Clinical advantages of 3.0 T MRI over 1.5 T

Since approval by the FDA in 2000, human MR imaging (MRI) at 3.0 T has been increasingly used in clinical practice. In spite of the potential technical challenges, a number of clinical advantages of 3.0 T MRI over 1.5 T have been identified in the recent years. This article reviews the benefits and the current knowledge of 3.0 T whole-body MRI from an evidence-based perspective and summarizes its clinical applications.     

T1rho MRI of menisci and cartilage in patients with osteoarthritis at 3T

Objective

To assess and compare subregional and whole T1rho values (median ± interquartile range) of femorotibial cartilage and menisci in patients with doubtful (Kellgren–Lawrence (KL) grade 1) to severe (KL4) osteoarthritis (OA) at 3T.

Materials and methods

30 subjects with varying degrees of OA (KL1–4, 13 females, 17 males, mean age ± SD = 63.9 ± 13.1 years) were evaluated on a 3T MR scanner using a spin-lock-based 3D GRE sequence for T1rho mapping. Clinical proton density (PD)-weighted fast spin echo (FSE) images in sagittal (without fat saturation), axial, and coronal (fat-saturated) planes were acquired for cartilage and meniscus Whole-organ MR imaging score (WORMS) grading. Wilcoxon rank sum test was performed to determine whether there were any statistically significant differences between subregional and whole T1rho values of femorotibial cartilage and menisci in subjects with doubtful to severe OA.

Results

Lateral (72 ± 10 ms, median ± interquartile range) and medial (65 ± 10 ms) femoral anterior cartilage subregions in moderate–severe OA subjects had significantly higher T1rho values (P < 0.05) than cartilage subregions and whole femorotibial cartilage in doubtful–minimal OA subjects. There were statistically significant differences in meniscus T1rho values of the medial posterior subregion of subjects with moderate–severe OA and T1rho values of all subregions and the whole meniscus in subjects with doubtful–minimal OA. When evaluated based on WORMS, statistically significant differences were identified in T1rho values between the lateral femoral anterior cartilage subregion in patients with WORMS5–6 (advanced degeneration) and whole femorotibial cartilage and all cartilage subregions in patients with WORMS0–1 (normal).

Conclusion

T1rho values are higher in specific meniscus and femorotibial cartilage subregions. These findings suggest that regional damage of both femorotibial hyaline cartilage and menisci may be associated with osteoarthritis.     

3D-imaging of the knee with an optimized 3D-FSE-sequence and a 15-channel knee-coil

Objectives

To evaluate the clinical usefulness of an optimized 3D-Fast-Spin-Echo-sequence (3D-SPACE) in combination with a 15-channel knee-coil for 3D-imaging of the knee at 3 T.

Methods

15 volunteers and 50 consecutive patients were examined at 3 T with fat-saturated moderately T2-weighted 3D-SPACE (Voxel-size (VS): 0.6 mm × 0.5 mm × 0.5 mm/acquisition-time (AT) 10:44 min) using a 15-channel knee-coil. Flip angle optimization and radial k-space reordering were applied. Signal- and contrast-to-noise-ratios (SNR, CNR) were compared to non-optimized 3D-SPACE (8-channel knee-coil) and conventional 2D-FSE (VS: 0.4 mm × 0.4 mm × 3 mm/total AT: 12 min). Two radiologists independently rated depiction of internal knee structures and assessed detection and depiction of cartilage and meniscus abnormalities compared to conventional 2D-FSE-sequences. Sensitivity and specificity were calculated for a subgroup with arthroscopy as reference standard. Statistical analysis was performed with paired t-tests, confidence intervals and weighted-κ-coefficients.

Results

SNR and CNR particularly of fluid/cartilage of optimized 3D-SPACE were significantly higher (p < 0.05) than of the non-optimized 3D-sequence and conventional 2D-sequence. Blurring and image inhomogeneity were reduced in the optimized sequence. The thin slice-thickness was beneficial for depiction of problematical anatomical structures such as meniscal roots. 3D-SPACE showed significantly higher diagnostic confidence (p < 0.05) for diagnosis of cartilage lesions of the femoral trochlea. Overall sensitivity and specificity of 3D-SPACE and 2D-FSE for cartilage lesions was 82.3%/80.2% and 79.4%/84.2% and 100%/86.4% and 92.3%/81.8% for meniscus lesions.

