This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thoracic and Lumbosacral Spine Injuries, Subject name: Orthopaedics
[{'content': 'In the lumbar spine, 90% of the disc herniations occur at which of the following level: \nSelect and explain. \nA. L1-L2, B. L2-L3, C. L3-L4, D. L4-L5', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. (d) L4-L5Ref: Maheshwari 5th ed. / 253* Most common site of spinal disc herniation: Lumbar region (95% in L4-L5 or L5-S1).* The second most common site is the cervical region (C5-C6, C6-C7).* Thoracic region accounts for only 0.15% to 4.0% of cases.* Herniations usually occur posterolaterally, where the annulus fibrosis is relatively thin and is not reinforced by the posterior or anterior longitudinal ligament.* In the cervical spinal cord, a symptomatic posterolateral herniation between two vertebrae will impinge on the nerve which exits the spinal canal between those two vertebrae on that side. For example, a right posterolateral herniation of the disc between vertebrae C5 and C6 will impinge on the right C6 spinal nerve.', 'role': 'assistant'}]