Considering Hounsfield Units in native CT- scans for diagnosing spondylodiscitis

Considering Hounsfield Units in native CT- scans for diagnosing spondylodiscitis | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Considering Hounsfield Units in native CT- scans for diagnosing spondylodiscitis Max Prost, Roman Taday, Christian Bernard Matar, David Latz, Carl Christoph Paul Beyersdorf, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3959086/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 02 Sep, 2025 Read the published version in BMC Musculoskeletal Disorders → Version 1 posted 12 You are reading this latest preprint version Abstract Background MRI being the method of choice for radiological diagnosis of spondylodiscitis is still often delayed. The significance of native CT Scans as an alternative diagnostic tool for spondylodiscitis is poor according to the current data. Therefore, the aim of this study was to investigate, weather spondylodiscitis leads to a significant pattern of the density distribution from the affected vertebral bodies and discs measured by Hounsfield Units (HU) in native CT Scans. Methods In a retrospective study we analyzed data from 136 patients, who were treated for spondylodiscitis. Patients who provided MRI- and CT- scans of the spine were included. In axial CT planes HU from the affected intervertebral disc as well as from the affected vertebral bodies and from the unaffected adjacent intervertebral discs and vertebral bodies from the level above and below as reference were measured. Results The average measured HU of the affected disc were 26.0% less than in the not affected adjacent discs (p < 0.001). The average measured HU of the affected vertebral bodies were 33.77% higher than in the not affected adjacent vertebral body’s (p < 0.001)). The localization of the spondylodiscitis and the degree of bony destruction according to Eysel-Peters classification had no influence on these findings. Conclusion Decreased HU of the affected vertebral disc of approximate 25% and / or increased HU of the affected vertebral bodies of approximate 30% compared with adjacent vertebral discs and vertebral are indicative for spondylodiscitis even in early phase without destruction and independent of the localization. Spondylodiscitis diagnostics spinal infections Houndsfield Units Figures Figure 1 Figure 2 Introduction Infections of the spine like spondylitis or spondylodiscitis are rare, but still the third most common form of osteomyelitis. The disease is characterized by a heterogenic clinical presentation accompanied by a variety of differential diagnoses and is therefore often recognized and treated late. This leads to an increased morbidity of the disease and can even become life threatening [ 1 ]. Diagnosing spondylodiscitis or vertebral osteomyelitis is challenging, due to non-specific signs and symptoms on presentation especially at the early stage of the disease. During this early stage of disease conventional imaging modalities can fail to detect subtile changes in vertebral and non- bony surrounding structures [ 2 ]. Recent studies have estimated the delay between the onset of the non-specific symptoms and the diagnosis of spondylodiscitis to an average of 45 days [ 3 ]. Diagnostic imaging is routinely employed as part of the investigative pathway. Magnetic Resonance Imaging (MRI) remains the gold standard imaging in depicting spondylodiscitis, offering a high sensitivity and specificity. When enhanced with intravenous Gadolinium, MRI can differentiate between infection, degeneration, and neoplasia with an accuracy of 95% in it's Short-Tau-Inversion-Recovery-Sequenz (STIR) [ 1 , 2 , 4 , 5 ]. Nevertheless, acquiring high- resolution images through MRI can sometimes be difficult, due to long acquisition time, patient- related contraindications or other logistic issues like access or availability. Further, especially in the eraly stage of the disease, it could be difficult to distinguish between osteocondrosis and spondylodiscitis even in an MRI. Additionally, the indication for obtaining early MRI in a patient with back pain is tied to reasonable suspicion of spondylodiscitis or red flags [ 6 , 7 ]. Alternatively, native or contrast enhanced computed tomography (CT) is rapidly and overall available, faster than MRI and represents the modality of choice for the detection of differential diagnoses of spondylodiscitis with a higher incidence (e.g. osteoporotic fractures, degenerative osteochondrosis) [ 8 , 9 ]. In terms of initial diagnostic imaging for spondylodiscitis, CT scans are currently reserved to analyze the bony destruction and for settings in which performing an MRI is contraindicated, and more expensive nuclear imaging (PET/ CT) is not feasible [ 5 , 6 , 10 ]. This is caused by the fact, that it's accuracy remains significantly lower than MRI and PET/ CT, particularly in early stages. CT is currently used mostly for percutaneous needle biopsy and drainage of abscesses as well as to analyze the bony destruction. [ 1 , 6 , 11 , 12 ]. Nevertheless, measuring local bone quality using CT scans with Hounsfield units (HU) quantification is possible and has been shown to be a reliable method to assess bone density changes for osteoporosis, spondylarthritis and osteochondrosis across all vertebrae [ 13 – 16 ]. The aim of the present study was to analyze an alternative method to diagnose spondylodiscitis whith a native CT Scan. To assas this aim, we want to show whether the measured Hounsfield units (HU) in the infected intervertebral discs and vertebral bodies, in comparison to adjacent non infected spine segements display a significant pattern to be interpreted as a reliable parameter that can predict an infectious entity of the spine. Such a parameter would be a useful tool to aid in the early diagnosis of spondylodiscitis using CT. Patients and methods We performed a retrospective single center data analyis. An existing database of patients who were treated with spondylodiscitis in our institution from 2014–2022 was screened for patients who met our inclusion criteria. We included patients in whom the diagnosis of spondylodiscitis was ensured by MRI, laboratory examination and positive pathogen detection weather with needle guided or intraoperative biopsie or with blood cluture and who had a CT- scan of the affected spine segment. Patients without MRI and patients without or with an incomplete CT of the spine were excluded. The maximal accepted time between MRI an CT Scan was 14 days, if the time between imagig was longer the patients were excluded. Further, we excluded patients who developed spondylodiscitis after spinal surgery with remaining implants. Demographical data like sex and age as well as data according to the localization of the spondylodiscitis were recorded. The radiological degree of destruction caused by the spondylodiscitis was detected and classified according to the Eysel- Peters Classification [ 17 ]. The native spinal CT and MRI were analyzed by the IDS 7-PACS ® -System (Sectra, Linköping, Sweden). The affected intervertebral discs and vertebral bodies were identified in the aviable MRI of the patients. For HU measurement we used a three- dimensional multiplanar reconstruction of the respective spine- CT. To analyze the intervertebral disc we measured the HU in axial CT- planes from the affected intervertebral disc and from the adjacent unaffected intervertebral discs from the one level above and below as reference (Fig. 1 ). For analysis of the vertebral body we measured the HU from the vertebral bodies which were affected by the spondylodiscitis (above and below the affected intervertebral disc) and the HU from the unaffected adjacent