to those seen on anatomic sections. Two readers determined in consensus which was the best plane to observe the course and attachment sites for each ligament. They further analyzed the size and sites of attachment of these ligaments in two orthogonal planes chosen for optimal viewing.

RESULTS: Each ligament was well seen as a hypointense linear structure with MR arthrography. The radioscaphocapitate, radiolunotriquetral, radioscapholunate, dorsal radiotriquetral, palmar scaphotriquetral, and dorsal scaphotriquetral ligaments were best evaluated in the transverse plane. The palmar and dorsal ulnotriquetral and ulnolunate ligaments were best visualized in the sagittal plane. The radial collateral ligament was best analyzed in the coronal plane. The attachment sites of all ligaments were best analyzed either in the transverse or sagittal planes.

CONCLUSION: MR arthrography allows visualization of the carpal ligaments. Detailed knowledge of the normal appearance of these ligaments can serve as a baseline for future studies in which MR arthrography is used to characterize wrist instability.

© RSNA, 2002

Index terms: Ligaments • Wrist, arthrography, 434.122 • Wrist, MR, 434.121411, 434.12143

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Chronic wrist pain is a common and difficult diagnostic problem that, in some cases, relates to carpal instability. Such wrist pain may potentially be caused by ligamentous injury not related to recognized carpal instability. The ligamentous anatomy of the wrist and the ligamentous integrity are important to carpal stability (1,2). Controversy exists in the literature regarding the terminology applied to individual ligaments of the wrist (3–6). Taleisnik (7) divided the carpal ligaments into two major groups: extrinsic ligaments and intrinsic ligaments. The intrinsic ligaments are ligaments that are entirely within the carpus, between carpal bones. The extrinsic ligaments are those that have an attachment on the carpus and pass out of the carpus. Injuries to the intrinsic and extrinsic ligaments of the wrist are probably more common than appreciated (8). The identification of ligamentous attachment sites is important to ensure analysis of the entire ligament. The normal magnetic resonance (MR) anatomy of the carpal ligaments was reported recently (9,10), but the attachments sites of these ligaments have been previously reported only with multiplanar reconstructions of three-dimensional Fourier-transform MR imaging (11,12).

The purpose of our article was to describe the normal MR arthrographic anatomy of the major carpal ligaments (excluding the scapholunate and lunotriquetral ligaments) and their osseous attachments by using standard imaging planes.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Cadavers and Specimen Preparation
Twenty-two fresh human hands were harvested from 11 nonembalmed cadavers (age range at death, 45–90 years; mean age at death, 75 years). There was limited clinical information. Institutional policies were followed regarding cadaver use. The specimens were derived from arms cut through the distal portions of the radius and ulna. The specimens were immediately deep-frozen at -40°C (Forma Bio-Freezer; Forma Scientific, Marietta, Ohio). All specimens were allowed to thaw for 24 hours at room temperature prior to routine radiography. Posteroanterior and lateral projections were obtained prior to MR imaging to confirm the absence of osseous abnormalities. No osseous abnormalities were noted.

MR Arthrography
With fluoroscopic guidance, a musculoskeletal radiologist (N.H.T.) inserted a 22-gauge (0.7 x 40.0-mm) needle directly through the skin from a dorsal approach and advanced it into the midcarpal joint between lunate and hamate bones. The position of the needle tip was verified with a test injection of a small amount of iodinated contrast agent (Omnipaque 350; Nycomed Amersham, Princeton, NJ). A solution of 1 mL of gadopentetate dimeglumine (Magnevist; Schering, Berlin, Germany) diluted in 200 mL of a solution composed of half saline and half iodinated contrast material (Omnipaque 350) was injected in the midcarpal joint with fluoroscopic control. A total volume of 3–4 mL of the solution was injected. If a communication with the radiocarpal joint was present, an additional 3–4 mL of the solution was added. With communication to both the radiocarpal and the distal radioulnar joints, a further additional 1–2 mL of the solution was added, making a total of 7–9 mL. If no communication was present, the radiocarpal and distal radioulnar joints were sequentially injected from a dorsal approach with 3–4 mL and 1–2 mL of the solution, respectively. Conventional posteroanterior and lateral radiographs were then obtained.