Conclusions

Optimized 3D-SPACE provides significantly higher signal and contrast compared to conventional 2D-FSE, particularly for fluid and cartilage, leading to improved diagnostic confidence, particularly in problematic areas, such as the femoral trochlea.     

3T MRI in paediatrics: challenges and clinical applications

3T MRI is being increasingly performed for clinical purposes in paediatrics, primarily because of the potential to improve spatial and temporal resolution - these can assist in overcoming the unique anatomic, physiologic and behavioural challenges of imaging children. The increased spatial resolution improves the capacity to image small patients; with particular reference to smaller structures such as the inner ear, brachial plexus, biliary system and the vascular system. The challenges inherent to imaging at high field strength remain pertinent especially, the altered T1 contrast, artefacts (susceptibility, chemical shift and B1 inhomogeneity) and safety issues, including specific absorption rate - several of these are circumvented due to software and hardware advances, or by trade off of some of the increased signal. The above mentioned challenges also create opportunities at 3T, with improvement in MR angiography, arterial spin labelling, functional MRI, susceptibility weighted imaging, and MR spectroscopy - all of which have distinctive applications in paediatrics. Whole body imaging also becomes more practical because of the capacity for faster scans. 3T MRI has the potential to image all the systems in paediatrics. However, neonatal brain and paediatric spine imaging have specific challenges at 3T. Several factors also limit cardiac imaging at present. Further improvements in coil technology and newer sequences may help overcome the challenges that remain.     

Contrast-enhanced MRI of subchondral cysts in patients with or at risk for knee osteoarthritis: The MOST study

Objective

The aim of the study was (1) to evaluate contrast enhancement patterns of subchondral cysts on magnetic resonance imaging and (2) to discuss possible radiological explanations of cyst enhancement based on existing theories of subchondral cyst formation in osteoarthritis.

Materials and methods

The Multicenter Osteoarthritis Study (MOST) is a NIH-funded longitudinal observational study for individuals who have or are at high risk for knee osteoarthritis. All subjects with available non-enhanced and contrast-enhanced MRI were included. The tibiofemoral and patellofemoral joints were divided in 14 subregions. The presence and size of subchondral cysts and bone marrow edema-like lesions (BMLs) were scored semiquantitatively in each subregion on non-contrast-enhanced MRI from 0 to 3. Enhancement of subchondral cysts was evaluated on contrast-enhanced MRI as grade 0 (absent), grade 1 (partial enhancement), or grade 2 (full enhancement). The adjacent articular cartilage was scored in each subregion on non-enhanced MRI as grade 0 (intact), grade 1 (partial thickness loss), or grade 2 (full thickness loss).

Results

Four hundred knees were included (1 knee per person, 5600 subregions). Subchondral cysts were detected in 260 subregions (4.6%). After intravenous contrast administration, 245 cysts (94.2%) showed full enhancement, 12 (4.6%) showed partial enhancement and 3 (1.2%) showed no enhancement. Enhancing BMLs were found in 237 (91.2%) subregions containing cysts, which were located adjacent or in the middle of BMLs. In 121 subregions (46.5%) having cysts, no adjacent full thickness cartilage loss was detected.

Conclusion

Most subchondral cysts demonstrated full or partial contrast enhancement, and were located adjacent or in the midst of enhancing BMLs. As pure cystic lesions are not expected to enhance on MRI, the term “subchondral cyst-like bone marrow lesion” might be appropriate to describe these lesions.     

