Cartilage repair of the ankle: first results of T2 mapping at 7.0 T after microfracture and matrix associated autologous cartilage transplantation

Arthroscopic microfracture and associated techniques in the treatment of osteochondral lesions of the talus: A systematic review and metanalysis

BACKGROUND

Osteochondral lesions of the talus are common in patients suffering even minor trauma; timely diagnosis and treatment can prevent the development of early osteoarthritis. The objectives of this systematic review and meta-analysis were to evaluate the effects of additional procedures on arthroscopic ankle microperforations for osteochondral lesions.

METHODS

A systematic literature search was conducted using PubMed-Medline, Cochrane Central, and Google Scholar to select clinical studies analyzing the efficacy of platelet-rich plasma (PRP), hyaluronic acid (HA), and bone marrow concentrate (BMC) procedures. Ten articles following PRISMA guidelines with a total of 464 patients were included in this review. Quality assessment using MINORS was performed, and all studies demonstrated high quality.

RESULTS

The results of the systematic review showed benefits in all patients undergoing infiltrative therapy with PRP, hyaluronic acid, and BMC. The best results in terms of AOFAS score and VAS scale were found in patients undergoing PRP injection. The meta-analysis showed improvements in pain relief and return to daily activities in patients undergoing arthroscopic microperforations and PRP, although not reporting statistically significant results (p = 0.42).

CONCLUSION

All treatment strategies reported better scores compared to the control groups. Among the various treatments analyzed, the addition of PRP appears to be the most valuable probably for the larger population receiving this treatment, showing excellent outcomes in pain reduction, clinical outcomes, and return to daily activities.

LEVEL OF EVIDENCE

II.

T2 mapping for quantitative assessment of ankle cartilage of weightlifters

The research into the prevention of sports injuries among the population, particularly juveniles, has become crucial due to the increasing participation in physical exercises like fitness. To assess the difference in T2 values of ankle talar cartilage between weightlifters and healthy volunteers using quantitative magnetic resonance imaging (MRI) technique T2 mapping. Study design: Prospective. Prospective evaluation of T2 values of ankle cartilage of 50 weightlifters (30 adults and 20 juveniles) and 100 healthy volunteers (80 adults and 20 juveniles) using Siemens 3.0 T MRI with PDWI, T1WI, and T2 mapping sequences. Three physicians manually divided the talar cartilage of the ankle joint into six regions of interest. Three physicians utilized the anterior and posterior cut edges of the tibial cartilage as markers to identify the corresponding anterior and posterior cut edges of the talar cartilage on the sagittal MRI images. The medial and lateral sides were defined as half of the talar articular surface on the coronal plane. Differences in T2 values in each cartilage region were compared using independent sample T test or Mann-Whitney U test. The T2 values of talar cartilage were significantly increased in the athlete group relative to the volunteer group (35.11 and 31.99, P < 0.001), with the most significant difference observed in the juvenile athlete group compared to the volunteer group (34.42 and 28.73, P < 0.001). There was a significant difference in the T2 value of ankle talar cartilage between weightlifters and healthy volunteers, and juveniles may be more vulnerable to overuse sports injuries. This study contributes to understanding the cartilage health of juvenile athletes and the prevention of sports injuries.

Autologous Osteochondral Transplantation for Osteochondral Lesions of the Talus-Does Sex Play a Role?

Autologous osteochondral transplantation (AOT) is used in the treatment of osteochondral lesions (OCL) of the talus. The purpose of this study was to compare the differences in the presentation of talar OCLs and outcomes following AOT between male and female patients. Eighty-seven consecutive patients, ages 16 to 65 years, who underwent AOT were retrospectively reviewed. Patients were divided into 2 groups based on sex. Demographic data and OCL defect characteristic data were recorded. Functional outcomes were assessed pre- and postoperatively using the Foot and Ankle Outcome Score (FAOS). The Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) score was used to assess cartilage incorporation. Fifty-six (64%) males and 31 (36%) females with mean clinical follow-up of 47.2 months were included in this study. OCL defect size was significantly larger in male patients (112.8 mm²) when compared with female patients (88.7 mm²) (p < .001). Male patients presented with a lesion associated with a recognized trauma (p < .006) when compared with female patients who typically presented with associated chronic ankle instability. Mean FAOS improved pre- to postoperatively from 50 to 81 (p < .001) with a statistically significant increase found in male patients (p < .001). The mean MOCART score was 82.1 in male and 86.7 female patients (p < .001). Our study demonstrates potential gender-related differences in the presentation and mechanism of injury in the development of OCLs. It is also not unreasonable to suggest that there may also be differences in treatment and rehabilitation strategies to reduce the risk of developing OCLs in men and women.

Prognostic factors for the management of chondral defects of the knee and ankle joint: a systematic review

Purpose

Different surgical techniques to manage cartilage defects are available, including microfracture (MFx), autologous chondrocyte implantation (ACI), osteoarticular auto- or allograft transplantation (OAT), autologous matrix-induced chondrogenesis (AMIC). This study investigated the patient-related prognostic factors on the clinical outcomes of surgically treated knee and ankle cartilage defects.

Methods

This study followed the PRISMA statement. In May 2022, the following databases were accessed: PubMed, Google Scholar, Embase, and Scopus. All the studies investigating the outcomes of surgical management for knee and/or talus chondral defects were accessed. Only studies performing mesenchymal stem cells transplantation, OAT, MFx, ACI, and AMIC were considered. A multiple linear model regression analysis through the Pearson Product–Moment Correlation Coefficient was used.

Results

Data from 184 articles (8905 procedures) were retrieved. Female sex showed a positive moderate association with visual analogue scale at last follow-up (P = 0.02). Patient age had a negative association with the American Orthopaedic Foot and Ankle Score (P = 0.04) and Lysholm Knee Scoring Scale (P = 0.03). BMI was strongly associated with graft hypertrophy (P = 0.01). Greater values of VAS at baseline negatively correlate with lower values of Tegner Activity Scale at last follow-up (P < 0.0001).

Conclusion

The clinical outcomes were mostly related to the patients’ performance status prior surgery. A greater BMI was associated with greater rate of hypertrophy. Female sex and older age evidenced fair influence, while symptom duration prior to the surgical intervention and cartilage defect size evidenced no association with the surgical outcome. Lesion size and symptom duration did not evidence any association with the surgical outcome.

Surgical Management of Focal Chondral Defects of the Talus: A Bayesian Network Meta-analysis

BACKGROUND

No consensus has been reached regarding the optimal surgical treatment for focal chondral defects of the talus.

PURPOSE

A Bayesian network meta-analysis was conducted to compare the clinical scores and complications of mosaicplasty, osteochondral auto- and allograft transplant, microfracture, matrix-assisted autologous chondrocyte transplant, and autologous matrix-induced chondrogenesis (AMIC) for chondral defects of the talus at midterm follow-up.

STUDY DESIGN

Bayesian network meta-analysis; Level of evidence, 4.

