Faculty Bibliography

OBJECTIVE: Assess the diagnostic accuracy of 3-T indirect magnetic resonance arthrography (iMRA) for hip cartilage and labral pathology detection using arthroscopy as the reference standard and compare it to the published performance of direct magnetic resonance arthrography (dMRA). MATERIALS AND METHODS: Between 2009 and 2011, 290 patients suspected of having femoroacetabular impingement underwent iMRA. Our study group consisted of 41 of these patients (17 males, mean age 35 years; 24 females, mean age 33 years) who did not have a prior history of hip surgery and who subsequently underwent arthroscopy. Two experienced musculoskeletal radiologists separately evaluated the randomized and anonymized studies for the presence and quadrant location of labral and cartilage pathology. These recorded data were compared to arthroscopic reports. RESULTS: Forty-one patients had labral pathology, 34 patients had acetabular and 5 patients had femoral cartilage pathology at arthroscopy. Sensitivity, specificity, accuracy, negative- and positive-predictive values for labral lesion detection were respectively 98, 99, 99, 99 and 98 %; for acetabular cartilage lesion detection they were 69, 98, 89, 87 and 95 %; for femoral cartilage lesion detection they were 69, 95, 93 and 39 %. Sensitivities of iMRA by quadrant (anteroinferior, anterosuperior, posteroinferior, posterosuperior) for the labrum were 100.0, 95.0, NA and 85.7 %, for acetabular cartilage were NA, 58.8, NA and 39.5 % and for femoral cartilage were 50.0, 33.3, 75.0 and 75.0 %). NA indicates results not available because of the absence of findings in those quadrants. Specificities of iMRA by quadrant (anteroinferior, anterosuperior, posteroinferior, posterosuperior) for the labrum (95.0, 100.0, 95.1, 67.5 %), acetabular (100.0, 85.7, 92.6, 79.5 %) and femoral cartilage (100.0, 94.7, 96.2, 85.9 %). CONCLUSION: iMRA at 3 T is accurate in detecting labral pathology suggesting that it is a viable alternative to dMRA.

Three cases of PIN palsy following biceps repair are presented with clinical and imaging correlation. The imaging findings in these cases will be discussed and the orthopedic literature, as regards possible surgical approaches and technical factors believed to predispose to or prevent this complication, will be reviewed. It is important for radiologists to serve as consultants in these uncommon but sometimes devastating complications, helping to quickly and accurately recognize the imaging findings corresponding to the clinical symptoms and aiding the surgeon in diagnosis and treatment by identifying the possible causes and sites of nerve compression.

Purpose: A previous study has suggested that sonographic assessment of the acetabular labrum following intra-articular injection demonstrated concordance between sonographic and non-contrast MRI findings of labral pathology. However, the time interval between sonographic imaging andMRI varied significantly, and non-contrastMRI is less accurate in diagnosing labral tears than MR arthrography. We wish to verify whether such concordance exists when systematically compared to MRA performed on the same day. Material andMethods: Imaging from 26 patients who were referred for hip directMR arthrography with ultrasound guidance were retrospectively reviewed for this study. US-guided hip injection was performed with a 6 MHz curved transducer and a 3.5 inch, 22-gauge needle according to the department's standard protocol. A dilute gadolinium mixture of 10 cc of normal saline and 0.1 cc of gadolinium contrast and 2 cc of 1% lidocaine was administered in all cases. Routine post-injection ultrasound imaging examination of the anterosuperior labrum was performed from the iliopsoas tendon to the rectus femoris tendon using a linear 9 MHz transducer by an experienced MSK radiologist. Subsequently, patients proceeded directly to MR imaging. Same-day ultrasound and MRA images were retrospectively and blindly reviewed in random order by two experienced MSK radiologists after the studies were anonymized. The labrum for each study was divided into three anatomical zones: adjacent to iliopsoas tendon, adjacent to rectus femoris tendon, and between the two tendons. For each modality and anatomic zone, the labrum was given three binary numerical scores denoting the presence or absence of the following: intrasubstance labral cleft, chondrolabral junction cleft, and abnormal labrum morphology. The values for each labrum anatomical zone and pathology were then compared. MRA was considered the gold standard for diagnosing labral tears.
Result(s): The patient population consisted of 11 males and 15 females, mean age 33.5 years (standard deviation of 9.1 years). 11 injections were performed in the left hip and 15 were performed in the right hip. The mean body mass index (BMI) was 23.7 (standard deviation of 4.1). 4 patients were eventually taken to arthroscopy and theMRAfindings were confirmed. Given that the presence or absence of labral cleft, chondrolabral junction cleft, and abnormal morphology was included for each labrum anatomical zone, 234 data points were obtained for US and MRevaluation. US and MR showedmatching analysis in 124/234 (53%) of the data points. 3/26 (11.5%) patients had normal labrumMRA examinations. On a zonal basis, US was most accurate in detecting abnormal morphology (LR+ 1.59, LR- 0.388). US was also moderately accurate detecting labral clefts on a zone basis (LR+ 1.35, LR- 0.58). US called some form of pathology near the rectus femoris and between the tendons in all patients, with PPVof 0.577 and 0.692 in each zone respectively

