Objective. To confirm preclinical data suggesting that doxycycline can slow the progression of osteoarthritis (OA). The primary outcome measure was joint space narrowing (JSN) in the medial tibiofemoral compartment.Methods. In this placebo-controlled trial, obese women (n ‫؍‬ 431) ages 45-64 years with unilateral radiographic knee OA were randomly assigned to receive 30 months of treatment with 100 mg doxycycline or placebo twice a day. Tibiofemoral JSN was measured manually in fluoroscopically standardized radiographic examinations performed at baseline, 16 months, and 30 months. Severity of joint pain was recorded at 6-month intervals.Results. Seventy-one percent of all randomized subjects completed the trial. Radiographs were obtained from 85% of all randomized subjects at 30 months. Adherence to the dosing regimen was 91.8% among subjects who completed the study per protocol. After 16 months of treatment, the mean ؎ SD loss of joint space width in the index knee in the doxycycline group was 40% less than that in the placebo group (0.15 ؎ 0.42 mm versus 0.24 ؎ 0.54 mm); after 30 months, it was 33% less (0.30 ؎ 0.60 mm versus 0.45 ؎ 0.70 mm). Doxycycline did not reduce the mean severity of joint pain, although pain scores in both treatment groups were low at baseline and remained low throughout the trial, suggesting the presence of a floor effect. However, the frequency of followup visits at which the subject reported a >20% increase in pain in the index knee, relative to the previous visit, was reduced among those receiving doxycycline. In contrast, doxycycline did not have an effect on either JSN or pain in the contralateral knee. In both treatment groups, subjects who reported a >20% increase in knee pain at the majority of their followup visits had more rapid JSN than those whose pain did not increase.Conclusion. Doxycycline slowed the rate of JSN in knees with established OA. Its lack of effect on JSN in the contralateral knee suggests that pathogenetic mechanisms in that joint were different from those in the index knee.In the present report, we describe the results of a randomized, placebo-controlled, double-blind trial of the tetracycline antibiotic, doxycycline, in subjects with knee osteoarthritis (OA). Selection of doxycycline as a potential disease-modifying OA drug was based not on the premise that OA is an infectious disease, but rather on results of in vitro studies showing 1) that doxycycline inhibited the degradation of type XI collagen, one of the minor collagens of articular cartilage, by 72-kd gelati-

Multisection computed tomography (CT) was introduced in 1992 with the advent of dual-section-capable scanners and was improved in 1998 following the development of quad-section technology. With a recent increase in gantry speed from one to two revolutions per second, multisection CT scanners are now up to eight times faster than conventional single-section helical CT scanners. The benefits of quad-section CT relative to single-section helical CT are considerable. They include improved temporal resolution, improved spatial resolution in the z axis, increased concentration of intravascular contrast material, decreased image noise, efficient x-ray tube use, and longer anatomic coverage. These factors substantially increase the diagnostic accuracy of the examination. The multisection CT technique has enabled faster and superior evaluation of patients across a wide spectrum of clinical indications. These include isotropic viewing, musculoskeletal applications, use of multiplanar reformation in special situations, CT myelography, long coverage and multiphase studies, CT angiography, cardiac scoring, evaluation of brain perfusion, imaging of large patients, evaluation of acute chest pain or dyspnea, virtual endoscopy, and thin-section scanning with retrospective image fusing. Multisection CT is superior to single-section helical CT for nearly all clinical applications.

Radiographic evaluation of navicular syndrome is problematic because of its inconsistent correlation with clinical signs. Scintigraphy often yields false positive and false negative results and diagnostic ultrasound is of limited value. Therefore, we assessed the use of computed tomography and magnetic resonance imaging in a horse with clinical and radiographic signs of navicular syndrome. Cadaver specimens were examined with spiral computed tomographic and high-field magnetic resonance scanners and images were correlated with pathologic findings. Radiographic changes consisted of bony remodeling, which included altered synovial fossae, increased medullary opacity, cyst formation and shape change. These osseous changes were more striking and more numerous on computed tomographic and magnetic resonance images. They were most clearly defined with computed tomography. Many osseous changes seen with computed tomography and magnetic resonance imaging were not radiographically evident. Histologically confirmed soft tissue alterations of the deep digital flexor tendon, impar ligament and marrow were identified with magnetic resonance imaging, but not with conventional radiography. Because of their multiplanar capability and tomographic nature, computed tomography and magnetic resonance imaging surpass conventional radiography for navicular imaging, facilitating earlier, more accurate diagnosis. Current advances in imaging technology should make these imaging modalities available to equine practitioners in the future.

Cross-sectional imaging utilizing computed tomography (CT) and magnetic resonance (MR) imaging have become routine components in the imaging assessment of patients with musculoskeletal disease. Unfortunately, in the setting of a postoperative orthopedic patient with associated orthopedic metallic instrumentation, these imaging techniques are prone to artifacts resulting in image quality degradation. An understanding of the physical basis of such metal-related artifacts, and their appearance on CT and MR imaging, has led investigators to the implementation of a series of techniques and modifications to imaging protocols to decrease CT and MR imaging artifacts in the vicinity of metallic instrumentation. Utilizing such modified imaging techniques, consistent, improved CT and MR image quality may be achieved in imaging of the postoperative orthopedic patient.

Multidetector computed tomography (CT) is an excellent way to supplement the radiographic evaluation of problematic hip prostheses. Multidetector CT is well suited for assessing periprosthetic bone, determining precise acetabular cup position, and evaluating periprosthetic fluid collections or ossified masses. Metal implants pose a number of challenges in the performance and interpretation of CT examinations. However, metal artifacts can be minimized by decreasing the detector collimation and pitch, increasing the kilovolt peak and milliampere-seconds, and using appropriate reconstruction algorithms and section thickness. Image interpretation requires a basic understanding of hip reconstruction and hip implants, as well as use of a systematic method of analysis that incorporates prior radiographic findings and CT findings. Radiologists must be familiar with the normal and abnormal CT appearances of hip prostheses and be able to recognize common complications on CT scans.