CT measures of femoral and tibial version and rotational position of femoral and tibial components of knee replacements: limitations in reliability and suitability for routine clinical practice.

OBJECTIVES: Rotational malalignment of knee replacements as measured on CT is understood to be associated with poor outcomes. The aim of this study is to measure the inter-rater and intra-rater reliability of measures of femoral and tibial version in the native arthritic knee and postoperative TKR component position using CT. METHODS: Eighty patients underwent CT of the knee before and after total knee replacement. Preoperative femoral and tibial version and component rotation were independently measured by two musculoskeletal radiologists. RESULTS: Mean differences between and within raters were small (< 1.6°). Maximum 95% limits of agreement for inter-rater and intra-rater comparisons were 8.1° and 7.6° for preoperative femoral version, 9.0° and 7.9° for postoperative femoral rotation, 26.0° and 20.5° for preoperative tibial version, and 24.9° and 23.6° for postoperative tibial rotation respectively. Postoperative ICCs varied from 0.68 to 0.81 (lower 95% CI:0.55-0.72) for both intra- and inter-rater comparisons. Preoperative ICCs were lower: 0.55-0.75 (lower 95% CI:0.40-0.65). CONCLUSION: The lower 95% confidence level for ICC of version and rotational measurements using the Berger protocol of TKRs on CT are all less than 0.73 and that the normal range of differences between observers is up to 9° for the femoral component and 26° for the tibial component. This suggests that CT measurements derived from the Berger protocol may not be consistent enough for clinical practice. KEY POINTS: • CT is commonly used to measure the rotational profile of knee replacements in symptomatic patients using the Berger protocol. • The limits of agreement for both femoral and tibial component rotation are wide even for experienced observers. • CT measurements of the rotation of knee arthroplasty are not reliable enough for routine clinical use.

Teriparatide and stress fracture healing in young adults (RETURN - Research on Efficacy of Teriparatide Use in the Return of recruits to Normal duty): study protocol for a randomised controlled trial.

BACKGROUND: Stress fractures are a common and potentially debilitating overuse injury to bone and occur frequently among military recruits and athletes. Recovery from a lower body stress fracture typically requires several weeks of physical rehabilitation. Teriparatide, a recombinant form of the bioactive portion of parathyroid hormone (1-34 amino acids), is used to treat osteoporosis, prevent osteoporotic fractures, and enhance fracture healing due to its net anabolic effect on bone. The study aim is to investigate the effect of teriparatide on stress fracture healing in young, otherwise healthy adults undergoing military training. METHODS: In a two-arm, parallel, prospective, randomised controlled, intention-to-treat trial, Army recruits (n = 136 men and women, 18-40 years) with a magnetic resonance imaging (MRI) diagnosed lower body stress fracture (pelvic girdle, sacrum, coccyx, or lower limb) will be randomised to receive either usual Army standard care, or teriparatide and usual Army standard care. Teriparatide will be self-administered by subcutaneous injections (20 µg/day) for 16 weeks, continuing to 24 weeks where a fracture remains unhealed at week 16. The primary outcome will be the improvement in radiological healing by two grades or more, or reduction to grade zero, 8 weeks after randomisation, assessed using Fredericson grading of MRI by radiologists blind to the randomisation. Secondary outcomes will be time to radiological healing, assessed by MRI at 8, 10, 12, 14, 16, 20 and 24 weeks, until healed; time to clinical healing, assessed using a clinical severity score of injury signs and symptoms; time to discharge from Army physical rehabilitation; pain, assessed by visual analogue scale; health-related quality of life, using the Short Form (36) Health Survey; and adverse events. Exploratory outcomes will include blood and urine biochemistry; bone density and morphology assessed using dual-energy X-ray absorptiometry, peripheral quantitative computed tomography (pQCT), and high-resolution pQCT; physical activity measured using accelerometers; and long-term future fracture rate. DISCUSSION: This study will evaluate whether teriparatide, in addition to standard care, is more effective for stress fracture healing than standard care alone in Army recruits who have sustained a lower body stress fracture. TRIAL REGISTRATION: ClinicalTrials.gov NCT04196855 . Registered on 12 December 2019.

