Does periacetabular osteotomy for hip dysplasia modulate cartilage biochemistry?

BACKGROUND: The aim of periacetabular osteotomy is to improve joint mechanics in patients with developmental dysplasia of the hip. In our study, we tried to determine whether the proteoglycan content, as measured with delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC), can be modulated with the alteration of the hip joint biomechanics. METHODS: In this prospective cohort study, thirty-seven patients (thirty-seven hips) with no or minimal osteoarthritis were treated with periacetabular osteotomy for symptomatic acetabular dysplasia. All patients had preoperative and one-year follow-up dGEMRIC scans. Twenty-eight of the thirty-seven also had two-year scans. The changes in dGEMRIC findings and hip morphology between the preoperative visit and the examinations at one and two years following the periacetabular osteotomy were assessed. RESULTS: The mean preoperative dGEMRIC index (and standard deviation) was 561.6 ± 117.6 ms; this decreased to 515.2 ± 118.4 ms at one year after periacetabular osteotomy but subsequently recovered to 529.2 ± 99.1 ms at two years postoperatively. The decrease in the dGEMRIC index of the acetabular cartilage after surgery appears to be most pronounced at the superior aspect of the acetabulum, where the decrease in mechanical loading after periacetabular osteotomy would be most pronounced. All domains of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) demonstrated significant improvement from the preoperative to the postoperative visits (all p < 0.001). CONCLUSIONS: Periacetabular osteotomy for developmental dysplasia of the hip appears to alter the mechanical loading of articular cartilage in the hip, which in turn alters the cartilage matrix composition, as demonstrated by dGEMRIC.

Femoral morphology and epiphyseal growth plate changes of the hip during maturation: MR assessments in a 1-year follow-up on a cross-sectional asymptomatic cohort in the age range of 9-17 years.

OBJECTIVES: The goal of this prospective study was to characterize the morphology and physeal changes of the femoral head during maturation using MRI in a population-based group of asymptomatic volunteers. MATERIALS AND METHODS: Sixty-four pupils (127 hips) of 331 pupils from a primary and high school were asked to take part in this study and were willing to participate. 3T MRI of the hip was obtained at baseline and 1-year follow-up. With these images, we analyzed the femoral morphology and epiphyseal changes related to age, status of the physis, and location on the femur. RESULTS: The radius of the femoral head and neck increased with age, as expected, (p < 0.001). The epiphyseal extension increased significantly with age (p < 0.05), but epiphyseal tilt and alpha angle showed no differences (p > 0.05). Building groups by using the epiphyseal status, we found that the epiphyseal extension had the highest changes in the "open" group and almost stopped in the "closed" group. The tilt angle did not change significantly (p > 0.05). Significant smaller alpha-angles were found in the "closed" group, however, these were in a normal range in all of them. Correlated to the position, the highest alpha-angle values were located in anterior-superior and superior-anterior position. CONCLUSIONS: Our data can be used as normative values, which can be compared to patients or cohorts with certain risk factors (e.g., professional athletes), this will offer the chance to detect and understand pathological changes.

T2 star relaxation times for assessment of articular cartilage at 3 T: a feasibility study.

PURPOSE: T2 mapping techniques use the relaxation constant as an indirect marker of cartilage structure, and the relaxation constant has also been shown to be a sensitive parameter for cartilage evaluation. As a possible additional robust biomarker, T2* relaxation time is a potential, clinically feasible parameter for the biochemical evaluation of articular cartilage. MATERIALS AND METHODS: The knees of 15 healthy volunteers and 15 patients after microfracture therapy (MFX) were evaluated with a multi-echo spin-echo T2 mapping technique and a multi-echo gradient-echo T2* mapping sequence at 3.0 Tesla MRI. Inline maps, using a log-linear least squares fitting method, were assessed with respect to the zonal dependency of T2 and T2* relaxation for the deep and superficial regions of healthy articular cartilage and cartilage repair tissue. RESULTS: There was a statistically significant correlation between T2 and T2* values. Both parameters demonstrated similar spatial dependency, with longer values measured toward the articular surface for healthy articular cartilage. No spatial variation was observed for cartilage repair tissue after MFX. CONCLUSIONS: Within this feasibility study, both T2 and T2* relaxation parameters demonstrated a similar response in the assessment of articular cartilage and cartilage repair tissue. The potential advantages of T2*-mapping of cartilage include faster imaging times and the opportunity for 3D acquisitions, thereby providing greater spatial resolution and complete coverage of the articular surface.

