Modic type 2 changes are fibroinflammatory changes with complement system involvement adjacent to degenerated vertebral endplates.

Background: Vertebral endplate signal intensity changes visualized by magnetic resonance imaging termed Modic changes (MC) are highly prevalent in low back pain patients. Interconvertibility between the three MC subtypes (MC1, MC2, MC3) suggests different pathological stages. Histologically, granulation tissue, fibrosis, and bone marrow edema are signs of inflammation in MC1 and MC2. However, different inflammatory infiltrates and amount of fatty marrow suggest distinct inflammatory processes in MC2. Aims: The aims of this study were to investigate (i) the degree of bony (BEP) and cartilage endplate (CEP) degeneration in MC2, (ii) to identify inflammatory MC2 pathomechanisms, and (iii) to show that these marrow changes correlate with severity of endplate degeneration. Methods: Pairs of axial biopsies (n = 58) spanning the entire vertebral body including both CEPs were collected from human cadaveric vertebrae with MC2. From one biopsy, the bone marrow directly adjacent to the CEP was analyzed with mass spectrometry. Differentially expressed proteins (DEPs) between MC2 and control were identified and bioinformatic enrichment analysis was performed. The other biopsy was processed for paraffin histology and BEP/CEP degenerations were scored. Endplate scores were correlated with DEPs. Results: Endplates from MC2 were significantly more degenerated. Proteomic analysis revealed an activated complement system, increased expression of extracellular matrix proteins, angiogenic, and neurogenic factors in MC2 marrow. Endplate scores correlated with upregulated complement and neurogenic proteins. Discussion: The inflammatory pathomechanisms in MC2 comprises activation of the complement system. Concurrent inflammation, fibrosis, angiogenesis, and neurogenesis indicate that MC2 is a chronic inflammation. Correlation of endplate damage with complement and neurogenic proteins suggest that complement system activation and neoinnervation may be linked to endplate damage. The endplate-near marrow is the pathomechanistic site, because MC2 occur at locations with more endplate degeneration. Conclusion: MC2 are fibroinflammatory changes with complement system involvement which occur adjacent to damaged endplates.

Atypical patterns of spinal segment degeneration in patients with abdominal aortic aneurysms.

PURPOSE: Abdominal aortic aneurysms (AAAs) affect the vascular perfusion of the lumbar spine. The treatment of AAAs with endovascular aortic aneurysm repair (EVAR) completely occludes the direct vascular supply to the lumbar spine. We hypothesized that patients with AAA who undergo EVAR show a different pattern of spinal degeneration than individuals without AAA. METHODS: In this retrospective institutional review board-approved study, 100 randomly selected patients with AAA who underwent EVAR with computed tomography (CT) scans between 2005 and 2017 were compared with age- and gender-matched controls without AAA. In addition, long-term follow-up CT images (> 6 months before EVAR, at the time of EVAR, and > 12 months after EVAR) of the patients were analysed to compare the progression of degeneration from before to after EVAR. Degeneration scores, lumbar levels with the most severe degeneration, and lumbar levels with progressive degeneration were analysed in all CT images. Fisher's exact test, Wilcoxon signed-rank test, and Mann-Whitney U test were performed for statistical analyses. RESULTS: Compared with the control group (n = 94), the most severe degeneration was more commonly detected in the mid-lumbar area in the patient group (n = 100, p = 0.016), with significantly more endplate erosions being detected in the lumbar spine (p = 0.015). However, EVAR did not result in significant additional acceleration of the degenerative process in the long-term follow-up analysis (n = 51). CONCLUSION: AAA is associated with atypical, more cranially located spinal degradation, particularly in the mid-lumbar segments; however, EVAR does not seem to additionally accelerate the degenerative process. This observation underlines the importance of disc and endplate vascularization in the pathomechanism of spinal degeneration. LEVEL OF EVIDENCE I: Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Role of C-reactive protein in the bone marrow of Modic type 1 changes.

