A typical case was recently reported: early misdiagnosis and delayed diagnosis in a local hospital when a spinal fracture occurred in a patient with DISH. Further information about the disease is necessary. Diffuse idiopathic skeletal hyperostosis (DISH) is a common disease that increases progressively with age. There is a paucity of epidemiological data in China, but overseas data show a prevalence of 3.8% in men and 2.6% in women over the age of 40, and a prevalence of approximately 10.0% in people over the age of 65. The majority of cervical DISH does not cause symptoms, but a minority of cervical DISH can produce a range of specific clinical symptoms that have attracted the attention of scholars. Clinically, diffuse idiopathic hypertrophy is not uncommon, and the lack of knowledge of this disease often leads to neglect of further comprehensive examination, while certain local imaging manifestations of this disease are simply classified as degenerative diseases of the cervical and thoracolumbar spine, and diagnosed and treated. In fact, this disease is a specific type of disease with systemic lesions and the spine as the central manifestation of heterotopic ossification of the anterolateral aspects of multiple consecutive segments of the vertebral body, which is often clinically confused with ankylosing spondylitis and degenerative osteoarthrosis. 1, the evolution of the name of DISH DISH has had many names. In 1971, Forestier pointed out that the main features of DISH were ossification of the anterior and right lateral ligaments of the thoracolumbar and cervicothoracic segments of the spine, hypertrophy of the anterior cortical bone of the vertebral body, and cloud-like shadows in the anterior part of the intervertebral space, naming it senile ankylosing hyperostosis of the spine. In 1976, Resnick called it diffuse idiopathic hyperostosis of the spine (DISH). This nomenclature is a more comprehensive description of the characteristics of the disease and is well recognized by scholars. 2, etiology and pathological changes: the etiology of DISH is unknown, but some studies have suggested that it is related to endocrine disorders, hyperglycemia and obesity. In this paper, 3 of 25 patients had a history of diabetes. The main pathological changes of the disease are limited or extensive calcification or ossification of the anterior longitudinal ligament, paravertebral connective tissue and fibrous ring of the spine, degeneration of the fibrous ring with vascular hyperplasia, cellular infiltration of chronic inflammation and formation of new bone in the periosteum in front of the vertebral body. ossification of the posterior border of the vertebral body in DISH can cause neurological complications, and the degree of ossification is proportional to the clinical symptoms and the degree of spinal cord compression. Osteomalacia can occur throughout the skeleton, but is most common in the spine, with the cervical spine being the most prevalent. 3, clinical manifestations of DISH: (1) Spinal stiffness is the most common clinical symptom, characterized by a bimodal phase, i.e., light during the day and heavy in the morning and evening, which can be triggered by cold and humid climate. (2) Spinal pain mostly involves the thoracic spine and presents as back pain, which is relatively mild and rarely radiates. Some early X-rays do not show typical spinal DISH changes, but there may be clear ossification of the bones and ligaments of the peripheral bones. (3) Peripheral arthritis and ossification manifest as pain in the heel, knee, elbow, and shoulder, aggravated by activity or prolonged rest, and X-rays showing bone formation or ossification in the affected area. (4) Neurological abnormalities are caused by the formation of superfluous bones and ossification of the posterior longitudinal ligament and ligamentum flavum, which compress the spinal cord and/or nerve roots, and the common symptoms are sensory and motor abnormalities. (5) Difficulty in swallowing, sore throat and hoarseness are caused by direct or indirect compression of the esophagus or laryngeal nerve by the cervical vertebral redundancy, which usually improves when the head is lowered and worsens when the head is raised. Physical examination: (1) pressure pain in the spinal bones of the thoracic back, mostly in the thoracolumbar spine, followed by pressure pain in the cervical spine, heel and other affected areas, and sometimes hard masses in the soft tissues and bone superfluities can be palpated at the site of pressure pain. (2) Restriction of movement of the spine and peripheral bones and joints can be found, including limitation of extension and flexion of the spine, reduction of the physiological anterior convexity of the lumbar spine, and reduction of the range of motion of the cervical spine in most patients with dysphagia. Restriction of peripheral bone movement is also common, but can be improved with activity. 3.3 Laboratory tests About 40% of patients with DISH have latent or clinical diabetes mellitus, and some have elevated blood vitamin A levels, while other tests such as blood sedimentation, routine blood count and biochemistry are mostly within the normal range. In order to distinguish DISH from other diseases with similar manifestations, Resnick chose spinal X-ray features as the diagnostic criteria for DISH: (1) ossification of the anterolateral margins of at least four consecutive vertebrae with or without vertebral body (2) the disc height in the affected area remains relatively intact and lacks radiographic manifestations of degenerative disc changes, including vacuum phenomenon and sclerosis of the vertebral body margins; (3) there is no bony ankylosis of the small intervertebral joints and no erosion, sclerosis or fusion of the sacroiliac joints. This diagnostic criterion is highly specific, but is not conducive to the diagnosis of mild and early DISH because it ignores lesions of the peripheral bone. the revised diagnostic criteria of Utsinger are: (1) continuous anterolateral ossification of at least 4 adjacent vertebral bodies, mainly in the thoracic region. The ossification zone initially appears corrugated and later develops into a broad, irregular strut-like ossification zone; (2) at least two adjacent vertebrae with anterolateral continuous ossification; (3) symmetrical peripheral osteophytes involving the posterior border of the heel bone, the superior patella, or the hawk’s beak, with an intact bone cortex at the edge of the new bone spur. One point must be emphasized: the sacroiliac joint was not involved in all cases. The patient’s vertebral space was basically normal and there was no ankylosis of the small joints. 