Magnetic resonance imaging of articular cartilage

MRI evaluation of meniscal anatomy: which parameters reach the best inter-observer concordance?

Purpose

The aim of the study is to evaluate which MRI parameters achieve the best degree of inter-individual concordance in the description of meniscal fibrocartilage, regarding its morphology, signal and position.

Materials and methods

Eighty-nine knee MRIs were included in the study, retrospectively re-evaluated by three radiologists who completed a binary report (normal/abnormal) describing the meniscus signal, position relative to the tibial plateau margin and morphology. The inter-individual concordance value was calculated using Cohen's test.

Results

We obtained different inter-individual concordance values according to the parameters considered. The concordance was poor in the description of the meniscal position relative to the tibial plateau margin (average k = 0.6); the result was comparable in the description of the meniscal morphology (average k = 0.56). The best results were obtained with the meniscal signal analysis (average k = 0.8).

Conclusion

To the best of our knowledge, there are no studies in the literature assessing the concordance between multiple readers in the description of the parameters we studied. The results we obtained suggest that the most reliable parameter for describing meniscal fibrocartilage is its signal intensity, whereas morphology and position may lead to different interpretations that are not always unequivocal.

Correlation of the Histological ICRS II Score and the 3D MOCART Score for the Analysis of Aged Osteochondral Regenerates in a Large Animal Model

OBJECTIVE

Reliable outcome measures are essential to predict the success of cartilage repair techniques. Histology is probably the gold standard, but magnetic resonance imaging (MRI) has the potential to decrease the need for invasive histological biopsies. The 3D magnetic resonance observation of cartilage repair tissue (MOCART) score is a reliable yet elaborate tool. Moreover, literature is controversial concerning the correlation of histology and MRI.

DESIGN

To test the applicability of the International Cartilage Regeneration and Joint Preservation Society (ICRS) II and MOCART 3D score for the evaluation of aged osteochondral regenerates in a large animal model, and to identify correlating histological and MRI parameters. Osteochondral defects in medial femoral condyles of n = 12 adult sheep were reconstructed with biodegradable bilayer implants. About 19.5 months postoperation, n = 10 joints were analyzed with MRI (3D MOCART score). Histological samples were analyzed using the ICRS II score; both pre- and post-training. The intraclass correlation coefficient, the inter-rater reliability, and the 95% confidence interval were calculated. Matching histological and MRI parameters were tested for correlation.

RESULTS

We found a statistically significant correlation of all histological parameters. MRI parameters reflecting "overall" assessments had very strong inter-rater correlations. Statistically significant strong correlations were found for the MRI parameters defect filling, cartilage interface, bone interface, and surface. For defect overall (MRI) and overall assessment (ICRS II), we found a significant yet mild correlation.

CONCLUSIONS

The ICRS II and the 3D MOCART score are applicable to aged osteochondral regenerates. Prior training on the scoring systems is essential. Select MRI and histological parameters correlate; however, the only statistically significant correlation was found for overall assessment.

High-Frequency Acoustic Imaging Using Adhesive-Free Polymer Transducer

The piezoelectric polymer PVDF and its copolymers have a long history as transducer materials for medical and biological applications. An efficient use of these polymers can potentially both lower the production cost and offer an environment-friendly alternative for medical transducers which today is dominated by piezoelectric ceramics containing lead. The main goal of the current work has been to compare the image quality of a low-cost in-house transducers made from the copolymer P(VDF-TrFE) to a commercial PVDF transducer. Several test objects were explored with the transducers used in a scanning acoustic microscope, including a human articular cartilage sample, a coin surface, and an etched metal film with fine line structures. To evaluate the image quality, C- and B-scan images were obtained from the recorded time series, and compared in terms of resolution, SNR, point-spread function, and depth imaging capability. The investigation is believed to provide useful information about both the strengths and limitations of low-cost polymer transducers.

Poor Sensitivity of Magnetic Resonance Arthrography to Detect Hip Chondral Delamination: A Retrospective Follow-Up of 227 FAI-Operated Patients

OBJECTIVE

The purpose of this study was to retrospectively assess the frequency and characteristics of acetabular cartilage delamination (CD) in femoroacetabular impingement (FAI) patients and to assess the sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of magnetic resonance arthrography (MRA) in detecting CD based on the radiologist report.

DESIGN

This is a single-center retrospective review of consecutive patients operated for symptomatic FAI. All of the patients had a 1.5-T MR-arthrogram within 12 months preoperatively. MRA reports of these patients were compared with operation notes and surgical videos of all patients by two trained assessors.

RESULTS

At surgery, CD of the acetabulum was present in 169 patients out of a total of 229 patients (74%). Only 6.5% (11 patients) of CD was described on the MRA reports preoperatively. The mean age of the patients was 37.6 ± 13.3 years. The average extent of delamination was 3.12 ± 1.5 cm² with a mean coronal × sagittal extent of 0.68 × 4.33 cm. There was a significant difference regarding age (P = 0.002), alpha angle from frog view (P = 0.002), and alpha angle from anteroposterior view (P = 0.012) between the patients with delamination and without delamination. The majority of labral tears and cartilage damage were located in the anterosuperior quadrant. MRA sensitivity was 6%, specificity 98%, NPV 27%, and PPV 91% based on the radiologist report.

CONCLUSION

The CD in patients with FAI can be severely underdiagnosed with MRA. There is a need for better standard diagnostic criteria to detect CD in patients with FAI.

Analyzing Femorotibial Cartilage Thickness Using Anatomically Standardized Maps: Reproducibility and Reference Data

Alterations in cartilage thickness (CTh) are a hallmark of knee osteoarthritis, which remain difficult to characterize at high resolution, even with modern magnetic resonance imaging (MRI), due to a paucity of standardization tools. This study aimed to assess a computational anatomy method producing standardized two-dimensional femorotibial CTh maps. The method was assessed with twenty knees, processed following three common experimental scenarios. Cartilage thickness maps were obtained for the femorotibial cartilages by reconstructing bone and cartilage mesh models in tree-dimension, calculating three-dimensional CTh maps, and anatomically standardizing the maps. The intra-operator accuracy (median (interquartile range, IQR) of -0.006 (0.045) mm), precision (0.152 (0.070) mm), entropy (7.02 (0.71) and agreement (0.975 (0.020))) results suggested that the method is adequate to capture the spatial variations in CTh and compare knees at varying osteoarthritis stages. The lower inter-operator precision (0.496 (0.132) mm) and agreement (0.808 (0.108)) indicate a possible loss of sensitivity to detect differences in a setting with multiple operators. The results confirmed the promising potential of anatomically standardized maps, with the lower inter-operator reproducibility stressing the need to coordinate operators. This study also provided essential reference data and indications for future research using CTh maps.

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.

Evaluation of Cartilage in the Wrist using Magnetic Resonance Imaging

Wrist pain is a common patient complaint with a myriad of clinical conditions that can explain the underlying cause. Short of wrist arthroscopy, no technique other than formal wrist arthrotomy exists for direct examination of the hyaline cartilage coating the articular surfaces of the carpal bones. Magnetic resonance imaging (MRI) has been proven accurate in evaluating joint surfaces of large joints such as the shoulder, hip, and knee with articular cartilage surface thickness is in excess of 1 mm. However, in the carpus the thickness of the cartilage and the contours present have precluded accurate imaging. Advances in MRI technology over the last several decades are now making imaging of small joint surfaces, such as the carpus, an area worth revisiting. Herein we provide a review of these efforts with a specific focus on the evaluation of the wrist.

