Tim Kobes

Dr. Tim Kobes

orcid

Research Focus & Metrics

Academic Career Length

5Years (2022-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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Verified
Journal Article
Open access
PDF file
TKTim Kobes
Tim Kobes
ASArthur Sweet
Arthur Sweet
SVSophie Verstegen
Sophie Verstegen
MHMarijn Houwert
Marijn Houwert
WVWouter Veldhuis
Wouter Veldhuis
MBMark van Baal
Mark van Baal
Opportunistic screening for bone mineral density (BMD) of the first lumbar vertebra (L1) using computed tomography (CT) is increasingly used to identify patients at risk for osteoporosis. An extensive study in the United States has reported sex-specific normative values of CT-based BMD across all ages. The current study aims to validate North American reference values of CT-based bone mineral density in a Dutch population of level-1 trauma patients. All trauma patients aged 16 or older, admitted to our level-1 trauma center during 2017, who underwent a CT scan of the chest or abdomen at 120 kVp within 7 days of hospital admission, were retrospectively included. BMD measurements in Hounsfield Units (HU) were performed manually in L1 or an adjacent vertebra. Student’s t-tests were performed to compare the Dutch mean BMD value per age group to the North American reference values. Linear regression analysis and Pearson’s correlation coefficient (ρ) calculations were performed to assess the correlation between BMD and age. In total, 624 patients were included (68.4% men, aged 16–95). Mean BMD decreased linearly with 2.4 HU per year of age (ρ = −0.77). Sex-specific analysis showed that BMD of premenopausal women was higher than BMD of men at these ages. Dutch mean BMD values in the age groups over 35 years were significantly lower than the North American reference values. Our findings indicate that using North American BMD thresholds in Dutch clinical practice would result in overdiagnosis of osteoporosis and osteopenia. Dutch guidelines may benefit from population-specific thresholds.

18 June 2025 in Journal of Bone and Joint Surgery
Verified
Journal Article
Closed access
CLCarol A. Lin
Carol A. Lin
TKTim Kobes
Tim Kobes
EKEric Kholodovsky
Eric Kholodovsky
GHGiselle Hernandez
Giselle Hernandez
NONathan N. O’hAra
Nathan N. O’hAra
TIthe PREP-IT Investigators
the PREP-IT Investigators
Background: The ideal antibiotic prophylaxis for open fractures is unknown. We evaluated outcomes following different antibiotic prophylaxis regimens for open fractures. Methods: This is a secondary analysis of data from PREP-IT. Prophylactic antibiotics were defined as any intravenous antibiotic given on the day of admission. The outcomes were surgical site infection (SSI) within 90 days and reoperation within 1 year. Logistic regression and an instrumental variable analysis that leveraged site-level variation accounted for confounding. Subgroup variation was evaluated by stratifying by Gustilo-Anderson classification (Types I and II versus III). Results: Of the 3,331 included participants, the mean age was 45 ± 18 years, 63% were male, 73% were White, 21% were Black, 2% were Asian, and 10% were Hispanic. Cefazolin monotherapy (58% of patients), ceftriaxone monotherapy (10%), and cefazolin plus gentamicin (6%) were the most common regimens. In the instrumental variable analysis, the odds of infection did not significantly differ with ceftriaxone use (odds ratio [OR], 1.24; 95% confidence interval [CI], 0.70 to 2.20; p = 0.45) or cefazolin plus gentamicin use (OR, 0.25; 95% CI, 0.03 to 2.04; p = 0.20) compared with cefazolin monotherapy. There were no significant differences between the regimens with respect to infection when stratified by Gustilo-Anderson type. However, we did observe a nearly 3-fold increase in the odds of infection with ceftriaxone use compared with cefazolin monotherapy (OR, 2.73; 95% CI, 0.96 to 7.79; p = 0.06) in Type-I and II fractures, and a 75% decrease in the odds of infection with cefazolin plus gentamicin use (OR, 0.25; 95% CI, 0.03 to 2.02; p = 0.19) compared with cefazolin monotherapy in Type-III fractures. Conclusions: Among patients with open fractures, antibiotic prophylaxis with ceftriaxone monotherapy did not provide significant benefits compared with cefazolin monotherapy in preventing infection in Type-I and II fractures. The findings suggest that cefazolin plus gentamicin might reduce the odds of infection in Type-III fractures compared with cefazolin monotherapy, but this difference was not statistically significant. Level of Evidence: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

