Measurement accuracy of focal cartilage defects from MRI and correlation of MRI graded lesions with histology: a preliminary study

Prospective Multiparametric Magnetic Resonance Monitoring of Changes in Lesions of Hyaline Cartilage of the Knee Joint After Treatment by Microfractures and Implantation of Biological Collagen Type I Matrix Implants

RATIONALE AND OBJECTIVES

This study's aims were to depict changes in cartilage quality after surgical intervention using magnetic resonance (MR) examination and in content of glycosaminoglycans chains (GAGs) after two types of surgeries - chondral defect treatment by microfractures and scaffold implantation in combination with microfractures.

MATERIALS AND METHODS

Twenty-five patients were studied: 14 with implants, 11 with microfractures. MR examination was made before surgery and 6, 12, and 18 months thereafter. Qualitative changes in cartilage were observed by means of delayed gadolinium enhanced magnetic resonance imaging of cartilage sequence using Gd-DTPA2- and Gd-DOTA. In each examination, GAGs content was determined at three locations: the defect, its surroundings, and a non-load-bearing reference area.

RESULTS

Measured indices showed no statistically significant differences in changes within the defect area when comparing the two treatment types at individual time points of 6, 12, and 18 months. In the case of microfracture treatment, more substantial decrease in GAGs concentration occurred at month 6, whereas the greatest decline occurred at month 12 when using an implant. Change in GAGs content and decline in cartilage quality were substantial also in the reference area and close surroundings.

CONCLUSIONS

Hyaline cartilage behaves as a unified whole, and change in GAGs content was marked also in locations with no morphological damage. Over the monitored period, no statistically significant difference between treatment types was noted as measured by GAGs content in the defect or its close surroundings. dGEMRIC is suitable for monitoring cartilage quality even if use of Gd-DTPA2- is not possible, because comparable results were achieved using Gd-DOTA.

Morphological MRI of knee cartilage: repeatability and reproducibility of damage evaluation and correlation with gross pathology examination

OBJECTIVE

To assess the performance of a morphological evaluation, based on a clinically relevant magnetic resonance imaging (MRI) protocol, in scoring the severity of knee cartilage damage. Specifically, to evaluate the reproducibility, repeatability, and agreement of MRI evaluation with the gross pathology examination (GPE) of the tissue.

METHODS

MRI of the knee was performed the day before surgery in 23 patients undergoing total knee arthroplasty. Osteochondral tissue resections were collected and chondral defects were scored by GPE according to a semi-quantitative scale. MR images were independently scored by four radiologists, who assessed the severity of chondral damage according to equivalent criteria. Inter- and intra-rater agreements of MRI evaluations were assessed. Correlation, precision, and accuracy metrics between MRI and GPE scores were calculated.

RESULTS

Moderate to substantial inter-rater agreement in scoring cartilage damage by MRI was found among radiologists. Intra-rater agreement was higher than 96%. A significant positive monotonic correlation between GPE and MRI scores was observed for all radiologists, although higher correlation values were obtained by radiologists with expertise in musculoskeletal radiology and/or longer experience. The accuracy of MRI scores displayed a spatial pattern, characterized by lesion overestimation in the lateral condyle and underestimation in the medial condyle with respect to GPE.

CONCLUSIONS

Evaluation of knee cartilage morphology by MRI is a reproducible and repeatable technique, which positively correlates with GPE. Clinical expertise in musculoskeletal radiology positively impacts the evaluation reliability. These findings may help to address limitations in MRI evaluation of knee chondral lesions, thus improving MRI assessment of knee cartilage.

KEY POINTS

• MRI evaluation of knee cartilage shows moderate to strong correlation with gross pathology examination. • MRI evaluation overestimates cartilage damage in the lateral condyle and underestimates it in the medial condyle. • Education and experience of the radiologist play a role in MRI evaluation of knee chondral lesions.

Cartilage evaluation in finger joints in healthy controls and early hand osteoarthritis patients using high-resolution MRI

OBJECTIVE

To compare direct evaluation of cartilage with high resolution MRI (hrMRI) to indirect cartilage evaluation using MRI inter-bone distance in hand OA patients and healthy controls.

DESIGN

41 hand OA patients and 18 healthy controls underwent hrMRI of the 2^nd and 3^rd metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints. The images were read by two independent readers using OMERACT hand OA MRI inter-bone distance score (0-3 scale) and a new hrMRI cartilage score with direct evaluation of the cartilage (0-3 scale). Inter-reader and intra-reader reliability was calculated using exact and close agreement and kappa values. The prevalence of abnormal scores and agreement between methods was assessed in both hand OA patients and healthy controls.

RESULTS

The intra- and inter-reader reliability of both scores was comparable, with exact agreement in 73-83% and close agreement in 95-100%. In hand OA patients 27% of 161 joints had both cartilage damage and loss of inter-bone distance, cartilage damage by hrMRI only was present in 20% of joints and reduced inter-bone distance only in 4% of joints. In the healthy controls, 1 of 71 joints were scored as abnormal by both hrMRI and inter bone distance scoring, 1 joint was scored as abnormal using the hrMRI cartilage score only, whereas 15% of joints had only reduced inter bone distance.

CONCLUSIONS

Direct cartilage evaluation of MCP and PIP joints using hrMRI has a good reliability, and the higher prevalence of hrMRI cartilage damage in hand OA patients and the lower prevalence in healthy controls in comparison to evaluation of inter-bone distance suggests a better validity.

Application of the Chinese Aircraft-shaped Sleeve system in the treatment of tibial shaft fractures using a suprapatellar approach for tibial intramedullary nailing: a randomised controlled trial

Background

The use of the suprapatellar approach for intramedullary nailing has recently become popular for the treatment of tibial fractures. This study aimed to investigate the effectiveness of using the Chinese Aircraft-shaped Sleeve (CASS) system on the clinical outcomes of tibial intermedullary nailing using a suprapatellar approach for the treatment of tibial fractures in a cohort of adult Chinese patients.

Methods

Magnetic resonance images (MRI) of the knee joints of 212 healthy adults with normal lower limb function from May 2011 to May 2015 were obtained from a level I Chinese regional trauma centre. Sixty inpatients at the same trauma centre who underwent treatment for tibial shaft fractures from June 2015 to June 2018 were enrolled. Tibial intramedullary nailing fixation of tibial shaft fractures via the suprapatellar approach was performed with either a CASS system or a conventional sleeve. The measurements of patellofemoral joint anatomy, the surgical time, the assessments of the patellofemoral joint cartilage conditions, and information of residual debris based on arthroscopic analysis were subsequently collected.

Results

The mean patellar angle (PA), sulcus angle (SA), sulcus width (SW) and sulcus depth (SD) were 135.40 ± 6.20°, 142.37 ± 5.33°, 33.37 ± 2.73 mm, and 4.29 ± 0.63 mm, respectively. The surgical time until entry reaming commencement and the irrigation time were significantly lower in the CASS group (P < 0.001). The difference in cartilage damage rate between groups was statistically significant (P = 0.031); the difference in residual debris conditions was not statistically significant (P = 0.1967).

Conclusion

The use of the CASS system could improve clinical outcomes of intramedullary nailing via suprapatellar approach for patients with a small patellofemoral joint space.

How precisely does ultrasonographic evaluation reflect the histological status of the articular cartilage of the knee joint?

The thickness and the grade of the articular cartilages of the knee of 34 patients who underwent total knee arthroplasty were evaluated by ultrasound (US) and by histology. The US grade correlated with the histological grade and the thickness of the articular cartilage measured by US. The thickness measured by US was significantly correlated with that measured by histology for the medial condyle. The US thickness was significantly less than the histological thickness for thicker articular cartilages. US grading and the thickness of the articular cartilages evaluated by US is sufficiently reliable to indicate their histological status.

Quantitative Assessment of Degenerative Cartilage and Subchondral Bony Lesions in a Preserved Cadaveric Knee: Propagation-Based Phase-Contrast CT Versus Conventional MRI and CT

OBJECTIVE

The aim of this study was to quantitatively assess hyaline cartilage and subchondral bone conditions in a fully preserved cadaveric human knee joint using high-resolution x-ray propagation-based phase-contrast imaging (PBI) CT and to compare the performance of the new technique with conventional CT and MRI.