METHODS

This Bayesian network meta-analysis followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) extension statement for reporting of systematic reviews incorporating network meta-analyses of health care interventions. PubMed, Embase, Google Scholar, and Scopus databases were accessed in February 2021. All clinical trials comparing 2 or more surgical interventions for the management of chondral defects of the talus were accessed. The outcomes of interest were visual analog scale (VAS) score, American Orthopaedic Foot and Ankle Society (AOFAS) score, rate of failure, and rate of revision surgery. The network meta-analysis were performed through the routine for Bayesian hierarchical random-effects model analysis. The log odds ratio (LOR) effect measure was used for dichotomous variables, and the standardized mean difference (SMD) was used for continuous variables.

RESULTS

Data from 13 articles (521 procedures) were retrieved. The median length of the follow-up was 47.8 months (range, 31.7-66.8 months). Analysis of variance revealed no difference between the treatment groups at baseline in terms of age, sex, body mass index, AOFAS score, VAS score, and mean number of defects. AMIC demonstrated the greatest AOFAS score (SMD, 11.27) and lowest VAS score (SMD, -2.26) as well as the lowest rates of failure (LOR, 0.94) and revision (LOR, 0.94). The test for overall inconsistency was not significant.

CONCLUSION

At approximately 4 years of follow-up, the AMIC procedure for management of focal chondral defects of the talus produced the best outcome.

Adjacent cartilage tissue structure after successful transplantation: a quantitative MRI study using T2 mapping and texture analysis

OBJECTIVES

The aim of this study was to assess the texture of repair tissue and tissue adjacent to the repair site after matrix-associated chondrocyte transplantation (MACT) of the knee using gray-level co-occurrence matrix (GLCM) texture analysis of T₂ quantitative maps.

METHODS

Twenty patients derived from the MRI sub-study of multicenter, single-arm phase III study underwent examination on a 3 T MR scanner, including a T₂ mapping sequence 12 and 24 months after MACT. Changes between the time points in mean T₂ values and 20 GLCM features were assessed for repair tissue, adjacent tissue, and reference cartilage. Differences in T₂ values and selected GLCM features between the three cartilage sites at two time points were analyzed using linear mixed-effect models.

RESULTS

A significant decrease in T₂ values after MACT, between time points, was observed only in repair cartilage (p < 0.001). Models showed significant differences in GLCM features between repair tissue and reference cartilage, namely, autocorrelation (p < 0.001), correlation (p = 0.015), homogeneity (p = 0.002), contrast (p < 0.001), and difference entropy (p = 0.047). The effect of time was significant in a majority of models with regard to GLCM features (except autocorrelation) (p ≤ 0.001). Values in repair and adjacent tissue became similar to reference tissue over time.

CONCLUSIONS

GLCM is a useful add-on to T₂ mapping in the evaluation of knee cartilage after MACT by increasing the sensitivity to changes in cartilage structure. The results suggest that cartilage tissue adjacent to the repair site heals along with the cartilage implant.

KEY POINTS

• GLCM is a useful add-on to T₂ mapping in the evaluation of knee cartilage after MACT by increasing the sensitivity to changes in cartilage structure. • Repair and adjacent tissue became similar to reference tissue over time. • The results suggest that cartilage tissue adjacent to the repair site heals along with the cartilage implant.

Accuracy of MRI-Based Talar Cartilage Thickness Measurement and Talus Bone and Cartilage Modeling: Comparison with Ground-Truth Laser Scan Measurements

OBJECTIVE

The purpose of this work was to compare measurements of talar cartilage thickness and cartilage and bone surface geometry from clinically feasible magnetic resonance imaging (MRI) against high-accuracy laser scan models. Measurement of talar bone and cartilage geometry from MRI would provide useful information for evaluating cartilage changes, selecting osteochondral graft sources or creating patient-specific joint models.

DESIGN

Three-dimensional (3D) bone and cartilage models of 7 cadaver tali were created using (1) manual segmentation of high-resolution volumetric sequence 3T MR images and (2) laser scans. Talar cartilage thickness was compared between the laser scan- and MRI-based models for the dorsal, medial, and lateral surfaces. The laser scan- and MRI-based cartilage and bone surface models were compared using model-to-model distance.

RESULTS

Average cartilage thickness within the dorsal, medial, and lateral surfaces were 0.89 to 1.05 mm measured with laser scanning, and 1.10 to 1.22 mm measured with MRI. MRI-based thickness was 0.16 to 0.32 mm higher on average in each region. The average absolute surface-to-surface differences between laser scan- and MRI-based bone and cartilage models ranged from 0.16 to 0.22 mm for bone (MRI bone models smaller than laser scan models) and 0.35 to 0.38 mm for cartilage (MRI bone models larger than laser scan models).

CONCLUSIONS

This study demonstrated that cartilage and bone 3D modeling and measurement of average cartilage thickness on the dorsal, medial, and lateral talar surfaces using MRI were feasible and provided similar model geometry and thickness values to ground-truth laser scan-based measurements.

Differentiation of Cartilage Repair Techniques Using Texture Analysis from T2 Maps

OBJECTIVE

The aim of this study was to investigate texture features from T2 maps as a marker for distinguishing the maturation of repair tissue after 2 different cartilage repair procedures.

DESIGN

Seventy-nine patients, after either microfracture (MFX) or matrix-associated chondrocyte transplantation (MACT), were examined on a 3-T magnetic resonance (MR) scanner with morphological and quantitative (T2 mapping) MR sequences 2 years after surgery. Twenty-one texture features from a gray-level co-occurrence matrix (GLCM) were extracted. The texture feature difference between 2 repair types was assessed individually for the femoral condyle and trochlea/anterior condyle using linear regression models. The stability and reproducibility of texture features for focal cartilage were calculated using intra-observer variability and area under curve from receiver operating characteristics.

RESULTS

There was no statistical significance found between MFX and MACT for T2 values (P = 0.96). There was, however, found a statistical significance between MFX and MACT in femoral condyle in GLCM features autocorrelation (P < 0.001), sum of squares (P = 0.023), sum average (P = 0.005), sum variance (P = 0.0048), and sum entropy (P = 0.05); and in anterior condyle/trochlea homogeneity (P = 0.02) and dissimilarity (P < 0.001).

CONCLUSION

Texture analysis using GLCM provides a useful extension to T2 mapping for the characterization of cartilage repair tissue by increasing its sensitivity to tissue structure. Some texture features were able to distinguish between repair tissue after different cartilage repair procedures, as repair tissue texture (and hence, probably collagen organization) 24 months after MACT more closely resembled healthy cartilage than did MFX repair tissue.

Osteochondral Lesions of the Talus: A Review on Talus Osteochondral Injuries, Including Osteochondritis Dissecans

This is a review on talus osteochondritis dissecans and talus osteochondral lesions. A majority of the osteochondral lesions are associated with trauma while the cause of pure osteochondritis dissecans is still much discussed with a possible cause being repetitive microtraumas associated with vascular disturbances causing subchondral bone necrosis and disability. Symptomatic nondisplaced osteochondral lesions can often be treated conservatively in children and adolescents while such treatment is less successful in adults. Surgical treatment is indicated when there is an unstable cartilage fragment. There are a large number of different operative technique options with no number one technique to be recommended. Most techniques have been presented in level II to IV studies with a low number of patients with short follow ups and few randomized comparisons exist. The actual situation in treating osteochondral lesions in the ankle is presented and discussed.

