Value of MR arthrography for evaluation of children and adolescents with clinically suspected intraarticular cause of hip pain.

PURPOSE: To evaluate the distribution of intra- and extraarticular MRI findings in children and adolescents with clinically suspected intraarticular cause of hip pain in order to assess the need for additional intraarticular contrast administration. MATERIAL AND METHODS: Database was searched over a period of 34 months retrospectively for consecutive hip MR arthrography in young patients (8-17 years) with suspected intraarticular cause of hip or groin pain. Exclusion criteria were prior hip surgery, follow-up examination due to known intraarticular pathology, incomplete examination, qualitatively non-diagnostic examinations, and missing informed consent. Reports of fellowship-trained MSK radiologists were searched for intraarticular versus extraarticular findings explaining hip or groin pain. RESULTS: Seventy patients (68% female; median age: 14.5 years; range:10.8-16.9 years) were analyzed. No reason for pain was found in 30 (42.9%) hips, extraarticular reasons in 20 (28.6%) cases, intraarticular in 14 (20.0%), and both (intra- and extraarticular) in 6 (8.6%) hips. Most common extraarticular reasons were apophysitis (14.3%), other bony stress reactions (12.9%), intramuscular edema (7%), tendinitis (5.7%), and trochanteric bursitis (4.3%). Labral pathology was the most common intraarticular finding (overall:34.3%; partial tear:15.7%, complete tear:15.7%), most frequent at the anterosuperior position (81.8%). Cartilage defects (1.4%), intraarticular neoplasia (1.4%), and tear of the femoral head ligament (2.8%) were rarely found. Synovitis and loose bodies were not observed. Cam-(37.1%) and pincer-configurations (47.1%) were common while hip dysplasia was rare (5.7%). CONCLUSION: MRI in children and adolescents with hip pain should be done primarily without intraarticular contrast administration since most cases show an extraarticular pain reason or no diagnosis detectable with MRI.

Improved estimates of strength and stiffness in pathologic vertebrae with bone metastases using CT-derived bone density compared with radiographic bone lesion quality classification.

OBJECTIVE: The aim of this study was to compare the ability of 1) CT-derived bone lesion quality (classification of vertebral bone metastases [BM]) and 2) computed CT-measured volumetric bone mineral density (vBMD) for evaluating the strength and stiffness of cadaver vertebrae from donors with metastatic spinal disease. METHODS: Forty-five thoracic and lumbar vertebrae were obtained from cadaver spines of 11 donors with breast, esophageal, kidney, lung, or prostate cancer. Each vertebra was imaged using microCT (21.4 µm), vBMD, and bone volume to total volume were computed, and compressive strength and stiffness experimentally measured. The microCT images were reconstructed at 1-mm voxel size to simulate axial and sagittal clinical CT images. Five expert clinicians blindly classified the images according to bone lesion quality (osteolytic, osteoblastic, mixed, or healthy). Fleiss' kappa test was used to test agreement among 5 clinical raters for classifying bone lesion quality. Kruskal-Wallis ANOVA was used to test the difference in vertebral strength and stiffness based on bone lesion quality. Multivariable regression analysis was used to test the independent contribution of bone lesion quality, computed vBMD, age, gender, and race for predicting vertebral strength and stiffness. RESULTS: A low interrater agreement was found for bone lesion quality (κ = 0.19). Although the osteoblastic vertebrae showed significantly higher strength than osteolytic vertebrae (p = 0.0148), the multivariable analysis showed that bone lesion quality explained 19% of the variability in vertebral strength and 13% in vertebral stiffness. The computed vBMD explained 75% of vertebral strength (p < 0.0001) and 48% of stiffness (p < 0.0001) variability. The type of BM affected vBMD-based estimates of vertebral strength, explaining 75% of strength variability in osteoblastic vertebrae (R2 = 0.75, p < 0.0001) but only 41% in vertebrae with mixed bone metastasis (R2 = 0.41, p = 0.0168), and 39% in osteolytic vertebrae (R2 = 0.39, p = 0.0381). For vertebral stiffness, vBMD was only associated with that of osteoblastic vertebrae (R2 = 0.44, p = 0.0024). Age and race inconsistently affected the model's strength and stiffness predictions. CONCLUSIONS: Pathologic vertebral fracture occurs when the metastatic lesion degrades vertebral strength, rendering it unable to carry daily loads. This study demonstrated the limitation of qualitative clinical classification of bone lesion quality for predicting pathologic vertebral strength and stiffness. Computed CT-derived vBMD more reliably estimated vertebral strength and stiffness. Replacing the qualitative clinical classification with computed vBMD estimates may improve the prediction of vertebral fracture risk.

