Performance of radiography and single-photon emission computed tomography/computed tomography in painful total hip arthroplasty and impact on arthroplasty survival

PURPOSE

To investigate the performance of radiography and single-photon emission computed tomography/computed tomography (SPECT/CT) in painful hip arthroplasty regarding loosening and arthroplasty survival.

METHODS

Radiography and SPECT/CT reports of 249 painful hip arthroplasties of 191 patients were reviewed. Positive imaging was defined if loosening, infection, and polyethylene wear were found, indicating the need for arthroplasty exchange. Median time from radiograph to operation or last follow-up was 41.3 months (range 0.3-118.4 months). In 67 patients, the performance of radiographs and SPECT/CT regarding loosening was compared with an intraoperative reference standard. The time point of arthroplasty exchange was compared with imaging diagnosis and evaluated with Kaplan-Meier curves.

RESULTS

Exchange of cup, shaft, or both was performed in 76 of 249 arthroplasties. Main diagnoses on SPECT/CT were loosening (n = 94), infection (n = 5), and polyethylene wear (n = 15). In total, 104 patients were SPECT/CT positive compared to 84 patients on radiography. Five-year survival of arthroplasties for radiograph positive and negative arthroplasties was 41.5%/83.4% and 39.3%/90.7% for SPECT/CT, respectively. Prognostic impact regarding arthroplasty exchange was highest in radiograph and SPECT/CT concordant positive patients (hazard ratio 19.7 as compared to radiograph and SPECT/CT negative patients). Sensitivity and specificity in 67 operated patients regarding shaft loosening were 59.4%/80.0% with radiography, 90.6%/68.6% with SPECT/CT (P = 0.002 for sensitivity and P = 0.29 for specificity), and for cup loosening 47.4%/89.6% with radiography and 63.2%/85.4% with SPECT/CT (P = 0.51, respectively, P = 0.63).

CONCLUSION

In patients with painful hip arthroplasty, positive radiography, and SPECT/CT are associated with poorer arthroplasty survival. Performance regarding loosening is slightly better with SPECT/CT.

MRI of complex regional pain syndrome in the foot

PURPOSE

To evaluate the diagnostic potential of MRI in patients with suspected CRPS (complex regional pain syndrome).

METHOD

A retrospective health-record search was conducted for patients with suspected CRPS (foot). Fifty patients with initially suspected CRPS were included (37 females (51 ± 13 years) and 13 males (44 ± 15 years)). All patients underwent MRI. Two radiologists assessed skin, bone, and soft tissue parameters on MRI. The final diagnosis was CRPS (Gold standard: Budapest criteria) or non-CRPS. MRI parameters were compared between CRPS patients and non-CRPS patients.

RESULTS

CRPS was diagnosed in 22/50(44 %) patients. Skin thickness (1.9 ± 0.5 mm vs. 1.7 ± 0.3 mm, p = 0.399), enhancement, and subcutaneous edema showed no differences between CRPS and non-CRPS patients. Bone marrow edema presence and pattern were not different between groups. Up to 50 % of CRPS patients showed no bone marrow edema. Subcortical enhancement and periosteal enhancement were not different between groups. For reader 1, muscle edema score was higher in the non-CRPS group compared to the CRPS group (0.1 ± 0.2 vs. 0.6 ± 1.0, p = 0.008), but not different for reader 2 (0.1 ± 0.5 vs. 0.2 ± 0.8, p = 0.819). Perfusion pattern was more extensive in non-CRPS patients for reader 1 (p = 0.048), but not for reader 2 (p = 0.157). Joint effusions showed no difference between groups.

CONCLUSIONS

MRI cannot distinguish between CRPS and non-CRPS patients. The role of MR imaging in patients with suspected CRPS is to exclude alternative diagnoses that would better explain patients' symptoms.

Anomalous insertion of the medial meniscus into a triple bundle anterior cruciate ligament: A rare combination of two anatomical variants

•

The anomalous insertion of the medial meniscus into a triple bundle anterior cruciate ligament is a rare variant.

•

The coexistence of these anomalies might be a risk factor for developing tears of the medial meniscus.

•

Excision of the anomalous insertion of the medial meniscus is a possible form of treatment when conservative therapy fails.

Rare anatomical variants in the human knee joint include the anomalous insertion of the medial meniscus (AIMM) into the anterior cruciate ligament (ACL) or the presence of a triple bundle ACL. The functional implications of those anomalies have not yet been fully elucidated and might be important in reconstructive surgery of the damaged knee.