Demographics in Patients Receiving Matrix-Assisted Chondrocyte Implantation (MACI) in the Ankle

Objective. To compare demographics and cartilage lesion characteristics of patients enrolled in clinical trials investigating autologous chondrocyte implantation (ACI) in the ankle joint with those actually scheduled for matrix-assisted chondrocyte implantation (MACI) using database records. Design. Anonymized data from patients scheduled for MACI treatment in the ankle in Australia/Asia and Europe were obtained from the Genzyme/Sanofi database. Average age, defect size, and male-female ratio were analyzed and compared by country. A literature search was performed on PubMed and Google Scholar and clinical cohort studies and prospective comparative trials using ACI and related treatments in the ankle joint were identified. Weighted average age, weighted defect size, and male-female ratio were analyzed and compared with database data. Results. The 167 patients included from the databases from Europe and Australia had a mean age of 33.4 years (range 14-64 years) and a mean defect size of 2.27 cm² (range 0.25-16 cm²). Male-female ratio was 4:3. Patients from European countries were significantly younger and had significantly larger defects compared with patients from Australia. From the literature search a total of 472 patients were included from 28 studies. The mean age was 32.2 years (range 15-62 years). Male-female ratio was 3:2. Weighted mean size was 1.94cm² (range 0.3-16). There were no significant differences between previous studies and databases. Conclusion. No differences in sizes and age were found between patients enrolled in clinical trials and patients scheduled for MACI outside clinical trials. The sizes of treated defects followed the general recommendations. There were, however, significant differences between countries.

Arthroscopic one-step matrix-assisted bone marrow stimulation for the treatment of osteochondral defects of the talus

OBJECTIVE

All arthroscopic one-step treatment of osteochondral defects of the talus with matrix-assisted bone marrow stimulation with a cell-free hyaluronic acid 3D matrix.

INDICATIONS

Symptomatic osteochondral defects of the talus (1-2 cm², ICRS III-IV).

CONTRAINDICATIONS

Large non-shouldered osteochondral defects (2 cm²) of the talus, arthritis, kissing lesions of the distal tibia, metabolic arthropathies, non-reconstructable defects, hindfoot malalignment, chronic inflammatory systemic disorders.

SURGICAL TECHNIQUE

Arthroscopic examination of the ankle joint and visualization of the osteochondral defect of the talus to confirm the indication via standard portals. First, debridement of the osteochondral defect with arthroscopic curette or shaver, removal of loose fragments, resection of the sclerotic bone via shaver and measurement of the defect size. Second, multiple perforation of the subchondral plate to recruit mesenchymal stem cells from the underlying bone marrow by an microfracturing awl to stimulate the differentiation of fibrocartilaginous repair tissue in the defect zone. Then, the cell-free hyaluronic acid 3D matrix is placed into the defect via arthroscopic forceps and modulated by a probe to avoid detachment of the matrix by ankle joint movement.

POSTOPERATIVE MANAGEMENT

Postoperative management includes movement restrictions for pro- and supination but free passive dorsal extension and plantar flexion. No weight-bearing is allowed for 6 weeks.

RESULTS

Twenty-three patients (male: 11/women: 12) with a mean age of 33 years (range: 18-56) and a minimum follow-up of 24 months were included in this retrospective two-center study. The mean values for Foot and Ankle Outcome Score (FAOS) were 79 (range 33-93), for Tegner score 3 (range: 1-5) and the Visual analog scale (VAS) pain 1 (range: 0-3) and VAS function 2 (range: 0-5). At follow-up, MRI was available in 17 of 23 patients. MRI results showed a mean Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) score of 81 (range: 65-90). Complications were not observed during the follow-up period.

A flexible and biocompatible bombyx mori silk fibroin/wool keratin composite scaffold with interconnective porous structure

The paper describes the preparation of a porous bombyx mori silk fibroin (SF)/wool keratin (WK) composite scaffold with mimic structure and function for cartilage tissue engineering. A porous composite scaffold made from SF/WK in an appropriate concentration and mass ratio was prepared using a freeze-drying technique. Results showed that the composite scaffolds are water-insoluble; possess good mechanical properties, porosity above 80%, and pore size above 200 μm. Larger pore size and better connectivity of the composite scaffold than the pure SF scaffolds were contributed by the WK addition. The heat resistance and water-swelling of WK enhanced the thermal and mechanical properties of the composite scaffolds. In vitro cytotoxicity assessments showed cells with a good growth state, confirming no toxicity to the cells. The results of in vivo biocompatibility assessments exhibited that there is almost no inflammatory response in the implantation site tissue of the rats. The development of porous SF/WK composite scaffold has the potential in cartilage tissue engineering.

Operative treatments for osteochondral lesions of the talus in adults: A systematic review and meta-analysis

PURPOSE

This systematic review aimed to identify the available evidence regarding the comparative effectiveness and safety of various operative treatments in adult patients with osteochondral lesions of the talus (OLT).

MATERIALS AND METHODS

The PubMed, Embase, ISI Web of Knowledge, and the Cochrane Controlled Trial Register of Controlled Trials were searched from their inception date to September 2019. Two reviewers selected the randomized controlled trials (RCTs) and non-RCTs assessing the comparative effectiveness and safety of various operative treatments for OLT. The meta-analysis was performed using Revman 5.3.

RESULTS

Eight studies (1 RCT and 7 non-RCTs) with 375 patients were included in this review. The difference in the American Orthopaedic Foot and Ankle Society (AOFAS) score between the cartilage repair and replacement was not significant. The cartilage regeneration with or without cartilage repair had significant superiority in improving the AOFAS score compared with the cartilage repair. The difference in the magnetic resonance observation of cartilage repair tissue score between the cartilage repair and replacement and between cartilage repair and cartilage repair plus regeneration was significant.

CONCLUSIONS

Cartilage regeneration and cartilage repair plus regeneration had significant superiority in improving the ankle function and radiological evaluation of OLT, although the trials included did not have high-level evidence. Moreover, which treatment between the 2 was safer could not be addressed in this review as most of the trials did not report the safety outcome. Further studies are needed to define the best surgical option for treating OLT.

Quantitative MRI T2 Mapping Is Able to Assess Tissue Quality After Reparative and Regenerative Treatments of Osteochondral Lesions of the Talus

BACKGROUND

Quantitative MRI has potential for tissue characterization after reparative and regenerative surgical treatment of osteochondral lesions of the talus (OCLTs). However available data is inconclusive and quantitative sequences can be difficult to implement in real-time clinical application.

PURPOSE

To assess the potential of T2 mapping in discriminating articular tissue characteristics after reparative and regenerative surgery of OCLTs in real-world clinical settings.

STUDY TYPE

Observational and prospective cohort study.

POPULATION

15 OCLT patients who had received either reparative treatment with arthroscopic microfracture surgery (MFS) for a grade I lesion or regenerative treatment with bone marrow derived cell transplantation (BMDCT) for a grade II lesion.