MR imaging was performed within 30 minutes following injection of the contrast agent. MR imaging studies were obtained with a 1.5-T MR imaging unit (Signa; GE Medical Systems, Milwaukee, Wis) with a dedicated wrist coil (Quadrature; GE Medical Systems). The hand was placed in prone position, with the wrist in neutral position in the center of the bore, pinpointed by the laser mark. Five sequences were performed: transverse, coronal, and sagittal T1-weighted spin-echo sequences (repetition time msec/echo time msec, 500/12–23; section thickness, 2.5 mm; interspace, 0.5 mm; number of signals acquired, two; field of view, 6 x 6 cm; matrix, 512 x 256; acquisition time, 8 minutes 50 seconds for each sequence); sagittal T1-weighted fat-saturated spin-echo sequence (500/12; section thickness, 2.5 mm; interspace, 0.5 mm; number of signals acquired, two; field of view, 8 x 8 cm; matrix, 512 x 256; acquisition time, 8 minutes 50 seconds); and coronal T1-weighted fat-saturated spin-echo sequence (500/12; section thickness, 2 mm; interspace, 0.5 mm; number of signals acquired, two; field of view, 8 x 8 cm; matrix, 512 x 256; acquisition time, 8 minutes 50 seconds). Coronal (n = 7), sagittal (n = 7), or transverse (n = 8) programmed planes were drawn on the specimen by using the laser mark of the bore as a reference.

MR-Anatomic Comparison
After imaging, all cadaveric specimens were immediately frozen in neutral position at -40°C for at least 24 hours and were subsequently sliced with a band saw into 2-mm-thick slices (that corresponded to the thickness of the MR images) along one of the following imaging planes, according to lines drawn on the specimen at the time of imaging: coronal (n = 7), sagittal (n = 7), or transverse (n = 8) planes. Photographs of each slice were obtained, with the specimen thawed.

MR images were interpreted retrospectively in consensus by two musculoskeletal radiologists (N.H.T., C.W.A.P) with 3 and 4 years of experience. Each carpal ligament shown in Figure 1 was analyzed in the 22 wrists. Their appearance and signal intensity on MR images were compared with the appearance derived from inspection of the corresponding anatomic slices. The ligaments were classified as radiocarpal, ulnocarpal, or intercarpal and as palmar or dorsal. The best MR imaging plane to analyze the course, attachment sites, and cross-sectional dimensions of each ligament was determined and confirmed with anatomic correlation. The cross-sectional dimensions were measured digitally in at least two orthogonal planes on MR images, chosen to best show the ligaments and their bone attachments. These were measured at the midportion of each ligament and at their bone attachments. A simplified approach was developed to facilitate recognition of each ligament in the three orthogonal planes.

View larger version (79K): [in this window] [in a new window] [Download PPT slide]   Figure 1a. (a) Schematic shows the palmar carpal ligaments (frontal view). 1 = radioscaphocapitate (RSC) ligament, 2 = radiolunotriquetral (RLT) (long radiolunate) ligament, 3 = radioscapholunate ligament, 4 = palmar ulnotriquetral ligament, 5 = ulnolunate ligament, 6 = proximal and distal bands of the palmar scaphotriquetral ligament. The thick black line along the distal surface of the ulna represents the palmar radioulnar ligament. (b) Schematic shows the dorsal carpal ligaments (frontal view). 7 = dorsal scaphotriquetral ligament, 8 = dorsal radiotriquetral ligament, 9 = dorsal ulnotriquetral ligament, 10 = radial collateral ligament. Thick black line represents the dorsal radioulnar ligament.

View larger version (78K): [in this window] [in a new window] [Download PPT slide]   Figure 1b. (a) Schematic shows the palmar carpal ligaments (frontal view). 1 = radioscaphocapitate (RSC) ligament, 2 = radiolunotriquetral (RLT) (long radiolunate) ligament, 3 = radioscapholunate ligament, 4 = palmar ulnotriquetral ligament, 5 = ulnolunate ligament, 6 = proximal and distal bands of the palmar scaphotriquetral ligament. The thick black line along the distal surface of the ulna represents the palmar radioulnar ligament. (b) Schematic shows the dorsal carpal ligaments (frontal view). 7 = dorsal scaphotriquetral ligament, 8 = dorsal radiotriquetral ligament, 9 = dorsal ulnotriquetral ligament, 10 = radial collateral ligament. Thick black line represents the dorsal radioulnar ligament.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

Extrinsic Ligaments
Palmar
Radiocarpal ligaments.—The RSC ligament (Fig 2) is a prominent ligament that arose from the palmar and radial aspects of the radial styloid process. Most often its radial attachment could not be distinguished from that of the RLT, also known as the long radiolunate, ligament (Fig 3). The RSC ligament ran in an oblique direction and traversed a groove in the waist of the scaphoid. It was attached by a fibrous band to the palmar aspect of the distal pole of the scaphoid in common with the palmar scaphotriquetral ligament. The RSC ligament extended distally to a wide insertion in the center of the palmar aspect of the capitate distal to the insertion of the distal band of the palmar scaphotriquetral ligament.

