Bone Tissue in Magnetic Resonance Imaging: Contribution of New Zero Echo Time Sequences.

The introduction of new ultrashort and zero echo time (ZTE) sequences is revolutionizing magnetic resonance imaging (MRI) and optimizing patient management. These sequences acquire signals in tissues with very short T2: mineralized bone, cortical bone, and calcium deposits. They can be added to a classic MRI protocol. ZTE MRI provides computed tomography-like contrast for bone.

The yield of a positive MRI of the spine as imaging criterion in the ASAS classification criteria for axial spondyloarthritis: results from the SPACE and DESIR cohorts.

OBJECTIVES: To assess the prevalence of spinal inflammation on MRI in patients with chronic back pain (CBP) of maximally 3 years duration and to evaluate the yield of adding a positive MRI-spine as imaging criterion to the Assessment of SpondyloArthritis international Society (ASAS) classification criteria for axial spondyloarthritis (axSpA). METHODS: Baseline imaging of the sacroiliac joints (X-SI), MRI of the sacroiliac joints (MRI-SI) and MRI-spine were scored by ≥2 experienced central readers per modality in the SPondyloArthritis Caught Early (SPACE) and DEvenir des Spondylarthropathies Indifférenciées Récentes (DESIR) cohorts. Inflammation suggestive of axSpA was assessed in the entire spine. A positive MRI-spine was defined by the presence of ≥5 inflammatory lesions. Alternative less strict definitions were also tested. RESULTS: In this study, 541 and 650 patients with CBP from the SPACE and DESIR cohorts were included. Sacroiliitis on X-SI and MRI-SI was found in 40/541 (7%) and 76/541 (14%) patients in SPACE, and in DESIR in 134/650 (21%) and 231/650 (36%) patients, respectively. In SPACE and DESIR, a positive MRI-spine was seen in 4/541 (1%) and 48/650 (7%) patients. Of the patients without sacroiliitis on imaging, 3/447 (1%) (SPACE) and 8/382 (2%) (DESIR) patients had a positive MRI-spine. Adding positive MRI-spine as imaging criterion led to new classification in only one patient in each cohort, as the other patients already fulfilled the clinical arm. Other definitions of a positive MRI-spine yielded similar results. CONCLUSION: In two cohorts of patients with CBP with a maximum symptom duration of 3 years, a positive MRI-spine was rare in patients without sacroiliitis on MRI-SI and X-SI. Addition of MRI-spine as imaging criterion to the ASAS axSpA criteria had a low yield of newly classified patients and is therefore not recommended.

Can we use structural lesions seen on MRI of the sacroiliac joints reliably for the classification of patients according to the ASAS axial spondyloarthritis criteria? Data from the DESIR cohort.

OBJECTIVES: Investigating the utility of adding structural lesions seen on MRI of the sacroiliac joints to the imaging criterion of the Assessment of SpondyloArthritis (ASAS) axial SpondyloArthritis (axSpA) criteria and the utility of replacement of radiographic sacroiliitis by structural lesions on MRI. METHODS: Two well-calibrated readers scored MRI STIR (inflammation, MRI-SI), MRI T1-w images (structural lesions, MRI-SI-s) and radiographs of the sacroiliac joints (X-SI) of patients in the DEvenir des Spondyloarthrites Indifférenciées Récentes cohort (inflammatory back pain: ≥3 months, <3 years, age <50). A third reader adjudicated MRI-SI and X-SI discrepancies. Previously proposed cut-offs for a positive MRI-SI-s were used (based on <5% prevalence among no-SpA patients): erosions (E) ≥3, fatty lesions (FL) ≥3, E/FL ≥5. Patients were classified according to the ASAS axSpA criteria using the various definitions of MRI-SI-s. RESULTS: Of the 582 patients included in this analysis, 418 fulfilled the ASAS axSpA criteria, of which 127 patients were modified New York (mNY) positive and 134 and 75 were MRI-SI-s positive (E/FL≥5) for readers 1 and 2, respectively. Agreement between mNY and MRI-SI-s (E/FL≥5) was moderate (reader 1: κ: 0.39; reader 2: κ: 0.44). Using the E/FL≥5 cut-off instead of mNY classification did not change in 478 (82.1%) and 469 (80.6%) patients for readers 1 and 2, respectively. Twelve (reader 1) or ten (reader 2) patients would not be classified as axSpA if only MRI-SI-s was performed (in the scenario of replacement of mNY), while three (reader 1) or six (reader 2) patients would be additionally classified as axSpA in both scenarios (replacement of mNY and addition of MRI-SI-s). Similar results were seen for the other cut-offs (E≥3, FL≥3). CONCLUSIONS: Structural lesions on MRI can be used reliably either as an addition to or as a substitute for radiographs in the ASAS axSpA classification of patients in our cohort of patients with short symptom duration.