FIELD STRENGTH/SEQUENCE

1.5 T, proton density weighted TSE, T2-weighted true fast imaging with steady-state-free precession and multi-echo T2 mapping sequences.

ASSESSMENT

Patients were evaluated at a minimum postoperative follow-up of 24 months. T2 maps of the ankle were generated and the distribution of T2 values was analyzed in manually identified volumes of interest (VOIs) for both treated lesions (TX) and healthy cartilage (CTRL). The amount of fibrocartilage, hyaline-like and remodeling tissue in TX VOIs was obtained, based on T2 thresholds from CTRL VOIs.

STATISTICAL TESTS

Fisher's exact test for categorical data, nonparametric Mann-Whitney U test for continuous data. The statistical significance level was P < 0.05.

RESULTS

From CTRL VOI analysis, T2 < 25 msec, 25 msec ≤ T2 ≤ 45 msec, and T2 > 45 msec were considered as representative for fibrocartilage, hyaline-like and remodeling tissue, respectively. Tissue composition of the two treatment groups was different, with significantly more fibrocartilage (+28%) and less hyaline-like tissue (-15%) in MFS than in BMDCT treated lesions. No difference in healthy tissue composition was found between the two groups (P = 0.75).

DATA CONCLUSIONS

T2 mapping of surgically treated OCLTs can provide quantitative information about the type and amount of newly formed tissue at the lesion site, thereby facilitating surgical follow-up in a real-word clinical setting.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 3.

Musculoskeletal MR Imaging Applications at Ultra-High (7T) Field Strength

Regulatory approval of ultrahigh field (UHF) MR imaging scanners for clinical use has opened new opportunities for musculoskeletal imaging applications. UHF MR imaging has unique advantages in terms of signal-to-noise ratio, contrast-to-noise ratio, spectral resolution, and multinuclear applications, thus providing unique information not available at lower field strengths. But UHF also comes with a set of technical challenges that are yet to be resolved and may not be suitable for all imaging applications. This review focuses on the latest research in musculoskeletal MR imaging applications at UHF including morphologic imaging, T₂, T₂∗, and T_1ρ mapping, chemical exchange saturation transfer, sodium imaging, and phosphorus spectroscopy imaging applications.

Musculoskeletal MRI at 7 T: do we need more or is it more than enough?

Ultra-high field magnetic resonance imaging (UHF-MRI) provides important diagnostic improvements in musculoskeletal imaging. The higher signal-to-noise ratio leads to higher spatial and temporal resolution which results in improved anatomic detail and higher diagnostic confidence. Several methods, such as T2, T2*, T1rho mapping, delayed gadolinium-enhanced, diffusion, chemical exchange saturation transfer, and magnetisation transfer techniques, permit a better tissue characterisation. Furthermore, UHF-MRI enables in vivo measurements by low-γ nuclei (²³Na, ³¹P, ¹³C, and ³⁹K) and the evaluation of different tissue metabolic pathways. European Union and Food and Drug Administration approvals for clinical imaging at UHF have been the first step towards a more routinely use of this technology, but some drawbacks are still present limiting its widespread clinical application. This review aims to provide a clinically oriented overview about the application of UHF-MRI in the different anatomical districts and tissues of musculoskeletal system and its pros and cons. Further studies are needed to consolidate the added value of the use of UHF-MRI in the routine clinical practice and promising efforts in technology development are already in progress.

Magnetic Resonance Imaging of the Musculoskeletal System at 7T: Morphological Imaging and Beyond

In 2017, a whole-body 7T magnetic resonance imaging (MRI) device was given regulatory approval for clinical use in both the EU and United States for neuro and musculoskeletal applications. As 7 Tesla allows for higher signal-to-noise , which results in higher resolution images than those obtained on lower-field-strength scanners, it has attracted considerable attention from the musculoskeletal field, as evidenced by the increasing number of publications in the last decade. Besides morphological imaging, the quantitative MR methods, such as T₂, T₂∗, T_1ρ mapping, sodium imaging, chemical-exchange saturation transfer, and spectroscopy, substantially benefit from ultrahigh field scanning. In this review, we provide technical considerations for the individual techniques and an overview of (mostly) clinical applications for the assessment of cartilage, tendon, meniscus, and muscle. The first part of the review is dedicated to morphological applications at 7T, and the second part describes the most recent developments in quantitative MRI at 7T.

[Advanced cartilage imaging for detection of cartilage injuries and osteochondral lesions]

BACKGROUND

Osteochondral defects represent a main risk factor for osteoarthritis of the ankle.

OBJECTIVES

The aim of this article is to provide an overview of current optimal clinical cartilage imaging techniques of the foot and ankle and to show typical osteochondral injuries on imaging.

MATERIALS AND METHODS

A thorough literature search was performed and was supported by personal experience.

RESULTS

Cartilage imaging of the foot and ankle remains challenging. However, advanced morphological and quantitative magnetic resonance (MR) imaging techniques may provide useful clinical information, for example, concerning cartilage repair surgery. Compared to MRI, MR arthrography (MR-A) and CT arthrography (CT-A) have higher sensitivity with respect to detection of osteochondral defects. Regarding smaller joints of the foot, mainly advanced osteoarthritic changes are detected on conventional radiography; only in rare cases, MR and CT imaging of these smaller joints is of relevance.

CONCLUSIONS

While at the smaller joints of the foot cartilage imaging only plays a minor role, at the ankle joint cross-sectional cartilage imaging using CT and MRI becomes more and more important for clinicians due to emerging therapeutic options, such as different osteochondral repair techniques.

MR Imaging of the Musculoskeletal System Using Ultrahigh Field (7T) MR Imaging

MR imaging is an indispensable instrument for the diagnosis of musculoskeletal diseases. In vivo MR imaging at 7T offers many advantages, including increased signal-to-noise ratio, higher spatial resolution, improved spectral resolution for spectroscopy, improved sensitivity for X-nucleus imaging, and decreased image acquisition times. There are also however technical challenges of imaging at a higher field strength compared with 1.5 and 3T MR imaging systems. We discuss the many potential opportunities as well as the challenges presented by 7T MR imaging systems and highlight recent developments in in vivo research imaging of musculoskeletal applications in general and cartilage, skeletal muscle, and bone in particular.

A new RF transmit coil for foot and ankle imaging at 7T MRI

A four-channel Tic-Tac-Toe (TTT) transmit RF coil was designed and constructed for foot and ankle imaging at 7T MRI. Numerical simulations using an in-house developed FDTD package and experimental analyses using a homogenous phantom show an excellent agreement in terms of B1+ field distribution and s-parameters. Simulations performed on an anatomically detailed human lower leg model demonstrated an B1+ field distribution with a coefficient of variation (CV) of 23.9%/15.6%/28.8% and average B1+ of 0.33μT/0.56μT/0.43μT for 1W input power (i.e., 0.25W per channel) in the ankle/calcaneus/mid foot respectively. In-vivo B1+ mapping shows an average B1+ of 0.29μT over the entire foot/ankle. This newly developed RF coil also presents acceptable levels of average SAR (0.07W/kg for 10g per 1W of input power) and peak SAR (0.34W/kg for 10g per 1W of input power) over the whole lower leg. Preliminary in-vivo images in the foot/ankle were acquired using the T2-DESS MRI sequence without the use of a dedicated receive-only array.