View larger version (29K): [in this window] [in a new window] [Download PPT slide]   Figure 2. Schematic shows the RSC (1), ulnolunate (2), and radial collateral (3) ligaments in the transverse (left) (from distal to proximal = top to bottom), sagittal (middle) (from radial to ulnar = left to right), and coronal (right) planes. C = capitate, H = hamate, L = lunate, P = pisiform, R = radius, S = scaphoid, T = triquetrum, U = ulna.

View larger version (183K): [in this window] [in a new window] [Download PPT slide]   Figure 3a. Palmar radiocarpal and intercarpal ligaments. (a) Coronal T1-weighted spin-echo (500/12) MR arthrographic image. The RSC ligament arises from the radial aspect of the radial styloid process. It inserts widely on the palmar aspect of the capitate (C). The palmar scaphotriquetral ligament (pST) is composed of a proximal band running directly from the scaphoid (S) to the triquetrum (T) and a distal band forming an arch from the scaphoid to the capitate, hamate (H), and triquetrum. The radioscapholunate (RSL) ligament (arrowhead) arises from the distal palmar aspect of the radius (R) and extends distally to the scapholunate ligament. The RLT (long radiolunate) ligament arises in common with the RSC ligament. The palmar ulnotriquetral ligament arises from the palmar radioulnar ligament. L = lunate. (b) Coronal anatomic comparison specimen of the wrist. The RSC ligament arises from the radial aspect of the radial styloid process. It inserts widely on the palmar aspect of the capitate. The RLT ligament arises in common with the RSC ligament (arrowheads). The ulnolunate (UL) and palmar ulnotriquetral (UT) ligaments arise from the palmar radioulnar ligament (arrows). P = pisiform, R = radius, S = scaphoid.

View larger version (195K): [in this window] [in a new window] [Download PPT slide]   Figure 3b. Palmar radiocarpal and intercarpal ligaments. (a) Coronal T1-weighted spin-echo (500/12) MR arthrographic image. The RSC ligament arises from the radial aspect of the radial styloid process. It inserts widely on the palmar aspect of the capitate (C). The palmar scaphotriquetral ligament (pST) is composed of a proximal band running directly from the scaphoid (S) to the triquetrum (T) and a distal band forming an arch from the scaphoid to the capitate, hamate (H), and triquetrum. The radioscapholunate (RSL) ligament (arrowhead) arises from the distal palmar aspect of the radius (R) and extends distally to the scapholunate ligament. The RLT (long radiolunate) ligament arises in common with the RSC ligament. The palmar ulnotriquetral ligament arises from the palmar radioulnar ligament. L = lunate. (b) Coronal anatomic comparison specimen of the wrist. The RSC ligament arises from the radial aspect of the radial styloid process. It inserts widely on the palmar aspect of the capitate. The RLT ligament arises in common with the RSC ligament (arrowheads). The ulnolunate (UL) and palmar ulnotriquetral (UT) ligaments arise from the palmar radioulnar ligament (arrows). P = pisiform, R = radius, S = scaphoid.

View larger version (30K): [in this window] [in a new window] [Download PPT slide]   Figure 4. Schematic shows the RLT (or long radiolunate) (1), scaphotriquetral (2), and palmar ulnotriquetral (3) ligaments in the transverse (left) (from distal to proximal = top to bottom), sagittal (middle) (from radial to ulnar = left to right), and coronal (right) planes. C = capitate, H = hamate, L = lunate, P = pisiform, R = radius, S = scaphoid, T = triquetrum, U = ulna. The palmar ulnotriquetral ligament attaches proximally to the palmar radioulnar ligament and not directly onto the ulna.

View larger version (96K): [in this window] [in a new window] [Download PPT slide]   Figure 5a. (a) Sagittal T1-weighted fat-saturated spin-echo (500/12) MR arthrographic image of the wrist and (b) anatomic correlation. The RSC ligament courses through the groove of the palmar aspect of the waist of the scaphoid (S) and attaches to the palmar aspect of its distal pole (arrows). The RLT ligament arises from the palmar edge of the distal radius (R) (arrowheads). Tp = trapezium, Tr = trapezoid.

View larger version (134K): [in this window] [in a new window] [Download PPT slide]   Figure 5b. (a) Sagittal T1-weighted fat-saturated spin-echo (500/12) MR arthrographic image of the wrist and (b) anatomic correlation. The RSC ligament courses through the groove of the palmar aspect of the waist of the scaphoid (S) and attaches to the palmar aspect of its distal pole (arrows). The RLT ligament arises from the palmar edge of the distal radius (R) (arrowheads). Tp = trapezium, Tr = trapezoid.