We report the case of a 35-year-old female patient with an AIMM into a triple bundle ACL associated with tears of the medial meniscus in both of her knees. Arthroscopic partial meniscectomy was performed on one side, and conservative treatment with physiotherapy was chosen for the other side with good clinical outcomes.

Long-Term Outcomes of Pectoralis Major Transfer for the Treatment of Irreparable Subscapularis Tears: Results After a Mean Follow-up of 20 Years

BACKGROUND

One recognized salvage option in the treatment of an irreparable subscapularis tear is the pectoralis major tendon transfer (PMT). We aimed to analyze the long-term clinical and imaging outcome of PMT for irreparable subscapularis deficiency.

METHODS

Twenty-eight consecutive patients representing 30 shoulders underwent PMT at a mean age of 53.0 years (range, 35 to 67 years). At a mean of 19.7 years (range, 18 to 22 years) postoperatively, 24 shoulders (80%) were clinically examined and 21 were radiographically and sonographically assessed. The long-term results were compared with preoperative findings and previously published short-term results.

RESULTS

The mean relative Constant score (percentage of age and sex-matched normal scores; CS%) and the Subjective Shoulder Value (SSV) both improved significantly from preoperatively (CS%, 47%, and SSV, 22%) to postoperatively (CS%, 77%, and SSV, 71%; p < 0.001 for both). All patients rated their results as good or excellent. Active anterior elevation was improved from preoperatively (120°) to postoperatively (131°), but the difference was not significant. Active internal and external rotation decreased significantly from the short-term (32-month) follow-up to the time of the latest follow-up (p = 0.005 and p = 0.002, respectively); however, internal rotation remained at 6 points compared with the 8 points recorded at short-term follow-up and external rotation decreased only from a mean of 51° to 39°. Loss of active range of motion was not observed subjectively and was not subjectively limiting, represented by the high ultimate SSV and overall satisfaction. Four shoulders (19%) showed evidence of glenohumeral arthropathy (Samilson and Prieto grade 3), but clinically were mildly symptomatic to asymptomatic at the time of the latest follow-up (CS% range, 67% to 88%; SSV range, 70% to 80%). Rupture of the PMT was sonographically identified in 2 patients (10%) and was associated with radiographic evidence of advanced cuff tear arthropathy (Hamada stages ≥4). Six (20%) of the initial 30 shoulders were revised, and 1 (4%) of the 24 shoulders that were clinically examined underwent reverse total shoulder arthroplasty.

CONCLUSIONS

At long-term follow-up, PMT for isolated and combined subscapularis tears is associated with good to excellent clinical results. Although one-third of the shoulders developed mildly symptomatic or asymptomatic osteoarthritis, the need for salvage with use of reverse total shoulder arthroplasty was rare.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Magnetic resonance imaging (MRI) versus single photon emission computed tomography (SPECT/CT) in painful total hip arthroplasty: a comparative multi-institutional analysis

OBJECTIVE

To investigate the value of MRI in comparison to single photon emission computed tomography (SPECT)/CT in patients with painful hip arthroplasties.

METHODS

A prospective, multi-institutional study was performed. Therefore, 35 consecutive patients (21 female, 14 male, mean age 61.8 ± 13.3 years) with 37-painful hip arthroplasties were included. A hip surgeon noted the most likely diagnosis based on clinical examination and hip radiographs. Then, MRI and SPECT/CT of the painful hips were acquired. MRI and SPECT/CT were assessed for loosening, infection, fracture, tendon pathology and other abnormalities. Final diagnosis and therapy was established by the hip surgeon after integration of MRI and SPECT/CT results. The value of MRI and SPECT/CT for diagnosis was assessed with a 3-point scale (1 = unimportant, 2 = helpful, 3 = essential).

RESULTS

Loosening was observed in 13/37 arthroplasties (6 shaft only, 6 cup only, 1 combined). Sensitivity, specificity, positive predictive value and negative predictive value for loosening of MRI were 86%/88%/60%/100% and of SPECT/CT 93%/97%/90%/100%, respectively. MRI and SPECT/CT diagnosed infection correctly in two of three patients and fractures in two patients, which were missed by X-ray. MRI detected soft tissue abnormalities in 21 patients (6 bursitis, 14 tendon lesions, 1 pseudotumor), of which only 1 tendon abnormality was accurately detected with SPECT/CT. All 5 arthroplasties with polyethylene wear were correctly diagnosed clinically and with both imaging modalities. MRI and SPECT/CT were judged as not helpful in 0/0%, as helpful in 16%/49% and essential in 84%/51%.

