Cartilage Thickness in Cadaveric Ankles: Measurement with Double-Contrast Multi–Detector Row CT Arthrography versus MR Imaging

Low-Dose Computed Tomography Arthrography Using Tin-Filter Technology: Advancing High-Resolution Cartilage Evaluation in the Ankle Joint

RATIONALE AND OBJECTIVES

Arthrographic imaging is essential for diagnosing and managing joint pathologies. Computed tomography arthrography (CTA) offers high spatial resolution and can complement or replace magnetic resonance imaging (MRI) when needed. Dose-reduction methods are crucial due to the significant radiation exposure from radiological procedures. This study explores the use of tin-filter technology in musculoskeletal radiology to reduce radiation dose without compromising image quality.

MATERIALS AND METHODS

39 sonographically guided joint fillings were conducted with no reported complications. Tin-filter CTA with tube voltage of 100 kVp was conducted for all patients, with radiation exposure metrics (DLP, CTDIVol) recorded and imaging results compared to MRI and if available arthroscopy for diagnostic accuracy. Four independent readers rated the images subjective quality by a range of different items like diagnostic suitability for assessing cartilage damage. For the objective image assessment, the contrast-to-noise ratio (CNR) and Signal-to noise ratio (SNR) were used.

RESULTS

Tin-filter CTA achieved a mean DLP of 19.37 mGy-cm (± 4.3). High subjective image quality was maintained (diagnostic grade: 1.71; intraclass correlation coefficient: 0.966). The mean CNR was 97.92 (± 34.65) for bone and 135.24 (± 68.56) for the contrast agent. Similarly, the mean SNR was 91.85 (± 32.74) for bone and 129.18 (± 67.44). Cartilage damage was identified in 69.2% of cases, with 78.9% confirmation in arthroscopy. CTA aligned with MRI findings in 74.1% of cases.

CONCLUSION

Tin-filter CTA, combined with sonographically guided joint filling, is a low-radiation, high-resolution method for assessing ankle joint cartilage. Its ability to detect subtle damage makes it invaluable for surgical planning, especially for patients with metal implants or inconclusive MRI results.

Cartilage defect identification on computed tomography arthrography in equine fetlock: Ex-vivo study

CT arthrography (CTA) for evaluating cartilage defects would be beneficial in clinical practice. Since the contrast medium (CM) volume is often driven by operator experience, the aim was to evaluate the minimum volume of iodinated CM for CTA sufficient to identify iatrogenic cartilage defects in horse fetlock. The study was conducted on ex-vivo 32 distal limbs from adult horses collected at slaughter. Iatrogenic cartilage defects were arthroscopically made on fetlock, at 5 predetermined locations. Subsequently, CT scans were performed, according to the following protocol: precontrast scan, followed by subsequent scans with incremental volumes of CM, ranging from 2,5-40 ml (total of 10 scans per fetlock). Then, the cartilage defects were measured macroscopically using a calliper. CTA scans were evaluated by a single operator, and defects were assessed for presence/absence and volume measures. Data were expressed as median and interquartile values. The association between CT scan assessments and different CM volumes was examined with chi-square test. The correlation between CT scans and macroscopic assessments was evaluated using Spearman's coefficient. Significance was set at a p-value <0.05. Twenty millilitres of CM were required to visualize 100 % of the defects, regardless of the location. A weak correlation was found between the defects' volume on macroscopic and CT scan assessment. Twenty millilitres of CM was sufficient to identify cartilage defects on the fetlock articular surface, supporting the conscious use of CM adequate for specific diagnostic purposes.

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.

Foot and Ankle Bone Marrow Edema Assessment in Long Distance Runners

BACKGROUND

The clinical significance of foot and ankle bone marrow edema (BME) is poorly understood.

METHODS

Magnetic resonance imaging (MRI) and the visual analog scale (VAS) pain scores were collected for 17 runners who participated in the Twin Cities Marathon, immediately postmarathon and at a 6-week follow-up. Bone marrow edema lesions were classified using lesion frequency, anatomical location, and grading scale change to calculate a BME score for each affected bone. Spearman rank correlation coefficient test was used to identify a possible correlation between VAS and postmarathon BME. A paired Student t test was used to detect differences between total mileage ran 6 weeks postmarathon in participants with or without BME.

RESULTS

After completing the marathon, 8 BME lesions were identified in 5 participants (29.4%; 5/17), 3 were men, and 2 were women, with a mean age of 33.8 years (range: 24-52), and BMI of 22.9 ± 4. All lesions were resolved on 6-week follow-up imaging. VAS pain scores did not correlate with postmarathon BME. A significant difference in total miles logged over 6 weeks postmarathon could not be found among participants with and without BME.

CONCLUSION

Foot and ankle BME changes identified by MRI were not correlated to clinical symptoms and may resolve with self-directed activity in less time than other areas of the lower extremity.

LEVEL OF EVIDENCE

Level II, Prospective Cohort Study.

The role of anatomical context in soft-tissue multi-organ segmentation of cadaveric non-contrast-enhanced whole body CT

BACKGROUND

Cadaveric computed tomography (CT) image segmentation is a difficult task to solve, especially when applied to whole-body image volumes. Traditional algorithms require preprocessing using registration, or highly conserved organ morphologies. These requirements cannot be fulfilled by cadaveric specimens, so deep learning must be used to overcome this limitation. Further, the widespread use of 2D algorithms for volumetric data ignores the role of anatomical context. The use of 3D spatial context for volumetric segmentation of CT scans as well as the anatomical context required to optimize the segmentation has not been adequately explored.

PURPOSE

To determine whether 2D slice-by-slice UNet algorithms or 3D volumetric UNet (VNet) algorithms provide a more effective method for segmenting 3D volumes, and to what extent anatomical context plays in the segmentation of soft-tissue organs in cadaveric, noncontrast-enhanced (NCE) CT.

METHODS

We tested five CT segmentation algorithms: 2D UNets with and without 3D data augmentation (3D rotations) as well as VNets with three levels of anatomical context (implemented via image downsampling at 1X, 2X, and 3X) for their performance via 3D Dice coefficients, and Hausdorff distance calculations. The classifiers were trained to segment the kidneys and liver and the performance was evaluated using Dice coefficient and Hausdorff distance on the segmentation versus the ground truth annotation.

RESULTS

Our results demonstrate that VNet algorithms perform significantly better (p < 0.05 $p<0.05$ ) than 2D models. Among the VNet classifiers, those that use some level of image downsampling outperform (as calculated through Dice coefficients) the VNet without downsampling. Additionally, the optimal amount of downsampling depends on the target organ.

CONCLUSIONS

Anatomical context is an important component of soft-tissue, multi-organ segmentation in cadaveric, NCE CT imaging of the whole body. Different amounts of anatomical contexts are optimal depending on the size, position, and surrounding tissue of the organ.

