Assessment of knee cartilage in cadavers with dual-detector spiral CT arthrography and MR imaging

Ultrasound Imaging in Knee Osteoarthritis: Current Role, Recent Advancements, and Future Perspectives

While conventional radiography and MRI have a well-established role in the assessment of patients with knee osteoarthritis, ultrasound is considered a complementary and additional tool. Moreover, the actual usefulness of ultrasound is still a matter of debate in knee osteoarthritis assessment. Despite that, ultrasound offers several advantages and interesting aspects for both current clinical practice and future perspectives. Ultrasound is potentially a helpful tool in the detection of anomalies such as cartilage degradation, osteophytes, and synovitis in cases of knee osteoarthritis. Furthermore, local diagnostic and minimally invasive therapeutic operations pertaining to knee osteoarthritis can be safely guided by real-time ultrasound imaging. We are constantly observing a growing knowledge and awareness among radiologists and other physicians, concerning ultrasound imaging. Ultrasound studies can be extremely useful to track the response to various therapies. For this specific aim, tele-ultrasonography may constitute an easy tool aiding precise and repeated follow-up controls. Moreover, raw radio-frequency data from US backscattering signals contain more information than B-mode imaging. This paves the way for quantitative in-depth analyses of cartilage, bone, and other articular structures. Overall, ultrasound technologies and their rapid evolution have the potential to make a difference at both the research and clinical levels. This narrative review article describes the potential of such technologies and their possible future implications.

Diagnosis of osteochondral lesions of the talus on Dual-layer spectral detector CT arthrography: clinical feasibility of virtual noncontrast images

AIM

To compare the image quality of virtual noncontrast (VNC) and true noncontrast (TNC) CT images and to evaluate the clinical feasibility of VNC CT images for assessing osteochondral lesions of the talus (OLTs).

MATERIALS AND METHODS

Forty-five OLT patients who underwent ankle CT arthrography (CTA) using dual-layer spectral detector CT were enrolled. Reconstruction of VNC and three-dimensional volume rendering images was performed. Afterward, image noise, the signal-to-noise ratio (SNR), and the contrast-to-noise ratio (CNR) were measured. For the subjective evaluation, two board-certified musculoskeletal radiologists [R2-1] assessed spatial resolution, overall image quality, and lesion conspicuity. The accuracy rate for OLT grading was determined in 23 patients who underwent arthroscopic surgery.

RESULTS

While VNC images showed significantly less noise than TNC images, TNC images showed better SNRs and CNRs (p<.01). In the subjective analysis, TNC images showed better overall image quality (p<.001). For the 3D volume rendering images, VNC images scored significantly higher for lesion conspicuity (p<.001). The accuracy rates of CTA and CTA with VNC images for OLT grading were 79.2% and 83.3%, respectively. Regarding confidence level, when CTA and VNC images were evaluated together, the confidence level was significantly higher than that when only CTA images were evaluated (p<.001).

CONCLUSION

VNC imaging can provide better confidence level of OLT grading and evaluation of the integrity of the subchondral bone plate when combined with conventional CTA without additional radiation dose to the patient. In addition, VNC images-based 3D volume rendering reconstruction would be helpful for preoperative planning in OLT patients.

Sodium fluoride PET/CT with arthrography for cartilage evaluation of the knee

The presence of healthy cartilage in the knee joint, featuring smooth articular surfaces, is crucial for normal physiological knee function. However, noninvasive in-vivo assessment of cartilage quality in the knee remains challenging and has not been thoroughly investigated. We aimed to illustrate two clinical cases, a 62-year-old male and a 67-year-old male, presented to the orthopaedic outpatient clinic with severe knee complaints. The novel combination of sodium fluoride-18 positron emission tomography/computed tomography and intra-articular injection of a contrast agent (Na[18F]F-PET/CT arthrography) was performed to evaluate cartilage defects of the knee as part of a prospective patient study. The lesion size observed on the Na[18F]F-PET was substantially larger compared to the findings on CT. This might indicate that Na[18F]F-PET/CT arthrography was able to image osseous and chondral pathological changes in an early stage and in a single procedure. Na[18F]F-PET/CT arthrography is a promising imaging technique and might extend the diagnostic potential of nuclear and radiological imaging in the evaluation of cartilage defects.

Retrospective study of patellar fractures and damage of accessory soft tissue based on MRI

BACKGROUND

To better understand the pathophysiological mechanisms of patellar fractures, MRI was utilized to identify the imaging signs of various types of patellar fractures.

METHODS

A retrospective study was performed using MRI images of 52 patients with patellar fractures. Observing the development of patellar and femoral morphology and the imaging manifestations of different fracture types, such as fracture displacement, and damage to accessory ligaments, tendons, and meniscus, type of joint cavity effusion, and damage to surrounding accessory bones were identified.

RESULTS

There were 21 tangential fractures (40.4%), 8 transverse fractures (15.4%), 8 longitudinal fractures (15.4%), 4 oblique fractures (7.7%), and 11 comminuted fractures (21.2%) among the 52 patients with patellar fracture. Tangential fractures begin at a younger age than the other four forms of fractures. When tangential fractures were compared to other types of fractures, medial patellar retinaculum and anterior and posterior cruciate ligament injuries were statistically significant (P< 0.05). The detection rate of trochlear dysplasia, type II and type III patellar was higher in patients with tangential fractures than in other fractures.

CONCLUSIONS

Tangential fractures are less common to cause anterior and posterior cruciate ligament injuries than other types of fractures, but they are more likely to cause medial patellar retinaculum injuries.

Imaging Biomarkers of Osteoarthritis

Currently no disease-modifying osteoarthritis drug has been approved for the treatment of osteoarthritis (OA) that can reverse, hold, or slow the progression of structural damage of OA-affected joints. The reasons for failure are manifold and include the heterogeneity of structural disease of the OA joint at trial inclusion, and the sensitivity of biomarkers used to measure a potential treatment effect.This article discusses the role and potential of different imaging biomarkers in OA research. We review the current role of radiography, as well as advances in quantitative three-dimensional morphological cartilage assessment and semiquantitative whole-organ assessment of OA. Although magnetic resonance imaging has evolved as the leading imaging method in OA research, recent developments in computed tomography are also discussed briefly. Finally, we address the experience from the Foundation for the National Institutes of Health Biomarker Consortium biomarker qualification study and the future role of artificial intelligence.