MATERIALS AND METHODS

A cadaveric human knee was examined using an x-ray beam of 60 keV, a detector with a 90-mm² FOV, and a pixel size of 46 × 46 μm². PBI CT images were reconstructed with both the filtered back projection algorithm and the equally sloped tomography method. Conventional 3-T MRI and CT were also performed. Measurements of cartilage thickness, cartilage lesions, International Cartilage Repair Society scoring, and detection of subchondral bone changes were evaluated. Visual inspection of the specimen akin to arthroscopy was conducted and served as a standard of reference for lesion detection.

RESULTS

Loss of cartilage height was visible on PBI CT and MRI. Quantification of cartilage thickness showed a strong correlation between the two modalities. Cartilage lesions appeared darker than the adjacent cartilage on PBI CT. PBI CT showed similar agreement to MRI for depicting cartilage substance defects or lesions compared with the visual inspection. The assessment of subchondral bone cysts showed moderate to strong agreement between PBI CT and CT.

CONCLUSION

In contrast to the standard clinical methods of MRI and CT, PBI CT is able to simultaneously depict cartilage and bony changes at high resolution. Though still an experimental technique, PBI CT is a promising high-resolution imaging method to evaluate comprehensive changes of osteoarthritic disease in a clinical setting.

Lesion Size Does Not Predict Outcomes in Fresh Osteochondral Allograft Transplantation

BACKGROUND

Cartilage repair algorithms use lesion size to choose surgical techniques when selecting a cartilage repair procedure. The association of fresh osteochondral allograft (OCA) size with graft survivorship and subjective patient outcomes is still unknown.

PURPOSE

To determine if lesion size (absolute or relative) affects outcomes after OCA transplantation.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

The study included 156 knees in 143 patients who underwent OCA transplantation from 1998 to 2014 for isolated femoral condyle lesions. The mean age was 29.6 ± 11.4 years, and 62.9% were male. The majority of patients (62.2%) presented for cartilage repair because of osteochondritis dissecans. The mean graft area, used as a surrogate for absolute size of the lesion, was 6.4 cm² (range, 2.3-11.5 cm²). The relative size of the lesion was calculated as the tibial width ratio (TWR; ratio of graft area to tibial width) and affected femoral condyle ratio (AFCR; ratio of graft area to affected femoral condyle width) using preoperative radiographs. All patients had a minimum follow-up of 2 years. Further surgical procedures were documented, and graft failure was defined as revision OCA transplantation or conversion to arthroplasty. International Knee Documentation Committee (IKDC) pain, function, and total scores were obtained. Satisfaction with OCA transplantation was assessed.

RESULTS

The mean follow-up among patients with grafts remaining in situ was 6.0 years (range, 1.9-16.5 years). The OCA failure rate was 5.8%. Overall survivorship of the graft was 97.2% at 5 years and 93.5% at 10 years. No difference in postoperative outcomes between groups was found in absolute or relative size. Change in IKDC scores (from preoperative to latest follow-up) was greater for knees with large lesions compared to knees with small lesions, among all measurement methods. Overall satisfaction with the results of OCA transplantation was 89.8%.

CONCLUSION

The size of the lesion, either absolute or relative, does not influence outcomes after OCA transplantation for isolated femoral condyle lesions of the knee.

Stem Cells for Cartilage Repair: Preclinical Studies and Insights in Translational Animal Models and Outcome Measures

Due to the restricted intrinsic capacity of resident chondrocytes to regenerate the lost cartilage postinjury, stem cell-based therapies have been proposed as a novel therapeutic approach for cartilage repair. Moreover, stem cell-based therapies using mesenchymal stem cells (MSCs) or induced pluripotent stem cells (iPSCs) have been used successfully in preclinical and clinical settings. Despite these promising reports, the exact mechanisms underlying stem cell-mediated cartilage repair remain uncertain. Stem cells can contribute to cartilage repair via chondrogenic differentiation, via immunomodulation, or by the production of paracrine factors and extracellular vesicles. But before novel cell-based therapies for cartilage repair can be introduced into the clinic, rigorous testing in preclinical animal models is required. Preclinical models used in regenerative cartilage studies include murine, lapine, caprine, ovine, porcine, canine, and equine models, each associated with its specific advantages and limitations. This review presents a summary of recent in vitro data and from in vivo preclinical studies justifying the use of MSCs and iPSCs in cartilage tissue engineering. Moreover, the advantages and disadvantages of utilizing small and large animals will be discussed, while also describing suitable outcome measures for evaluating cartilage repair.

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.

Accuracy of magnetic resonance imaging to detect cartilage loss in severe osteoarthritis of the first carpometacarpal joint: comparison with histological evaluation

Background

Magnetic resonance imaging (MRI) is increasingly used for research in hand osteoarthritis, but imaging the thin cartilage layers in the hand joints remains challenging. We therefore assessed the accuracy of MRI in detecting cartilage loss in patients with symptomatic osteoarthritis of the first carpometacarpal (CMC1) joint.

Methods

Twelve patients scheduled for trapeziectomy to treat severe symptomatic osteoarthritis of the CMC1 joint underwent a preoperative high resolution 3D spoiled gradient (SPGR) MRI scan. Subsequently, the resected trapezium was evaluated histologically. The sections were scored for cartilage damage severity (Osteoarthritis Research Society International (OARSI) score), and extent of damage (percentage surface area). Each MRI scan was scored for the area of normal cartilage, partial cartilage loss and full cartilage loss. The percentages of the total surface area with any cartilage loss and full-thickness cartilage loss were calculated using MRI and histological evaluation.

Results

MRI and histological evaluation both identified large areas of overall cartilage loss. The median (IQR) surface area of any cartilage loss on MRI was 98% (82–100%), and on histological assessment 96% (87–98%). However, MRI underestimated the extent of full-thickness cartilage loss. The median (IQR) surface area of full-thickness cartilage loss on MRI was 43% (22–70%), and on histological evaluation 79% (67–85%). The difference was caused by a thin layer of high signal on the articulating surface, which was interpreted as damaged cartilage on MRI but which was not identified on histological evaluation.

Conclusions

Three-dimensional SPGR MRI of the CMC1 joint demonstrates overall cartilage damage, but underestimates full-thickness cartilage loss in patients with advanced osteoarthritis.

Baseline cartilage quality is associated with voxel-based T1ρ and T2 following ACL reconstruction: A multicenter pilot study

In this multi-center study, voxel-based relaxometry (VBR), a novel technique to automatically quantify localized cartilage change, was used to investigate T_1ρ and T₂ relaxation times of patients with anterior cruciate ligament (ACL) tears at the time of injury and 6 months after reconstructive surgery. Sixty-four ACL-injured patients from three sites underwent bilateral 3T MR T_1ρ and T₂ mapping; 56 patients returned 6 months after surgery. Cross-sectional and longitudinal VBR comparisons of relaxation times were calculated. Noyes Score (NS) clinical grades of cartilage lesions were noted at both times and correlated with relaxation times. Lastly, patients were divided into two groups based on baseline NS grades in the injured knee. T_1ρ times of each group were assessed with VBR and compared. Results illustrate the feasibility of VBR for efficiently analyzing data from patients at different sites. Significant relaxation time elevations at baseline were observed in the injured knee compared to the uninjured, particularly in the posterolateral tibia (pLT). Longitudinally, a decrease was observed in the pLT and patella, while an increase was noted in the trochlea. Stratifying patients by baseline lesion presence revealed T_1ρ increased more 6 months after surgery in patients with lesions. Such findings propose that the presence of cartilage lesions at baseline are associated with the longitudinal progression of T_1ρ and T₂ after ACL injury, and may contribute to early cartilage degeneration. Furthermore, the speed and localized specificity of automatic VBR analysis may translate well for clinical application, as seen in this multicenter study. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:688-698, 2017.