Longitudinal analysis of MRI T2 knee cartilage laminar organization in a subset of patients from the osteoarthritis initiative

The purpose of this pilot study was to longitudinally quantify the T₂ laminar integrity of knee cartilage in a subset of subjects with osteoarthritis from the Osteoarthritis Initiative at baseline, 1‐year follow‐up, and 2‐year follow‐up. Cartilage from 13 subjects was divided into six compartments and subdivided into deep and superficial layers. At each time point, mean T₂ values in superficial and deep layers were compared. Longitudinal analysis included full‐thickness mean T₂, mean deep T₂, mean superficial T₂, mean T₂ laminar difference, mean percentage T₂ laminar difference, and two‐dimensional measures of cartilage thickness. More compartments showed significantly higher superficial T₂ than deep T₂ values at baseline and 1‐year follow‐up compared to 2‐year follow‐up. No significant longitudinal changes of full‐thickness mean T₂ and superficial T₂ values were observed. Significant longitudinal changes were observed in the deep T₂ values, T₂ laminar difference, and percentage T₂ laminar difference. Cartilage thickness had no influence on T₂ analysis. Results of this study suggest that laminar analysis may improve the sensitivity to detect longitudinal T₂ changes and that disruption of the T₂ laminar organization of knee cartilage may be present in knee osteoarthritis progressors. Further investigation is warranted to evaluate the potential of the presented methodology to better characterize evolution and pathophysiology of osteoarthritis. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc.     

Biochemical evaluation of articular cartilage in patients with osteochondrosis dissecans by means of quantitative T2- and T2-mapping at 3T MRI: a feasibility study

Objective

To perform an in vivo evaluation comparing overlying articular cartilage in patients suffering from osteochondrosis dissecans (OCD) in the talocrural joint and healthy volunteers using quantitative T2 mapping at 3.0 T.

Method and materials

Ten patients with OCD of Grade II or lower and 9 healthy age matched volunteers were examined at a 3.0 T whole body MR scanner using a flexible multi-element coil. In all investigated persons MRI included proton-density (PD)-FSE and 3D GRE (TrueFisp) sequences for morphological diagnosis and location of anatomical site and quantitative T2 and T2* maps. Region of interest (ROI) analysis was performed for the cartilage layer above the OCD and for a morphologically healthy graded cartilage layer. Mean T2 and T2* values were then statistically analysed.

Results

The cartilage layer of healthy volunteers showed mean T2 and T2* values of 29.4 ms (SD 4.9) and 11.8 ms (SD 2.7), respectively. In patients with OCD of grade I and II lesions mean T2 values were 40.9 ms (SD 6.6), 48.7 ms (SD 11.2) and mean T2* values were 16.1 ms (SD 3.2), 16.2 ms (SD 4.8). Therefore statistically significantly higher mean T2 and T2* values were found in patients suffering from OCD compared to healthy volunteers.

Conclusion

T2 and T2* mapping can help assess the microstructural composition of cartilage overlying osteochondral lesions.     

The relationship between limited MRI section analyses and volumetric assessment of synovitis in knee osteoarthritis

AIM: To assess whether simple, limited section analysis can replace detailed volumetric assessment of synovitis in patients with osteoarthritis (OA) of the knee using contrast-enhanced magnetic resonance imaging (MRI). MATERIALS AND METHODS: Thirty-five patients with clinical and radiographic OA of the knee were assessed for synovitis using gadolinium-enhanced MRI. The volume of enhancing synovium was quantitatively assessed in four anatomical sites (the medial and lateral parapatellar recesses, the intercondylar notch and the suprapatellar pouch) by summing the volumes of synovitis in consecutive sections. Four different combinations of section analysis were evaluated for their ability to predict total synovial volume. RESULTS: A total of 114 intra-articular sites were assessed. Simple linear regression demonstrated that the best predictor of total synovial volume was the analysis containing the inferior, mid and superior sections of each of the intra-articular sites, which predicted between 40-80% (r(2) = 0.396, p < 0.001 for notch; r(2) = 0.818, p < 0.001 for medial parapatellar recess) of the total volume assessment. CONCLUSIONS: The results suggest that a three-section analysis on axial post-gadolinium sequences provides a simple surrogate measure of synovial volume in OA knees.     