CT-based and morphological comparison of glenoid inclination and version angles and mineralisation distribution in human body donors.

BACKGROUND: For optimal prosthetic anchoring in omarthritis surgery, a differentiated knowledge on the mineralisation distribution of the glenoid is important. However, database on the mineralisation of diseased joints and potential relations with glenoid angles is limited. METHODS: Shoulder specimens from ten female and nine male body donors with an average age of 81.5 years were investigated. Using 3D-CT-multiplanar reconstruction, glenoid inclination and retroversion angles were measured, and osteoarthritis signs graded. Computed Tomography-Osteoabsorptiometry (CT-OAM) is an established method to determine the subchondral bone plate mineralisation, which has been demonstrated to serve as marker for the long-term loading history of joints. Based on mineralisation distribution mappings of healthy shoulder specimens, physiological and different CT-OAM patterns were compared with glenoid angles. RESULTS: Osteoarthritis grades were 0-I in 52.6% of the 3D-CT-scans, grades II-III in 34.3%, and grade IV in 13.2%, with in females twice as frequently (45%) higher grades (III, IV) than in males (22%, III). The average inclination angle was 8.4°. In glenoids with inclination ≤10°, mineralisation was predominantly centrally distributed and tended to shift more cranially when the inclination raised to > 10°. The average retroversion angle was - 5.2°. A dorsally enhanced mineralisation distribution was found in glenoids with versions from - 15.9° to + 1.7°. A predominantly centrally distributed mineralisation was accompanied by a narrower range of retroversion angles between - 10° to - 0.4°. CONCLUSIONS: This study is one of the first to combine CT-based analyses of glenoid angles and mineralisation distribution in an elderly population. The data set is limited to 19 individuals, however, indicates that superior inclination between 0° and 10°-15°, and dorsal version ranging between - 9° to - 3° may be predominantly associated with anterior and central mineralisation patterns previously classified as physiological for the shoulder joint. The current basic research findings may serve as basic data set for future studies addressing the glenoid geometry for treatment planning in omarthritis.

Conventional finite element models estimate the strength of metastatic human vertebrae despite alterations of the bone's tissue and structure.

INTRODUCTION: Pathologic vertebral fractures are a major clinical concern in the management of cancer patients with metastatic spine disease. These fractures are a direct consequence of the effect of bone metastases on the anatomy and structure of the vertebral bone. The goals of this study were twofold. First, we evaluated the effect of lytic, blastic and mixed (both lytic and blastic) metastases on the bone structure, on its material properties, and on the overall vertebral strength. Second, we tested the ability of bone mineral content (BMC) measurements and standard FE methodologies to predict the strength of real metastatic vertebral bodies. METHODS: Fifty-seven vertebral bodies from eleven cadaver spines containing lytic, blastic, and mixed metastatic lesions from donors with breast, esophageal, kidney, lung, or prostate cancer were scanned using micro-computed tomography (µCT). Based on radiographic review, twelve vertebrae were selected for nanoindentation testing, while the remaining forty-five vertebrae were used for assessing their compressive strength. The µCT reconstruction was exploited to measure the vertebral BMC and to establish two finite element models. 1) a micro finite element (µFE) model derived at an image resolution of 24.5 µm and 2) homogenized FE (hFE) model derived at a resolution of 0.98 mm. Statistical analyses were conducted to measure the effect of the bone metastases on BV/TV, indentation modulus (Eit), ratio of plastic/total work (WPl/Wtot), and in vitro vertebral strength (Fexp). The predictive value of BMC, µFE stiffness, and hFE strength were evaluated against the in vitro measurements. RESULTS: Blastic vertebral bodies exhibit significantly higher BV/TV compared to the mixed (p = 0.0205) and lytic (p = 0.0216) vertebral bodies. No significant differences were found between lytic and mixed vertebrae (p = 0.7584). Blastic bone tissue exhibited a 5.8% lower median Eit (p< 0.001) and a 3.3% lower median Wpl/Wtot (p<0.001) compared to non-involved bone tissue. No significant differences were measured between lytic and non-involved bone tissues. Fexp ranged from 1.9 to 13.8 kN, was strongly associated with hFE strength (R2=0.78, p< 0.001) and moderately associated with BMC (R2=0.66, p< 0.001) and µFE stiffness (R2=0.66, p< 0.001), independently of the lesion type. DISCUSSION: Our findings show that tumour-induced osteoblastic metastases lead to slightly, but significantly lower bone tissue properties compared to controls, while osteolytic lesions appear to have a negligible impact. These effects may be attributed to the lower mineralization and woven nature of bone forming in blastic lesions whilst the material properties of bone in osteolytic vertebrae appeared little changed. The moderate association between BMC- and FE-based predictions to fracture strength suggest that vertebral strength is affected by the changes of bone mass induced by the metastatic lesions, rather than altered tissue properties. In a broader context, standard hFE approaches generated from CTs at clinical resolution are robust to the lesion type when predicting vertebral strength. These findings open the door for the development of FE-based prediction tools that overcomes the limitations of BMC in accounting for shape and size of the metastatic lesions. Such tools may help clinicians to decide whether a patient needs the prophylactic fixation of an impending fracture.