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figure 6. Transverse T1-weighted spin-echo (500/12) MR arthrographic image of the wrist. The RLT ligament arises from the palmar aspect of the distal radius (R) and radial styloid process (arrowheads), extends to the palmar aspect of the lunate (L, short arrows), and extends ulnarly to the radial side of the pisotriquetral joint on the palmar aspect of the triquetrum (T, long arrows). The dorsal radiotriquetral (dRT) ligament arises from the dorsal aspect of the distal radius and extends over the scaphoid (S) and the lunate to insert on the dorsal aspect of the triquetrum. P = pisiform.

Ulnocarpal ligaments.—The palmar ulnotriquetral ligament (Fig 4) was attached proximally and extended perpendicularly to the palmar radioulnar ligament, to its wide insertion in the palmar aspect of the triquetrum (Fig 7).

View larger version (145K): [in this window] [in a new window] [Download PPT slide]   Figure 7a. (a) Sagittal T1-weighted spin-echo (500/12) MR arthrographic image of the wrist. The palmar ulnotriquetral ligament (pUT) arises from the palmar radioulnar ligament (pRUL, open arrow) and extends perpendicularly to the palmar radioulnar ligament to the proximal and palmar aspect of the triquetrum (T, arrowheads). The dorsal ulnotriquetral (dUT) ligament arises from the dorsal radioulnar ligament (dRUL, curved arrow) and extends to the dorsal aspect of the triquetrum to a common insertion with the dorsal radiotriquetral ligament (straight arrows). The triangular fibrocartilage is the dark structure extending between the palmar radioulnar ligament and the dorsal radioulnar ligament. U = ulna. (b) Sagittal anatomic correlation. The palmar ulnotriquetral ligament (pUT) arises from and extends perpendicularly to the palmar radioulnar ligament (open arrows) to the proximal and palmar aspect of the triquetrum (T, arrowheads). The dorsal ulnotriquetral ligament (dUT) arises from the dorsal radioulnar ligament (straight solid arrows) and extends to the dorsal aspect of the triquetrum to a common insertion with the dorsal radiotriquetral ligament (curved arrow). TFC = triangular fibrocartilage, U = ulna.

View larger version (154K): [in this window] [in a new window] [Download PPT slide]   Figure 7b. (a) Sagittal T1-weighted spin-echo (500/12) MR arthrographic image of the wrist. The palmar ulnotriquetral ligament (pUT) arises from the palmar radioulnar ligament (pRUL, open arrow) and extends perpendicularly to the palmar radioulnar ligament to the proximal and palmar aspect of the triquetrum (T, arrowheads). The dorsal ulnotriquetral (dUT) ligament arises from the dorsal radioulnar ligament (dRUL, curved arrow) and extends to the dorsal aspect of the triquetrum to a common insertion with the dorsal radiotriquetral ligament (straight arrows). The triangular fibrocartilage is the dark structure extending between the palmar radioulnar ligament and the dorsal radioulnar ligament. U = ulna. (b) Sagittal anatomic correlation. The palmar ulnotriquetral ligament (pUT) arises from and extends perpendicularly to the palmar radioulnar ligament (open arrows) to the proximal and palmar aspect of the triquetrum (T, arrowheads). The dorsal ulnotriquetral ligament (dUT) arises from the dorsal radioulnar ligament (straight solid arrows) and extends to the dorsal aspect of the triquetrum to a common insertion with the dorsal radiotriquetral ligament (curved arrow). TFC = triangular fibrocartilage, U = ulna.

View larger version (132K): [in this window] [in a new window] [Download PPT slide]   Figure 8. Sagittal T1-weighted spin-echo (500/12) MR arthrographic image of the wrist. The palmar ulnolunate ligament (UL) arises from the palmar radioulnar ligament (pRUL) and extends to the palmar aspect of the lunate (L) in common with the RLT ligament (black arrowheads). The dorsal ulnotriquetral ligament (dUT) arises from the dorsal radioulnar ligament (dRUL) and extends to the dorsal aspect of the triquetrum (T) to a common insertion with the dorsal radiotriquetral ligament (white arrowheads). Arrows = insertion of the RLT ligament. H = hamate, U = ulna.

View larger version (30K): [in this window] [in a new window] [Download PPT slide]   Figure 9. Schematic shows the dorsal radiotriquetral (1), dorsal scaphotriquetral (2), and dorsal ulnotriquetral (3) ligaments in the transverse (left) (from distal to proximal = top to bottom), sagittal (middle) (from radial to ulnar = left to right), and coronal (right) planes. C = capitate, H = hamate, L = lunate, P = pisiform, R = radius, S = scaphoid, T = triquetrum, U = ulna. The dorsal ulnotriquetral ligament attaches proximally to the dorsal radioulnar ligament and not directly onto the ulna.