Quantitative susceptibility mapping of articular cartilage in patients with osteoarthritis at 3T

BACKGROUND

Quantitative susceptibility mapping (QSM) has recently been applied in humans to quantify the magnetic susceptibility of collagen fibrils in the articular cartilage.

PURPOSE

To determine the ability of QSM to detect cartilage matrix degeneration between normal and early knee osteoarthritis (OA) patients.

STUDY TYPE

Prospective.

POPULATION

Twenty-four patients with knee OA and 24 age- and sex-matched healthy controls.

FIELD STRENGTH/SEQUENCE

3D gradient echo, T₁ turbo spin echo, and proton density-weighted (PDw) spectral attenuated inversion recovery (SPAIR) sequence at 3.0T.

ASSESSMENT

Scan-rescan reproducibility of the susceptibility values in the cartilage was assessed in control subjects. Cartilage thickness, volume, mean, and standard deviation (SD) of susceptibility values of the cartilage compartments were compared between normal and OA patients. The relationship between magnetic susceptibility values and cartilage lesion grading based on MR images was studied.

STATISTICAL TESTS

The Wilcoxon Rank-Sum test was used to compare cartilage thickness, volume, mean, and SD of susceptibility values between control subjects and OA patients. A Spearman rank correlation was performed to study the relationship between the mean and SD of susceptibility values and the cartilage thinning grades.

RESULTS

The SD of magnetic susceptibility values in the knee cartilage was significantly lower in OA patients compared with healthy controls, and it decreased with more severe MR grades of cartilage thinning degeneration. Significant correlations between the SD of susceptibility values and cartilage thinning grades were observed with R²  = 0.64 and P = 0.000, R²  = 0.47 and P = 0.002, R²  = 0.52 and P = 0.001, R²  = 0.42 and P = 0.0006, and R²  = 0.67 and P = 0.000 for medial femoral condyle (MFC), lateral femoral condyle (LFC), medial tibia (MT), lateral tibia (LT), and patella, respectively. No significant difference was found in cartilage volume (P = 0.17, P = 0.13, P = 0.20, P = 0.25, and P = 0.18 for MFC, LFC, MT, LT, and patella, respectively) and thickness (P = 0.31, P = 0.19, P = 0.16, P = 0.09, and P = 0.22 for MFC, LFC, MT, LT, and patella, respectively) between OA patients and healthy controls.

DATA CONCLUSION

The variations of susceptibility values in the knee cartilage decrease with the degree of cartilage degeneration. QSM may be a sensitive indicator for alteration of the collagen network and shows potential to detect cartilage degeneration at early stage.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018.

Subchondral Bone and the Osteochondral Unit: Basic Science and Clinical Implications in Sports Medicine

Context:

Articular cartilage injuries and early osteoarthritis are among the most common conditions seen by sports medicine physicians. Nonetheless, treatment options for articular degeneration are limited once the osteoarthritic cascade has started. Intense research is focused on the use of biologics, cartilage regeneration, and transplantation to help maintain and improve cartilage health. An underappreciated component of joint health is the subchondral bone.

Evidence Acquisition:

A comprehensive, nonsystematic review of the published literature was completed via a PubMed/MEDLINE search of the keywords “subchondral” AND “bone” from database inception through December 1, 2016.

Study Design:

Clinical review.

Level of Evidence:

Level 4.

Methods:

Articles collected via the database search were assessed for the association of bone marrow lesions and osteoarthritis, cartilage regeneration, and ligamentous and meniscal injury; the clinical disorder known as painful bone marrow edema syndrome; and the subchondral bone as a target for medical and surgical intervention.

Results:

A complex interplay exists between the articular cartilage of the knee and its underlying subchondral bone. The role of subchondral bone in the knee is intimately related to the outcomes from cartilage restoration procedures, ligamentous injury, meniscal pathology, and osteoarthritis. However, subchondral bone is often neglected when it should be viewed as a critical element of the osteochondral unit and a key player in joint health.

Conclusion:

Continued explorations into the intricacies of subchondral bone marrow abnormalities and implications for the advent of procedures such as subchondroplasty will inform further research efforts on how interventions aimed at the subchondral bone may provide durable options for knee joint preservation.

Effectiveness of an Ayurveda treatment approach in knee osteoarthritis - a randomized controlled trial

OBJECTIVE

Ayurveda is commonly used in South Asia to treat knee osteoarthritis (OA). We aimed to evaluate the effectiveness of Ayurvedic treatment compared to conventional conservative care in patients with knee OA.

METHOD

According to American College of Rheumatology (ACR) criteria knee OA patients were included in a multicenter randomized, controlled, open-label trial and treated in 2 hospital clinics and 2 private outpatient clinics in Germany. Participants received either a multi-modal Ayurvedic treatment or multi-modal conventional care with 15 treatments over 12 weeks respectively. Primary outcome was the change on the Western Ontario and McMaster University Osteoarthritis (WOMAC) Index after 12 weeks. Secondary outcomes included WOMAC subscales; the pain disability index and a pain experience scale, numeric rating scales for pain and sleep quality, quality-of-life and mood, rescue medication use, and safety issues.

RESULTS

One hundred fifty-one participants (Ayurveda n = 77, conventional care n = 74) were included. Changes of the WOMAC Index from baseline to 12 weeks were more pronounced in the Ayurveda group (mean difference 61.0 [95%CI: 52.4;69.6]) than in the conventional group (32.0 [95%CI: 21.4;42.6]) resulting in a significant between-group difference (p < 0.001) and a clinically relevant effect size (Cohen's d 0.68 [95% CI:0.35;1.01]). Similar trends were observed for all secondary outcomes at week 12. Effects were sustained at follow-ups after 6 and 12 months.

CONCLUSION

Results suggest that Ayurvedic treatment is beneficial in reducing knee OA symptoms. Further studies should be conducted to confirm the magnitude of the effect and to clarify the role of different treatment components and non-specific effects. REGISTRATION: at clinicaltrials.gov (NCT01225133; initial release 10/06/2010).

Treatment of a Focal Articular Cartilage Defect of the Talus with Polymer-Based Autologous Chondrocyte Implantation: A 12-Year Follow-Up Period

Autologous chondrocyte implantation (ACI) is a first-line treatment option for large articular cartilage defects. Although well-established for cartilage defects in the knee, studies of the long-term outcomes of matrix-assisted ACI to treat cartilage defects in the ankle are rare. In the present report, we describe for the first time the long-term clinical and radiologic results 12 years after polymer-based matrix-assisted ACI treat a full-thickness talar cartilage defect in a 25-year-old male patient. The clinical outcome was assessed using the visual analog scale and Freiburg ankle score, magnetic resonance imaging evaluation using the Henderson-Kreuz scoring system and T2 mapping. Clinical assessment revealed improved visual analog scale and Freiburg ankle scores. The radiologic analysis and T2 relaxation time values indicated the formation of hyaline-like repair tissue. Polymer-based autologous chondrocytes has been shown to be a safe and clinically effective long-term treatment of articular cartilage defects in the talus.

