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Published online before print January 7, 2002, 10.1148/radiol.2222010181
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(Radiology 2002;222:437-445.)
© RSNA, 2002

Musculoskeletal Imaging

MR Imaging of the Metacarpophalangeal Joints of the Fingers

Part I. Conventional MR Imaging and MR Arthrographic Findings in Cadavers1

Nicolas H. Theumann, MD, Christian W. A. Pfirrmann, MD, Jean-Luc Drapé, MD, PhD, Debra J. Trudell, RA and Donald Resnick, MD

1 From the Department of Radiology, Veterans Administration Medical Center, 3350 La Jolla Village Dr, San Diego, CA 92161 (N.H.T., C.W.A.P., D.J.T., D.R.); Department of Radiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland (N.H.T.); and Department of Radiology B, CHU Cochin, Assistance Publique-Hôpitaux de Paris-Université Paris V, France (J.L.D.). Received December 18, 2000; revision requested February 7, 2001; final revision received July 25; accepted July 30. Supported by the Swiss Radiological Society and the Swiss National Science Foundation. Address correspondence to D.R. (e-mail: dresnick@ucsd.edu). © RSNA, 2001


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
PURPOSE: To demonstrate the normal anatomy of the metacarpophalangeal (MCP) joints of the fingers with magnetic resonance (MR) imaging and MR arthrography in cadavers.

MATERIALS AND METHODS: MR images of 20 MCP joints of the fingers of five fresh human cadaveric hands in the extended and flexed positions were obtained before and after arthrography. The MR appearances of all articular and periarticular structures were analyzed and compared with those seen on anatomic sections. Two readers independently graded the visibility of these structures. Interobserver agreement was tested by using the {kappa} statistic.

RESULTS: The main collateral ligaments could be best evaluated on the transverse images of flexed fingers. The accessory bands of the collateral ligament complex were best seen on the transverse images of extended fingers. Sagittal MR images were best for evaluating the palmar plate and the capsule. MR arthrography improved the visualization of all articular and periarticular structures. The {kappa} values related to conventional MR imaging findings at all sequences, 0.42–0.71, indicated moderate to substantial agreement. The {kappa} values for the MR arthrographic sequences, 0.59–0.74, were slightly higher than those for the nonenhanced sequences.

CONCLUSION: Conventional MR imaging and MR arthrography enable accurate visualization of the important anatomic structures of the MCP joints. MR arthrography enhances visualization of the intraarticular elements.

Index terms: Extremities, MR, 437.121411, 437.121412, 437.121416, 437.12143, 437.124 • Fingers and toes, 437.40, 437.92 • Hand, arthrography, 437.12143, 437.124, 437.92 • Magnetic resonance (MR), arthrography, 437.12143, 437.124


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Although uncommon, injuries of the metacarpophalangeal (MCP) joints of the fingers necessitate accurate diagnosis, because the loss of function of even one MCP joint can seriously impair overall hand function (1). To ensure appropriate treatment, the identification of the damaged structures at the time of injury is essential. Advances in magnetic resonance (MR) imaging technology that improve spatial resolution enable the visualization of important intra- and periarticular structures, even in small joints such as the MCP joints, with standard clinical equipment. Detailed knowledge of the normal anatomy remains essential to the analysis of MR images of this area.

Imaging of the MCP joints is not performed routinely. Several methods of imaging the MCP joints have been used as a supplement to routine radiography. Dynamic conventional radiography (2) can show instability of the MCP joints and indirectly depict a ligamentous lesion. Arthrography of the MCP joints also has been used to detect injuries of the collateral ligaments (3). Ultrasonographic (US) examination of the fingers has been described (4–6), but access to the MCP joints of the fingers with this modality is limited by the adjacent fingers. In general, these different imaging methods are limited in the evaluation of the different intraarticular structures of the MCP joint because of their lack of good spatial resolution and lack of good contrast, both of which are needed to delineate the fine anatomic structures of these joints. The role of MR imaging in the assessment of MCP joint abnormalities has been described in a few investigations (5,7–9). However, to our knowledge, no report in the literature detailing MR arthrography of the MCP joints of the fingers exists. Thus, the purpose of this study was to demonstrate the normal anatomy of the MCP joints of the fingers with MR imaging and MR arthrography in cadavers.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Cadavers and Specimen Preparation
Twenty MCP joints of five fresh cadaveric hands were imaged. These joints were harvested from three nonembalmed cadavers (one woman, two men; age range at death, 61–89 years; mean age at death, 78 years). The specimens were taken 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). To exclude the depiction of traumatic or degenerative articular disorders, radiography in the frontal and lateral projections was performed in all specimens. All specimens were allowed to thaw for 24 hours at room temperature prior to MR imaging.