View larger version (141K): [in this window] [in a new window] [Download PPT slide]   Figure 10a. (a) Transverse T1-weighted spin-echo (500/12) MR arthrographic image of the wrist. The RLT ligament arises from the palmar aspect of the distal radius (R) and radial styloid process (white arrowheads), extends to the palmar aspect of the lunate (L, arrow), and runs distally to the radial side of the pisotriquetral joint on the palmar aspect of the triquetrum (T, black arrowheads). The dorsal radiotriquetral (dRT) ligament arises from the dorsal aspect of the distal radius and extends over the scaphoid (S) and the lunate to insert on the dorsal aspect of the triquetrum. (b) Transverse anatomic comparison specimen. The RLT ligament arises from the palmar aspect of the distal radius (R) and radial styloid process (white arrowheads), extends to the palmar aspect of the lunate (L) and runs distally to the radial side of the pisotriquetral joint on the palmar aspect of the triquetrum (T, black arrowheads). The dorsal radiotriquetral (dRT) ligament arises from the dorsal aspect of the distal radius (black arrows) and extends over the scaphoid (S) and the lunate to insert on the dorsal aspect of the triquetrum (white arrows). LT = lunotriquetral ligament, SL = scapholunate ligament.

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figure 10b. (a) Transverse T1-weighted spin-echo (500/12) MR arthrographic image of the wrist. The RLT ligament arises from the palmar aspect of the distal radius (R) and radial styloid process (white arrowheads), extends to the palmar aspect of the lunate (L, arrow), and runs distally to the radial side of the pisotriquetral joint on the palmar aspect of the triquetrum (T, black arrowheads). The dorsal radiotriquetral (dRT) ligament arises from the dorsal aspect of the distal radius and extends over the scaphoid (S) and the lunate to insert on the dorsal aspect of the triquetrum. (b) Transverse anatomic comparison specimen. The RLT ligament arises from the palmar aspect of the distal radius (R) and radial styloid process (white arrowheads), extends to the palmar aspect of the lunate (L) and runs distally to the radial side of the pisotriquetral joint on the palmar aspect of the triquetrum (T, black arrowheads). The dorsal radiotriquetral (dRT) ligament arises from the dorsal aspect of the distal radius (black arrows) and extends over the scaphoid (S) and the lunate to insert on the dorsal aspect of the triquetrum (white arrows). LT = lunotriquetral ligament, SL = scapholunate ligament.

Collateral Ligament
The radial collateral ligament (Fig 2) arose from the tip of the radial styloid process and lateral to the common origin of the RSC and RLT ligaments (Fig 11). It inserted distally into the radial aspect of the scaphoid waist. It also blended with the capsule to insert into the trapezium.

View larger version (138K): [in this window] [in a new window] [Download PPT slide]   Figure 11. Coronal T1-weighted fat-saturated spin-echo (500/12) MR arthrographic image of the wrist. The radial collateral ligament arises from the tip of the radial styloid process (arrows) and extends distally to the lateral aspect of the scaphoid (S) waist (arrowheads). L = lunate, R = radius.

Intrinsic Ligaments
Palmar
The palmar scaphotriquetral ligament (Fig 4) arose in common with the fibrous band of the RSC ligament from the scaphoid and extended distally as two parallel bands (Fig 3). The proximal band ran directly to the triquetrum (Fig 12b). The distal band formed an arch and inserted into the palmar aspect of the capitate (distal to the RSC ligament), the palmar aspect of the hamate, and the triquetrum (below the pisohamate ligament) in common with the proximal band. Both bands inserted on the palmar aspect of the triquetrum distal to the RLT ligament. The distal band of the palmar scaphotriquetral ligament is also known as the v-shape ligament, with a radial (scaphocapitate) and an ulnar (capitotriquetral) arm. The RSC, RLT (long radiolunate), and palmar scaphotriquetral ligaments blended together to form the floor of the carpal tunnel (Fig 1a).