Scaffolds based therapy for osteochondral lesions of the talus: A systematic review

AIM

To clarify the effectiveness of scaffold-based therapy for osteochondral lesions of the talus (OLT).

METHODS

A systematic search of MEDLINE and EMBASE databases was performed during August 2016 and updated in January 2017. Included studies were evaluated with regard to the level of evidence (LOE) and quality of evidence (QOE) using the Modified Coleman Methodology Score. Variable reporting outcome data, clinical outcomes, and the percentage of patients who returned to sport at previous level were also evaluated.

RESULTS

Twenty-eight studies for a total of 897 ankles were included; 96% were either LOE III or IV. Studies were designated as either of poor or fair quality. There were 30 treatment groups reporting six different scaffold repair techniques: 13 matrix-induced autologous chondrocyte transplantation (MACT), nine bone marrow derived cell transplantation (BMDCT), four autologous matrix-induced chondrogeneis (AMIC), and four studies of other techniques. The categories of general demographics (93%) and patient-reported outcome data (85%) were well reported. Study design (73%), imaging data (73%), clinical variables (49%), and patient history (30%) were also included. The weighted mean American Orthopaedic Foot and Ankle Society (AOFAS) score at final follow-up was: 86.7 in MACT, 88.2 in BMDCT, and 82.3 in AMIC. Eight studies reported that a weighted mean of 68.3% of patients returned to a previous level of sport activity.

CONCLUSION

Scaffold-based therapy for OLT may produce favorable clinical outcomes, but low LOE, poor QOE, and variability of the data have confounded the effectiveness of this treatment.

Advanced MRI Techniques for the Ankle

OBJECTIVE

The purposes of this article are to present a state-of-the-art routine protocol for MRI of the ankle, to provide problem-solving tools based on specific clinical indications, and to introduce principles for the implementation of ultrashort echo time MRI of the ankle, including morphologic and quantitative assessment.

CONCLUSION

Ankle injury is common among both athletes and the general population, and MRI is the established noninvasive means of evaluation. The design of an ankle protocol depends on various factors. Higher magnetic field improves signal-to-noise ratio but increases metal artifact. Specialized imaging planes are useful but prolong acquisition times. MR neurography is useful, but metal reduction techniques are needed whenever a metal prosthesis is present. An ultrashort echo time sequence is a valuable tool for both structural and quantitative evaluation.

Five-Year Outcomes After Treatment for Acute Instability of the Tibiofibular Syndesmosis Using a Suture-Button Fixation System

Background:

Suture-button repair is a widely accepted surgical treatment for acute and isolated ankle syndesmosis injuries. To our knowledge, midterm results have not previously been reported.

Purpose:

To evaluate the clinical, qualitative, and quantitative radiological midterm outcomes of suture-button repair after acute isolated ankle syndesmosis injuries.

Study Design:

Retrospective case series; Level of evidence, 4.

Methods:

Clinical outcomes were measured using the Foot and Ankle Disability Index (FADI) and the American Orthopaedic Foot and Ankle Society (AOFAS) score. Three-tesla magnetic resonance imaging (MRI) was performed bilaterally at the ankle. Besides morphological sequences for evaluation of the syndesmosis and degenerative changes of the ankle using the Ankle Osteoarthritis Scoring System (AOSS), the MR protocol included a coronal 2-dimensional multislice multiecho sequence for quantitative cartilage T2-weighted mapping. Spearman correlations and paired t tests were used for statistical analysis.

Results:

This retrospective study included 19 consecutive patients (mean age, 29.7 ± 11.5 years) with acute isolated syndesmosis injuries treated with a suture-button system between January 2006 and June 2014, with a mean follow-up of 5.1 ± 2.6 years. Postoperatively, the median FADI score was 136 (range, 78-136), and the median AOFAS score was 100 (range, 87-100). Seventeen (89.5%) patients reported to have reached their preinjury level of sports activities. MRIs of 16 patients were obtained and all showed intact anterior and posterior syndesmotic ligaments; however, in most patients, the previously injured syndesmotic ligament was thickened compared with the uninjured ankle. Average width of the anterior (P = .81) and posterior (P = .60) syndesmosis was not significantly different between the ipsilateral (3.2 ± 1.2 and 4.4 ± 0.9 mm) and contralateral ankles (3.0 ± 0.6 and 4.2 ± 0.7 mm). The median AOSS score was 1.5 (range, 0-11) for the ipsilateral ankle and 0 (range, 0-6) for the contralateral ankle. T2 values of articular cartilage did not significantly differ between the involved and the uninjured ankle (P = .68). Five patients needed hardware removal due to persistent skin irritation, and 1 patient suffered from reinstability of the ankle resulting in revision surgery 2 years after the index surgery.

Conclusion:

Suture-button fixation is an excellent treatment for acute and isolated syndesmosis injuries, resulting in stable ankles without early or advanced osteoarthritic changes at midterm follow-up.

New Technology in Imaging Cartilage of the Ankle

The incidence of osteochondral lesions, as well as osteoarthritis of the ankle joint following osteochondritis dissecans and trauma, has been reappraised in recent years. Consequently, an increasing number of surgical interventions using different cartilage repair techniques is performed in the ankle joint, which has resulted in a growing demand for repetitive and objective assessment of cartilage tissue and its repair. While morphological imaging does enable monitoring of macroscopic changes with increasing precision, it fails to provide information about the ultrastructural composition of cartilage. The significance of molecular changes in cartilage matrix composition, however, is increasingly recognized, as it is assumed that macroscopic cartilage degeneration is preceded by a loss in glycosaminoglycans and a disorganization of the collagen network. Recent advances in biochemical magnetic resonance imaging (MRI) have yielded sequences sensitive to these changes, thus providing invaluable insight into both early cartilage degeneration and maturation of repair tissue, on a molecular level. The aim of this review was to provide a comprehensive overview of these techniques, including water and collagen-sensitive T2/T2* mapping, as well as glycosaminoglycan-sensitive sequences such as delayed gadolinium-enhanced MRI of cartilage dGEMRIC, and sodium imaging, and describe their applications for the ankle joint.