The reliability of radiographic measures of total ankle replacement position: an analysis from the OARS cohort.

OBJECTIVE: There is no validated radiographic measurement to diagnose prosthetic complication(s) following total ankle replacements (TARs) although a number of angular and linear measurements, used to define the TAR position on postoperative radiographs, have been recommended to detect prosthetic loosening. The aim of this study was to test the intra- and interobserver reliability of these measurements. MATERIALS AND METHODS: This is a prospective study embedded within a multicentre cohort study. Following sample size calculation, 62 patients were analysed. Six measurements were performed on the first postoperative anteroposterior and lateral ankle radiographs: angles α and ß, and length "a" defined the craniocaudal position of the tibial component, while angle γ, and lengths "b" and "c" defined the angular position of the talar component. Measurements were recorded by three independent observers. Inter- and intraobserver reliability was assessed with intraclass correlation coefficient (ICC), Bland-Altman plots, and within-subject coefficients of variation (CV). RESULTS: The intrarater ICC was "almost perfect" (ICC 0.83-0.97) for all six measurements. The interrater ICC was "substantial" to "almost perfect" (ICC 0.69-0.93). The mean difference in intrarater angular measurements was ≤ 0.6° and ≤ 0.8 mm for linear measurements, and ≤ 2.2° and ≤ 2.1 mm for interrater measurements. Maximum CV for the interrater linear measurements (≤ 17.7%) more than doubled that of the angular measurements (≤ 8.0%). The maximum width of the 95% limits of agreement was 6.5° and 8.4 mm for intrarater measures, and 8.9° and 10.6 mm for interrater measurements. CONCLUSION: Angular measures are more reliable than linear measures and have potential in routine clinical practice for TAR position assessment.

Correlation of MARS MRI findings with cup position, metal ion levels and function in metal-on-metal total hip arthroplasty.

INTRODUCTION: Metal-on-metal (MoM) total hip arthroplasties (THAs) have been linked with increased incidence of pseudotumours and revision rate. magnetic resonance imaging (MRI) is useful in diagnosing adverse reaction to metal debris (ARMD) disease but it is not known if MRI findings correlate with cup position. PATIENTS AND METHODS: From a cohort of 79 MoM THA, 34 MRI studies were available. MRI was classified according to Anderson classification. Mean follow-up was 7.1 years. Evaluation included cup position including margin of safety, measurement of metal ion levels and evaluation of function. RESULTS: 44% of patients had definite ARMD. We did not find any correlation between MRI stage and Co, Cr, margin of safety (MOS) or functional scores. However, patients with a margin of safety angle < 21° had more severe findings in MRI. CONCLUSIONS: Patients with MoM THA experience high degree of ARMD. In our study, the disease did not correlate with metal ion levels but correlated with cup position, evaluated with the MOS angle.

Normal variations in position and relations of the median nerve in the carpal tunnel: A cross-sectional observational study using clinical magnetic resonance imaging.

A standard relationship of the median nerve to neighboring tendons in the carpal tunnel has been described, but descriptions of normal variations are limited. The aim of this study is to describe the variation in position of the median nerve within the carpal tunnel and the variability in relation to adjacent tendons on clinical MR studies. A retrospective study was performed, analyzing 37 wrist MR examinations performed on a 3T MR machine. Primary endpoints involved measuring the four coordinates of the median nerve in relation to anatomical bony landmarks performed on a single-slice image. The secondary endpoints were anterior, posterior, medial, and lateral relations of the median nerve. The mean distance from hook of hamate to trapezium was 21.8 mm with a mean depth of 9.6 mm. The mean position of the median nerve from the hook of the hamate was 12.5 mm with a depth of 2.9 mm. The most common radial relations to the median nerve in descending order of frequencies were FPL, FDS 2, and FDS 3, the most common dorsal relations were FDS 2 and then FDS 3, and the most common ulnar relations were FDS 3 and then FDS 2. The position of the median nerve in the carpal tunnel is variable both in ulna-to-radial and dorsal to palmar directions, and variations in relation to neighboring tendons are also common. Clin. Anat. 33:598-604, 2020. © 2019 Wiley Periodicals, Inc.