vertebral bodies from the level above and below as reference. HU measuremente of the vertebral bodies were taken at from three cross-sectional slices at the level of the cover plate, in the middle of the vertebral body and close to the ground plate (Fig. 1 ). Lateral reconstruction of an lumbar spine CT Scan. In the aviable MRI Scan of this patient the intervertebral disc between L2 and L3 showed inflammatory changes and was set and mesured as affectet intervertebral disc (with bar). The intervertebral disc one segement above and one segment below were set and mesuered as reference. The black bars show the localization of the performed measurements in the vertebral bodies which were affected by the spondylodiscitis. The unaffected adjacent vertebral bodies from the level above and below as reference. The mean of this three measurements was calculated and analyzed. In the axial CT- planes a circular region of interest was selected based on manually defined reference lines, having a diameter of app. 75% of the anteroposterior and transverse diameters of the vertebral body or the intervertebral disc ( Fig. 2 ). Axial reconstruction of an lumbar spine CT Scan. A circular region of interest was selected based on manually defined reference lines, having a diameter of app. 75% of the anteroposterior and transverse diameters of the vertebral body or the intervertebral disc. The average HU within the sample region was displayed by the software. A shows exemplary a performed measurement in a vertebral disc. B shows a performed measurement in a vertebral body. The average HU within the sample region was displayed by the software. The measurements were performed according to the technique described by Schreiber et. al in 2011. [ 15 ] Statistical analysis: Statistical analysis was performed by SPSS ® 27 (IBM, Armonk, USA). Descriptive data are given as mean and standard deviation (SD). We tested all continuous variables for normal distribution by Kolmogorov– Smirnov test. Variables that showed normal distribution were analyzed by t-test and variables, which showed no normal distribution, were analyzed by Wilcoxon signed-rank test. This study was approved by the local ethics committee (Register number 2020 − 914_1) and was conducted according to the revised Declaration of Helsinki. Results From the 246 patients with spondylodiscitis in our database we identified 136 patients who met our inclusion criteria. 110 patients could not be included due to incomplete set of radiological data or due to postoperative spondylodiscitis with remaining implants. 44 patients were female (32.4%), 92 patients were male (67.6%). The average age of the patients was 66.86 (13.08) years. 9 (6.6%) patients had a spondylodiscitis located in the cervical spine, 50 (36.8%) were located in the thoracic and 77 (56.6%) in the lumbar spine. According to the Eysel-Peters Classification 57 (41.9%) patients were classified as type 1, 55 (40.4%) as type 2 and 24 (17.6%) as type 3. The average measured HU of the affected disc were 26.0% less than in the not affected adjacent discs (73.4(29.2) vs. 99.1 (26.5)). The difference was significant (p < 0.001). The average measured HU of the affected vertebral bodies were 33.8% higher than in the not affected adjacent vertebral body’s (246.8 (81.2) vs. 184.5 (64.7). The difference was significant (p < 0.001). In a subgroup analysis in which we analyzed the difference of the measured HU from the affected discs and vertebral bodies depending on the Eysel-Peters Classification, the measured HU of the affected disc were significant less than in the not affected adjacent discs independent of the Eysel-Peters type. The measured parameters for the discs were shown in Table 1 . Table 1 Measured HU of the affected and not affected adjacent vertebral disc depending on the Eysel- Peters Classficiation. The measured HU of the affected vertebral bodies were significant higher than in the not affected adjacent vertebral bodies in patients with a spondylodiscitis type Eysel-Peters 1 and 2. In the patients with a type 3 spondylodiscitis, the difference was not significant. The measured parameters for the vertebral bodies were shown in Table 2 . Affected disc Type EP 1 Not affected adjacent disc Type EP 1 Affected disc Type EP 2 Not affected adjacent disc Type EP 2 Affected Disc Type EP 3 Not affected adjacent disc Type EP 3 Mean 71.9 96.6 74.7 102.5 73.9 97.4 SD 30.3 23.2 29.9 30.4 26.0 24.2 Significance p < 0.001 p < 0.001 p < 0.05 Table 2 Measured HU of the affected and not affected adjacent vertebral bodies (VB) depending on the Eysel- Peters Classification. In a further subgroup analysis, we analyzed the difference of the measured HU from the affected discs and vertebral bodies depending on the localization of the spondylodiscitis. The measured HU of the affected discs were significantly less than in the not affected adjacent discs independent of the localization. The measured parameters for the discs were shown in Table 3 . Affected VB Type EP 1 Not affected adjacent VB Type EP 1 Affected VB Type EP 2 Not affected adjacent VB Type EP 2 Affected VB Type EP 3 Not affected adjacent VB Type EP 3 Mean 236.0 178.1 241.4 184.6 284.7 199.2 SD 93.1 68.6 67.3 63.5 71.5 57.7 Significance p < 0.001 p 0.05 Table 3 Measured HU of the affected and not affected adjacent vertebral disc depending on localization. The measured HU of the affected vertebral bodies were significant higher than in the not affected adjacent vertebral bodies independent of the localization. The measured parameters for the vertebral bodies were shown in Table 4 . Affected disc cervical spine Not affected adjacent disc cervical spine Affected disc thoracic spine Not affected adjacent disc thoracic spine Affected disc lumbar spine Not affected adjacent disc Lumbar spine Mean 94.7 115.4 81.2 108.5 63.0 87.7 SD 33.5 21.3 31.5 26.9 24.7 19.4 Significance p < 0.005 p < 0.001 p < 0.001 Table 4 Measured HU of the affected and not affected adjacent vertebral bodies (VB) depending on the localization Affected VB cervical spine Not affected adjacent VB cervical spine Affected VB thoracic spine Not affected adjacent VB thoracic spine Affected VB lumbar spine Not affected adjacent VB Lumbar spine Mean 362.4 271.3 266.9 81.6 211.4 166.6 SD 73.2 50.5 195.6 62.4 64.6 60.5 Significance p < 0.05 p < 0.05 p < 0.001 Discussion In clinical practice, back pain is a common disease closely related to the degeneration of the spine. Among differential diagnoses, spondylodiscitis is a rarity, but the most common form of osteomyelitis in patients over 50 years of age. For spondylodiscitis a mortalitiy rate of 15–20% is described [ 10 ]. The reason for this is the often long period between the onset of the disease and the final diagnosis, as the heterogenic and unspecific symptoms accompanied by a variety of differential diagnosis and the lack of clear clinical signs delay the initiation of therapy [ 3 , 10 ]. Early diagnosis and rapid initiation of specific antibiotic therapy are therefore the most important cornerstones in the treatment of spondylodiscitis [ 1 , 6 , 10 ]. MRI is the gold standard for imaging detection of spondylodiscitis, offering high sensitivity and specificity even in early stages of the disease [ 4 , 5 ]. For patients with unclear spinal symptoms the first imaging modality is conventional radiological imaging of the corresponding spinal segment like X- ray or CT- scan [ 6 ]. A justified indication for obtaining early MRI in a patient with back pain is obligatory tied to a reasonable suspicion of spondylodiscitis or red flags, due to high cost, long acquisition time or patient- related contraindications [ 4 , 6 , 7 ]. The performance of a (low-dose) CT