Nonenhanced MR Imaging
Standard nonenhanced MR imaging studies were obtained by using a 1.5-T unit (Signa; GE Medical Systems, Milwaukee, Wis) and either a wrist coil for assessment of the MCP joints in extended positions or a wrap coil for assessment of the MCP joints in flexed positions. The hand was placed in the prone position in the center of the gantry.

The MCP joints were first examined in extension. Transverse T1-weighted spin-echo MR images (500/12 [repetition time msec/echo time msec], 2-mm section thickness, 0.5-mm interspace, two signals acquired, 6 x 6-cm field of view, 512 x 256 matrix, acquisition time of 4 minutes 23 seconds) were obtained. This sequence was performed two times: first with the second and third MCP joints placed in the center of the field and then with the fourth and fifth MCP joints placed in this position. Two sets of coronal T1-weighted spin-echo MR images were obtained by using the same parameters and MCP joint positioning that were used to obtain the transverse images. Transverse three-dimensional fast gradient-recalled-echo (GRASS; GE Medical Systems) MR images (50/12, 0.7-mm section thickness, no interspace, two signals acquired, 8 x 8-cm field of view, 60° flip angle, 512 x 256 matrix, acquisition time of 10 minutes 30 seconds) were then acquired.

Subsequently, the MCP joints were taped in 90° of flexion, and transverse T1-weighted spin-echo MR images (500/12, 2-mm section thickness, 0.5-mm interspace, three signals acquired, 9 x 9-cm field of view, 512 x 256 matrix, acquisition time of 6 minutes 30 seconds) were obtained.

MR Arthrography
With fluoroscopic guidance, a 22-gauge (0.7 x 40.0-mm) needle was inserted directly through the skin from a dorsal approach and advanced into the MCP joints. The position of the tip of the needle was verified with a test injection of a small amount of the iodinated contrast agent iohexol (Omnipaque 350; Nycomed Amersham, Princeton, NJ). Subsequently, approximately 1–3 mL of a solution consisting of 1 mL of gadopentetate dimeglumine (Magnevist; Schering, Berlin, Germany) diluted in 250 mL of saline and mixed with an equal amount of iohexol was injected into each joint with fluoroscopic control. Conventional anteroposterior radiographs were then obtained to confirm optimal filling of the joints and to exclude substantial leakage of contrast agent. MR arthrography was performed within 30 minutes following the injection of the contrast agent. MR sequences identical to those used before opacification of the joint were performed with the long fingers in extension and in flexion.

Two sagittal T1-weighted spin-echo MR sequences with the MCP joints in extension and then in flexion were successively performed. The first sagittal T1-weighted spin-echo MR sequence (500/12, 2.5-mm section thickness, 0.6-mm interspace, two signals acquired, 6 x 6-cm field of view, 512 x 256 matrix, acquisition time of 8 minutes 50 seconds) was performed by using the wrist coil. The second sagittal T1-weighted spin-echo MR sequence (500/12, 2.5-mm section thickness, 0.5-mm interspace, three signals acquired, 9 x 9-cm field of view, 512 x 256 matrix, acquisition time of 11 minutes 43 seconds) was performed by using the wrap coil.

Comparison of MR Imaging and Anatomic Features
After imaging, all cadaveric specimens were immediately positioned with the MCP joint in either extension (n = 3) or flexion (n = 2), frozen at -40°C for at least 24 hours, and subsequently cut with a band saw into 2-mm-thick sections that corresponded to the thickness of the images along one of the imaging planes according to lines drawn on the specimen at the time of imaging: coronal (n = 1), sagittal (n = 1), or transverse (n = 1) plane with the MCP joints in extension and sagittal (n = 1) or transverse (n = 1) plane with the MCP joints in flexion. Photographs of each section were taken with the specimen thawed.