What is the reliability of non-trained investigators in recognising structural MRI lesions of sacroiliac joints in patients with recent inflammatory back pain? Results of the DESIR cohort.

OBJECTIVE: The objective of this study was to evaluate the reliability of recognising structural lesions on MRI (erosions, fatty lesions, ankylosis) of the sacroiliac joints (MRI-SIJ) in clinical practice compared to a central reading in patients with a possible recent axial spondyloarthritis (axSpA). METHODS: Patients aged 18-50 years, with recent (<3 years) and chronic (≥3 months) inflammatory back pain, suggestive of axSpA were included in the DEvenir des Spondyloarthrites Indifférenciées Récentes (DESIR) cohort. MRI-SIJ structural lesions were scored by non-trained local readers, and by two trained central readers. Local readers scored each SIJ as normal, doubtful or definite lesions. Central readers scored separately each type of lesion. The central reading (mean of the two central readers' scores) was the external standard. Agreement (κ) was calculated first between local (3 definitions of a positive MRI-SIJ) and central readings (9 definitions), and then between the two central readers. RESULTS: 664/708 patients with complete available images were included. Agreements between local and central readings were overall 'fair', except when considering at least 2 or 3 fatty lesions and at least 3 erosions and/or fatty lesions where agreement was 'moderate'. Agreement between central readers was similar. MRI-SIJ was positive for 52.6% of patients according to central reading (at least 1 structural lesion) and for 35.4% of patients according to local reading (at least unilateral 'doubtful' or 'definite' structural lesions). CONCLUSIONS: Agreement on a positive structural MRI-SIJ was fair to moderate between local and central readings, as well as between central readers. The reliability improved when fatty lesions were considered. TRIAL REGISTRATION NUMBER: NCTO 164 8907.

Rate and Predisposing Factors for Sacroiliac Joint Radiographic Progression After a Two-Year Follow-up Period in Recent-Onset Spondyloarthritis.

OBJECTIVE: To evaluate the rate of radiographic structural progression in the sacroiliac (SI) joints in patients with radiographic or nonradiographic axial spondyloarthritis (SpA), and to determine factors predisposing to such progression, over 2 years. METHODS: Patients with recent-onset axial SpA (from the Devenir des Spondyloarthropathies Indifferérenciées Récentes cohort) were assigned a radiographic SI joint score according to the modified New York criteria. Demographic characteristics, smoking status, HLA-B27 positivity, inflammation on magnetic resonance imaging (MRI) of the SI joints, disease activity, and treatment were investigated as potential predisposing factors. The main analysis consisted of the evaluation of the switch from nonradiographic to radiographic axial SpA, but other definitions of radiographic progression were also evaluated. RESULTS: Of the 708 patients enrolled, 449 had baseline and 2-year pelvic radiographs. Of these patients, 47% were men. Their mean ± SD age was 34 ± 9 years, 61% were B27 positive, and 37% had inflammation of the SI joints on MRI. The percentages of patients who switched from nonradiographic to radiographic axial SpA (4.9% [16 of 326]) and from radiographic to nonradiographic axial SpA (5.7% [7 of 123]) were low. The mean ± SD change in the total SI joint score (range 0-8) was small (0.1 ± 0.8) but highly significant (P < 0.001). The potential baseline predisposing factors for meeting the modified New York criteria in the multivariate analysis were current smoking, HLA-B27 positivity, and inflammation of the SI joints on MRI, with odds ratios of 3.3 (95% confidence interval [95% CI] 1.0-11.5], 12.6 (95% CI 2.3-274), and 48.8 (95% CI 9.3-904), respectively. CONCLUSION: Our findings suggest that structural progression does exist in early SpA, but it is quite small and observed in a small number of patients, and that environmental (smoking status), genetic (HLA-B27 positivity), and inflammation (inflammation of the SI joints on MRI) markers might be independent predisposing factors for progression.