Osteochondral Lesions of the Ankle and Foot

Osteochondral lesions (OCLs) in the ankle are more common than OCLs of the foot, but both share a similar imaging appearance. Knowledge of the various imaging modalities, as well as available surgical techniques, is important for radiologists. We discuss radiographs, ultrasonography, computed tomography, single-photon emission computed tomography/computed tomography, and magnetic resonance imaging to evaluate OCLs. In addition, various surgical techniques used to treat OCLs-debridement, retrograde drilling, microfracture, micronized cartilage-augmented microfracture, autografts, and allografts-are described with an emphasis on postoperative appearance following these techniques.

A threshold volume of 10 ml is suggested for detecting articular cartilage defects in equine carpal joints using CT arthrography: Ex vivo pilot study

Computed tomographic arthrography (CTA) has been described as a method for detecting articular cartilage defects in equine carpal joints; however, published studies on the effects of contrast volume for lesion detection are currently lacking. The purpose of this prospective, experimental, pilot study was to determine a threshold volume of iodinated contrast for CTA of the antebrachiocarpal (ABC) and middle carpal (MC) joints for detection of articular cartilage surface defects. Articular cartilage defects were iatrogenically created in the surfaces of the ABC and MC joints of 20 equine cadaver limbs using arthroscopy. Unaltered articular surfaces within some joints acted as controls. Joints were imaged precontrast using multidetector CT. The ABC and MC joints were injected with a 150 mg iodine/ml nonionic contrast medium, in 5 ml increments from 5 to 50 ml per joint with CT performed subsequent to each increment. Cartilage defects were measured grossly using a caliper. Detection (qualitative) and measurement (quantitative) of the defects were independently performed by two board-certified radiologists using medical imaging software. At each volume of contrast, the interrater reliability for gross examination and the two observers in the detection of a defect was calculated (Gwet's AC1). Logistic mixed-effects models of selected volumes, 0, 5, 10, 15, and 50 ml, demonstrated that at 10 ml contrast and above, no statistically significant difference between either observer and gross examination for defect detection was identified for either joint. Findings supported using a dose of 10 ml for 150 mg iodine/ml concentration contrast media when performing CTA of equine carpal joints.

High resolution flat-panel CT arthrography vs. MR arthrography of artificially created osteochondral defects in ex vivo upper ankle joints

PURPOSE

High resolution flat-panel computed tomography arthrography (FPCT-A) and magnetic resonance arthrography (MR-A) are well suited to evaluate osteochondral lesions. The current study compares the performance of FPCT-A versus MR-A in an experimental setting.

METHODS

Fourteen cadaveric ankles were prepared with artificial osteochondral defects of various sizes in four separate talar locations. After intra-articular contrast injection, FPCT-A and 3-T MR-A were acquired. Each defect was then filled with synthetic pallets. The resulting cast was used as reference. Two independent radiologists measured the dimensions of all defects with FPCT-A and MR-A. Intra-class correlation coefficients (ICC) were calculated. Data were compared using t-tests and Bland-Altman plots.

RESULTS

The correlation for FPCT-A and cast was higher compared to MR-A and cast (ICC 0.876 vs. 0.799 for surface [length x width]; ICC 0.887 vs. 0.866 for depth, p<0.001). Mean differences between FPCT-A and cast measurements were -1.1 mm for length (p<0.001), -0.7 mm for width (p<0.001) and -0.4 mm for depth (p = 0.023). By MR-A, there were no significant differences for length and width compared to cast (p>0.05). Depth measurements were significantly smaller by MR-A (mean difference -1.1 mm, p<0.001). There was no bias between the different modalities.

CONCLUSIONS

Ex vivo FPCT-A and MR-A both deliver high diagnostic accuracy for the evaluation of osteochondral defects. FPCT-A was slightly more accurate than MR-A, which was most significant when measuring lesion depth.

An Experimentally Validated Finite Element Model of the Lower Limb to Investigate the Efficacy of Blast Mitigation Systems

Improvised explosive devices (IEDs) used in the battlefield cause damage to vehicles and their occupants. The injury burden to the casualties is significant. The biofidelity and practicality of current methods for assessing current protection to reduce the injury severity is limited. In this study, a finite-element (FE) model of the leg was developed and validated in relevant blast-loading conditions, and then used to quantify the level of protection offered by a combat boot. An FE model of the leg of a 35 years old male cadaver was developed. The cadaveric leg was tested physically in a seated posture using a traumatic injury simulator and the results used to calibrate the FE model. The calibrated model predicted hindfoot forces that were in good correlation (using the CORrelation and Analysis or CORA tool) with data from force sensors; the average correlation and analysis rating (according to ISO18571) was 0.842. The boundary conditions of the FE model were then changed to replicate pendulum tests conducted in previous studies which impacted the leg at velocities between 4 and 6.7 m/s. The FE model results of foot compression and peak force at the proximal tibia were within the experimental corridors reported in the studies. A combat boot was then incorporated into the validated computational model. Simulations were run across a range of blast-related loading conditions. The predicted proximal tibia forces and associated risk of injury indicated that the combat boot reduced the injury severity for low severity loading cases with higher times to peak velocity. The reduction in injury risk varied between 6 and 37% for calcaneal minor injuries, and 1 and 54% for calcaneal major injuries. No injury-risk reduction was found for high severity loading cases. The validated FE model of the leg developed here was able to quantify the protection offered by a combat boot to vehicle occupants across a range of blast-related loading conditions. It can now be used as a design and as an assessment tool to quantify the level of blast protection offered by other mitigation technologies.

Osteochondral defects of the talus: radiological appearance and surgical candidate profiling - A retrospective analysis

BACKGROUND

Osteochondral defects of the talus (OCD) are a well-established pathology within the ankle. They are most commonly associated with ankle trauma and whilst many are asymptomatic, they can have a significant negative impact on the patient, most notably with regards pain and mobility. Treatment of these lesions remains variable across the diverse cohort of these patients.

AIMS

Evaluating the incidence of talus OCDs. Evaluating anatomic and morphologic data of the lesions against previous studies. Establishing if there was there any associated ligamentous injury. Determining the cohort of patients who were considered/underwent surgical intervention.

METHODS

A retrospective review was performed on patients presenting to a single Scottish Hospital with Talar OCDs between 2012-2016. Data collected included radiological appearance of the lesions (location and size), clinical history, associated ligament injury, treatment given and subsequent outcome. Categorical variables were presented as count and percentage while non-parametric variables were presented as median and interquartile range.

RESULTS

90 new cases that matched our inclusion criteria were identified. Using the Raikin classification, the majority of injuries are in the posteromedial (26%), centrolateral (21%), and centromedial (18%) segments of the talus. Of note, no lesions were identified in the posterocentral segment. 46% of patients had an associated ligamentous injury, either in the form of a sprain or tear. Most commonly the injury involved both ATFL and CFL (82%). 70% of patients that underwent surgery had radiological evidence of ligamentous injury. No statistically significant difference was identified between the management option and the involved segment according to Orr/Raikin classifications.

CONCLUSION

Talus osteochondral defects are a pathology which is more common than originally thought and their treatment remain a controversial topic. Little is known about the physical history of the condition as most cases are asymptomatic, thus poorly documented by definition. There is a clear opportunity and need for further research into developing evidence-based guidelines for their management. This study tried to correlate the management of OCDs with epidemiological and radiological data.