Mid-term clinical results of medial meniscus repair with the meniscus arrow in the unstable knee

The medial meniscus is a secondary stabilizer to anterior tibial translation and provides significant stability, especially in an ACL-deficient knee. The purpose of this study is to evaluate the clinical outcome of medial meniscus repair in the unstable knee. Between 1997 and 2002, 11 patients, with a mean age of 25.8 years (range 15–39 years), underwent all-inside medial meniscus repair, using the Meniscus Arrow, for unstable medial meniscus tear in ACL-deficient knees. For various reasons none of these patients underwent ACL reconstruction. The average follow-up was 73 months (range 52–91 months). There were three failures (27.3%) defined as the need for reoperation and partial meniscectomy. The mean Tegner activity score decreased from 6.75 (pretrauma) to 4.5 (postoperatively). The average Lysholm and subjective IKDC scores were 83 and 77.4, respectively. Two patients were graded as B (nearly normal) and six as C (abnormal), according to the IKDC knee evaluation form. KT-2000 arthrometry demonstrated that sagittal knee laxity was more than 5 mm in all knees (side to side difference). MRI demonstrated grade three signal alterations at the repair site of meniscus in three patients and signs of cartilage damage in two patients. All patients were asymptomatic during daily activities but seven out of eight reported pain or effusion after sports. Medial meniscus repair in the ACL-deficient knee is not contraindicated. The need of reducing the level of physical activity is essential.     

Feasibility of 3.0T pelvic MR imaging in the evaluation of endometriosis

Introduction

Endometriosis represents an important clinical problem in women of reproductive age with high impact on quality of life, work productivity and health care management. The aim of this study is to define the role of 3 T magnetom system MRI in the evaluation of endometriosis.

Materials and methods

Forty-six women, with transvaginal (TV) ultrasound examination positive for endometriosis, with pelvic pain, or infertile underwent an MR 3.0 T examination with the following protocol: T2 weighted FRFSE HR sequences, T2 weighted FRFSE HR CUBE 3D sequences, T1 w FSE sequences, LAVA-flex sequences. Pelvic anatomy, macroscopic endometriosis implants, deep endometriosis implants, fallopian tube involvement, adhesions presence, fluid effusion in Douglas pouch, uterus and kidney pathologies or anomalies associated and sacral nervous routes were considered by two radiologists in consensus. Laparoscopy was considered the gold standard.

Results

MRI imaging diagnosed deep endometriosis in 22/46 patients, endometriomas not associated to deep implants in 9/46 patients, 15/46 patients resulted negative for endometriosis, 11 of 22 patients with deep endometriosis reported ovarian endometriosis cyst. We obtained high percentages of sensibility (96.97%), specificity (100.00%), VPP (100.00%), VPN (92.86%).

Conclusion

Pelvic MRI performed with 3 T system guarantees high spatial and contrast resolution, providing accurate information about endometriosis implants, with a good pre-surgery mapping of the lesions involving both bowels and bladder surface and recto-uterine ligaments.     

Displacement of the medial meniscus within the passive motion characteristics of the human knee joint: an RSA study in human cadaver knees

The objective of this study was to validate an in vitro human cadaver knee-joint model for the evaluation of the meniscal movement during knee-joint flexion. The question was whether our model showed comparable meniscal displacements to those found in earlier meniscal movement studies in vivo. Furthermore, we determined the influence of tibial torque on the meniscal displacement during knee-joint flexion. Three tantalum beads were inserted in the medial meniscus of six human-cadaver joints. The knee joints were placed and loaded in a loading apparatus, and the movements of the beads were determined by means of RSA during knee-joint flexion and extension with and without internal tibial (IT) and external tibial (ET) torque. During flexion without tibial torque, all menisci moved in posterior and lateral direction. The anterior horn showed significantly greater excursions than the posterior horn in both posterior and lateral direction. Internal tibial torque caused an anterior displacement of the pathway on the tibial plateau. External tibial torque caused a posterior displacement of the pathway. External tibial torque restricted the meniscal displacement during the first 30° of knee-joint flexion. The displacements of the meniscus in this experiment were similar to the displacements described in the in vivo MRI studies. Furthermore, the application of tibial torque confirmed the relative immobility of the posterior horn of the meniscus. During external tibial torque, the posterior displacement of the pathway on the tibial plateau during the first 30° of flexion might be restricted by the attached knee-joint capsule or the femoral condyle. This model revealed representative meniscal displacements during simple knee-joint flexion and also during the outer limits of passive knee-joint motion.     