CT in osteoarthritis: its clinical role and recent advances

Computed tomography (CT) is a widely available imaging method and considered as one of the most reliable techniques in bone assessment. Although CT has limited tissue contrast and needs radiation exposure, it has several advantages like fast scanning time and high spatial resolution. In this regard, CT has unique roles in osteoarthritis (OA) and its variable utilities have been reported. Hence, this review highlights the clinical role of CT in OA of representative joints. In addition, CT showed the several technical advancements recently, for example, acquiring the CT image with standing, obtaining the dual-energy data, and novel photon-counting detector development. Therefore, the recent studies and potential utility of these new CT systems in OA are also discussed.

Imaging in Osteoarthritis

Osteoarthritis (OA) is the most frequent form of arthritis with major implications on both individual and public health care levels. The field of joint imaging, and particularly magnetic resonance imaging (MRI), has evolved rapidly due to the application of technical advances to the field of clinical research. This narrative review will provide an introduction to the different aspects of OA imaging aimed at an audience of scientists, clinicians, students, industry employees, and others who are interested in OA but who do not necessarily focus on OA. The current role of radiography and recent advances in measuring joint space width will be discussed. The status of cartilage morphology assessment and evaluation of cartilage biochemical composition will be presented. Advances in quantitative three-dimensional morphologic cartilage assessment and semi-quantitative whole-organ assessment of OA will be reviewed. Although MRI has evolved as the most important imaging method used in OA research, other modalities such as ultrasound, computed tomography, and metabolic imaging play a complementary role and will also be discussed.

Three-dimensional analysis for quantification of knee joint space width with weight-bearing CT: comparison with non-weight-bearing CT and weight-bearing radiography

OBJECTIVE

To compare computer-based 3D-analysis for quantification of the femorotibial joint space width (JSW) using weight-bearing cone beam CT (WB-CT), non-weight-bearing multi-detector CT (NWB-CT), and weight-bearing conventional radiographs (WB-XR).

DESIGN

Twenty-six participants prospectively underwent NWB-CT, WB-CT, and WB-XR of the knee. For WB-CT and NWB-CT, the average and minimal JSW was quantified by 3D-analysis of the minimal distance of any point of the subchondral tibial bone surface and the femur. Associations with mechanical leg axes and osteoarthritis were evaluated. Minimal JSW of WB-CT was further compared to WB-XR. Two-tailed p-values of <0.05 were considered significant.

RESULTS

Significant differences existed of the average medial and lateral JSW between WB-CT and NWB-CT (medial: 4.7 vs 5.1 mm [P = 0.028], lateral: 6.3 vs 6.8 mm [P = 0.008]). The minimal JSW on WB-XR (medial:3.1 mm, lateral:5.8 mm) were significantly wider compared to WB-CT and NWB-CT (both medial:1.8 mm, lateral:2.9 mm, all p < 0.001), but not significantly different between WB-CT and NWB-CT (all p ≥ 0.869). Significant differences between WB-CT and NWB-CT existed in participants with varus knee alignment for the average and the minimal medial JSW (p = 0.004 and p = 0.011) and for participants with valgus alignment for the average lateral JSW (p = 0.013). On WB-CT, 25% of the femorotibial compartments showed bone-on-bone apposition, which was significantly higher when compared to NWB-CT (10%,P = 0.008) and WB-XR (8%,P = 0.012).

CONCLUSION

Combining WB-CT with 3D-based assessment allows detailed quantification of the femorotibial joint space and the effect of knee alignment on JSW. WB-CT demonstrates significantly more bone-on-bone appositions, which are underestimated or even undetectable on NWB-CT and WB-XR.

[MR and CT arthrography in cartilage imaging : Indications and implementation]

BACKGROUND

The imaging of chondral pathologies is an essential part in the work-up of acute and chronic joint diseases. Besides conventional MR imaging, CT and MR arthrography are well-established methods in evaluating articular cartilage. The application of these techniques requires knowledge of indications and safe injection procedures by the performing radiologist.

PURPOSE

Our goal is to describe the techniques of cross-sectional arthrographies of different joints, give an overview of general and joint-specific considerations for practical application as well as provide typical indications for cartilage imaging.

MATERIALS AND METHODS

A selective PubMed literature search concerning "arthrography", "CT arthrography", "MR arthrography", "arthrography cartilage", "arthrography wrist", "arthrography elbow", "arthrography shoulder", "arthrography hip", "arthrography knee", "arthrography ankle", "arthrography complications", "arthrography imaging guidance" "osteochondral lesion", "cartilage imaging" and "cartilage lesion" was performed.

RESULTS AND CONCLUSION

CT and MR arthrography are valuable and safe tools in cartilage imaging. They are useful to verify and specify chondral pathologies, usually after conventional MR imaging, and have an important role in evaluating the stability and therefore in therapeutic decision making of osteochondral lesions. CT arthrography is not only a substitute technique in case of MR contraindications, it can be advantageous in small joints (wrist, elbow, ankle) compared to MR arthrography due to its higher image resolution. Fluoroscopic guided joint puncture is still the most commonly used image guidance method, but the role of ultrasound is steadily increasing. Joint traction in MR arthrography is a promising technique to improve cartilage visualization, though it is not yet used in clinical routine imaging.

Image-Guided Chondrocyte Harvesting for Autologous Chondrocyte Implantation: Initial Feasibility Study with Human Cadaver and Pilot Clinical Experience

Background:

Autologous chondrocyte implantation (ACI), a promising modality for repairing full-thickness cartilage defects, requires 2 consecutive arthroscopic procedures for chondrocyte harvesting and implantation. In the present study, we assessed the feasibility and efficacy of image-guided chondrocyte harvesting as an alternative to arthroscopic biopsy.

Methods:

We induced full-thickness cartilage defects in 10 human cadaveric knees. Computed tomographic arthrography (CTA) was performed following the intra-articular administration of Omnipaque 350 to measure the diameters of the induced cartilage defects. Subsequently, 2 independent operators conducted CTA-guided chondrocyte harvesting (from the medial and lateral trochlear ridges) in each knee. The time for chondrocyte harvesting, accuracy (distance between the predefined target on CTA and the final insertion site of the needle), and number of needle readjustments were recorded. In the institutional review board-approved clinical study, informed consent was obtained and chondrocyte harvesting was performed both with use of a conventional arthroscopic biopsy method and with use of a needle through an arthroscopy access site in 10 subjects for whom ACI was indicated. The samples were processed and cultured blindly, and the quantity and quality of the samples were determined.

