Subregional Anatomical Distribution of T2 Values of Articular Cartilage in Asymptomatic Hips

Augmentation of ACL Autograft Reconstruction With an Amnion Collagen Matrix Wrap and Bone Marrow Aspirate Concentrate: A Pilot Randomized Controlled Trial With 2-Year Follow-up

Background

It is theorized that the lack of a synovial lining after anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) contributes to slow ligamentization and possible graft failure. Whether graft maturation and incorporation can be improved with the use of a scaffold requires investigation.

Purpose

To evaluate the safety and efficacy of wrapping an ACL autograft with an amnion collagen matrix and injecting bone marrow aspirate concentrate (BMAC), quantify the cellular content of the BMAC samples, and assess 2-year postoperative patient-reported outcomes.

Study Design

Randomized controlled trial; Level of evidence, 2.

Methods

A total of 40 patients aged 18 to 35 years who were scheduled to undergo ACLR were enrolled in a prospective single-blinded randomized controlled trial with 2 arms based on graft type: bone-patellar tendon-bone (BTB; n = 20) or hamstring (HS; n = 20). Participants in each arm were randomized into a control group who underwent standard ACLR or an intervention group who had their grafts wrapped with an amnion collagen matrix during graft preparation, after which BMAC was injected under the wrap layers after implantation. Postoperative magnetic resonance imaging (MRI) mapping/processing yielded mean T2* relaxation time and graft volume values at 3, 6, 9, and 12 months. Participants completed the Single Assessment Numeric Evaluation Score, Knee injury and Osteoarthritis Outcome Score, and pain visual analog scale. Statistical linear mixed-effects models were used to quantify the effects over time and the differences between the control and intervention groups. Adverse events were also recorded.

Results

No significant differences were found at any time point between the intervention and control groups for BTB T2* (95% CI, -1.89 to 0.63; P = .31), BTB graft volume (95% CI, -606 to 876.1; P = .71), HS T2* (95% CI, -2.17 to 0.39; P = .162), or HS graft volume (95% CI, -11,141.1 to 351.5; P = .28). No significant differences were observed between the intervention and control groups of either graft type on any patient-reported outcome measure. No adverse events were reported after a 2-year follow-up.

Conclusion

In this pilot study, wrapping a graft with an amnion collagen matrix and injecting BMAC appeared safe. MRI T2* values and graft volume of the augmented ACL graft were not significantly different from that of controls, suggesting that the intervention did not result in improved graft maturation.

Registration

NCT03294759 (ClinicalTrials.gov identifier).

Compositional MRI of the Hip: Reproducibility, Effect of Joint Unloading, and Comparison of T2 Relaxometry with Delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage

OBJECTIVE

Our aim was to compare T2 with delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) in the hip and assess the reproducibility and effect of joint unloading on T2 mapping.

DESIGN

Ten individuals at high risk of developing hip osteoarthritis (SibKids) underwent contemporaneous T2 mapping and dGEMRIC in the hip (10 hips). Twelve healthy volunteers underwent T2 mapping of both hips (24 hips) at time points 25, 35, 45, and 55 minutes post offloading. Acetabular and femoral cartilage was manually segmented into regions of interest. The relationship between T2 and dGEMRIC values from anatomically corresponding regions of interests was quantified using Pearson's correlation. The reproducibility of image analysis for T2 and dGEMRIC, and reproducibility of image acquisition for T2, was quantified using the intraclass correlation coefficient (ICC), root mean square coefficient of variance (RMSCoV), smallest detectable difference (SDD), and Bland-Altman plots. The paired t test was used to determine if difference existed in T2 values at different unloading times.

RESULTS

T2 values correlated most strongly with dGEMRIC values in diseased cartilage (r = -0.61, P = <0.001). T2 image analysis (segmentation) reproducibility was ICC = 0.96 to 0.98, RMSCoV = 3.5% to 5.2%, and SDD = 2.2 to 3.5 ms. T2 values at 25 minutes unloading were not significantly different to longer unloading times (P = 0.132). SDD for T2 image acquisition reproducibility was 7.1 to 7.4 ms.