Quantitative T2 evaluation at 3.0T compared to morphological grading of the lumbar intervertebral disc: a standardized evaluation approach in patients with low back pain.

BACKGROUND: The purpose of our investigation was to compare quantitative T2 relaxation time measurement evaluation of lumbar intervertebral discs with morphological grading in young to middle-aged patients with low back pain, using a standardized region-of-interest evaluation approach. PATIENTS AND METHODS: Three hundred thirty lumbar discs from 66 patients (mean age, 39 years) with low back pain were examined on a 3.0T MR unit. Sagittal T1-FSE, sagittal, coronal, and axial T2-weighted FSE for morphological MRI, as well as a multi-echo spin-echo sequence for T2 mapping, were performed. Morphologically, all discs were classified according to Pfirrmann et al. Equally sized rectangular regions of interest (ROIs) for the annulus fibrosus were selected anteriorly and posteriorly in the outermost 20% of the disc. The space between was defined as the nucleus pulposus. To assess the reproducibility of this evaluation, inter- and intraobserver statistics were performed. RESULTS: The Pfirrmann scoring of 330 discs showed the following results: grade I: six discs (1.8%); grade II: 189 (57.3%); grade III: 96 (29.1%); grade IV: 38 (11.5%); and grade V: one (0.3%). The mean T2 values (in milliseconds) for the anterior and the posterior annulus, and the nucleus pulposus for the respective Pfirrmann groups were: I: 57/30/239; II: 44/67/129; III: 42/51/82; and IV: 42/44/56. The nucleus pulposus T2 values showed a stepwise decrease from Pfirrmann grade I to IV. The posterior annulus showed the highest T2 values in Pfirrmann group II, while the anterior annulus showed relatively constant T2 values in all Pfirrmann groups. The inter- and intraobserver analysis yielded intraclass correlation coefficients (ICC) for average measures in a range from 0.82 (anterior annulus) to 0.99 (nucleus). CONCLUSIONS: Our standardized method of region-specific quantitative T2 relaxation time evaluation seems to be able to characterize different degrees of disc degeneration quantitatively. The reproducibility of our ROI measurements is sufficient to encourage the use of this method in future investigations, particularly for longitudinal studies.

Effects of B1 inhomogeneity correction for three-dimensional variable flip angle T1 measurements in hip dGEMRIC at 3 T and 1.5 T.

Delayed gadolinium-enhanced MRI of cartilage is a technique for studying the development of osteoarthritis using quantitative T(1) measurements. Three-dimensional variable flip angle is a promising method for performing such measurements rapidly, by using two successive spoiled gradient echo sequences with different excitation pulse flip angles. However, the three-dimensional variable flip angle method is very sensitive to inhomogeneities in the transmitted B(1) field in vivo. In this study, a method for correcting for such inhomogeneities, using an additional B(1) mapping spin-echo sequence, was evaluated. Phantom studies concluded that three-dimensional variable flip angle with B(1) correction calculates accurate T(1) values also in areas with high B(1) deviation. Retrospective analysis of in vivo hip delayed gadolinium-enhanced MRI of cartilage data from 40 subjects showed the difference between three-dimensional variable flip angle with and without B(1) correction to be generally two to three times higher at 3 T than at 1.5 T. In conclusion, the B(1) variations should always be taken into account, both at 1.5 T and at 3 T.

Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) in Femoacetabular impingement.

Femoroacetabular impingement is a well-described pre-arthritic condition with two main types; cam and pincer. Studies using the open treatment for impingement have described patterns of articular cartilage wear specific to cam and pincer impingement. Assessing articular damage in the hip joint is an important component of treatment. Intravenous gadolidium allows radiologists to perform an indirect assessment of articular cartilage glycosaminoglycan (GAG) content by using a technique called dGEMRIC. Using this indirect assessment of articular cartilage, we compared the dGEMRIC indices in a group of six cam and seven pincer patients to a control group (n = 12) of asymptomatic controls that had no plain MRI findings of osteoarthritis. The superior portion of the hip joint was divided into seven regions from 9 to 3 o'clock. These regions were then subdivided into peripheral and central regions. The cam and pincer groups both had statistically lower dGEMRIC values compared to the control group. The cam group demonstrated not only peripheral but also central involvement of the joint and this was concentrated in the anterior portion of the joint. The pincer group exhibited more global hip involvement with all areas of the hip averaging a dGEMRIC index 28% less than controls. With the use of dGEMRIC more specific patterns of cartilage wear can be elicited in patients with impingement, which may improve patient selection and help better understand the progression of osteoarthithis throughout the hip joint.

Assessment of early cartilage degeneration after slipped capital femoral epiphysis using T2 and T2* mapping.

BACKGROUND: T2 and T2* mapping are novel tools to assess cartilage quality. PURPOSE: To evaluate hip cartilage quality in the long-term follow-up of patients with slipped capital femoral epiphysis (SCFE) with T2 and T2* mapping. MATERIAL AND METHODS: Thirty-three patients (19 men, 14 women, mean age 24 ± 6.0 years, range 18-51 years) with a history of SCFE in 41 hips and 10 healthy controls (seven men, mean age 22 ± 4 years) were included. Follow-up period was 12 ± 6 (range 4-39 years) years. Coronal T2 and T2* mapping were performed on a 1.5 T scanner. T2 and T2* values of the hip articular cartilage were determined in the medial, central, and lateral portion of the hip within the weight bearing zone. Clinical symptoms including pain were assessed with the Harris hip score. Statistical analysis was performed using Mann-Whitney U test and Spearman rank sum test. RESULTS: In hips after SCFE T2 (central portion: 25.71 ms ± 4.84 ms vs. 29.71 ms ± 7.04 ms, p<0.05) and T2* (central portion: 20.76 ms ± 3.17 ms vs. 23.06 ms ± 2.68 ms, P<0.01) of cartilage were significantly lower, compared to controls. The differences were most apparent in the lateral portion of the hip articular cartilage. Abnormal cartilage T2 and T2* were not associated with hip pain or impaired hip function. SCFE was unilateral in 23 cases (70%). In the patients' unaffected hips without SCFE, areas of significantly reduced T2 (central portion: 26.07 ms ± 4.27 ms, P<0.05) and T2* (lateral portion: 23.23 ms ± 2.45 vs. 25.11 ms ± 3.01 ms, P<0.05) were noted. CONCLUSION: T2 and T2* mapping of the hip in patients after SCFE are significantly different from healthy controls and may offer additional information about cartilage quality.

Comparison of pre-operative dGEMRIC imaging with intra-operative findings in femoroacetabular impingement: preliminary findings.