Precision of computed tomography and cartilage-reproducing image reconstruction method in generating digital model for potential use in 3D printing of patient-specific radial head prosthesis: a human cadaver study

Background

A prosthetic replacement is a standard treatment for an irreparable radial head fracture; however, the surface mismatch of the commercially available designs is concerned for the long-term cartilage wear. The patient-specific implant created from 3D printing technology could be favorable in replicating the normal anatomy and possibly reduce such sequela. Our study aimed to assess the precision of the computed tomography (CT) and cartilage-reproducing image reconstruction method (CIRM) in generating digital models for potentially use in manufacturing the patient-specific prosthesis from 3D printing.

Methods

Eight intact  elbows (3 right and 5 left) from 7 formalin-embalmed cadavers (4 males and 3 females) with mean age of 83 years (range, 79–94 years) were used for this study. Computerized 3D models were generated from CT, and CIRM. The cartilage-reproducing image reconstruction method has compensated the cartilage profile based on the distance between the subchondral surfaces of the radial head and surrounding bones in CT images. The models of actual radial head geometry used as the gold standard was generated from CT arthrography (CTA). All models of each specimen were matched by registering the surface area of radial neck along with the tuberosity. The difference of head diameter, head thickness, and articular disc depth among three models was evaluated and analyzed by Friedman ANOVA and multiple comparison test using Bonferroni method for statistical correction. A p-value of less than 0.01 was considered statistically  significant. The difference of overall 3D geometry was measured with the root mean square of adjacent point pairs.

Results

The analysis displayed the difference of diameter, thickness, and disc depth across the models (p< 0.01). Pairwise comparisons revealed statistically significant difference of all parameters between CTA models and CT models (p< 0.01) whereas no difference was found between CTA models and CIRM models. The mean difference of overall 3D geometry between CTA models and CT models was 0.51±0.24 mm, and between CTA models and CIRM models was 0.24±0.10 mm.

Conclusions

CIRM demonstrated encouraging results in reestablish the normal anatomy and could be potentially used in production process of 3D printed patient-specific radial head prosthesis.

Flat-panel CT arthrography for cartilage defect detection in the ankle joint: first results in vivo

OBJECTIVES

The purpose of this study was to compare the diagnostic performance of flat-panel computed tomography (FPCT) arthrography for cartilage defect detection in the ankle joint to direct magnetic resonance (MR) arthrography using multidetector computed tomography (MDCT) arthrography as the reference standard.

METHODS

Twenty-seven patients with specific suspicion of articular cartilage lesion underwent ankle arthrography with injection of a mixture of diluted gadolinium and iobitridol and were examined consecutively with the use of FPCT, MDCT, and 1.5 T MR imaging. FPCT, MDCT, and MR arthrography examinations were blinded and randomly evaluated by two musculoskeletal radiologists in consensus. In each ankle, eight articular cartilage areas were assessed separately: medial talar surface, medial talar trochlea, lateral talar trochlea, lateral talar surface, tibial malleolus, medial tibial plafond, lateral tibial plafond, and fibular malleolus. Findings at FPCT and MR were compared with MDCT assessments in 216 cartilage areas.

RESULTS

For the detection of cartilage defects, FPCT demonstrated a sensitivity of 97%, specificity of 95%, and accuracy of 96%; and MR arthrography showed a sensitivity of 69%, specificity of 94%, and accuracy of 87%. FPCT and MR arthrography presented almost perfect agreement (κ = 0.87) and moderate agreement (κ = 0.60), respectively, with MDCT arthrography. Mean diagnostic confidence was higher for FPCT (2.9/3) than for MR (2.3/3) and MDCT (2.7/3) arthrography.

CONCLUSIONS

FPCT demonstrated better accuracy than did 1.5 T MR arthrography for cartilage defect detection in the ankle joint. Therefore, FPCT should be considered in patients scheduled for dedicated imaging of ankle articular cartilage.

Weight-Bearing CT Scan After Tibial Pilon Fracture Demonstrates Significant Early Joint-Space Narrowing

BACKGROUND

Posttraumatic osteoarthritis (PTOA) is a common and early sequela of tibial pilon fractures resulting in substantial long-term disability. New approaches are needed to objectively and reliably quantify early disease progression in order to critically assess the impact of interventions aimed at preventing or mitigating PTOA. Weight-bearing computed tomography (WBCT) scans provide a means for measuring joint space while the ankle is in a loaded, functional position. We assessed the interrater and intrarater reliability of a standardized, regional method to quantify joint-space loss following tibial pilon fracture compared with the uninjured contralateral ankle.

METHODS

We prospectively enrolled 20 patients with intra-articular tibial pilon fractures that were surgically treated at 1 of 2 level-I trauma centers. Six months after injury, bilateral ankle WBCT scans were obtained. Joint space was measured by 4 reviewers at 9 discrete regions of the tibiotalar articulation on sagittal images. Measurements were repeated by reviewers 2 weeks later. To characterize the measurement method, interrater correlation coefficient estimates and test-retest reproducibility were calculated.

RESULTS

The mean tibiotalar joint space was 21% less in the injured ankles compared with the contralateral uninjured ankles (p < 0.0001). The middle-lateral and middle-central regions of the joint demonstrated the greatest decrease in joint space between injured and uninured ankles. The interrater correlation coefficient of the measurement technique was 0.88, and the test-retest reproducibility was 0.80, indicating good reliability and reproducibility of the method.

CONCLUSIONS

We developed a simple, standardized, and reliable technique to quantify tibiotalar joint space following tibial pilon fracture on WBCT. Significant loss of joint space is seen 6 months after the injury. This tool can be used to longitudinally quantify loss of joint space following pilon fracture and assess the impact of interventions to reduce PTOA.

CT arthrography for demonstration of various articular injuries in post-sprained ankle pain

Background

Post-sprained ankles may sustain ligamentous tear, chondral defect, or osteochondral lesions (OCL). Being widely available and does not depend on high-end machine, the aim of this study was to assess the value of high resolution multi-detector CT arthrography (CTA) in detection of various ligamentous tears, chondral defects, and osteochondral lesions in case of sprain-related persistent ankle pain.

Results

There were 34 (68%) cases of ligamentous injury, most of which had single ligament affection whereas some cases demonstrated multi-ligamentous injury, and the total number of individual injured ligaments was 42 ligaments. There were 36 cases (72%) which had either chondral or osteochondral defects; the total number of OCL was 21 lesions and the total number of segmental cartilage defects was 20.

Conclusion

This study emphasized the diagnostic importance of multi-detector CTA in sprain-related ankle pain. In persistent post-sprained ankle pain, multi-detector CTA is a helpful imaging modality which could be utilized for detection of OCL, chondral defects, and various ligamentous tears.

High-resolution flat panel CT versus 3-T MR arthrography of the wrist: initial results in vivo

OBJECTIVES

The objective of this study was to compare the diagnostic performance of direct C-arm flat panel computed tomography arthrography (FPCT-A) with direct magnetic resonance arthrography (MR-A) of the wrist in patients with clinically suspected pathologies.