THE USE OF SMALL FIELD-OF-VIEW 3 TESLA MAGNETIC RESONANCE IMAGING FOR IDENTIFICATION OF ARTICULAR CARTILAGE DEFECTS IN THE CANINE STIFLE: AN EX VIVO CADAVERIC STUDY

Noninvasive identification of canine articular cartilage injuries is challenging. The objective of this prospective, cadaveric, diagnostic accuracy study was to determine if small field-of-view, three tesla magnetic resonance imaging (MRI) was an accurate method for identifying experimentally induced cartilage defects in canine stifle joints. Forty-two canine cadaveric stifles (n = 6/group) were treated with sham control, 0.5, 1.0, or 3.0 mm deep defects in the medial or lateral femoral condyle. Proton density-weighted, T1-weighted, fast-low angle shot, and T2 maps were generated in dorsal and sagittal planes. Defect location and size were independently determined by two evaluators and compared to histologic measurements. Accuracy of MRI was determined using concordance correlation coefficients. Defects were identified correctly in 98.8% (Evaluator 1) and 98.2% (Evaluator 2) of joints. Concordance correlation coefficients between MRI and histopathology were greater for defect depth (Evaluator 1: 0.68-0.84; Evaluator 2: 0.76-0.83) compared to width (Evaluator 1: 0.30-0.54; Evaluator 2: 0.48-0.68). However, MRI overestimated defect depth (histopathology: 1.65 ± 0.94 mm; Evaluator 1, range of means: 2.07-2.38 mm; Evaluator 2, range of means: 2-2.2 mm) and width (histopathology: 6.98 ± 1.32 mm; Evaluator 1, range of means: 8.33-8.8 mm; Evaluator 2, range of means: 6.64-7.16 mm). Using the paired t-test, the mean T2 relaxation time of cartilage defects was significantly greater than the mean T2 relaxation time of adjacent normal cartilage for both evaluators (P < 0.0001). Findings indicated that MRI is an accurate method for identifying cartilage defects in the cadaveric canine stifle. Additional studies are needed to determine the in vivo accuracy of this method.

Comparison of 3D turbo spin-echo SPACE sequences with conventional 2D MRI sequences to assess the shoulder joint

PURPOSE

To determine the accuracy and reliability of three-dimensional (3D) T1- and proton density (PD)-weighted turbo spin-echo (TSE) sampling perfection with application-optimized contrasts using different flip-angle evolution (SPACE) compared with conventional 2D sequences in assessment of the shoulder-joint.

MATERIALS AND METHODS

Ninety-three subjects were examined on a 3-T MRI system with both conventional 2D-TSE sequences in T1-, T2- and PD-weighting and 3D SPACE sequences in T1- and PD-weighting. All examinations were assessed independently by two reviewers for common pathologies of the shoulder-joint. Agreement between 2D- and 3D-sequences and inter-observer-agreement was evaluated using kappa-statistics.

RESULTS

Using conventional 2D TSE sequences as standard of reference, sensitivity, specificity, and accuracy values of 3D SPACE were 81.8%, 95.1%, and 93.5% for injuries of the supraspinatus-tendon (SSP), 81.3%, 93.5%, and 91.4% for the cartilage layer and 82.4%, 98.5%, and 97.5% for the long biceps tendon. Concordance between 2D and 3D was almost perfect for tendinopathies of the SSP (κ=0.85), osteoarthritis (κ=1), luxation of the biceps tendon (κ=1) and adjacent bone marrow (κ=0.92). Inter-observer-agreement was generally higher for conventional 2D TSE sequences (κ, 0.23-1.0), when compared to 3D SPACE sequences (κ, -0.33 to 1.0) except for disorders of the long biceps tendon and supraspinatus tendon rupture.

CONCLUSION

Because of substantial and almost perfect concordance with conventional 2D TSE sequences for common shoulder pathologies, MRI examination-time can be reduced by nearly 40% (up to 11 min) using 3D-SPACE without loss of information.

In vitro assessment of knee MRI in the presence of metal implants comparing MAVRIC-SL and conventional fast spin echo sequences at 1.5 and 3 T field strength

PURPOSE

To assess lesion detection and artifact size reduction of a multiacquisition variable-resonance image combination, slice encoding for metal artifact correction (MAVRIC-SEMAC) hybrid sequence (MAVRIC-SL) compared to standard sequences at 1.5T and 3T in porcine knee specimens with metal hardware.

MATERIALS AND METHODS

Artificial cartilage and bone lesions of defined size were created in the proximity of titanium and steel screws with 2.5 mm diameter in 12 porcine knee specimens and were imaged at 1.5T and 3T magnetic resonance imaging (MRI) with MAVRIC-SL PD and short T1 inversion recovery (STIR), standard fast spin echo (FSE) T2 PD, and STIR and fat-saturated T2 FSE sequences. Three radiologists blinded to the lesion locations assessed lesion detection rates on randomized images for each sequence using receiver operating characteristic (ROC). Artifact length and width were measured.

RESULTS

Metal artifact sizes were largest in the presence of steel screws at 3T (FSE T2 FS: 28.7 cm(2) ) and 1.5T (16.03 cm(2) ). MAVRIC-SL PD and STIR reduced artifact sizes at both 3T (1.43 cm(2) ; 2.46 cm(2) ) and 1.5T (1.16 cm(2) ; 1.59 cm(2) ) compared to FS T2 FSE sequences (27.57 cm(2) ; 13.20 cm(2) ). At 3T, ROC-derived AUC values using MAVRIC-SL sequences were significantly higher compared to standard sequences (MAVRIC-PD: 0.87, versus FSE-T2 -FS: 0.73 [P = 0.025]; MAVRIC-STIR: 0.9 vs. T2 -STIR: 0.78 [P = 0.001] and vs. FSE-T2 -FS: 0.73 [P = 0.026]). Similar values were observed at 1.5T. Comparison of 3T and 1.5T showed no significant differences (MAVRIC-SL PD: P = 0.382; MAVRIC-SL STIR: P = 0.071).

CONCLUSION

MAVRIC-SL sequences provided superior lesion detection and reduced metal artifact size at both 1.5T and 3T compared to conventionally used FSE sequences. No significant disadvantage was found comparing MAVRIC-SL at 3T and 1.5T, although metal artifacts at 3T were larger. J. Magn. Reson. Imaging 2015;41:1291-1299. © 2014 Wiley Periodicals, Inc.

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.

Preoperative MRI underestimates articular cartilage defect size compared with findings at arthroscopic knee surgery

BACKGROUND

Magnetic resonance imaging (MRI) is widely used as a preoperative tool to estimate the size of articular cartilage defects to optimize treatment selection. However, the reliability of MRI sizing of cartilage defects is not well understood. Hypothesis/

PURPOSE

The purpose of this investigation was to compare the size of knee articular cartilage defects on MRI to arthroscopic visualization after debridement. It was hypothesized that MRI sizing would produce measurements that were no different than those made during arthroscopic knee surgery.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

Seventy-seven patients (age [mean ± SD], 38 ± 10.7 years) who met inclusion criteria underwent preoperative knee MRI of at least 1.5 T within 1 year of arthroscopic knee surgery for a high-grade cartilage defect. Postdebridement defect sizes were obtained from intraoperative surgery notes and compared with retrospective MRI estimates.

RESULTS

Ninety-two total cartilage defects were analyzed with an average of 1.2 high-grade defects per knee and average postdebridement defect area of 2.99 cm(2) per lesion (95% CI, 1.63-2.26 cm(2)). Preoperative MRI analysis estimated a lesion area that was an average of 1.04 cm(2) smaller (95% CI, 0.70-1.39 cm(2); P < .0001). In 74% of the lesions analyzed, defect size was larger on arthroscopic visualization than was estimated by MRI sizing. On average, MRI underestimated the defect area by 70% compared with arthroscopic visualization.

CONCLUSION

Magnetic resonance imaging underestimates the size of articular cartilage defects compared with final postdebridement size as measured during arthroscopic knee surgery. Thus, before arthroscopic surgery, orthopaedic surgeons should consider treatment strategies that are appropriate for a larger defect than predicted by preoperative MRI.