Juvenile Particulate Osteochondral Allograft for Treatment of Osteochondral Lesions of the Talus: Detection of Altered Repair Tissue Biochemical Composition Using 7 Tesla MRI and T2 Mapping

During the previous 2 decades, numerous surgical procedures have become available to treat osteochondral lesions of the talus. The objective of the present study was to use 7 Tesla (7T) magnetic resonance imaging (MRI) to quantify and compare T2 values (a marker of collagen architecture) of native tibiotalar cartilage and cartilage repair tissue in patients treated with a juvenile particulate allograft for osteochondral lesions of the talus. The institutional review board approved the present study, and all subjects provided written informed consent. We scanned the ankles of 7 cartilage repair patients using a 7T MRI scanner with a multi-echo spin-echo sequence to measure the cartilage T2 values. We assessed the cartilage T2 values in the talar repair tissue, adjacent native talar cartilage, and overlying tibial cartilage. We compared the differences between groups using the paired t test. The talar cartilage repair tissue demonstrated greater mean T2 relaxation times compared with the native adjacent talar cartilage (64.88 ± 12.23 ms versus 49.56 ± 7.82 ms; p = .043). The tibial cartilage regions overlying these talar cartilage regions demonstrated a trend toward greater T2 relaxation times (77.00 ± 31.29 ms versus 59.52 ± 7.89 ms; p = .067). 7T MRI can detect differences in T2 values in cartilage repair tissue compared with native cartilage and could be useful for monitoring the status of cartilage health after surgical intervention.

Quantitative techniques for musculoskeletal MRI at 7 Tesla

Whole-body 7 Tesla MRI scanners have been approved solely for research since they appeared on the market over 10 years ago, but may soon be approved for selected clinical neurological and musculoskeletal applications in both the EU and the United States. There has been considerable research work on musculoskeletal applications at 7 Tesla over the past decade, including techniques for ultra-high resolution morphological imaging, 3D T2 and T2* mapping, ultra-short TE applications, diffusion tensor imaging of cartilage, and several techniques for assessing proteoglycan content in cartilage. Most of this work has been done in the knee or other extremities, due to technical difficulties associated with scanning areas such as the hip and torso at 7 Tesla. In this manuscript, we first provide some technical context for 7 Tesla imaging, including challenges and potential advantages. We then review the major quantitative MRI techniques being applied to musculoskeletal applications on 7 Tesla whole-body systems.

Technical Considerations: Best Practices for MR Imaging of the Foot and Ankle

There are many challenges involved in obtaining diagnostic MR images of the foot and ankle. The complex anatomy and morphology, with curved and angular structures localized to the periphery of the body, make for an inherent challenge, let alone if an added level of complexity, such as orthopedic instrumentation, is added. This review outlines the technical considerations best designed to produce diagnostic images of the foot and ankle, with an emphasis on the postoperative state, including imaging in the presence of metal.

Clinical applications at ultrahigh field (7 T). Where does it make the difference?

Presently, three major MR vendors provide commercial 7-T units for clinical research under ethical permission, with the number of operating 7-T systems having increased to over 50. This rapid increase indicates the growing interest in ultrahigh-field MRI because of improved clinical results with regard to morphological as well as functional and metabolic capabilities. As the signal-to-noise ratio scales linearly with the field strength (B0 ) of the scanner, the most obvious application at 7 T is to obtain higher spatial resolution in the brain, musculoskeletal system and breast. Of specific clinical interest for neuro-applications is the cerebral cortex at 7 T, for the detection of changes in cortical structure as a sign of early dementia, as well as for the visualization of cortical microinfarcts and cortical plaques in multiple sclerosis. In the imaging of the hippocampus, even subfields of the internal hippocampal anatomy and pathology can be visualized with excellent resolution. The dynamic and static blood oxygenation level-dependent contrast increases linearly with the field strength, which significantly improves the pre-surgical evaluation of eloquent areas before tumor removal. Using susceptibility-weighted imaging, the plaque-vessel relationship and iron accumulation in multiple sclerosis can be visualized for the first time. Multi-nuclear clinical applications, such as sodium imaging for the evaluation of repair tissue quality after cartilage transplantation and (31) P spectroscopy for the differentiation between non-alcoholic benign liver disease and potentially progressive steatohepatitis, are only possible at ultrahigh fields. Although neuro- and musculoskeletal imaging have already demonstrated the clinical superiority of ultrahigh fields, whole-body clinical applications at 7 T are still limited, mainly because of the lack of suitable coils. The purpose of this article was therefore to review the clinical studies that have been performed thus far at 7 T, compared with 3 T, as well as those studies performed at 7 T that cannot be routinely performed at 3 T. Copyright © 2015 John Wiley & Sons, Ltd.

In vivo deformation of thin cartilage layers: Feasibility and applicability of T2* mapping

The objectives of this study were as follows: (i) to assess segmentation consistency and scan precision of T2* mapping of human tibio-talar cartilage, and (ii) to monitor changes in T2* relaxation times of ankle cartilage immediately following a clinically relevant in vivo exercise and during recovery. Using multi-echo gradient recalled echo sequences, averaged T2* values were calculated for tibio-talar cartilage layers in 10 healthy volunteers. Segmentation consistency and scan precision were determined from two repeated segmentations and two repeated acquisitions with repositioning, respectively. Subsequently, acute in vivo cartilage loading responses were monitored by calculating averaged tibio-talar T2* values at rest, immediately after (i.e., deformation) and at 15 min (i.e., recovery) following a 30-repetition knee bending exercise. Precision errors attained 4-6% with excellent segmentation consistency point estimates (i.e., intra-rater ICC of 0.95) and acceptable limits of confidence. At deformation, T2* values were increased in both layers [+16.1 (10.7)%, p = 0.004 and +17.3 (15.3)%, p = 0.023, for the talus and tibia, respectively] whereas during recovery no significant changes could be established when comparing to baseline [talar cartilage: +5.2 (8.2)%, p = 0.26 and tibial cartilage: +6.6 (10.4)%, p = 0.23]. T2* mapping is a viable method to monitor deformational behavior in thin cartilage layers such as ankle cartilage. Longitudinal changes in T2* can be reliably appraised and require at least 4-6% differences to ascertain statistical significance. The ability to detect considerable change even after non-strenuous loading events, endorses T2* mapping as an innovative method to evaluate the effects of therapeutic exercise on thin cartilage layers. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:771-778, 2016.

Clinical and MRI outcomes of HA injection following arthroscopic microfracture for osteochondral lesions of the talus

PURPOSE

The purpose of this study was to compare the clinical and magnetic resonance imaging (MRI) outcomes of arthroscopic microfracture surgery alone or in combination with hyaluronic acid (HA) injection in the treatment of osteochondral lesions of the talus.

METHODS

Thirty-five patients with osteochondral lesions of the talus who underwent arthroscopic microfracture were included and followed up for at least 9 months post-operatively. The patients were randomly divided into non-injection group (n = 17) who received treatment with microfracture surgery alone and injection group (n = 18) who also accepted intra-articular injection of HA post-operatively. Quantitative MRI was used to evaluate the cartilage repair after surgery. American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hind foot Scale scores and Visual Analogue Scale (VAS) scores were used to evaluate clinical outcomes.

RESULTS

After operation, the MRI outcomes showed that the thickness index was higher (0.8 ± 0.1 vs. 0.7 ± 0.1) and the T2 index was lower (1.2 ± 0.1 vs. 1.4 ± 0.1) in the injection group than in the non-injection group (P < 0.01). As for the volumes of subchondral bone marrow oedema, there are no significant differences between groups (n.s.). Compared with the non-injection group, the AOFAS score and the VAS score yielded a higher level of improvement in injection group at final follow-up post-operatively (P < 0.05).