2 March 2023 in European Journal of Trauma and Emergency Surgery
Verified
Journal Article
Open access
PDF file
ASArthur A. R. Sweet
Arthur A. R. Sweet
TKTim Kobes
Tim Kobes
RHRoderick M. Houwert
Roderick M. Houwert
RGRolf H. H. Groenwold
Rolf H. H. Groenwold
PMPim Moeskops
Pim Moeskops
MBMark C. P. M. van Baal
Mark C. P. M. van Baal
Purpose: The present study aims to assess whether CT-derived muscle mass, muscle density, and visceral fat mass are associated with in-hospital complications and clinical outcome in level-1 trauma patients. Methods: A retrospective cohort study was conducted on adult patients admitted to the University Medical Center Utrecht following a trauma between January 1 and December 31, 2017. Trauma patients aged 16 years or older without severe neurological injuries, who underwent a CT that included the abdomen within 7 days of admission, were included. An artificial intelligence (AI) algorithm was used to retrieve muscle areas to calculate the psoas muscle index and to retrieve psoas muscle radiation attenuation and visceral fat (VF) area from axial CT images. Multivariable logistic and linear regression analyses were performed to assess associations between body composition parameters and outcomes. Results: A total of 404 patients were included for analysis. The median age was 49 years (interquartile range [IQR] 30–64), and 66.6% were male. Severe comorbidities (ASA 3–4) were seen in 10.9%, and the median ISS was 9 (IQR 5–14). Psoas muscle index was not independently associated with complications, but it was associated with ICU admission (odds ratio [OR] 0.79, 95% confidence interval [CI] 0.65–0.95), and an unfavorable Glasgow Outcome Scale (GOS) score at discharge (OR 0.62, 95% CI 0.45–0.85). Psoas muscle radiation attenuation was independently associated with the development of any complication (OR 0.60, 95% CI 0.42–0.85), pneumonia (OR 0.63, 95% CI 0.41–0.96), and delirium (OR 0.49, 95% CI 0.28–0.87). VF was associated with developing a delirium (OR 1.95, 95% CI 1.12–3.41). Conclusion: In level-1 trauma patients without severe neurological injuries, automatically derived body composition parameters are able to independently predict an increased risk of specific complications and other poor outcomes.

28 March 2024 in European Journal of Trauma and Emergency Surgery
Verified
Journal Article
Open access
PDF file
TKTim Kobes
Tim Kobes
DSDiederik PJ Smeeing
Diederik PJ Smeeing
FHFalco Hietbrink
Falco Hietbrink
KBKim E. M. Benders
Kim E. M. Benders
RHR. Marijn Houwert
R. Marijn Houwert
MBMark P. C. M. van Baal
Mark P. C. M. van Baal
Purpose: What are reported definitions of HAP in trauma patient research? Methods: A systematic review was performed using the PubMed/MEDLINE database. We included all English, Dutch, and German original research papers in adult trauma patients reporting diagnostic criteria for hospital-acquired pneumonia diagnosis. The risk of bias was assessed using the MINORS criteria. Results: Forty-six out of 5749 non-duplicate studies were included. Forty-seven unique criteria were reported and divided into five categories: clinical, laboratory, microbiological, radiologic, and miscellaneous. Eighteen studies used 33 unique guideline criteria; 28 studies used 36 unique non-guideline criteria. Conclusion: Clinical criteria for diagnosing HAP—both guideline and non-guideline—are widespread with no clear consensus, leading to restrictions in adequately comparing the available literature on HAP in trauma patients. Studies should at least report how a diagnosis was made, but preferably, they would use pre-defined guideline criteria for pneumonia diagnosis in a research setting. Ideally, one internationally accepted set of criteria is used to diagnose hospital-acquired pneumonia. Level of evidence: Level III.