Multimodal evaluation of tissue-engineered cartilage

Tissue engineering (TE) has promise as a biological solution and a disease modifying treatment for arthritis. Although cartilage can be generated by TE, substantial inter- and intra-donor variability makes it impossible to guarantee optimal, reproducible results. TE cartilage must be able to perform the functions of native tissue, thus mechanical and biological properties approaching those of native cartilage are likely a pre-requisite for successful implantation. A quality-control assessment of these properties should be part of the implantation release criteria for TE cartilage. Release criteria should certify that selected tissue properties have reached certain target ranges, and should be predictive of the likelihood of success of an implant in vivo. Unfortunately, it is not currently known which properties are needed to establish release criteria, nor how close one has to be to the properties of native cartilage to achieve success. Achieving properties approaching those of native cartilage requires a clear understanding of the target properties and reproducible assessment methodology. Here, we review several main aspects of quality control as it applies to TE cartilage. This includes a look at known mechanical and biological properties of native cartilage, which should be the target in engineered tissues. We also present an overview of the state of the art of tissue assessment, focusing on native articular and TE cartilage. Finally, we review the arguments for developing and validating non-destructive testing methods for assessing TE products.

Effect of long-term vigorous physical activity on healthy adult knee cartilage

INTRODUCTION

Whether participation in long-term vigorous physical activity affects knee cartilage is unclear and may depend on the state of knee health. We examined the association between vigorous physical activity during a decade and the subsequent changes in knee cartilage among healthy adults. We then examined whether this effect differed in those with and without bone marrow lesions (BMLs), as an indicator of preclinical joint damage.

METHODS

A total of 297 healthy adults age 50-79 yr were recruited. Physical activity was assessed via questionnaire at baseline (1990-1994) and at follow-up (2003-2004), and a score for persistence of vigorous physical activity score was determined. Each subject underwent knee magnetic resonance imaging in 2003-2004 and in 2006-2007. Cartilage volume, defects, and BMLs were measured using validated methods.

RESULTS

Persistent participation in vigorous physical activity was associated with worsening of medial knee cartilage defects (odds ratio (OR) = 1.5, 95% confidence interval (CI) = 1.0-2.3). In the subgroup with BMLs, but not in those without BML, persistent vigorous physical activity was associated with a significant worsening of medial knee cartilage defects (OR = 3.4, 95% CI = 1.0-16.5) and a trend toward an increased rate of loss of medial knee cartilage volume (21.6 mm·yr, 95% CI = -0.4 to 43.6).

CONCLUSIONS

In knees with BMLs, persistent participation in vigorous physical activity was associated with adverse cartilage changes in the medial compartment. This suggests that the long-term effects of vigorous physical activity may depend on the preexisting health of the joint.

Mechanism of disease in early osteoarthritis: application of modern MR imaging techniques -- a technical report

The application of biomolecular magnetic resonance imaging becomes increasingly important in the context of early cartilage changes in degenerative and inflammatory joint disease before gross morphological changes become apparent. In this limited technical report, we investigate the correlation of MRI T1, T2 and T1ρ relaxation times with quantitative biochemical measurements of proteoglycan and collagen contents of cartilage in close synopsis with histologic morphology. A recently developed MRI sequence, T1ρ, was able to detect early intracartilaginous degeneration quantitatively and also qualitatively by color mapping demonstrating a higher sensitivity than standard T2-weighted sequences. The results correlated highly with reduced proteoglycan content and disrupted collagen architecture as measured by biochemistry and histology. The findings lend support to a clinical implementation that allows rapid visual capturing of pathology on a local, millimeter level. Further information about articular cartilage quality otherwise not detectable in vivo, via normal inspection, is needed for orthopedic treatment decisions in the present and future.

Use magnetic resonance imaging to assess articular cartilage

Magnetic resonance imaging (MRI) enables a noninvasive, three-dimensional assessment of the entire joint, simultaneously allowing the direct visualization of articular cartilage. Thus, MRI has become the imaging modality of choice in both clinical and research settings of musculoskeletal diseases, particular for osteoarthritis (OA). Although radiography, the current gold standard for the assessment of OA, has had recent significant technical advances, radiographic methods have significant limitations when used to measure disease progression. MRI allows accurate and reliable assessment of articular cartilage which is sensitive to change, providing the opportunity to better examine and understand preclinical and very subtle early abnormalities in articular cartilage, prior to the onset of radiographic disease. MRI enables quantitative (cartilage volume and thickness) and semiquantitative assessment of articular cartilage morphology, and quantitative assessment of cartilage matrix composition. Cartilage volume and defects have demonstrated adequate validity, accuracy, reliability and sensitivity to change. They are correlated to radiographic changes and clinical outcomes such as pain and joint replacement. Measures of cartilage matrix composition show promise as they seem to relate to cartilage morphology and symptoms. MRI-derived cartilage measurements provide a useful tool for exploring the effect of modifiable factors on articular cartilage prior to clinical disease and identifying the potential preventive strategies. MRI represents a useful approach to monitoring the natural history of OA and evaluating the effect of therapeutic agents. MRI assessment of articular cartilage has tremendous potential for large-scale epidemiological studies of OA progression, and for clinical trials of treatment response to disease-modifying OA drugs.

Preoperative Measurement of Cartilage Defects by MRI Underestimates Lesion Size

OBJECTIVE

Anecdotal evidence suggests that MRI frequently underestimates the size of cartilage defects when compared with final lesion size after debridement of all degenerated tissue. This has potential implications for the choice of cartilage repair technique since most treatment algorithms are primarily driven by defect size. We conducted an investigation comparing size estimates based on preoperative MRI with final defect size after debridement. Our aim was to provide surgeons with more objective data to assist in predicting true defect size based on MRI scanning.

DESIGN

Patients were included in this retrospective study if they had undergone preoperative MRI and open cartilage repair within 12 months to minimize potential confounding by defect progression on MRI. Defect sizes measured after debridement were obtained from surgical notes and compared with MRI size estimates by 2 musculoskeletal radiologists.

RESULTS

Thirty-eight patients were enrolled with a median age of 37 years, median number of 1.7 defects, and a total median defect area of 6 cm(2) per knee. Preoperative MRI scanning had predicted a median defect area of 3.6 cm(2). This reflected a difference of 65% (P < 0.001) between MRI and final defect area after debridement when 85% of all individual defects were larger than predicted by preoperative MRI.

CONCLUSIONS

Our study compared the size of cartilage defects measured by preoperative MRI with surgical measurements after debridement. On average, the final total defect area per knee was 65% larger than estimated preoperatively by MRI. Individual defects were larger than predicted by 47% to 377%, depending on defect location.

Arthroscopic Measurement of Cartilage Lesions of the Knee Condyle: Principles and Experimental Validation of a New Method

PURPOSE

To present a new method of arthroscopic measurement of the surface and location of condylar lesions.

METHODS

We propose measuring the height of the condylar lesion by using the lesion's arc (Δ°) obtained from the difference between the angle of flexion at the beginning of the lesion and the angle of flexion at the end of the lesion. The first goal of the study was to determine the intra and inter reliability of the lesion's arc. Experiment 1: 20 deep lesions were evaluated using the lesional arc by two arthroscopists. Experiment 2: In a second series of 20 lesions, the flexion angles of the knees were recorded using a goniometer. All 10 knees (5 in each series) were then disarticulated and the true lesion arc was checked with a goniometer to assess the validity of the scopic measurements. The second goal was to obtain the height of the lesion from the lesion's arc. The lesion arc Δ° of the condylar is converted into height (millimeters) on the basis of a table obtained from 5 standard profiles of the lateral X-ray of the knee.

RESULTS

Experiment 1: The intra observer reliability was good but the inter observer reliability was poor. Experiment 2: The intra and inter observers' reliability were good. On the anatomic control after disarticulating the knee, the confidence interval was narrower when using the goniometer.

CONCLUSIONS

We propose a simple, reliable method to measure the height of a condylar lesion with the lesion's arc during arthroscopy.