CONCLUSIONS

T2 values in the hip correlate well with dGEMRIC in areas of cartilage damage. T2 shows high reproducibility and values do not change beyond 25 minutes of joint unloading.

Automated analysis of immediate reliability of T2 and T2* relaxation times of hip joint cartilage from 3 T MR examinations

BACKGROUND

Magnetic resonance (MR) T2 and T2* mapping sequences allow in vivo quantification of biochemical characteristics within joint cartilage of relevance to clinical assessment of conditions such as hip osteoarthritis (OA).

PURPOSE

To evaluate an automated immediate reliability analysis of T2 and T2* mapping from MR examinations of hip joint cartilage using a bone and cartilage segmentation pipeline based around focused shape modelling.

STUDY TYPE

Technical validation.

SUBJECTS

17 asymptomatic volunteers (M: F 7:10, aged 22-47 years, mass 50-90 kg, height 163-189 cm) underwent unilateral hip joint MR examinations. Automated analysis of cartilage T2 and T2* data immediate reliability was evaluated in 9 subjects (M: F 4: 5) for each sequence.

FIELD STRENGTH/SEQUENCE

A 3 T MR system with a body matrix flex-coil was used to acquire images with the following sequences: T2 weighted 3D-trueFast Imaging with Steady-State Precession (water excitation; 10.18 ms repetition time (TR); 4.3 ms echo time (TE); Voxel Size (VS): 0.625 × 0.625 × 0.65 mm; 160 mm field of view (FOV); Flip Angle (FA): 30 degrees; Pixel Bandwidth (PB): 140 Hz/pixel); a multi-echo spin echo (MESE) T2 mapping sequence (TR/TE: 2080/18-90 ms (5 echoes); VS: 4 × 0.78 × 0.78 mm; FOV: 200 mm; FA: 180 degrees; PB: 230 Hz/pixel) and a MESE T2* mapping sequence (TR/TE: 873/3.82-19.1 ms (5 echoes); VS: 3 × 0.625 × 0.625 mm; FOV: 160 mm; FA: 25 degrees; PB: 250 Hz/pixel).

ASSESSMENT

Automated cartilage segmentation and quantitative analysis provided T2 and T2* data from test-retest MR examinations to assess immediate reliability.

STATISTICAL TESTS

Coefficient of variation (CV) and intraclass correlations (ICC_{2, 1}) to analyse automated T2 and T2* mapping reliability focusing on the clinically important superior cartilage regions of the hip joint.

RESULTS

Comparisons between test-retest T2 and (T2*) data revealed mean CV's of 3.385% (1.25%), mean ICC_{2, 1}'s of 0.871 (0.984) and median mean differences of -1.139ms (+0.195ms).

CONCLUSION

The T2 and T2* times from automated analyses of hip cartilage from test-retest MR examinations had high (T2) and excellent (T2*) immediate reliability.

3-T MRI mapping is a valid in vivo method of quantitatively evaluating the anterior cruciate ligament: rater reliability and comparison across age

OBJECTIVE

As biologic augmentation methods emerge, objective measures of soft tissues are necessary for developmental study. The purpose of this study was to develop a quantitative MRI mapping protocol for the ACL. The objectives were (1) to provide age-based T2 relaxation, T2* relaxation, and volume values in healthy individuals, (2) to establish the intra-rater and inter-rater reliability of ACL mapping, and (3) to determine whether 3-T or 7-T MRI is more appropriate for future clinical trials.

MATERIALS AND METHODS

Thirty healthy participants, aged 18-62, asymptomatic for knee pathology and without history of knee injury underwent both a 3-T and 7-T MRI. Manual image mapping of the anterior cruciate ligament was performed by two observers and processed to obtain T2, T2*, and volume values. Analysis of variance and two-way random effects model were used to calculate statistical significance and intraclass correlation coefficients.

RESULTS

Across all participants, 3-T and 7-T mean T2, T2* and volume values were 37.1 ± 7.9 and 39.7 ± 6.2 ms (p = 0.124), 10.9 ± 1.3 and 10.9 ± 0.9 ms (p = 0.981), and 2380 ± 602 and 2484 ± 736 mm³ (p = 0.551), respectively. The T2, T2*, and volume did not vary between age cohorts (p > 0.05). Excellent inter-rater and intra-rater reliability regarding T2 and T2* values was found. While ACL volume exhibited good inter-rater reliability and excellent intra-rater reliability.