scan for initial diagnostics represents the modalitiy of choice in depicting differential diagnoses and an alternative in the case of contraindications to MRI or an additional diagnostic when justified indication for MRI is not given (non-MR-capable pacemakers, other patient-dependent factors) or a MRI is not avaiable. Conventional imaging like x- ray and CT- scans can be used for general bone quality assessment. Hounsfield Units (HU) value assessed in CT- scans have a significantly positive correlation with bone mass density of endplates [ 14 , 15 , 18 , 19 ]. Although inaccuracies related to geometry and basic radiation physics principles (a.e. noisy images, variability in axial slices) exist, the value of the Hounsfield units measurements appear to be a reliable predicting bone mineral density changes of trabecular bone and the density of intervertebral disc [ 14 , 15 , 18 ]. This study found, that HU values of the affected discs are significantly lower than those of the adjacent discs above and below it, especially in earlier stages such as Eysel I or II ( Table 1 ) . Moreover, our findings show that the HU values of the affected vertebra above and below the infected intervertebral disc are significantly higher than those of the corresponding regions in adjacent vertebra regardless of the endplate and bone marrow region ( Table 2 ). These findings were independent of the localization within the spine ( Table 3 , 4 ). Lower HU values of the disc accompanied by higher HU values of the affected vertebrae than the HU values of the adjacent vertebral sections, indicate degeneration of the affected disc with consecutive osteosclerosis of the adjacent vertebrae in spondylodiscitis. These findings were significant in this study for early stages like Eysel I and II. This might be explained by infection triggered disc destruction accompanied by reactive osteosclerosis and increased bone marrow eadema of the adjacent vertebrae [ 20 ]. Due to the fact, that especially in these early stage of the disease, it could be difficult to distinguish between osteocondrosis and spondylodiscitis in a MRI, the results of our investigation present an important diagnostic tool to improve diagnosing spondylodiscitis. The increasing erosion and destruction of the vertebral bodies associated with a higher grade of spondylodiscitis mixed with reactive bracing bone formations explains the decreasing significance of the results for grades like Eysel III. As the infection progressively influences the vertebral bodies, there appears to be a heterogeneous change in HU. The presence of spondylodiscitis is often indistinguishable from osteochondrosis on native radiologic imaging [ 10 , 21 ]. Nonetheless, previous studies showed, that higher grades of disc degeneration were correlated with attenuation of the adjacent vertebrae's HU values. The HU values of the adjacent vertebrae showed a tendency of decrease along the aggravation of disc degeneration or had no significant correlation of endplate's HU value and the aggravation of the disc degeneration [ 16 , 18 , 21 – 24 ]. There were some limitiations to this study. First of all this study is a single- center, retrospective analysis. No conclusions can be drawn regarding the sensitivity and specificity of HU examination in spondylodiscitis. There is no direct comparison in relation to osteochondrosis of the spine. However, the combination of elevated inflammation values (elevated CRP, leucocytes, BSR) in laboratory findings [ 1 , 6 , 10 ] and CT findings as presented in this study may increase the suspicion of spondylodiscitis and support the justification of rapid MRI examinations, possibly reducing the delay until diagnosis. Conclusion To our knowledge this is the first study to HU analysis in CT scans in spondylodiscitis. Decreased HU of the affected vertebral disc of approximate 25% and / or increased HU of the affected vertebral bodies of approximate 30% compared with adjacent vertebral discs and vertebral bodies in a native spinal CT scan are indicative for spondylodiscitis even in early phase without destruction and independent of the localization. Suspicion for spondylodiscitis can be corroborated by elevated inflammation values in the laboratory findings. Abbreviations MRI Magnetic Resonance Imaging CT Computed tomography PET/ CT Positron Emission Tomography SEM Standard error of mean HU Hounsfield Units SD Standard deviation STIR Short- Tau- Inversion- Recovery VB Vertebral Bodv Declarations Ethical Approval and consent to participate Due to the retrospective nature of the study, the need for informed consent was waived by the local ethics committee of the Medical Faculty and University Hospital Düsseldorf (Register number 2020-914_1). This study was approved by the local ethics committee and was conducted according to the revised declaration of Helsinki Consent to Publication Not applicable because of the retrospective design of the investigation Data Availability statement The datasets generated during and / or analyzed during the current study are not publicly available due to data protection but are available from the corresponding author on reasonable request. Conflict of interest MP reports personal fees from Stryker and Medtronic, outside the submitted work RT none CBM none DL none CCPB none MER none JW none MJS none The other authors declare no conflict of interest relevant to this work. Funding No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article Acknowledgment Not applicable / No Acknowledgment Author contribution MP: Conception and design, administrative support, Collection and assembly of data, Provision of study materials or patients, Data analysis and interpretation, Manuscript writing, Final approval of manuscript. RT: Administrative support, Collection and assembly of data, Provision of study materials or patients, Data analysis and interpretation, Manuscript writing, Final approval of manuscript. CBM: Administrative support, Collection and assembly of data, Data analysis and interpretation, final approval of manuscript. DL: Administrative support, Collection and assembly of data, Data analysis and interpretation, final approval of manuscript. MER: Administrative support, Collection and assembly of data, Data analysis and interpretation, final approval of manuscript. CCPB: Administrative support, Collection and assembly of data, Data analysis and interpretation, final approval of manuscript. JW: Administrative support, Provision of study materials or patients, Manuscript writing, Final approval of manuscript. MJS: Conception and design, administrative support, Collection and assembly of data, Provision of study materials or patients, Data analysis and interpretation, Manuscript writing, Final approval of manuscript. References Herren C, Jung N, Pishnamaz M et al. Spondylodiscitis: Diagnosis and Treatment Options. Dtsch Ärztebl Int . Epub ahead of print 25 December 2017. 10.3238/arztebl.2017.0875 . Maamari J, Grach SL, Passerini M, et al. The use of MRI, PET/CT, and nuclear scintigraphy in the imaging of pyogenic native vertebral osteomyelitis: a systematic review and meta-analysis. Spine J. 2023;23:868–76. 