The MR images and arthrograms were interpreted by two musculoskeletal radiologists (N.H.T., C.W.A.P.) who were blinded to the results of each other’s readings. All images of a given specimen were analyzed at the same time. Intra- and periarticular structures were identified on all MR images and arthrograms of the study according to their descriptions in the literature (10), and their appearances on these images (in one plane for each specimen) were correlated with their appearances at inspection of the corresponding anatomic sections. The postcontrast radiographs were not compared with the anatomic sections or the MR images. Data regarding the following intraarticular structures (Fig 1) were recorded:



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  		Figure 1. Drawing illustrates transverse view of the main structures of the MCP joint after removal of the metacarpal head.

 
1. The proximal and distal cartilaginous surfaces and the proximal and distal capsular attachments.

2. The ligamentous structures, which include the proximal and distal attachments and bodies of the main radial and ulnar collateral ligaments, the distal attachments and bodies of the radial and ulnar accessory collateral ligaments, the proximal and distal attachments and bodies of the palmar plates (PPs), the recesses of the distal attachment of the PP, and the deep transverse metacarpal ligament (DTML).

3. The extensor hood formed by the following: radial and ulnar sagittal bands, transverse fibers of the interosseous tendinous part of the extensor hood on the radial and ulnar sides (Fig 2), and fibrous connections between the extensor tendons of the second and fifth fingers (11).



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  		Figure 2. Drawing of the extensor hood. The sagittal bands are located above the joint line, and the transverse fibers of the lumbrical and interosseous tendons are more distal, over the proximal phalanx.

 
4. The musculotendinous structures: first annular (A1) pulley, palmar and dorsal interosseous muscles and tendons, and lumbrical muscles.

Visibility of each normal structure at each MR sequence was graded in four categories: 1, nonvisible; 2, visible but nonanalyzable (ie, MR characteristics could not be interpreted); 3, visible and analyzable; and 4, excellent visibility. An MR sequence was rated as good when the average grade for both readers was equal to or more than 3.5. The detection rates with each sequence were compared. No statistical tests were performed to compare the value of each sequence in enabling visualization of each structure.

Interobserver agreement findings for each MR sequence were tested by calculating {kappa} statistics (12). Agreement was rated, according to the method of Landis and Koch (13), as follows: {kappa} values of 0–0.20 indicated slight agreement; values of 0.21–0.40, fair agreement; values of 0.41–0.60, moderate agreement; values of 0.61–0.80, substantial agreement; and values of 0.81–0.99, excellent agreement. A value of 1.00 indicated absolute agreement. Differences between the prearthrographic (ie, conventional MR imaging) and arthrographic assessments of all structures were compared for all sequences, all imaging planes, and both readers by using a paired t test. A P value of .05 indicated a significant difference.

On the basis of results of analysis of all the MR images, the same two observers reached a consensus regarding the following measurements: (a) the maximum diameter of both main collateral ligaments on the transverse T1-weighted spin-echo arthrograms of the fingers flexed, (b) the maximum diameter of both accessory collateral ligaments on the transverse T1-weighted spin-echo arthrograms of the fingers extended, and (c) the length and maximum (immediately proximal to the distal attachment) and minimum (immediately distal to the proximal attachment) thicknesses of the PP on the sagittal T1-weighted spin-echo arthrograms of the fingers extended.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 
The results of analysis of the MR images and arthrograms are shown in Tables 1 and 2.


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  		TABLE 1. Visualization Grading of Conventional MR Imaging and MR Arthrographic Sequences

 

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  		TABLE 2. MCP Joint Measurements

 
Articular Structures: Capsule and Cartilage
At anatomic inspection, the capsule was loose and attached to the elevated crest surrounding the smooth articular surface of the head of the metacarpal bone and the ridge separating the articular concave base from the shaft of the proximal phalanx. On MR images, depiction of the proximal and distal attachments of the capsule necessitated intraarticular injection of contrast agent. These attachments were best seen on the sagittal T1-weighted spin-echo MR arthrograms of the fingers in the extended position (Fig 3). Visualization of the chondral surface was better after intraarticular injection of contrast agent compared with visualization at standard spin-echo MR imaging (grade, 3.5–4.0 vs 1.2–1.5). At nonarthrographic MR imaging, the cartilage surface was depicted better on the fast gradient-recalled-echo images than on the spin-echo images (grade, 2.5–3.5 vs 1.2–1.5).



