The prevalence of 11 ribs and its potential implications in spine surgery

Wrong level surgery is a preventable event in spine surgery. The thoracic spine given its length and anatomical landmarks remains the most challenging spine section for accurate localization during surgery. Traditionally, counting the ribs with intraoperative fluoroscopy is the preferred method. The incidence of 11 ribs instead of the conventional 12 ribs is not examined in current scientific literature, even though the incidence of 11 ribs may have a substantial impact on spinal procedures and the outcomes. This is especially relevant if patients have a potential surgical pathology of their thoracic spine. In this case series we sought to investigate the prevalence of 11 ribs in a trauma population.

A retrospective review was conducted of patients presenting with thoracolumbar fractures at our Level I Trauma Center between 2017 and 2018. CT scans were obtained and analyzed by counting the number of ribs.

Out of 234 patients who were consulted for thoraco-lumbar fractures by spine specialists, 8 patients had 11 ribs which results in a prevalence of 3.4 % in this population. Within these 8 patients, 5 were male (62.5 %).

Spine surgeons should consider the possibility of numeric variation of ribs when evaluating thoracolumbar spine imaging. In a trauma population with spine fractures, the prevalence of 11 ribs is 3.4 %. Given the not insignificant prevalence of this variant in potentially surgical spine patients, the spine surgeon should remain vigilant of this anatomical variant.