Modic type 1 changes (MC1) are vertebral bone marrow lesions and associate with low back pain. Increased serum C-reactive protein (CRP) has inconsistently been associated with MC1. We aimed to provide evidence for the role of CRP in the tissue pathophysiology of MC1 bone marrow. From 13 MC1 patients undergoing spinal fusion at MC1 levels, vertebral bone marrow aspirates from MC1 and intrapatient control bone marrow were taken. Bone marrow CRP, interleukin (IL)-1, and IL-6 were measured with enzyme-linked immunosorbent assays; lactate dehydrogenase (LDH) was measured with a colorimetric assay. CRP, IL-1, and IL-6 were compared between MC1 and control bone marrow. Bone marrow CRP was correlated with blood CRP and with bone marrow IL-1, IL-6, and LDH. CRP expression by marrow cells was measured with a polymerase chain reaction. Increased CRP in MC1 bone marrow (mean difference: +0.22 mg CRP/g, 95% confidence interval [CI] [-0.04, 0.47], p = 0.088) correlated with blood CRP (r = 0.69, p = 0.018), with bone marrow IL-1ß (ρ = 0.52, p = 0.029) and IL-6 (ρ = 0.51, p = 0.031). Marrow cells did not express CRP. Increased LDH in MC1 bone marrow (143.1%, 95% CI [110.7%, 175.4%], p = 0.014) indicated necrosis. A blood CRP threshold of 3.2 mg/L detected with 100% accuracy increased CRP in MC1 bone marrow. In conclusion, the association of CRP with inflammatory and necrotic changes in MC1 bone marrow provides evidence for a pathophysiological role of CRP in MC1 bone marrow.

Learning how to perform ultrasound-guided interventions with and without augmented reality visualization: a randomized study.

OBJECTIVES: Augmented reality (AR), which entails overlay of in situ images onto the anatomy, may be a promising technique for assisting image-guided interventions. The purpose of this study was to investigate and compare the learning experience and performance of untrained operators in puncture of soft tissue lesions, when using AR ultrasound (AR US) compared with standard US (sUS). METHODS: Forty-four medical students (28 women, 16 men) who had completed a basic US course, but had no experience with AR US, were asked to perform US-guided biopsies with both sUS and AR US, with a randomized selection of the initial modality. The experimental setup aimed to simulate biopsies of superficial soft tissue lesions, such as for example breast masses in clinical practice, by use of a turkey breast containing olives. Time to puncture(s) and success (yes/no) of the biopsies was documented. All participants completed questionnaires about their coordinative skills and their experience during the training. RESULTS: Despite having no experience with the AR technique, time to puncture did not differ significantly between AR US and sUS (median [range]: 17.0 s [6-60] and 14.5 s [5-41], p = 0.16), nor were there any gender-related differences (p = 0.22 and p = 0.50). AR US was considered by 79.5% of the operators to be the more enjoyable means of learning and performing US-guided biopsies. Further, a more favorable learning curve was achieved using AR US. CONCLUSIONS: Students considered AR US to be the preferable and more enjoyable modality for learning how to obtain soft tissue biopsies; however, they did not perform the biopsies faster than when using sUS. KEY POINTS: • Performance of standard and augmented reality US-guided biopsies was comparable • A more favorable learning curve was achieved using augmented reality US. • Augmented reality US was the preferred technique and was considered more enjoyable.

The Great Mimickers of Spinal Pathology.

Back pain is one of the leading causes of health costs worldwide, particularly because of the further increased aging population. After clinical examination, spinal imaging is of utmost importance in many patients to reach the correct diagnosis. There are many imaging pitfalls and mimickers of spinal pathology on radiographs, magnetic resonance imaging, and computed tomography. These mimickers may lead to a misdiagnosis or a further imaging work-up if they are not recognized and thus lead to unnecessary examinations and increased health care costs. In this review we present the common mimickers of spinal pathology and describe normal variations when reading imaging studies of the spine.

Spondylophyte classification based on biomechanical effects on segmental stiffness.

BACKGROUND CONTEXT: The biomechanical impact of spondylophytes on segmental stiffness is largely unknown, despite their high incidence. PURPOSE: The aim of this study was to quantify the biomechanical contribution according to location and cranio-caudal extent of spondylophytes and to create a clinically applicable radiological classification system. STUDY DESIGN: Biomechanical cadaveric study. METHODS: Twenty-six cadaveric human lumbar spinal segments with spondylophytes were tested with a displacement-controlled stepwise reduction method. The reduction in load required for the same motion after spondylophyte dissection was used to calculate the biomechanical contribution in flexion, extension, axial rotation, lateral bending, anterior, posterior and lateral shear. The spondylophytes were categorized by assessment of their anatomical position and cranio-caudal extent in computed tomography images (grade 1: spondylophytes spanning less than 50% of the disc-height, grade 2:>50%, grade 3:>90%, grade 4: bony bridging between the vertebrae) by two experienced radiologists. Cohen's kappa (κ) was used to report interreader reliability. RESULTS: The largest biomechanical effect of non-bridging spondylophytes (grade 1-3) was recorded during contralateral bending with a grade-dependent contribution of up to 35%. Other loading directions including ipsilateral bending and translational loading were affected with values below 13%. Spondylophytes with osseous bridging (grade 4) show large contribution to the segmental stiffness in most loading conditions with values reaching over 80%. Interreader agreement for the spondylophyte grading was "substantial" (κ=0.73, p<.001). CONCLUSIONS: The location and cranio-caudal extent of spondylophytes are essential parameters for their biomechanical effect. A reproducible classification has been validated biomechanically and helps evaluate the effect of specific spondylophyte configurations on segmental stiffness. CLINICAL SIGNIFICANCE: Non-bridging spondylophytes primarily act as tensile structures and do not provide relevant propping. A classification system is presented to support understanding of the biomechanical consequences of different spondylophyte configuration for clinical decision making in surgical planning.

