Introduction

With the rise of urban violence, traffic accidents and crime, the number of charred, mutilated or highly decomposed bodies and skeletal remains that reach forensic medicine departments around the world has increased significantly^1,2.

The cause of death and the identity of the victim could be difficult to determine in such conditions, as when soft tissues are destroyed it is not possible to conduct a fingerprint analysis^1,3. This is why forensic anthropology and forensic dentistry play a major role in criminal investigations, where the relatives of the missing person will be interviewed and asked to provide medical and dental records, such as clinical records, radiographs, CT scans, cast models and pictures to aid in the human identification process^1,3-6.

Among the many methods available it is worth mentioning those comparing AM and PM radiographic imaging of the skull⁴, as the morphological variability of its many anatomical structures, like the frontal sinus, is very useful in forensics to determine a person’s identity⁷.

The specialized literature presents cases, although few, where human remains were identified by analyzing the frontal sinus^7,8, comparing images of the anatomical characteristics of the sinus and those of the osteosynthesis material⁹. The aim of this study is to present a forensic case report of a skeletonized body identified by analysis of frontal sinus morphology and the type and location of the material used to reduce trauma-induced fractures.

Case description

A skeletonized body was found in a forested region in the State of Goiás, Central-West region of Brazil. The forensic anthropological analysis (biological profiling) and cause of death determination were conducted after the examination at the scene had taken place and the remains were transported to the Institute of Forensic Medicine (IML) in the state capital.

During the external examination of the body we observed the pelvis and skull had male characteristics¹⁰, closed medial clavicular epiphysis¹¹, no osteophytes in the vertebral bodies¹², sagittal suture with few points of synostosis and third molars with full rhizogenesis, so we determined the age to be between 30 and 40. We estimated the height (between 1.67 m and 1.74 m) by measuring the length of the long bones of the upper and lower limbs and by using Trotter and Gleser’s¹³ 1952 table. There were three osteosynthesis metal plates on the skull, fixed with screws, which suggests the occurrence of AM trauma (characteristics and location shown in Table 1 and Fig. 1).

The cause of death was determined to be traumatic brain and face injury by means of a perforating, blunt instrument. There were transfixing wounds caused by firearms, with entry holes in the occipital and right jaw regions (Fig. 2).

In addition to expert examinations, police investigations revealed that the victim was probably a 29-year old man who had been kidnapped seven months earlier. The AM documentation submitted entailed a medical form and two posteroanterior (PA) skull radiographs (one presurgical and one immediately after surgery), taken seven years before his disappearance, which showed a fracture and an osteosynthesis plate in the right periorbital region. These also showed the morphology of the frontal sinus: expanded to both sides of the midline (Fig. 3).

We decided to conduct PM exams, a PA radiograph and a cranial cone-beam CT (Fig. 4). This was done at a radiological laboratory that has signed an agreement with the IML. InVesalius® software was used to review the PM CT. The cranial image was reconstructed, rotated and processed in the same position as the AM immediate postsurgical PA radiograph.

After that, we compared the AM immediate postsurgical PA radiograph to the PA radiograph and PM CT. We found morphological similarity of the frontal sinus in terms of its area of expansion, number and location of the septa and lobes (Table 2) and the osteosynthesis plate present in the lateral wall of the right orbit, anatomic location, type and fixing screws (number, design, length, arrangement and fixing angle), as shown in Fig. 5. This made it possible to positively identify the missing person.

Discussion

Radiograph images are widely used for identification purposes, especially when a lophoscopy analysis cannot be performed, and are very useful in cases of charred, decaying and skeletonized bodies^4,5,9,14.

This is further enhanced by the number of skull x-rays performed on a daily basis, as the population has increased access to dental care, to diagnose, plan and/or check different clinical treatments^5,15).

In addition, the skull is highly resistant to environmental conditions and thus has demonstrated great forensic potential. In fact, PA radiographs make it possible to study the anatomical features (dental or bone), pathological and/or therapeutic characteristics, as well as the type of a possible osteosynthesis material⁹.

However, we should remember that PA radiographs are not the best alternative for a detailed dental analysis, if compared to panoramic⁵ or intraoral¹⁾ radiographs. These should be used with caution to avoid misleading or inconsistent conclusions. In return, they become valuable in a morphologic, qualitative and quantitative assessment of the frontal sinus, bearing in mind that this expansive cavity is unique and does not change in adults^7-9,16,17.

In this case, the morphological similarity between AM and PM x-ray images of the frontal sinus, comparative procedure widely supported and described in the literature^(7-9,16.17), made the positive identification of the victim possible, paving the way for the criminal investigation to arrest and prosecute those involved in his death. The presence of the osteosynthesis plate on the lateral wall of the right orbit was an additional element for comparison, with results consistent with those of the frontal sinus⁹.

Finally, it should be mentioned that this method is faster and less expensive than a DNA test, showing how important it is to have a radiology service in the IMLs or, if this were not possible, to enter into agreements with public or private radiological laboratories. It is also necessary to have forensic dentists with the right expertise and training in imaging techniques, especially extraoral x-rays and CTs, usually used for criminal investigation purposes.

Conclusions

PA radiographs and skull CTs make it possible to analyze the morphology of the frontal sinus and the characteristics of a potential osteosynthesis material, facilitating the human identification process in complex cases of charred, decaying or skeletonized bodies.