OBJECTIVE: This study aimed at identifying the optimal threshold value to detect cartilage lesions with Standardized dGEMRIC at 3T and evaluate intra- and inter-observer repeatability. DESIGN: We retrospectively reviewed 20 hips in 20 patients. dGEMRIC maps were acquired at 3T along radial imaging planes of the hip and standardized to remove the effects of patient's age, sex and diffusion of gadolinium contrast. Two observers separately evaluated 84 Standardized dGEMRIC maps, both by visual inspection and using an average index for a region of interest in the acetabular cartilage. A radiologist evaluated the acetabular cartilage on morphologic MR images at exactly the same locations. Using intra-operative findings as reference, the optimal threshold to detect cartilage lesions with Standardized dGEMRIC was assessed and results were compared with the diagnostic performance of morphologic MRI. RESULTS: Using z < -2 as threshold and visual inspection of the color-adjusted maps, sensitivity, specificity and accuracy for Observer 1 and Observer 2, were 83%, 60% and 75%, and 69%, 70% and 69%, respectively. Overall performance was 52%, 67% and 58%, when using an average z for the acetabular cartilage, compared to 37%, 90% and 56% for morphologic assessment. The kappa coefficient was 0.76 and 0.68 for intra- and inter-observer repeatability, respectively, indicating substantial agreement. CONCLUSIONS: Standardized dGEMRIC at 3T is accurate in detecting cartilage damage and could improve preoperative assessment in FAI. As cartilage lesions in FAI are localized, visual inspection of the Standardized dGEMRIC maps is more accurate than an average z for the acetabular cartilage.

Healthy cartilage is essential for normal joint function, and osteoarthritis is the end result of cartilage injury. Hip osteoarthritis was once believed to be a disease of old age; however, younger individuals with femoroacetabular impingement have been found to have premature cartilage injury due to potentially treatable geometric hip joint abnormalities. Thus advanced knowledge of early cartilage damage in these individuals has the potential to affect their clinical course. Imaging provides methods for the noninvasive assessment of cartilage disease. Although much of imaging has been limited to the detection of physically evident abnormalities in cartilage, newer MR techniques are proving that it may be possible to assess the health of cartilage before physically evident damage is present. We review both the currently used morphologic techniques and emerging biochemical strategies used in the assessment of hip cartilage health.

The hip joint poses unique challenges at magnetic resonance (MR) imaging because of its shape and anatomic position. When conventional imaging planes are used, partial-volume averaging effects may substantially hamper the depiction of cartilage and labral damage at MR imaging. Such effects are most prevalent when the imaging plane is not perpendicular to the curvature of the joint and result in images that poorly depict or fail to depict cartilage and labral conditions. Partial-volume averaging, along with the inherently thin and closely apposed articular cartilage, may be partly to blame for the seemingly disparate reported sensitivities of MR imaging for depicting cartilage damage in the literature, which vary widely depending on whether arthrography was used. Fortunately, the multiplanar capability of MR imaging is not limited to standard anatomic planes. Radial sections, which are obtained perpendicular to the surfaces of the hip joint, provide a true cross section of the cartilage and labrum that conventional planes do not. Radial imaging is a reproducible technique that enhances the morphologic assessment of the articular cartilage and labrum. The additional information it provides is important because early damage occurs in the anterosuperior region of the hip in patients with femoroacetabular impingement. (c)RSNA, 2013.