MR imaging of BioCartilage augmented microfracture surgery utilizing 2D MOCART and KOOS scores

OBJECTIVES

BioCartilage is a novel scaffold-based microfracture augmentation technique that has been shown to aid in chondrogenic differentiation of adult progenitor cells resulting in formation of more hyaline-like cartilage. As this cartilage repair technique becomes more commonplace, it is essential that the musculoskeletal radiologist and orthopedic surgeon gain familiarity with the surgical technique and its post-operative MR imaging findings.

METHODS

We present several case studies regarding MRI findings (modified clinical 2D MOCART) and clinical outcome (KOOS) scores in patients who have undergone this novel surgical procedure. For data analysis KOOS scores where dichotomized to scores greater or less than 80, and MOCART scores were dichotomized to scores greater or less than 50. A fisher exact test was then performed to determine if there was any correlation between parameters of the modified 2D MOCART and KOOS scores (Tables 2 and 3).

RESULTS

Marrow elements travel through the microfracture holes and interact with the scaffold created by BioCartilage, rather than creating their own fibrin scaffold, as is typically anticipated from a marrow stimulation procedure. Interestingly, the amount defect fill, presence of an intact surface, intact subchondral bone, or lack of effusion did not correlate with positive outcomes. Parameters that trended towards significance included presence of adhesions and subchondral lamina. Completeness of cartilage interface, homogeneity, and signal intensity also failed to reach statistical significance. In our experience, patients that demonstrated mild repair tissue surface irregularity, but with preservation of greater than 50% thickness compared to surrounding native cartilage, mild irregularity of subchondral plate, with vertical low signal intensity lines (sequela of prior microfracture surgery), and mild or no bone marrow edema pattern demonstrated higher KOOS scores.

CONCLUSION

Biocartilage in conjunction with microfracture is an encouraging cartilage restoration technique that promotes regeneration of more robust hyaline-like cartilage compared to the fibrocartilage formed after conventional microfracture. The T2 mapping properties of the repair tissue after successful BioCartilage augmented microfracture surgery are very similar to that of the adjacent native cartilage. Although there appear to be characteristic trends in a successful repair, further research is warranted to elucidate any correlations between specific characteristics of the repair and patient clinical outcomes.

Association between MRI-detected osteophytes and changes in knee structures and pain in older adults: a cohort study

OBJECTIVE

To describe cross-sectional and longitudinal associations between magnetic resonance imaging (MRI)-detected osteophytes (OPs) and knee structural abnormalities and knee pain in older adults.

METHOD

A prospective population-based cohort study of 895 participants aged 50-80 years (mean age 62 years, 50% female) was performed. T1-or T2-weighted fat suppressed MRI was used to assess knee OPs, cartilage volume, cartilage defects and bone marrow lesions (BMLs) at baseline and after 2.6 years. Radiographically-detected OPs were scored according to the Osteoarthritis Research Society International (OARSI) atlas. Knee pain was assessed using a self-administered questionnaire at baseline, 2.6 and 5 years later.

RESULTS

85% of participants had MRI-detected OPs at baseline, while 10% of participants had radiographically-detected OPs. Cross-sectionally, higher gardes of MRI-detected OPs in all compartments were significantly, independently and site-specifically associated with higher prevalences of cartilage defects and BMLs, lower cartilage volume and higher prevalence of knee pain. Longitudinally, higher gardes of baseline MRI-detected OPs site-specifically predicted greater risks of any increase in cartilage defects or BMLs, and loss of cartilage volume in medial and lateral tibiofemoral (LTF) and total compartments over 2.6 years in multivariable analyses. These significant associations were similar in those without radiographically-detected OPs. MTF and total OP scores were significantly associated with change in total knee pain over 2.6 and 5 years but these became non-significant after adjustment for cartilage defects and BMLs.

CONCLUSION

MRI-detected knee OPs are common and appear to be clinically relevant to knee structural changes in older adults.

Identifying Hidden Zones of the Far Posterior Cartilage of the Femoral Condyles Not Visible During Knee Arthroscopy

OBJECTIVE

The purpose of this study was to compare standard knee arthroscopic and MRI findings and measurements for visualization of the femoral condyle articular cartilage. The hypothesis was that certain posterior cartilage defects identified with MRI may not be accessible with routine arthroscopy.

MATERIALS AND METHODS

Six cadaveric knees were examined by routine arthroscopy through standard inferomedial and inferolateral portals. Suture anchors were inserted into the femoral condyles at 30°, 60°, 90°, and 120° of flexion as markers of the cartilage surface at the most posterior aspect of the condyle that could be accessed at each degree of flexion. Each specimen was then examined with 3-T MRI and gross dissection. Measurements were obtained and compared.

RESULTS

During arthroscopy at 90° of knee flexion, only 5.83 mm of the medial femoral condyle and 6.83 mm of the lateral femoral condyle were visualized posterior to the anchor placed at 90° of flexion. These arthroscopic measurements were statistically significant underestimates of the actual amount of cartilage identified posterior to the 90° anchor at gross dissection (medial condyle, 44.20 mm; lateral condyle, 37.50 mm) and MRI (medial, 41.33 mm; lateral, 38.87 mm). This indicates that 85.9% of the medial and 81.8% of the lateral posterior articular cartilage of the femoral condyle seen at MRI were not visualized during arthroscopy.

CONCLUSION

More than 80% of the articular cartilage proximal to the menisci seen at MRI is not visible during routine arthroscopy. This far posterior articular cartilage should be called the hidden zone.

Magnetic Resonance Imaging of Articular Cartilage

The emergence of newer pharmacotherapeutic agents and surgical cartilage resurfacing techniques is driving the need for imaging modalities capable of early, accurate, and reproducible lesion detection. Magnetic resonance imaging (MRI) has emerged as a noninvasive tool for direct 2-dimensional (2D) and 3-dimensional (3D) assessment of the articular cartilage in both clinical and research settings. MRI has largely overcome the shortcomings of the current gold standard, radiography, by allowing for the detection of preclinical disease and subtle early abnormalities prior to the onset of radiographic disease, when damage is still reversible. Current MRI techniques are either morphological (2D/3D qualitative and quantitative techniques) or compositional (matrix-assessment techniques that detect macromolecular changes prior to morphological changes). MRI is evolving as a complete answer to our cartilage-imaging requirements of lesion description, treatment planning, and outcome measurement as well as in various research settings.

Diagnostic Efficacy of 3-T MRI for Knee Injuries Using Arthroscopy as a Reference Standard: A Meta-Analysis

OBJECTIVE

The objectives of our study were to assess the evidence for the diagnostic efficacy of 3-T MRI for meniscal and anterior cruciate ligament (ACL) injuries in the knee using arthroscopy as the reference standard and to compare these results with the results of a previous meta-analysis assessing 1.5-T MRI.

MATERIALS AND METHODS

The online Cochrane Library, MEDLINE, and PubMed databases were searched using the following terms: MRI AND ((3 OR three) AND (Tesla OR T)) AND knee AND arthroscopy AND (menisc* OR ligament). Patient demographics, patient characteristics, MRI scanning details, and diagnostic results were investigated. The methodologic quality of the included studies was assessed using the revised Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. A meta-analysis of studies using 3-T MRI was performed, and the results were compared with a previous meta-analysis of studies using 1.5-T MRI.