Paravertebral Collateral Arteries in Patients with Carotid Stenosis: Is There a Safe Space for Transforaminal Cervical Nerve Root Injections?

AIM: Image-guided cervical nerve root injections can cause serious complications including spinal cord infarction. This risk may be increased in patients with carotid stenosis who develop collateral arteries. The aim of this study is to describe the prevalence, and anatomical location, of arterial collateral vessels in relation to the optimal needle tip position in cervical nerve root injections. MATERIALS AND METHODS: This retrospective study included 25 patients who had > 70% stenosis on a carotid CT angiogram. For each foramen the position of collateral arteries and the most anterior point of the facet joint were recorded, as Cartesian coordinates, by two independent observers. Descriptive statistics were used to analyse and present the results. RESULTS: 14 patients had unilateral and 11 had bilateral stenoses. A total of 85 collaterals were identified at all levels, the most common being C2/3. The median distance from collateral to optimal needle tip placement was 9.6 mm (95% CI median: 6.7-12.4, IQR: 5.6-15.6). The minimum distance was 2.9 mm. Inter-observer reliability was "substantial" (ICC 0.78, 95% CI 0.71-0.83). CONCLUSION: Collateral arteries were common in our cohort of patients with carotid artery stenosis and half lay within 10 mm of the optimal position for transforaminal cervical nerve root injection.

Measuring liver fat fraction with complex-based chemical shift MRI: the effect of simplified sampling protocols on accuracy.

BACKGROUND: The assessment of liver percentage fat fraction (%FF) using proton density fat fraction sequences is becoming increasingly accessible. Previous studies have tended to use multiple small ROIs that focus on Couinaud segments. In an effort to simplify day-to-day analysis, this study assesses the impact of using larger, elliptical ROIs focused on a single hepatic lobe. Additionally, we assess the impact of sampling fewer transhepatic slices when measuring %FF. METHODS: Retrospective analysis of prospectively obtained images from 34 volunteers using an IDEAL IQ sequence. Two observers independently measured %FF using three different protocols: freehand whole-liver ROI (fh-ROI), elliptical-ROI on the right lobe (rt-ROI) and elliptical-ROI on the left lobe (lt-ROI). RESULTS: Inter-observer reliability for all measurements techniques was 'excellent' (Spearman's rank correlation coefficients 0.81-0.98). There was a significant difference (Paired Wilcoxon Test: p < 0.001) between the median %FF obtained using fh-ROI when compared to the rt-ROI method, the maximum mean difference between the two techniques was 2.79% (95% CI). For all sampling methods a Kruskall-Wallis analysis demonstrated no significant difference in mean %FF when the number of slices sampled was reduced from 11 to 1. The mean coefficient of variance increased when more slices were sampled (3 slices = 0.1, 11 slices = 0.17, p < 0.001). CONCLUSION: Simplified ROIs focused on one hepatic lobe provide %FF measurements that are unlikely to be sufficiently accurate for use in clinical practice. Freehand whole-liver ROIs should be used in preference. A single freehand ROI measurement taken at the level of the hepatic hilum yields a %FF that is representative of the mean whole liver % FF. Multiple slices are needed to measure heterogeneity.

Primary care referral for knee MRI in the United Kingdom: Association with demography and subsequent surgical intervention.