Results:

CTA measurements of full-thickness cartilage defects showed high to perfect absolute agreement and consistency when compared with direct measurements (overall interclass correlation coefficient, 0.933 to 0.983; p < 0.05). For both operators, image-guided chondrocyte harvesting from the lateral ridge was more accurate (p = 0.007 and 0.040) and faster (p = 0.056 and 0.014) in comparison with harvesting from the medial ridge. In the clinical study, no significant difference was observed for the growth index of samples between the needle-harvest and conventional methods (p = 0.897).

Conclusions:

CTA can be used for precise measurement of full-thickness cartilage defects. Image-guided chondrocyte harvesting is a viable alternative to traditional arthroscopic biopsy for ACI.

Clinical Relevance:

We recognize the current pivotal role of arthroscopic biopsy, as a part of ACI, for chondrocyte harvesting as well as for delineating the nature of the lesion. However, on the basis of our results, image-guided chondrocyte retrieval may obviate the need for arthroscopic biopsy in some patients in the future.

The comparison of direct magnetic resonance arthrography with volumetric interpolated breath-hold examination sequence and multidetector computed tomography arthrography techniques in detection of talar osteochondral lesions

Objective

The aim of this study was to compare additive diagnostic values of magnetic resonance (MR) arthrography with volumetric interpolated breath-hold examination (VIBE) sequence and multidetector computed tomography (MDCT) arthrography for diagnosis and grading of talar osteochondral lesions.

Methods

MDCT arthrography and MR arthrography with three dimensional VIBE sequence were performed in 27 patients. Findings of MR arthrography and MDCT arthrography images were compared with arthroscopic findings. Sensitivity, specificity, and accuracy rates were calculated for both MR arthrography and MDCT arthrography imaging findings.

Results

For grade I osteochondral lesions; sensitivity, specificity and accuracy rates of MR arthrography were 95%, 73%, 90%, respectively; For grade I osteochondral lesions; sensitivity, specificity and accuracy rates of MDCT arthrography were 96%, 79%, 81%. For grade IV osteochondral lesions; sensitivity, specificity and accuracy rates of MDCT arthrography and MR arthrography were 100%. For grade II lesions, the sensitivity, specificity and accuracy rates of the MR arthrography were 80%, 76%, 77%, respectively; for grade III lesions, the sensitivity, specificity and accuracy rates of the MR arthrography were 78%, 68%, 75%. For grade II osteochondral lesions; the sensitivity, specificity and accuracy rates of the MDCT arthrography were 91%, 81%, 86%; for grade III osteochondral lesions; the sensitivity, specificity and accuracy rates of the MDCT arthrography were 90%, 83%, 89%; For grade II and III osteochondral lesions, MDCT arthrography had higher sensitivity, specificity and accuracy rates than MR arthrography. MDCT arthrography had higher diagnostic performance than MR arthrography for detection of grade II and III lesions (p = 0.041 and p = 0.038, respectively).

Conclusion

MDCT arthrography appears to be more reliable than MR arthrography with three dimensional VIBE sequence for accurate detection and grading of osteochondral lesions.

Level of evidence

Level III, Diagnostic Study.

CT arthrography visualizes tissue growth of osteochondral defects of the talus after microfracture

PURPOSE

Little is known about the arthroscopic or radiographic outcomes after arthroscopic microfracture of osteochondral lesions of the talus (OLTs). The purpose of this study was to investigate tissue growth after arthroscopic microfracture of OLTs using computed tomography arthrography (CTA) and to identify the relationship between CTA findings and clinical outcomes. We hypothesized that the morphology of the repaired tissue would be similar to that of normal anatomy and correlate with the clinical outcomes.

METHODS

Forty-two ankles treated using arthroscopic microfracture of OLTs between 2009 and 2014 were monitored. CTA was performed post-operatively at 6 months and at 1 and 2 years after surgery. The post-operative thickness of the repaired tissue associated with OLT (grade) and the volume of the subchondral cystic lesions were evaluated using CTA. Clinical outcomes, including the pain visual analog scale (VAS) and American Orthopaedic Foot and Ankle Society (AOFAS) ankle functional scores, were evaluated and correlated with CTA.

RESULTS

The proportion of fully grown tissue (grade 3) increased over time; specifically, the rates were 12/40 (33.3%) at 6 months, 11/18 (61.1%) at 1 year, and 8/10 (80%) at 2 years after surgery (p = 0.005). The VAS pain (p < 0.001) and AOFAS scores (p < 0.001) were also improved at the final follow-up; however, they were not associated with repaired tissue thickness as shown by CTA (n.s.).

CONCLUSIONS

After microfracture of OLTs, tissue growth in the osteochondral defects was well visualized using CT arthrography and was observed in most cases. However, the CTA findings were not related to the clinical outcomes.

LEVEL OF EVIDENCE

IV.

SPECT/CT arthrography

Single photon emission CT (SPECT)/CT arthrography, the combination of CT arthrography and late phase bone SPECT/CT, has been developed in 2011 and so far used in knee, ankle and wrist joints. SPECT/CT offers functional information about increased bone turnover in combination with morphological details. Compared with SPECT/CT alone, additional intra-articular contrast enables the assessment of cartilage, menisci, ligaments and loose bodies. SPECT/CT arthrography is a promising alternative technique for the evaluation of internal derangement of joints in patients with MR contraindications and/or metallic implants. In this article, we review and report our 5-year experience with this technique illustrated with patient examples and give a perspective for future applications.

[Chondral and osteochondral defects : Representation by imaging methods]

Morphological imaging of cartilage at high resolution allows the differentiation of chondral and osteochondral lesions. Nowadays, magnetic resonance imaging is the principal diagnostic tool in the assessment of cartilage structure and composition. Conventional radiography, computed tomography, ultrasound or optical coherence tomography are adjunct diagnostic modalities in the assessment of cartilage pathologies. The present article discusses the up-to-date diagnostic practice of cartilage imaging in terms of its scientific basis and current clinical status, requirements, techniques and image interpretation. Innovations in the field such as functional MRI are discussed as well due to their mid- to long-term clinical perspective.