RESULTS

One hundred one studies were identified by the search strategy, and 13 studies were included in our review. Twelve studies were considered to have level 1b evidence, and one study was considered to have level 2b evidence. All 13 studies had high methodologic integrity and low risk of bias using the QUADAS-2 tool. The studies included 1197 patients with a mean age of 41.9 years. Ten of the 13 studies were eligible for meta-analysis. The mean sensitivity and mean specificity of 3-T MRI for knee injuries by location were as follows: medial meniscus, 0.94 (95% CI, 0.91-0.96) and 0.79 (95% CI, 0.75-0.83), respectively; lateral meniscus, 0.81 (95% CI, 0.75-0.85) and 0.87 (95% CI, 0.84-0.89); and ACL, 0.92 (95% CI, 0.83-0.96) and 0.99 (95% CI, 0.96-1.00). The specificity of 3-T MRI for injuries of the lateral meniscus was significantly lower than that of 1.5-T MRI (p = 0.0013).

CONCLUSION

This study does not provide evidence that 3-T scanners have superior diagnostic efficacy for meniscal damage and ACL integrity when compared with previous studies of 1.5-T machines.

Quantitative assessment of morphology, T1ρ, and T2 of shoulder cartilage using MRI

OBJECTIVES

The aim of this study was to assess the feasibility of quantifying shoulder cartilage morphology and relaxometry in a clinically feasible scan time comparing different pulse sequences and assessing their reproducibility at 3 Tesla.

METHODS

Three pulse sequences were compared for morphological assessments of shoulder cartilage thickness and volume (SPGR, MERGE, FIESTA), while a combined T1ρ-T2 sequence was optimized for relaxometry measurements. The shoulders of six healthy subjects were scanned twice with repositioning, and the cartilage was segmented and quantified. The degree of agreement between the three morphological sequences was assessed using Bland-Altman plots, while the morphological and relaxometry reproducibility were assessed with root-mean-square coefficients of variation (RMS-CVs) RESULTS: Bland-Altman plots indicated good levels of agreement between the morphological assessments of the three sequences. The reproducibility of morphological assessments yielded RMS-CVs between 4.0 and 17.7 %. All sequences correlated highly (R > 0.9) for morphologic assessments with no statistically significant differences. For relaxometry assessments of humeral cartilage, RMS-CVs of 6.4 and 10.6 % were found for T1ρ and T2, respectively.

CONCLUSIONS

The assessment of both cartilage morphology and relaxometry is feasible in the shoulder with SPGR, humeral head, and T1ρ being the more reproducible morphological sequence, anatomic region, and quantitative sequence, respectively.

KEY POINTS

• The thin cartilage morphology can be assessed in the shoulder in vivo. • Non-invasive biochemical assessment of shoulder cartilage is feasible in vivo using MRI.

Congenital dislocation of the patella - clinical case

Congenital patellar dislocation is a rare condition in which the patella is permanently dislocated and cannot be reduced manually. The patella develops normally as a sesamoid bone of the femur. This congenital dislocation results from failure of the internal rotation of the myotome that forms the femur, quadriceps muscle and extensor apparatus. It usually manifests immediately after birth, although in some rare cases, the diagnosis may be delayed until adolescence or adulthood. Early diagnosis is important, thereby allowing surgical correction and avoiding late sequelae, including early degenerative changes in the knee. A case of permanent dislocation of the patella is presented here, in a female child aged seven years.

Animal models of osteoarthritis: classification, update, and measurement of outcomes

Osteoarthritis (OA) is one of the most commonly occurring forms of arthritis in the world today. It is a debilitating chronic illness causing pain and immense discomfort to the affected individual. Significant research is currently ongoing to understand its pathophysiology and develop successful treatment regimens based on this knowledge. Animal models have played a key role in achieving this goal. Animal models currently used to study osteoarthritis can be classified based on the etiology under investigation, primary osteoarthritis, and post-traumatic osteoarthritis, to better clarify the relationship between these models and the pathogenesis of the disease. Non-invasive animal models have shown significant promise in understanding early osteoarthritic changes. Imaging modalities play a pivotal role in understanding the pathogenesis of OA and the correlation with pain. These imaging studies would also allow in vivo surveillance of the disease as a function of time in the animal model. This review summarizes the current understanding of the disease pathogenesis, invasive and non-invasive animal models, imaging modalities, and pain assessment techniques in the animals.

MRI EVALUATION OF KNEE CARTILAGE

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

Osteochondral Allograft MRI Scoring System (OCAMRISS) in the Knee: Interobserver Agreement and Clinical Application

INTRODUCTION

Osteochondral allograft (OCA) transplantation is a suitable treatment option for large osteochondral defects. Magnetic resonance imaging (MRI) is an objective, reproducible, noninvasive monitoring tool for postoperative assessment after cartilage surgery.

OBJECTIVE

To correlate Osteochondral Allograft MRI Scoring System (OCAMRISS) in patients undergoing OCA transplantation in the knee with clinical outcomes and determine interobserver agreement of this scoring system.

METHODS

Fifteen patients underwent OCA transplantation in the knee and received a postoperative MRI. Four examiners read each MRI and completed an OCAMRISS. Interobserver agreement and intraclass correlation coefficients (ICCs) were assessed. Clinical outcomes were evaluated. Correlation between the OCAMRISS and clinical outcomes was calculated using Spearman's correlation coefficients.

RESULTS

Interobserver agreement on individual features of the OCAMRISS was superior (κ = 0.81-1.0) in 65% of comparisons, substantial (κ = 0.61-0.8) in 14%, moderate (κ = 0.41-0.6) in 18%, and fair (κ = 0.21-0.4) in 3%. Agreement among readers was very strong for the cartilage, bone, ancillary, and total scores with 96% of comparisons having an ICC >0.80. International Knee Documentation Committee (IKDC) function scores were correlated with OCAMRISS cartilage score (ρ = 0.53, P = 0.044) and total score (ρ = 0.67, P = 0.006). The Knee injury and Osteoarthritis Outcome Score (KOOS) sports/recreation subscale was correlated with OCAMRISS ancillary score (ρ = 0.58, P = 0.049) and total score (ρ = 0.64, P = 0.024). No correlation was observed with subchondral bone features of OCAMRISS and any of the outcome scores.

CONCLUSIONS

The recently described OCAMRISS is a reproducible grading system for in vivo evaluation after osteochondral allograft transplantation.

Imaging of articular cartilage: current concepts

Magnetic resonance imaging (MRI) is the gold standard method for non-invasive assessment of joint cartilage, providing information on the structure, morphology and molecular composition of this tissue. There are certain minimum requirements for a MRI study of cartilage tissue: machines with a high magnetic field (> 1.5 Tesla); the use of surface coils; and the use of T2-weighted, proton density-weighted fast-spin echo (T2 FSE-DP) and 3D fat-suppressed T1-weighted gradient echo (3D-FS T1W GRE) sequences. For better contrast between the different joint structures, MR arthography is a method that can highlight minimal fibrillation or fractures of the articular surface and allow evaluation of the integrity of the native cartilage-repair tissue interface. To assess the biochemical composition of cartilage and cartilage repair tissue, various techniques have been proposed for studying proteoglycans [dGEMRIC, T1rho mapping, sodium (23Na) imaging MRI, etc.], collagen, and water distribution [T2 mapping, "magnetisation transfer contrast", diffusion-weighted imaging (DWI), and so on]. Several MRI classifications have been proposed for evaluating the processes of joint degeneration (WORMS, BLOKS, ICRS) and post-surgical maturation of repair tissue (MOCART, 3D MOCART). In the future, isotropic 3D sequences set to improve image quality and facilitate the diagnosis of disorders of articular structures adjacent to cartilage.