Added value of combined acromiohumeral distance and critical shoulder angle measurements on conventional radiographs for the prediction of rotator cuff pathology.

Purpose: To investigate the role of acromiohumeral distance (AHD) and critical shoulder angle (CSA) measurements from conventional radiographs (CR) in isolation and combined (prognostic index PIAHD-CSA) as predictors of full thickness rotator cuff tendon tears (RCT) and critical fatty degeneration (CFD; i.e. as much fat as muscle). Method: In this retrospective study AHD and CSA were measured in 127 CR. MR arthrograms served as reference standard and were screened for RCT and CFD. Statistical analysis for inter-reader agreement, Spearman's rank correlation, linear stepwise regression and logistic regression for AHD and CSA with ROC analyses including PIAHD-CSA were performed. Results: In 90 subjects (17 females, mean age 36.1 ± 14.1) no RCT were found on MR imaging and served as control group. In 37 patients (13 females, mean age 58.7 ± 13.2) ≥ one RCT was found. Inter-reader agreements rated between к = 0.42-0.82 for categorical and 0.91-0.96 for continuous variables. No significant correlation of AHD and CSA with either age or sex was seen (p = 0.28 and p = 0.74, respectively). Case group had significantly smaller mean AHD (8.7 ± 3.2 vs. 10.8 ± 2.2 mm; p < 0.001) and larger mean CSA (36.5 ± 4.5° vs. 33.1 ± 4.0°; p < 0.001). PIAHD-CSA increased diagnostic performance for prediction of RCT and CFD (AUC = 0.78 and 0.71), compared to isolated AHD (0.74 and 0.71) and CSA (0.71 and 0.66). Conclusions: AHD and CSA do not depend on age or sex but differ significantly between healthy and pathologic rotator cuffs. A decreased AHD is most influenced by infraspinatus muscle atrophy and fatty degeneration. Combined PIAHD-CSA increases diagnostic performance for predicting RCT and CFD.

MRI appearance of adjunct surgical material used in spine surgery.

BACKGROUND CONTEXT: Early postoperative MR images are frequently necessary after spine surgery. The appearance of commonly used adjunct hemostatic agents and dural sealants in MR images has not been systematically evaluated. PURPOSE: The purpose of this experimental study was to systematically analyze and describe the characteristics of the most commonly applied hemostatic agents and dural sealants in spine surgery on early postoperative MR images. STUDY DESIGN: Cadaver Study METHODS: Four commonly applied dural sealants (Duraseal, Bioglue, Tachosil, Tisseel) and five commonly used hemostatic agents (Surgiflo, Bonewax, , Spongostan, Gelfoam, Avitene) were investigated. The experimental setting involved a human cadaver where a standard left-sided laminotomy was performed on nine levels of the thoracolumbar spine, and the materials were separately applied and mixed with fresh blood or water for hemostatic and dural sealants, respectively. The cadaver model was scanned at a 3 Tesla MRI and the imaging findings for all materials were compared to the surrounding tissue and systematically reported. RESULTS: All investigated dural sealants and hemostatic agents were distinguishable from the surrounding tissue on MR images with different appearances on the MR sequences. A detailed atlas for the identification of the materials in postoperative spine MRI was established. CONCLUSION: Commonly used hemostatic agents and dural sealants can be successfully identified on early postoperative spine MRI. CLINICAL SIGNIFICANCE: Knowledge about MRI appearances of commonly used adjunct surgical materials helps in interpretation of postoperative imaging and supports clinical decision making.

Hydrostatic integrity of the intervertebral disc assessed by MRI.