CONCLUSIONS

T2 relaxation values and ACL volume do not vary with age and therefore can be used as a quantifiable, non-invasive method to assess ACL graft maturation. 7-T MRI analysis was not superior to 3-T MRI analysis, suggesting that 3-T MRI is practical and capable for future comparative studies.

Automatic Cartilage Segmentation for Delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Hip Joint Cartilage: A Feasibility Study

OBJECTIVE

Automatic segmentation for biochemical cartilage evaluation holds promise for an efficient and reader-independent analysis. This pilot study aims to investigate the feasibility and to compare delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) hip joint assessment with manual segmentation of acetabular and femoral head cartilage and dGEMRIC hip joint assessment using automatic surface and volume processing software at 3 Tesla.

DESIGN

Three-dimensional (3D) dGEMRIC data sets of 6 patients with hip-related pathology were assessed (1) manually including multiplanar image reformatting and regions of interest (ROI) analysis and (2) automated by using a combined surface and volume processing software. For both techniques, T1_Gd values were obtained in acetabular and femoral head cartilage at 7 regions (anterior, anterior-superior, superior-anterior, superior, superior-posterior, posterior-superior, and posterior) in central and peripheral portions. Correlation between both techniques was calculated utilizing Spearman's rank correlation coefficient.

RESULTS

A high correlation between both techniques was observed for acetabular (ρ = 0.897; P < 0.001) and femoral head (ρ = 0.894; P < 0.001) cartilage in all analyzed regions of the hip joint (ρ between 0.755 and 0.955; P < 0.001).

CONCLUSIONS

Automatic cartilage segmentation with dGEMRIC assessment for hip joint cartilage evaluation seems feasible providing high to excellent correlation with manually performed ROI analysis. This technique is feasible for an objective, reader-independant and reliable assessment of biochemical cartilage status.

Do dGEMRIC and T2 Imaging Correlate With Histologic Cartilage Degeneration in an Experimental Ovine FAI Model?

BACKGROUND

Biochemical MRI of hip cartilage such as delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) and T2 mapping is increasingly used to judge cartilage quality in the assessment of femoroacetabular impingement (FAI). The current evidence is sparse about which of these techniques yields a stronger correlation with histologic cartilage degeneration because of the difficulty in validating biochemical MRI techniques against histology in the clinical setting. Recently, an experimental ovine FAI model was established that induces chondrolabral damage and offers a validated platform to address these limitations.

QUESTIONS/PURPOSES

In a sheep model, we asked: (1) Do dGEMRIC and/or T2 values of acetabular and femoral cartilage correlate with histologic cartilage degeneration as assessed with the Mankin score? (2) Do simultaneously measured dGEMRIC and T2 values correlate in an experimental ovine FAI model?

METHODS

We performed an experimental pilot study on five female Swiss Alpine sheep (10 hips) that underwent postmortem MRI, including biochemical cartilage sequences, after a staged FAI correction had been performed on one side. No surgery was performed on the contralateral side, which served as a healthy control. In these sheep, an extraarticular intertrochanteric varus osteotomy was performed to rotate the naturally aspherical ovine femoral head into the acetabulum to induce cam-type FAI and chondrolabral damage comparable to human beings. After a 70-day ambulation period, femoral osteochondroplasty was performed and all sheep were euthanized after a total observation period of 210 days. Before they were euthanized, the sheep received a contrast agent and roamed and walked for at least 45 minutes. Hips were prepared to fit in a knee coil and MRI was performed at 3 T including a three-dimensional (3-D) dGEMRIC sequence, a two-dimensional (2-D) radial T2 mapping sequence, and a 2-D radial proton density-weighted sequence for morphologic cartilage assessment. Using specifically developed software, the 3-D dGEMRIC images and T2 maps were coregistered on the 2-D morphologic radial images. This enabled us to simultaneously measure dGEMRIC and T2 values using the identical regions of interest. dGEMRIC and T2 values of the acetabular and femoral cartilage were measured circumferentially using anatomic landmarks. After MRI, bone-cartilage samples were taken from the acetabulum and the femur and stained with toluidine blue for assessment of the histologic cartilage degeneration using the Mankin score, which was assessed in consensus by two observers. Spearman's rank correlation coefficient was used to (1) correlate dGEMRIC values and T2 values with the histologic Mankin score of femoroacetabular cartilage; and to (2) correlate dGEMRIC values and T2 values of femoroacetabular cartilage.