CONCLUSIONS

Arthroscopic microfracture is a safe and effective procedure for osteochondral lesions of the talus. Intra-articular HA injection as an adjunct to arthroscopic microfracture might offer better functional recovery than microfracture alone.

LEVEL OF EVIDENCE

II.

Autologous Osteochondral Transplantation for Osteochondral Lesions of the Talus

BACKGROUND

Autologous osteochondral transplantation (AOT) is used to treat osteochondral lesions (OCLs) of the talus, typically reserved for lesions greater than 150 mm(2). Few studies exist examining the functional and magnetic resonance imaging (MRI) outcomes following this procedure. The purpose of this study was to investigate functional and MRI outcomes, including quantitative T2 mapping following AOT.

METHODS

Eighty-five consecutive patients who underwent AOT were identified. Functional outcomes were assessed pre- and postoperatively using the Foot and Ankle Outcome Score (FAOS). The Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) score was used to assess cartilage incorporation. Quantitative T2 MRI relaxation time of graft tissue and adjacent normal cartilage values were recorded in a subset of 61 patients. The mean clinical follow-up was 47.2 months, with mean MRI follow-up of 24.8 months.

RESULTS

Mean FAOS improved pre- to postoperatively from 50 to 81 (P < .001). The mean MOCART score was 85.8. Lesion size was negatively correlated with MOCART score (r = -0.36, P = .004). Superficial T2 values in graft tissue were higher than control tissue (42.0 vs 35.8, P < .001). Deep T2 values in graft tissue were similar to the control values (30.9 vs 30.0, P = .305). Functional outcomes were similar in patients irrespective of whether they had previous microfracture or concomitant procedures.

CONCLUSION

AOT was an effective treatment for large OCLs of the talus in the current study. MOCART scoring indicated good structural integrity of the graft. Quantitative T2 mapping suggests that graft tissue may not always mirror native hyaline cartilage. The long-term implications of this are not yet known.

LEVEL OF EVIDENCE

Level IV, case series.

Osteochondral repair with synovial membrane‑derived mesenchymal stem cells

The aim of the present study was to analyze cartilage repair tissue quality following synovial membrane-derived mesenchymal stem cell (SMSC) transplantation in a rabbit osteochondral defect. A total of 15 New Zealand white rabbits were randomly distributed into three groups (n=5 in each group). In group 1, an osteochondral defect model was established in the right knee trochlea, prior to transplantation with SMSCs (SMSC group). In group 2, an osteochondral defect model was established without further treatment (control group). Group 3 did not undergo osteochondral defect model establishment and served as the sham control (normal group). All animals were sacrificed 12 weeks following the surgical procedures for magnetic resonance imaging and histological examination. No significant differences were observed between the control and SMSC group in the macroscopic score (P>0.05), the 2D magnetic resonance observation of cartilage repair tissue score (P>0.05) or the modified O'Driscoll scale (P>0.05). Compared with the control group, a significant improvement in tissue quality was observed in the SMSCs group postoperatively. The repair tissue of the SMSCs group had a shorter T₂, compared with that of the control group, although no significant difference was detected (P>0.05). Furthermore, the apparent diffusion coefficient in the repair tissue of the SMSC group had a significantly lower value, compared with that of the control group (P=0.016). The results of the present study demonstrated that osteochondral repair using SMSCs facilitated the repair of appropriate tissue texture.

Sodium magnetic resonance imaging of ankle joint in cadaver specimens, volunteers, and patients after different cartilage repair techniques at 7 T: initial results

OBJECTIVES

The goal of cartilage repair techniques such as microfracture (MFX) or matrix-associated autologous chondrocyte transplantation (MACT) is to produce repair tissue (RT) with sufficient glycosaminoglycan (GAG) content. Sodium magnetic resonance imaging (MRI) offers a direct and noninvasive evaluation of the GAG content in native cartilage and RT. In the femoral cartilage, this method was able to distinguish between RTs produced by MFX and MACT having different GAG contents. However, it needs to be clarified whether sodium MRI can be useful for evaluating RT in thin ankle cartilage. Thus, the aims of this 7-T study were (1) to validate our sodium MRI protocol in cadaver ankle samples, (2) to evaluate the sodium corrected signal intensities (cSI) in cartilage of volunteers, (3) and to compare sodium values in RT between patients after MFX and MACT treatment.

MATERIALS AND METHODS

Five human cadaver ankle samples as well as ankles of 9 asymptomatic volunteers, 6 MFX patients and 6 MACT patients were measured in this 7-T study. Sodium values from the ankle samples were compared with histochemically evaluated GAG content. In the volunteers, sodium cSI values were calculated in the cartilages of ankle and subtalar joint. In the patients, sodium cSI in RT and reference cartilage were measured, morphological appearance of RT was evaluated using the magnetic resonance observation of cartilage repair tissue (MOCART) scoring system, and clinical outcome before and after surgery was assessed using the American Orthopaedic Foot and Ankle Society score and Modified Cincinnati Knee Scale. All regions of interest were defined on morphological images and subsequently transferred to the corresponding sodium images. Analysis of variance, t tests, and Pearson correlation coefficients were evaluated.

RESULTS

In the patients, significantly lower sodium cSI values were found in RT than in reference cartilage for the MFX (P = 0.007) and MACT patients (P = 0.008). Sodium cSI and MOCART scores in RT did not differ between the MFX and MACT patients (P = 0.185). No significant difference in sodium cSI was found between reference cartilage of the volunteers and the patients (P = 0.355). The patients showed significantly higher American Orthopaedic Foot and Ankle Society and Modified Cincinnati scores after treatment than they did before treatment. In the volunteers, sodium cSI was significantly higher in the tibial cartilage than in the talar cartilage of ankle joint (P = 0.002) and in the talar cartilage than in the calcaneal cartilage of subtalar joint (P < 0.001). Data from the cadaver ankle samples showed a strong linear relationship between the sodium values and the histochemically determined GAG content (r = 0.800; P < 0.001; R = 0.639).

CONCLUSIONS

This study demonstrates the feasibility of in vivo quantification of sodium cSI, which can be used for GAG content evaluation in thin cartilages of ankle and subtalar joints at 7 T. A strong correlation observed between the histochemically evaluated GAG content and the sodium values proved the sufficient sensitivity of sodium MRI to changes in the GAG content of cartilages in the ankle. Both MFX and MACT produced RT with lower sodium cSI and, thus, of lower quality compared with reference cartilage in the patients or in the volunteers. Our results suggest that MFX and MACT produce RT with similar GAG content and similar morphological appearance in patients with similar surgery outcome. Sodium MRI at 7 T allows a quantitative evaluation of RT quality in the ankle and may thus be useful in the noninvasive assessment of new cartilage repair procedures.