Hydrostatic integrity of the intervertebral disc (IVD) is lost during the process of degeneration. Invasive pressure profilometry (IPP) can quantify it, however, is not applicable for clinical use. We aimed to investigate correlations between IPP and MRI findings to assess non-invasive MRI based methods for prediction of hydrostatic integrity of the intervertebral disc. The pressure profiles of 39 lumbar spinal segments originating from 22 human cadavers were recorded during axial compression in the neutral, the flexed and the extended positions. Disc pressure profiles were measured and mathematically transformed to a novel metric that quantifies pressure profile heterogeneity across the disc. The relationship between pressure profile inhomogeneity ("pressure score") and clinically established magnetic resonance-based classifications systems and demographic parameters was then tested using Spearman correlation tests. Pressure profile inhomogeneities were correlated with IVD degeneration (according to Pfirrmann, rho = 0.43, p = 0.006), endplate defects (according to Rajasekaran, rho = 0.39, p = 0.013), segmental degeneration (according to Farshad, rho = 0.41, p = 0.009) and age (rho = 0.32, p = 0.049). Modic changes per se did not affect the pressure profiles significantly (p = 0.23) and pressure scores did not correlate with BMI (rho = -0.21, p = 0.2). Heterogeneity of segmental IVD pressure profiles is a unique measure of disc function. We demonstrate that established clinical methods for MRI characterization of the intervertebral disc, the endplate and overall segmental degeneration all correlate with the hydrostatic integrity of the IVD and can be used for its assessment.

Patient-specific template-guided versus standard freehand lumbar pedicle screw implantation: a randomized controlled trial.

OBJECTIVE: Patient-specific template-guided (TG) pedicle screw placement currently achieves the highest reported accuracy in cadaveric and early clinical studies, with reports of reduced use of radiation and less surgical time. However, a clinical randomized controlled trial (RCT) eliminating potential biases is lacking. This study compares TG and standard freehand (FH) pedicle screw insertion techniques in an RCT. METHODS: Twenty-four patients (mean age 64 years, 9 men and 15 women) scheduled consecutively and independently from this study for 1-, 2-, or 3-level lumbar fusion were randomized to either the FH (n = 12) or TG (n = 12) group. Accuracy of pedicle screw placement, intraoperative parameters, and short-term complications were compared. RESULTS: A total of 112 screws (58 FH and 54 TG screws) were implanted in the lumbar spine. Radiation exposure was significantly less in the TG group (78.0 ± 46.3 cGycm2) compared with the FH group (234.1 ± 138.1 cGycm2, p = 0.001). There were 4 pedicle screw perforations (6.9%) in the FH group and 2 (3.7%) in the TG group (p > 0.99), with no clinical consequences. Clinically relevant complications were 1 postoperative pedicle fracture in the FH group (p > 0.99), 1 infection in the FH group, and 2 infections in the TG group (p > 0.99). There were no significant differences in surgical exposure time, screw insertion time, overall surgical time, or blood loss between the FH and TG groups. CONCLUSIONS: In this RCT, patient-specific TG pedicle screw insertion in the lumbar region achieved a high accuracy, but not better than a standardized FH technique. Even if intraoperative radiation exposure is less with the TG technique, the need for a preoperative CT scan counterbalances this advantage. However, more difficult trajectories might reveal potential benefits of the TG technique and need further research.

Intervertebral disc degeneration relates to biomechanical changes of spinal ligaments.