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Cite Share Download PDF Status: Published Journal Publication published 02 Sep, 2025 Read the published version in BMC Musculoskeletal Disorders → Version 1 posted Editorial decision: Revision requested 10 Dec, 2024 Reviews received at journal 02 Jul, 2024 Reviewers agreed at journal 02 Jul, 2024 Reviews received at journal 01 Jul, 2024 Reviews received at journal 29 Jun, 2024 Reviewers agreed at journal 28 Jun, 2024 Reviewers agreed at journal 19 Jun, 2024 Reviewers invited by journal 19 Jun, 2024 Editor assigned by journal 11 Jun, 2024 Editor invited by journal 27 Feb, 2024 Submission checks completed at journal 27 Feb, 2024 First submitted to journal 15 Feb, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Düsseldorf","correspondingAuthor":false,"prefix":"","firstName":"Roman","middleName":"","lastName":"Taday","suffix":""},{"id":275186257,"identity":"eaa43e07-d44f-4cd1-a1e2-1e765bca3ce4","order_by":2,"name":"Christian Bernard Matar","email":"","orcid":"","institution":"University Hospital Düsseldorf, Heinrich- Heine-University Düsseldorf","correspondingAuthor":false,"prefix":"","firstName":"Christian","middleName":"Bernard","lastName":"Matar","suffix":""},{"id":275186258,"identity":"c22bd546-d4c8-463e-9ca9-0e43d8988837","order_by":3,"name":"David Latz","email":"","orcid":"","institution":"University Hospital Düsseldorf, Heinrich- Heine-University Düsseldorf","correspondingAuthor":false,"prefix":"","firstName":"David","middleName":"","lastName":"Latz","suffix":""},{"id":275186259,"identity":"ee875f85-d832-44d0-b33d-ef9d6ec627ca","order_by":4,"name":"Carl Christoph Paul Beyersdorf","email":"","orcid":"","institution":"University Hospital Düsseldorf, Heinrich- Heine-University Düsseldorf","correspondingAuthor":false,"prefix":"","firstName":"Carl","middleName":"Christoph Paul","lastName":"Beyersdorf","suffix":""},{"id":275186260,"identity":"3d954b46-04fd-4680-a781-d114586d575e","order_by":5,"name":"Melanie Elisabeth Röckner","email":"","orcid":"","institution":"University Hospital Düsseldorf, Heinrich- Heine-University Düsseldorf","correspondingAuthor":false,"prefix":"","firstName":"Melanie","middleName":"Elisabeth","lastName":"Röckner","suffix":""},{"id":275186261,"identity":"c760b818-4308-46d6-8c35-2821df02d6b5","order_by":6,"name":"Joachim Windolf","email":"","orcid":"","institution":"University Hospital Düsseldorf, Heinrich- Heine-University Düsseldorf","correspondingAuthor":false,"prefix":"","firstName":"Joachim","middleName":"","lastName":"Windolf","suffix":""},{"id":275186262,"identity":"3a475a20-6b25-4239-b7e7-23e88a0289b7","order_by":7,"name":"Max Joseph Scheyerer","email":"","orcid":"","institution":"University Hospital Düsseldorf, Heinrich- Heine-University Düsseldorf","correspondingAuthor":false,"prefix":"","firstName":"Max","middleName":"Joseph","lastName":"Scheyerer","suffix":""}],"badges":[],"createdAt":"2024-02-15 15:49:57","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3959086/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3959086/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12891-025-09106-9","type":"published","date":"2025-09-02T15:58:04+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":51970046,"identity":"0b0c72e3-d0b7-4187-98ac-f2bcf250841d","added_by":"auto","created_at":"2024-03-04 18:46:15","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":24707,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eLocalisation of the performed measurements\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3959086/v1/d03938659417e05b347a4420.jpg"},{"id":51970047,"identity":"5cf46936-7dfc-426c-8581-8e625868e0cd","added_by":"auto","created_at":"2024-03-04 18:46:15","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":46763,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMesurement of the HU in the vertebral discs and the verbetral bodies\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3959086/v1/de5ae0de17f85b6edda0f4e8.jpg"},{"id":90827994,"identity":"34544667-fcdb-4486-85f7-b9cf46492d65","added_by":"auto","created_at":"2025-09-08 16:04:53","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":875974,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3959086/v1/a30b2dd8-5be2-4a6c-a4cd-c8b54af7bbb9.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Considering Hounsfield Units in native CT- scans for diagnosing spondylodiscitis","fulltext":[{"header":"Introduction","content":"\u003cp\u003eInfections of the spine like spondylitis or spondylodiscitis are rare, but still the third most common form of osteomyelitis. The disease is characterized by a heterogenic clinical presentation accompanied by a variety of differential diagnoses and is therefore often recognized and treated late. This leads to an increased morbidity of the disease and can even become life threatening [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Diagnosing spondylodiscitis or vertebral osteomyelitis is challenging, due to non-specific signs and symptoms on presentation especially at the early stage of the disease. During this early stage of disease conventional imaging modalities can fail to detect subtile changes in vertebral and non- bony surrounding structures [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Recent studies have estimated the delay between the onset of the non-specific symptoms and the diagnosis of spondylodiscitis to an average of 45 days [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Diagnostic imaging is routinely employed as part of the investigative pathway. Magnetic Resonance Imaging (MRI) remains the gold standard imaging in depicting spondylodiscitis, offering a high sensitivity and specificity. When enhanced with intravenous Gadolinium, MRI can differentiate between infection, degeneration, and neoplasia with an accuracy of 95% in it's Short-Tau-Inversion-Recovery-Sequenz (STIR) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Nevertheless, acquiring high- resolution images through MRI can sometimes be difficult, due to long acquisition time, patient- related contraindications or other logistic issues like access or availability. Further, especially in the eraly stage of the disease, it could be difficult to distinguish between osteocondrosis and spondylodiscitis even in an MRI. Additionally, the indication for obtaining early MRI in a patient with back pain is tied to reasonable suspicion of spondylodiscitis or red flags [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Alternatively, native or contrast enhanced computed tomography (CT) is rapidly and overall available, faster than MRI and represents the modality of choice for the detection of differential diagnoses of spondylodiscitis with a higher incidence (e.g. osteoporotic fractures, degenerative osteochondrosis) [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. In terms of initial diagnostic imaging for spondylodiscitis, CT scans are currently reserved to analyze the bony destruction and for settings in which performing an MRI is contraindicated, and more expensive nuclear imaging (PET/ CT) is not feasible [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. This is caused by the fact, that it's accuracy remains significantly lower than MRI and PET/ CT, particularly in early stages. CT is currently used mostly for percutaneous needle biopsy and drainage of abscesses as well as to analyze the bony destruction. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Nevertheless, measuring local bone quality using CT scans with Hounsfield units (HU) quantification is possible and has been shown to be a reliable method to assess bone density changes for osteoporosis, spondylarthritis and osteochondrosis across all vertebrae [\u003cspan additionalcitationids=\"CR14 CR15\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The aim of the present study was to analyze an alternative method to diagnose spondylodiscitis whith a native CT Scan. To assas this aim, we want to show whether the measured Hounsfield units (HU) in the infected intervertebral discs and vertebral bodies, in comparison to adjacent non infected spine segements display a significant pattern to be interpreted as a reliable parameter that can predict an infectious entity of the spine. Such a parameter would be a useful tool to aid in the early diagnosis of spondylodiscitis using CT.