Hip pain is a common but potentially vexing clinical problem; symptoms may be protean, referred, and poorly localized. History and physical examination can be unreliable in discriminating between intra-articular and extra-articular origins of pain. MR imaging augments clinical evaluation by providing information about the hip joint as well as the periarticular structures, which can be a source of symptoms. This article presents an anatomy-based review of common and less common tendon pathologies on MR imaging, which are considered in the differential diagnosis of hip pain.

OBJECTIVE: To validate a new method to analyze delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC) measurements in the hip for early assessment of cartilage defects in femoroacetabular impingement (FAI). METHODS: We performed a retrospective review of 10 hips in 10 FAI patients, who underwent hip arthroscopy. T(1)-weighted images and dGEMRIC T(1) maps were acquired at 1.5 T on coronal planes, including the anterior-superior, superior, posterior-superior hip cartilage. For all slices, a region of interest (ROI) was defined over the central portion of the femoral cartilage, assumed to be healthy, and T(1) values (x) were transformed to standard scores (z) using z = (x -mu)/sigma, where mu and sigma are the average and standard deviation of T(1) in the femoral ROI. Diagnostic performance of the resulting standardized dGEMRIC maps was evaluated against intraoperative findings and compared with that of a previously proposed dGEMRIC analysis as well as morphologic assessment. RESULTS: Assuming z = -2 or z = -3 as the threshold between normal and degenerated cartilage, sensitivity, specificity and accuracy were 88%, 51% and 62%, and 71%, 63% and 65%, respectively. By using T(1) = 500 ms as single threshold for all dGEMRIC T(1) maps, these values became 47%, 58% and 55%, whereas they were 47%, 79% and 70% for morphologic evaluation. CONCLUSIONS: Standardized dGEMRIC can increase the sensitivity in detecting abnormal cartilage in FAI and has the potential to improve the clinical interpretation of dGEMRIC measurements in FAI, by removing the effect of inter- and intra-patient T(1) variability.

PURPOSE: Several techniques used to measure ulnar variance on a posteroanterior wrist radiograph have been described. It remains unclear whether they accurately represent the true ulnar variance of the patient. The purpose of this study was to correlate ulnar variance measurements on plain radiographs, computed tomography (CT), magnetic resonance imaging (MRI), and anatomic dissection. METHODS: Posteroanterior (PA) radiographs, coronal and sagittal CT scans, and coronal MRI scans were obtained on 8 fresh-frozen cadaver wrists. The ulnar variance was measured by 5 reviewers. The specimens were then dissected, exposing the wrist joint. The ulnar variance was measured directly on each specimen using digital calipers. The inter-rater reliability was calculated for each imaging modality. The bias for each imaging modality was calculated using the digital caliper measurements as the true ulnar variance. RESULTS: Intraclass correlation coefficients demonstrated excellent inter-rater reliability for each imaging modality. The average bias from the true variance was the following: PA radiograph, 0.77 mm; coronal CT, 0.96 mm; sagittal CT, 0.96 mm; MRI with articular cartilage, 0.73 mm; MRI excluding cartilage, 0.49 mm. The variance measured on all imaging modalities tended to underestimate the magnitude of the true variance. CONCLUSIONS: Ulnar variance measured on coronal MRI best reflected the true ulnar variance as measured directly using calipers. The CT scans demonstrated the greatest deviation from the true variance. However, differences were small and might not be clinically meaningful. All imaging modalities demonstrated excellent inter-rater reliability, with MRI being highest. All imaging modalities tended to underestimate the magnitude of the true variance. CLINICAL RELEVANCE: The imaged underestimation of true ulnar variance should be taken into account when performing surgical procedures that alter the relative lengths of the radius and ulna.