BACKGROUND: Since 2008 primary care physicians (GPs) in our region have been allowed open access to knee MRI scans. There are questions about whether this changes referral practice and if it is an effective use of resources. PURPOSE: To describe the change in demographics of patients referred for knee MRI following implementation of a new referral pathway. STUDY TYPE: Retrospective observational study. POPULATION: All primary care referrals between 2008 and 2015 for knee MRI from a population of 900,000. FIELD STRENGTH/SEQUENCE: Not applicable. ASSESSMENT: Demographic profile and number of knee MRI referrals and subsequent arthroscopies. STATISTICAL TESTS: Comparisons between urban and rural populations used the t-test. Test for normality used Shapiro-Wilks. Comparison between abnormal MRI proportions used a chi-squared test. RESULTS: There were 23,928 knee MRI referrals (10,695 from GPs) between 2000 and 2015. MRI knee referrals rose from 210 in 2008 to 2379 in 2015. The average age of the patient decreased from 46.8 (SD = 14.9) in 2008 to 41.3 (SD = 14.7) in 2015. Conversion to arthroscopy declined from 15.4% to 10.2%, but there was no significant change in abnormal scan proportion. Conversion rates showed no significant difference between rural (9.6%) and urban populations (10.5%). Referral rates were significantly higher in low socioeconomic status areas (47.3% vs. 34.6%). The median referral rate per 1000 patients was 13.8 (interquartile range = 8.4). Referral rates varied widely between practices. DATA CONCLUSION: Despite a large rise in knee MRI referrals from primary care, there has been no substantial change in the age profile, suggesting that there has been no increase in inappropriate referral of elderly patients in whom MRI is unlikely to influence management. A modest decrease in the conversion rate to arthroscopy may be reasonably offset against a decrease in secondary care referrals. Socioeconomic status of the target population must be considered when planning primary care knee MRI services. LEVEL OF EVIDENCE: 4 Technical Efficacy Stage: 6 J. Magn. Reson. Imaging 2019.

Association of subchondral bone texture on magnetic resonance imaging with radiographic knee osteoarthritis progression: data from the Osteoarthritis Initiative Bone Ancillary Study.

OBJECTIVES: To assess whether initial or 12-18-month change in magnetic resonance imaging (MRI) subchondral bone texture is predictive of radiographic knee osteoarthritis (OA) progression over 36 months. METHODS: This was a nested case-control study including 122 knees/122 participants in the Osteoarthritis Initiative (OAI) Bone Ancillary Study, who underwent MRI optimised for subchondral bone assessment at either the 30- or 36-month and 48-month OAI visits. Case knees (n = 61) had radiographic OA progression between the 36- and 72-month OAI visits, defined as ≥ 0.7 mm minimum medial tibiofemoral radiographic joint space (minJSW) loss. Control knees (n = 61) without radiographic OA progression were matched (1:1) to cases for age, sex, body mass index and initial medial minJSW. Texture analysis was performed on the medial femoral and tibial subchondral bone. We assessed the association of texture features with radiographic progression by creating a composite texture score using penalised logistic regression and calculating odds ratios. We evaluated the predictive performance of texture features for predicting radiographic progression using c-statistics. RESULTS: Initial (odds ratio [95% confidence interval] = 2.13 [1.41-3.40]) and 12- 18-month change (3.76 [2.04-7.82]) texture scores were significantly associated with radiographic OA progression. Combinations of texture features were significant predictors of radiographic progression using initial (c-statistic [95% confidence interval] = 0.65 [0.64-0.65], p = 0.003) and 12-18-month change (0.68 [0.68-0.68], p < 0.001) data. CONCLUSIONS: Initial and 12-18-month changes in MRI subchondral bone texture score were significantly associated with radiographic progression at 36 months, with better predictive performance for 12-18-month change in texture. These results suggest that texture analysis may be a useful biomarker of subchondral bone in OA. KEY POINTS: • Subchondral bone MRI texture analysis is a promising knee osteoarthritis imaging biomarker. • In this study, subchondral bone texture was associated with knee osteoarthritis progression. • This demonstrates predictive and concurrent validity of MRI subchondral bone texture analysis. • This method may be useful in clinical trials with interventions targeting bone.