METHODS

Forty-nine patients underwent tri-compartmental wrist arthrography. FPCT-A was acquired using a high-resolution acquisition mode, followed by a 3-T MR exam using a dedicated wrist coil. Image quality and artifacts of FPCT-A and MR-A were evaluated with regard to the depictability of anatomical structures. The time stamps for the different image acquisitions were recorded for workflow assessment.

RESULTS

Image quality was rated significantly superior for all structures for FPCT-A (p < 0.001) as compared to MR-A including intrinsic ligaments, TFCC, cartilage, subchondral bone, and trabeculae. The differences in image quality were highest for cartilage (2.0) and lowest for TFCC (0.9). The artifacts were rated lower in MR-A than in FPCT-A (p < 0.001). The procedure was more time-efficient in FPCT-A than in MR-A.

CONCLUSIONS

FPCT-A of the wrist provides superior image quality and optimized workflow as compared to MR-A. Therefore, FPCT-A should be considered in patients scheduled for dedicated imaging of the intrinsic structures of the wrist.

KEY POINTS

• FPCT arthrography allows high-resolution imaging of the intrinsic wrist structures. • The image quality is superior as compared to MR arthrography. • The procedure is more time-efficient than MR arthrography.

Staging of Osteochondral Lesions of the Talus: MRI and Cone Beam CT

Osteochondral lesions (OCL) of the talus involve both articular cartilage and subchondral bone of the talar dome. This term refers to a wide spectrum of pathologies including mild bone marrow contusion as well as severe osteoarthritis resulting from long standing disease. Although Magnetic Resonance Imaging (MRI) at 1.5 Tesla is the leading cross-sectional modality for detection and staging of OCL, lack of spatial resolution hampers accurate assessment of thin articular cartilage. Cone Beam Computed Tomography (CBCT) arthrography is better suited for precise staging of cartilage lesions. The purpose of this pictorial review is to illustrate the strength of each imaging method.

[Pilon fractures : Review of diagnostics and classification]

Intraarticular fractures of the distal tibia (pilon fractures) are rare injuries and today they occur mostly in traffic accidents and falls from a great height. There are simple fractures in the context of low-energy traumas, as well as complex comminuted fractures in high-energy traumas. Besides the clinical examination, plain radiographs and computed tomographic scans are diagnostic prerequisites. The aim of the diagnostic process is to clearly identify and classify the fracture before appropriate treatment is initiated. The systems used to classify the displaced distal pilon fractures are supposed to ensure the three-dimensional assessment of the fracture and provide high inter- and intra-observer agreement. In addition to the classification of Rüedi and Allgöwer, the classification of pilon fractures has been carried out using the AO classification.

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.

Diagnostic Value of CT Arthrography for Evaluation of Osteochondral Lesions at the Ankle

Background. To retrospectively determine the diagnostic value of computed tomography arthrography (CTA) of the ankle in the evaluation of (osteo)chondral lesions in comparison to conventional magnetic resonance imaging (MRI) and intraoperative findings. Methods. A total of N = 79 patients had CTAs and MRI of the ankle; in 17/79 cases surgical reports with statements on cartilage integrity were available. Cartilage lesions and bony defects at talus and tibia were scored according to defect depth and size by two radiologists. Statistical analysis included sensitivity analyses and Cohen's kappa calculations. Results. On CTA, 41/79 and 31/79 patients had full thickness cartilage defects at the talus and at the tibia, respectively. MRI was able to detect 54% of these defects. For the detection of full thickness cartilage lesions, interobserver agreement was substantial (0.72 ± 0.05) for CTA and moderate (0.55 ± 0.07) for MRI. In surgical reports, 88–92% and 46–62% of full thickness defects detected by CTA and MRI were described. CTA findings changed the further clinical management in 15.4% of cases. Conclusions. As compared to conventional MRI, CTA improves detection and visualization of cartilage defects at the ankle and is a relevant tool for treatment decisions in unclear cases.

Human talar and femoral cartilage have distinct mechanical properties near the articular surface

Talar osteochondral lesions (OCL) frequently occur following injury. Surgical interventions such as femoral condyle allogeneic or autogenic osteochondral transplant (AOT) are often used to treat large talar OCL. Although AOT aims to achieve OCL repair by replacing damaged cartilage with mechanically matched cartilage, the spatially inhomogeneous material behavior of the talar dome and femoral donor sites have not been evaluated or compared. The objective of this study was to characterize the depth-dependent shear properties and friction behavior of human talar and donor-site femoral cartilage. To achieve this objective, depth-dependent shear modulus, depth-dependent energy dissipation and coefficient of friction were measured on osteochondral cores from the femur and talus. Differences between anatomical regions were pronounced near the articular surface, where the femur was softer, dissipated more energy and had a lower coefficient of friction than the talus. Conversely, shear modulus near the osteochondral interface was nearly indistinguishable between anatomical regions. Differences in energy dissipation, shear moduli and friction coefficients have implications for graft survival and host cartilage wear. When the biomechanical variation is combined with known biological variation, these data suggest the use of caution in transplanting cartilage from the femur to the talus. Where alternatives exist in the form of talar allograft, donor-recipient mechanical mismatch can be greatly reduced.

Acute Osteochondral Fractures in the Lower Extremities - Approach to Identification and Treatment

Chondral and osteochondral fractures of the lower extremities are important injuries because they can cause pain and dysfunction and often lead to osteoarthritis. These injuries can be misdiagnosed initially which may impact on the healing potential and result in poor long-term outcome. This comprehensive review focuses on current pitfalls in diagnosing acute osteochondral lesions, potential investigative techniques to minimize diagnostic errors as well as surgical treatment options. Acute osteochondral fractures are frequently missed and can be identified more accurately with specific imaging techniques. A number of different methods can be used to fix these fractures but attention to early diagnosis is required to limit progression to osteoarthritis. These fractures are common with joint injuries and early diagnosis and treatment should lead to improved long term outcomes.

Expedited patient-specific assessment of contact stress exposure in the ankle joint following definitive articular fracture reduction

Acute injury severity, altered joint kinematics, and joint incongruity are three important mechanical factors linked to post-traumatic osteoarthritis (PTOA). Finite element analysis (FEA) was previously used to assess the influence of increased contact stress due to joint incongruity on PTOA development. While promising agreement with PTOA development was seen, the inherent complexities of contact FEA limited the numbers of subjects that could be analyzed. Discrete element analysis (DEA) is a simplified methodology for contact stress computation, which idealizes contact surfaces as a bed of independent linear springs. In this study, DEA was explored as an expedited alternative to FEA contact stress exposure computation. DEA was compared to FEA using results from a previously completed validation study of two cadaveric human ankles, as well as a previous study of post-operative contact stress exposure in 11 patients with tibial plafond fracture. DEA-computed maximum contact stresses were within 19% of those experimentally measured, with 90% of the contact area having computed contact stress values within 1MPa of those measured. In the 11 fractured ankles, maximum contact stress and contact area differences between DEA and FEA were 0.85 ± 0.64 MPa and 22.5 ± 11.5mm(2). As a predictive measure for PTOA development, both DEA and FEA had 100% concordance with presence of OA (KL grade ≥ 2) and >95% concordance with KL grade at 2 years. These results support DEA as a reasonable alternative to FEA for computing contact stress exposures following surgical reduction of a tibial plafond fracture.