CONCLUSION

In patients with painful hip arthroplasty SPECT/CT is slightly superior to MR in the assessment of loosening. MRI is far superior in the detection of soft tissue, especially tendon pathologies.

ADVANCES IN KNOWLEDGE

To our knowledge this is the first prospective, multiinstitutional study which compares MRI with SPECT/CT in painful hip arthroplasties. We found that MRI is far superior in the detection of soft tissue pathologies, whereas SPECT/CT remains slightly superior regarding loosening.

Acetabular coverage differs between standing and supine positions: model-based assessment of low-dose biplanar radiographs and comparison with CT

OBJECTIVES

To evaluate the feasibility of 2D and 3D acetabular coverage assessments based on low-dose biplanar radiographs (BPR) in comparison with CT, and to demonstrate the influence of weight-bearing position (WBP) on anterior and posterior acetabular coverages.

METHODS

Fifty patients (21 females, 29 males) underwent standing BPR and supine CT of the pelvis. Using dedicated software, BPR-based calculations of anterior and posterior 2D coverages and anterior, posterior, and global 3D coverages were performed in standardized anterior pelvic plane (APP) and WBP. CT-based anterior and posterior 2D coverages and global 3D coverage was calculated in APP and compared with BPR-based data. Statistics included intraclass correlation coefficients (ICC) and Bland-Altman plots.

RESULTS

Mean anterior 2D coverage was 21.2% (standard deviation, ± 7.4%) for BPR and 23.8% (± 8.4%) for CT (p = 0.226). Mean posterior 2D coverage was 54.2% (± 9.8%) for BPR and 61.7% (± 9.7%) for CT (p = 0.001). Mean global 3D coverage was 46.5% (± 3.0%) for BPR and 45.6% (± 3.6%) for CT (p = 0.215). The inter-method reliability between CT and BPR and inter-reader reliability for BPR-based measurements were very good for all measurement (all ICC > 0.8). Based on BPR, mean anterior and posterior 3D coverages were 20.5% and 26.0% in WBP and APP, while 25 patients increased anterior and 24 patients increased posterior 3D coverage from APP to WBP with a relative change of coverage of up to 11.9% and 10.0%, respectively.

CONCLUSIONS

2D and 3D acetabular coverages can be calculated with very good reliability based on BPR. The impact of standing position on acetabular coverage can be quantified with BPR on an individual basis.

KEY POINTS

• 2D and 3D acetabular coverages can be calculated with very good reliability based on biplanar radiographs in comparison with CT. • The impact of standing position on anterior and posterior acetabular coverages can be quantified with BPR on an individual basis.

Guided growth with tension band plate or definitive epiphysiodesis for treatment of limb length discrepancy?

Background

It is not exactly known whether guided growth or definitive epiphysiodesis techniques are superior in treating limb length discrepancy (LLD). The purpose of the present study was therefore to find out if definitive epiphysiodesis is associated with more powerful LLD correction than tension band plate epiphysiodesis.

Methods

Pediatric patients with LLD treated either with tension band plating as a guided growth technique (temporary epiphysiodesis) or a percutaneous drilling technique (definitive epiphysiodesis) around the knee and a minimum follow-up of 12 months were included in this retrospective study. Radiographic measurements were performed by two independent reviewers. The reduction in side difference between preoperative radiographs and last follow-up was calculated and compared between surgical techniques.

Results

Thirty-eight patients (mean age 13.6 years) were included, 17 treated with temporary and 21 with definitive epiphysiodesis. Average follow-up was at 578 days. The reduction of the LLD in 12 months was 5.7 mm in patients treated with temporary epiphysiodesis and 8.4 mm with definitive epiphysiodesis, respectively (p = 0.22). In both groups, LLD could be statistically significantly reduced after 12 and 24 months. Definitive epiphysiodesis had a lower revision rate (4.8% vs. 17.6%). Intra- and interobserver reliability of the measurements was excellent.