Systematic review of the concurrent and predictive validity of MRI biomarkers in OA

OBJECTIVE

To summarize literature on the concurrent and predictive validity of MRI-based measures of osteoarthritis (OA) structural change.

METHODS

An online literature search was conducted of the OVID, EMBASE, CINAHL, PsychInfo and Cochrane databases of articles published up to the time of the search, April 2009. 1338 abstracts obtained with this search were preliminarily screened for relevance by two reviewers. Of these, 243 were selected for data extraction for this analysis on validity as well as separate reviews on discriminate validity and diagnostic performance. Of these 142 manuscripts included data pertinent to concurrent validity and 61 manuscripts for the predictive validity review. For this analysis we extracted data on criterion (concurrent and predictive) validity from both longitudinal and cross-sectional studies for all synovial joint tissues as it relates to MRI measurement in OA.

RESULTS

Concurrent validity of MRI in OA has been examined compared to symptoms, radiography, histology/pathology, arthroscopy, CT, and alignment. The relation of bone marrow lesions, synovitis and effusion to pain was moderate to strong. There was a weak or no relation of cartilage morphology or meniscal tears to pain. The relation of cartilage morphology to radiographic OA and radiographic joint space was inconsistent. There was a higher frequency of meniscal tears, synovitis and other features in persons with radiographic OA. The relation of cartilage to other constructs including histology and arthroscopy was stronger. Predictive validity of MRI in OA has been examined for ability to predict total knee replacement (TKR), change in symptoms, radiographic progression as well as MRI progression. Quantitative cartilage volume change and presence of cartilage defects or bone marrow lesions are potential predictors of TKR.

CONCLUSION

MRI has inherent strengths and unique advantages in its ability to visualize multiple individual tissue pathologies relating to pain and also predict clinical outcome. The complex disease of OA which involves an array of tissue abnormalities is best imaged using this imaging tool.

Proton density-weighted MR imaging of the knee: fat suppression versus without fat suppression

OBJECTIVE

To prospectively evaluate the diagnostic accuracy of proton density-weighted imaging with and without fat suppression for detecting meniscal tears.

MATERIALS AND METHODS

The study involved 48 patients who underwent arthroscopy less than 3 months after proton density-weighted imaging with and without fat suppression. Sagittal images were independently reviewed by two radiologists for the presence of meniscal tears. Medial and lateral menisci were separately analyzed in terms of anterior horn, body, and posterior horn. Interobserver agreement was assessed using κ coefficients. The McNemar test was used to determine any differences between the two methods in terms of sensitivity and specificity. Arthroscopy findings were used as the diagnostic reference standard.

RESULTS

Arthroscopy revealed 71 tears involving 85 meniscal segments: 34 medial meniscal segments and 51 lateral meniscal segments. The sensitivity, specificity, and accuracy of each radiologist were 95% (81/85), 92% (186/203), and 93% (267/288), and 93% (79/85), 93% (189/203), and 93% (268/288) when using fat-suppressed proton density-weighted imaging, and 91% (77/85), 93% (189/203), and 92% (266/288), and 91% (77/85), 93% (188/203), and 92% (265/288) when using proton density-weighted imaging without fat suppression, respectively. Interobserver agreement for meniscal tears was very high with proton-weighted imaging with (κ = 0.87) or without (κ = 0.86) fat suppression. There were no significant differences for detection of medial meniscal tears when using proton density-weighted imaging with or without fat suppression for both readers (p > 0.05).

CONCLUSION

Fat-suppressed proton density-weighted imaging can replace proton density-weighted imaging without fat suppression for the detection of meniscal tears.

Fat-suppressed spoiled gradient-recalled imaging of equine metacarpophalangeal articular cartilage

The purpose was to evaluate the capacity of 1.5 T magnetic resonance (MR) imaging to assess articular cartilage in racehorses with naturally occurring metacarpophalangeal joint osteoarthritis. A sagittal, three-dimensional spoiled gradient-recalled echo (SPGR) with fat saturation (FS) sequence was acquired ex vivo on 20 joints. Following joint dissection, specific areas on the third metacarpal condyle were designated for subsequent sampling for histologic cartilage thickness measurement and modified Mankin scoring. Cartilage thickness was measured and cartilage signal intensity was also graded (0-3) on MR images at these selected metacarpal sites. Cartilage structure was graded (0-3) macroscopically and on MR images by two examiners in defined subregions of the proximal phalanx, third metacarpal, and proximal sesamoid bones. There was good precision (mean error 0.11 mm) and moderate correlation (r = 0.44; P < 0.0001) of cartilage thickness measurements between MR images (0.90 +/- 0.17mm) and histology (0.79 +/- 0.16 mm). There was moderate correlation between modified Mankin histologic score and signal intensity of cartilage (r = 0.36; P < 0.01) or MR cartilage structure assessment (r = 0.49, P > 0.001) on SPGR-FS. The sensitivity to detect full-thickness cartilage erosion on MR was only moderate (0.56), and these lesions were often underestimated, particularly when linear in nature. However, the specificity to detect such lesions on MR was high (0.92). While few limitations were identified, the use of a clinically applicable SPGR-FS sequence allows a reasonably accurate method to assess structural changes affecting the articular cartilage of the equine metacarpophalangeal joint.

Correlation of signal attenuation-based quantitative magnetic resonance imaging with quantitative computed tomographic measurements of subchondral bone mineral density in metacarpophalangeal joints of horses

OBJECTIVE

To evaluate the ability of signal attenuation-based quantitative magnetic resonance imaging (QMRI) to estimate subchondral bone mineral density (BMD) as assessed via quantitative computed tomography (QCT) in osteoarthritic joints of horses.

SAMPLE POPULATION

20 metacarpophalangeal joints from 10 horse cadavers.

PROCEDURES

Magnetic resonance (MR) images (dorsal and transverse T1-weighted gradient recalled echo [GRE] and dorsal T2*-weighted GRE fast imaging employing steady-state acquisition [T2*-FIESTA]) and transverse single-slice computed tomographic (CT) images of the joints were acquired. Magnetic resonance signal intensity (SI) and CT attenuation were quantified in 6 regions of interest (ROIs) in the subchondral bone of third metacarpal condyles. Separate ROIs were established in the air close to the joint and used to generate corrected ratios and SIs. Computed tomographic attenuation was corrected by use of a calibration phantom to obtain a K(2)HPO(4)-equivalent density of bone. Correlations between QMRI performed with different MR imaging sequences and QCT measurements were evaluated. The intraobserver repeatability of ROI measurements was tested for each modality.

RESULTS

Measurement repeatability was excellent for QCT (R(2) = 98.3%) and QMRI (R(2) = 98.8%). Transverse (R(2) = 77%) or dorsal (R(2) = 77%) T1-weighted GRE and QCT BMD measurements were negatively correlated, as were dorsal T2*-FIESTA and QCT (R(2) = 80%) measurements. Decreased bone SI during MR imaging linearly reflected increased BMD.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of this ex vivo study suggested that signal attenuation-based QMRI was a reliable, clinically applicable method for indirect estimation of subchondral BMD in osteoarthritic metacarpophalangeal joints of horses.

Non-invasive MRI assessment of the articular cartilage in clinical studies and experimental settings

Attrition and eventual loss of articular cartilage are important elements in the pathophysiology of osteoarthritis (OA). Preventing the breakdown of cartilage is believed to be critical to preserve the functional integrity of a joint. Chondral injuries are also common in the knee joint, and many patients benefit from cartilage repair. Magnetic resonance imaging (MRI) and advanced digital post-processing techniques have opened possibilities for in vivo analysis of cartilage morphology, structure, and function in healthy and diseased knee joints. Techniques of semi-quantitative scoring of human knee cartilage pathology and quantitative assessment of human cartilage have been developed. Cartilage thickness and volume have been quantified in humans as well as in small animals. MRI detected cartilage loss has been shown to be more sensitive than radiographs detecting joint space narrowing. It is possible to longitudinally study knee cartilage morphology with enough accuracy to follow the disease-caused changes and also evaluate the therapeutic effects of chondro-protective drugs. There are also several MRI methods that may allow evaluation of the glycosaminoglycan matrix or collagen network of articular cartilage, and may be more sensitive for the detection of early changes. The clinical relevance of these methods is being validated. With the development of new therapies for OA and cartilage injury, MR images will play an important role in the diagnosis, staging, and evaluation of the effectiveness of these therapies.