Test-retest reliability of rapid whole body and compartmental fat volume quantification on a widebore 3T MR system in normal-weight, overweight, and obese subjects.

PURPOSE: To measure the test-retest reliability of rapid (<15 min) whole body and visceral fat volume quantification in normal and obese subjects on a widebore 3T MR system and compare it with conventional manual segmentation. MATERIALS AND METHODS: Thirty participants (body mass index [BMI] 20.1-48.6 kg/m2 ) underwent two whole-body magnetic resonance imaging (MRI) examinations on a widebore 3T machine using a 2-point Dixon technique. Phase sensitive reconstruction and intensity inhomogeneity correction produced quantitative datasets of total adipose tissue (TAT), abdominal subcutaneous adipose tissue (ASAT), and visceral adipose tissue (VAT). The quantification was performed automatically using nonrigid atlas-based segmentation and compared with manual segmentation (SliceOmatic). RESULTS: The mean TAT was 31.74 L with a coefficient of variation (CV) of 0.79% and a coefficient of repeatability (CR) of 0.49 L. The ASAT was 7.92 L with a CV of 2.98% and a CR of 0.46 L. There was no significant difference in the semiautomated and manually segmented VAT (P = 0.73) but there were differences in the reliability of the two techniques. The mean semiautomated VAT was 2.56 L, CV 1.8%, and CR 0.09 L compared to the mean manually segmented VAT of 3.12 L, where the CV was 6.3% and the CR was 0.39 L. CONCLUSION: Rapid semiautomated whole body and compartmental fat volume quantification can be derived from a widebore 3T system, for a range of body sizes including obese patients, with "almost perfect" test-retest reliability. J. Magn. Reson. Imaging 2016;44:1464-1473.

Ultrashort TE evaluation of the osteochondral junction in vivo: a feasibility study.

OBJECTIVE: To determine whether differences in the osteochondral junction (OCJ) in two different age groups could be detected with ultrashort time-to-echo (UTE) MRI in vivo. METHODS: 10 healthy controls aged 20-30 years (Group 1) and 10 patients aged 40-50 years with knee pain but no evidence of osteoarthritis (OA) (Group 2) underwent 3-T MRI of the knee using a two-dimensional UTE sequence. Evaluation of the presence/absence of a high-signal-intensity (SI) line at the medial tibial/lateral tibial (MT/LT) OCJ was performed. Regions of interest (ROI) were created at the MT OCJ and LT OCJ. The peak OCJ SI ratio was calculated by measuring peak OCJ SI using averaged craniocaudal SI profiling, then dividing by the mean SI of a background ROI to standardize between studies. Groups were compared using χ(2) and Mann-Whitney U tests. RESULTS: A high SI line was present in significantly more Group 1 subjects at both MT (p < 0.001) and LT (p = 0.002). There was a significant difference (p < 0.001) in MT peak OCJ SI ratio between Group 1 (mean ± SD = 0.85 ± 0.10) and Group 2 (0.77 ± 0.12). There was no significant difference (p = 0.19) in LT peak OCJ SI ratio between Group 1 (0.81 ± 0.23) and Group 2 (0.80 ± 0.13). CONCLUSION: Significant differences in the UTE MR characteristics of the OCJ were demonstrated between the two age groups. ADVANCES IN KNOWLEDGE: Alterations in the UTE appearances of the tibial plateau OCJ in the older group with knee pain compared with a younger, healthy control cohort may reflect the very early stages of OA.

MRI texture analysis of subchondral bone at the tibial plateau.