OBJECTIVES: To study standard MRI and dGEMRIC in patients with symptomatic FAI undergoing surgical intervention and compare them with intra-operative findings to see if they were corroborative. METHODS: Sixteen patients with symptomatic FAI that warranted surgical intervention were prospectively studied. All patients underwent plain radiographic series for FAI assessment followed by standard MRI and dGEMRIC. Subsequently, patients were surgically treated with safe dislocation and the joint was evaluated for any macroscopic signs of damaged cartilage. Data were statistically analyzed. RESULTS: A total of 224 zones in 16 patients were evaluated. One hundred and sixteen zones were intra-operatively rated as normal with mean T1 values of 510.1 ms ± 141.2 ms. Eighty zones had evidence of damage with mean T1 values of 453.1 ms ± 113.6 ms. The difference in these T1 values was significant (p = 0.003). Correlation between standard MRI and intra-operative findings was moderate (r = 0.535, p < 0.001). Intra-operative findings revealed more damage than standard MRI. On standard MRI, 68.6% zones were graded normal while 31.4% had evidence of damage. On intra-operative visualization, 56.4% zones were graded normal and 43.6% had evidence of damage. Correlation between dGEMRIC and intra-operative findings turned out to be weak (r = 0.114, p < 0.126). On T1 assessment 31.4% of zones were graded as normal and 68.6% as damaged. CONCLUSIONS: dGEMRIC was significantly different between normal and affected cartilage based on intra-operative assessment. The correlation for morphological findings was limited, underestimating defects. By combining morphological with biochemical assessment dGEMRIC may play some role in the future to prognosticate outcomes and facilitate surgical planning and intervention.

Parametric T2 and T2* mapping techniques to visualize intervertebral disc degeneration in patients with low back pain: initial results on the clinical use of 3.0 Tesla MRI.

OBJECTIVE: To assess, compare and correlate quantitative T2 and T2* relaxation time measurements of intervertebral discs (IVDs) in patients suffering from low back pain, with respect to the IVD degeneration as assessed by the morphological Pfirrmann Score. Special focus was on the spatial variation of T2 and T2* between the annulus fibrosus (AF) and the nucleus pulposus (NP). MATERIALS AND METHODS: Thirty patients (mean age: 38.1 ± 9.1 years; 20 female, 10 male) suffering from low back pain were included. Morphological (sagittal T1-FSE, sagittal and axial T2-FSE) and biochemical (sagittal T2- and T2* mapping) MRI was performed at 3 Tesla covering IVDs L1-L2 to L5-S1. All IVDs were morphologically classified using the Pfirrmann score. Region-of-interest (ROI) analysis was performed on midsagittal T2 and T2* maps at five ROIs from anterior to posterior to obtain information on spatial variation between the AF and the NP. Statistical analysis-of-variance and Pearson correlation was performed. RESULTS: The spatial variation as an increase in T2 and T2* values from the AF to the NP was highest at Pfirmann grade I and declined at higher Pfirmann grades II-IV (p < 0.05). With increased IVD degeneration, T2 and T2* revealed a clear differences in the NP, whereas T2* was additionally able to depict changes in the posterior AF. Correlation between T2 and T2* showed a medium Pearson's correlation (0.210 to 0.356 [p < 0.001]). CONCLUSION: The clear differentiation of IVD degeneration and the possible quantification by means of T2 and fast T2* mapping may provide a new tool for follow-up therapy protocols in patients with low back pain.

Evaluation of cartilage repair tissue after matrix-associated autologous chondrocyte transplantation using a hyaluronic-based or a collagen-based scaffold with morphological MOCART scoring and biochemical T2 mapping: preliminary results.