Conclusions

As in earlier studies supposed, temporary epiphysiodesis with tension band plating seems to correct LLD less powerful compared to definitive percutaneous epiphysiodesis. However, in the present study, the differences of LLD correction were not statistically significant. We do not recommend the use of tension band plates for LLD correction due to inferior correction with higher complication and revision rate.

Subchondral bone microarchitecture analysis in the proximal tibia at 7-T MRI

Background Bone remodels in response to mechanical loads and osteoporosis results from impaired ability of bone to remodel. Bone microarchitecture analysis provides information on bone quality beyond bone mineral density (BMD). Purpose To compare subchondral bone microarchitecture parameters in the medial and lateral tibia plateau in individuals with and without fragility fractures. Material and Methods Twelve female patients (mean age = 58 ± 15 years; six with and six without previous fragility fractures) were examined with dual-energy X-ray absorptiometry (DXA) and 7-T magnetic resonance imaging (MRI) of the proximal tibia. A transverse high-resolution three-dimensional fast low-angle shot sequence was acquired (0.234 × 0.234 × 1 mm). Digital topological analysis (DTA) was applied to the medial and lateral subchondral bone of the proximal tibia. The following DTA-based bone microarchitecture parameters were assessed: apparent bone volume; trabecular thickness; profile-edge-density (trabecular bone erosion parameter); profile-interior-density (intact trabecular rods parameter); plate-to-rod ratio; and erosion index. We compared femoral neck T-scores and bone microarchitecture parameters between patients with and without fragility fracture. Results There was no statistical significant difference in femoral neck T-scores between individuals with and without fracture (-2.4 ± 0.9 vs. -1.8 ± 0.7, P = 0.282). Apparent bone volume in the medial compartment was lower in patients with previous fragility fracture (0.295 ± 0.022 vs. 0.317 ± 0.009; P = 0.016). Profile-edge-density, a trabecular bone erosion parameter, was higher in patients with previous fragility fracture in the medial (0.008 ± 0.003 vs. 0.005 ± 0.001) and lateral compartment (0.008 ± 0.002 vs. 0.005 ± 0.001); both P = 0.025. Other DTA parameters did not differ between groups. Conclusion 7-T MRI and DTA permit detection of subtle changes in subchondral bone quality when differences in BMD are not evident.

Frequency of inflammatory-like MR imaging findings in asymptomatic fingers of healthy volunteers

OBJECTIVE

To describe the frequency of inflammatory-like findings on MR imaging in asymptomatic volunteers and compare them with patients with known rheumatoid arthritis and psoriatic arthritis.

MATERIALS AND METHODS

MR images of fingers in 42 asymptomatic volunteers and 33 patients with rheumatoid/psoriatic arthritis were analyzed. The Outcome Measures in Rheumatology Clinical Trials (OMERACT) Rheumatoid/Psoriatic Arthritis MRI Scoring System (RAMRIS/PsAMRIS) and tenosynovitis scoring system were used to assess: bone marrow edema (BME), erosions, tendon sheath fluid/tenosynovitis, joint effusion, and soft-tissue edema. Findings and scores were compared between volunteers and patients. Inter-reader agreement was calculated (intraclass correlation coefficients, ICC).

RESULTS

In volunteers, tendon sheath fluid was very common in at least one location (42/42 volunteers for reader 1, 34/42 volunteers for reader 2). BME, erosions, joint effusion, and soft-tissue edema were absent (except one BME in the 3rd proximal phalanx for reader 1). Tendon sheath fluid scores in volunteers and tenosynovitis scores in patients were high (reader 1, 7.17 and 5.39; reader 2, 2.31 and 5.45). Overall, inter-reader agreement was substantial (ICC = 0.696-0.844), except for tendon sheath fluid (ICC = 0.258).

CONCLUSION

Fluid in the finger flexor tendon sheaths may be a normal finding and without gadolinium administration should not be interpreted as tenosynovitis. Bone marrow edema, erosions, joint effusion, and soft-tissue edema in the fingers most likely reflect pathology if present.