View larger version (156K): [in this window] [in a new window] [Download PPT slide]   Figure 12a. (a) Coronal T1-weighted spin-echo (500/12) MR arthrographic image of the wrist. The dorsal radiotriquetral ligament (dRT) arises from the dorsal aspect of the radius (R, arrowheads). The dorsal scaphotriquetral ligament (dST) arises from the dorsal aspect of the scaphoid (arrows) and extends perpendicularly to the long axis of the forearm to the dorsal aspect of the triquetrum (T) distal to the dorsal radiotriquetral ligament (arrowheads). C = capitate, H = hamate, Tr = trapezoid, dRUL = dorsal radioulnar ligament. (b) Transverse T1-weighted spin-echo (500/12) MR arthrographic images of the wrist. The dorsal scaphotriquetral ligament (dST) arises from the dorsal aspect of the scaphoid (S, arrows on left) and extends perpendicularly to the long axis of the forearm to the dorsal aspect of the triquetrum (T, arrows on right) distal to the dorsal radiotriquetral ligament. The proximal band of the palmar scaphotriquetral (pST) ligament extends from the palmar aspect of the scaphoid (arrowheads on left) directly to the triquetrum on the radial side of the pisotriquetral joint (arrowheads on right). C = capitate.

View larger version (149K): [in this window] [in a new window] [Download PPT slide]   Figure 12b. (a) Coronal T1-weighted spin-echo (500/12) MR arthrographic image of the wrist. The dorsal radiotriquetral ligament (dRT) arises from the dorsal aspect of the radius (R, arrowheads). The dorsal scaphotriquetral ligament (dST) arises from the dorsal aspect of the scaphoid (arrows) and extends perpendicularly to the long axis of the forearm to the dorsal aspect of the triquetrum (T) distal to the dorsal radiotriquetral ligament (arrowheads). C = capitate, H = hamate, Tr = trapezoid, dRUL = dorsal radioulnar ligament. (b) Transverse T1-weighted spin-echo (500/12) MR arthrographic images of the wrist. The dorsal scaphotriquetral ligament (dST) arises from the dorsal aspect of the scaphoid (S, arrows on left) and extends perpendicularly to the long axis of the forearm to the dorsal aspect of the triquetrum (T, arrows on right) distal to the dorsal radiotriquetral ligament. The proximal band of the palmar scaphotriquetral (pST) ligament extends from the palmar aspect of the scaphoid (arrowheads on left) directly to the triquetrum on the radial side of the pisotriquetral joint (arrowheads on right). C = capitate.

View larger version (83K): [in this window] [in a new window] [Download PPT slide]   Figure 13a. (a) Sagittal T1-weighted fat-saturated spin-echo (500/12) MR arthrographic image. The RLT ligament arises from the palmar edge (curved arrow) of the distal radius (R) and attaches widely on the palmar aspect of the lunate (L). The RSC ligament inserts in the center of the palmar aspect of the capitate (C). The dorsal radiotriquetral (dRT) ligament arises from the dorsal edge of the distal radius (straight arrows). The dorsal scaphotriquetral (dST) ligament has a thin insertion to the dorsal aspect of the lunate (arrowhead). (b) Sagittal anatomic comparison specimen. The RLT ligament arises from the palmar edge (curved arrow) of the distal radius (R) and attaches widely on the palmar aspect of the lunate (L). The RSC ligament inserts in the center (straight black arrows) of the palmar aspect of the capitate (C). The dorsal radiotriquetral (dRT) ligament arises from the dorsal edge of the distal radius (straight white arrows). The dorsal scaphotriquetral (dST) ligament has a thin insertion to the dorsal aspect of the lunate (arrowhead).

View larger version (154K): [in this window] [in a new window] [Download PPT slide]   Figure 13b. (a) Sagittal T1-weighted fat-saturated spin-echo (500/12) MR arthrographic image. The RLT ligament arises from the palmar edge (curved arrow) of the distal radius (R) and attaches widely on the palmar aspect of the lunate (L). The RSC ligament inserts in the center of the palmar aspect of the capitate (C). The dorsal radiotriquetral (dRT) ligament arises from the dorsal edge of the distal radius (straight arrows). The dorsal scaphotriquetral (dST) ligament has a thin insertion to the dorsal aspect of the lunate (arrowhead). (b) Sagittal anatomic comparison specimen. The RLT ligament arises from the palmar edge (curved arrow) of the distal radius (R) and attaches widely on the palmar aspect of the lunate (L). The RSC ligament inserts in the center (straight black arrows) of the palmar aspect of the capitate (C). The dorsal radiotriquetral (dRT) ligament arises from the dorsal edge of the distal radius (straight white arrows). The dorsal scaphotriquetral (dST) ligament has a thin insertion to the dorsal aspect of the lunate (arrowhead).