Is there a characteristic distal tarsal subchondral bone plate thickness pattern in horses with no history of hindlimb lameness?

REASONS FOR PERFORMING STUDY

Osteoarthritis (OA) is a common cause of distal tarsal pain, but disease development is poorly understood. Awareness of normal tarsal structure and function is important in order to understand the pathogenesis of OA. Thickening of the subchondral bone (SCB) plate has been related to the development of OA, but SCB plate patterns in the equine tarsus have not been documented.

HYPOTHESES

There is a repeatable pattern of SCB thickness across the distal tarsal joints, and specifically that thickness would be greatest dorsally and laterally.

METHODS

Twenty cadaver tarsi were collected from mature horses that had undertaken low-level exercise only with no history of hindlimb lameness. Magnetic resonance images were acquired using a high-resolution sagittal 3-dimensional T1-weighted spoiled gradient echo sequence. Subchondral bone thickness was measured on sagittal images at dorsal and plantar locations on the proximal and distal aspects of the central (CT) and third (T3) tarsal bones and proximal aspect of the third metatarsal bone (Mt3).

RESULTS

On the proximal aspect of CT, medial and lateral SCB thickness were significantly greater than midline. On the distal aspect of CT and T3 and proximal Mt3, lateral SCB thickness was significantly greater than medial and midline sites. Dorsal SCB thickness was greatest on the proximal and distal aspects of CT and proximal Mt3. Subchondral bone accounted for a greater proportion of CT and T3 on the dorsal aspect than the plantar.

CONCLUSIONS

There is a repeatable pattern of SCB thickness in the distal tarsal bones of horses with no history of hindlimb lameness. This reflects the pattern of loading across the joints.

POTENTIAL RELEVANCE

This study provides evidence of a consistent osteochondral pattern in the equine tarsus for reference in identification of osteoarticular pathologies.

Alteration of distal tarsal subchondral bone thickness pattern in horses with tarsal pain

REASONS FOR PERFORMING STUDY

Understanding of the development of pathology and source of pain in distal tarsal osteoarthritis is poorly understood. Magnetic resonance imaging is often used in the analysis of human osteoarthritis (OA) because it is sensitive to early changes.

HYPOTHESIS

In association with distal tarsal joint (DTJ) pain, there will be an alteration in the characteristic subchondral bone (SCB) thickness pattern of horses with no history of pain when subjected to low-level exercise.

METHODS

Sixteen cadaver tarsal joints were collected from 9 mature horses with a history of tarsal pain and radiographic evidence of OA; 3 cadaver tarsi were collected from 2 mature horses with a history of tarsal pain and no radiographic abnormality. Magnetic resonance images were acquired using high-resolution sagittal 3D T1 weighted spoiled gradient echo sequence. Subchondral bone thickness was measured on sagittal images at dorsal and plantar locations on the proximal and distal aspects of the central (CT) and third (T3) tarsal bones and proximal aspect of the third metatarsal bone (MT3).

RESULTS

In tarsi with radiographic evidence of OA medial and lateral SCB thicknesses were greater than midline on the proximal and distal aspects of CT and T3. Lateral SCB thickness was greater than medial on the proximal aspect of MT3. There was an increase in SCB thickness at the majority of sites compared with normal horses. There were too few joints in the group without radiographic changes to analyse statistically. In painful tarsi SCB thickness was greater medially than laterally at all sites. In horses without tarsal pain all lateral sites had greater SCB thickness, except the proximal aspect of CT.

CONCLUSIONS

There is alteration of normal SCB thickness patterns in painful tarsi. Different thickness patterns could represent different types of pathological processes.

POTENTIAL CLINICAL RELEVANCE

Further work is required to elucidate the pathological processes leading to OA of the DTJs.

Evaluation of histological scoring systems for tissue-engineered, repaired and osteoarthritic cartilage

OBJECTIVE

Regeneration of hyaline cartilage has been the focus of an increasing number of research groups around the world. One of the most important outcome measures in evaluation of its success is the histological quality of cartilaginous tissue. Currently, a variety of histological scoring systems is used to describe the quality of osteoarthritic, in vivo repaired or in vitro engineered tissue. This review aims to provide an overview of past and currently used histological scoring systems, in an effort to aid cartilage researchers in choosing adequate and validated cartilage histological scoring systems.

METHODS

Histological scoring systems for analysis of osteoarthritic, tissue engineered and in vivo repaired cartilage were reviewed. The chronological development as well as the validity and practical applicability of the scoring systems is evaluated.

RESULTS

The Histological-Histochemical Grading System (HHGS) or a HHGS-related score is most often used for evaluation of osteoarthritic cartilage, however the Osteoarthritis Research Society International (OARSI) Osteoarthritis Cartilage Histopathology Assessment System seems a valid alternative. The O'Driscoll score and the International Cartilage Repair Society (ICRS) II score may be used for in vivo repaired cartilage. The 'Bern score' seems most adequate for evaluation of in vitro engineered cartilage.

CONCLUSION

A great variety of histological scoring systems exists for analysis of osteoarthritic or normal, in vivo repaired or tissue-engineered cartilage, but only few have been validated. Use of these validated scores may considerably improve exchange of information necessary for advances in the field of cartilage regeneration.

Recent advances in MRI of articular cartilage

OBJECTIVE

MRI is the most accurate noninvasive method available to diagnose disorders of articular cartilage. Conventional 2D and 3D approaches show changes in cartilage morphology. Faster 3D imaging methods with isotropic resolution can be reformatted into arbitrary planes for improved detection and visualization of pathology. Unique contrast mechanisms allow us to probe cartilage physiology and detect changes in cartilage macromolecules.

CONCLUSION

MRI has great promise as a noninvasive comprehensive tool for cartilage evaluation.

Do NSAIDs affect longitudinal changes in knee cartilage volume and knee cartilage defects in older adults?

BACKGROUND

The effects of nonsteroidal anti-inflammatory drugs (NSAIDs) on knee osteoarthritis progression are unclear. The aim of this longitudinal study was to determine the associations between use of NSAIDs and changes in knee cartilage volume and knee cartilage defects over 2.9 years in older adults.

METHODS

T(1)-weighted fat-suppressed magnetic resonance imaging on the right knee was performed in a total of 395 randomly selected subjects (mean age 62 years, range 51-80 years, and 50% female) to assess knee cartilage volume at tibial sites and knee cartilage defects (0-4 scale) at baseline and 2.9 years later. Medication use in the last month was recorded by questionnaire.

RESULTS

Compared with nonusers of NSAIDs (n = 334), users of cyclooxygenase (COX)-2 inhibitors (n = 40) had decreased knee cartilage defect development in the medial tibiofemoral compartment (odds ratio [OR] 0.4, 95% confidence interval [CI], 0.2-0.99), whereas users of conventional NSAIDs (n = 21) had increased knee cartilage defect development in both medial (OR 3.1, 95% CI, 1.0-9.1) and lateral (OR 2.6, 95% CI, 1.0-6.7) tibiofemoral compartments. Comparing users of COX-2 inhibitors with users of conventional NSAIDs, the latter had higher knee cartilage volume loss (-5.3% vs -3.1% at medial tibia and -3.6% vs -1.1% at lateral tibia; all P <.05). All associations were adjusted for potential confounders including knee pain and radiographic osteoarthritis.

CONCLUSIONS

This study suggests that nonselective NSAIDs may have deleterious effects, while selective COX-2 inhibitors might have beneficial effects on knee cartilage. Randomized controlled trials examining knee structure to confirm this finding are warranted.