Postpartum Bone Marrow Edema at the Sacroiliac Joints May Mimic Sacroiliitis of Axial Spondyloarthritis on MRI.

OBJECTIVE: The objective of our study was to compare MRI findings in the sacroiliac joints of postpartum women (as a model of mechanical changes) and women with known axial spondyloarthritis (as an inflammatory model). SUBJECTS AND METHODS: For this prospective multicenter age-matched, case-control study, sacroiliac joint MRI examinations of 30 healthy women (mean age, 34.0 years) in the early postpartum period (mechanical group) and 30 age-matched women (mean age, 33.8 years) with known axial spondyloarthritis (retrospective inflammatory group) were compared. Blinded to clinical information, readers assessed MR images using the following scoring systems: Spondyloarthritis Research Consortium of Canada (SPARCC) MRI index, Berlin method, Assessment of Spondyloarthritis International Society (ASAS) criteria, and SPARCC MRI structural score. Descriptive statistics as percentages of the different findings (i.e., bone marrow edema [BME], erosion, fatty bone marrow replacement, backfill, ankylosis) and scores between groups and between delivery modes were compared. RESULTS: In the postpartum group, 63.3% (19/30) of women showed BME around the sacroiliac joints compared with 86.7% (26/30) of women in the spondyloarthritis group (based on ASAS criteria). Erosions were uncommon in the postpartum group (10.0% [3/30] postpartum vs 56.7% [17/30] spondyloarthritis). Fatty bone marrow replacement, backfill, and ankylosis were not seen in the postpartum group. In subjects with positive MRI findings for sacroiliitis based on ASAS criteria, the SPARCC MRI index (mean ± SD, 13.6 ± 14.5 vs 13.0 ± 10.7; p = 0.818) and Berlin method (4.5 ± 3.0 and 5.5 ± 3.5, p = 0.378) were not different between the postpartum and spondyloarthritis groups. Scores were not different between birth modalities. CONCLUSION: Pregnancy-induced BME at the sacroiliac joints, as a result of prolonged mechanical stress, was present in 63.3% of women who underwent MRI during the early postpartum period and may mimic sacroiliitis of axial spondyloarthritis.

Upright weight-bearing CT of the knee during flexion: changes of the patellofemoral and tibiofemoral articulations between 0° and 120°.