BACKGROUND: In cartilage repair, bioregenerative approaches using tissue engineering techniques have tried to achieve a close resemblance to hyaline cartilage, which might be visualized using advanced magnetic resonance imaging. PURPOSE: To compare cartilage repair tissue at the femoral condyle noninvasively after matrix-associated autologous chondrocyte transplantation using Hyalograft C, a hyaluronic-based scaffold, to cartilage repair tissue after transplantation using CaReS, a collagen-based scaffold, with magnetic resonance imaging using morphologic scoring and T2 mapping. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Twenty patients after matrix-associated autologous chondrocyte transplantation (Hyalograft C, n = 10; CaReS, n = 10) underwent 3-T magnetic resonance imaging 24 months after surgery. Groups were matched by age and defect size/localization. For clinical outcome, the Brittberg score was assessed. Morphologic analysis was applied using the magnetic resonance observation of cartilage repair tissue score, and global and zonal biochemical T2 mapping was performed to reflect biomechanical properties with regard to collagen matrix/content and hydration. RESULTS: The clinical outcome was comparable in each group. The magnetic resonance observation of cartilage repair tissue score showed slightly but not significantly (P= .210) better results in the CaReS group (76.5) compared to the Hyalograft C group (70.0), with significantly better (P= .004) constitution of the surface of the repair tissue in the CaReS group. Global T2 relaxation times (milliseconds) for healthy surrounding cartilage were comparable in both groups (Hyalograft C, 49.9; CaReS, 51.9; P= .398), whereas cartilage repair tissue showed significantly higher results in the CaReS group (Hyalograft C, 48.2; CaReS, 55.5; P= .011). Zonal evaluation showed no significant differences (P > or = .05). CONCLUSION: Most morphologic parameters provided comparable results for both repair tissues. However, differences in the surface and higher T2 values for the cartilage repair tissue that was based on a collagen scaffold (CaReS), compared to the hyaluronic-based scaffold, indicated differences in the composition of the repair tissue even 2 years postimplantation. CLINICAL RELEVANCE: In the follow-up of cartilage repair procedures using matrix-associated autologous chondrocyte transplantation, differences due to scaffolds have to be taken into account.

Delayed gadolinium-enhanced MRI of cartilage in the ankle at 3 T: feasibility and preliminary results after matrix-associated autologous chondrocyte implantation.

PURPOSE: To demonstrate the feasibility of delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) in the ankle at 3 T and to obtain preliminary data on matrix associated autologous chondrocyte (MACI) repair tissue. MATERIALS AND METHODS: A 3D dual flip angle sequence was used with an eight-channel multipurpose coil at 3 T to obtain T1 maps both pre- and postintravenous contrast agent (Magnevist, 0.2 mM/kg). Postcontrast T1 over time was evaluated in three volunteers; a modified dGEMRIC protocol was then used to assess 10 cases after MACI in the ankle. RESULTS: Forty-five minutes were found sufficient for maximum T1 decrease. MACI cases had a precontrast mean T1 of 1050 +/- 148.4 msec in reference cartilage (RC) and 1080 +/- 165.6 msec in repair tissue (RT). Postcontrast T1 decreased to 590 +/- 134.0 msec in RC and 554 +/- 133.0 msec in RT. There was no significant difference between the delta relaxation rates in RT (9.44 x 10(-4) s(-1)) and RC (8.04 x 10(-4) s(-1), P = 0.487). The mean relative delta relaxation rate was 1.34 +/- 0.83. CONCLUSION: It is feasible to assess the thin cartilage layers of the ankle with dGEMRIC at 3 T; MACI can yield RT with properties similar to articular cartilage.

Assessment of osteoarthritis in hips with femoroacetabular impingement using delayed gadolinium enhanced MRI of cartilage.

PURPOSE: To determine the feasibility of assessing early osteoarthritis (OA) in hips with femoroacetabular impingement (FAI) using delayed Gadolinium enhanced MRI of Cartilage (dGEMRIC). MATERIALS AND METHODS: Thirty-seven hips in 30 patients who had a dGEMRIC scan and radiographic evidence of FAI were identified. Clinical symptoms were assessed. Radiographic measurements were performed to determine acetabular and femoral morphology. The severity of radiographic OA was determined using Tönnis grade and minimum joint space width (JSW). On MRI, the alpha angle was measured on the sagittal oblique slices. Correlations between dGEMRIC index, patient symptoms, morphologic measurements, radiographic OA, and age were determined. RESULTS: Significant correlations were observed between dGEMRIC index, pain (P < 0.05), and alpha angle (P < 0.05). The correlation of dGEMRIC with alpha angle suggests that hips with more femoral deformity show signs of early OA. CONCLUSION: The results of osteoplasty for FAI depend on the amount of pre-existing OA in the joint. dGEMRIC may be a useful technique for diagnosis and staging of early osteoarthritis in hips with impingement.

