OBJECTIVES: This article reviews the prevalence of lumbarisation, sacralisation and lumbar ribs, and their morphological relevance by evaluating multi-slice computed tomography (MSCT) images. These segment variations can cause miscounting of vertebrae at the lumbar spinal level. METHODS: A retrospective radiographic analysis of 226 cases scanned by MSCT prior to forensic autopsy was undertaken. MSCT scans of the entire spine were obtained. Radiological data were evaluated on a three-dimensional image workstation. Vertebral levels were determined by counting downward from the first cervical vertebra, based on the assumption of seven cervical, 12 thoracic and five lumbar vertebrae. The prevalence of lumbarisation, sacralisation and lumbar ribs was assessed. RESULTS: Lumbar ribs were observed in 13 of the 226 cases (5.8 %). Lumbarisation and sacralisation were observed in 14 cases (6.2 %) and six cases (2.7 %), respectively. Lumbar ribs were present in 11 of the 14 cases with lumbarisation, and in two of the 206 cases with normal lumbar vertebral configuration. Lumbarisation had a statistically significant association with lumbar ribs (p < 0.01). CONCLUSIONS: There was a strong association between lumbar ribs and lumbarisation, with a resulting miscount rate for the lumbar spine of slightly less than 10 %. TEACHING POINTS: • Lumbarisation and sacralisation are observed 6.2 % and 2.7 %, respectively. • Thoracolumbar segment variations can cause a miscount rate for the lumbar spine of less than 10 %. • Lumbar rib is significantly associated to lumbarisation.