General Characteristics
Each ligament was visualized with all sequences (with or without fat saturation) as a linear hypointense structure. The best planes to analyze the course and both attachment sites were always consistent for each ligament. The course and cross section of each of the radiocarpal and intercarpal ligaments were best analyzed in transverse and sagittal planes, respectively. The only exception was the radioscapholunate ligament, whose course was better analyzed in the sagittal plane and its cross section in the transverse plane. The coronal plane showed a good visualization of the course of the radiocarpal ligaments but was not accurate for analyzing their cross sections and attachment sites. The best planes to analyze the courses and cross sections of the ulnocarpal ligaments were sagittal and transverse, respectively. The course and cross section of the radial collateral ligament were best analyzed in the coronal and transverse planes, respectively.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
The wrist is formed by two rows of small carpal bones, the metacarpals distally and the radius and ulnar proximally. The distal row moves with the hand and is not a common site of debilitating injury (14). The proximal row is the level of most wrist movement and injuries (15,16). The bones are connected by ligaments and fibrous bundles of connective tissue. The importance of complete interruption of some of these ligaments is well established, but the consequences of partial interruption to these structures requires further evaluation.

Carpal instability has been classified into five groups (17): dorsal intercalated segment instability, volar intercalated segment instability, ulnar translocation, dorsal subluxation, and palmar carpal subluxation. Taleisnick (18) expanded the classification to include static and dynamic forms of instabilities. This classification was further expanded to include dissociative carpal instability and nondissociative carpal instability (19). This last classification, which is based on whether there is a disruption within the carpal bones of the proximal or distal row (dissociative carpal instability) or between radiocarpal or both carpal rows (nondissociative carpal instability), complements the earlier approaches, which dealt with the alignment of the capitate, lunate, and radius only. The nondissociative carpal instability involves carpal and radiocarpal ligamentous lesions, excluding those of the scapholunate and lunotriquetral interosseous ligaments. The diagnosis of nondissociative carpal instability is based on physical examination findings that demonstrate wrist ligament laxity, passive and painful subluxation between carpal rows, and a sudden painful clunk with change in position of the wrist in the presence of a normal wrist tricompartmental arthrogram. Findings from fluoroscopic examination show all three carpal bones in the proximal row moving as a solitary unit during the painful clunk with nondissociative carpal instability. With dissociative carpal instability, fluoroscopic evaluation findings show dissociative motion between bones in the same carpal row.

The dilemma in treating patients with nondissociative carpal instability (20) and patients with undiagnosed causes of painful wrist is defining the precise location of the abnormalities. Conventional radiography and fluoroscopy allow diagnosis of some types of carpal malalignment but do not depict ligamentous lesions directly (21). Wrist arthrography is a sensitive test for evaluating the interosseous ligaments, but as currently reported in literature, it does not allow evaluation of the extent of disruption of these ligaments or the status of the other carpal ligaments (22,23). Although authors of a recent study reported that the RSC ligament could be visualized during radiocarpal arthrography, there are little data to indicate that abnormalities of the RSC ligament can be diagnosed arthrographically (24).

Scheck et al (25) showed that MR arthrography coupled with three-dimensional gradient-echo sequences allowed analysis of carpal ligaments. They found five ligamentous lesions (in the RLT and RSC ligaments) in 20 painful wrists, and all lesions were verified with arthroscopy. Although these results are preliminary, determination of the normal MR arthrographic appearance of the carpal ligaments and their attachment sites becomes very important.

The extrinsic ligaments work against a different set of forces to stabilize the wrist. Because the distal articular surface of the radius is sloped with both a palmar and an ulnar incline, the transversely loaded carpus tends to slide in a palmar and ulnar direction. This tendency is resisted by the obliquely oriented palmar and dorsal radiocarpal ligaments (26). The RSC, RLT (long radiolunate), palmar scaphotriquetral, and dorsal scaphotriquetral ligaments were the largest, both in our study and in the literature (1). The RLT (long radiolunate) ligament is more important clinically for load transference, while the RSC ligament functions mainly to retain the scaphoid in position (14).

Taleisnick (15) categorized ulnar translocation into two types. In type I, the entire carpus is translated in an ulnar direction, including the scaphoid. This situation requires complete radiocarpal ligamentous interruption. In type II, the RSC ligament is preserved, and the scaphoid remains in its normal position with respect to the radius, while the remaining carpus translates in an ulnar direction. Scapholunate dissociation is present in type II ulnar translocation. Ulnar carpal dislocation can be accompanied by a complete tear of the extrinsic ligaments, without interosseous ligamentous lesions (27).

