Medullabeteiligung bei einer Schraubenosteosynthese einer Densfraktur Typ II nach Anderson und D’Alonzo – eine forensisch-funktionelle Frakturanalyse

In the first part the clinical picture and post-mortem examination of a fatal direct injury to the medulla during a ventral lag screw osteosynthesis due to a type II dens fracture are presented. Apparently, there was a break in the osseous abutment for the screw. The preparative demonstration resulted in an intraoperative partial resection of the corpus of the axis, including the primary abutment with a deep relocation of the screw into the corpus of the dens. Clinical details about this are lacking. Therefore, the task was to look out for ways of an indirect assessment of the bone quality of the abutment in order to realize a forensic injury reconstruction. For this a biomechanical approach was chosen with a detailed depiction of the osseous density distribution in the axis and the maximum tension under high tensile stress, subsection 2. Independent from the age-related osteoporosis, the extent of microfractures in the spongiosa proved to be the essential criterion for the assessment of the bone quality of the abutment. In the specific case of a 72-year-old female, the introduction of a rotatory force due to a domestic fall led to an asymmetrical fracture of the dens with avulsion of a broad spongiosa sleeve. Due to the extensive microfractures connected with this, the osseous abutment for a lag screw osteosynthesis had to be viewed as posttraumatically unstable. This means a contraindication for the surgical treatment of the dens fracture.