Fat Suppression with Dixon Techniques in Musculoskeletal Magnetic Resonance Imaging: A Pictorial Review.

Dixon techniques are part of the methods used to suppress the signal of fat in MRI. They present many advantages compared with other fat suppression techniques including (1) the robustness of fat signal suppression, (2) the possibility to combine these techniques with all types of sequences (gradient echo, spin echo) and different weightings (T1-, T2-, proton density-, intermediate-weighted sequences), and (3) the availability of images both with and without fat suppression from one single acquisition. These advantages have opened many applications in musculoskeletal imaging. We first review the technical aspects of Dixon techniques including their advantages and disadvantages. We then illustrate their applications for the imaging of different body parts, as well as for tumors, neuromuscular disorders, and the imaging of metallic hardware.

Classification of axial SpA based on positive imaging (radiographs and/or MRI of the sacroiliac joints) by local rheumatologists or radiologists versus central trained readers in the DESIR cohort.

OBJECTIVE: Investigating changes in patient classification (ASAS (Assessment of SpondyloArthritis international Society) axSpA criteria) based on evaluation of images of the sacro-iliac joints (MRI-SI and X-SI) by local and central readers. METHODS: The DESIR cohort included patients with inflammatory back pain (IBP; ≥3 months, but <3 years), suggestive of axSpA. Local radiologists/rheumatologists (local-reading) and two central readers (central-reading) evaluated baseline images. Agreement regarding positive MRI (pos-MRI) between central readers and between local-reading and central-reading was calculated (κs). Number of patients classified differently (ASAS criteria) by using local-reading instead of central-reading was calculated. RESULTS: Inter-reader agreement between the two central readers and between local-reading and central-reading was substantial (κ=0.73 and κ=0.70, respectively). In 89/663 MRI-SIs (13.4%) local-reading and central-reading disagreed; 38/223 patients (17.0%) with pos-MRI (local-reading) were negative by central-reading; 51/440 patients (11.6%) with neg-MRI (local-reading) were positive by central-reading.In 163/582 patients eligible for applying ASAS criteria (28.0%), local-reading and central-reading disagreed on positive imaging (MRI-SI and/or X-SI; κ=0.68). In 46/582 patients (7.9%) a different evaluation resulted in a different classification; 18/582 patients (3.1%) classified no-SpA (central-reading) were axSpA by local-reading; 28/582 patients (4.8%) classified axSpA (central-reading) were no-SpA by local-reading. Among axSpA patients (central-reading), 16/419 patients (3.8%) fulfilling imaging-arm by central-reading fulfilled clinical-arm by local-reading; 29/419 patients (6.9%) fulfilling clinical-arm by central-reading fulfilled also imaging-arm by local-reading. CONCLUSIONS: In patients with recent onset IBP, trained readers and local rheumatologists/radiologists agree well on recognising a pos-MRI. While disagreeing in 28% of the patients on positive imaging (MRI-SI and/or X-SI), classification of only 7.9% of the patients changed based on a different evaluation of images, showing the ASAS axSpA criteria's robustness.