High resolution fast T1 mapping technique for dGEMRIC.

PURPOSE: To determine the feasibility of using a high resolution isotropic three-dimensional (3D) fast T1 mapping sequence for delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) to assess osteoarthritis in the hip. MATERIALS AND METHODS: T1 maps of the hip were acquired using both low and high resolution techniques following the administration of 0.2 mmol/kg Gd-DTPA(2-) in 35 patients. Both T1 maps were generated from two separate spoiled GRE images. The high resolution T1 map was reconstructed in the anatomically equivalent plane as the low resolution map. T1 values from the equivalent anatomic regions containing femoral and acetabular cartilages were measured on the low and high resolution maps and compared using regression analysis. RESULTS: In vivo T1 measurements showed a statistically significant correlation between the low and high resolution acquisitions at 1.5 Tesla (R(2) = 0.958, P < 0.001). These results demonstrate the feasibility of using a fast two-angle T1 mapping (F2T1) sequence with isotropic spatial resolution (0.8 x 0.8 x 0.8 mm) for quantitative assessment of biochemical status in articular cartilage of the hip. CONCLUSION: The high resolution 3D F2T1 sequence provides accurate T1 measurements in femoral and acetabular cartilages of the hip, which enables the biochemical assessment of articular cartilage in any plane through the joint. It is a powerful tool for researchers and clinicians to acquire high resolution data in a reasonable scan time (< 30 min).

Range of motion after computed tomography-based simulation of intertrochanteric corrective osteotomy in cases of slipped capital femoral epiphysis: comparison of uniplanar flexion osteotomy and multiplanar flexion, valgisation, and rotational osteotomies.

BACKGROUND: Various osteotomy techniques have been developed to correct the deformity caused by slipped capital femoral epiphysis (SCFE) and compared by their clinical outcomes. The aim of the presented study was to compare an intertrochanteric uniplanar flexion osteotomy with a multiplanar osteotomy by their ability to improve postoperative range of motion as measured by simulation of computed tomographic data in patients with SCFE. METHODS: We examined 19 patients with moderate or severe SCFE as classified based on slippage angle. A computer program for the simulation of movement and osteotomy developed in our laboratory was used for study execution. According to a 3-dimensional reconstruction of the computed tomographic data, the physiological range was determined by flexion, abduction, and internal rotation. The multiplanar osteotomy was compared with the uniplanar flexion osteotomy. Both intertrochanteric osteotomy techniques were simulated, and the improvements of the movement range were assessed and compared. RESULTS: The mean slipping and thus correction angles measured were 25 degrees (range, 8-46 degrees) inferior and 54 degrees (range, 32-78 degrees) posterior. After the simulation of multiplanar osteotomy, the virtually measured ranges of motion as determined by bone-to-bone contact were 61 degrees for flexion, 57 degrees for abduction, and 66 degrees for internal rotation. The simulation of the uniplanar flexion osteotomy achieved a flexion of 63 degrees, an abduction of 36 degrees, and an internal rotation of 54 degrees. CONCLUSIONS: Apart from abduction, the improvement in the range of motion by a uniplanar flexion osteotomy is comparable with that of the multiplanar osteotomy. However, the improvement in flexion for the simulation of both techniques is not satisfactory with regard to the requirements of normal everyday life, in contrast to abduction and internal rotation. LEVEL OF EVIDENCE: Level III, Retrospective comparative study.

Do normal radiographs exclude asphericity of the femoral head-neck junction?