Cost-effectiveness of Virtual Bone Strength Testing in Osteoporosis Screening Programs for Postmenopausal Women in the United States

Purpose To investigate whether assessment of bone strength with quantitative computed tomography (CT) in combination with dual-energy x-ray absorptiometry (DXA) is cost-effective as a screening tool for osteoporosis in postmenopausal women. Materials and Methods A state-transition microsimulation model of osteoporosis for postmenopausal women aged 55 years or older was developed with a lifetime horizon and U.S. societal perspective. All model inputs were derived from published literature. Three strategies were compared: no screening, DXA with T score-dependent rescreening intervals, and a combination of DXA and quantitative CT with different intervals (3, 5, and 10 years) at different screening initiation ages (55-65 years). Oral bisphosphonate therapy was started if DXA hip T scores were less than or equal to -2.5, 10-year risk for hip fracture was greater than 3% (World Health Organization Fracture Risk Assessment Tool score, or FRAX), 10-year risk for major osteoporotic fracture was greater than 20% (FRAX), quantitative CT femur bone strength was less than 3000 N, or occurrence of first fracture (eg, hip, vertebral body, wrist). Outcome measures were incremental cost-effectiveness ratios (ICERs) in 2015 U.S. dollars per quality-adjusted life year (QALY) gained and number of fragility fractures. Probabilistic sensitivity analysis was also performed. Results The most cost-effective strategy was combined DXA and quantitative CT screening starting at age 55 with quantitative CT screening every 5 years (ICER, $2000 per QALY). With this strategy, 12.8% of postmenopausal women sustained hip fractures in their remaining life (no screening, 18.7%; DXA screening, 15.8%). The corresponding percentages of vertebral fractures for DXA and quantitative CT with a 5-year interval, was 7.5%; no screening, 11.1%; DXA screening, 9%; for wrist fractures, 14%, 17.8%, and 16.4%, respectively; for other fractures, 22.6%, 30.8%, and 27.3%, respectively. In probabilistic sensitivity analysis, DXA and quantitative CT at age 55 years with quantitative CT screening every 5 years was the best strategy in more than 90% of all 1000 simulations (for thresholds of $50 000 per QALY and $100 000 per QALY). Conclusion Combined assessment of bone strength and bone mineral density is a cost-effective strategy for osteoporosis screening in postmenopausal women and has the potential to prevent a substantial number of fragility fractures. © RSNA, 2017 Online supplemental material is available for this article.

Measurement of acetabular version based on biplanar radiographs with 3D reconstructions in comparison to CT as reference standard in cadavers

To quantify acetabular version using 3 D reconstructions based on biplanar radiographs (BPR) with CT as reference standard. No institutional review board approval was needed. Nine dry-bone pelvises underwent BPR in five different positions (rotation/tilt). The 3 D models of each pelvis were reconstructed by two radiologists on the basis of anatomical landmarks using semi-automated software. Automated software was used to assess the 3 D models and to calculate acetabular versions perpendicular to the anterior pelvic plane on all levels in the craniocaudal direction in 1 mm steps. Transverse CT images perpendicular to the anterior pelvic plain were reconstructed through the acetabulum in 1 mm steps. Both readers measured acetabular version on each image. Inter-reader agreement was calculated. Measurements based on BPR and CT were compared. Inter-reader agreement was almost perfect for BPR-based acetabular version measurements (ICC (intraclass correlation coefficient) = 0.920, P < 0.0005) and CT (ICC = 0.990, P < 0.0005). Correlation of acetabular versions between the five BPR-positions was substantial/almost perfect (ICC = 0.722-0.887 and 0.749-0.872 for readers 1 and 2, respectively; most P < 0.0005). The acetabular version measurements between the ap-positioning from BPR and CT showed moderate agreement (mean CCC (concordance correlation coefficient) = 0.733 for reader 1, CCC = 0.755 for reader 2). Acetabular version on multiple levels can be measured using BPR and dedicated post-processing software and is relatively independent of pelvic rotation and tilt. Clin. Anat. 30:591-598, 2017. © 2017 Wiley Periodicals, Inc.

Femoral torsion assessment with MRI in children: Should we use the bony or cartilaginous contours?

OBJECTIVE

To assess whether the use of cartilaginous contours at the femoral condyles instead of bony contours significantly changes femoral torsion measurements in children.

MATERIALS AND METHODS

Femoral torsion was measured in 32 girls (mean age 10.1 years±2.3 standard deviation) and 42 boys (10.9 years±2.5) on axial magnetic resonance (MR) images by two independent readers (R1,R2). The femoral condyle angle was measured using each the cartilaginous and bony contours of the distal femur. Cartilage thickness at femoral condyles was assessed. Intraclass-correlation-coefficient (ICC) and Pearson's correlation were used for statistical analysis.