Comparison of PD BLADE with fat saturation (FS), PD FS and T2 3D DESS with water excitation (WE) in detecting articular knee cartilage defects

The purpose of this study, is to compare the sequences: 1) proton density (PD) BLADE (BLADE is a PROPELLER-equivalent implementation of the Siemens Medical System) with fat saturation (FS) coronal (COR), 2) PD FS COR, 3) multi-planar reconstruction (MPR) with 3mm slice thickness and 4) multi-planar reconstruction (MPR) with 1.5mm slice thickness, both from the T2 3D-double-echo steady state (DESS) with water excitation (WE) sagittal (SAG), regarding their abilities to identify changes in the femorotibial condyle cartilage in knee MRI examinations. Thirty three consecutive patients with osteoarthritis (18 females, 15 males; mean age 56years, range 37-71years), who had been routinely scanned for knee examination using the previously mentioned image acquisition techniques, participated in the study. A quantitative analysis was performed based on the relative contrast (ReCON) measurements, which were taken both on normal tissues as well as on pathologies. Additionally, a qualitative analysis was performed by two radiologists. Motion and pulsatile flow artifacts were evaluated. The PD BLADE FS COR sequence produced images of higher contrast between Menisci and Cartilage, Fluid and Cartilage, Pathologies and Cartilage as well as of the Conspicuousness Superficial Cartilage and it was found to be superior to the other sequences (p<0.001). The sequences T2 3D DESS 1.5mm and T2 3D DESS 3mm were significantly superior to the PD BLADE FS COR and the PD FS COR sequences in the visualization of Bone and Cartilage and the Conspicuousness Deep Surface Cartilage. This pattern of results is also confirmed by the quantitative analysis. PD FS BLADE sequences are ideal for the depiction of the cartilage pathologies compared to the conventional PD FS and T2 3D DESS sequences.

Usefulness of IDEAL T2-weighted FSE and SPGR imaging in reducing metallic artifacts in the postoperative ankles with metallic hardware

PURPOSE

The aim of this work is to prospectively compare the effectiveness of iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL), T2-weighted fast spin-echo (FSE), and spoiled gradient-echo (SPGR) MR imaging to frequency selective fat suppression (FSFS) protocols for minimizing metallic artifacts in postoperative ankles with metallic hardware.

MATERIALS AND METHODS

The T2-weighted and SPGR imaging with IDEAL and FSFS were performed on 21 ankles of 21 patients with metallic hardware. Two musculoskeletal radiologists independently analyzed techniques for visualization of ankle ligaments and articular cartilage, uniformity of fat saturation, and relative size of the metallic artifacts. A paired t test was used for statistical comparisons of MR images between IDEAL and FSFS groups.

RESULTS

IDEAL T2-weighted FSE and SPGR images enabled significantly improved visualization of articular cartilage (p < 0.05), the size of metallic artifact (p < 0.05), and the uniformity of fat saturation (p < 0.05). However, no significant improvement was found in the visibility of ligaments.

CONCLUSIONS

IDEAL T2-weighted FSE and SPGR imaging effectively reduces the degree of tissue-obscuring artifacts produced by fixation hardware in ankle joints and improves image quality compared to FSFS T2-weighted FSE and SPGR imaging. However, visibility of ligaments was not improved using IDEAL imaging.

Accuracy of magnetic resonance imaging, magnetic resonance arthrography and computed tomography for the detection of chondral lesions of the knee

PURPOSE

To assess the diagnostic test accuracy of magnetic resonance imaging (MRI), magnetic resonance arthrography (MRA) and computed tomography arthrography (CTA) for the detection of chondral lesions of the patellofemoral and tibiofemoral joints.

METHODS

A review of published and unpublished literature sources was conducted on 22nd September 2011. All studies assessing the diagnostic test accuracy (sensitivity/specificity) of MRI or MRA or CTA for the assessment of adults with chondral (cartilage) lesions of the knee (tibiofemoral/patellofemoral joints) with surgical comparison (arthroscopic or open) as the reference test were included. Data were analysed through meta-analysis.

RESULTS

Twenty-seven studies assessing 2,592 knees from 2,509 patients were included. The findings indicated that whilst presenting a high specificity (0.95-0.99), the sensitivity of MRA, MRI and CTA ranged from 0.70 to 0.80. MRA was superior to MRI and CTA for the detection of patellofemoral joint chondral lesions and that higher field-strength MRI scanner and grade four lesions were more accurately detected compared with lower field-strength and grade one lesions. There appeared no substantial difference in diagnostic accuracy between the interpretation from musculoskeletal and general radiologists when undertaking an MRI review of tibiofemoral and patellofemoral chondral lesions.

CONCLUSIONS

Specialist radiological imaging is specific for cartilage disease in the knee but has poorer sensitivity to determine the therapeutic options in this population. Due to this limitation, there remains little indication to replace the 'gold-standard' arthroscopic investigation with MRI, MRA or CTA for the assessment of adults with chondral lesions of the knee.

LEVEL OF EVIDENCE

II.

Experimental scoring systems for macroscopic articular cartilage repair correlate with the MOCART score assessed by a high-field MRI at 9.4 T--comparative evaluation of five macroscopic scoring systems in a large animal cartilage defect model

OBJECTIVE

To develop a new macroscopic scoring system which allows for an overall judgment of experimental articular cartilage repair and compare it with four existing scoring systems and high-field magnetic resonance imaging (MRI).

METHODS

A new macroscopic scoring system was developed to assess the repair of cartilage defects. Cartilage repair was graded by three observers with different experience in cartilage research at 2-3 time points and compared with the protocol A of the international cartilage repair society (ICRS) cartilage repair assessment score, the Oswestry arthroscopy score, and macroscopic grading systems designed by Jung and O'Driscoll. Parameters were correlated with the two-dimensional (2D) magnetic resonance observation of cartilage repair tissue (MOCART) score based on a 9.4 T MRI as an external reference standard.

RESULTS

All macroscopic scores exhibited high intra- and interobserver reliability and high internal correlation. The newly developed macroscopic scoring system had the highest intraobserver [0.866 ≤ intraclass correlation (ICC) ≤ 0.895] and the highest interobserver reliability (ICC = 0.905) for "total points". Here, Cronbach's alpha indicated good homogeneity and functioning of the items (mean = 0.782). "Total points" of the 2D MOCART score correlated with all macroscopic scores (all P < 0.0001). The newly developed macroscopic scoring system yielded the highest correlation for the MRI parameter "defect fill" (rho = 0.765; all P < 0.0001).

CONCLUSIONS

"Total points" and "defect fill", two clinically relevant indicators of cartilage repair, can be reliably and directly assessed by macroscopic evaluation, using either system. These data support the use of macroscopic assessment to precisely judge cartilage repair in preclinical large animal models.

Imaging cartilage physiology

Osteoarthritis (OA) is a common disease that results in cartilage degeneration in the joints and is a disabling condition for millions of individuals. Poor sensitivity and specificity of standard diagnostic methods have relegated treatment options to mitigating pain or surgical replacement. The advent of disease-modifying drugs holds the potential for reversing the normal course of OA and rebuilding cartilage. To aid these therapies, novel magnetic resonance imaging-based tools are required for detecting subtle early changes in cartilage physiology due to OA that may provide improved diagnoses and clinical management of patients. Some of the techniques reviewed here such as T1ρ and T2 relaxometry, magnetization transfer, chemical exchange saturation transfer, and Na magnetic resonance imaging are all biomarkers of cartilage pathological diseases that are sensitive to early biochemical changes in the extracellular matrix of cartilage. These techniques have the potential to noninvasively detect early pathological changes with the goal of aiding clinical decision making as well as contributing to the development and evaluation of potential disease-modifying therapies.