OBJECTIVES: To determine the feasibility of MRI texture analysis as a method of quantifying subchondral bone architecture in knee osteoarthritis (OA). METHODS: Asymptomatic subjects aged 20-30 (group 1, n = 10), symptomatic patients aged 40-50 (group 2, n = 10) and patients scheduled for knee replacement aged 55-85 (group 3, n = 10) underwent high spatial resolution T1-weighted coronal 3T knee MRI. Regions of interest were created in the medial (MT) and lateral (LT) tibial subchondral bone from which 20 texture parameters were calculated. T2 mapping of the tibial cartilage was performed in groups 1 and 2. Mean parameter values were compared between groups using ANOVA. Linear discriminant analysis (LDA) was used to evaluate the ability of texture analysis to classify subjects correctly. RESULTS: Significant differences in 18/20 and 12/20 subchondral bone texture parameters were demonstrated between groups at the MT and LT respectively. There was no significant difference in mean MT or LT cartilage T2 values between group 1 and group 2. LDA demonstrated subject classification accuracy of 97 % (95 % CI 91-100 %). CONCLUSION: MRI texture analysis of tibial subchondral bone may allow detection of alteration in subchondral bone architecture in OA. This has potential applications in understanding OA pathogenesis and assessing response to treatment. KEY POINTS: • Improved techniques to monitor OA disease progression and treatment response are desirable • Subchondral bone (SB) may play significant role in the development of OA • MRI texture analysis is a method of quantifying changes in SB architecture • Pilot study showed that this technique is feasible and reliable • Significant differences in SB texture were demonstrated between individuals with/without OA.

Quantitative analysis of tibial subchondral bone: Texture analysis outperforms conventional trabecular microarchitecture analysis.

BACKGROUND: The aim of this study was to compare two different methods of quantitative assessment of tibial subchondral bone in osteoarthritis (OA): statistical texture analysis (sTA) and trabecular microarchitecture analysis (tMA). METHODS: Asymptomatic controls aged 20-30 (n = 10), patients aged 40-50 with chronic knee pain but without established OA (n = 10) and patients aged 55-85 with advanced OA scheduled for knee replacement (n = 10) underwent knee MR imaging at 3 Tesla with a three-dimensional gradient echo sequence to allow sTA and tMA. tMA and sTA features were calculated using region of interest creation in the medial (MT) and lateral (LT) tibial subchondral bone. Features were compared between groups using one-way analysis of variance. The two most discriminating tMA and sTA features were used to construct exploratory discriminant functions to assess the ability of the two methods to classify participants. RESULTS: No tMA features were significantly different between groups at either MT or LT. 17/20 and 11/20 sTA features were significantly different between groups at the MT/LT, respectively (P < 0.001). Discriminant functions created using tMA features classified 12/30 participants correctly (40% accuracy; 95% confidence interval [CI], 22-58%) based on MT data and 9/30 correctly (30%,; 95% CI, 14-46) based on LT data. Discriminant functions using sTA features classified 16/30 participants correctly (53%; 95% CI, 35-71) based on MT data and 14/30 correctly (47%; 95% CI, 29-65) based on LT data. CONCLUSION: sTA features showed more significant differences between the three study groups and improved classification accuracy compared with tMA features.

Pharmacokinetic modeling of multislice dynamic contrast-enhanced MRI in normal-healing radial fractures: A pilot study.

PURPOSE: To define the range of quantitative pharmacokinetic parameters in normal-healing bone with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). DCE-MRI is an established technique for characterizing abnormal tissue microvasculature within solid tumors, but has also shown promise for assessing bone and bone marrow. MATERIALS AND METHODS: In this study ethical approval for eight patients was obtained. Inclusion criteria were an extra-articular distal radial fracture in patients aged 20-50 years which had united by 6 weeks in plaster cast. This was assessed by an experienced orthopedic surgeon. DCE-MRI was performed at 1.5T 6 weeks after initial injury. The transfer constant (K(trans) ), transfer rate (Kep ), and initial area under the curve (IAUC) values for the fracture site and adjacent marrow were obtained for each patient. RESULTS: The mean T1 , K(trans) , Kep , and IAUC at the fracture site were 1713 (standard deviation [SD] 645), 0.09 (SD 0.07), 0.17 (SD 0.17) and 4.9 (SD 4.4). The relative standard deviation (RSD) for the fracture site ranged from 0.38 to 0.97 and for the adjacent marrow ranged from 0.95-3.88. Within each patient the range of RSDs was 0.04-0.42 for T1 , 0.26-0.91 for K(trans) , 0.14-1.06 for Kep , and 0.35-0.96 for the IAUC. CONCLUSION: Pharmacokinetic measures of perfusion can be obtained from healing fractures using DCE-MRI with "excellent" intraclass correlation coefficients for inter- and intrarater reliability. The use of these perfusion parameters is limited by wide patient-to-patient variation and slice-to-slice variation within patients.

