Ossified ligamentum flavum (OLF) is a condition of heterotopic lamellar bone formation within the yellow ligament. Some patients with OLF can be asymptomatic. However, asymptomatic OLF may not be obvious on preoperative MRI and could increase the risk of iatrogenic injury during treatments for unrelated spinal conditions. This report describes a case of spinal cord injury caused by the indirect transmission of force from an osteotome to an asymptomatic OLF during the resection of a thoracic inferior articular process (IAP). To prevent this outcome, we urge careful review of CT imaging in the preoperative setting and advocate the use of a high-speed drill instead of an osteotome during bone removal in the setting of an adjacent area of OLF.