Is superolateral Hoffa fat pad edema a consequence of impingement between lateral femoral condyle and patellar ligament?

PURPOSE: To evaluate whether knee extensor mechanism features are associated with superolateral Hoffa fat pad edema at magnetic resonance imaging. MATERIALS AND METHODS: Institutional review board approval and written consent from all patients were obtained. Patients with superolateral Hoffa fat pad edema (n = 30) and a control group without edema of the fat pad (n = 60) were evaluated prospectively with magnetic resonance (MR) imaging. Demographic data and extensor mechanism features were compared, including trochlear depth, lateral trochlear inclination, patellar tilt angle, patellar height ratio, distance between patellar ligament and lateral trochlear facet, distance from the tibial tubercle to the trochlear groove, patellar facet asymmetry, and patellar ligament abnormalities. RESULTS: The following variables were associated with superolateral Hoffa fat pad edema in the multivariable models: patellar height ratio (P = .023), shortest distance between patellar ligament and lateral trochlear facet (P < .001), and distance from the tibial tubercle to the trochlear groove (P = .046). Of all demographic and degenerative variables, only age was significantly associated, with younger patients more likely to have superolateral Hoffa fat pad edema (P < .009). CONCLUSION: A high-riding patella, a short distance between the patellar ligament and the lateral trochlear facet, and an increased distance from the tibial tubercle to the trochlear groove are associated with superolateral Hoffa fat pad edema at MR imaging. These results are suggestive of impingement between the lateral femoral condyle and the posterior aspect of the patellar ligament in these patients.

Results of 32 allograft-prosthesis composite reconstructions of the proximal femur.

UNLABELLED: The use of allograft-prosthesis composites for reconstruction after bone tumor resection at the proximal femur has generated considerable interest since the mid1980s on the basis that their use would improve function and survival, and restore bone stock. Although functional improvement has been documented, it is unknown whether these composites survive long periods and whether they restore bone stock. We therefore determined long-term allograft-prosthesis composite survival, identified major complications that led to revision, and determined whether allograft bone stock could be spared at the time of revision. We also compared the radiographic appearance of allografts sterilized by gamma radiation and fresh-frozen allografts. We retrospectively reviewed 32 patients with bone malignancy in the proximal femur who underwent reconstruction with a cemented allograft-prosthesis composite. The allograft-prosthesis composite was a primary reconstruction for 23 patients and a revision procedure for nine. The minimum followup was 2 months (median, 68 months; range, 2-232 months). The cumulative incidence of revision for any reason was 14% at 5 years (95% confidence interval, 1%-28%) and 19% at 10 years (95% confidence interval, 3%-34%). Nine patients (28%) had revision of the reconstruction during followup; four of these patients had revision surgery for infection. Allografts sterilized by gamma radiation showed worse resorption than fresh-frozen allografts. Based on reported results, allograft-composite prostheses do not appear to improve survival compared with megaprostheses. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Assessment of vascular invasion by bone and soft tissue tumours of the limbs: usefulness of MDCT angiography.

OBJECTIVE: To evaluate the accuracy of computed tomography angiography (CTA) in predicting arterial encasement by limb tumours, by comparing CTA with surgical findings (gold standard). METHODS: Preoperative CTA images of 55 arteries in 48 patients were assessed for arterial status: cross-sectional CTA images were scored as showing a fat plane between artery and tumour (score 0), slight contact between artery and tumour (score 1), partial arterial encasement (score 2) or total arterial encasement (score 3). Reformatted CTA images were assessed for arterial displacement, rigid wall, stenosis or occlusion. At surgery, arteries were classified as free or surgically encased; 45 arteries were free and 10 were surgically encased. RESULTS: Multivariate logistic regression identified the axial CTA score as a relevant predictor for arterial encasement and subsequent vascular intervention during surgery. All sites where CTA showed a fat plane between the tumour and the artery were classified as free at surgery (n = 28/28). The sensitivity of total arterial encasement on CTA (score 3) was 90%, specificity 93%, accuracy 93% and positive likelihood ratio 13.5. CONCLUSION: CTA evidence of total arterial encasement is a highly specific indication of arterial encasement. The presence of fat between the tumour and the artery on CTA rules out arterial involvement at surgery.