RESULTS

Mean difference between cartilaginous and bony femoral torsion in girls was -1.1°±1.75 (range, -5.4° to 3.1°) for R1 and -1.64°±1.67 (-6.3° to 2.1°) for R2, in boys -1.5°±1.87 (-8.4° to 1.1°) for R1 and -2.28°±1.48 (-4.3° to 9.7°) for R2. Weak-to-moderate correlations between difference of cartilaginous-versus-bony measurements and cartilage thickness (r=-0.15 to -0.55, P<0.001-0.46) or age (r=-0.33 to 0.46, P<0.001-0.006) were found for both genders. Intermethod-ICC for cartilaginous versus bony femoral torsion measurements was 0.99/0.99 for R1/R2 in girls, and 0.99/0.98 in boys.

CONCLUSION

There is only a small difference when measuring femoral torsion through cartilaginous versus bony contours, and no major difference in this between boys and girls.

Hip Imaging in Athletes: Sports Imaging Series

Hip or groin pain in athletes is common and clinical presentation is often nonspecific. Imaging is a very important diagnostic step in the work-up of athletes with hip pain. This review article provides an overview on hip biomechanics and discusses strategies for hip imaging modalities such as radiography, ultrasonography, computed tomography, and magnetic resonance (MR) imaging (MR arthrography and traction MR arthrography). The authors explain current concepts of femoroacetabular impingement and the problem of high prevalence of cam- and pincer-type morphology in asymptomatic persons. With the main focus on MR imaging, the authors present abnormalities of the hip joint and the surrounding soft tissues that can occur in athletes: intraarticular and extraarticular hip impingement syndromes, labral and cartilage disease, microinstability of the hip, myotendinous injuries, and athletic pubalgia. (©) RSNA, 2016.

Advances in MRI around metal

The prevalence of orthopedic metal implants is continuously rising in the aging society. Particularly the number of joint replacements is increasing. Although satisfying long-term results are encountered, patients may suffer from complaints or complications during follow-up, and often undergo magnetic resonance imaging (MRI). Yet metal implants cause severe artifacts on MRI, resulting in signal-loss, signal-pileup, geometric distortion, and failure of fat suppression. In order to allow for adequate treatment decisions, metal artifact reduction sequences (MARS) are essential for proper radiological evaluation of postoperative findings in these patients. During recent years, developments of musculoskeletal imaging have addressed this particular technical challenge of postoperative MRI around metal. Besides implant material composition, configuration and location, selection of appropriate MRI hardware, sequences, and parameters influence artifact genesis and reduction. Application of dedicated metal artifact reduction techniques including high bandwidth optimization, view angle tilting (VAT), and the multispectral imaging techniques multiacquisition variable-resonance image combination (MAVRIC) and slice-encoding for metal artifact correction (SEMAC) may significantly reduce metal-induced artifacts, although at the expense of signal-to-noise ratio and/or acquisition time. Adding advanced image acquisition techniques such as parallel imaging, partial Fourier transformation, and advanced reconstruction techniques such as compressed sensing further improves MARS imaging in a clinically feasible scan time. This review focuses on current clinically applicable MARS techniques. Understanding of the main principles and techniques including their limitations allows a considerate application of these techniques in clinical practice. Essential orthopedic metal implants and postoperative MR findings around metal are presented and highlighted with clinical examples.

LEVEL OF EVIDENCE

4 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:972-991.

Enthesitis of lumbar spinal ligaments in clinically suspected spondyloarthritis: value of gadolinium-enhanced MR images in comparison to STIR

OBJECTIVE

To compare detection of spinal ligament enthesitis between gadolinium-enhanced fat-saturated T1-weighted gadolinium-enhanced fat-saturated T1-weighted (T1+Gd) and STIR sequences in patients with suspected spondyloarthritis.

MATERIALS AND METHODS

Sixty-eight patients (37 males, 42 ± 14 years) with a sacroiliac-joint (SIJ) and lumbar spine MRI for suspected spondyloarthritis were prospectively included. Sagittal T1+Gd and STIR images of the lumbar spine were assessed by two readers for enthesitis of interspinous/supraspinous ligaments, and for capsulitis of facet-joints between T12-S1. Patients' MRI were grouped according to ASAS (Assessment of SpondyloArthritis international Society) criteria in positive (group A) or negative (group B) SIJs. Enthesitis/capsulitis were compared between groups. Interreader agreement was assessed.