\u003c/p\u003e"},{"header":"Patients and methods","content":"\u003cp\u003eWe performed a retrospective single center data analyis. An existing database of patients who were treated with spondylodiscitis in our institution from 2014\u0026ndash;2022 was screened for patients who met our inclusion criteria. We included patients in whom the diagnosis of spondylodiscitis was ensured by MRI, laboratory examination and positive pathogen detection weather with needle guided or intraoperative biopsie or with blood cluture and who had a CT- scan of the affected spine segment. Patients without MRI and patients without or with an incomplete CT of the spine were excluded. The maximal accepted time between MRI an CT Scan was 14 days, if the time between imagig was longer the patients were excluded. Further, we excluded patients who developed spondylodiscitis after spinal surgery with remaining implants.\u003c/p\u003e \u003cp\u003eDemographical data like sex and age as well as data according to the localization of the spondylodiscitis were recorded. The radiological degree of destruction caused by the spondylodiscitis was detected and classified according to the Eysel- Peters Classification [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The native spinal CT and MRI were analyzed by the IDS 7-PACS\u003csup\u003e\u0026reg;\u003c/sup\u003e-System (Sectra, Link\u0026ouml;ping, Sweden). The affected intervertebral discs and vertebral bodies were identified in the aviable MRI of the patients. For HU measurement we used a three- dimensional multiplanar reconstruction of the respective spine- CT. To analyze the intervertebral disc we measured the HU in axial CT- planes from the affected intervertebral disc and from the adjacent unaffected intervertebral discs from the one level above and below as reference (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). For analysis of the vertebral body we measured the HU from the vertebral bodies which were affected by the spondylodiscitis (above and below the affected intervertebral disc) and the HU from the unaffected adjacent vertebral bodies from the level above and below as reference. HU measuremente of the vertebral bodies were taken at from three cross-sectional slices at the level of the cover plate, in the middle of the vertebral body and close to the ground plate (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eLateral reconstruction of an lumbar spine CT Scan. In the aviable MRI Scan of this patient the intervertebral disc between L2 and L3 showed inflammatory changes and was set and mesured as affectet intervertebral disc (with bar). The intervertebral disc one segement above and one segment below were set and mesuered as reference. The black bars show the localization of the performed measurements in the vertebral bodies which were affected by the spondylodiscitis. The unaffected adjacent vertebral bodies from the level above and below as reference.\u003c/p\u003e \u003cp\u003eThe mean of this three measurements was calculated and analyzed. In the axial CT- planes a circular region of interest was selected based on manually defined reference lines, having a diameter of app. 75% of the anteroposterior and transverse diameters of the vertebral body or the intervertebral disc \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAxial reconstruction of an lumbar spine CT Scan. A circular region of interest was selected based on manually defined reference lines, having a diameter of app. 75% of the anteroposterior and transverse diameters of the vertebral body or the intervertebral disc. The average HU within the sample region was displayed by the software. A shows exemplary a performed measurement in a vertebral disc. B shows a performed measurement in a vertebral body.\u003c/p\u003e \u003cp\u003eThe average HU within the sample region was displayed by the software. The measurements were performed according to the technique described by Schreiber et. al in 2011. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis:\u003c/h2\u003e \u003cp\u003eStatistical analysis was performed by SPSS\u003csup\u003e\u0026reg;\u003c/sup\u003e 27 (IBM, Armonk, USA). Descriptive data are given as mean and standard deviation (SD). We tested all continuous variables for normal distribution by Kolmogorov\u0026ndash; Smirnov test. Variables that showed normal distribution were analyzed by t-test and variables, which showed no normal distribution, were analyzed by Wilcoxon signed-rank test.\u003c/p\u003e \u003cp\u003e This study was approved by the local ethics committee (Register number 2020\u0026thinsp;\u0026minus;\u0026thinsp;914_1) and was conducted according to the revised Declaration of Helsinki.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eFrom the 246 patients with spondylodiscitis in our database we identified 136 patients who met our inclusion criteria. 110 patients could not be included due to incomplete set of radiological data or due to postoperative spondylodiscitis with remaining implants.\u003c/p\u003e \u003cp\u003e44 patients were female (32.4%), 92 patients were male (67.6%). The average age of the patients was 66.86 (13.08) years. 9 (6.6%) patients had a spondylodiscitis located in the cervical spine, 50 (36.8%) were located in the thoracic and 77 (56.6%) in the lumbar spine.\u003c/p\u003e \u003cp\u003eAccording to the Eysel-Peters Classification 57 (41.9%) patients were classified as type 1, 55 (40.4%) as type 2 and 24 (17.6%) as type 3.\u003c/p\u003e \u003cp\u003eThe average measured HU of the affected disc were 26.0% less than in the not affected adjacent discs (73.4(29.2) vs. 99.1 (26.5)). The difference was significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003eThe average measured HU of the affected vertebral bodies were 33.8% higher than in the not affected adjacent vertebral body\u0026rsquo;s (246.8 (81.2) vs. 184.5 (64.7). The difference was significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003eIn a subgroup analysis in which we analyzed the difference of the measured HU from the affected discs and vertebral bodies depending on the Eysel-Peters Classification, the measured HU of the affected disc were significant less than in the not affected adjacent discs independent of the Eysel-Peters type. The measured parameters for the discs were shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMeasured HU of the affected and not affected adjacent vertebral disc depending on the Eysel- Peters Classficiation. The measured HU of the affected vertebral bodies were significant higher than in the not affected adjacent vertebral bodies in patients with a spondylodiscitis type Eysel-Peters 1 and 2. In the patients with a type 3 spondylodiscitis, the difference was not significant. The measured parameters for the vertebral bodies were shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAffected disc\u003c/p\u003e \u003cp\u003eType EP 1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNot affected adjacent disc\u003c/p\u003e \u003cp\u003eType EP 1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAffected disc\u003c/p\u003e \u003cp\u003eType EP 2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNot affected adjacent disc\u003c/p\u003e \u003cp\u003eType EP 2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAffected Disc\u003c/p\u003e \u003cp\u003eType EP 3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eNot affected adjacent disc\u003c/p\u003e \u003cp\u003eType EP 3\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e71.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e96.