Accuracy assessment of 3D bone reconstructions using CT: an intro comparison

Computed tomography provides high contrast imaging of the joint anatomy and is used routinely to reconstruct 3D models of the osseous and cartilage geometry (CT arthrography) for use in the design of orthopedic implants, for computer assisted surgeries and computational dynamic and structural analysis. The objective of this study was to assess the accuracy of bone and cartilage surface model reconstructions by comparing reconstructed geometries with bone digitizations obtained using an optical tracking system. Bone surface digitizations obtained in this study determined the ground truth measure for the underlying geometry. We evaluated the use of a commercially available reconstruction technique using clinical CT scanning protocols using the elbow joint as an example of a surface with complex geometry. To assess the accuracies of the reconstructed models (8 fresh frozen cadaveric specimens) against the ground truth bony digitization-as defined by this study-proximity mapping was used to calculate residual error. The overall mean error was less than 0.4 mm in the cortical region and 0.3 mm in the subchondral region of the bone. Similarly creating 3D cartilage surface models from CT scans using air contrast had a mean error of less than 0.3 mm. Results from this study indicate that clinical CT scanning protocols and commonly used and commercially available reconstruction algorithms can create models which accurately represent the true geometry.

3.0T MR imaging of the ankle: Axial traction for morphological cartilage evaluation, quantitative T2 mapping and cartilage diffusion imaging-A preliminary study

PURPOSE

To determine the impact of axial traction during high resolution 3.0T MR imaging of the ankle on morphological assessment of articular cartilage and quantitative cartilage imaging parameters.

MATERIALS AND METHODS

MR images of n=25 asymptomatic ankles were acquired with and without axial traction (6kg). Coronal and sagittal T1-weighted (w) turbo spin echo (TSE) sequences with a driven equilibrium pulse and sagittal fat-saturated intermediate-w (IMfs) TSE sequences were acquired for morphological evaluation on a four-point scale (1=best, 4=worst). For quantitative assessment of cartilage degradation segmentation was performed on 2D multislice-multiecho (MSME) SE T2, steady-state free-precession (SSFP; n=8) T2 and SSFP diffusion-weighted imaging (DWI; n=8) images. Wilcoxon-tests and paired t-tests were used for statistical analysis.

RESULTS

With axial traction, joint space width increased significantly and delineation of cartilage surfaces was rated superior (P<0.05). Cartilage surfaces were best visualized on coronal T1-w images (P<0.05). Differences for cartilage matrix evaluation were smaller. Subchondral bone evaluation, motion artifacts and image quality were not significantly different between the acquisition methods (P>0.05). T2 values were lower at the tibia than at the talus (P<0.001). Reproducibility was better for images with axial traction.

CONCLUSION

Axial traction increased the joint space width, allowed for better visualization of cartilage surfaces and improved compartment discrimination and reproducibility of quantitative cartilage parameters.

Accuracy of 3D dual echo steady state (DESS) MR arthrography to quantify acetabular cartilage thickness

PURPOSE

To deploy and quantify the accuracy of 3D dual echo steady state (DESS) MR arthrography with hip traction to image acetabular cartilage. Clinical magnetic resonance imaging (MRI) sequences used to image hip cartilage often have reduced out-of-plane resolution and may lack adequate signal-to-noise to image cartilage.

MATERIALS AND METHODS

Saline was injected into four cadaver hips placed under traction. 3D DESS MRI scans were obtained before and after cores of cartilage were harvested from the acetabulum; the two MRIs were spatially aligned to reference core positions. The thickness of cartilage cores was measured under microscopy to serve as the reference standard. 3D reconstructions of cartilage and subchondral bone were generated using automatic and semiautomatic image segmentation. Cartilage thickness estimated from the 3D reconstructions was compared to physical measurements using Bland-Altman plots.

RESULTS

As revealed by the automatic segmentation mask, saline imbibed the joint space throughout the articulating surface, with the exception of the posteroinferior region in two hips. Locations where air bubbles were introduced and regions of suspected low density bone disrupted an otherwise smooth automatic segmentation mask. Automatic and semiautomatic segmentation yielded a bias ± repeatability coefficient (95% limits of agreement) of 0.10 ± 0.51 mm (-0.41 to 0.61 mm) and 0.06 ± 0.43 mm (-0.37 to 0.49 mm), respectively.

CONCLUSION

Cartilage thickness can be estimated to within ∼0.5 mm of the physical value with 95% confidence using 3D reconstructions of 3D DESS MR arthrography images. Manual correction of the automatic segmentation mask may improve reconstruction accuracy.

Diagnostic accuracy of 3.0 Tesla magnetic resonance imaging for the detection of articular cartilage lesions of the talus

BACKGROUND

Talar chondral defects can be a source of persistent ankle pain and disability. If untreated, there is an increased risk of osteoarthritis. The purpose of our study was to determine diagnostic accuracy of 3T MRI in detecting Outerbridge grades 3 and 4 articular cartilage lesions of the talus in a clinical setting, utilizing a standardized clinical MRI protocol.

METHODS

Patients who had a 3T ankle MRI and subsequent ankle surgery, by a single surgeon, were included in this study. MRI exams were performed 180 days or less before surgery. Seventy-nine ankles in 78 patients (mean age of 42.3 years) were included in this study. Mean body mass index was 26.3. A standard clinical MRI exam was performed on a 3T MRI scanner. Mean days from MRI to surgery was 39 days. All MRI exams were read and findings recorded by a musculoskeletal radiologist. Arthroscopic examination was performed by a single orthopaedic surgeon. Detailed arthroscopic findings and demographic data were collected prospectively and stored in a data registry. Of the 78 patients, 31 (39.2%) reported previous ankle surgery. Pain was the primary reason for seeking medical attention as reported by 95% of patients, followed by instability in 44% and loss of function with 42%.

RESULTS

Prevalence of Outerbridge grade 3 and 4 talar articular cartilage defects identified at arthroscopy was 17.7%. The 3T MRI demonstrated a sensitivity of 0.714, specificity of 0.738, positive predictive value of 0.370, and negative predictive value of 0.923.

CONCLUSION

Sensitivity and specificity levels were acceptable for detection of grades 3 and 4 articular cartilage defects of the talar dome using 3T MRI. The high negative predictive value may be beneficial in preoperative planning. While these values are acceptable, a high index of suspicion should be maintained in the appropriate clinical setting.