In vitro phenotypic modulation of chondrocytes from knees of patients with osteochondritis dissecans: implications for chondrocyte implantation procedures

We attempted to characterise the biological quality and regenerative potential of chondrocytes in osteochondritis dissecans (OCD). Dissected fragments from ten patients with OCD of the knee (mean age 27.8 years (16 to 49)) were harvested at arthroscopy. A sample of cartilage from the intercondylar notch was taken from the same joint and from the notch of ten patients with a traumatic cartilage defect (mean age 31.6 years (19 to 52)). Chondrocytes were extracted and subsequently cultured. Collagen types 1, 2, and 10 mRNA were quantified by polymerase chain reaction. Compared with the notch chondrocytes, cells from the dissecate expressed similar levels of collagen types 1 and 2 mRNA. The level of collagen type 10 message was 50 times lower after cell culture, indicating a loss of hypertrophic cells or genes. The high viability, retained capacity to differentiate and metabolic activity of the extracted cells suggests preservation of the intrinsic repair capability of these dissecates. Molecular analysis indicated a phenotypic modulation of the expanded dissecate chondrocytes towards a normal phenotype. Our findings suggest that cartilage taken from the dissecate can be reasonably used as a cell source for chondrocyte implantation procedures.

Midterm results of the treatment of cartilage defects in the knee using alginate beads containing human mature allogenic chondrocytes

BACKGROUND

The treatment of chondral lesions is still an important challenge for the orthopaedic surgeon. Attempts have been made to restore cartilage lesions by filling the defects with a temporary biocompatible matrix.

PURPOSE

The authors present their midterm experience with the implantation of alginate beads containing human mature allogenic chondrocytes for the treatment of cartilage lesions in the knee.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A biodegradable, alginate-based biocompatible scaffold containing human mature allogenic chondrocytes was used for the treatment of cartilage lesions in the knee. Twenty-one patients were clinically prospectively evaluated with use of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and a visual analog scale (VAS). The mean follow-up time was 6.3 years (range, 5-8 years). Magnetic resonance imaging (MRI) data were analyzed based on the MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) system, allowing morphologic assessment of the repair tissue. Magnetic resonance images were taken at 1 year of follow-up and at a mean follow-up of 6.1 years (range, 5-7 years).

RESULTS

During the follow-up period, the WOMAC and VAS scores improved significantly. No signs of clinical deterioration or adverse reactions to the alginate beads/allogenic chondrocyte implantation were observed. Four failures occurred during the follow-up period in this study (19.05%). The MOCART scores were moderate and remained stable in time.

CONCLUSION

This investigation provided useful information on the efficacy of the implantation of alginate beads containing human mature allogenic chondrocytes for the treatment of cartilage lesions in the knee. The midterm clinical outcome of the presented technique was satisfactory. However, these results were not confirmed by the MRI findings.

Direct delayed human adenoviral BMP-2 or BMP-6 gene therapy for bone and cartilage regeneration in a pony osteochondral model

OBJECTIVE

To evaluate healing of surgically created large osteochondral defects in a weight-bearing femoral condyle in response to delayed percutaneous direct injection of adenoviral (Ad) vectors containing coding regions for either human bone morphogenetic proteins 2 (BMP-2) or -6.

METHODS

Four 13mm diameter and 7mm depth circular osteochondral defects were drilled, 1/femoral condyle (n=20 defects in five ponies). At 2 weeks, Ad-BMP-2, Ad-BMP-6, Ad-green fluorescent protein (GFP), or saline was percutaneously injected into the central drill hole of the defect. Quantitative magnetic resonance imaging (qMRI) and computed tomography (CT) were serially performed at 12, 24, and 52 weeks. At 12 (one pony) or 52 weeks, histomorphometry and microtomographic analyses were performed to assess subchondral bone and cartilage repair tissue quality.

RESULTS

Direct delivery of Ad-BMP-6 demonstrated delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) and histologic evidence of greater Glycosaminoglycan (GAG) content in repair tissue at 12 weeks, while Ad-BMP-2 had greater non-mineral cartilage at the surface at 52 weeks (p<0.04). Ad-BMP-2 demonstrated greater CT subchondral bone mineral density (BMD) by 12 weeks and both Ad-BMP-2 and -6 had greater subchondral BMD at 52 weeks (p<0.05). Despite earlier (Ad-BMP-6) and more persistent (Ad-BMP-2) chondral tissue and greater subchondral bone density (Ad-BMP-2 and -6), the tissue within the large weight-bearing defects at 52 weeks was suboptimal in all groups due to poor quality repair cartilage, central fibrocartilage retention, and central bone cavitation. Delivery of either BMP by this method had greater frequency of subchondral bone cystic formation (p<0.05).

CONCLUSIONS

Delivery of Ad-BMP-2 or Ad-BMP-6 via direct injection supported cartilage and subchondral bone regeneration but was insufficient to provide long-term quality osteochondral repair.

Remodeling of articular cartilage and subchondral bone after bone grafting and matrix-associated autologous chondrocyte implantation for osteochondritis dissecans of the knee

BACKGROUND

Osteochondritis dissecans (OCD) of the knee is a challenging problem. Previously, the authors implemented a novel 1-step surgical procedure for OCD treatment consisting of matrix-associated autologous chondrocyte implantation (ACI) and simultaneous bone reconstruction including the subchondral lamina.

PURPOSE

This study presents the 2-to 5-year results after this technique, assessing correlations of clinical function and cartilage and bone remodeling processes.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Twenty-six patients with symptomatic condylar knee OCD (International Cartilage Repair Society OCD III/IV) were treated with matrix-associated ACI and monocortical cancellous cylinders for defect filling and subchondral bone plate reconstruction using cortical graft layers as novel subchondral lamina. Evaluations were performed with clinical rating scales and 1.5-T magnetic resonance imaging using the magnetic resonance observation of cartilage repair tissue (MOCART) score and a newly implemented subchondral lamina remodeling grade.

RESULTS

The defect size was 5.3 ± 2.3 cm(2). The defect depth was 8.7 ± 2.4 mm. After a follow-up of 39.8 ± 12.0 months, all scores improved significantly. Nineteen patients (73%) reached good/excellent results in the Lysholm-Gillquist score (preoperatively: 53.2 ± 18.0 points; latest follow-up: 88.5 ± 9.5 points) and the Cincinnati knee rating score (preoperatively: 51.7 ± 13.0 points; latest follow-up: 84.6 ± 11.7 points) and significant improvements in the subjective International Knee Documentation Committee (IKDC) score by 27.9% (preoperatively: 50.5% ± 16.1%; latest follow-up: 78.4% ± 13.4%). The MOCART score reached 62.4 ± 18.9 points. The clinical improvement and tissue remodeling occurred simultaneously and timed; thus, the cartilage defect filling and the lamina remodeling grades correlated significantly with each other, the follow-up time, and almost all clinical scores.