The radioscapholunate ligament has been shown to contain vascular and neural elements and no ligamentous tissue (13). According to Berger and Kauer (13) and as confirmed in our study, no ligamentous fibers were depicted within the radioscapholunate ligament. The term radioscapholunate bundle is preferred. The function of the palmar scaphotriquetral ligament is to support the head of the capitate during dorsal flexion. A tear of the palmar scaphotriquetral ligament causes an instability pattern (dorsal intercalated segment instability) that is radiologically evident at an early stage (28). Tears of the other carpal ligaments, although often found, become radiologically evident only as carpal collapse or ulnar dislocation occur (28). In our study, these major carpal ligaments and their attachment sites were well visualized with MR arthrography.

The function of the palmar ulnotriquetral and dorsal ulnotriquetral ligaments, in common with the ulnolunate ligament, is to stabilize the distal radioulnar joint during pronation and supination of the wrist (1). Furthermore, these ligaments, along with other components of the triangular fibrocartilage complex and the radiocarpal ligaments, prevent ulnar dislocation of the carpal bones. In our experience, these ligaments were well visualized in the sagittal and transverse planes.

The radial collateral ligament was small and thin in comparison with other carpal ligaments. It only slightly influences wrist stability, as the normal wrist demonstrates freedom of radial directed movements requiring flexible radial-sided supporting structures (29). The majority of radial-sided support is provided by the tendons of the extrinsic muscles, which cross the wrist to the hand and provide active stabilization of the carpal bones. We did not include the ulnar collateral ligament in our analysis because it was not possible to identify this ligament as a distinct structure. Only some scattered hypointense ligamentous fibers were identifiable, and these fibers blended with the thick sheath of the extensor carpi ulnaris tendon, suggesting a close association between the two structures. The existence of the ulnar collateral ligament has already been disputed in a previous report (30).

The diagnosis of specific soft-tissue and cartilaginous lesions of the wrist influences the choice between surgical or nonsurgical treatment (31). In suspected tears of the extrinsic ligaments, authors of recent reports have recommended arthroscopy for the inspection of the attachments of the ligaments because no alternative diagnostic method was available (31,32). MR arthrography, therefore, may represent this alternative.

The anatomy and integrity of the wrist ligaments are not routinely studied. The analytic approach proposed in our schematic display of each ligament, together with associated measurements of cross sections and attachment sites, are useful tools to simplify the analysis of each ligament and to exclude injuries of their body or insertions. Our measurements establish the average dimensions of the cross sections and attachments of these ligaments in the orthogonal planes clinically used. The detection of a marked deviation in these measurements, when compared with our average measurements, suggests the presence of a ligamentous defect (partial or complete tear).

There are several limitations to this study. First, clinical information was limited, a common problem in cadaveric studies. Routine radiography, however, allowed exclusion of major osseous abnormalities or signs of carpal instabilities. Second, the use of cadaveric specimens allowed us to place the anatomic area of interest exactly in the center of the bore in the best position for imaging, a situation that is not always possible in patients. Clinically available equipment, however, was used in this study. Third, the use of specimens allowed us to fully distend, without "pain," the joint capsule and fill all three wrist compartments, which helped to delineate the carpal ligaments. However, an amount of contrast agent similar to that typically used in clinical procedures was used. Finally, owing to the small sample size, variability of the measurements cannot be definitively addressed by the results of our study.

In conclusion, MR arthrography allows visualization of the carpal ligaments. MR arthrography may potentially represent an alternative diagnostic method to arthroscopy in the assessment of ligamentous injuries of the wrist. Detection of abnormalities of wrist ligaments may be valuable in diagnosing causes of the unexplained painful wrist. MR arthrography may also become a tool for understanding the relationship between ligamentous integrity and clinical manifestations. Further exploration of the accuracy of MR arthrography in a clinical setting is warranted.

	FOOTNOTES

 
² Current address: Department of Radiology, CHUV, Lausanne, Switzerland.

Abbreviations: RLT = radiolunotriquetral, RSC = radioscaphocapitate

Author contributions: Guarantors of integrity of entire study, N.H.T., C.W.A.P., D.R., L.A.G.; study concepts, N.H.T., C.W.A.P., C.B.C.; study design, N.H.T., C.W.A.P.; literature research, N.H.T., C.W.A.P., G.E.A.; clinical studies, N.H.T., C.W.A.P.; experimental studies, N.H.T., C.W.A.P., D.J.T.; data acquisition and analysis/interpretation, N.H.T., C.W.A.P.; statistical analysis, N.H.T., C.W.A.P.; manuscript preparation, N.H.T., C.W.A.P., C.B.C., G.E.A., L.A.G., D.R.; manuscript definition of intellectual content, N.H.T., C.W.A.P., C.B.C., D.R.; manuscript editing, C.B.C., G.E.A., D.R.; manuscript revision/review, G.E.A., D.R.; manuscript final version approval, D.R.

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