PURPOSE: To prospectively compare patellofemoral and tibiofemoral articulations in the upright weight-bearing position with different degrees of flexion using CT in order to gain a more thorough understanding of the development of diseases of the knee joint in a physiological position. MATERIALS AND METHODS: CT scans of the knee in 0°, 30°, 60° flexion in the upright weight-bearing position and in 120° flexion upright without weight-bearing were obtained of 10 volunteers (mean age 33.7 ± 6.1 years; range 24-41) using a cone-beam extremity-CT. Two independent readers quantified tibiofemoral and patellofemoral rotation, tibial tuberosity-trochlear groove distance (TTTG) and patellofemoral distance. Tibiofemoral contact points were assessed in relation to the anteroposterior distance of the tibial plateau. Significant differences between degrees of flexion were sought using Wilcoxon signed-rank test (P < 0.05). RESULTS: With higher degrees of flexion, internal tibiofemoral rotation increased (0°/120° flexion; mean, 0.5° ± 4.5/22.4° ± 7.6); external patellofemoral rotation decreased (10.6° ± 7.6/1.6° ± 4.2); TTTG decreased (11.1 mm ±3.7/-2.4 mm ±6.4) and patellofemoral distance decreased (38.7 mm ±3.0/21.0 mm ±7.0). The CP shifted posterior, more pronounced laterally. Significant differences were found for all measurements at all degrees of flexion (P = 0.005-0.037), except between 30° and 60°. ICC was almost perfect (0.80-0.99), except for the assessment of the CP (0.20-0.96). CONCLUSION: Knee joint articulations change significantly during flexion using upright weight-bearing CT. Progressive internal tibiofemoral rotation leads to a decrease in the TTTG and a posterior shift of the contact points in higher degrees of flexion. This elucidates patellar malalignment predominantly close to extension and meniscal tears commonly affecting the posterior horns.

Reliability of postoperative MR imaging in the determination of level and side of lumbar spinal decompression surgery.

Background Magnetic resonance imaging (MRI) is the diagnostic modality of choice in defining soft tissue compromise of the spinal canal. Purpose To evaluate the reliability of postoperative MRI in the determination of level and side of lumbar spinal decompression surgery, investigated by two reviewers, in different levels of training and specialization. Material and Methods Postoperative MR images of 86 patients who underwent spinal decompression (single level, n = 70; multilevel, n = 16; revision decompression, n = 9) were reviewed independently by an experienced musculoskeletal radiologist and a fourth-year orthopedic surgery resident. The level (single or multiple) and side of previous surgical decompression were determined and compared to the surgical notes. We examined factors that may have influenced the reliability, including demographics, type of surgical decompression, use of a drain, and time interval from surgery to MRI. Results Significantly fewer levels were correctly determined by the resident (77/86 cases, 89.5%) compared with the radiologist (84/86 cases, 97.7%) ( P = 0.014). The resident interpreted significantly more MR images incorrectly in cases where a drain was used (n = 8; P < 0.001). Re-decompression cases were interpreted incorrectly significantly more often by both the radiologist (n = 2, P = 0.032) and the resident (n = 4, P = 0.014). Conclusion Determination of the level and side operated on in previous lumbar spinal decompression surgery on MRI has a high reliability, especially when performed by a musculoskeletal radiologist. However, this reliability is decreased in cases involving surgical drainage and same-level revision surgery.

Partial supraspinatus tears are associated with tendon lengthening.

PURPOSE: Tendon tear may result in muscular retraction with the loss of contractile amplitude and strength of the rotator cuff muscles. Currently, neither a validated method of measuring supraspinatus tendon length nor normal values are known. It was therefore the purpose of this study to measure the normal length of the supraspinatus tendon and to determine whether partial tears are associated with changes in tendon length. METHODS: MR examinations of 49 asymptomatic volunteers and 37 patients with arthroscopically proven, isolated partial tears of the supraspinatus tendon were compared. The ratio of the extramuscular tendon length to the distance between the footprint and the glenoid surface was calculated (TL/FG ratio). Tendon length measurements were taken by two independent readers at the bursal and articular surfaces at the anterior, the central and the posterior parts of the tendon. RESULTS: TL/FG ratios at the bursal surface of tendons with partial tears were significantly higher than those in the control group [anterior: 0.78 ± 0.20 vs. 0.66 ± 0.15 (p < 0.05); central: 0.61 ± 0.13 vs. 0.52 ± 0.10 (p < 0.05); posterior: 0.57 ± 0.15 vs. 0.52 ± 0.10 (p < 0.05)]. At the articular surface, differences were significant only anteriorly [0.60 ± 0.13, vs. 0.54 ± 0.10 (p < 0.05)]. A cut-off TL/FG ratio of 0.63 for measurements at the bursal surface in the center of the tendon achieved a sensitivity of 46 % and a specificity of 92 % for the identification of partial cuff tearing. CONCLUSION: A reproducible method for measurement of extramuscular supraspinatus tendon length is described. Partial tearing of the supraspinatus tendon is associated with significant tendon lengthening, suggesting failure in continuity, and this is most reliably measured on the bursal surface. LEVEL OF EVIDENCE: III.