CONCLUSION

The simultaneous reconstruction of deep osteochondral defects of the knee OCD with monocortical cancellous cylinders and matrix-associated ACI is a biological, 1-step alternative to osteochondral cylinder transfer or conventional ACI that leads to good clinical and magnetic resonance imaging results after an intermediate follow-up period. The present study demonstrated simultaneous remodeling processes of articular cartilage repair tissue and subchondral lamina; this synchronization is not yet understood and deserves further investigation.

Value of T2-mapping and DWI in the diagnosis of early knee cartilage injury

OBJECTIVE

To study the value of T2-mapping and diffusion weighted imaging (DWI) in the diagnosis of early injury of knee cartilage.

METHODS

Seventy-two subjects, including healthy group (n=30) and early cartilage injury group (n=42), were tested on MR scans with T2-mapping and DWI. T2 and apparent diffusion coefficient (ADC) values of cartilage were measured after being processed at the workstation, and the differences were statistically analyzed between the two groups.

RESULTS

The mean T2 and ADC values of cartilage in early injury group and health group were respectively 51.58±4.15 ms and 1.78±0.35 ×10(-3) mm(2)/s, 39.54±4.02 ms and 1.44±0.17 ×10(-3) mm(2)/s. There was significant difference between the values of T2 and ADC.

CONCLUSION

T2 and ADC values in early cartilage injury have obviously increased. T2-mapping and DWI have high clinical value in the diagnosis of early articular cartilage injury.

Matrix-induced autologous chondrocyte implantation of the knee: mid-term and long-term follow-up by MR arthrography

OBJECTIVE

To define magnetic resonance (MR) arthrography imaging findings of matrix-induced autologous chondrocyte implantation (MACI) grafts of the knee in order to describe implant behaviour and to compare findings with validated clinical scores 30 and 60 months after MACI implant.

MATERIALS AND METHODS

Thirteen patients were recruited (10 male, 3 female) with a total number of 15 chondral lesions. Each patient underwent an MACI procedure and MR arthrography 30 and 60 months after surgery. MR arthrography was performed using a dedicated coil with a 1.5-Tesla unit. The status of the chondral implant was evaluated with the modified MOCART scoring scale. The lining of the implant, the integration to the border zone, the surface and structure of the repaired tissue were assessed, and the presence of bone marrow oedema and effusion was evaluated. For clinical assessment, the Cincinnati score was used.

RESULTS

At 60 months, the abnormality showed worsening in 1 out of 15 cases. Integration showed improvement in 3 out of 15 cases, and worsening in 3 out of 15 cases. Two surfaces of the implant showed further deterioration at 60 months, and 1 afflicted implant fully recovered after the same time interval. Implant contrast enhancement at 30 months was seen in 2 out of 15 cases, 1 of which recovered at 60 months. According to the MOCART score, 4 cases were rated 68.4 out of 75 at 30 months and 65 out of 75 at 60 months. The mean clinical score decreased from 8.6 out of 10 at 30 months to 8.1 out of 10 at 60 months.

CONCLUSION

Magnetic resonance arthrography improved the evaluation of implants and facilitated the characterisation of MACI integration with contiguous tissues. The follow-up showed significant changes in MACI, even at 60 months, allowing for useful long-term MR evaluations.

Magnetic Resonance Imaging of Cartilage Repair: A Review

Articular cartilage lesions are a common pathology of the knee joint, and many patients may benefit from cartilage repair surgeries that offer the chance to avoid the development of osteoarthritis or delay its progression. Cartilage repair surgery, no matter the technique, requires a noninvasive, standardized, and high-quality longitudinal method to assess the structure of the repair tissue. This goal is best fulfilled by magnetic resonance imaging (MRI). The present article provides an overview of the current state of the art of MRI of cartilage repair. In the first 2 sections, preclinical and clinical MRI of cartilage repair tissue are described with a focus on morphological depiction of cartilage and the use of functional (biochemical) MR methodologies for the visualization of the ultrastructure of cartilage repair. In the third section, a short overview is provided on the regulatory issues of the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) regarding MR follow-up studies of patients after cartilage repair surgeries.

In vivo sodium imaging of human patellar cartilage with a 3D cones sequence at 3 T and 7 T

PURPOSE

To compare signal-to-noise ratios (SNRs) and T*(2) maps at 3 T and 7 T using 3D cones from in vivo sodium images of the human knee.

MATERIALS AND METHODS

Sodium concentration has been shown to correlate with glycosaminoglycan content of cartilage and is a possible biomarker of osteoarthritis. Using a 3D cones trajectory, 17 subjects were scanned at 3 T and 12 at 7 T using custom-made sodium-only and dual-tuned sodium/proton surface coils, at a standard resolution (1.3 x 1.3 x 4.0 mm(3)) and a high resolution (1.0 x 1.0 x 2.0 mm(3)). We measured the SNR of the images and the T*(2) of cartilage at both 3 T and 7 T.

RESULTS

The average normalized SNR values of standard-resolution images were 27.1 and 11.3 at 7 T and 3 T. At high resolution, these average SNR values were 16.5 and 7.3. Image quality was sufficient to show spatial variations of sodium content. The average T*(2) of cartilage was measured as 13.2 +/- 1.5 msec at 7 T and 15.5 +/- 1.3 msec at 3 T.

CONCLUSION

We acquired sodium images of patellar cartilage at 3 T and 7 T in under 26 minutes using 3D cones with high resolution and acceptable SNR. The SNR improvement at 7 T over 3 T was within the expected range based on the increase in field strength. The measured T*(2) values were also consistent with previously published values.

Comparison of MRI and arthroscopy after autologous chondrocyte implantation in patients with osteochondral lesion of the talus

No reported postoperative evaluation method is accurately correlated with the clinical outcome of repaired cartilage after autologous chondrocyte implantation. This study investigated the correlation of follow-up magnetic resonance imaging (MRI) evaluation and arthroscopic findings to the clinical outcome of surgically repaired osteochondral lesion of the talus with autologous chondrocyte implantation using the modified magnetic resonance observation of cartilage repair tissue (MOCART) scoring system.The study group comprised 21 consecutive patients with an osteochondral lesion of the talus who underwent autologous chondrocyte implantation. One year postoperatively, a follow-up MRI was obtained and a second-look arthroscopy was performed. Although the arthroscopic findings of the repaired osteochondral lesion of the talus showed better correlation with the clinical outcome when used with the modified MOCART scoring system, the higher correlation occurred only within a statistical error range, thus making the correlation not significantly different from the one determined on MRI. Therefore, a second-look arthroscopy is not necessary to evaluate the repaired talar cartilage after an autologous chondrocyte implantation. Magnetic resonance imaging is a useful method for long-term follow-up of patients with osteochondral lesions of the talus.

The subchondral bone in articular cartilage repair: current problems in the surgical management

As the understanding of interactions between articular cartilage and subchondral bone continues to evolve, increased attention is being directed at treatment options for the entire osteochondral unit, rather than focusing on the articular surface only. It is becoming apparent that without support from an intact subchondral bed, any treatment of the surface chondral lesion is likely to fail. This article reviews issues affecting the entire osteochondral unit, such as subchondral changes after marrow-stimulation techniques and meniscectomy or large osteochondral defects created by prosthetic resurfacing techniques. Also discussed are surgical techniques designed to address these issues, including the use of osteochondral allografts, autologous bone grafting, next generation cell-based implants, as well as strategies after failed subchondral repair and problems specific to the ankle joint. Lastly, since this area remains in constant evolution, the requirements for prospective studies needed to evaluate these emerging technologies will be reviewed.