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  		Figure 3a. Sagittal MR arthrograms of the MCP joint of the third finger in extension, with anatomic correlation. (a) T1-weighted spin-echo MR arthrogram (500/12) and (b) corresponding anatomic section show the PP (curved arrow), distal recess of the PP (short solid arrow), and loose proximal recess (arrowheads). A bare area (open arrow) can be seen between the cartilage (long straight arrows) and the dorsal insertion of the capsule. (c) T1-weighted spin-echo MR arthrogram (500/12) of the MCP of the third finger in flexion shows that the PP is angled, the distal recess (white arrow) is compressed, and the flexor tendons (black arrow) are applied to the surface of the bone.

 


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  		Figure 3b. Sagittal MR arthrograms of the MCP joint of the third finger in extension, with anatomic correlation. (a) T1-weighted spin-echo MR arthrogram (500/12) and (b) corresponding anatomic section show the PP (curved arrow), distal recess of the PP (short solid arrow), and loose proximal recess (arrowheads). A bare area (open arrow) can be seen between the cartilage (long straight arrows) and the dorsal insertion of the capsule. (c) T1-weighted spin-echo MR arthrogram (500/12) of the MCP of the third finger in flexion shows that the PP is angled, the distal recess (white arrow) is compressed, and the flexor tendons (black arrow) are applied to the surface of the bone.

 


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  		Figure 3c. Sagittal MR arthrograms of the MCP joint of the third finger in extension, with anatomic correlation. (a) T1-weighted spin-echo MR arthrogram (500/12) and (b) corresponding anatomic section show the PP (curved arrow), distal recess of the PP (short solid arrow), and loose proximal recess (arrowheads). A bare area (open arrow) can be seen between the cartilage (long straight arrows) and the dorsal insertion of the capsule. (c) T1-weighted spin-echo MR arthrogram (500/12) of the MCP of the third finger in flexion shows that the PP is angled, the distal recess (white arrow) is compressed, and the flexor tendons (black arrow) are applied to the surface of the bone.

 
Ligaments
At anatomic inspection, the collateral ligaments were clearly identified. They were situated on the radial and ulnar sides of each joint, blending with and reinforcing the capsule. The collateral ligaments included two distinctive bands, which represented the main collateral ligaments and the accessory collateral ligaments. The main collateral ligaments were taut in flexion and relaxed in extension (Fig 4). They arose in depressions on the radial and ulnar sides of the metacarpal head and extended distally toward the base of the proximal phalanx (Fig 5). Transverse T1-weighted spin-echo MR images and arthrograms of the joints in flexion enabled the most complete analysis of the attachments of the main collateral ligaments and their body (grade, 3.7–3.9). No difference in the visualization of these structures was observed when conventional and arthrographic MR images were analyzed. Coronal sequences following contrast agent administration (Fig 6) enabled good visualization (grade, 3.5–3.9) of the proximal and distal attachments of the main collateral ligaments. When extended, the main collateral ligaments had intermediate signal intensity (Fig 6a, 6b). The mean thickness of the main radial collateral ligaments (range, 2.1–2.6 mm) was slightly greater than that of the main ulnar collateral ligaments (range, 1.8–2.1 mm).



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  		Figure 4. Drawing of the collateral ligament complex. The main collateral ligament is relaxed in extension and taut in flexion, and the accessory collateral ligament is taut in extension and more relaxed in flexion.

 


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  		Figure 5a. Transverse views of the MCP joint of the third finger in flexion, with anatomic correlation. T1-weighted spin-echo (a) conventional MR image (500/12) and (b) MR arthrogram (500/12) and (c) the corresponding anatomic section show the proximal attachments (black arrowheads), distal attachments (white arrowheads), and taut body (arrow) of the main collateral ligament.