MRI of Native Knee Cartilage Delamination Injuries

OBJECTIVE

The purpose of this article is to describe the normal imaging appearance of cartilage and the pathophysiologic findings, imaging appearance, and surgical management of cartilage delamination.

CONCLUSION

Delamination injuries of knee cartilage signify surgical lesions that can lead to significant morbidity without treatment. These injuries may present with clinical symptoms identical to those associated with meniscal injury, and arthroscopic identification can be difficult, thereby creating a role for imaging diagnosis. A low sensitivity of imaging identification of delamination injury of the knee is reported in the available literature, although vast improvements in MRI of cartilage have since been introduced.

Accuracy of computed tomographic arthrography for assessment of articular cartilage defects in the ovine stifle

Articular cartilage defects are one of the features of osteoarthritis in animals and humans. Early detection of cartilage defects is a challenge in clinical veterinary practice and also in translational research studies. An accurate, diagnostic imaging method would be desirable for detecting and following up lesions in specific anatomical regions of the articular surface. The current prospective experimental study aimed to describe the accuracy of computed tomographic arthrography (CTA) for detecting cartilage defects in a common animal model used for osteoarthritis research, the ovine stifle (knee, femoropatellar/femorotibial) joint. Joints in cadaver limbs (n = 42) and in living animals under anesthesia (n = 13) were injected with a contrast medium and imaged using a standardized CT protocol. Gross anatomy and histological assessment of specific anatomic regions were used as a gold standard for the evaluation of sensitivity, specificity, negative predictive value, and positive predictive value for CTA identification of articular cartilage defects in those regions. Pooled estimated sensitivity and specificity were 90.32% and 97.30%, respectively, in cadaver limbs, and 81.82% and 95.24%, respectively, in living animals. Pooled estimated positive predictive value and negative predictive values were 98.25% and 85.71%, respectively, in cadaver limbs, and 81.82% and 95.24%, respectively, in living animals. The delineation of cartilage surface was good for anatomical regions most frequently affected by cartilage defects in the ovine stifle: medial femoral condyle, medial tibial condyle, and patella. This study supported the use of CTA as an imaging technique for detecting and monitoring articular cartilage defects in the ovine stifle joint.

New approach for predictive measurement of knee cartilage defects with three-dimensional printing based on CT-arthrography: A feasibility study

PURPOSE

The aim was to prove the possibility of creating an exact module of knee cartilage defects using 3D printing.

METHODS

Defects were created in cadaver knees. CT-arthrography and 3-Tesla MRI were performed. Based on CTA images a model of the cartilage was created using 3D printing. Defect-sizes in the imaging modalities were compared.

RESULTS

Estimated lesion area in 3D model differed approximately 5% comparing to the defect sizes in knees. MRI underestimated the defect on average of 12%, whereas the CTA overestimated the defect about 3%.

CONCLUSIONS

We proved the feasibility of creating an accurate module of knee cartilage.

MRI EVALUATION OF KNEE CARTILAGE

Through the ability of magnetic resonance imaging (MRI) to characterize soft tissue noninvasively, it has become an excellent method for evaluating cartilage. The development of new and faster methods allowed increased resolution and contrast in evaluating chondral structure, with greater diagnostic accuracy. In addition, physiological techniques for cartilage assessment that can detect early changes before the appearance of cracks and erosion have been developed. In this updating article, the various techniques for chondral assessment using knee MRI will be discussed and demonstrated.

OARSI Clinical Trials Recommendations: Knee imaging in clinical trials in osteoarthritis

Significant advances have occurred in our understanding of the pathogenesis of knee osteoarthritis (OA) and some recent trials have demonstrated the potential for modification of the disease course. The purpose of this expert opinion, consensus driven exercise is to provide detail on how one might use and apply knee imaging in knee OA trials. It includes information on acquisition methods/techniques (including guidance on positioning for radiography, sequence/protocol recommendations/hardware for magnetic resonance imaging (MRI)); commonly encountered problems (including positioning, hardware and coil failures, sequences artifacts); quality assurance (QA)/control procedures; measurement methods; measurement performance (reliability, responsiveness, validity); recommendations for trials; and research recommendations.

Anatomical distribution of areas of preserved cartilage in advanced femorotibial osteoarthritis using CT arthrography (Part 1)

OBJECTIVE

To determine subregions of normal and abnormal cartilage in advanced stages of femorotibial osteoarthritis (OA) by mapping the entire femorotibial joint in a cohort of pre-total knee replacement (TKR) OA knees.

DESIGN

We defined an areal subdivision of the femorotibial articular cartilage surface on CT arthrography (CTA), allowing the division of the femorotibial articular surface into multiple (up to n = 204 per knee) subregions and the comparison of the same areas between different knees. Two readers independently classified each cartilage area as normal, abnormal or non-assessable in 41 consecutive pre-TKR OA knees.

RESULTS

A total of 6447 cartilage areas (from 41 knees) were considered assessable by both readers. The average proportion of preserved cartilage was lower in the medial femorotibial joint than in the lateral femorotibial joint for both readers (32.0/69.8% and 33.9/68.5% (medial/lateral) for reader 1 and 2 respectively, all P < 0.001). High frequencies of normal cartilage were observed at the posterior aspect of the medial condyle (up to 89%), and the anterior aspect of the lateral femorotibial compartment (up to 100%). The posterior aspect of the medial condyle was the area that most frequently exhibited preserved cartilage in the medial femorotibial joint, contrasting with the high frequency of cartilage lesions in the rest of that compartment.

CONCLUSIONS

Cartilage at the posterior aspect of the medial condyle, and at the anterior aspect of the lateral femorotibial compartment, may be frequently preserved in advanced grades of OA.

