The MRI and CT images from 7 sections in 3 planes were selected and adjoined to their corresponding anatomic slices: 2 in the sagittal plane, 1 in the dorsal plane and 4 in the transverse plane (Fig. 1). For each anatomic section, a corresponding MRI and CT images were selected on the basis of similarity. The clinically osseous and soft tissue structures of the bovine carpus were identified and labeled on the anatomic slice then subsequently located on the corresponding CT and MRI images. Each figure is a composite of four images corresponding to the adjoined gross anatomic section, MRI, CT bone window and CT soft tissue window. The transverse and dorsal images were oriented with lateral to the right and sagittal images were oriented with dorsal to the right. The representative sagittal images were selected laterally at the level of the ulnar carpal bone (Fig. 2) and medially at the level of the radial carpal bone (Fig. 3). A dorsal image was chosen at the level of the collateral ligaments (Fig. 4). The transverse images were selected at the level of the distal radius (Fig. 5), proximal row of carpal bones (Fig. 6), distal row of carpal bones (Fig. 7), and the proximal metacarpal region (Fig. 8).
On the transverse images at the level of the distal radius (Fig. 5), the cortical and medullary bone of the radius and ulna were clearly depicted on the CT bone window. The cortex had low signal intensity and medulla had heterogeneous high signal intensity, on the MRI images. On the CT soft tissue window: the ulnar, humeral and radial heads of the deep digital flexor muscle, superficial and deep parts of the superficial digital flexor muscle; and the extensor carpi ulnaris muscle were hypodense compared with their tendinous parts. The tendons of common digital extensor, flexor carpi ulnaris, extensor carpi radialis, lateral digital extensor and flexor carpi radialis muscles were hyperattenuated on the CT images and markedly hypointense on the MRI images, compared with the surrounding soft tissues. The long and short (proximal limb) medial collateral carpal ligaments were identified adjacent to the medial edge of the radius and had low signal intensity on the MRI images and appeared as hyperattenuated oval structures on the CT images.
At the level of the proximal row of carpal bones (Fig. 6), the radial, intermediate, ulnar and accessory carpal bones were clearly depicted on the CT images. The cortices had low signal intensity and cancellous bone had heterogeneous high signal intensity, on the MRI images. The long and short lateral collateral ligaments were identified adjacent to the ulnar carpal bone as oval hyperattenuated structures on CT images and of low signal intensity on the MRI images. The extensor and flexor tendons were more or less oval in shape with low signal intensity on MRI images and hypodense on the CT images. At this level, the superficial and deep digital flexor muscles had heterogeneous signal intensity on the MRI images and heterogeneous density on the CT images (mixed tendinous and muscle tissue). The intercarpal ligaments were recognized between the carpal bones as lines of low to moderate signal intensity on the MRI images and heterogeneous density on the CT images. The synovial fluid had intermediate signal intensity on the MRI images.
At the level of the distal row of carpal bones (Fig. 7), the fused second and third, and fourth carpal bones were well defined. The intercarpal ligaments were seen as parallel fibers of low signal intensity separated by synovial fluid pockets of intermediate signal intensity. The long lateral collateral ligament appeared thicker than further proximally and had heterogeneous low signal intensity with clear margins. The medial collateral ligament had also heterogeneous signal intensity, and was larger, more elongated, and spreaded around the medial side of the fused second and third carpal bone. The superficial and deep digital flexor tendons had low signal intensity. The flexor retinaculum was seen as a narrow band of homogeneous medium to low signal intensity. Synovial fluid was observed between the carpal bones, between the intercarpal ligament fibers, and on the palmarolateral side of the middle carpal joint.
At the level of the proximal metacarpal region (Fig. 8), the third, fourth and fifth metacarpal bones were visible. The lateral collateral ligament appeared thin and elongated at this level with heterogeneous density and signal intensity on the CT and MRI images, respectively. The medial collateral ligament became thinner more palmar and spreaded around the mediopalmar side of the third metacarpal bone. The extensor carpi radialis tendon was less well defined and had heterogeneous signal intensity.
On the sagittal slices (Figs. 1, 2), the joint spaces of the antebrachiocarpal, middle intercarpal joint and carpometacarpal joints were well depicted. On the CT bone window, excellent differentiation between cortical, subchondral, and cancellous bone was seen. The trabecular pattern of the cancellous bone was well depicted. On the CT soft tissue window, the superficial and deep digital flexor tendons were clearly recognized along the disto-palmar aspect of the carpus. On the lateral parasagittal slice, ligaments of the accessory carpal bone and the insertion of the flexor carpi ulnaris tendon could be evaluated. Detectable on the medial parasagittal slice were the superficial and deep digital flexor muscles with its transition into tendons as well as the changes of signal intensity from muscle to tendon.
On the dorsal slice (Fig. 3), the distal radius, contours of the radial trochlea, joint spaces, and associated inter-osseus foramina of the ulnar, intermediate, radial, fused second and third, fourth carpal bones were clearly visualized on the CT bone window images. On the CT soft tissue window images, the origin of the long limbs of the collateral ligaments from the ulnar and radial styloid processes could be evaluated and followed from proximal to distal. The short deep collateral ligaments were partially visible as they ran in a nearly horizontal (dorsoproximal-palmarodistal) direction. The inter-carpal ligaments were recognized at the level of the associated joint spaces. The articular surfaces and joint spaces of the carpal joints were clearly defined. The median artery and vein were deeply located medial to the deep part of the superficial digital flexor tendon and appeared as circular structures, of medium to low signal intensity. The radial vein was seen running subcutaneously on the palmaro-medial aspect, accompanied laterally by the radial artery caudal to the flexor carpi radialis tendon (Figs. 5–8).