 


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  		Figure 5b. Transverse views of the MCP joint of the third finger in flexion, with anatomic correlation. T1-weighted spin-echo (a) conventional MR image (500/12) and (b) MR arthrogram (500/12) and (c) the corresponding anatomic section show the proximal attachments (black arrowheads), distal attachments (white arrowheads), and taut body (arrow) of the main collateral ligament.

 


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  		Figure 5c. Transverse views of the MCP joint of the third finger in flexion, with anatomic correlation. T1-weighted spin-echo (a) conventional MR image (500/12) and (b) MR arthrogram (500/12) and (c) the corresponding anatomic section show the proximal attachments (black arrowheads), distal attachments (white arrowheads), and taut body (arrow) of the main collateral ligament.

 


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  		Figure 6a. Coronal views of the MCP joints of the second and third fingers in extension, with anatomic correlation. T1-weighted spin-echo (a) conventional MR image (500/12) and (b) MR arthrogram (500/12) and (c) the corresponding anatomic specimen show the proximal (black arrowheads in a and b) and distal (straight arrows) attachments of the main collateral ligament. Note the heterogeneous signal intensity of the main collateral ligaments. The interosseous tendons (white arrowheads) are well demonstrated. Note the intermetacarpophalangeal spaces (curved arrows in c) between the main collateral ligaments and the interosseous tendons.

 


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  		Figure 6b. Coronal views of the MCP joints of the second and third fingers in extension, with anatomic correlation. T1-weighted spin-echo (a) conventional MR image (500/12) and (b) MR arthrogram (500/12) and (c) the corresponding anatomic specimen show the proximal (black arrowheads in a and b) and distal (straight arrows) attachments of the main collateral ligament. Note the heterogeneous signal intensity of the main collateral ligaments. The interosseous tendons (white arrowheads) are well demonstrated. Note the intermetacarpophalangeal spaces (curved arrows in c) between the main collateral ligaments and the interosseous tendons.

 


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  		Figure 6c. Coronal views of the MCP joints of the second and third fingers in extension, with anatomic correlation. T1-weighted spin-echo (a) conventional MR image (500/12) and (b) MR arthrogram (500/12) and (c) the corresponding anatomic specimen show the proximal (black arrowheads in a and b) and distal (straight arrows) attachments of the main collateral ligament. Note the heterogeneous signal intensity of the main collateral ligaments. The interosseous tendons (white arrowheads) are well demonstrated. Note the intermetacarpophalangeal spaces (curved arrows in c) between the main collateral ligaments and the interosseous tendons.

 
The accessory collateral ligaments (Fig 7) arose in the same depression as the main collateral ligaments but in a more palmar location. Their proximal attachments were not separable. The accessory collateral ligaments were taut in extension and more relaxed in flexion (Fig 4). They extended in a palmar direction and were firmly attached to the PP. Transverse T1-weighted spin-echo MR images and arthrograms of these ligaments in extension enabled the best visualization (grade, 3.8–3.9) of their attachments and body. At MR arthrography, the shape of the body of the ligament was better visualized (grade, 3.9 vs 3.1 at conventional MR imaging) and the ligaments had low signal intensity, as compared with intermediate signal intensity on the conventional MR images (Fig 7a, 7b). The accessory collateral ligament usually was larger on the radial side (range, 1.4–1.9 mm) than on the ulnar side (range, 1.2–1.6 mm). The diameter of this ligament decreased slightly between the second and fifth MCP joints.



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  		Figure 7a. Transverse views of the MCP joints of the second and third fingers in extension, with anatomic correlation. T1-weighted spin-echo (a) conventional MR image (500/12) and (b) MR arthrogram (500/12) and (c) the corresponding anatomic section show the proximal attachments (open arrow), distal attachments (long straight black arrow), and taut body (long straight white arrow) of the accessory collateral ligament. In b, the accessory collateral ligaments are better depicted with intraarticular contrast agent enhancement. The sagittal bands (white arrowheads), interosseous muscles (short black arrow in c) and tendons (short white arrows), PP (curved black arrow), A1 pulleys (black arrowheads), and DTML (curved white arrow in a and c) also are well demonstrated.

