Morphometry of the thoracic pedicle and the pedicle-rib unit: A review of literature

Background : The pedicle is the most commonly used site in spinal fixation. The size of the pedicle screw utilized is determined by the dimensions of the pedicle. The purpose of this review is to summarize the available English literature on thoracic pedicle morphometry. Materials and methods : PubMed search with the mesh term “thoracic pedicle morphometry measurements” and “pedicle-rib unit morphometry measurements” found 25 relevant articles. Results : The transverse width of the thoracic pedicle is narrowest at the mid-thoracic region. The chord length increases with caudal advancement, and is longest in the lower thoracic spine. The transverse angle of the thoracic pedicle is neutral or divergent at the lower thoracic spine, while it is most convergent in the upper thoracic spine. Conclusions : Linear thoracic pedicle dimensions are influenced by age, gender, height, weight and spinal level. Angular dimensions are influenced by spinal level only. Pedicle screw size choice and application is therefore guided by these factors. Pre-operative CT scanning of the thoracic spine is highly recommended in surgical planning. Key words : Thoracic vertebra pedicle, Pedicle-rib unit, Morphometry