Optimal breathing protocol for dynamic contrast-enhanced MRI of solitary pulmonary nodules at 3T

The purpose of this study was to evaluate optimal breathing maneuvers that minimize lung parenchymal movement for dynamic contrast-enhanced MRI (DCE-MRI), which requires longer scan times, beyond the limit of a single breath hold. A healthy volunteer was scanned on a 3T MR scanner using two different breathing maneuvers. In the first, the healthy volunteer was instructed to hold his breath as much as possible and breathe in between breath holds while an image was obtained. In the second, the volunteer was instructed to breathe shallowly and freely throughout the scan. On the obtained images, the excursion of the highest point of the right diaphragm and the pulmonary vessel branches located in the four different anatomic regions of the lung were measured in two orthogonal planes. A patient with a solitary pulmonary nodule (SPN) underwent DCE-MRI utilizing a 2D spoiled gradient-echo (SPGR) sequence while the patient breathed shallowly and freely during the scan. The standard deviations of the excursion of the highest point and selected pulmonary vessels were much smaller during shallow, free breathing maneuver scans than those during breath hold maneuver scans. A dynamic perfusion-fitting curve of the SPN was obtained during the DCE-MRI using shallow free breathing. Shallow, free breathing allows smaller diaphragmatic cranial caudal and lung parenchymal displacements. Therefore, it can be useful during exams where targeting of the lesion is necessary, in studies with long scan times, such as dynamic MRI. This breathing maneuver makes it possible to analyze SPN with DCE-MRI while making use of the advantages of a higher magnetic field in conjunction.     

T2* measurement of the knee articular cartilage in osteoarthritis at 3T

Purpose:

To measure reproducibility, longitudinal and cross‐sectional differences in T2* maps at 3 Tesla (T) in the articular cartilage of the knee in subjects with osteoarthritis (OA) and healthy matched controls.

Materials and Methods:

MRI data and standing radiographs were acquired from 33 subjects with OA and 21 healthy controls matched for age and gender. Reproducibility was determined by two sessions in the same day, while longitudinal and cross‐sectional group differences used visits at baseline, 3 and 6 months. Each visit contained symptomological assessments and an MRI session consisting of high resolution three‐dimensional double‐echo‐steady‐state (DESS) and co‐registered T2* maps of the most diseased knee. A blinded reader delineated the articular cartilage on the DESS images and median T2* values were reported.

Results:

T2* values showed an intra‐visit reproducibility of 2.0% over the whole cartilage. No longitudinal effects were measured in either group over 6 months. T2* maps revealed a 5.8% longer T2* in the medial tibial cartilage and 7.6% and 6.5% shorter T2* in the patellar and lateral tibial cartilage, respectively, in OA subjects versus controls (P < 0.02).

Conclusion:

T2* mapping is a repeatable process that showed differences between the OA subject and control groups. J. Magn. Reson. Imaging 2012;35:1422–1429. © 2012 Wiley Periodicals Inc.     

Radiographic joint space narrowing in osteoarthritis of the knee: relationship to meniscal tears and duration of pain