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e74.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e102.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e73.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e97.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e29.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e30.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e26.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e24.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSignificance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMeasured HU of the affected and not affected adjacent vertebral bodies (VB) depending on the Eysel- Peters Classification. In a further subgroup analysis, we analyzed the difference of the measured HU from the affected discs and vertebral bodies depending on the localization of the spondylodiscitis. The measured HU of the affected discs were significantly less than in the not affected adjacent discs independent of the localization. The measured parameters for the discs were shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAffected VB\u003c/p\u003e \u003cp\u003eType EP 1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNot affected adjacent VB\u003c/p\u003e \u003cp\u003eType EP 1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAffected VB\u003c/p\u003e \u003cp\u003eType EP 2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNot affected adjacent VB\u003c/p\u003e \u003cp\u003eType EP 2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAffected VB\u003c/p\u003e \u003cp\u003eType EP 3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eNot affected adjacent VB\u003c/p\u003e \u003cp\u003eType EP 3\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e236.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e178.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e241.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e184.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e284.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e199.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e93.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e68.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e67.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e63.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e71.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e57.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSignificance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMeasured HU of the affected and not affected adjacent vertebral disc depending on localization. The measured HU of the affected vertebral bodies were significant higher than in the not affected adjacent vertebral bodies independent of the localization. The measured parameters for the vertebral bodies were shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAffected disc\u003c/p\u003e \u003cp\u003ecervical spine\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNot affected adjacent disc\u003c/p\u003e \u003cp\u003ecervical spine\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAffected disc\u003c/p\u003e \u003cp\u003ethoracic spine\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNot affected adjacent disc\u003c/p\u003e \u003cp\u003ethoracic spine\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAffected disc\u003c/p\u003e \u003cp\u003elumbar spine\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eNot affected adjacent disc\u003c/p\u003e \u003cp\u003eLumbar spine\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e94.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e115.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e81.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e108.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e63.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e87.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e33.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e31.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e26.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e24.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e19.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSignificance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMeasured HU of the affected and not affected adjacent vertebral bodies (VB) depending on the localization\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAffected VB\u003c/p\u003e \u003cp\u003ecervical spine\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNot affected adjacent VB\u003c/p\u003e \u003cp\u003ecervical spine\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAffected VB\u003c/p\u003e \u003cp\u003ethoracic spine\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNot affected adjacent VB\u003c/p\u003e \u003cp\u003ethoracic spine\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eAffected VB\u003c/p\u003e \u003cp\u003elumbar spine\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eNot affected adjacent VB\u003c/p\u003e \u003cp\u003eLumbar spine\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e362.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e271.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e266.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e81.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e211.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e166.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e73.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e195.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e62.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e64.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e60.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSignificance\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn clinical practice, back pain is a common disease closely related to the degeneration of the spine. Among differential diagnoses, spondylodiscitis is a rarity, but the most common form of osteomyelitis in patients over 50 years of age. For spondylodiscitis a mortalitiy rate of 15\u0026ndash;20% is described [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The reason for this is the often long period between the onset of the disease and the final diagnosis, as the heterogenic and unspecific symptoms accompanied by a variety of differential diagnosis and the lack of clear clinical signs delay the initiation of therapy [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Early diagnosis and rapid initiation of specific antibiotic therapy are therefore the most important cornerstones in the treatment of spondylodiscitis [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. MRI is the gold standard for imaging detection of spondylodiscitis, offering high sensitivity and specificity even in early stages of the disease [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. For patients with unclear spinal symptoms the first imaging modality is conventional radiological imaging of the corresponding spinal segment like X- ray or CT- scan [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. A justified indication for obtaining early MRI in a patient with back pain is obligatory tied to a reasonable suspicion of spondylodiscitis or red flags, due to high cost, long acquisition time or patient- related contraindications [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The performance of a (low-dose) CT scan for initial diagnostics represents the modalitiy of choice in depicting differential diagnoses and an alternative in the case of contraindications to MRI or an additional diagnostic when justified indication for MRI is not given (non-MR-capable pacemakers, other patient-dependent factors) or a MRI is not avaiable. Conventional