Asphericity of the femoral head-neck junction is one cause for femoroacetabular impingement of the hip. However, the asphericity often is underestimated on conventional radiographs. This study compares the presence of asphericity on conventional radiographs with its appearance on radial slices of magnetic resonance arthrography (MRA). We retrospectively reviewed 58 selected hips in 148 patients who underwent a surgical dislocation of the hip. To assess the circumference of the proximal femur, alpha angle and height of asphericity were measured in 14 positions using radial slices of MRA. The hips were assigned to one of four groups depending on the appearance of the head-neck junction on anteroposterior pelvic and lateral crosstable radiographs. Group I (n = 19) was circular on both planes, Group II (n = 19) was aspheric on the crosstable view, Group III (n = 4) was aspheric on the anteroposterior view, and Group IV (n = 13) was aspheric on both views. In all four groups, the highest alpha angle was found in the anterosuperior area of the head-neck junction. Even when conventional radiographs appeared normal, an increased alpha angle was present anterosuperiorly. Without the use of radial slices in MRA, the asphericity would be underestimated in these patients.

Femoroacetabular impingement magnetic resonance imaging.

Femoroacetabular impingement (FAI) of the hip joint is increasingly being recognized as one of the causes of hip pain and restriction of hip motion in young adults. The main subtypes are Pincer and Cam types. MRI digagnostic and relevant surgical information is presented.

Magnetic resonance imaging of the hip at 3 Tesla: clinical value in femoroacetabular impingement of the hip and current concepts.

Magnetic resonance imaging (MRI) is the most promising noninvasive modality for hip joint evaluation, but it has limitations in diagnosing cartilage lesion and acetabular labrum changes, especially in early stages. This is significant due to superior outcome results of surgery intervention in hip dysplasia or femoroacetabular impingement in patients not exceeding early degeneration. This emphasizes the need for accurate and reproducible methods in evaluating cartilage structure. In this article, we discuss the impact of the most recent technological advance in MRI, namely the advantage of 3-T imaging, on diagnostic imaging of the hip. Limitations of standard imaging techniques are shown with emphasis on femoroacetabular impingement. Clinical imaging examples and biochemical techniques are presented that need to be further evaluated.

Comparison of delayed gadolinium enhanced MRI of cartilage (dGEMRIC) using inversion recovery and fast T1 mapping sequences.

The delayed Gadolinium Enhanced MRI of Cartilage (dGEMRIC) technique has shown promising results in pilot clinical studies of early osteoarthritis. Currently, its broader acceptance is limited by the long scan time and the need for postprocessing to calculate the T1 maps. A fast T1 mapping imaging technique based on two spoiled gradient echo images was implemented. In phantom studies, an appropriate flip angle combination optimized for center T1 of 756 to 955 ms yielded excellent agreement with T1 measured using the inversion recovery technique in the range of 200 to 900 ms, of interest in normal and diseased cartilage. In vivo validation was performed by serially imaging 26 hips using the inversion recovery and the Fast 2 angle T1 mapping techniques (center T1 756 ms). Excellent correlation with Pearson correlation coefficient R2 of 0.74 was seen and Bland-Altman plots demonstrated no systematic bias.

Magnetic resonance imaging for diagnosis and assessment of cartilage defect repairs.

Clinical magnetic resonance imaging (MRI) is the method of choice for the non-invasive evaluation of articular cartilage defects and the follow-up of cartilage repair procedures. The use of cartilage-sensitive sequences and a high spatial-resolution technique enables the evaluation of cartilage morphology even in the early stages of disease, as well as assessment of cartilage repair. Sequences that offer high contrast between articular cartilage and adjacent structures, such as the fat-suppressed, 3-dimensional, spoiled gradient-echo sequence and the fast spin-echo sequence, are accurate and reliable for evaluating intrachondral lesions and surface defects of articular cartilage. These sequences can also be performed together in reasonable examination times. In addition to morphology, new MRI techniques provide insight into the biochemical composition of articular cartilage and cartilage repair tissue. These techniques enable the diagnosis of early cartilage degeneration and help to monitor the effect and outcome of various surgical and non-surgical cartilage repair therapies.