BACKGROUND CONTEXT: The ligamentum flavum (LF), the inter- and supraspinous ligament (ISL&SSL) and the intertransverse ligament (ITL) are relevant spinal structures for segmental stability. The biomechanical effect of degeneration and aging on their biomechanical properties remains largely unknown. PURPOSE: The aim of this study was to assess the material properties of the ITL, ISL&SSL and LF and to correlate parameters of biomechanical function with LF-thickness, intervertebral disc (IVD) degeneration and age. STUDY DESIGN: Biomechanical cadaveric study. METHODS: MRI- and CT-scans of 50 human lumbar segments (Th12-L5) were used to assess the ISL (acc. to Keorochana), the grade of IVD degeneration (acc. to Pfirrmann) and to quantify LF-thickness. The ITL, ISL&SSL and LF were resected in the neutral position of the spinal segment with a specifically developed method to conserve initial strain. Ramp to failure testing was performed (0.5 mm/s) to record initial tension, slack length, stiffness and ultimate strength. The relationship between the biomechanical characteristics and age and radiological parameters were analyzed. There are no study-specific conflicts of interest and no external funding was received for this study. RESULTS: With aging, a significant reduction in initial tension (r=-0.5, p<.01) and ultimate strength (r=-0.41, p<.01) of the LF was observed, while the effect on LF-stiffness and the characteristics of the other ligaments was non-significant. IVD-degeneration was correlated with a significant reduction in stiffness (r=-0.47, p=.001; r=-0.36, p=.01) and ultimate strength (r=-0.3, p=.04; r=-0.36, p=.01) of the LF and ISL&SSL respectively and a significant reduction in initial tension (r=-0.4, p<.01) of the LF. For the ITL, no significant correlation was observed. Comparing Pfirrman 2 to 5, this reduction was 40% to 80% for stiffness 60% to 70% for ultimate strength and 88% for initial tension of the LF. ISL&SSL-stiffness between Kerorochana grade A and D differed significantly (p=.03), while all other comparisons were non-significant (p>.05). LF-thickness did not correlate with the biomechanical properties of the LF (p>.05). CONCLUSIONS: Aging is primarily related to biomechanical changes to the LF. IVD-degeneration is related to a relevant reduction in stiffness and ultimate strength of the LF and ISL&SSL, with a similar trend for the ITL. The ISL-specific Keorochana grading system provides only minimal biomechanical information and LF-thickness does not provide biomechanical information. CLINICAL SIGNIFICANCE: Patient age and the degenerative state of the IVD can be used to evaluate the biomechanical characteristics of the dorsal spinal ligaments, which can be helpful in selecting the optimal surgical procedure (e.g. in decompression surgery) for a specific situation.

Biomechanical Contributions of Spinal Structures with Different Degrees of Disc Degeneration.

STUDY DESIGN: Biomechanical cadaveric study. OBJECTIVE: The aim of this study was to evaluate the effect of degeneration on biomechanical properties of the passive structures of the lumbar spine. SUMMARY OF BACKGROUND DATA: Although the load apportionment among the passive structures in healthy spines follows well-defined contribution patterns, it remains unknown how this load distribution and sagittal preload changes by degenerative processes of the intervertebral disc (IVD). METHODS: Fifty lumbar spinal segments were tested in a displacement-controlled stepwise reduction study in flexion, extension, axial rotation, lateral bending, anterior, posterior and lateral shear. The intertransverse ligaments (ITLs), supraspinous and interspinous ligaments (ISL&SSL), facet joint capsules (FJC), facet joints (FJ), ligamentum flavum (LF), posterior longitudinal ligament (PLL), anterior longitudinal ligament (ALL), and spondylophytes were subsequently reduced. The results were set in relation to IVD-degeneration, quantified with Pfirrmann classification. RESULTS: In flexion, a load redistribution from LF (-28% n.s.) and PLL (-13% n.s.) towards the IVD (+9%, n.s.) is observed comparing grade 2 to 5 IVD degeneration, whereas in all other loading directions, a reduction of IVD-contribution from -12% to -53% is recorded. In axial rotation, anterior and lateral shear, more load is shared by the FJ (+4% n.s., +23% ∗, +13% n.s.). The preload of the ALL, LF, PLL, and IVD is reduced ranging from -0.06 Nm to -0.37 Nm. CONCLUSION: IVD degeneration is related to notable load-redistributions between the passive spinal structures. With further degeneration, reduced contribution of the LF and PLL and higher loads on the IVD are observed in flexion. In the other tested loading directions, the relative load on the IVD is reduced, whereas higher FJ-exposure in axial rotation, anterior and lateral shear is observed. Furthermore, the preload of the spinal structures is reduced. These observations can further the understanding of the degenerative cascade in the spine.Level of Evidence: N/A.

Synthetic Biphasic Scaffolds versus Microfracture for Articular Cartilage Defects of the Knee: A Retrospective Comparative Study.