Imaging following acute knee trauma

Joint injury has been recognized as a potent risk factor for the onset of osteoarthritis. The vast majority of studies using imaging technology for longitudinal assessment of patients following joint injury have focused on the injured knee joint, specifically in patients with anterior cruciate ligament injury and meniscus tears where a high risk for rapid onset of post-traumatic osteoarthritis is well known. Although there are many imaging modalities under constant development, magnetic resonance (MR) imaging is the most important instrument for longitudinal monitoring after joint injury. MR imaging is sensitive for detecting early cartilage degeneration and can evaluate other joint structures including the menisci, bone marrow, tendons, and ligaments which can be sources of pain following acute injury. In this review, focusing on imaging following acute knee trauma, several studies were identified with promising short-term results of osseous and soft tissue changes after joint injury. However, studies connecting these promising short-term results to the development of osteoarthritis were limited which is likely due to the long follow-up periods needed to document the radiographic and clinical onset of the disease. Thus, it is recommended that additional high quality longitudinal studies with extended follow-up periods be performed to further investigate the long-term consequences of the early osseous and soft tissue changes identified on MR imaging after acute knee trauma.

Visualization of joint and bone using dual-energy CT arthrography with contrast subtraction: in vitro feasibility study using porcine joints

OBJECTIVE

To assess the feasibility of subtracting various concentrations of iodinated contrast material on dual-energy computed tomographic (DECT) arthrography to provide both CT arthrography and virtual unenhanced CT (VUCT) in a single CT acquisition.

MATERIALS AND METHODS

This was an in vitro study for which institutional review board approval was not required. CT arthrographies of 12 joints of pig cadavers were obtained using dual-energy CT. Various concentrations of iodinated contrast material, 25% (75 mg/ml), 50% (150 mg/ml), 75% (225 mg/ml), and 100% (300 mg/ml) were used for the DECT arthrography. The paired regions of interest (ROI) were drawn over the same location on two paired CT scans at different tube voltages (80 kVp and 140 kVp). The average Hounsfield units (HU) ratio of the contrast media(HU on CT at 80 kVp/HU on CT at 140 kVp) was calculated for each joint. Subtraction of contrast material was carried out using VUCT application

RESULTS

The 25% iodinated contrast mixture was successfully subtracted from DECT arthrography of four joints, in which the average HU ratio ranged from 1.95 to 2.0. The subtraction of the 50%,75%, and 100% iodine contrast mixtures was not successful, because of the upper demonstrable HU limit in dual-energy CT.

CONCLUSIONS

DECT arthrography with 25% iodinated contrast medium injection can provide both CT arthrography and virtual unenhanced images in a single CT acquisition.

A comparison of 3-T magnetic resonance imaging and computed tomography arthrography to identify structural cartilage defects of the fetlock joint in the horse

Articular cartilage defects are prevalent in metacarpo/metatarsophalangeal (MCP/MTP) joints of horses. The aim of this study was to determine and compare the sensitivity and specificity of 3-Tesla magnetic resonance imaging (3-T MRI) and computed tomography arthrography (CTA) to identify structural cartilage defects in the equine MCP/MTP joint. Forty distal cadaver limbs were imaged by CTA (after injection of contrast medium) and by 3-T MRI using specific sequences, namely, dual-echo in the steady-state (DESS), and sampling perfection with application-optimised contrast using different flip-angle evolutions (SPACE). Gross anatomy was used as the gold standard to evaluate sensitivity and specificity of both imaging techniques. CTA sensitivity and specificity were 0.82 and 0.96, respectively, and were significantly higher than those of MRI (0.41 and 0.93, respectively) in detecting overall cartilage defects (no defect vs. defect). The intra and inter-rater agreements were 0.96 and 0.92, respectively, and 0.82 and 0.88, respectively, for CT and MRI. The positive predictive value for MRI was low (0.57). CTA was considered a valuable tool for assessing cartilage defects in the MCP/MTP joint due to its short acquisition time, its specificity and sensitivity, and it was also more accurate than MRI. However, MRI permits assessment of soft tissues and subchondral bone and is a useful technique for joint evaluation, although clinicians should be aware of the limitations of this diagnostic technique, including reduced accuracy.

The diagnostic value of direct CT arthrography using MDCT in the evaluation of acetabular labral tear: with arthroscopic correlation

OBJECTIVE

The purpose of this study was first, to determine the sensitivity, specificity, and accuracy of MDCT arthrography (CTA) for the diagnosis of acetabular labral tear and sulcus; second, to correlate tear types using the Lage classification system on CTA compared with the arthroscopic classification; and third, to correlate CTA localization with arthroscopic localization.

MATERIALS AND METHODS

Direct CTA was performed using 16- or 64-slice MDCT in 126 hips (124 patients) who had chronic groin pain and positive impingement test. Images were reviewed and evaluated by two experienced musculoskeletal radiologists preoperatively. CTA findings were compared with arthroscopic findings in 58 hips (56 patients) under consensus by two orthopedic surgeons.

RESULTS

Forty-one of the 58 hips were diagnosed as labral tears on CT arthrography. Forty-three of the 58 hips were shown to have a labral tear on arthroscopy. Sensitivity, specificity, and accuracy for detecting labral tear and sulcus by CTA were 90.7%, 86.7%, and 89.7%, and 93.8%, 97.6% and 96.6% respectively for observer 1, and 90.7% and 80.0%, 87.9% and 87.5%, 95.2%, and 93.1 % respectively for observer 2. Thirty-five out of 41 hips (85%) that were diagnosed with labral tear on CTA correlated substantially with arthroscopic Lage classification (kappa coefficient = 0.65). CTA and arthroscopic findings showed similar distribution patterns of the tears with most lesions located in antero- and postero-superior areas (p = 0.013).

CONCLUSION

Direct CT arthrography using MDCT may be a useful diagnostic technique in the detection of acetabular labral tear.

Bath Concentration of Anionic Contrast Agents Does Not Affect Their Diffusion and Distribution in Articular Cartilage In Vitro

OBJECTIVE

Differences in contrast agent diffusion reflect changes in composition and structure of articular cartilage. However, in clinical application the contrast agent concentration in the joint capsule varies, which may affect the reliability of contrast enhanced cartilage tomography (CECT). In the present study, effects of concentration of x-ray contrast agents on their diffusion and equilibrium distribution in cartilage were investigated.