 


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  		Figure 7b. Transverse views of the MCP joints of the second and third fingers in extension, with anatomic correlation. T1-weighted spin-echo (a) conventional MR image (500/12) and (b) MR arthrogram (500/12) and (c) the corresponding anatomic section show the proximal attachments (open arrow), distal attachments (long straight black arrow), and taut body (long straight white arrow) of the accessory collateral ligament. In b, the accessory collateral ligaments are better depicted with intraarticular contrast agent enhancement. The sagittal bands (white arrowheads), interosseous muscles (short black arrow in c) and tendons (short white arrows), PP (curved black arrow), A1 pulleys (black arrowheads), and DTML (curved white arrow in a and c) also are well demonstrated.

 


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  		Figure 7c. Transverse views of the MCP joints of the second and third fingers in extension, with anatomic correlation. T1-weighted spin-echo (a) conventional MR image (500/12) and (b) MR arthrogram (500/12) and (c) the corresponding anatomic section show the proximal attachments (open arrow), distal attachments (long straight black arrow), and taut body (long straight white arrow) of the accessory collateral ligament. In b, the accessory collateral ligaments are better depicted with intraarticular contrast agent enhancement. The sagittal bands (white arrowheads), interosseous muscles (short black arrow in c) and tendons (short white arrows), PP (curved black arrow), A1 pulleys (black arrowheads), and DTML (curved white arrow in a and c) also are well demonstrated.

 
The PP was clearly visualized at anatomic inspection. The PP (Fig 3) was a thick, dense structure on the palmar aspect of the MCP joints in the intervals between the accessory collateral ligaments to which they were connected. The PP was firmly inserted into the palmar base of the proximal phalanx. A central distal recess could be seen between two strong attachments (Fig 3a). The PP thinned out proximally into a membranous capsule. A groove was found on the palmar aspect of the flexor tendons, the tendon sheaths of which were held to the side of the groove by the A1 pulley (Fig 7). The deep surface of the PP formed part of the articular surface for the head of the metacarpal bone (Fig 3b). Transverse T1-weighted spin-echo MR images and arthrograms of the joints in extension enabled the best visualization of the axial extent of the PP, the DTML, and the A1 pulley attaching to the PP. Sagittal T1-weighted spin-echo MR arthrograms of the joints in either extension or flexion enabled the best delineation of the shape of the body of the PP (grade, 3.8–4.0), the distal attachments (grade, 3.5–3.6), and the recess (grade, 2.3–3.7 vs 1.0–2.0 on conventional MR images). The proximal attachments usually were not well identified on the midsagittal view; the sagittal plane remained the best for visualization of these structures (grade, 3.0 vs 1.0–1.8). The mean length of the PP was almost identical at the second, third, and fourth MCP joints (11 mm) but substantially shorter at the fifth MCP joint (8 mm). The maximal and minimal thicknesses were about 2.5 and 1.4 mm, respectively, at the second, third, and fourth MCP joints and were relatively smaller at the fifth MCP joint (2.2 and 1.0 mm, respectively).

On the anatomic sections, the DTMLs consisted of three short wide, flattened bands that connected the PP of the second to fifth MCP joints. The lumbrical muscles and the digital vessels and nerves were located on the palmar aspect of the DTML. The interosseous muscles and tendons were located on the dorsal aspect of the DTML. Transverse T1-weighted spin-echo MR imaging or arthrography proved to be the only technique that allowed analysis of these ligaments (grade, 3.0–4.0 vs 1.0 at other sequences). In addition, these ligaments were better seen with the fingers extended than with them flexed. The third bands between the fourth and fifth PPs were never seen as well as the two first bands (grade, 2.0–3.6 vs 3.0–4.0) (Fig 7).

Extensor Hood
All structures of the extensor hood were clearly identified in all specimens. The sagittal bands were thin bands that extended from the common extensor tendons to the junction of the PP and DTML and coursed between the interosseous tendons and the main collateral ligaments (Fig 8). The central digits had a palmar soft-tissue confluence on each side that consisted of the sagittal bands, PP, A1 pulley, and DTML. Conventional and arthrographic transverse T1-weighted spin-echo MR images of the fingers in extension were the best way to analyze the sagittal bands (grade, 3.8–3.9 vs 1.0–2.6 at other sequences).