OBJECTIVE: The purpose of this study was to compare the results of a biphasic synthetic scaffold (TruFit, Smith & Nephew) to microfracture for the treatment of knee cartilage defects and identify patient- and lesion-specific factors that influence outcomes. DESIGN: Prospectively collected data from 132 patients (mean age, 41.8 years; 69% male) with isolated chondral or osteochondral femoral defects treated with biphasic synthetic scaffolds (n = 66) or microfracture (n = 66) were reviewed. Clinical outcomes were evaluated longitudinally over 5 years with the Short Form-36 (SF-36), Activities of Daily Living of the Knee Outcome Survey (KOS-ADL), International Knee Documentation Committee (IKDC), and Marx Activity Scale. Cartilage-sensitive magnetic resonance imaging (MRI) was performed to evaluate osseous integration and cartilage fill in a subgroup of patients. Multivariate regression analysis was used to identify predictors of clinical outcomes within the scaffold group. RESULTS: Both groups demonstrated clinically significant improvements in knee clinical scores over 5 years (P < 0.01). There were no significant differences in KOS-ADL and IKDC scores between groups up to 5 years postoperatively. Marx activity level scores in the microfracture group declined over time, while significant improvements in activity level scores were observed in the scaffold group over 5 years (P < 0.01). Good-quality tissue fill and cartilage isointensity were more often observed in the scaffold group compared with the microfracture group, particularly with longer time intervals. Increasing age, high body mass index, prior microfracture, and traumatic etiology were predictors for inferior outcomes in the scaffold group. CONCLUSIONS: Activity level and MRI appearance following treatment of cartilage lesions with the biphasic synthetic scaffold were superior to microfracture over time in this nonrandomized, retrospective comparison.

Operator independent reliability of direct augmented reality navigated pedicle screw placement and rod bending.

BACKGROUND: AR based navigation of spine surgeries may not only provide accurate surgical execution but also operator independency by compensating for potential skill deficits. "Direct" AR-navigation, namely superposing trajectories on anatomy directly, have not been investigated regarding their accuracy and operator's dependence.Purpose of this study was to prove operator independent reliability and accuracy of both AR assisted pedicle screw navigation and AR assisted rod bending in a cadaver setting. METHODS: Two experienced spine surgeons and two biomedical engineers (laymen) performed independently from each other pedicle screw instrumentations from L1-L5 in a total of eight lumbar cadaver specimens (20 screws/operator) using a fluoroscopy-free AR based navigation method. Screw fitting rods from L1 to S2-Ala-Ileum were bent bilaterally using an AR based rod bending navigation method (4 rods/operator). Outcome measures were pedicle perforations, accuracy compared to preoperative plan, registration time, navigation time, total rod bending time and operator's satisfaction for these procedures. RESULTS: 97.5% of all screws were safely placed (<2 mm perforation), overall mean deviation from planned trajectory was 6.8±3.9°, deviation from planned entry point was 4±2.7 mm, registration time per vertebra was 2:25 min (00:56 to 10:00 min), navigation time per screw was 1:07 min (00:15 to 12:43 min) rod bending time per rod was 4:22 min (02:07 to 10:39 min), operator's satisfaction with AR based screw and rod navigation was 5.38±0.67 (1 to 6, 6 being the best rate). Comparison of surgeons and laymen revealed significant difference in navigation time (1:01 min; 00:15 to 3:00 min vs. 01:37 min; 00:23 to 12:43 min; p = 0.004, respectively) but not in pedicle perforation rate. CONCLUSIONS: Direct AR based screw and rod navigation using a surface digitization registration technique is reliable and independent of surgical experience. The accuracy of pedicle screw insertion in the lumbar spine is comparable with the current standard techniques.

Diurnal T2-changes of the intervertebral discs of the entire spine and the influence of weightlifting.

The purpose was to study if (1) diurnal changes occur in the entire spine and if (2) intervertebral discs (IVDs) of weightlifters (WL) have decreased baseline T2-values in the morning as well as (3) increased diurnal changes throughout the day. This prospective cohort study investigated healthy volunteers between 2015 and 2017. WL were required to have participated in weightlifting ≥ 4×/week for ≥ 5 years, while non-weightlifters (NWL) were limited to < 2×/week for ≥ 5 years. Both groups underwent magnetic resonance imaging (MRI) of the entire spine in the morning and evening. WL were requested to perform weightlifting in-between imaging. IVD regions of interest (nucleus pulposus) were defined and T2-maps were measured. Analysis consisted of unpaired t-test, paired t-test, propensity-score matching (adjusting for age and sex), and Pearson correlation. Twenty-five individuals (15 [60.0%] males) with a mean age of 29.6 (standard deviation [SD 6.9]) years were analyzed. Both groups (WL: n = 12 versus [vs.] NWL: n = 13) did not differ demographic characteristics. Mean IVD T2-values of all participants significantly decreased throughout the day (95.7 [SD 15.7] vs. 86.4 [SD 13.9] milliseconds [ms]) in IVDs of the cervical (71.8 [SD 13.4] vs. 64.4 [SD 14.1] ms), thoracic (98.8 [SD 19.9] vs. 88.6 [SD 16.3] ms), and lumbar (117.0 [SD 23.7] vs. 107.5 [SD 21.6] ms) spine (P < 0.001 each). There were no differences between both groups in the morning (P = 0.635) and throughout the day (P = 0.681), even after adjusting for confounders. It can be concluded that diurnal changes of the IVDs occurred in the entire (including cervical and thoracic) spine. WL and NWL showed similar morning baseline T2-values and diurnal changes. Weightlifting may not negatively affect IVDs chronically or acutely.

