Faculty Bibliography

OBJECTIVE. The purpose of this article is to review the current understanding of the underlying pathophysiology of the Hill-Sachs lesion and anterior glenoid bone loss and to discuss the role of imaging in identifying and accurately describing these injuries. CONCLUSION. Understanding the underlying mechanics of anterior shoulder instability that result in Hill-Sachs lesions and glenoid bone loss, the strengths and weaknesses of the different imaging modalities ordered for their evaluation, and the methods used to characterize these osseous injuries on imaging are essential for the radiologist in this clinical setting.

PURPOSE: The authors describe their initial experience in implementing an integrated radiology reading room within a urologic oncology clinic, including the frequency and nature of clinician consultations and the perceived impact on patient management by clinicians. METHODS: A radiology reading room was established within an office-based urologic oncology clinic in proximity to the surgeon's work area. A radiologist was present in this reading room for a 3-hour shift each day. The frequency and nature of consultations during these shifts were recorded. Also, the clinic's staff completed a survey assessing perceptions of the impact of the integrated reading room on patient management. RESULTS: One hundred two consultations occurred during 57 included dates (average, 1.8 consultations per shift): 52% for review of external cases brought in by patients on discs, 43% for review of internal cases, and 5% for direct review by the radiologist of imaging with patients. The maximum number of consultations during a single shift was 8. All of the clinic's urologists indicated that >90% of consultations benefited patient care. The clinicians indicated tendencies to view consultations as affecting management in the majority of cases, to be more likely to seek consultation for outside imaging when the radiologist was on site, and to be less likely to repeat outside imaging when the radiologist was on site. CONCLUSIONS: The integrated reading room within the clinic has potential to improve the quality of care, for instance by facilitating increased review of outside imaging studies and thereby potentially reducing duplicate ordering and by enabling occasional direct image review with patients by radiologists.

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.

OBJECTIVE: To assess the ability of 3D MR shoulder reconstructions to accurately quantify glenoid bone loss in the clinical setting using findings at the time of arthroscopy as the gold standard. MATERIALS AND METHODS: Retrospective review of patients with MR shoulder studies that included 3D MR reconstructions (3D MR) produced using an axial Dixon 3D-T1W-FLASH sequence at our institution was conducted with the following inclusion criteria: history of anterior shoulder dislocation, arthroscopy (OR) performed within 6 months of the MRI, and an estimate of glenoid bone loss made in the OR using the bare-spot method. Two musculoskeletal radiologists produced estimates of bone loss along the glenoid width, measured in mm and %, on 3D MR using the best-fit circle method, which were then compared to the OR measurements. RESULTS: There were a total of 15 patients (13 men, two women; mean age, 28, range, 19-51 years). There was no significant difference, on average, between the MRI (mean 3.4 mm/12.6 %; range, 0-30 %) and OR (mean, 12.7 %; range, 0-30 %) measurements of glenoid bone loss (p = 0.767). A 95 % confidence interval for the mean absolute error extended from 0.45-2.21 %, implying that, when averaged over all patients, the true mean absolute error of the MRI measurements relative to the OR measurements is expected to be less than 2.21 %. Inter-reader agreement between the two readers had an IC of 0.92 and CC of 0.90 in terms of percentage of bone loss. CONCLUSIONS: 3D MR reconstructions of the shoulder can be used to accurately measure glenoid bone loss.

OBJECT: Our objective was to use 7 T MRI to compare cartilage morphology (thickness) and collagen composition (T2 values) in cartilage repair patients and healthy controls. MATERIALS AND METHODS: We scanned the knees of 11 cartilage repair patients and 11 controls on a 7 T MRI scanner using a high-resolution, gradient-echo sequence to measure cartilage thickness and a multi-echo spin-echo sequence to measure cartilage T2 values. We used two-tailed t tests to compare cartilage thickness and T2 values in: repair tissue (RT) versus adjacent cartilage (AC); RT versus healthy control cartilage (HC); AC versus HC. RESULTS: Mean thickness in RT, AC, HC were: 2.2 +/- 1.4, 3.6 +/- 1.1, 3.3 +/- 0.7 mm. Differences in thickness between RT-AC (p = 0.01) and RT-HC (p = 0.02) were significant, but not AC-HC (p = 0.45). Mean T2 values in RT, AC, HC were: 51.6 +/- 7.6, 40.0 +/- 4.7, 45.9 +/- 3.7 ms. Differences in T2 values between RT-AC (p = 0.0005), RT-HC (p = 0.04), and AC-HC (p = 0.004) were significant. CONCLUSION: 7 T MRI allows detection of differences in morphology and collagen architecture in: (1) cartilage repair tissue compared to adjacent cartilage and (2) cartilage repair tissue compared to cartilage from healthy controls. Although cartilage adjacent to repair tissue may be normal in thickness, it can demonstrate altered collagen composition.