Diagnostic performance of flat-panel CT arthrography for cartilage defect detection in the ankle joint: comparison with MDCT arthrography with gross anatomy as the reference standard

OBJECTIVE

The purpose of this study is to compare the diagnostic performance and radiation exposure of flat-panel CT arthrography for cartilage defect detection in the ankle joint to standard MDCT arthrography, using gross anatomy and thermoluminescent dosimetry as reference standards.

MATERIALS AND METHODS

Ten cadaveric ankle specimens were obtained from individuals who had willed their bodies to science. Five milliliters of a mixture of diluted ioxaglate and saline were injected. Specimens were examined consecutively with the use of flat-panel CT and MDCT. Radiation doses of flat-panel CT and MDCT were recorded using thermoluminescent dosimeters. Flat-panel CT and MDCT arthrography examinations were blinded and randomly evaluated by two musculoskeletal radiologists in consensus. In each ankle specimen, eight cartilage areas were assessed separately: medial talar surface, medial talar trochlea, lateral talar trochlea, lateral talar surface, tibial malleolus, medial tibial pla-fond, lateral tibial plafond, and fibular malleolus. Findings at flat-panel CT and MDCT arthrography were compared with macroscopic assessments in 80 cartilage areas.

RESULTS

For the detection of cartilage lesions, flat-panel CT showed a sensitivity of 80%, specificity of 98%, and accuracy of 94%, and MDCT arthrography showed a sensitivity of 55%, specificity of 98%, and accuracy of 88%. Flat-panel CT and MDCT arthrography showed almost perfect (κ = 0.83) and substantial (κ = 0.65) agreement, respectively, with anatomic examination. Radiation dose was significantly lower for flat-panel CT (mean, 2.1 mGy; range, 1.1-3.0 mGy) than for MDCT (mean, 47.2 mGy; range, 39.3-53.8 mGy) (p < 0.01).

CONCLUSION

Flat-panel CT arthrography is accurate for detecting cartilage defects in the ankle joint and is an alternative to MDCT arthrography that may have better diagnostic performance and may permit the use of a lower radiation dose.

Cartilage thickness at the posterior medial femoral condyle is increased in femorotibial knee osteoarthritis: a cross-sectional CT arthrography study (Part 2)

OBJECTIVE

To evaluate the thickness of cartilage at the posterior aspect of the medial and lateral condyle in Osteoarthritis (OA) knees compared to non-OA knees using computed tomography arthrography (CTA).

DESIGN

535 consecutive knee CTAs (mean patient age = 48.7 ± 16.0; 286 males), were retrospectively analyzed. Knees were radiographically classified into OA or non-OA knees according to a modified Kellgren/Lawrence (K/L) grading scheme. Cartilage thickness at the posterior aspect of the medial and lateral femoral condyles was measured on sagittal reformations, and compared between matched OA and non-OA knees in the whole sample population and in subgroups defined by gender and age.

RESULTS

The cartilage of the posterior aspect of medial condyle was statistically significantly thicker in OA knees (2.43 mm (95% confidence interval (CI) = 2.36, 2.51)) compared to non-OA knees (2.13 mm (95%CI = 2.02, 2.17)) in the entire sample population (P < 0.001), as well as for all subgroups of patients over 40 years old (all P ≤ 0.01), except for females above 60 years old (P = 0.07). Increase in cartilage thickness at the posterior aspect of the medial condyle was associated with increasing K/L grade in the entire sample population, as well as for males and females separately (regression coefficient = 0.10-0.12, all P < 0.001). For the lateral condyle, there was no statistically significant association between cartilage thickness and OA (either presence of OA or K/L grade).

CONCLUSIONS

Cartilage thickness at the non-weight-bearing posterior aspect of the medial condyle, but not of the lateral condyle, was increased in OA knees compared to non-OA knees. Furthermore, cartilage thickness at the posterior aspect of the medial condyle increased with increasing K/L grade.

The role of radiology in the evolution of the understanding of articular disease

Both the clinical practice of radiology and the journal Radiology have had an enormous effect on our understanding of articular disease. Early descriptions of osteoarthritis (OA) appeared in Radiology. More recently, advanced physiologic magnetic resonance (MR) techniques have furthered our understanding of the early prestructural changes in patients with OA. Sodium imaging, delayed gadolinium-enhanced MR imaging of cartilage, and spin-lattice relaxation in the rotating frame (or T1ρ) sequences have advanced understanding of the pathophysiology and pathoanatomy of OA. Many pioneering articles on rheumatoid arthritis (RA) also have been published in Radiology. In the intervening decades, our understanding of the natural history of RA has been altered by these articles. Many of the first descriptions of crystalline arthropathies, including gout, calcium pyrophosphate deposition, and hydroxyapatite deposition disease, appeared in Radiology.

Toward patient-specific articular contact mechanics

The mechanics of contacting cartilage layers is fundamentally important to understanding the development, homeostasis and pathology of diarthrodial joints. Because of the highly nonlinear nature of both the materials and the contact problem itself, numerical methods such as the finite element method are typically incorporated to obtain solutions. Over the course of five decades, we have moved from an initial qualitative understanding of articular cartilage material behavior to the ability to perform complex, three-dimensional contact analysis, including multiphasic material representations. This history includes the development of analytical and computational contact analysis methods that now provide the ability to perform highly nonlinear analyses. Numerical implementations of contact analysis based on the finite element method are rapidly advancing and will soon enable patient-specific analysis of joint contact mechanics using models based on medical image data. In addition to contact stress on the articular surfaces, these techniques can predict variations in strain and strain through the cartilage layers, providing the basis to predict damage and failure. This opens up exciting areas for future research and application to patient-specific diagnosis and treatment planning applied to a variety of pathologies that affect joint function and cartilage homeostasis.

Biochemical cartilage alteration and unexpected signal recovery in T2* mapping observed in ankle joints with mobile MRI during a transcontinental multistage footrace over 4486 km

OBJECTIVE

The effect of ultra-long distance running on the ankle cartilage with regard to biochemical changes, thickness and lesions is examined in the progress of a transcontinental ultramarathon over 4486 km.

METHOD

In an observational field study, repeated follow-up scanning of 22 participants of the TransEurope FootRace (TEFR) with a 1.5 T MRI mounted on a mobile unit was performed. For quantitative biochemical and structural evaluation of cartilage a fast low angle shot (FLASH) T2* weighted gradient-echo (GRE)-, a turbo-inversion-recovery-magnitude (TIRM)- and a fat-saturated proton density (PD)-weighted sequence were utilized. Statistical analysis of cartilage T2* and thickness changes was obtained on the 13 finishers (12 male, mean age 45.4 years, BMI 23.5 kg/m²). None of the nine non-finisher (eight male, mean age 53.8 years, BMI 23.4 kg/m²) stopped the race due to ankle problems.

RESULTS

From a mean of 17.0 ms for tibial plafond and 18.0 ms for talar dome articular cartilage at baseline, nearly all observed regions of interest (ROIs) of the ankle joint cartilage showed a significant T2*-signal increase (25.6% in mean), with standard error ranging from 19% to 33% within the first 2500 km of the ultra-marathon. This initial signal behavior was followed by a signal decrease. This signal recovery (30.6% of initial increase) showed a large effect size. No significant morphological or cartilage thickness changes (at baseline 2.9 mm) were observed.