Ultrasound-guided interventions with augmented reality in situ visualisation: a proof-of-mechanism phantom study.

BACKGROUND: Ultrasound (US) images are currently displayed on monitors, and their understanding needs good orientation skills. Direct overlay of US images onto the according anatomy is possible with augmented reality (AR) technologies. Our purpose was to explore the performance of US-guided needle placement with and without AR in situ US viewing. METHODS: Three untrained operators and two experienced radiologists performed 200 US-guided punctures: 100 with and 100 without AR in situ US. The punctures were performed in two different phantoms, a leg phantom with soft tissue lesions and a vessel phantom. Time to puncture and number of needle passes were recorded for each puncture. Data are reported as median [range] according to their non-normal distribution. RESULTS: AR in situ US resulted in reduced time (median [range], 13 s [3-101] versus 14 s [3-220]) and number of needle passes (median [range], 1 [1-4] versus 1 [1-8]) compared to the conventional technique. The initial gap in performance of untrained versus experienced operators with the conventional US (time, 21.5 s [3-220] versus 10.5 s [3-94] and needle passes 1 [1-8] versus 1 [1, 2]) was reduced to 12.5 s [3-101] versus 13 s [3-100] and 1 [1-4] versus 1 [1-4] when using AR in situ US, respectively. CONCLUSION: AR in situ US could be a potential breakthrough in US applications by simplifying operator's spatial orientation and reducing experience-based differences in performance of US-guided interventions. Further studies are needed to confirm these preliminary phantom results.

Accuracy of Patient-Specific Template-Guided Versus Freehand Cervical Pedicle Screw Placement from C2 to C7: A Randomized Cadaveric Study.

BACKGROUND: Dorsal spinal instrumentation with cervical pedicle screws (CPS) and rod constructs is performed for numerous pathologies of the cervical spine, although technically demanding. Screw misplacement is biomechanically disadvantageous and carries the risk of neurovascular sequelae. The aim of this study was to assess the accuracy of patient-specific, template-guided CPS placement from C2 to C7 compared with the freehand technique. METHODS: Patient-specific targeting guides were used for placement of 3.5 mm CPS from C2 to C7 in 4 cadaveric specimens. Template-guided instrumentation was randomized for each cervical level and side and the contralateral side instrumented likewise but with the freehand technique. No fluoroscopy was used at all, and the spinal canal was not opened for the freehand technique. Accuracy was assessed by computed tomography, grading perforations using a 2-mm increment method, and time efficiency was compared between the 2 techniques. RESULTS: In total, 48 screws were inserted with an equal distribution of 24 screws (50%) in each of the 2 groups. Outer pedicle width averaged 5.1 ± 1.0 mm (range 2.7-7.8); 66.7% (n = 16) of template-guided versus 20.8% (n = 5) of freehand CPS were fully contained within the pedicle (P = 0.001), whereas 91.7% (n = 22) versus 50% (n = 12) were within the <2 mm "safe" zone (P = 0.001). The mean time for instrumentation per level and side was 03:09 ± 01:37 minutes for the template-guided versus 02:32 ± 01:04 minutes for the freehand technique (P = 0.132). CONCLUSIONS: In a cadaver model, template-guided CPS placement has a significantly greater accuracy than the freehand technique. This accuracy is comparable with navigated techniques reported in the literature.

Quantitative MRI of visually intact rotator cuff muscles by multiecho Dixon-based fat quantification and diffusion tensor imaging.