MRI signal-based quantification of subchondral bone at the tibial plateau: a population study.

OBJECTIVE: To determine whether differences in subchondral sclerosis at the tibial plateau could be detected with magnetic resonance (MR) imaging in two different age groups. MATERIALS AND METHODS: This was a retrospective hypothesis-testing study. Thirty-two knees in group A (25-30 year olds) and 32 knees in group B (45-50 years old) were included. Participants had no MR features of osteoarthritis (OA). On coronal images, tibial articular cartilage thickness was measured, and regions of interest were created in the medial and lateral tibial plateau subchondral bone and in the tibial metaphysis. The measure of heterogeneity at the tibial plateaux was the ratio of the standard deviation of the signal in the medial/lateral compartment to the standard deviation of the signal in the metaphysis (ratio of standard deviations--RSS(medial)/RSS(lateral)). Differences between groups were assessed using unpaired Student's t-tests. RESULTS: Mean RSS(medial) was 2.61 (standard deviation, SD = 0.77) in group A and 2.97 (SD = 0.59) in group B. Mean RSS(lateral) in group A was 1.86 (SD = 0.63) and 1.89 (SD = 0.43) in group B. Mean total cartilage thickness (in mm) in group A was 3.38 (SD = 0.90) for the medial and 3.90 (SD = 1.09) for the lateral compartment and 3.44 (SD = 0.74) for the medial and 3.96 (SD = 0.96) for the lateral compartment in group B. The only parameter to show a statistically significant difference between groups was RSS(medial) (p = 0.04). CONCLUSION: A difference in medial subchondral bone sclerosis between two age groups was demonstrated in the absence of MR features of OA. This may represent the earliest OA change detectable on MR imaging.

Radiological evidence for the triple bundle anterior cruciate ligament.

The anterior cruciate ligament (ACL) has traditionally been described as having two bundles--one anteromedial and one posterolateral. This has been challenged by studies proposing the existence of a third, intermediate, bundle with distinct functional significance, an arrangement that has been described in a number of domesticated animal species. No radiological evidence for the triple bundle ACL has previously been described. A prevalence study was carried out on 73 consecutive human knee magnetic resonance (MR) studies to determine the number of visible bundles, excluding individuals with a history of ACL injury or mucoid degeneration. A triple bundle ACL was demonstrated in 15 out of 73 human knees (20.5%, 95% confidence interval 12.9-31.2%). This is the first radiological description of the human triple bundle ACL. There was MR imaging evidence of a triple bundle ACL in approximately one fifth of human knees in this study.

Test-retest reliability of automated whole body and compartmental muscle volume measurements on a wide bore 3T MR system.