imaging like x- ray and CT- scans can be used for general bone quality assessment. Hounsfield Units (HU) value assessed in CT- scans have a significantly positive correlation with bone mass density of endplates [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Although inaccuracies related to geometry and basic radiation physics principles (a.e. noisy images, variability in axial slices) exist, the value of the Hounsfield units measurements appear to be a reliable predicting bone mineral density changes of trabecular bone and the density of intervertebral disc [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. This study found, that HU values of the affected discs are significantly lower than those of the adjacent discs above and below it, especially in earlier stages such as Eysel I or II \u003cem\u003e(\u003c/em\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cem\u003e)\u003c/em\u003e. Moreover, our findings show that the HU values of the affected vertebra above and below the infected intervertebral disc are significantly higher than those of the corresponding regions in adjacent vertebra regardless of the endplate and bone marrow region \u003cem\u003e(\u003c/em\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cem\u003e).\u003c/em\u003e These findings were independent of the localization within the spine \u003cem\u003e(\u003c/em\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, \u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cem\u003e).\u003c/em\u003e Lower HU values of the disc accompanied by higher HU values of the affected vertebrae than the HU values of the adjacent vertebral sections, indicate degeneration of the affected disc with consecutive osteosclerosis of the adjacent vertebrae in spondylodiscitis. These findings were significant in this study for early stages like Eysel I and II. This might be explained by infection triggered disc destruction accompanied by reactive osteosclerosis and increased bone marrow eadema of the adjacent vertebrae [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Due to the fact, that especially in these early stage of the disease, it could be difficult to distinguish between osteocondrosis and spondylodiscitis in a MRI, the results of our investigation present an important diagnostic tool to improve diagnosing spondylodiscitis. The increasing erosion and destruction of the vertebral bodies associated with a higher grade of spondylodiscitis mixed with reactive bracing bone formations explains the decreasing significance of the results for grades like Eysel III. As the infection progressively influences the vertebral bodies, there appears to be a heterogeneous change in HU. The presence of spondylodiscitis is often indistinguishable from osteochondrosis on native radiologic imaging [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Nonetheless, previous studies showed, that higher grades of disc degeneration were correlated with attenuation of the adjacent vertebrae's HU values. The HU values of the adjacent vertebrae showed a tendency of decrease along the aggravation of disc degeneration or had no significant correlation of endplate's HU value and the aggravation of the disc degeneration [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan additionalcitationids=\"CR22 CR23\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. There were some limitiations to this study. First of all this study is a single- center, retrospective analysis. No conclusions can be drawn regarding the sensitivity and specificity of HU examination in spondylodiscitis. There is no direct comparison in relation to osteochondrosis of the spine. However, the combination of elevated inflammation values (elevated CRP, leucocytes, BSR) in laboratory findings [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] and CT findings as presented in this study may increase the suspicion of spondylodiscitis and support the justification of rapid MRI examinations, possibly reducing the delay until diagnosis.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eTo our knowledge this is the first study to HU analysis in CT scans in spondylodiscitis. Decreased HU of the affected vertebral disc of approximate 25% and / or increased HU of the affected vertebral bodies of approximate 30% compared with adjacent vertebral discs and vertebral bodies in a native spinal CT scan are indicative for spondylodiscitis even in early phase without destruction and independent of the localization. Suspicion for spondylodiscitis can be corroborated by elevated inflammation values in the laboratory findings.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eMRI\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Magnetic Resonance Imaging\u003c/p\u003e\n\u003cp\u003eCT\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Computed tomography\u003c/p\u003e\n\u003cp\u003ePET/ CT \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Positron Emission Tomography\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSEM \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Standard error of mean\u003c/p\u003e\n\u003cp\u003eHU \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Hounsfield Units\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSD \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Standard deviation\u003c/p\u003e\n\u003cp\u003eSTIR \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Short- Tau- Inversion- Recovery\u003c/p\u003e\n\u003cp\u003eVB \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Vertebral Bodv\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eEthical Approval and consent to participate\u003c/p\u003e\n\u003cp\u003eDue to the retrospective nature of the study, the need for informed consent was waived by the local ethics committee of the Medical Faculty and University Hospital D\u0026uuml;sseldorf (Register number 2020-914_1). This study was approved by the local ethics committee and was conducted according to the revised declaration of Helsinki\u003c/p\u003e\n\u003cp\u003eConsent to Publication\u003c/p\u003e\n\u003cp\u003eNot applicable because of the retrospective design of the investigation\u003c/p\u003e\n\u003cp\u003eData Availability statement\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and / or analyzed during the current study are not publicly available due to data protection but are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003eConflict of interest\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMP reports personal fees from Stryker and Medtronic, outside the submitted work\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eRT none\u003c/p\u003e\n\u003cp\u003eCBM none\u003c/p\u003e\n\u003cp\u003eDL none\u003c/p\u003e\n\u003cp\u003eCCPB none\u003c/p\u003e\n\u003cp\u003eMER none\u003c/p\u003e\n\u003cp\u003eJW none\u003c/p\u003e\n\u003cp\u003eMJS none\u003c/p\u003e\n\u003cp\u003eThe other authors declare no conflict of interest relevant to this work.\u003c/p\u003e\n\u003cp\u003eFunding\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNo benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article\u003c/p\u003e\n\u003cp\u003eAcknowledgment\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNot applicable / No Acknowledgment\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAuthor contribution\u003c/p\u003e\n\u003cp\u003eMP: Conception and design, administrative support, Collection and assembly of data, Provision of study materials or patients, Data analysis and interpretation, Manuscript writing, Final approval of manuscript.\u003c/p\u003e\n\u003cp\u003eRT: Administrative support, Collection and assembly of data, Provision of study materials or patients, Data analysis and interpretation, Manuscript writing, Final approval of manuscript.