‘The Stegosaurus Appearance’ on ultrasound to assist in identifying the correct spinal level for primary lumbar spinal surgery

Lumbar spinal surgery relies on palpation of anatomical landmarks and X-ray imaging confirmation to identify the correct spinal level, therefore exposing patients and staff to radiation, and increasing intraoperative time and cost. Ultrasound (US) assistance is being used to visualise spinal anatomy by many specialities, such as neurology and anaesthetics, and can be used intraoperatively in selected spinal surgery cases. However, its potential use to check spinal levels prior to surgery remains understudied. This prospective, pilot study screened all patients requiring a primary elective or emergency lumbar discectomy, under the supervision of a single consultant neurosurgeon, over an 8-month period at a single neurosurgical unit. US assistance was used to identify and mark the proposed spinal level prior to skin incision. The resemblance of the parasagittal lumbar US images to the back of the dinosaur Stegosaurus aided users in identifying the relevant anatomical structures necessary to mark the desired spinal level, (e.g., lumbar laminae, intervertebral spaces, sacrum). This inspired our description of the US images of the lumbar spine as 'The Stegosaurus Appearance'. The spinal level marked by US was then confirmed in the standard fashion using intraoperative X-ray imaging. In 100% of cases (12/12), the desired spinal level was correctly identified using US, confirmed by the subsequent intraoperative X-ray images. US assistance appears to be a safe, quick, and accurate tool for identifying the correct lumbar spinal level prior to skin incision, and could therefore represent a useful adjunct to supplement level checking in lumbar spinal surgery.