Good correlation of goutallier rating of supraspinatus fatty changes on axial and reformatted parasagittal computed tomographic images.

UNLABELLED: Traumatic tendon tear of the rotator cuff occurs frequently and leads to fatty muscle infiltration. With regard to the outcome, fatty infiltration of the rotator cuff muscles constitutes a major negative predictive factor after rotator cuff surgery. In 1989, Goutallier et al established his classification system for assessment of fatty infiltration of the rotator cuff muscles. He used computed tomographic (CT) images in the axial plane. Today, the assessment of rotator cuff muscles on axial CT images has been widely replaced by assessment on parasagittal acquired magnetic resonance images. This change raised 2 important questions. First, there is a controversy whether the Goutallier classification can simply be adopted for magnetic resonance imaging. The second question is whether the muscle assessment in the axial plane is interchangeable with that in the parasagittal plane. We hypothesize that the assessment of fatty muscle infiltration is the same on reformatted parasagittal CT images as on axial CT images METHODS: Three independent readers, 2 radiologists and one shoulder surgeon, rated fatty changes of the supraspinatus muscle on CT scans of 91 shoulders. Goutallier grades were assessed on axial and reformatted parasagittal CT images in 2 separate reading sessions. The paired t test was used to find differences between grading results on axial and reformatted parasagittal images. The Pearson correlation coefficient and weighted kappa statistics were used to quantify linear correlation, intrareader, and interreader agreement. RESULTS: Mean (SD) Goutallier grading among all readers was 0.80 (1.16) (range, 0-4) on axial images and 0.89 (1.05) (range, 004) on parasagittal reconstructions. We detected a trend toward a slightly higher Goutallier grading on parasagittal reconstructions; however, this result was not significant (P = 0.07). The Pearson correlation coefficient was 0.702 (P < 0.001). Weighted kappa statistics indicated a moderately good to good intrareader (range of weighted kappa, 0.53-0.62) and interreader (weighted kappa, axial images, 0.55; reformatted parasagittal images, 0.65) agreement. CONCLUSION: Grading of fatty infiltration of the supraspinatus muscle on parasagittal CT images is comparable with the standard Goutallier grading on axial images and is characterized by a moderately good to good intrareader and interreader agreement. Assessment of parasagittal images is characterized by a slightly higher interreader agreement and may therefore be the preferable modality.

Comparison of radiation dose, workflow, patient comfort and financial break-even of standard digital radiography and a novel biplanar low-dose X-ray system for upright full-length lower limb and whole spine radiography.

OBJECTIVE: To compare the radiation dose, workflow, patient comfort, and financial break-even of a standard digital radiography and a biplanar low-dose X-ray system. MATERIALS AND METHODS: A standard digital radiography system (Ysio, Siemens Healthcare, Erlangen, Germany) was compared with a biplanar X-ray unit (EOS, EOS imaging, Paris, France) consisting of two X-ray tubes and slot-scanning detectors, arranged at an angle of 90° allowing simultaneous vertical biplanar linear scanning in the upright patient position. We compared data of standing full-length lower limb radiographs and whole spine radiographs of both X-ray systems. RESULTS: Dose-area product was significantly lower for radiographs of the biplanar X-ray system than for the standard digital radiography system (e.g. whole spine radiographs; standard digital radiography system: 392.2 ± 231.7 cGy*cm(2) versus biplanar X-ray system: 158.4 ± 103.8 cGy*cm(2)). The mean examination time was significantly shorter for biplanar radiographs compared with standard digital radiographs (e.g. whole spine radiographs: 449 s vs 248 s). Patients' comfort regarding noise was significantly higher for the standard digital radiography system. The financial break-even point was 2,602 radiographs/year for the standard digital radiography system compared with 4,077 radiographs/year for the biplanar X-ray unit. CONCLUSION: The biplanar X-ray unit reduces radiation exposure and increases subjective noise exposure to patients. The biplanar X-ray unit demands a higher number of examinations per year for the financial break-even point, despite the lower labour cost per examination due to the shorter examination time.