Monitoring surgical performance: an application to total hip replacement.

RATIONALE, AIMS AND OBJECTIVES: Inadequate surgical implantation of a hip replacement may result in decreased patient satisfaction and reduced implant survival. The objective was to monitor surgical performance in hip replacement. METHOD: The study took place at a teaching centre. All primary total hip replacements were prospectively included in the series. For each hip replacement, intraoperative technical errors, cup and stem fixation and position, and postoperative complications were recorded. If all items rated were correct, the procedure was considered as correct. The Cumulative Sums (CUSUM) test was used to monitor the performance of the centre. A 90% proportion of successful procedures was considered as adequate performance and a 75% proportion of successful procedures was deemed as inadequate performance. Meetings were conducted to discuss the results of monitoring. RESULTS: Eighty-three total hip replacements were monitored. Overall, 28 procedures (34%) were considered inadequate. The most potent reasons for inadequate performance were cup positioning and stem fixation. The CUSUM test signalled after the second procedure that performance was inadequate. After the first meeting, despite an improvement was seen, the CUSUM test raised an alarm indicating inadequate performance. The study was stopped after the second meeting because of funding reasons before it could be demonstrated that performance had reached the desired level. CONCLUSION: This study has demonstrated that implementing a dedicated system to monitor surgical performance in a teaching hospital improves the quality of implantation of total hip replacements. Nonetheless, the target of ninety percent of adequate primary total hip replacement could not be reached and efforts should be continued.

Fractures of the ankylosed spine: MDCT and MRI with emphasis on individual anatomic spinal structures.

OBJECTIVE: The purpose of this article is to illustrate the spectrum of MDCT and MRI appearances of spinal fractures in ankylosing spondylitis and diffuse idiopathic skeletal hyperostosis. CONCLUSION: Spinal fractures associated with ankylosing spondylitis and diffuse idiopathic skeletal hyperostosis usually involve the three columns of the spine, and injury to the posterior osteoligamentous component is the hallmark of these fractures. Osseous and ligamentous injuries can be accurately visualized and analyzed with MDCT with multiplanar reformation and with MRI.

Ipsilateral femoral autograft reconstruction after resection of a pelvic tumor.

BACKGROUND: Reconstruction of bone after the resection of a pelvic tumor is challenging. The purpose of the present study was to evaluate the use of the ipsilateral femur as the graft material for reconstruction. METHODS: We performed a retrospective review of thirteen patients with a malignant pelvic lesion who underwent resection followed by reconstruction with an ipsilateral femoral autograft and insertion of a total hip replacement. The study group included nine men and four women with a median age of fifty-one years at the time of the reconstruction. The diagnosis was chondrosarcoma in eight patients, metastasis in three, and myeloma and radiation-induced malignant disease in one each. The surviving patients were assessed functionally and radiographically; the cumulative probability of revision was estimated while taking into account competing risks. RESULTS: The median duration of follow-up was forty-nine months. At the time of the latest follow-up, seven patients were alive and disease-free and six had died from metastatic disease. Four patients had had revision of the reconstruction, two for the treatment of mechanical complications and two for the treatment of infection. Three other patients had mechanical complications but had not had a revision. The cumulative probability of revision of the reconstruction for mechanical failure was 8% (95% confidence interval, 0% to 23%), 8% (95% confidence interval, 0% to 23%), and 16% (95% confidence interval, 0% to 39%) at one, two, and four years, respectively. CONCLUSIONS: Although it has attendant complications consistent with pelvic tumor surgery, an ipsilateral femoral autograft reconstruction may be an option for reconstruction of pelvic discontinuity in a subgroup of patients following tumor resection. This innovative procedure requires longer-term follow-up studies.