TY - BOOK

T1 - Advanced forensic analysis ofskull fracture

T2 - PhD Thesis

AU - Henningsen, Mikkel Jon

PY - 2023/6/14

Y1 - 2023/6/14

N2 - The overall aim of this PhD-project was to advance the detection, analysis, and presentation tolaypersons of skull fracture in the field of forensic pathology. The advancement of computed tomography,the increase in computational capability, and the rapid growth in 3D printing possibilitiesprovide tools that may propel forensic medicine from the autopsy- and microscopy investigationsof ancient times and into the 21st century. Studies I - IV focused on diagnosing blunt forceskull fracture with post-mortem computed tomography (PMCT), analysing skull fractures withfinite element analysis (FEA), and reporting the results to the court of law with the aid of 3D prints.Study I aimed to provide a summary effect size for the sensitivity and specificity of PMCT forskull fracture detection. Because individual studies on PMCT with varying sample sizes had reportedoutcomes ranging from 0.50 to 1.00, a meta-analysis was needed. Study I demonstrated thatPMCT is a near perfect diagnostic test in terms of sensitivity and specificity i.e., finding fracturein cases with an actual fracture and excluding fracture in cases with no actual fracture [1].However, the existing studies included cases with extensive fractures caused by explosions, gunshots,high-velocity blunt force traumas, etc. PMCT may be a better diagnostic tool in cases withsuch trauma mechanisms than in cases with less forceful blunt force head trauma. If data fromPMCT are to be used to compare with results of FEA, or if PMCT is to be used as a screening toolat medico-legal investigations, the diagnostic capabilities of PMCT for identifying small and subtlefractures must also be determined.Study II aimed to determine the diagnostic capabilities of PMCT for detection of individual fracturelines in the skull and present this as sensitivity and specificity. A retrospective study comparedautopsy with PMCT and generated more than 5,000 data points. Study II found that even thoughthe presence and absence of a fracture system can be reliably diagnosed or excluded, the individualfracture lines were difficult to diagnose, and inter-observer agreement was moderate [2].Study III aimed to assess the feasibility of using subject-specific finite element (FE) head modelsfor FEA of blunt force skull fracture in adults in forensic pathology routine cases. Study III foundthat FEA successfully predicted the occurrence of skull fracture in five of five cases, and correctlypredicted fracture pattern in three of five cases. FEA was sensitive to changes in kinematic assumptions.FEA was found feasible in cases with linear fractures, a single head impact, and welldescribed circumstances. Subject-specific FEA may aid forensic pathologists in analysing skullfracture and assessing the plausibility of proposed scenarios. The results should be used cautiouslythough.Study IV aimed to explore the effects of introducing 3D print as a demonstrative aid to forensicpathologists providing expert testimony. Study IV found that the professional norms of forensicpathologists are different to the norms of prosecutors, defence counsels, and judges. This differencecontributed to the court’s already existing problem of critically appraising e.g. statistical,medical, and psychological statements. 3D prints enabled a quick overview, provided a mentalximage of the fractures, and were perceived to be less emotionally confronting than autopsy photos.However, physical 3D prints posed logistical challenges in distribution, demonstration, and archiving.Virtual 3D models were perceived equally beneficial to 3D prints as the sense of touchwas of lesser importance than previous studies had speculated. Virtual 3D models were perceivedto cause less emotional impact than 3D prints and be easier to distribute, show, and store. Despitethe benefits of 3D demonstration, the court rarely needed the detailed information provided by 3Dprints, instead relying on the expert witness to assess proposed scenarios. 3D prints were thereforerarely necessary.In conclusion, this PhD-project demonstrated that while PMCT had a near perfect sensitivity andspecificity for skull fracture detection in a varied sample, the detection of individual fracture lineswas more difficult. PMCT must, for now, be supplemented by autopsy if all fracture lines are tobe visualised. PMCT data may be used for generation of subject-specific 3D models, which maybe used for FEA of skull fracture or 3D prints to demonstrate autopsy findings in court. Muchwork remains before FEA and 3D printing can be implemented in routine forensic pathology butthe studies in this project highlights some of the drawbacks and difficulties, thus paving the wayfor future research and implementation.