OBJECTIVE: The objective of this study was to assess, with knee radiography, joint space narrowing (JSN) and its relationship to meniscal tears, anterior cruciate ligament (ACL) ruptures, articular cartilage erosion, and duration of pain in patients with knee osteoarthritis. MATERIALS AND METHODS: A total of 140 patients who had knee osteoarthritis and underwent primary total knee replacement (TKR) surgery, with unicompartmental medial tibiofemoral JSN (grade 1 or greater) and normal lateral compartments, were recruited. Polytomous logistic regression was used to assess the relationship between JSN and risk factors. RESULTS: All patients with JSN were categorized as grade 1 (n = 14, 10.0%), grade 2 (n = 64, 45.7%), or grade 3 (n = 62, 44.3%). Women presented with indications for a TKR at a younger age than men (mean age, 69 vs 73 years, P < 0.05). There were 123 (87.9%) meniscal tears and 58 (41.4%) partial (insufficient or attenuated ACL fibers) and 10 (7.1%) complete ACL ruptures; 115 of 134 (85.8%) patients had moderate to severe cartilage erosion. A higher grade of JSN was correlated with a higher frequency of meniscal tears [odds ratio (OR) 6.00, 95% CI 1.29-27.96 for grade 2 vs grade 1 JSN] and duration of knee pain (OR 1.25, 95% CI 1.01-1.53 for grade 3 vs grade 1 JSN). A higher grade of JSN was not correlated with a higher frequency of ACL rupture or articular cartilage erosion. CONCLUSION: A higher grade of JSN is associated with a higher frequency of meniscal tears and long duration of knee pain in patients with knee osteoarthritis.     

Cardiac cine MRI: comparison of 1.5 T, non-enhanced 3.0 T and blood pool enhanced 3.0 T imaging

INTRODUCTION: Cardiac cine imaging using balanced steady state free precession sequences (bSSFP) suffers from artefacts at 3.0 T. We compared bSSFP cardiac cine imaging at 1.5 T with gradient echo imaging at 3.0 T with and without a blood pool contrast agent. MATERIALS AND METHODS: Eleven patients referred for cardiac cine imaging underwent imaging at 1.5 T and 3.0 T. At 3.0 T images were acquired before and after administration of 0.03 mmol/kg gadofosveset. Blood pool signal-to-noise ratio (SNR), temporal variations in SNR, ejection fraction and myocardial mass were compared. Subjective image quality was scored on a four-point scale. RESULTS: Blood pool SNR increased with more than 75% at 3.0 T compared to 1.5 T (p<0.001); after contrast administration at 3.0 T SNR increased with 139% (p<0.001). However, variations in blood pool SNR at 3.0 T were nearly three times as high versus those at 1.5 T in the absence of contrast medium (p<0.001); after contrast administration this was reduced to approximately a factor 1.4 (p=0.21). Saturation artefacts led to significant overestimation of ejection fraction in the absence of contrast administration (1.5 T: 44.7+/-3.1 vs. 3.0 T: 50.7+/-4.2 [p=0.04] vs. 3.0 T post contrast: 43.4+/-2.9 [p=0.55]). Subjective image quality was highest for 1.5 T (2.8+/-0.3), and lowest for non-enhanced 3.0 T (1.7+/-0.6; p=0.006). CONCLUSIONS: GRE cardiac cine imaging at 3.0 T after injection of the blood pool agent gadofosveset leads to improved objective and subjective cardiac cine image quality at 3.0 T and to the same conclusions regarding cardiac ejection fraction compared to bSSFP imaging at 1.5 T.     

Premature osteoarthritis of the knee associated with cartilage hypertrophy and phalangeal dysgenesis

A woman presented with premature knee osteoarthritis associated with marked femoral cartilage hypertrophy. She also exhibited phalangeal dysgenesis, suggesting this may be an unrecognised syndrome that may predispose to knee osteoarthritis.     

膝关节骨性关节炎的X线测量与分析

目的:通过对膝关节骨性关节炎患者X线片的测量,分析膝关节骨性关节炎患者股骨、胫骨和髌骨形态学改变,以及三者之间排列关系的改变,进而分析这些改变在膝关节骨性关节炎中的诊治意义和作用。方法:取正常组100例膝和膝关节骨性关节炎组127例膝,拍摄正位、侧位和髌骨轴位CR片,并对其分组逐一测量股骨角等指标,应用统计学方法对测量结果卡方检验,对检验结果进行分析,并结合临床进行讨论。结果:膝关节骨性关节炎组(KOA组)胫骨角等的检验结果与正常组存在差异,有统计学意义。而股骨角的检验结果与正常组间无差异。结论:①在膝关节骨性关节炎患者影像学分析中,出现了胫骨角等指标的变化。股骨角对于膝关节骨性关节炎的影像学分析不敏感。②在膝关节骨性关节炎患者影像学分析和统计学检验中,验证了膝内翻发生率高于膝外翻,股胫关节内侧间隙狭窄多于股胫关节外侧间隙狭窄。③在膝关节骨性关节炎患者X线分析中,发现髌股关节可出现髌骨外翻脱位。     