RESULTS

Enthesitis/capsulitis per patient was statistically significantly more frequent with T1+Gd compared to STIR (p ≤ 0.007), except for interspinous ligaments for reader 1 (p = 0.455). Interspinous enthesitis, supraspinous enthesitis, and capsulitis were present with T1+Gd(STIR) in 64.7 %(72.1 %), 60.3 %(17.7 %), and 61.8 %(29.4 %) for reader 1, and 51.5 %(41.2 %), 45.6 %(7.4 %), and 91.2 %(45.5 %) for reader 2. There were 76.5 %(52/68) patients in group A and 23.5 %(16/68) in group B. Total number of enthesitis/capsulitis on T1+Gd was statistically significantly higher in group A than B (4.96 vs. 2.94, p = 0.026; 8.12 vs. 5.25, p = 0.041 for reader 1 and 2, respectively). Interreader agreement showed mixed results for interspinous/supraspinous/capsulitis but was higher on T1+Gd (ICC = 0.838/0.783/0.367; p ≤ 0.001) compared to STIR (ICC = 0.652/0.298/0.224; p ≤ 0.032).

CONCLUSION

In patients with suspected spondyloarthritis, enthesitis/capsulitis in the lumbar spine are common findings and more frequently/reliably detected with T1+Gd than STIR. In patients with positive SIJ-MRI, the total number of enthesitis/capsulitis in T1+Gd was higher compared to patients with negative SIJ-MRI.

Quantification of early fatty infiltration of the rotator cuff muscles: comparison of multi-echo Dixon with single-voxel MR spectroscopy

OBJECTIVES

To evaluate quantification of early fatty infiltration in supraspinatus muscles with magnetic resonance (MR) imaging using a T2*-corrected multi-echo 3D-gradient-echo Dixon-based sequence (multi-echo Dixon) and compare it to proton-MR-spectroscopy.

METHODS

Sixty subjects (mean age 46 years, 41 men) with good supraspinatus muscle quality on 1.5 T MR imaging were included. Fat percentage (FP) in the supraspinatus muscle was quantified using a multi-echo Dixon compared to single-voxel MR spectroscopy as reference standard. In 18 subjects the multi-echo Dixon was repeated to assess test-retest reliability. Measurements based on multi-echo Dixon were performed by two independent readers by placing regions-of-interest (ROIs) in the supraspinatus muscle corresponding to the MR-spectroscopy voxel. Intraclass and concordance correlation coefficients (ICC/CCC) were used for statistical analysis.

RESULTS

Test-retest reliability was substantial for reader 1 (ICC = 0.757) and almost perfect for reader 2 (ICC = 0.873). Inter-reader reliability for multi-echo Dixon was almost perfect (ICC = 0.893, P < .0005). Mean FP in all 60 subjects with multi-echo Dixon was 3.5 ± 1.6 for reader 1, 3.7 ± 1.8 for reader 2, and 2.8 ± 1.4 with MR spectroscopy. Correlation between multi-echo Dixon and MR spectroscopy was moderate (CCC = 0.641).

CONCLUSION

The multi-echo Dixon sequence is a reliable method and comparable to MR-spectroscopy for quantification of low levels of fatty infiltration in the supraspinatus muscle.

KEY POINTS

• Multi-echo Dixon for low fat quantification in muscles is reliable. • Multi-echo Dixon low fat quantification is comparable to single-voxel MR spectroscopy • Multi-echo Dixon detects substantial differences in fatty infiltration within Goutallier 0-1.

[CT and MRI of hip arthroplasty]

Metal-induced artifacts impair image quality of computed tomography (CT) and magnetic resonance imaging (MRI) in patients with hip prostheses. Due to new developments in metal artifact reduction both methods can now be used for evaluation of a painful hip prosthesis. Iterative reconstruction algorithms and dual-energy scans are among the newer CT techniques for artifact reduction, while slice-encoding for metal artifact correction (SEMAC) and multi-acquisition variable-resonance image combination (MAVRIC) have introduced substantial improvements for MRI. Loosening of the hip prosthesis, osteolysis from small wear particles and pseudotumors in metal-on-metal prostheses are specific pathologies in patients with total hip arthroplasty. Other causes of painful hip prostheses are infections, fractures, tendinopathies, tendon ruptures, muscle and nerve alterations and heterotopic ossifications.