RESULTS

A moderate to fair correlation between overall dGEMRIC values of the acetabular cartilage (R = -0.430; p = 0.003) and the femoral cartilage (R = -0.334; p = 0.003) versus the histologic Mankin score was found. A moderate correlation (R = -0.515; p = 0.010) was found among peripheral dGEMRIC values of the acetabulum, the superior femoral cartilage (R = -0.500; p = 0.034), and the histologic Mankin score, respectively. No correlation between overall and regional femoroacetabular T2 values and the histologic Mankin scores was found. No correlation between overall and regional femoroacetabular dGEMRIC values and T2 values was found.

CONCLUSIONS

In this recently established sheep model, we found dGEMRIC values correlated well with histologic evidence of cartilage degeneration in the hip. This combination of a robust animal model and an accurate imaging technique appears to offer a noninvasive means to study the natural course of FAI and to compare the effectiveness of potential surgical options to treat it.

CLINICAL RELEVANCE

This translational study supports the continuing use of dGEMRIC as a biomarker for prearthritic cartilage degeneration with the ultimate goal to identify patients who will benefit most from corrective FAI surgery. The value of T2 imaging of hip cartilage warrants further investigation.

Factors increasing risk of failure following hip arthroscopy: a case control study

We aimed to identify factors such as pre-arthroscopy and intra-operative variables that were associated with failure of hip arthroscopy as a joint preserving operation. We performed a retrospective analysis of a database containing 344 consecutive hip arthroscopies performed at our institution. Forty-four hips were identified that underwent a subsequent arthroplasty procedure following their hip arthroscopy (cases). Sixty-six control hips (hip arthroscopy with no subsequent arthroplasty) were randomly selected from the same database. Cases and controls were matched for age, sex and follow-up (P = 0.59, 0.48, 0.10, respectively). Pre-operative radiographs/MRI scans plus intra-operative findings were analysed to identify factors associated with failure. Both a lower centre edge angle and higher acetabular index on pre-operative radiographs were associated with higher rates of failure (P < 0.001). The presence of any acetabular wear at operation was also associated with failure (P < 0.001). Highest rates of failure were seen in hips with both features of dysplasia on pre-operative radiographs and any intra-operative acetabular wear (relative risk: 5, odds ratio: 9.13, P < 0.001). Dysplastic features on pre-operative radiographs and the finding of acetabular wear at hip arthroscopy increase the risk of subsequent arthroplasty. Identification of these features pre-operatively with evolving imaging techniques would improve the results of hip arthroscopy as joint preserving surgery.

Both 3-T dGEMRIC and Acetabular-Femoral T2 Difference May Detect Cartilage Damage at the Chondrolabral Junction

BACKGROUND

In addition to case reports of gadolinium-related toxicities, there are increasing theoretical concerns about the use of gadolinium for MR imaging. As a result, there is increasing interest in noncontrast imaging techniques for biochemical cartilage assessment. Among them, T2 mapping holds promise because of its simplicity, but its biophysical interpretation has been controversial.

QUESTIONS/PURPOSES

We sought to determine whether (1) 3-T delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) and T2 mapping are both capable of detecting cartilage damage at the chondrolabral junction in patients with femoroacetabular impingement (FAI); and (2) whether there is a correlation between these two techniques for acetabular and femoral head cartilage assessment.