BACKGROUND: Quantitative MRI allows assessment of shoulder rotator cuff (RC) muscles by Dixon MR sequences with calculation of fractional fat content (FF%) maps and diffusion tensor imaging (DTI) including tractography. PURPOSE: To compare FF% and DTI derived parameters among visually intact RC muscles, to compare 2D with 3D DTI measurements and to establish normative values. STUDY TYPE: Prospective. SUBJECTS: Forty patients aged >18 years undergoing shoulder MR arthrography were included. FIELD STRENGTH/SEQUENCE: MR arthrography of the shoulder including 3D multiecho Dixon and 3D echo-planar DTI sequences (15 gradient encoding directions, b-value 600 s/mm2 ) was performed at 3.0T. ASSESSMENT: Muscles affected by RC tears or fatty infiltration of Goutallier grade ≥1 were excluded. Two independent radiologists measured FF%, apparent diffusion coefficient (ADC), and fractional anisotropy (FA) by region-of-interest (ROI) placements at the Y-position of the scapula and 3D tractography of each muscle with qualitative evaluation was performed. STATISTICAL TESTS: Intraclass correlation coefficients (ICCs) and Cohen's kappa were used for interreader agreement and Pearson correlation coefficient to correlate quantitative measures with each other and age, independent-samples t-test, one-way analysis of variance (ANOVA), and Kruskal-Wallis test were performed to investigate differences between genders and muscles. RESULTS: Qualitative and quantitative measurements showed moderate (κ = 0.41-0.56) to almost perfect (ICC = 0.75-0.99) agreement. There were weak but significant positive correlations of FF% with age (r = 0.273, P < 0.05) and FA-2D (r = 0.319-0.383, P < 0.05). Significant differences were found among RC muscles for ADC, radial diffusivity (RD), and tract homogeneity (all P < 0.05) but not between genders (all P ≥ 0.05). High correlations of 2D with 3D measurements for ADC (r = 0.639, P < 0.001) and FA (r = 0.628, P < 0.001) were seen. DATA CONCLUSION: Quantitative MRI with estimation of FF% and DTI parameters shows significant age-associated changes and differences among visually intact RC muscles. High reproducibility and correlations of 2D with 3D DTI measurements can be expected. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:109-117.

Value of standard radiographs, computed tomography, and magnetic resonance imaging of the lumbar spine in detection of intraoperatively confirmed pedicle screw loosening-a prospective clinical trial.

BACKGROUND CONTEXT: Pedicle screw loosening is common after spinal fusion and can be associated with pseudoarthrosis and pain. With suspicion of screw loosening on standard radiographs, CT is currently considered the advanced imaging modality of choice. MRI with new metal artifact reduction techniques holds potential to be sensitive in detection of screw loosening. The sensitivity and specificity of either of the imaging modalities are yet clear. PURPOSE: To evaluate the sensitivity and specificity of three different image modalities (standard radiographs, CT, and MRI) for detection of pedicle screw loosening. STUDY DESIGN/SETTING: Cross-sectional diagnostic study. PATIENT SAMPLE: Forty-one patients (159 pedicle screws) undergoing revision surgeries after lumbar spinal fusion between August 2014 and April 2017 with preoperative radiographs, CT, and MRI with spinal metal artifact reduction (STIR WARP and TSE high bandwidth sequences). OUTCOME MEASURES: Sensitivity and specificity in detection of screw loosening for each imaging modality. METHODS: Screw torque force was measured intraoperatively and compared with preoperative screw loosening signs such as peri-screw edema in MRI and peri-screw osteolysis in CT and radiographs. A torque force of less than 60 Ncm was used to define a screw as loosened. RESULTS: Sensitivity and specificity in detection of screw loosening was 43.9% and 92.1% for MRI, 64.8% and 96.7% for CT, and 54.2% and 83.5% for standard radiographs, respectively. CONCLUSIONS: Despite improvement of MRI with metal artifact reduction MRI technique, CT remains the modality of choice. Even so, CT fails to detect all loosened pedicle screws.

3-T MRI implant safety: heat induction with new dual-channel radiofrequency transmission technology.

We aimed to investigate whether different transmission settings of the dual-transmit technology may influence the amount of heat induction around an implant material dependent on its location within the magnetic field. Metallic hip implants were positioned in the magnet of a 3-T scanner at various lateral offset positions in relation to the magnetic axis in a body-phantom tank filled with polyacrylic acid gel. The temperature increase close to the implants was measured during turbo spin-echo scanning using dual-channel parallel radiofrequency (RF) transmission with circular in comparison to elliptic RF polarization. Circularly polarized transmission (CPT) induced higher temperature increases (maximum 6.2 °C) than elliptically polarized transmission (EPT) (maximum 1.5 °C). The heat induction was dependent on the distance to the isocenter with increased heating by increased distance to the isocenter. EPT showed lower heating around implants compared to the CPT as commonly used in single-transmission system; further, less heating was observed for both transmission settings closer to the magnet isocenter.