DESIGN

Full-thickness cartilage discs (d = 4.0 mm, n = 120) were detached from bovine patellae (n = 24). The diffusion of various concentrations of ioxaglate (5, 10, 21, 50 mM) and iodide (30, 60, 126, 300 mM) was allowed only through the articular surface. Samples were imaged with a clinical peripheral quantitative computed tomography scanner before immersion in contrast agent, and after 1, 5, 9, 16, 25, and 29 hours in the bath.

RESULTS

Diffusion and partition coefficients were similar between different contrast agent concentrations. The diffusion coefficient of iodide (473 ± 133 µm(2)/s) was greater (P ≤ 0.001) than that of ioxaglate (92 ± 46 µm(2)/s). In full-thickness cartilage, the partition coefficient (at 29 h) of iodide (71 ± 5%) was greater (P ≤ 0.02 with most concentrations) than that of ioxaglate (62 ± 6%).

CONCLUSIONS

Significant differences in partition and diffusion coefficient of two similarly charged (-1) contrast agents were detected, which shows the effect of steric interactions. However, the increase in solute concentration did not increase its partition coefficient. In clinical application, it is important that contrast agent concentration does not affect the interpretation of CECT imaging.

The effect of meniscal tears on cartilage loss of the knee: findings on serial MRIs

BACKGROUND

The relationship between meniscal tears and progressive loss of hyaline cartilage and osteoarthritis of the knee has been reported in the literature. The current treatment protocols for meniscal tears include conservative treatment, meniscal repair, and meniscectomy. Treatment plans are based on factors such as tear pattern, patient age, and associated pathology. The mechanism, pattern, and treatment of meniscal tears vary with age and activity level. Younger, more active patients often sustain more acute tears, which are more amenable to repair due to increased propensity for healing compared with older patients. It is unclear which patients or types of meniscal tears will go on to sustain cartilage loss or osteoarthritis.

OBJECTIVE

In our study, we aimed to determine magnetic resonance imaging (MRI) findings in patients with meniscal tears that may be predictive as a risk factor for future cartilage loss.

METHODS

A database was retrospectively searched for patients with ≥ 2 MRIs of the same knee over a 7-year period, with the initial report containing the keyword "meniscal tear." Follow-up examinations were then evaluated for cartilage loss.

RESULTS

Seventy-six meniscal tears were evaluated. Initial MRI findings associated with cartilage loss included subchondral bone marrow edema (P < 0.0001), meniscal extrusion (P < 0.001), radial meniscal tear (P = 0.017), and posterior horn meniscal tear (P = 0.031). In patients without meniscectomy, cartilage loss was observed in 38% (15/39) compared with 76% (28/37) in patients with meniscectomy, (P = 0.0001).

CONCLUSION

Subchondral bone marrow edema and meniscal extrusion were the strongest MRI predictors for cartilage loss in an untreated knee with a meniscal tear. There was significantly greater cartilage loss in patients post-meniscectomy at follow-up than in those who did not undergo meniscectomy.

Ankle post-traumatic osteoarthritis: a CT arthrography study in patients with bi- and trimalleolar fractures

PURPOSE

To detect radiographically occult cartilage lesions using CT arthrography (CTa) in patients with malleolar fractures treated with open reduction internal fixation and to correlate the lesions with the functional outcome score.

MATERIALS AND METHODS

Twenty-one patients (13 men and 8 women, mean age 35 years, range 16-55) underwent ankle CTa after a mean postoperative period of 565 days (range 271-756). CTa images were analyzed by two radiologists. Articular surface post-traumatic collapse and subsequent cartilage defects or erosions were recorded in millimeters and in a binary mode (i.e., present if >50% of cartilage thickness) respectively. The functional outcome was assessed using the American Orthopedic Foot and Ankle Society (AOFAS) score by two orthopaedic surgeons. The statistical analysis correlated the AOFAS score with both imaging parameters and was performed with ANOVA using the MedCalc statistical package, version 11.3.

RESULTS

Of the total of 12 articular surface steps recorded, 2/12 (16.67%) were anterolateral, 4/12 (33.33%) posterolateral, 5/12 (41.67%) anteromedial, and 1/12(8.33%) posteromedial. Of the total of 42 cartilage lesions, 7/42 (16.67%) were anterolateral, 14/42 (33.33%) posterolateral, 12/42 (28.57%) anteromedial, and 9/42 (21.43%) posteromedial. The mean AOFAS score was 8.67 (range 5.95-9.70). There was no statistically significant correlation between the AOFAS score and the post-traumatic internal derangement of the ankle joint (p = 0.524).

CONCLUSION

CTa detects radiographically silent cartilage lesions in patients with fractures of the ankle joint. There is no correlation of the extent of lesions and the patient's AOFAS score.

Effects of cartilage remnants of the posterior femoral condyles on femoral component rotation in varus knee osteoarthritis

Preoperative planning of total knee arthroplasty (TKA) based on computerized tomography (CT) data can produce a femoral rotational error due to lack of information on the femoral cartilage thickness. The research question of this study is how much femoral rotational error is expected due to the cartilage remnants when using the posterior condylar angles (PCA, angle between the posterior condylar line and the surgical epicondylar axis (SEA)) on CT data. CT arthrography was performed for 35 consecutive varus osteoarthritic knees in 31 patients who underwent TKA, on which the cartilage thicknesses of the posterior femoral condyles were measured. The PCAs when including or excluding the cartilage remnants were also measured. The cartilage thicknesses of the medial and lateral posterior condyles averaged 0.39mm (SD=0.53) and 1.55mm (SD=0.26), respectively (p<0.0001). When the cartilage was included or excluded, the PCA averaged 2.2° (SD=1.5) and 3.3° (SD=1.5), respectively (p=0.002). The cartilage remnants in the posterior femoral condyles produced an average of 1.1° and a maximum of 2.1° of additional femoral external rotation when using CT data for the preoperative planning. CT scan measurements of femoral rotation are subject to error. Although this is said to be small and within the safety margin for setting the femoral component parallel to the trans-epicondylar axis, this difference should be considered by surgeons who use the posterior condylar axis, in order to avoid excessive external rotation of the femoral component.

Imaging of osteochondritis dissecans

Osteochondritis dissecans (OCD) is a localized process that affects the subchondral bone and can progress to the overlying articular cartilage. The cause of this lesion remains elusive. With the vague clinical symptoms and signs of OCD, imaging plays a vital role in making the diagnosis and helping with the prognosis of OCD lesions. This article reviews current imaging modalities for the assessment of OCD including conventional radiography, nuclear medicine, computed tomography (CT), CT arthrography, magnetic resonance (MR) and MR arthrography. The role of imaging in evaluating healing of the OCD and articular congruity after surgical and nonsurgical management is discussed.

