Variations in the number of vertebrae among Iranian patients with adolescent idiopathic scoliosis

Correct-level surgery is one of the most important concerns in the treatment of patients with adolescent idiopathic scoliosis (AIS). Variations in vertebral number can potentially result in wrong-level surgery. It is possible that the incidence and type of these variations be affected by different factors such as ethnicity. In the current retrospective study, the prevalence of these variations in Iranian AIS patients was investigated.  

Between 2012 to 2017, spinal fusion was performed for the treatment of AIS in 125 patients. The thoracic and lumbar vertebrae were enumerated on posteroanterior radiographs. The first thoracic vertebra was the one attached to the first pair of ribs. Enumeration was continued in a caudal direction. The lumbar level initiated just below the last vertebra with a pair of associated ribs.

Abnormal vertebral enumeration was found in 18 patients (14.4%). The prevalence of abnormal lumbar enumeration was higher than thoracic vertebrae (10.4% versus 4%). Eleven thoracic vertebrae were found in 5 patients (4%). Four lumbar vertebrae were found in eleven patients (8.8%). There were two patients with six lumbar vertebrae (1.6%). There was no patient with abnormal enumeration of both thoracic and lumbar vertebrae.

The current study showed a relatively high rate of atypical number of thoracic and lumbar vertebrae in Iranian AIS patients. It is necessary to enumerate the vertebrae on the basis of an organized protocol preoperatively to prevent wrong-level surgery in AIS patients.