"Man can see only what he knows." Goethe Ossification of the Posterior Longitudinal Ligament (OPLL) has long been a challenge to orthopedic spinal surgeons in Japan, and their struggle to meet that challenge has marked a turning point in the history of spinal surgery. Investigation of the etiology and treatment of the condition has taught surgeons to see diseases of the spine and their surgical treatment in a new perspective. It was truly a surprise to learn that the posterior longitudinal ligament could become a thick, bony plate in the cervical spine and impinge on the spinal cord, leading to paralysis. Even more amazing, however, is that innumerable roent genological findings of such thick, bony lesions could be overlooked for decades before OPLL became well recognized by physicians in Japan. Progress in diagnostic imaging technology, first in computed tomography (CT) and then in magnetic resonance imaging (MRI), has helped in diagnosis and evaluation of the disease and in deciding therapeutic modalities. There is no better tool than CT and CT myelography for demonstrating the real threat of OPLL to the cervical spinal cord. MRI, however, provides more information on widespread ossified lesions from the cervical to lumbar regions, and on the intramedullary changes caused by chronic compression. It is not a great exaggeration to say that OPLL is one of the leading reasons for the enthusiastic expansion in the market for the newest diagnostic imaging tools in Japan.