METHODS

Thirty-one patients with hip-related symptoms resulting from FAI underwent a preoperative 3-T MRI of their hip that included dGEMRIC and T2 mapping (symptomatic group, 16 women, 15 men; mean age, 27 ± 8 years). Ten volunteers with no symptoms according to the WOMAC served as a control (asymptomatic group, seven women, three men; mean age, 28 ± 3 years). After morphologic cartilage assessment, acetabular and femoral head cartilages were graded according to the modified Outerbridge grading criteria. In the midsagittal plane, single-observer analyses of precontrast T1 values (volunteers), the dGEMRIC index (T1_Gd, patients), and T2 mapping values (everyone) were compared in acetabular and corresponding femoral head cartilage at the chondrolabral junction of each hip by region-of-interest analysis.

RESULTS

In the symptomatic group, T1_Gd and T2 values were lower in the acetabular cartilage compared with corresponding femoral head cartilage (T1_Gd: 515 ± 165 ms versus 650 ± 191 ms, p < 0.001; T2: 39 ± 8 ms versus 46 ± 10 ms, p < 0.001). In contrast, the asymptomatic group demonstrated no differences in T1 and T2 values for the acetabular and femoral cartilages with the numbers available (T1: 861 ± 130 ms versus 860 ± 182 ms, p = 0.98; T2: 43 ± 7 ms versus 42 ± 6 ms, p = 0.73). No correlation with the numbers available was noted between the modified Outerbridge grade and T1, T1_Gd, or T2 as well as between T2 and either T1 or T1_Gd.

CONCLUSIONS

Without the need for contrast media application, T2 mapping may be a viable alternative to dGEMRIC when assessing hip cartilage at the chondrolabral junction. However, acquisition-related phenomena as well as regional variations in the microstructure of hip cartilage necessitate an internal femoral head cartilage control when interpreting these results.

LEVEL OF EVIDENCE

Level IV, diagnostic study.

Predictive Value of 3-T Magnetic Resonance Imaging in Diagnosing Grade 3 and 4 Chondral Lesions in the Hip

PURPOSE

To assess the diagnostic capability and predictive value of 3-T magnetic resonance imaging (MRI) in detecting grade 3 and 4 cartilage lesions in the hip.

METHODS

From August 2010 to April 2015, patients who underwent 3-T MRI and hip arthroscopy were included in the study. Data were prospectively collected and retrospectively reviewed. A radiologist prospectively documented MRI findings, and the surgeon documented cartilage damage at arthroscopy using the Outerbridge grading system. Arthroscopy was considered the diagnostic gold standard. This study was approved by the institutional review board.

RESULTS

The study group comprised 606 patients, with 354 men (58%) and 252 women (42%). The mean patient age was 34 years (range, 18 to 71 years). For femoral head defects, the sensitivity was 61% (95% confidence interval [CI], 53% to 68%), specificity was 58% (95% CI, 55% to 62%), positive predictive value was 29% (95% CI, 25% to 33%), and negative predictive value was 84% (95% CI, 81% to 87%). For chondral defects of the acetabulum, the sensitivity was 80% (95% CI, 75% to 84%), specificity was 41% (95% CI, 38% to 44%), positive predictive value was 42% (95% CI, 39% to 45%), and negative predictive value was 79% (95% CI, 74% to 84%).

CONCLUSIONS

The results of this study showed that 3-T MRI had sensitivity, as well as specificity, for identifying chondral defects that is similar to what has been previously reported. MRI showed increased sensitivity when identifying acetabular defects compared with femoral head defects. With a low positive predictive value, MRI may be most useful in ruling out cartilage lesions.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Prospective In Vivo Comparison of Damaged and Healthy-Appearing Articular Cartilage Specimens in Patients With Femoroacetabular Impingement: Comparison of T2 Mapping, Histologic Endpoints, and Arthroscopic Grading

PURPOSE

To describe T2 mapping values in arthroscopically determined International Cartilage Repair Society (ICRS) grades in damaged and healthy-appearing articular cartilage waste specimens from arthroscopic femoroacetabular impingement (FAI) treatment. Furthermore, we sought to compare ICRS grades of the specimens with biochemical, immunohistochemistry and histologic endpoints and assess correlations with T2 mapping.