CONCLUSION

After initial T2*-increase during the first 2000-2500 km, a subsequent T2*-decrease indicates the ability of the normal cartilage matrix to partially regenerate under ongoing multistage ultramarathon burden in the ankle joints.

Deformation of articular cartilage during static loading of a knee joint--experimental and finite element analysis

Novel conical beam CT-scanners offer high resolution imaging of knee structures with i.a. contrast media, even under weight bearing. With this new technology, we aimed to determine cartilage strains and meniscal movement in a human knee at 0, 1, 5, and 30 min of standing and compare them to the subject-specific 3D finite element (FE) model. The FE model of the volunteer׳s knee, based on the geometry obtained from magnetic resonance images, was created to simulate the creep. The effects of collagen fibril network stiffness, nonfibrillar matrix modulus, permeability and fluid flow boundary conditions on the creep response in cartilage were investigated. In the experiment, 80% of the maximum strain in cartilage developed immediately, after which the cartilage continued to deform slowly until the 30 min time point. Cartilage strains and meniscus movement obtained from the FE model matched adequately with the experimentally measured values. Reducing the fibril network stiffness increased the mean strains substantially, while the creep rate was primarily influenced by an increase in the nonfibrillar matrix modulus. Changing the initial permeability and preventing fluid flow through noncontacting surfaces had a negligible effect on cartilage strains. The present results improve understanding of the mechanisms controlling articular cartilage strains and meniscal movements in a knee joint under physiological static loading. Ultimately a validated model could be used as a noninvasive diagnostic tool to locate cartilage areas at risk for degeneration.

CT assessment of the influence of dynamic loading on physiological incongruency of the canine elbow

OBJECTIVES

To present a novel technique for loading of the canine elbow joint and to quantify changes in congruency with increasing load using computed tomography.

MATERIALS AND METHODS

Five pairs of thoracic limbs were mounted at a mid stance angle in a custom made jig. Elbow joints were loaded to 0, 33, 66 and 100% of total individual cadaver bodyweight. At each load computed tomography of the elbow was performed. Joint space measurement was performed on sagittal plane central, lateral and medial compartment images at humero-radial (R1 , R2 , R3 ), humero-ulnar (U1 , U2 ) and radio-ulnar loci. The effect of loading on joint spaces was assessed (P<0.05).

RESULTS

With increasing load; for central an increase in R1 and radio-ulnar distance and decreased R3  occurred; for medial R1 increased; and for lateral R1 and radio-ulnar distance increased. The largest increases were seen in the lateral compartment.

CLINICAL SIGNIFICANCE

Significant changes in humero-radio-ulnar congruency occurred suggesting pronation of the radius with respect to the ulna was induced during loading. This movement may influence the load experienced by the medial coronoid process and could play a role in the aetiopathogenesis of medial coronoid process disease.

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.

Selective visualization of rabbit knee cartilage using MR imaging with a double-contrast agent

PURPOSE

To establish a reliable method and efficient contrast agent for selective MR imaging of articular cartilage to improve the diagnosis of cartilage disorders.

MATERIALS AND METHODS

A standard trace element replenisher (Mineric), which includes manganese chloride, cupric sulfate (both positive MR contrast agents), and colloidal ferric chloride (a negative contrast agent), was evaluated in comparison with gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) as a potential contrast agent. Normal saline was used as a control. The agents were injected into bilateral knee joints, and the entire joint block was dissected. Coronal images of femorotibial joints were obtained at 7.05 Tesla. Signal intensity ratios (SIRs) of cartilage to joint fluid were calculated for T1 and T2 values. The side effects of the agents were also investigated. Finally, histological evaluations were performed.

RESULTS

SIRs were significantly increased in the Mineric treatment group compared with the Gd-DTPA and saline treatment groups. The T1 values of cartilage and fluid were significantly decreased in the Gd-DTPA and Mineric treatment groups. The T2 values of fluid were significantly decreased in the Mineric treatment group. No apparent side effects or degenerative changes in the joints were observed.

CONCLUSION

A clinical trace element mixture was used as a novel double-contrast agent, and it exhibits selective MR contrast in articular cartilage.

Ankle joint distraction arthroplasty: why and how?

For select patients, distraction ankle arthroplasty may be a promising treatment approach for ankle osteoarthritis; however, there is still limited literature addressing its efficacy and clinical long-term results. In this article, the literature regarding the outcome after ankle distraction arthroscopy is reviewed, the indications and contraindication for this procedure are listed, our surgical technique is described, and our preliminary results with this procedure are presented.

Histomorphometric, CT arthrographic, and biomechanical mapping of the human ankle

BACKGROUND

The specific morphological and biomechanical characteristics of the osteochondral unit of the ankle joint are not yet fully understood. This anatomical study aimed to map regional thickness of the articular hyaline uncalcified cartilage and its adjacent layers of mineralized cartilage and subchondral bone as well as to measure the regional indentation stiffness of human ankle joint cartilage.

MATERIALS AND METHODS

A total of 20 pairs of human cadaver ankle joints (median age: 78 years) were evaluated by histomorphometry and multidetector row double-contrast CT arthrography for cartilage thickness in 17 distinct anatomical regions. In addition, regional distribution of the subchondral bone plate and of the mineralized cartilage was scrutinized histologically. Cartilage indentation stiffness was measured using an arthroscopic handheld device (Artscan200), especially validated for use in thin cartilage. The correlation between the thickness of different components of the osteochondral unit and the cartilage indentation stiffness was evaluated.

RESULTS

The thinnest uncalcified cartilage was measured at the anterior talar dome and the distal fibula. The thickest uncalcified cartilage was found in the mid and posterior talar dome, as well as in the tibial plafond. Mineralized cartilage and subchondral bone showed highest values at the anteromedial talar dome. Cartilage indentation stiffness showed a bicentric distribution pattern in 14/20 ankle pairs and was highest in regions with thin cartilage. Positive correlation between the thickness of the mineralized cartilage and the subchondral bone plate was found. No correlation between the thickness of the uncalcified and the mineralized cartilage could be identified.

CONCLUSION

This anatomical study provides a comprehensive mapping of the osteochondral unit of the human ankle joint in elderly people. Articular hyaline uncalcified cartilage and the subchondral bone plate showed clear regional differences and were reciprocally distributed. Cartilage indentation stiffness was inversely correlated to cartilage thickness in elderly people.

CLINICAL RELEVANCE

Thorough understanding of the osteochondral unit of the ankle joint could be helpful for clinicians and researchers in the development of improved operative repair techniques for osteochondral defects in the ankle joint, for example, in constructing specific tissue-engineered osteochondral plugs.

C-arm flat-panel CT arthrography of the wrist and elbow: first experiences in human cadavers

OBJECTIVE

To determine the optimal intra-articular iodine concentration for C-arm flat-panel computed tomography (FPCT) arthrography using advanced joint phantoms and to evaluate its application in human cadaveric wrists and elbows. Multi-detector (MD) CT served as the standard of reference.