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  		Figure 8. Transverse T1-weighted spin-echo MR arthrogram (500/12) of the MCP joint of the second and third MCP finger joints shows the fibrous connection (curved arrow) between the proprius and the common extensor tendon, the sagittal bands (arrowheads), the A1 pulley (thin straight arrows), the DTML (open arrows), and the lumbrical muscle (thick straight arrow). The line on the right side of image represents a 1-cm scale.

 
The transverse fibers formed a triangular lamina distal to the sagittal bands (Fig 2). Conventional and arthrographic transverse T1-weighted spin-echo MR images of the fingers in extension were the best way to evaluate these fibers (Fig 9) (grade, 3.0–4.0 vs 1.2–2.2 at other sequences).



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  		Figure 9. Transverse T1-weighted spin-echo MR arthrogram (500/12) 1 cm distal to the MCP joints of the fourth and fifth fingers shows the transverse fibers (curved arrows) arising from the interosseous tendons (straight black arrows) and extending to the extensor tendon (white arrow). The line on the right side of image represents a 1-cm scale.

 
The extensor muscle of the index finger and extensor muscle of the little finger and the corresponding tendons represented a part of the extensor complex of the index and little fingers. Fibrous connections of the extensor hood united the proper and common extensor tendons (Fig 8). Transverse T1-weighted spin-echo MR images and arthrograms were the best way to evaluate the fibrous connections (grade, 2.4–3.8 vs 1.0 at other sequences). An increased visualization grade was noted at MR arthrography (3.0–3.6 vs 2.4–3.8 at conventional MR imaging).

Muscles and Tendons
The digital flexor tendon sheaths began at the level of the metacarpal neck and continued to the distal insertion of the tendon of the deep flexor muscle of the fingers. The tendons of the superficial flexor muscle of the fingers and of the deep flexor muscle of the fingers resided in the sheaths, which were maintained against the PP by the A1 pulley (Fig 7). The A1 pulley attached to the junction of the PP and the DTML. Conventional and arthrographic transverse T1-weighted spin-echo MR images of the joints in extension were the best way to evaluate the tendon sheaths and the A1 pulley (grade, 3.3–3.6 vs 1.0–2.7 at other sequences).

The interosseous muscles and tendons were dorsal to the DTML and inserted into the proximal phalanx, with fibers continuing to the extensor hood. Transverse images provided good visualization of these tendons (Fig 7) (grade, 2.6–4.0 vs 1.3–2.3 at other sequences).

The lumbrical muscles were in a palmar location in relation to the DTML, passed to the radial side of the corresponding MCP joint, and then inserted into the digital extensor mechanism. At the level of the MCP joint, transverse T1-weighted spin-echo MR images and arthrograms were the best way to evaluate these structures (grade, 2.6–4.0 vs 1.3–2.3 at other sequences).

Coronal sections of the joint specimens (Fig 6c) showed intermetacarpophalangeal spaces between the main collateral ligament and the tendons of the interosseous muscles.

Interobserver Correlations and Conventional MR Imaging versus MR Arthrography
The results of interobserver correlations and of conventional MR imaging versus MR arthrography comparisons are detailed in Table 3. According to the results of analysis with the Landis and Koch method (13), both readers had moderate to substantial agreement on all the sequences analyzed. The {kappa} values for arthrography were a little higher than those for conventional MR imaging, with the exception of those at transverse T1-weighted spin-echo imaging.


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  		TABLE 3. Interobserver Correlations and Conventional MR Imaging versus MR Arthrography Comparison

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
REFERENCES
 
To date, few articles on the use of MR imaging in the evaluation of the MCP joints have been published (5,8,9,14,15). To achieve good visualization of the intraarticular and periarticular structures about the MCP joints, the radiologist must pay careful attention to the technical details of the examination. High-spatial-resolution imaging is needed for visualization of small anatomic structures. To achieve this resolution, the images must have an adequate signal-to-noise ratio; thus, the use of a local (ie, wrist or adapted-surface) coil is essential.