A rare periosteal diaphyseal lesion of the ulna.

Periosteal lesions of the ulna diaphysis are rare, include a wide spectrum of tumors, and may cause considerable diagnostic problems. Surgical treatment may vary widely, based on an accurate diagnosis. We present the case of a periosteal, extraskeletal low grade myxoid chondrosarcoma of the ulna diaphysis. The surgical therapy included an en-bloc resection with allograft reconstruction. The patient showed a favorable outcome. Careful preoperative evaluation and planning are imperative to obtain a satisfactory oncological and functional outcome, especially with uncommon tumor presentations at rare locations.

Magnetic resonance histologic correlation in rotator cuff tendons.

PURPOSE: To relate histologic changes in rotator cuff tendons to the appearance on T1-weighted as well as fat-suppressed T2-weighted and proton density-weighted magnetic resonance imaging (MRI) sequences. MATERIALS AND METHODS: T1-weighted, fat-suppressed T2-weighted and fat-suppressed proton density-weighted sequences of 18 cadaveric shoulders were acquired. The supraspinatus, infraspinatus, and subscapularis tendons were evaluated histologically. Twenty-six abnormalities were found in 23 of 37 tendons. In addition, histologically normal tendon parts (n = 32), including three segments with normal histology but abnormal MR signal, considered to represent magic angle effects, were defined. All regions of interest (ROIs) were evaluated by two musculoskeletal radiologists independently and blinded to histology. RESULTS: In the 26 areas with anatomically intact tendons but abnormal histological findings mucoid degeneration (n = 13), chondroid metaplasia (n = 11), fatty infiltration (n = 1), and foreign-body granuloma (n = 1) after tendon suture were found. Compared to normal tendon, mucoid degeneration was hyperintense on T2-weighted fat-suppressed (P = 0.007) and on proton density-weighted fat-suppressed images (P = 0.006). Chondroid metaplasia was hyperintense compared to normal tendon in all sequences (P < 0.05). Mucoid degeneration was hypointense compared to chondroid metaplasia on T2-weighted fat-suppressed images (P = 0.038) and hypointense compared to magic angle artifacts on T1-weighted images (P = 0.046). CONCLUSION: Chondroid metaplasia of rotator cuff tendons appears to be more common than expected. Both mucoid degeneration and chondroid metaplasia may explain increased tendon signal on MR images of the rotator cuff.

Shoulder arthroplasty.

Shoulder prostheses are now commonly used. Clinical results and patient satisfaction are usually good. The most commonly used types are humeral hemiarthroplasty, unconstrained total shoulder arthroplasty, and semiconstrained inversed shoulder prosthesis. Complications of shoulder arthroplasty depend on the prosthesis type used. The most common complications are prosthetic loosening, glenohumeral instability, periprosthetic fracture, rotator cuff tears, nerve injury, infection, and deltoid muscle dysfunction. Standard radiographs are the basis of both pre- and postoperative imaging. Skeletal scintigraphy has a rather limited role because there is overlap between postoperative changes which may persist for up to 1 year and early loosening and infection. Sonography is most commonly used postoperatively in order to demonstrate complications (hematoma and abscess formation) but may also be useful for the demonstration of rotator cuff tears occurring during follow-up. CT is useful for the demonstration of bone details both pre- and postoperatively. MR imaging is mainly used preoperatively, for instance for demonstration of rotator cuff tears.

Chronic recurrent multifocal osteomyelitis (CRMO) with symmetric involvement of both femora: X-ray, bone scintigram, and MR imaging findings in one case.

The case of a 17-month-old boy with symmetric involvement of both femora in chronic recurrent multifocal osteomyelitis (CRMO) is presented. Imaging showed an extraordinary involvement of both femoral diaphyses and distal metaphyses with extensive lamellar-like periosteal reactions. Diagnosis was based upon laboratory tests, bone scintigraphy, and MRI findings and was proved by open bone biopsy.