CT ASSESSMENT OF OSTEOARTHRITIS IN THE STIFLE JOINT OF DOGS WITH RUPTURED CRANIAL CRUCIATE LIGAMENT

Introduction/Purpose: Diagnostic Imaging techniques are used to assess osteoarthritic changes for setting prognosis and treatment in cases of CCL rupture. MRI is considered the “gold standard” to visualize damages of ligaments, menisci and cartilages1. Radiography is a well-defined technique used for planning correctional surgery but it has a lower sensitivity in demonstrating early osteoarthritic changes2. Ultrasonography is reported as a valuable tool to visualize osteophytes, intra-articular effusion, lesions of menisci and ligaments3, but it permits only a limited visualization of these structures. CT is superior to radiography and ultrasonography in assessing the stifle joint OA, since the lack of superimpositions and the higher contrast resolution. Therefore, the aim of this study was to assess osteoarthritic changes CT in case of CCL rupture. Material and Methods: 19 dogs of various breeds, 7 male and 12 females, mean age 5,7 years (range: 8 mt – 12 y), with clinical signs of unilateral (12 cases) or bilateral (7 cases) CCL rupture underwent CT studies of the stifle joints. In all dogs, the diagnosis of CCL rupture was confirmed at surgery. The duration of clinical signs varied from 5 days to 6 months with a mean chronicity of 1,2 months. CT studies were performed with a third generation scanner (GE Pace Plus) on dogs in dorsal recumbency with hind limbs caudally extended. 1mm thickness contiguous slices from suprapatellar recess to proximal tibial epiphysis were made. CT studies evaluation was made on transverse slices and on multiplanar reconstructions (MPR) using both bone (WW 1600, WL 400) and soft tissue (WW 500, WL 0) windows. Results: The most frequent CT findings visible on transverse images were: condylar and trochlear osteophytes (100%); capsular thickenings (88,9%); enthesiophytes of the tibial extensor muscle groove (83,3%); caudal dislocation of popliteal sesamoid (72,2%); intra-articular effusion (68,7%); subchondral sclerosis of femoral and tibial condyles (30%); synovial cysts (11,1%). MPR permits visualization of caudal cruciate ligament in all the stifle joints while CCL was visible only when it was intact. Medial meniscus damages, i.e. protrusion and/or tears, were visible in 21% of cases. Discussion/Conclusion: CT demonstrated to be an accurate technique that permits a good visualization of many of the ostheoartrosic changes secondary to CCL rupture. More of these changes, i.e. small enthesiophytes or osteophytes, capsular fluid distension or thickening, synovial cysts and caudal dislocation of popliteal sesamoid, are difficult to visualize on radiographs. On MPR images, cruciate ligaments appear as tape-shaped structures, relatively hyperdense compared to the surrounding hypodense fat and synovial fluid. Caudal cruciate ligament is visualized in the sagittal plane while CCL in an oblique parasagittal plane. The menisci are difficult to visualize also on MPR images. Our results demonstrate that, when MRI is not available, CT could be a valuable choice for the assessment of the osteoarthritic changes secondary to CCL rupture in dogs.