Weiss and co-workers (14) observed the general anatomy of these joints, and Erickson et al (9) described some of the small structures in and about these joints. In another investigation, Bodner and co-workers (5) studied the annular pulley of the flexor tendons. Drapé and co-workers investigated the MR imaging appearances of the extensor hood (8) and flexor tendons (15). All of these studies were performed by using customized coils. In our study, all of the important structures in and around the MCP joints were well demonstrated with clinically available equipment. To our knowledge, the role of MR arthrography in the assessment of the MCP joints of the fingers has not been described previously, although Ahn and co-workers (16) achieved high accuracy with MR arthrography in the detection of tears of the ulnar collateral ligament of the thumb.

The main collateral ligaments have a primary role in stabilizing the MCP joint in all modes of joint alignment and especially in flexion (17). Our study results indicate that conventional and arthrographic transverse T1-weighted spin-echo MR images of the joints in flexion allow the most complete analysis. When the MCP joint is extended, the angle of the main collateral ligament relative to the constant magnetic induction field is unpredictable, and the magic angle effect is maximized and can possibly cause increased signal intensity and consequently diminished visualization. An interesting finding was that the radial collateral ligaments are usually thicker than the ulnar collateral ligaments, as was shown in a previous report (10). The accessory collateral ligaments prevent palmar displacement of the proximal phalanx (18). Conventional and arthrographic transverse T1-weighted spin-echo MR images of the joints in extension provided the best visualization of these ligaments. Although not performed in our study, ulnar or radial deviation with the MCP joint in extension probably would have stretched the accessory collateral ligaments and increased their visibility.

The PP prevents hyperextension and dorsal subluxation of the MCP joints (10). Transverse and sagittal T1-weighted spin-echo MR images and arthrograms of the joints in either extension or flexion were the best way to evaluate the PP. The DTMLs allow dorsal and palmar mobility, as well as limited rotation, but they limit medial and lateral mobility (19). Conventional or arthrographic transverse T1-weighted spin-echo MR imaging proved to be the best technique for analysis of these ligaments. The A1 pulley maintains the flexor tendon against the PP (1). Transverse T1-weighted spin-echo MR images and arthrograms of the joints in extension enabled the best evaluation of the tendon sheaths and the A1 pulley. Flexed positions of the MCP joints with tension of the flexor tendons stretch the pulleys and enable one to confirm the integrity of their function. The interosseous and lumbrical muscles and tendons provide stabilization of the MCP joints in full extension (20). Transverse MR images and arthrograms enabled good visualization of these tendons.

Our inspection of coronal slices of the joint specimens revealed characteristics that were compatible with intermetacarpophalangeal spaces between the main collateral ligament and the tendons of the interosseous muscles in the second, third, and fourth spaces. As reported by Jovanovic et al (21), either these spaces are intermetacarpophalangeal bursae, which to our knowledge are not described in any anatomy textbook, or such "bursae" are actually spaces that are limited by recesses of the aponeuroses of the hand.

There were several limitations to this study. First, clinical information was very limited. This is a common problem in cadaveric studies; however, routine radiography enabled the exclusion of substantial osseous abnormalities. Second, the use of anatomic specimens allowed us to place the region of interest exactly in the center of the gantry in the best position for imaging; such a situation is not always possible with patients. Clinically available equipment was used in this study, however. Third, differences in structure elasticity between living and cadaveric tissue, particularly in the setting of joint flexion, were not considered. However, the specimens were placed in the same positions at imaging as patients would be. Fourth, other pulse sequence techniques might render different kinds of information; however, we limited our study to T1-weighted spin-echo sequences to best delineate the anatomy. Finally, although MR arthrography improved visualization of the intraarticular structures of the MCP joints, this technique is not available routinely and is time-consuming, even when only one MCP joint is injected with contrast agent. The clinical feasibility of MR arthrography of the MCP joint requires further analysis.

In conclusion, MR imaging and MR arthrography with commercially available coils enable accurate visualization of the important anatomic structures of and about the MCP joints. Stress images of the joints in flexion are essential for assessment of the collateral ligaments. MR arthrography enhances visualization of the intraarticular elements.


   FOOTNOTES
 
See also the article by Pfirrmann et al (pp 447–452 ) in this issue.

Abbreviations: A1 = first annular, DTML = deep transverse metacarpal ligament, MCP = metacarpophalangeal, PP = palmar plate

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


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 

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