Presumptive subarticular stress reactions of the knee: MRI detection and association with meniscal tear patterns

Objective MRI detects subchondral marrow findings in painful knees which bear resemblance to spontaneous osteonecrosis of the knee (SONK). Gathering evidence suggests that the primary or predominant pathogenesis of these lesions is physical stress. This study analyzes the patient characteristics and meniscal pathology associated with these lesions—herein referred to as presumptive subarticular stress related (PSSR) lesions.Design and patients All patients were scanned using a standardized imaging protocol. The criterion for a PSSR lesion was a subchondral marrow edema pattern encompassing a more focal, low-signal zone adjacent to or contiguous with the subchondral cortex. Patients were identified using an electronic database search of cases reported by one experienced musculoskeletal radiologist.Results Twenty-five PSSR lesions were identified among 1,948 MRI evaluations of the knee. Twenty-one PSSR lesions occurred in the medial compartment, and four occurred in the lateral compartment. There was no sex predilection. Patients with PSSR lesions were older than other patients undergoing MRI evaluation (mean 66 years versus 52 years, P<0.001). Meniscal tears occurred more commonly in cases with PSSR lesions than in the group as a whole (76% versus 45%, P<0.001). Radial and posterior root tears were more common in knees with PSSR lesions than in other knees with meniscal tears (53% versus 26%, P<0.01).Conclusions PSSR lesions are associated with meniscal tears and, more specifically, with meniscal tear patterns that dramatically increase contact forces across the knee joint. This observation supports the hypothesis that mechanical stress is important in the pathogenesis of these subarticular lesions that are detected by MRI.     

Reproducibility of joint space width and the intermargin distance measurements in patients with medial osteoarthritis of the knee in various degrees of flexion

Objective  This study tested the variability and reproducibility of measurements of the joint space width (JSW) and intermargin distance (IMD) of the medial tibial plateau in specific positions of knee flexion in osteoarthritic knees in order to evaluate the most useful knee angle for radiographic measurements. Design  Radiographs from 56 knees with osteoarthritis from 46 patients were taken with the knees in conventional full extension and 15°, 30°, and 45° of flexion with weight bearing. Three orthopedic surgeons independently measured the JSW and IMD at the narrowest point and the midpoint of medial tibial plateau using a computer-assisted method. Results  The JSW and IMD were smallest at 15° flexion, both measured at the narrowest point and the midpoint of the medial compartment. Reproducibility of the IMD at the midpoint was better than at the narrowest point for all four flexion angles. Conclusion  Measurements of the medial JSW and IMD are smallest at 15° of knee flexion indicating that radiographs should be obtained at this angle in order to best demonstrate the extent of osteoarthritis.     

膝关节软骨磁共振T2弛豫时间测定在早期骨关节炎中的应用价值

目的:探讨关节软骨磁共振T2弛豫时间定量分析在早期膝关节骨关节炎(OA)中的应用价值。方法:运用T2mapping成像测量正常组(n=12)和平片没有阳性发现的早期OA组(n=15)膝关节胫骨内侧髁、外侧髁,股骨内侧髁、外侧髁和髌骨5处软骨的T2值,并进行统计学分析。结果:正常组膝关节软骨T2值33.8~35.6ms,早期OA组膝关节软骨T2值40.3~42.7ms。病例组膝关节各处软骨的T2值差异有显著性意义(P<0.01)。结论:T2弛豫时间定量分析可以发现没有形态学变化的OA关节软骨内成分变化,在早期OA诊断中有较高的应用价值。