Imaging of knee osteoarthritis

New imaging modalities are broadening the possibilities in osteoarthritis (OA) research, and are offering new insights to help better understand the pathogenesis of this disease. Although knee radiographs are widely employed in epidemiological and clinical studies to assess structural pathology, joint radiographs provide limited outcome measures in knee OA, and other more valid, reliable and sensitive imaging modalities are now available. In particular, magnetic resonance imaging can directly visualize articular cartilage and other joint structures, such as bone and soft tissue, that are now recognized as part of the disease process. This chapter will examine imaging modalities in the assessment of knee OA, and the impact of these on our understanding of the pathogenesis of this disease.

Vastus medialis cross-sectional area is associated with patella cartilage defects and bone volume in healthy women

OBJECTIVES

Although vastus medialis and vastus lateralis are important muscular determinants of patellofemoral joint function, it is unclear how these muscles relate to the structure of the patellofemoral joint. The aim of this cross-sectional study was to determine the relationship between the vasti muscles and patella cartilage volume and defects and patella bone volume.

METHODS

One hundred and seventy-five women, aged 40-67 years, with no knee pain or clinical lower-limb disease had magnetic resonance imaging (MRI) of their dominant knee. The cross-sectional areas of the distal vastus medialis and lateralis were measured 37.5mm superior to the quadriceps tendon insertion at the proximal pole of the patella. Patella cartilage volume and defects and patella bone volume were measured from these images using validated methods.

RESULTS

There was no significant association between the distal vastus medialis cross-sectional area and patella cartilage volume. For every 1mm(2) increase in the distal vastus medialis cross-sectional area, there was an associated increased risk of patella cartilage defects [odds ratio (OR): 1.2; 95% confidence interval (CI) 1.004, 1.5; P=0.05], and an associated increase in patella bone volume (OR: 3.9; 95% CI 2.0, 5.8; P<0.001) after adjustment for potential confounders. There was no significant relationship between vastus lateralis cross-sectional area and measures of patella cartilage or bone.

CONCLUSION

An increased cross-sectional area of the distal portion of the vastus medialis muscle is associated with an increased risk of patella cartilage defects, and an increase in patella bone volume among healthy women. Although these results need to be confirmed in longitudinal studies, they suggest that an increase in the distal vastus medialis cross-sectional area is associated with structural change at the patellofemoral joint.

X-ray dark field imaging of human articular cartilage: possible clinical application to orthopedic surgery

Despite its convenience and non-invasiveness on daily clinical use, standard X-ray radiography cannot show articular cartilage. We developed a novel type of X-ray dark field imaging (DFI), which forms images only by a refracted beam with very low background illumination. We examined a disarticulated distal femur and a shoulder joint with surrounding soft tissue and skin, both excised from a human cadaver at the BL20B2 synchrotron beamline at SPring-8. The field was 90 mm wide and 90 mm high. Articular cartilage of the disarticulated distal femur was obvious on DFI, but not on standard X-ray images. Furthermore, DFI allowed visualization in situ of articular cartilage of the shoulder while covered with soft tissue and skin. The gross appearance of the articular cartilage on the dissected section of the proximal humerus was identical to the cartilage shown on the DFI image. These results suggested that DFI could provide a clinically accurate method of assessing articular cartilage. Hence, DFI would be a useful imaging tool for diagnosing joint disease such as osteoarthritis.

Diagnostic performance of in vivo 3-T MRI for articular cartilage abnormalities in human osteoarthritic knees using histology as standard of reference

The purpose of this study was (1) to evaluate the sensitivity, specificity and accuracy of sagittal in vivo 3-T intermediate-weighted fast spin-echo (iwFSE) sequences in the assessment of knee cartilage pathologies using histology as the reference standard in patients undergoing total knee replacement, and (2) to correlate MR imaging findings typically associated with osteoarthritis such as bone marrow edema pattern (BMEP) and cartilage swelling with histological findings. Tibial plateaus and femoral condyles of eight knees of seven patients were resected during surgery, and sagittal histological sections were prepared for histology. Preoperative MRI findings were compared to the corresponding region in histological sections for thickness, surface integrity and signal pattern of cartilage, and histological findings in areas of BMEP and swelling were documented. The overall sensitivity, specificity and accuracy were 72%, 69% and 70% for thickness, 69%, 74% and 73% for surface and 36%, 62% and 45% for intracartilaginous signal pattern. For all cases of BMEP on MRI subchondral ingrowth of fibrovascular tissue and increased bone remodeling were observed. MRI using fat-saturated iwFSE sequences showed good performance in assessing cartilage thickness and surface lesions, while signal changes of cartilage were not suited to characterize the severity of cartilage degeneration as validated by histology.

The natural history of cartilage defects in people with knee osteoarthritis

OBJECTIVES

Cartilage defects are highly prevalent in subjects with knee osteoarthritis (OA). Although they are associated with increased cartilage loss and joint replacement, there is little data on the natural history of cartilage defects. The aim of this study was to examine the progression of cartilage defects over 2 years in people with knee OA and to identify factors associated with progression.

METHODS

One hundred and seventeen subjects with OA underwent magnetic resonance imaging of their dominant knee at baseline and follow-up. Cartilage defects were scored (0-4) at four sites. Bone size of the medial and lateral tibial plateau was determined. Height, weight, body mass index and physical activity were measured by standard protocols.

RESULTS

The mean cartilage defect score increased significantly over the 2-year study period in all tibiofemoral compartments (all P<0.001), except the lateral tibial compartment with age and tibial plateau bone area at baseline being predictors of progression. However, there was heterogeneity with 81% progressing at any site, 15% remaining stable and 4% decreasing.

CONCLUSION

Over 2 years, cartilage defects tend to progress in people with symptomatic OA, with only a small percentage decreasing in severity. Increasing age and increased bone area are risk factors for progression. Interventions aimed at preventing cartilage defects from occurring and reducing their severity may result in a reduction in the severity of OA, by reducing loss of articular cartilage and subsequent requirement for knee joint replacement.

Tibial subchondral bone size and knee cartilage defects: relevance to knee osteoarthritis

Unlike knee plain radiography which can only detect joint space narrowing and osteophytes, magnetic resonance imaging can directly visualize and analyse the whole knee structure, including bone size, cartilage defects and loss of cartilage volume. Tibial subchondral bone area expansion may be primary and is associated with risk factors such as age, body mass index (BMI), genetics and/or limb malalignment. It can lead to the development of knee defects, which may also be caused by demographic, anthropometric and environmental factors such as age, female sex, BMI and smoking as well as structural changes such as osteophytes, bone marrow lesions, meniscal tears, meniscal extrusion and ligament abnormalities. Once knee cartilage defects develop, they have a variable natural history but are associated with subsequent cartilage loss in a dose-response manner. Both tibial subchondral bone area and knee cartilage defects are quantitatively related to the severity of knee osteoarthritis (OA), and predictive of the need for knee joint replacement in subjects with knee OA independent of radiographic change. Taken as a whole, these studies suggest that tibial subchondral bone expansion and cartilage defect development represent important targets for the prevention of cartilage loss and joint replacement.

Quantitative MRI of cartilage and bone: degenerative changes in osteoarthritis

Magnetic resonance imaging (MRI) and quantitative image analysis technology has recently started to generate a great wealth of quantitative information on articular cartilage and bone physiology, pathophysiology and degenerative changes in osteoarthritis. This paper reviews semiquantitative scoring of changes of articular tissues (e.g. WORMS = whole-organ MRI scoring or KOSS = knee osteoarthritis scoring system), quantification of cartilage morphology (e.g. volume and thickness), quantitative measurements of cartilage composition (e.g. T2, T1rho, T1Gd = dGEMRIC index) and quantitative measurement of bone structure (e.g. app. BV/TV, app. TbTh, app. Tb.N, app. Tb.Sp) in osteoarthritis. For each of these fields we describe the hardware and MRI sequences available, the image analysis systems and techniques used to derive semiquantitative and quantitative parameters, the technical accuracy and precision of the measurements reported to date and current results from cross-sectional and longitudinal studies in osteoarthritis. Moreover, the paper summarizes studies that have compared MRI-based measurements with radiography and discusses future perspectives of quantitative MRI in osteoarthritis. In summary, the above methodologies show great promise for elucidating the pathophysiology of various tissues and identifying risk factors of osteoarthritis, for developing structure modifying drugs (DMOADs) and for combating osteoarthritis with new and better therapy.