Assessing degeneration of human articular cartilage with ultra-short echo time (UTE) T2* mapping

OBJECTIVE

To examine the sensitivity of ultra-short echo time (UTE) T(2)* mapping to collagen matrix degeneration in human articular cartilage.

METHODS

Magnetic resonance imaging (MRI) UTE-T(2)* maps and standard T(2) maps were acquired on four human tibial plateau explants. Thirty-three osteochondral cores were harvested for polarized light microscopy (PLM), and composition analyses. Collagen matrix integrity was evaluated from PLM and histological images. Matrix integrity and composition was compared to standard T(2) values and UTE-T(2)* values on a spatially registered basis.

RESULTS

UTE-T(2)* values varied with matrix degeneration (P=0.008) and were lower in severely degraded cartilage compared to healthy tissue (P=0.012). A trend for higher UTE-T(2)* values in healthy tissue compared to mildly degenerate tissue (P=0.051) was detected. Standard T(2) values were not found to vary with matrix degeneration (P=0.13) but tended to be higher in severely degraded cartilage compared to healthy tissue. UTE-T(2)* value variations were independent of type-II collagen and glycosaminoglycan contents. UTE-T(2)* mapping of deep cartilage, adjacent to subchondral bone, was more robust than standard T(2) mapping in this zone.

CONCLUSION

UTE-T(2)* mapping of articular cartilage is sensitive to matrix degeneration and detects short-T(2) signal, particularly in deep tissue, that is not well captured by standard T(2) mapping. Correlation of UTE-T(2)* values and PLM indices supports the hypothesis that both may be sensitive to collagen microstructure. Further exploration of UTE-T(2)* mapping as a non-invasive tool to detect early articular cartilage degeneration is warranted.

Accuracy of diagnostic arthroscopy for the assessment of cartilage damage in the equine metacarpophalangeal joint

REASONS FOR PERFORMING STUDY

There are many noninvasive diagnostic methods used for evaluating chronic progressive joint disease, but each has severe limitations in the detection of early articular cartilage damage.

OBJECTIVES

To evaluate the accuracy of arthroscopy as a diagnostic method for the assessment of the severity of cartilage surface damage on the proximal articular margin of the equine first phalanx (P1).

HYPOTHESIS

That arthroscopic assessment of the visible cartilage provides 1) a good indication of the integrity of the cartilage surface and 2) a good estimation of the status of the cartilage surface of the entire articular area of P1.

METHODS

Arthroscopic examination of the dorsal pouch of the metacarpophalangeal joint was performed in the left front limbs of 74 slaughter horses (age 5 months to 23 years). The appearance of the visible cartilage of P1 was scored by 2 independent arthroscopists, using the SFA arthroscopic grading system. The joints were dissected after completion of the arthroscopic procedure. The cartilage degeneration index (CDIP1) was determined and used as a quantitative measure for the overall degree of cartilage surface deterioration on the articular area of P1. Further, CDI values were determined for the dorsal articular margin of P1 (CDIdam), i.e. the area that can be visualised with arthroscopy. The CDIdam values were classified into 3 groups (CDIdam<25%, minor lesions; 25%<CDIdam<45%, moderate lesions; and CDIdam>45%, severe lesions). Differences between the 2 arthroscopists were evaluated statistically in a nonparametric test and Pearson correlation coefficients (r) with matching P values were determined for the correlations between SFA and CDIdam and between CDIP1 and CDIdam. The level of significance was set at P<0.05.

RESULTS

Differences between SFA scores of the 2 arthroscopists were not significant (P = 0.22). In the group of joints with minor cartilage changes, there was no correlation between SFA and CDIdam (r = 0.12; P = 0.71), but there was a significant correlation between CDIP1 and CDIdam (r = 0.95; P<0.01). In the group with moderate cartilage damage, there was an increase in correlation between SFA and CDIdam (r = 0.27; P = 0.09) and a decrease in the correlation between CDIP1 and CDIdam (r = 0.48; P<0.01). In the group with severe cartilage changes, there was a significant correlation between SFA and CDIdam (r = 058; P<0.01), but no significant correlation between CDIP1 and CDIdam (r = 0.43; P = 0.06).

CONCLUSIONS

Arthroscopic assessment of cartilage lesions on the proximal articular surface of P1 in joints with minor cartilage damage leads to an underestimation of the actual damage because proteoglycan depletion and light cartilage fibrillation cannot be detected arthroscopically. In cases with mild cartilage damage, the status of the cartilage surface of the visible area of P1 is a good representation of the status of the entire articular surface. In cases with severe cartilage lesions, there is an overestimation of real damage. In such joints, the arthroscopic scoring system provides reliable information, but the visible area is not representative of the entire articular surface.

POTENTIAL RELEVANCE

From a practical viewpoint, it can be stated that the arthroscopic grading of visible lesions on the equine P1 gives the best impression of overall cartilage damage in joints with moderately severe cartilage lesions. It should be realised, however, that this is the result of an underestimation due to the shortcomings of the grading system, which is neutralised by an overestimation due to the fact that the severity of lesions on the visible area of P1 is not representative for the entire articular surface.

Pre- and postoperative assessment in joint preserving and replacing surgery

Advances in imaging technology have increased its suitability for diagnosing musculoskeletal disease. Modification of imaging techniques and improved image quality have led to increased use of computed tomography and magnetic resonance imaging in the assessment of postoperative complications. This article discusses the indications, pre- and postoperative imaging findings, and postoperative complications of knee and hip arthroplasty, articular cartilage repair, and high tibial osteotomy.

Knee-to-ankle mosaicplasty for the treatment of osteochondral lesions of the ankle joint

BACKGROUND

Osteochondral lesions are frequently seen in athletes after ankle injuries. At this time, osteochondral autologous transplantation (OATS, mosaicplasty) is the only surgical treatment that replaces the entire osteochondral unit in symptomatic lesions.

PURPOSE

To evaluate the clinical and radiological midterm to long-term outcome of ankles treated with knee-to-ankle mosaicplasty.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Clinical evaluation consisted of patient satisfaction, pain evaluation (visual analog scale [VAS]), American Orthopaedic Foot and Ankle Society (AOFAS) ankle score, sports activity score, range of motion, the radiological evaluation of magnetic resonance imaging (MRI), and single photon emission computed tomography-computed tomography (SPECT-CT) analysis of both the ankle and the knee joint.

RESULTS

Twelve of 21 patients (mean age, 43 years; male, 8; female, 4) were available for latest follow-up (mean, 72 months). At follow-up, patients reported a satisfaction rate of good to excellent in 92% (n = 11) and poor in 8% (n = 1). The average VAS pain score was 3.9 (preoperative, 5.9; P = .02), AOFAS ankle score significantly increased from 45.9 to 80.2 points (P < .0001), sports activity score remained significantly decreased with 1.25 (preinjury level, 2.3; P = .035), and ankle dorsiflexion was significantly reduced (P = .003). Knee pain was reported in 6 patients (50%). Radiologically, recurrent lesions were found in 10 of 10 cases (100%) and some degree of cartilage degeneration and discontinuity of the subchondral bone plate in 100%.

CONCLUSION

Indications for mosaicplasty with a plug transfer from the knee to the talus must be considered carefully, as at midterm, moderate outcome and considerable donor-site morbidity may be found.

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.