MATERIALS AND METHODS

Joint phantoms and 10 human cadaveric wrist and elbow joints were scanned with C-arm FPCT (5-s, 8-s, and 20-s runs) and standard MDCT using different and optimal concentrations of iodinated contrast material. CT numbers of contrast material, tissue, and noise were measured and contrast-to-noise ratios (CNR) calculated for quantitative analysis. Image and depiction of cartilage, bone, and soft tissues were rated. Radiation doses were compared.

RESULTS

In FPCT, iodine concentrations positively correlated with CT numbers and noise of contrast material and with radiation dose (r = 0.713-0.996, p < 0.05 each). At an iodine concentration of 45 mg/ml, CNR of cartilage and soft tissues were highest for all FPCT acquisitions and higher than in MDCT. The 20-s FPCT run performed best for image quality and depiction of anatomical structures and was rated overall equal to MDCT (p = 0.857).

CONCLUSION

The optimal iodine concentration for C-arm FPCT arthrography in this study is 45 mg/ml, leading to superior CNR and image quality for an optimal FPCT protocol compared with standard MDCT arthrography in human cadaveric joints.

Subject-specific analysis of joint contact mechanics: application to the study of osteoarthritis and surgical planning

Advances in computational mechanics, constitutive modeling, and techniques for subject-specific modeling have opened the door to patient-specific simulation of the relationships between joint mechanics and osteoarthritis (OA), as well as patient-specific preoperative planning. This article reviews the application of computational biomechanics to the simulation of joint contact mechanics as relevant to the study of OA. This review begins with background regarding OA and the mechanical causes of OA in the context of simulations of joint mechanics. The broad range of technical considerations in creating validated subject-specific whole joint models is discussed. The types of computational models available for the study of joint mechanics are reviewed. The types of constitutive models that are available for articular cartilage are reviewed, with special attention to choosing an appropriate constitutive model for the application at hand. Issues related to model generation are discussed, including acquisition of model geometry from volumetric image data and specific considerations for acquisition of computed tomography and magnetic resonance imaging data. Approaches to model validation are reviewed. The areas of parametric analysis, factorial design, and probabilistic analysis are reviewed in the context of simulations of joint contact mechanics. Following the review of technical considerations, the article details insights that have been obtained from computational models of joint mechanics for normal joints; patient populations; the study of specific aspects of joint mechanics relevant to OA, such as congruency and instability; and preoperative planning. Finally, future directions for research and application are summarized.

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.

Evaluation of the usefulness of magnetic resonance imaging in the assessment of the thickness of the roof of the glenoid fossa of the temporomandibular joint

OBJECTIVE

The aim of this study was to evaluate the usefulness of magnetic resonance imaging (MRI) in measuring thickness of the roof of the glenoid fossa (RGF) of the temporomandibular joint (TMJ).

STUDY DESIGN

Minimum RGF thickness in 95 TMJs of 59 patients with temporomandibular disorders were measured and compared on both sagittal-section MRI and cone-beam computed tomography (CBCT). RGF thickness on MRI was also compared with MRI, CBCT, and arthrographic findings.

RESULTS

Minimum RGF thickness was greater on MRI (1.46 mm) than on CBCT (0.90 mm). Spearman's correlation coefficient by rank for these 2 types of measurements was 0.63. RGF thickness on MRI differed significantly between those with and without degenerative joint changes (1.69 vs 1.32 mm; P < .01) and between those with and without disk displacement (1.58 vs 1.35 mm; P = .04), but showed no associations with disk deformity, joint effusion, or disk perforation.

CONCLUSIONS

MRI is useful in measuring RGF thickness from diagnostic as well as radiation protection standpoints.

Subchondral bone remodeling is related to clinical improvement after joint distraction in the treatment of ankle osteoarthritis

OBJECTIVE

In osteoarthritis (OA), subchondral bone changes alter the joint's mechanical environment and potentially influence progression of cartilage degeneration. Joint distraction as a treatment for OA has been shown to provide pain relief and functional improvement through mechanisms that are not well understood. This study evaluated whether subchondral bone remodeling was associated with clinical improvement in OA patients treated with joint distraction.

METHOD

Twenty-six patients with advanced post-traumatic ankle OA were treated with joint distraction for 3 months using an Ilizarov frame in a referral center. Primary outcome measure was bone density change analyzed on computed tomography (CT) scans. Longitudinal, manually segmented CT datasets for a given patient were brought into a common spatial alignment. Changes in bone density (Hounsfield Units (HU), relative to baseline) were calculated at the weight-bearing region, extending subchondrally to a depth of 8mm. Clinical outcome was assessed using the ankle OA scale.

RESULTS

Baseline scans demonstrated subchondral sclerosis with local cysts. At 1 and 2 years of follow-up, an overall decrease in bone density (-23% and -21%, respectively) was observed. Interestingly, density in originally low-density (cystic) areas increased. Joint distraction resulted in a decrease in pain (from 60 to 35, scale of 100) and functional deficit (from 67 to 36). Improvements in clinical outcomes were best correlated with disappearance of low-density (cystic) areas (r=0.69).

CONCLUSIONS

Treatment of advanced post-traumatic ankle OA with 3 months of joint distraction resulted in bone density normalization that was associated with clinical improvement.

Validation of cartilage thickness calculations using indentation analysis

Different methods have been used to cross-validate cartilage thickness measurements from magnetic resonance images (MRIs); however, a majority of these methods rely on interpolated data points, regional mean and/or maximal thickness, or surface mean thickness for data analysis. Furthermore, the accuracy of MRI cartilage thickness measurements from commercially available software packages has not necessarily been validated and may lead to an under- or overestimation of cartilage thickness. The goal of this study was to perform a matching point-to-point validation of indirect cartilage thickness calculations using a magnetic resonance (MR) image data set with direct cartilage thickness measurements using biomechanical indentation testing at the same anatomical locations. Seven bovine distal femoral condyles were prepared and a novel phantom filled with dilute gadolinium solution was rigidly attached to each specimen. High resolution MR images were acquired, and thickness indentation analysis of the cartilage was performed immediately after scanning. Segmentation of the MR data and cartilage thickness calculation was performed using semi-automated software. Registration of MR and indentation data was performed using the fluid filled phantom. The inter- and intra-examiner differences of the measurements were also determined. A total of 105 paired MRI-indentation thickness data points were analyzed, and a significant correlation between them was found (r=0.88, p<0.0001). The mean difference (+/-std. dev.) between measurement techniques was 0.00+/-0.23 mm, with Bland-Altman limits of agreement of 0.45 mm and -0.46 mm. The intra- and inter-examiner measurement differences were 0.03+/-0.22 mm and 0.05+/-0.24 mm, respectively. This study validated cartilage thickness measurements from MR images with thickness measurements from indentation by using a novel phantom to register the image-based and laboratory-based data sets. The accuracy of the measurements was comparable to previous cartilage thickness validation studies in literature. The results of this study will aid in validating a tool for clinical evaluation of in-vivo cartilage thickness.