Comparison of MR-arthrography and MDCT-arthrography for detection of labral and articular cartilage hip pathology

OBJECTIVE

To compare the diagnostic ability of MR arthrography (MRa) and MDCT arthrography (CTa) in depicting surgically proven hip labral tears and articular cartilage degradation.

MATERIALS AND METHODS

Labral pathology and articular cartilage were prospectively evaluated with MRa and CTa in 14 hips of 10 patients. The findings were evaluated by two independent observers (a musculoskeletal fellow and one senior musculoskeletal radiologist). Sensitivity, specificity, accuracy, and positive predictive value were determined using arthroscopic and open surgery findings as the standard of reference. Interobserver agreement was recorded. All images were assessed for the presence of a labral tear (according to Czerny classification) and for cartilage erosion using a 3 point scale for both methods: 1 = complete visualization-sharp edges, 2 = blurred edges fissuring-partial defects, 3 = exposed bone. The same classification was applied surgically.

RESULTS

Disagreement between the senior observer and the fellow observer was recorded in three cases of labral tearing with MRa and six with CTa. Disagreement was also found in four cases of cartilage erosion with both MRa and CTa. The percent sensitivity, specificity, accuracy, and positive predictive value for correctly assessing the labral tear were as follows for MRa/CTa, respectively: 100/15, 50/13, 90/14, and 90/13 (P < 0.05). The same values for cartilage assessment were 63/66, 33/40, 50/57 and 55/66 (P > 0.05).

CONCLUSION

Interobserver reproducibility with MRa is very good for labral tearing assessment. MRa is better for assessing labral tears. CTa shows better, but not statistically significant, demonstration of the articular cartilage.

The role of multidetector CT arthrography in the investigation of suspected intra-articular hip pathology

The aim of this study was to evaluate the role of multidetector CT (MDCT) arthrography in the diagnosis of intra-articular hip pathology. A retrospective review of 96 patients who had undergone CT hip arthrography was performed. Data regarding the presence of a labral tear, paralabral cyst, chondral loss, acetabular version, femoral morphology and fibrocystic change were collected. We detected 28 labral tears (24 anterior, 2 anterolateral, 1 lateral and 1 posterolateral). An abnormal labral-chondral transitional zone was seen in 9 patients and 4 patients had surface labral fraying. We identified three paralabral cysts. Acetabular cartilage loss was detected in 45 and femoral cartilage loss in 9 patients. An abnormal anterior femoral head and neck junction was present in 18 hips and fibrocystic change in 8. Acetabular retroversion was present in 11 hips. 63 sets of patient notes were reviewed, of which 49 were in-patients with abnormal MDCT arthrogram findings. Surgical correlation was available in 27 patients. There was a discrepancy between the findings of a labral tear in one patient (false negative, 90% sensitivity and 100% specificity) and the presence of acetabular cartilage loss (88% sensitivity and 100% specificity) and femoral cartilage loss (94% sensitivity and 100% specificity) in three patients. MDCT arthrography affords accurate detection of intra-articular hip pathology.

Imaging of lower limb cartilage

The cartilage of the lower limb joints is exposed to high levels of mechanical stress and therefore is a frequent site of degenerative and traumatic lesions. Magnetic resonance imaging (MRI) is the modality of choice for the assessment of these cartilage lesions. To date, clinically available sequences have focused on morphological defects and cartilage loss. Efforts have been made in recent years to depict cartilage lesions at an earlier stage, with new quantitative sequences focusing on the biochemical assessment of tissue.After a brief review of the hyaline cartilage structure, we review the current morphological imaging methods and the biochemical MRI techniques to assess the cartilage. We then illustrate the application of these MRI sequences for the most common degenerative and traumatic disorders affecting lower limb cartilage.

Three dimensional assessment of knee cartilage in cadavers with high resolution MR-arthrography and MSCT-arthrography

RATIONALE AND OBJECTIVES

The aim of this study was to compare high-resolution magnetic resonance (MR) arthrography and multislice computed tomographic (MSCT) arthrography in the evaluation of the entire knee cartilage obtained from cadavers.

MATERIALS AND METHODS

MR arthrography and MSCT arthrography were performed on 16 cadaver knees, and their findings were compared to those found during macroscopic assessment. The sensitivity and specificity of MR arthrography and MSCT arthrography for detecting cartilage lesions of grade > or = 2 and Spearman's correlation coefficients between arthrographic and macroscopic grades were determined. In addition, cartilage surface conspicuity of the two techniques was measured using a subjective ranking system.

RESULTS

The sensitivity and specificity, respectively, for the detection of cartilage disorder (grade > or = 2) were 87% and 97% on MR arthrography and 84% and 99% on MSCT arthrography. There was no statistically significant difference between the two techniques in sensitivity (P = 1.000) or specificity (P = .625). Spearman's correlation coefficients between MR arthrography or MSCT arthrography and macroscopic grading were 0.783 and 0.800, respectively, with no statistically difference (P = .492). Both MR arthrography and MSCT arthrography enabled the accurate depiction of cartilage surface.

CONCLUSIONS

High-resolution MR arthrography and MSCT arthrography were comparably accurate for the assessment of cartilage lesions of the entire knee.

CT arthrography, MR arthrography, PET, and scintigraphy in osteoarthritis

CT arthrography and MR arthrography are accurate methods for the study of surface cartilage lesions and cartilage loss. They also provide information on subchondral bone and marrow changes, and ligaments and meniscal lesions that can be associated with osteoarthritis. Nuclear medicine also offers new insights in the assessment of the disease. This article discusses the strengths and limitations of CT arthrography and MR arthrography. It also highlights nuclear medicine methods that may be relevant to the study of osteoarthritis in research and clinical practice.

Optimization of the contrast mixture ratio for simultaneous direct MR and CT arthrography: an in vitro study

Objective

This study was designed to determine the optimal mixture ratio of gadolinium and iodinated contrast agent for simultaneous direct MR arthrography and CT arthrography.