17 January 2023 in Archives of orthopaedic and trauma surgery
Verified
Journal Article
Open access
PDF file
TKTim Kobes
Tim Kobes
ATA. M. Terpstra
A. M. Terpstra
FIFrank IJpma
Frank IJpma
LLLuke L.P.H. LEENEN
Luke L.P.H. LEENEN
RHR. M. Houwert
R. M. Houwert
MBM. C. P. M. van Baal
M. C. P. M. van Baal
Introduction: Nosocomial pneumonia has poor prognosis in hospitalized trauma patients. Croce et al. published a model to predict post-traumatic ventilator-associated pneumonia, which achieved high discrimination and reasonable sensitivity. We aimed to externally validate Croce’s model to predict nosocomial pneumonia in patients admitted to a Dutch level-1 trauma center. Materials and methods: This retrospective study included all trauma patients (≥ 16y) admitted for > 24 h to our level-1 trauma center in 2017. Exclusion criteria were pneumonia or antibiotic treatment upon hospital admission, treatment elsewhere > 24 h, or death < 48 h. Croce’s model used eight clinical variables—on trauma severity and treatment, available in the emergency department—to predict nosocomial pneumonia risk. The model’s predictive performance was assessed through discrimination and calibration before and after re-estimating the model’s coefficients. In sensitivity analysis, the model was updated using Ridge regression. Results: 809 Patients were included (median age 51y, 67% male, 97% blunt trauma), of whom 86 (11%) developed nosocomial pneumonia. Pneumonia patients were older, more severely injured, and underwent more emergent interventions. Croce’s model showed good discrimination (AUC 0.83, 95% CI 0.79–0.87), yet predicted probabilities were too low (mean predicted risk 6.4%), and calibration was suboptimal (calibration slope 0.63). After full model recalibration, discrimination (AUC 0.84, 95% CI 0.80–0.88) and calibration improved. Adding age to the model increased the AUC to 0.87 (95% CI 0.84–0.91). Prediction parameters were similar after the models were updated using Ridge regression. Conclusion: The externally validated and intercept-recalibrated models show good discrimination and have the potential to predict nosocomial pneumonia. At this time, clinicians could apply these models to identify high-risk patients, increase patient monitoring, and initiate preventative measures. Recalibration of Croce’s model improved the predictive performance (discrimination and calibration). The recalibrated model provides a further basis for nosocomial pneumonia prediction in level-1 trauma patients. Several models are accessible via an online tool. Level of evidence: Level III, Prognostic/Epidemiological Study.

27 November 2022 in European Journal of Trauma and Emergency Surgery
Verified
Journal Article
Open access
PDF file
TKTim Kobes
Tim Kobes
ASArthur A. R. Sweet
Arthur A. R. Sweet
IKIjsbrand T. Klip
Ijsbrand T. Klip
RHRoderick M. Houwert
Roderick M. Houwert
WVWouter Veldhuis
Wouter Veldhuis
MBMark C. P. M. van Baal
Mark C. P. M. van Baal
Background: In-hospital complications after trauma may result in prolonged stays, higher costs, and adverse functional outcomes. Among reported risk factors for complications are pre-existing cardiopulmonary comorbidities. Objective and quick evaluation of cardiovascular risk would be beneficial for risk assessment in trauma patients. Studies in non-trauma patients suggested an independent association between cardiovascular abnormalities visible on routine computed tomography (CT) imaging and outcomes. However, whether this applies to trauma patients is unknown. Purpose: To assess the association between cardiopulmonary abnormalities visible on routine CT images and the development of in-hospital complications in patients in a level-1 trauma center. Methods: All trauma patients aged 16 years or older with CT imaging of the abdomen, thorax, or spine and admitted to the UMC Utrecht in 2017 were included. Patients with an active infection upon admission or severe neurological trauma were excluded. Routine trauma CT images were analyzed for visible abnormalities: pulmonary emphysema, coronary artery calcifications, and abdominal aorta calcification severity. Drug-treated complications were scored. The discharge condition was measured on the Glasgow Outcome Scale. Results: In total, 433 patients (median age 50 years, 67% male, 89% ASA 1–2) were analyzed. Median Injury Severity Score and Glasgow Coma Scale score were 9 and 15, respectively. Seventy-six patients suffered from at least one complication, mostly pneumonia (n = 39, 9%) or delirium (n = 19, 4%). Left main coronary artery calcification was independently associated with the development of any complication (OR 3.9, 95% CI 1.7–8.9). An increasing number of calcified coronary arteries showed a trend toward an association with complications (p = 0.07) and was significantly associated with an adverse discharge condition (p = 0.02). Pulmonary emphysema and aortic calcifications were not associated with complications. Conclusion: Coronary artery calcification, visible on routine CT imaging, is independently associated with in-hospital complications and an adverse discharge condition in level-1 trauma patients. The findings of this study may help to identify trauma patients quickly and objectively at risk for complications in an early stage without performing additional diagnostics or interventions.