AB - The overall aim of this PhD-project was to advance the detection, analysis, and presentation tolaypersons of skull fracture in the field of forensic pathology. The advancement of computed tomography,the increase in computational capability, and the rapid growth in 3D printing possibilitiesprovide tools that may propel forensic medicine from the autopsy- and microscopy investigationsof ancient times and into the 21st century. Studies I - IV focused on diagnosing blunt forceskull fracture with post-mortem computed tomography (PMCT), analysing skull fractures withfinite element analysis (FEA), and reporting the results to the court of law with the aid of 3D prints.Study I aimed to provide a summary effect size for the sensitivity and specificity of PMCT forskull fracture detection. Because individual studies on PMCT with varying sample sizes had reportedoutcomes ranging from 0.50 to 1.00, a meta-analysis was needed. Study I demonstrated thatPMCT is a near perfect diagnostic test in terms of sensitivity and specificity i.e., finding fracturein cases with an actual fracture and excluding fracture in cases with no actual fracture [1].However, the existing studies included cases with extensive fractures caused by explosions, gunshots,high-velocity blunt force traumas, etc. PMCT may be a better diagnostic tool in cases withsuch trauma mechanisms than in cases with less forceful blunt force head trauma. If data fromPMCT are to be used to compare with results of FEA, or if PMCT is to be used as a screening toolat medico-legal investigations, the diagnostic capabilities of PMCT for identifying small and subtlefractures must also be determined.Study II aimed to determine the diagnostic capabilities of PMCT for detection of individual fracturelines in the skull and present this as sensitivity and specificity. A retrospective study comparedautopsy with PMCT and generated more than 5,000 data points. Study II found that even thoughthe presence and absence of a fracture system can be reliably diagnosed or excluded, the individualfracture lines were difficult to diagnose, and inter-observer agreement was moderate [2].Study III aimed to assess the feasibility of using subject-specific finite element (FE) head modelsfor FEA of blunt force skull fracture in adults in forensic pathology routine cases. Study III foundthat FEA successfully predicted the occurrence of skull fracture in five of five cases, and correctlypredicted fracture pattern in three of five cases. FEA was sensitive to changes in kinematic assumptions.FEA was found feasible in cases with linear fractures, a single head impact, and welldescribed circumstances. Subject-specific FEA may aid forensic pathologists in analysing skullfracture and assessing the plausibility of proposed scenarios. The results should be used cautiouslythough.Study IV aimed to explore the effects of introducing 3D print as a demonstrative aid to forensicpathologists providing expert testimony. Study IV found that the professional norms of forensicpathologists are different to the norms of prosecutors, defence counsels, and judges. This differencecontributed to the court’s already existing problem of critically appraising e.g. statistical,medical, and psychological statements. 3D prints enabled a quick overview, provided a mentalximage of the fractures, and were perceived to be less emotionally confronting than autopsy photos.However, physical 3D prints posed logistical challenges in distribution, demonstration, and archiving.Virtual 3D models were perceived equally beneficial to 3D prints as the sense of touchwas of lesser importance than previous studies had speculated. Virtual 3D models were perceivedto cause less emotional impact than 3D prints and be easier to distribute, show, and store. Despitethe benefits of 3D demonstration, the court rarely needed the detailed information provided by 3Dprints, instead relying on the expert witness to assess proposed scenarios. 3D prints were thereforerarely necessary.In conclusion, this PhD-project demonstrated that while PMCT had a near perfect sensitivity andspecificity for skull fracture detection in a varied sample, the detection of individual fracture lineswas more difficult. PMCT must, for now, be supplemented by autopsy if all fracture lines are tobe visualised. PMCT data may be used for generation of subject-specific 3D models, which maybe used for FEA of skull fracture or 3D prints to demonstrate autopsy findings in court. Muchwork remains before FEA and 3D printing can be implemented in routine forensic pathology butthe studies in this project highlights some of the drawbacks and difficulties, thus paving the wayfor future research and implementation.

M3 - Ph.D. thesis

SN - 978-94336-92-5

BT - Advanced forensic analysis ofskull fracture

PB - University of Copenhagen

ER -