Materials and Methods

An in vitro study was performed utilizing mixtures of gadolinium at six different concentrations (0.625, 1.25, 2.5, 5.0, 10 and 20 mmol/L) and iodinated contrast agent at seven different concentrations (0, 12.5, 25, 37.5, 50, 75 and 92-99.9%). These mixtures were placed in tissue culture plates, and were then imaged with CT and MR (with T1-weighted sequences, proton-density sequences and T2-weighted sequences). CT numbers and signal intensities were measured. Pearson's correlation coefficients were used to assess the correlations between the gadolinium/iodinated contrast agent mixtures and the CT numbers/MR signal intensities. Scatter diagrams were plotted for all gadolinium/iodinated contrast agent combinations and two radiologists in consensus identified the mixtures that yielded the optimal CT numbers and MR signal intensities.

Results

The CT numbers showed significant correlation with iodinated contrast concentrations (r = 0.976, p < 0.001), whereas the signal intensities as measured on MR images showed a significant correlation with both gadolinium and iodinated contrast agent concentrations (r = -484 to -0.719, p < 0.001). A review of the CT and MR images, graphs, and scatter diagram of 42 combinations of the contrast agent showed that a concentration of 1.25 mmol/L gadolinium and 25% iodinated contrast agent was the best combination for simultaneous CT and MR imaging.

Conclusion

A mixture of 1.25 mmol/L gadolinium and 25% iodinated contrast agent was found to be optimal for simultaneous direct MR arthrography and CT arthrography.

Chronic medial knee pain without history of prior trauma: correlation of pain at rest and during exercise using bone scintigraphy and MR imaging

OBJECTIVE

The objective of this study was to correlate chronic medial knee pain at rest and during exercise with bone scintigraphic uptake, bone marrow edema pattern (BMEP), cartilage lesions, meniscal tears, and collateral ligament pathologies on magnetic resonance MR imaging (MRI).

MATERIALS AND METHODS

Fifty consecutive patients with chronic medial knee pain seen at our institute were included in our study. Pain level at rest and during exercise was assessed using a visual analog scale (VAS). On MR images, BMEP volume was measured, and the integrity of femoro-tibial cartilage, medial meniscus, and medial collateral ligament (MCL) were assessed. Semiquantitative scintigraphic tracer uptake was measured. Multivariate linear regression analysis was performed.

RESULTS

At the day of examination, 40 patients reported medial knee pain at rest, 49 when climbing stairs (at rest mean VAS 33 mm, range 0-80 mm; climbing stairs mean VAS, 60 mm, range 20-100 mm). Bone scintigraphy showed increased tracer uptake in 36 patients (uptake factor, average 3.7, range 2.4-18.0). MRI showed BMEP in 31 studies (mean volume, 4,070 mm(3); range, 1,200-39,200 mm(3)). All patients with BMEP had abnormal bone scintigraphy. Ten percent of patients with pain at rest and 8% of patients with pain during exercise showed no BMEP but tracer uptake in scintigraphy. Tracer uptake and signal change around MCL predicted pain at rest significantly (tracer uptake p = 0.004; MCL signal changes p = 0.002). Only MCL signal changes predicted pain during exercise significantly (p = 0.001).

CONCLUSION

In chronic medial knee pain, increased tracer uptake in bone scintigraphy is more sensitive for medial knee pain than BMEP on MRI. Pain levels at rest and during exercise correlate with signal changes in and around the MCL.

Current concepts and advances: computerized tomography in sports medicine

Computed tomography (CT) is a widely used imaging technique. With the introduction of multidetector row technology, CT has been further refined. Although the focus of this transformation has been body and cardiac imaging, orthopedic imaging has benefited greatly. Specifically, the improvements in CT have made it possible to obtain submillimeter-thick slices that enable the creation of high-resolution multiplanar reformations from a single scan. These images usually are indistinguishable from direct plane acquisitions and provide unparalleled detail. Additionally, the factors responsible for causing CT image artifacts when hardware is present are much better understood and the improvements in CT technique and technology can be exploited to provide better images of patients with orthopedic hardware. The detailed multiplanar visualization of joints facilitates CT arthrography that has undergone a renaissance. CT arthrography is useful in the very large athlete or patient, the claustrophobic, and for those patients who fail a conventional magnetic resonance examination or magnetic resonance arthrogram.

Osteoarthritis: current role of imaging

Osteoarthritis (OA) is the most prevalent joint disease; it is increasingly common in the aging population of Western society and has a major health economic impact. Despite surgery and symptom-oriented approaches there is no efficient treatment. Conventional radiography has played a role in the past in confirming diagnosis and demonstrating late bony changes and joint space narrowing. MRI has become the method of choice in large research endeavors and may become important for individualized treatment planning. This article focuses on radiography and MRI, with insight into other modalities, such as ultrasound, scintigraphy, and CT. Their role in OA diagnosis, follow-up, and research is discussed.

Comparison of MR-arthrography and CT-arthrography in hyaline cartilage-thickness measurement in radiographically normal cadaver hips with anatomy as gold standard

OBJECTIVE

To compare magnetic resonance (MR)-arthrography and multidetector-spiral-computed-tomography (MDSCT)-arthrography in cartilage-thickness measurement, in hips without cartilage loss, with coronal anatomic slices as gold standard.

METHOD

Institutional review board permission to study cadavers of individuals who willed their bodies to science was obtained. Two independent observers measured femoral and acetabular cartilage thicknesses of 12 radiographically normal hips (six women, five men; age range, 52-98 years; mean age, 76.5 years), on MDSCT-arthrographic and MR-arthrographic reformations, and on coronal anatomic slices, excluding regions of cartilage loss. Inter- and intraobserver reproducibilities were determined. Analysis of variance (ANOVA) was used to test differences between MR-arthrographic and MDSCT-arthrographic measurement errors compared to anatomy.

RESULTS

By MR-arthrography, cartilage was not measurable at approximately 50% of points on sagittal and transverse sections, compared to 0-6% of the points by MDSCT-arthrography. In the coronal plane, the difference between MDSCT-arthrographic and MR-arthrographic measurement errors was not significant (P=0.93).

CONCLUSION

In the coronal plane, MR-arthrography and MDSCT-arthrography were similarly accurate for measuring hip cartilage thickness.