Ultrasonographic Examination of Joints

Chapter 17 Ultrasonographic Examination of Joints



Ultrasonography has become an essential imaging technique for assessing joint lesions.1-6 It provides information complementary to radiography but does have some limitations. Ultrasonography requires a precise knowledge of anatomy, not only bone anatomy,4 and a systematic approach. Examining the joints of the distal part of the limb is physically uncomfortable for the imager and is time-consuming: complete examination of a joint may take up to 30 minutes. Quick examination of joints requires several years of daily practice.


The indications for ultrasonographic examination of equine joints include synovial fluid distention, local swelling, pain on passive manipulation of the joint, improvement in lameness after intraarticular or perineural analgesia, and positive radiological or scintigraphic findings. The area to be examined should be clipped, not shaved, and washed with hot water. High-resolution transducers (7.5- to 13-MHz linear probes) and a standoff pad are used for superficial structures. Convex array 2.5- to 5-MHz transducers are preferable for deeper structures. Both left and right joints should be examined to improve sensitivity and specificity. The image quality depends not only on the frequency of the transducer but also on the quality of the machine (from treatment of the signal to display on the monitor) and the skill of the operator in placing and orienting the transducer.


A comprehensive description of all joints cannot be given in this book. The fetlock joint is a model for a general approach to ultrasonography of joints because of its simple anatomy. Some aspects of examination of the stifle and hock also are presented.



Fetlock


Each aspect of the joint should be examined systematically using 7.5- to 13-MHz linear transducers and a thin standoff pad.



Dorsal Aspect


Figure 17-1 shows normal ultrasonographic anatomy.4,5 In normal fetlock joints the articular capsule is echogenic (except if too relaxed), and the articular margins of the proximal phalanx and the condyles of the third metacarpal bone (McIII) are smooth.



Ultrasonography is a useful technique for the differential diagnosis of soft tissue injuries on the dorsal aspect of the fetlock joint. These lesions include subcutaneous swelling or abscess, bursitis of the subtendonous bursa of the extensor tendons, extensor tendonitis, capsulitis, synovial fluid distention of the dorsal recess of the metacarpophalangeal joint (Figure 17-2), and chronic proliferative synovitis of the proximodorsal synovial fold of this joint (Figure 17-3). Thinning, fibrillation, and fissures of the articular cartilage of the dorsal and distal aspects of the condyle of the McIII can be identified with high-resolution transducers. Subchondral bone lesions can sometimes be detected before they are visible radiologically. Ultrasonography may be more sensitive than radiography for detection of the site and number of osteochondral fragments.7





Jun 4, 2016 | Posted by in EQUINE MEDICINE | Comments Off on Ultrasonographic Examination of Joints
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