Diagnosing, planning and evaluating osteochondral ankle defects with imaging modalities

This current concepts review outlines the role of different imaging modalities in the diagnosis, preoperative planning, and follow-up of osteochondral ankle defects. An osteochondral ankle defect involves the articular cartilage and subchondral bone (usually of the talus) and is mostly caused by an ankle supination trauma. Conventional radiographs are useful as an initial imaging tool in the diagnostic process, but have only moderate sensitivity for the detection of osteochondral defects. Computed tomography (CT) and magnetic resonance imaging (MRI) are more accurate imaging modalities. Recently, ultrasonography and single photon emission CT have been described for the evaluation of osteochondral talar defects. CT is the most valuable modality for assessing the exact location and size of bony lesions. Cartilage and subchondral bone damage can be visualized using MRI, but the defect size tends to be overestimated due to bone edema. CT with the ankle in full plantar flexion has been shown a reliable tool for preoperative planning of the surgical approach. Postoperative imaging is useful for objective assessment of repair tissue or degenerative changes of the ankle joint. Plain radiography, CT and MRI have been used in outcome studies, and different scoring systems are available.

Morphological and compositional monitoring of a new cell-free cartilage repair hydrogel technology - GelrinC by MR using semi-quantitative MOCART scoring and quantitative T2 index and new zonal T2 index calculation

OBJECTIVE

To evaluate cartilage repair tissue (RT) using MOCART scoring for morphological and T2 mapping for biochemical assessment following implantation of GelrinC, a biosynthetic, biodegradable hydrogel implant.

DESIGN

MR imaging (1.5/3T) was performed on 21 patients at six sites. Standard protocols were used for MOCART evaluation at 1 week (baseline) 1, 3, 6, 12, 18 and 24 months. Multi-echo SE was used for T2 mapping. Global (T2 in RT divided by T2 in normal cartilage) and zonal T2 index (deep T2 divided by superficial T2) of RT were calculated.

RESULTS

Average MOCART score was 71.8 (95% CI 62.2 to 81.3) at six, 75.2 (95% CI 62.8 to 87.5) at twelve, 71.8 (95% CI 55.4 to 88.2) at eighteen and 84.4 (95% CI 77.7 to 91.0) at twenty-four months. The global T2 index ranged between 0.8 and 1.2 (normal healthy cartilage) in 1/11 (9%) patients at baseline, 8/12 (67%) at 12 months, 11/13 (85%) at 18 months and 13/16 (81%) at 24 months. The zonal T2 index for RT was <20% difference to the zonal T2 index for normal cartilage in: 6/12 patients (50%) at 12 months, 7/13 (53.8%) at 18 months and 10/16 (63.5%) at 24 months. The standard deviation for T2 showed a significant decrease over the study.

CONCLUSIONS

The increase of MOCART scores over follow-up indicates improving cartilage repair tissue. Global and zonal T2 repair values at 24 months reached normal cartilage in 81% and 63.5% of the patients respectively, reflecting collagen organization similar to hyaline cartilage.

T2-mapping at 3 T after microfracture in the treatment of osteochondral defects of the talus at an average follow-up of 8 years

PURPOSE

To compare repaired cartilage with native cartilage, and inter-observer reliability, using T2 mapping at 3 T for assessing cartilage repair in osteochondral defects of the talus after the microfracture technique.

METHODS

We enrolled eight females and seven males undergoing arthroscopic microfracture for osteochondral defects of the talus at an average follow-up of 7.9 ± 2.2 years (range 5-13 years). Cartilage tissue was assessed using a 3-T magnetic resonance imaging unit with an 8-channel phased array foot and ankle coil (gradient strength, 50 mT/m; slew rate, 200 T/m/s). T2 maps were then calculated. Three independent boarded specialists evaluated the images, and magnetic resonance observation of cartilage repair tissue scores was used to assess the cartilage and joint status. Clinical results were assessed using the Hannover Scoring System (HSS) for the ankle and the American Orthopaedic Foot and Ankle Society (AOFAS) hind-foot score.

RESULTS

No significant mean differences were found between the T2 properties of the repair tissue and those of the native reference cartilage (T2 = 38.6 ± 5.3 ms, range 30.2-55.8 ms vs. 40.3 ± 8.5 ms, range 31.4-59.8 ms, respectively; intra-class correlation coefficient = 0.94; confidence interval 0.84-0.99, P ≤ 0.001). Despite ≥50 % defect filling in all patients, subchondral bone changes were considerable. The HSS at the follow-up revealed a mean score of 87 ± 12 (range 51-97), and the AOFAS-Score was 90 ± 13 (range 59-100).

CONCLUSIONS

3 T T2 maps were similar in repaired and native cartilage with good inter-observer reliability.

LEVEL OF EVIDENCE

IV.

Quantitative MRI in the evaluation of articular cartilage health: reproducibility and variability with a focus on T2 mapping

PURPOSE

Early diagnosis of cartilage degeneration and longitudinal tracking of cartilage health including repair following surgical intervention would benefit from the ability to detect and monitor changes of the articular cartilage non-invasively and before gross morphological alterations appear.

METHODS

Quantitative MR imaging has shown promising results with various imaging biomarkers such as T2 mapping, T1 rho and dGEMRIC demonstrating sensitivity in the detection of biochemical alterations within tissues of interest. However, acquiring accurate and clinically valuable quantitative data has proven challenging, and the reproducibility of the quantitative mapping technique and its values are essential. Although T2 mapping has been the focus in this discussion, all quantitative mapping techniques are subject to the same issues including variability in the imaging protocol, unloading and exercise, analysis, scanner and coil, calculation methods, and segmentation and registration concerns.

RESULTS

The causes for variability between time points longitudinally in a patient, among patients, and among centres need to be understood further and the issues addressed.

CONCLUSIONS

The potential clinical applications of quantitative mapping are vast, but, before the clinical community can take full advantage of this tool, it must be automated, standardized, validated, and have proven reproducibility prior to its implementation into the standard clinical care routine.

Cartilage repair surgery: outcome evaluation by using noninvasive cartilage biomarkers based on quantitative MRI techniques?

BACKGROUND

New quantitative magnetic resonance imaging (MRI) techniques are increasingly applied as outcome measures after cartilage repair.

OBJECTIVE

To review the current literature on the use of quantitative MRI biomarkers for evaluation of cartilage repair at the knee and ankle.

METHODS

Using PubMed literature research, studies on biochemical, quantitative MR imaging of cartilage repair were identified and reviewed.

RESULTS

Quantitative MR biomarkers detect early degeneration of articular cartilage, mainly represented by an increasing water content, collagen disruption, and proteoglycan loss. Recently, feasibility of biochemical MR imaging of cartilage repair tissue and surrounding cartilage was demonstrated. Ultrastructural properties of the tissue after different repair procedures resulted in differences in imaging characteristics. T2 mapping, T1rho mapping, delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), and diffusion weighted imaging (DWI) are applicable on most clinical 1.5 T and 3 T MR scanners. Currently, a standard of reference is difficult to define and knowledge is limited concerning correlation of clinical and MR findings. The lack of histological correlations complicates the identification of the exact tissue composition.

CONCLUSIONS

A multimodal approach combining several quantitative MRI techniques in addition to morphological and clinical evaluation might be promising. Further investigations are required to demonstrate the potential for outcome evaluation after cartilage repair.