PURPOSE: To measure the test-retest reproducibility of an automated system for quantifying whole body and compartmental muscle volumes using wide bore 3 T MRI. MATERIALS AND METHODS: Thirty volunteers stratified by body mass index underwent whole body 3 T MRI, two-point Dixon sequences, on two separate occasions. Water-fat separation was performed, with automated segmentation of whole body, torso, upper and lower leg volumes, and manually segmented lower leg muscle volumes. RESULTS: Mean automated total body muscle volume was 19·32 L (SD9·1) and 19·28 L (SD9·12) for first and second acquisitions (Intraclass correlation coefficient (ICC) = 1·0, 95% level of agreement -0·32-0·2 L). ICC for all automated test-retest muscle volumes were almost perfect (0·99-1·0) with 95% levels of agreement 1.8-6.6% of mean volume. Automated muscle volume measurements correlate closely with manual quantification (right lower leg: manual 1·68 L (2SD0·6) compared to automated 1·64 L (2SD 0·6), left lower leg: manual 1·69 L (2SD 0·64) compared to automated 1·63 L (SD0·61), correlation coefficients for automated and manual segmentation were 0·94-0·96). CONCLUSION: Fully automated whole body and compartmental muscle volume quantification can be achieved rapidly on a 3 T wide bore system with very low margins of error, excellent test-retest reliability and excellent correlation to manual segmentation in the lower leg. KEY POINTS: Sarcopaenia is an important reversible complication of a number of diseases. Manual quantification of muscle volume is time-consuming and expensive. Muscles can be imaged using in and out of phase MRI. Automated atlas-based segmentation can identify muscle groups. Automated muscle volume segmentation is reproducible and can replace manual measurements.

Impact of source data on the interpretation of contrast-enhanced magnetic resonance angiography of the lower limbs.

BACKGROUND: The primary purpose of this study is to examine whether use of source data is effective in increasing the number of arterial segments that can be interpreted from maximum intensity projections of lower limb MR angiograms. Correlation between sites of arterial disease and venous contamination was also measured. Interpretation of source data is performed routinely by radiologists, but the value of this has not been well studied with randomized studies. RESULTS: The proportion of segments visible above the knee was 87% using maximal intensity projection alone (MIP) and 88% when the MIP was combined with source data. The proportions were 67% for MIP and 72% for MIP plus source data below the knee. There was substantial agreement between presence of arterial disease and venous contamination in the calf and thigh. CONCLUSION: The use of source data increases the number of assessable segments, but not individuals, by a statistically significant but small amount (1.2%, p <0.05). This study supports the association between arterial disease and venous contamination.

Imaging Metal-on-Metal Hip Replacements: the Norwich Experience.

BACKGROUND: Adverse reaction to metal debris is a relatively recently described and often a silent complication of metal-on-metal (MOM) total hip replacements (THR). The Norfolk & Norwich University Hospital has been performing metal artefact reduction (MARS) MRI for 8 years in a variety of different types of MOM THR. QUESTIONS/PURPOSES: The aims of this review are to describe the experience of using MARS MRI in Norwich and to compare our experience with that published by other groups. METHODS: A MEDLINE keyword search was performed for studies including MRI in MOM THR. Relevant publications were reviewed and compared with published data from the Norfolk & Norwich University Hospital. The similarities and differences between these data were compared and possible explanations for these discussed. RESULTS: MARS MRI appears to be the most useful tool for diagnosing, staging and monitoring adverse reactions to metal debris (ARMD). There appears to be no clinically useful association between clinical and serological markers of disease and the severity of MR findings. Although severe early ARMD is associated with significant morbidity, mild disease is often stable for years. If patients with normal initial MR examinations develop ARMD, this usually occurs 7 years. A 1-year interval between MRI examinations is reasonable in asymptomatic patients. CONCLUSIONS: There is a general international consensus that ARMD is prevalent in symptomatic and asymptomatic patients with MOM THR and that while appearances vary with the type of prosthesis, there are characteristic features that make MARS MRI essential for diagnosis, staging and surveillance of the disease.

A case report: radiological findings in an unusual case of calciphylaxis 16 years after renal transplantation.

Calciphylaxis is a serious and potentially life-threatening disorder characterized by medial calcification of arterioles leading to subcutaneous ischemia and skin necrosis. It is most commonly seen in patients with end-stage renal disease or shortly after renal transplantation. We report an unusual case of calciphylaxis occurring 16 years after renal transplantation in a 48-year-old female with a failing graft, along with histological and striking radiological findings.