\u003c/p\u003e\n\u003cp\u003eCBM: Administrative support, Collection and assembly of data, Data analysis and interpretation, final approval of manuscript.\u003c/p\u003e\n\u003cp\u003eDL: Administrative support, Collection and assembly of data, Data analysis and interpretation, final approval of manuscript.\u003c/p\u003e\n\u003cp\u003eMER: Administrative support, Collection and assembly of data, Data analysis and interpretation, final approval of manuscript.\u003c/p\u003e\n\u003cp\u003eCCPB: Administrative support, Collection and assembly of data, Data analysis and interpretation, final approval of manuscript.\u003c/p\u003e\n\u003cp\u003eJW: Administrative support, Provision of study materials or patients, Manuscript writing, Final approval of manuscript.\u003c/p\u003e\n\u003cp\u003eMJS: Conception and design, administrative support, Collection and assembly of data, Provision of study materials or patients, Data analysis and interpretation, Manuscript writing, Final approval of manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cbr\u003e \u003c/strong\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHerren C, Jung N, Pishnamaz M et al. 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J Bone Jt Surg. 2011;93:1057\u0026ndash;63.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhu J, Wu H, Chen Y, et al. The correlation between the change of Hounsfield units value and Modic changes in the lumbar vertebral endplate. BMC Musculoskelet Disord. 2021;22:509.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStein G, Eysel P, Scheyerer MJ, editors. \u003cem\u003eExpertise Orthop\u0026auml;die und Unfallchirurgie Wirbels\u0026auml;ule\u003c/em\u003e. Stuttgart: Georg Thieme.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiang X, Liu Q, Xu J, et al. Hounsfield Unit for Assessing Bone Mineral Density Distribution Within Cervical Vertebrae and Its Correlation With the Intervertebral Disc Degeneration. Front Endocrinol. 2022;13:920167.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHendrickson NR, Pickhardt PJ, Del Rio AM, et al. Bone Mineral Density T-Scores Derived from CT Attenuation Numbers (Hounsfield Units): Clinical Utility and Correlation with Dual-energy X-ray Absorptiometry. Iowa Orthop J. 2018;38:25\u0026ndash;31.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMens MA, De Geus A, Wellenberg RHH, et al. Preliminary evaluation of dual-energy CT to quantitatively assess bone marrow edema in patients with diabetic foot ulcers and suspected osteomyelitis. Eur Radiol. 2023;33:5645\u0026ndash;52.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eArmbrecht G, Felsenberg D, Ganswindt M, et al. Degenerative inter-vertebral disc disease osteochondrosis intervertebralis in Europe: prevalence, geographic variation and radiological correlates in men and women aged 50 and over. Rheumatology. 2017;56:1189\u0026ndash;99.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMoore RJ. The vertebral endplate: disc degeneration, disc regeneration. Eur Spine J. 2006;15:333\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM\u0026auml;\u0026auml;tt\u0026auml; JH, Kraatari M, Wolber L, et al. Vertebral endplate change as a feature of intervertebral disc degeneration: a heritability study. Eur Spine J. 2014;23:1856\u0026ndash;62.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAdams MA, Dolan P. Intervertebral disc degeneration: evidence for two distinct phenotypes. J Anat. 2012;221:497\u0026ndash;506.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Spondylodiscitis, diagnostics, spinal infections, Houndsfield Units","lastPublishedDoi":"10.21203/rs.3.rs-3959086/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3959086/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eMRI being the method of choice for radiological diagnosis of spondylodiscitis is still often delayed. The significance of native CT Scans as an alternative diagnostic tool for spondylodiscitis is poor according to the current data. Therefore, the aim of this study was to investigate, weather spondylodiscitis leads to a significant pattern of the density distribution from the affected vertebral bodies and discs measured by Hounsfield Units (HU) in native CT Scans.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eIn a retrospective study we analyzed data from 136 patients, who were treated for spondylodiscitis. Patients who provided MRI- and CT- scans of the spine were included. In axial CT planes HU from the affected intervertebral disc as well as from the affected vertebral bodies and from the unaffected adjacent intervertebral discs and vertebral bodies from the level above and below as reference were measured.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe average measured HU of the affected disc were 26.0% less than in the not affected adjacent discs (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The average measured HU of the affected vertebral bodies were 33.77% higher than in the not affected adjacent vertebral body\u0026rsquo;s (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001)). The localization of the spondylodiscitis and the degree of bony destruction according to Eysel-Peters classification had no influence on these findings.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eDecreased HU of the affected vertebral disc of approximate 25% and / or increased HU of the affected vertebral bodies of approximate 30% compared with adjacent vertebral discs and vertebral are indicative for spondylodiscitis even in early phase without destruction and independent of the localization.\u003c/p\u003e","manuscriptTitle":"Considering Hounsfield Units in native CT- scans for diagnosing spondylodiscitis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-04 18:46:06","doi":"10.21203/rs.3.rs-3959086/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-12-10T12:54:25+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-03T02:49:21+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"178218481818584605604227858746633320680","date":"2024-07-03T00:44:23+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-01T05:41:12+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-06-29T17:16:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"270909867656579615152136641823531507701","date":"2024-06-28T11:26:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"312946453145996983273566941885039410964","date":"2024-06-19T05:44:29+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-06-19T04:35:06+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-06-11T05:20:20+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2024-02-27T09:35:31+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-02-27T09:24:36+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Musculoskeletal Disorders","date":"2024-02-15T15:33:58+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f11a74ce-f1ad-4145-acf9-2471766ccaa4","owner":[],"postedDate":"March 4th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-09-08T16:01:47+00:00","versionOfRecord":{"articleIdentity":"rs-3959086","link":"https://doi.org/10.1186/s12891-025-09106-9","journal":{"identity":"bmc-musculoskeletal-disorders","isVorOnly":false,"title":"BMC Musculoskeletal Disorders"},"publishedOn":"2025-09-02 15:58:04","publishedOnDateReadable":"September 2nd, 2025"},"versionCreatedAt":"2024-03-04 18:46:06","video":"","vorDoi":"10.1186/s12891-025-09106-9","vorDoiUrl":"https://doi.org/10.1186/s12891-025-09106-9","workflowStages":[]},"version":"v1","identity":"rs-3959086","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3959086","identity":"rs-3959086","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}