Objective: To determine the accuracy of MR imaging for the evaluation of the subscapularis tendon as well as define imaging findings that will increase accuracy. MATERIALS AND METHODS: Retrospective review of the MR and operative (OR) reports of 286 patients was conducted and reviewed for the presence/degree (partial (PT)/full-thickness (FT)) of tearing; only PT articular tears were included. The presence of a supraspinatus tear and time interval between surgery and MRI were also documented. All of the PT tears called on MRI were also reviewed to see if there was a statistically significant association between certain imaging characteristics and the presence of a tear in surgery. Statistical analysis included 95 % confidence intervals, Fisher's exact, and exact Mann-Whitney tests. RESULTS: A total of 244 patients were included in the study with a total of 25 subscapularis tears, 16 PT and nine FT, and 219 intact tendons in arthroscopy; 20/25 tears and 200 intact sensitivity of 80%, specificity of 91%, accuracy of 90%, positive predictive value of 51%, and negative predictive value of 98 %. There was a significant association between the presence of a PT tear during arthroscopy and fluid-like signal within the tendon on more than one imaging plane (p<0.001) with an accuracy of 90%. CONCLUSIONS: This study reflects a musculoskeletal radiology section's experience with the diagnosis of subscapularis tendon pathology, demonstrating that MRI could be used to accurately evaluate the subscapularis tendon. An understanding of certain imaging pitfalls and the presence of fluid-like signal on multiple imaging planes should increase the diagnostic accuracy of the radiologist evaluating the subscapularis tendon for the presence of a tear.

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.

OBJECTIVE. The purpose of this study was to define and correlate the appearance of the rotator cable on MRI with arthroscopy, band-saw cadaveric sections, and histology. MATERIALS AND METHODS. Two cadaveric shoulders underwent 3-T MRI, band-sawing, and histologic evaluation. Three readers evaluated the MRI for the presence of the cable, and the same readers and a pathologist reviewed the macroscopic and microscopic specimens for a structure that corresponded to the cable. Cadaver 1 underwent arthroscopic evaluation to evaluate for the presence of a cable. Seventy consecutive shoulders that underwent 1.5- or 3-T MRI were also reviewed for the presence of the cable and evaluation of its characteristics (location, thickness, and width). RESULTS. A linear band of hypointense signal intensity was found along the undersur-face of the supraspinatus and infraspinatus tendons on both cadaveric MR images, which correlated to a linear band of tissue in the same location on macroscopic and microscopic evaluation and linear thickening along the cuff articular surface on arthroscopy consistent with the cable. The cable was seen in 74.3% of the MRI studies in both sagittal and coronal planes with a mean (+/- SD) distance of the cable from the medial margin of the enthesis of 1.33 +/- 0.27 cm, a mean width of the cable of 1.24 +/- 0.31 cm, and a mean thickness of 0.19 +/- 0.05 cm. CONCLUSION. The rotator cable is a structure that can be consistently seen on gross anatomic and histologic analysis, arthroscopy, and MRI in the intact rotator cuff. Familiarity with the typical location and morphology of the cable may allow easier characterization of disease that can involve the cable, such as rotator cuff tears.

Micro-finite element analysis applied to high-resolution (0.234-mm length scale) MRI reveals greater whole and cancellous bone stiffness, but not greater cortical bone stiffness, in the distal femur of female dancers compared to controls. Greater whole bone stiffness appears to be mediated by cancellous, rather than cortical bone adaptation. INTRODUCTION: The purpose of this study was to compare bone mechanical competence (stiffness) in the distal femur of female dancers compared to healthy, relatively inactive female controls. METHODS: This study had institutional review board approval. We recruited nine female modern dancers (25.7 +/- 5.8 years, 1.63 +/- 0.06 m, 57.1 +/- 4.6 kg) and ten relatively inactive, healthy female controls matched for age, height, and weight (32.1 +/- 4.8 years, 1.6 +/- 0.04 m, 55.8 +/- 5.9 kg). We scanned the distal femur using a 7-T MRI scanner and a three-dimensional fast low-angle shot sequence (TR/TE = 31 ms/5.1 ms, 0.234 mm x 0.234 mm x 1 mm, 80 slices). We applied micro-finite element analysis to 10-mm-thick volumes of interest at the distal femoral diaphysis, metaphysis, and epiphysis to compute stiffness and cross-sectional area of whole, cortical, and cancellous bone, as well as cortical thickness. We applied two-tailed t-tests and ANCOVA to compare groups. RESULTS: Dancers demonstrated greater whole and cancellous bone stiffness and cross-sectional area at all locations (p < 0.05). Cortical bone stiffness, cross-sectional area, and thickness did not differ between groups (>0.08). At all locations, the percent of intact whole bone stiffness for cortical bone alone was lower in dancers (p < 0.05). Adjustment for cancellous bone cross-sectional area eliminated significant differences in whole bone stiffness between groups (p > 0.07), but adjustment for cortical bone cross-sectional area did not (p < 0.03). CONCLUSIONS: Modern dancers have greater whole and cancellous bone stiffness in the distal femur compared to controls. Elevated whole bone stiffness in dancers may be mediated via cancellous, rather than cortical bone adaptation.