Fast presurgical magnetic resonance imaging of meniscal tears and concurrent subchondral bone marrow lesions. Study of dogs with naturally occurring cranial cruciate ligament rupture.

Meniscal tears and subchondral bone marrow lesions have both been described in dogs with cranial cruciate ligament rupture, but their possible concurrence has not been evaluated. In a population of 14 dogs exhibiting signs of stifle pain with surgically confirmed cranial cruciate ligament rupture, a short presurgical 1.5T magnetic resonance (MR) imaging protocol including dorsal proton density, dorsal T1-weighted gradient recalled echo, and sagittal fat-saturated dual echo sequences was tested to further investigate these features and illustrate meniscal tears. Interobserver agreement for detection of medial meniscal tears (k=0.83) and bone marrow lesions (k=0.87) was excellent. Consensus MR reading allowed detection of nine out of 12 surgically confirmed medial meniscal tears and there was no false positive. All dogs had cruciate ligament enthesis-related bone marrow lesions in the tibia, femur or both bones. Additionally, among the 12 dogs with confirmed medial meniscal tears, subchondral bone marrow lesions were present in the caudomedial (9 dogs) and caudoaxial (11 dogs) regions of the tibial plateau, resulting in odds ratios (13.6, p=0.12, and 38.3, p=0.04, respectively) that had large confidence intervals due to the small group size of this study. The other two dogs had neither tibial bone marrow lesions in these locations nor medial meniscal tears. These encouraging preliminary results warrant further investigation using this clinically realistic preoperative MR protocol. As direct diagnosis of meniscal tears remained challenging in dogs even with high-field MR, identification of associated signs such as subchondral bone marrow lesions might indirectly allow suspicion of an otherwise unrecognized meniscal tear.

Use of routine clinical multimodality imaging in a rabbit model of osteoarthritis--part II: bone mineral density assessment.

OBJECTIVE: To assess bone mineral density (BMD) at different depths from the articular surface in vivo and temporally in a rabbit model of osteoarthritis (OA) using clinical computed tomography (CT) equipment. METHODS: The knee joints of rabbits (N=10 with Anterior cruciate ligament transection (ACLT) and contralateral sham joints, and N=6 unoperated controls) were scanned in a transverse image plane with a single-slice helical CT scanner. BMD was calculated at defined depths from the articular surface to the growth plate in the lateral femoral condyle (LFC), medial femoral condyle (MFC), lateral tibial plateau (LTP) and medial tibial plateau (MTP). Baseline BMD was measured at 2 weeks before surgery, and then repeated at weeks 2, 4 and 8 post-surgery in all 10 operated rabbits, and again at week 12 in five of the operated rabbits and at weeks -2 and 8 in the six control rabbits. RESULTS: In the control joints, BMD decreased with increasing distance into the epiphysis and remained stable over time within each depth. A significant reduction in BMD was observed at week 2 post-operatively in three compartments (LFC, MFC and MTP) in the ACLT joints and persisted to week 12. A modest reduction in BMD occurred in the LTP and MTP of the sham joints at week 12 alone. CONCLUSION: Clinical CT equipment permitted rapid, repeated, in vivo, non-invasive BMD assessment in a rabbit model of OA. A marked BMD reduction was measured with progression of OA until the end point at 12 weeks.

Imaging and histological features of central subchondral osteophytes in racehorses with metacarpophalangeal joint osteoarthritis.

REASONS FOR PERFORMING STUDY: Marginal osteophytes represent a well known component of osteoarthritis in man and animals. Conversely, central subchondral osteophytes (COs), which are commonly present in human knees with osteoarthritis, have not been reported in horses. OBJECTIVES: To describe and compare computed radiography (CR), single-slice computed tomography (CT), 1.5 Tesla magnetic resonance imaging (MRI), and histological features of COs in equine metacarpophalangeal joints with macroscopic evidence of naturally-occurring osteoarthritis. METHODS: MRI sequences (sagittal spoiled gradient recalled echo [SPGR] with fat saturation, sagittal T2-weighted fast spin echo with fat saturation [T2-FS], dorsal and transverse T1-weighted gradient-recalled echo [GRE], and sagittal T2*-weighted gradient echo with fast imaging employing steady state acquisition [FIESTA]), as well as transverse and reformatted sagittal CTI and 4 computed radiographic (CR) views of 20 paired metacarpophalangeal joints were acquired ex vivo. Following macroscopic evaluation, samples were harvested in predetermined sites of the metacarpal condyle for subsequent histology. The prevalence and detection level of COs was determined for each imaging modality. RESULTS: Abnormalities consistent with COs were clearly depicted on MRI, using the SPGR sequence, in 7/20 (35%) joints. They were identified as a focal hypointense protuberance from the subchondral plate into the cartilage, at the palmarodistal aspect (n=7) and/or at the very dorsal aspect (n=2) of the metacarpal condyle. COs were visible but less obvious in 5 of the 7 joints using FIESTA and reformatted sagittal CT, and were not identifiable on T2-FS, T1-GRE or CR. Microscopically, they consisted of dense bone protruding into the calcified cartilage and disrupting the tidemarks, and they were consistently associated with overlying cartilage defects. CONCLUSIONS: Subchondral osteophytes are a feature of osteoarthritis of equine metacarpophalangeal joints and they may be diagnosed using 1.5 Tesla MRI and CT. POTENTIAL RELEVANCE: Central subchondral osteophytes on MRI represent indirect evidence of cartilage damage in horses.