Preliminary study on diffraction enhanced radiographic imaging for a canine model of cartilage damage

OBJECTIVE

To demonstrate the ability of a novel radiographic technique, Diffraction Enhanced Radiographic Imaging (DEI), to render high contrast images of canine knee joints for identification of cartilage lesions in situ.

METHODS

DEI was carried out at the X-15A beamline at Brookhaven National Laboratory on intact canine knee joints with varying levels of cartilage damage. Two independent observers graded the DE images for lesions and these grades were correlated to the gross morphological grade.

RESULTS

The correlation of gross visual grades with DEI grades for the 18 canine knee joints as determined by observer 1 (r2 = 0.8856, P = 0.001) and observer 2 (r2 = 0.8818, P = 0.001) was high. The overall weighted kappa value for inter-observer agreement was 0.93, thus considered high agreement.

CONCLUSION

The present study is the first study for the efficacy of DEI for cartilage lesions in an animal joint, from very early signs through erosion down to subchondral bone, representing the spectrum of cartilage changes occurring in human osteoarthritis (OA). Here we show that DEI allows the visualization of cartilage lesions in intact canine knee joints with good accuracy. Hence, DEI may be applicable for following joint degeneration in animal models of OA.

The effects of exercise on human articular cartilage

The effects of exercise on articular hyaline articular cartilage have traditionally been examined in animal models, but until recently little information has been available on human cartilage. Magnetic resonance imaging now permits cartilage morphology and composition to be analysed quantitatively in vivo. This review briefly describes the methodological background of quantitative cartilage imaging and summarizes work on short-term (deformational behaviour) and long-term (functional adaptation) effects of exercise on human articular cartilage. Current findings suggest that human cartilage deforms very little in vivo during physiological activities and recovers from deformation within 90 min after loading. Whereas cartilage deformation appears to become less with increasing age, sex and physical training status do not seem to affect in vivo deformational behaviour. There is now good evidence that cartilage undergoes some type of atrophy (thinning) under reduced loading conditions, such as with postoperative immobilization and paraplegia. However, increased loading (as encountered by elite athletes) does not appear to be associated with increased average cartilage thickness. Findings in twins, however, suggest a strong genetic contribution to cartilage morphology. Potential reasons for the inability of cartilage to adapt to mechanical stimuli include a lack of evolutionary pressure and a decoupling of mechanical competence and tissue mass.

Magnetic resonance imaging (MRI) of articular cartilage in knee osteoarthritis (OA): morphological assessment

OBJECTIVE

Magnetic resonance imaging (MRI) is a three-dimensional imaging technique with unparalleled ability to evaluate articular cartilage. This report reviews the current status of morphological assessment of cartilage with quantitative MRI (qMRI), and its relevance for identifying disease status, and monitoring progression and treatment response in knee osteoarthritis (OA).

METHOD

An international panel of experts in MRI of knee OA, with direct experience in the analysis of cartilage morphology with qMRI, reviewed the existing published and unpublished data on the subject, and debated the findings at the OMERACT-OARSI Workshop on Imaging technologies (December 2002, Bethesda, MA) with scientists and clinicians from academia, the pharmaceutical industry and the regulatory agencies. This report reviews (1) MRI pulse sequence considerations for morphological analysis of articular cartilage; (2) techniques for segmenting cartilage; (3) semi-quantitative scoring of cartilage status; and (4) technical validity (accuracy), precision (reproducibility) and sensitivity to change of quantitative measures of cartilage morphology.

RESULTS

Semi-quantitative scores of cartilage status have been shown to display adequate reliability, specificity and sensitivity, and to detect lesion progression at reasonable observation periods (1-2 years). Quantitative assessment of cartilage morphology (qMRI), with fat-suppressed gradient echo sequences, and appropriate image analysis techniques, displays high accuracy and adequate precision (e.g., root-mean-square standard deviation medial tibia=61 microl) for cross-sectional and longitudinal studies in OA patients. Longitudinal studies suggest that changes of cartilage volume of the order of -4% to -6% occur per annum in OA in most knee compartments (e.g., -90 microl in medial tibia). Annual changes in cartilage volume exceed the precision errors and appear to be associated with clinical symptoms as well as with time to knee arthroplasty.

CONCLUSIONS

MRI provides reliable and quantitative data on cartilage status throughout most compartments of the knee, with robust acquisition protocols for multi-center trials now being available. MRI of cartilage has tremendous potential for large scale epidemiological studies of OA progression, and for clinical trials of treatment response to structure modifying OA drugs.

3.0 vs 1.5 T MRI in the detection of focal cartilage pathology--ROC analysis in an experimental model

OBJECTIVE

To use receiver operator characteristics (ROC) analysis for assessing the diagnostic performance of three cartilage-specific MR sequences at 1.5 and 3 T in detecting cartilage lesions created in porcine knees.

DESIGN

Eighty-four cartilage lesions were created in 27 porcine knee specimens at the patella, the medial and lateral femoral and the medial and lateral tibial cartilage. MR imaging was performed using a fat saturated spoiled gradient echo (SPGR) sequence (in plane spatial resolution/slice thickness: 0.20 x 0.39 mm2/1.5 mm) and two fat saturated proton density weighted (PDw) sequences (low spatial resolution: 0.31 x 0.47 mm2/3 mm and high spatial resolution: 0.20 x 0.26 mm2/2 mm). The images were independently analyzed by three radiologists concerning the absence or presence of lesions using a five-level confidence scale. Significances of the differences for the individual sequences were calculated based on comparisons of areas under ROC curves (A(Z)).

RESULTS

The highest A(Z)-values for all three radiologists were consistently obtained for the SPGR (A(Z) = 0.84) and the high-resolution (hr) PDw (A(Z) = 0.79) sequences at 3T. The corresponding A(Z)-values at 1.5 T were 0.77 and 0.69; the differences between 1.5 and 3 T were statistically significant (P < 0.05). A(Z)-values for the low-resolution PDw sequence were lower: 0.59 at 3 T and 0.55 at 1.5 T and the differences between 1.5 and 3T were not significant.

CONCLUSION

With optimized hr MR sequences diagnostic performance in detecting cartilage lesions was improved at 3 T. For a standard, lower spatial resolution PDw sequence no significant differences, however, were found.

Computer-aided quantification of focal cartilage lesions using MRI: accuracy and initial arthroscopic comparison

OBJECTIVE

The purpose of the study was to validate a Gradient Peak Method (GPM) by evaluating its accuracy and consistency at different magnetic field strengths. The GPM using magnetic resonance imaging (MRI) was previously proposed to quantitatively assess the morphology of focal cartilage lesions, and its feasibility was demonstrated.

METHODS

GPM quantifies the morphologic properties of cartilage lesions based on their three-dimensional geometry. Twenty-two conical and cylindrical lesions were surgically created on fresh porcine knees, and the results obtained by GPM were compared with manually measured lesion dimensions. Another 15 focal lesions of various shapes were created and scanned, and the quantification results were compared at 1.5 Tesla and 3 Tesla. Additionally, cartilage lesions in three patients were scanned, quantified by GPM, and compared with arthroscopic visualization and measurements.

RESULTS

The average absolute errors of GPM (depth: < or =0.4mm; diameter: < or =1.4mm) were within twice the in-plane resolution in depth estimates and within the slice thickness in diameter estimates. Analysis also suggested that the quantifications of GPM using 1.5 Tesla and 3 Tesla data were not statistically different. Moreover, the GPM results were shown to be consistent with the lesion measurements obtained arthroscopically.

CONCLUSIONS

The GPM using MRI provides estimates of lesion thickness, depth, diameter, and area. With this validation, the method can be potentially used as an auxiliary tool to help radiologists and physicians assess cartilage lesions quantitatively and monitor disease progression.