METHODS

Twenty-four patients were prospectively enrolled, consecutively, between December 2011 and August 2012. Patients were included if they were aged 18 years or older and met criteria that followed the clinical indications for arthroscopy to treat FAI. Patients with prior hip trauma including fracture or dislocation or who have undergone prior hip surgery were excluded. All patients received a preoperative sagittal T2 mapping scan of the hip joint. Cartilage was graded intraoperatively using the ICRS grading system, and graded specimens were collected as cartilage waste for histologic, biochemical, and immunohistochemistry analysis.

RESULTS

Forty-four cartilage specimens (22 healthy-appearing, 22 damaged) were analyzed. Median T2 values were significantly higher among damaged specimens (55.7 ± 14.9 ms) than healthy-appearing specimens (49.3 ± 12.3 ms; P = .043), which was most exaggerated among mild (grade 1 or 2) defects where the damaged specimens (58.1 ± 16.4 ms) were significantly higher than their paired healthy-appearing specimens (48.7 ± 15.4 ms; P = .026). Severely damaged specimens (grade 3 or 4) had significantly lower cumulative H&E than their paired healthy-appearing counterparts (P = .02) but was not statistically significant among damaged specimens with mild (grade 1 or 2) defects (P = .198). Among healthy-appearing specimens, median T2 and the percentage of collagen fibers oriented parallel were significantly correlated (rho = 0.425, P = .048).

CONCLUSIONS

This study outlines the potential for T2 mapping to identify early cartilage degeneration in patients undergoing arthroscopy to treat FAI. Findings in ICRS grade 1 and 2 degeneration corresponded to an increase in T2 values. Further biochemical evaluation revealed a significant difference between healthy-appearing cartilage and late degeneration in cumulative H&E as well as significantly lower percentage of collagen fibers oriented parallel and a higher percentage of collagen fibers oriented randomly when considering all grades of cartilage damage.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

Comparison of T2 Values in the Lateral and Medial Portions of the Weight-Bearing Cartilage of the Hip for Patients With Symptomatic Femoroacetabular Impingement and Asymptomatic Volunteers

PURPOSE

To develop a simplified method to define a clinically relevant subregion in the course of arthroscopic treatment of femoroacetabular impingement (FAI) using T2 mapping in patients and asymptomatic volunteers. Additionally, we sought to compare the lateral and medial subregion values in asymptomatic volunteers and in patients presenting with FAI. Finally, we wanted to investigate possible associations between patients' T2 mapping values and demographic variables-i.e., alpha angle, age, sex, and body mass index (BMI).

METHODS

Twenty-five asymptomatic volunteers and 23 consecutive symptomatic patients with FAI (cam or mixed type) were prospectively enrolled and evaluated with a sagittal T2 mapping sequence. The weight-bearing region of the acetabular and femoral cartilage was manually segmented and divided into medial and lateral subregions. Median T2 values were determined, and patient characteristics were assessed as potential predictors of T2 values.

RESULTS

T2 values in the lateral portion of the acetabulum were lower than in the medial portion for both asymptomatic volunteers (43 v 53 ms; P < .001) and patients with FAI (42 v 49 ms; P = .016). The medial acetabulum (MA) of asymptomatic volunteers had higher T2 values than those of the FAI group (53 v 49 ms; P = .040). The lateral-minus-medial difference was significantly larger among asymptomatic volunteers than in patients with FAI (P = .047). Patients with FAI had higher alpha angles than those of the asymptomatic volunteers, but no other associations with patient characteristics were observed.

CONCLUSIONS

This study's findings suggest that there are differences in cartilage T2 mapping values between medial and lateral weight-bearing aspects of the hip and may expand the application and usefulness of biochemical magnetic resonance imaging (MRI) techniques, specifically T2 mapping, in the diagnosis of hip cartilage damage with the evaluation of clinically relevant subregions. When comparing asymptomatic volunteers and patients with FAI presenting with cam or mixed type deformity, we observed a significant contrast between the T2 mapping values of the lateral and medial portions of the weight-bearing zone of the acetabular cartilage, whereas such contrast was not observed when zone 3 was analyzed as a whole.

LEVEL OF EVIDENCE

Level III, development of diagnostic criteria on the basis of consecutive patients with a universally applied reference gold standard.