Temporal assessment of bone marrow lesions on magnetic resonance imaging in a canine model of knee osteoarthritis: impact of sequence selection.

OBJECTIVE: To assess the evolution of bone marrow lesions (BMLs) in a canine model of knee osteoarthritis (OA) using three different magnetic resonance imaging (MRI) sequences. DESIGN: Three MRI sequences [coronal, T1-weighted three-dimensional fast gradient recalled echo (T1-GRE), sagittal fat-suppressed 3D spoiled gradient echo at a steady state (SPGR), and sagittal T2-weighted fast spin echo with fat saturation (T2-FS)] were performed at baseline, and at week 4, 8 and 26 in five dogs following transection of the anterior cruciate ligament. The same reader scored (0-3) subchondral BMLs twice, in blinded conditions, according to their extent in nine joint subregions, for all imaging sessions, and independently on the three MRI sequences. Correlation coefficients and Bland-Altman plots evaluated intra-reader repeatability. Readings scores were averaged and the nine subregions were summed to generate global BML scores. RESULTS: BMLs were most prevalent in the central and medial portions of the tibial plateau. Intra-reader repeatability was good to excellent for each sequence (r(s)=0.87-0.97; P<0.001). Maximal intra-reader variability (24%) was reached on T2-FS and was associated to higher scores (P<0.05). Global BML scores increased similarly on all three sequences until week 8 (P<0.05). At week 26, score on T2-FS was decreased, being lower when compared to T1-GRE and SPGR (P<0.05). CONCLUSION: In this canine OA model, the extent of BMLs varies in time on different MRI sequences. Until the complex nature of these lesions is fully resolved, it is suggested that to accurately assess the size and extent of BMLs, a combination of different sequences should be used.

Magnetic resonance imaging can accurately assess the long-term progression of knee structural changes in experimental dog osteoarthritis.

OBJECTIVES: Osteoarthritis (OA) structural changes take place over decades in humans. MRI can provide precise and reliable information on the joint structure and changes over time. In this study, we investigated the reliability of quantitative MRI in assessing knee OA structural changes in the experimental anterior cruciate ligament (ACL) dog model of OA. METHODS: OA was surgically induced by transection of the ACL of the right knee in five dogs. High resolution three dimensional MRI using a 1.5 T magnet was performed at baseline, 4, 8 and 26 weeks post surgery. Cartilage volume/thickness, cartilage defects, trochlear osteophyte formation and subchondral bone lesion (hypersignal) were assessed on MRI images. Animals were killed 26 weeks post surgery and macroscopic evaluation was performed. RESULTS: There was a progressive and significant increase over time in the loss of knee cartilage volume, the cartilage defect and subchondral bone hypersignal. The trochlear osteophyte size also progressed over time. The greatest cartilage loss at 26 weeks was found on the tibial plateaus and in the medial compartment. There was a highly significant correlation between total knee cartilage volume loss or defect and subchondral bone hypersignal, and also a good correlation between the macroscopic and the MRI findings. CONCLUSION: This study demonstrated that MRI is a useful technology to provide a non-invasive and reliable assessment of the joint structural changes during the development of OA in the ACL dog model. The combination of this OA model with MRI evaluation provides a promising tool for the evaluation of new disease-modifying osteoarthritis drugs (DMOADs).

Detection of rib trauma in newborn foals in an equine critical care unit: a comparison of ultrasonography, radiography and physical examination.

REASONS FOR PERFORMING STUDY: Previous studies have shown that in man ultrasonography is more accurate than radiography for detecting rib fractures. OBJECTIVES: To describe clinical, radiographic and ultrasonographic findings related with rib fractures in newborn foals in an equine critical care unit; and to compare diagnostic accuracy of ultrasonography to radiography. METHODS: A prospective ultrasonographic study was performed on 29 foals presented to the emergency unit. This study was performed at the Centre Hospitalier Universitaire Vétérinaire (CHUV), University of Montreal. Physical examination as well as radiographic and ultrasonographic examinations were performed. RESULTS: Thoracic radiographs revealed 10 rib fractures in 5 of 26 (19%) foals. Ultrasonography revealed 49 fractures in 19 of 29 (65%) foals of which fillies (n = 13; 68%) were significantly over represented as were fractures to the left thorax (n = 15; 78%). Seventeen of 19 foals (90%) had rib fractures located 3 cm or less from the costochondral junction, the distal part of the rib being displaced laterally in all cases. In 2 foals, where both thoracic radiographs and ultrasonography detected rib fractures, the site of fractures was located on the mid portion of the rib. Rib fractures were detected only by thoracic radiographs in one foal. Sixty-five percent (32/49) of fractured ribs had a moderate displacement (1-4 mm). CONCLUSIONS: Rib fractures are seen frequently in newborn foals in equine critical care units. Ultrasonography is more accurate than radiography and reveals fractures in most patients presented in emergency. The position (costochondral junction) of rib fractures and of the fragments suggest that most thoracic trauma probably occurs during parturition. POTENTIAL RELEVANCE: Ultrasound imaging increases awareness and improves the diagnosis of rib fractures in newborn foals.