4.2 Major differential diagnosis (1) Ankylosing spondylitis: Ankylosing spondylitis is most often seen in young men, with lesions starting from the sacroiliac joints on both sides and spreading upward, gradually invading the lumbar and thoracic vertebrae. First, the bone is sparse and the small joints are blurred or even disappear, and then the intervertebral discs together with the paravertebral ligaments are extensively ossified, but the ossification is thin and flat. In contrast, diffuse idiopathic osteophytes are more common in the elderly, with thick and dense ossification of the ligaments and wavy outer edges, mostly with ossification of the anterior longitudinal ligaments. The small joints and sacroiliac joints are normal. (2) Degenerative osteoarthropathy of the spine: In degenerative osteoarthropathy of the spine, the vertebral body edges are hyperplastic and sclerotic and may form bony bridges, with narrowing of the vertebral space, sparse bone, and sometimes visible Hsu’s nodes, without extensive calcification of the anterior longitudinal ligament. It is noteworthy that both can occur at the same time. (3) Fluorosis: In addition to osteophytes and ligament ossification, fluorosis also has density changes, i.e., increased bone density, bone softening, bone sparing, and interosseous membrane calcification is also one of the characteristics of the disease (mostly seen in the radius and tibiofibula), which is not difficult to differentiate when combined with clinical. 5, radiological examination and characteristic manifestations X-ray examination should be preferred for the diagnosis of diffuse idiopathic osteophyte hypertrophy. CT examination can more clearly show the hyperplasia of the posterior border of the vertebral body and ossification of the posterior longitudinal ligament, which can provide further help for the diagnosis and differential diagnosis of this disease. 5.1 Spinal X-ray manifestations Usually, DISH of the spine can be divided into two types: type I lesions, which are mainly characterized by wavy ossification of the anterior and paravertebral ligaments, because the intervertebral discs of this type are more normal and are not accompanied by anterior protrusion of the discs, so the ossification of the anterior longitudinal ligaments is usually continuous; type II lesions, in addition to ossification of the ligaments, are also combined with degeneration of the intervertebral disc fibrous ring and anterolateral protrusion of the discs, and the ossification of the anterior vertebral ligaments at the level of the intervertebral space In the anterior ossification zone at the intervertebral space level, the intervertebral disc protrudes and causes ossification to form a cut, resulting in an interrupted ossification of the anterior longitudinal ligament. The thoracic spine is the typical affected area of DISH, and abnormal ossification is common in the lower thoracic spine, most commonly in T7 to 11. The upper thoracic spine is rare, but continuous ossification from T1 to 12 can occasionally be seen. Characteristic radiographic manifestations: (1) continuous ossification of the anterolateral aspect of the vertebral body. The ossification is lamellar, crossing the intervertebral space, and is more extensive, but only slightly limited to 3-4 vertebrae. The thickness of the ossification is 1-10 mm, with a maximum thickness of 20 mm. When the ossification is extensive, dense shield-like changes are formed on the anterolateral side of the spine. Late ossification is more concave and uneven, especially at the disc level where no ossification or mild ossification is more evident. However, in some vertebrae, the thickness of the anterolateral ossification is only 1 to 3 mm, and the disc bulge and sharp-edged bones may be smooth until they appear. (2) Bone redundancy is formed at the upper and lower margins of the vertebral body, but the intervertebral disc maintains its relative height. The vertebral body is often claw-shaped or hawk-like, and often fuses with the anterior bone of the vertebral body, often with the disc intact, while the upper and lower margins of the vertebral body are most severely ossified. (3) The horizontal bone deposition of the intervertebral disc is located more anteriorly. Hypodense shadows of varying morphology are seen within the ossified mass, which are caused by disc bulging or herniation. (4) A linear or semi-annular translucent zone appears between the ossification of the ligament and the anterior edge of the vertebral body. Although the translucent zone does not occur in every vertebral body, it is a characteristic radiographic manifestation of DISH. This translucent zone often terminates abruptly at the superior and inferior edges of the vertebral body. In late stages, this translucent gap may disappear with the progression of ossification. (5) Asymmetry of ossification on both sides of the vertebral body. Although both sides are often involved, the right side of the thoracic spine (including the upper lumbar spine) is severely ossified, while bone deposits and osteophytes on the left side are rare, which is thought to be the result of the influence of aortic pulsation. Cervical DISH is most commonly seen in the C4 to 7 vertebrae, opposite C1 and C2. Initially, ossification occurs along the anterior surface of the vertebral body, with osteophytes appearing at the anterior edge, particularly at the anterior inferior edge of the vertebral body, extending down and over the intervertebral disc. As the lesion progresses, several consecutive vertebral bodies are seen to be involved. The ossification is smooth, uneven, and irregular, up to 6-8 mm thick, and there is often a low-density defect formed by disc bulging within the intervertebral space level ossification, but a translucent zone between the ossification and the vertebral body is less common. Lumbar vertebrae are more common from L1 to 3, symmetrical on both sides, with the prevertebral body initially showing bone hypertrophy and gradually cloudy hyperdensity shadows and claw-like bony flaps at the vertebral body edges, especially more pronounced at the prevertebral body. The ossification extends across the intervertebral space, and hypodense shadows are seen within the bone mass anterior to the intervertebral disc. Occasionally, a translucent zone between the new bone and the vertebral body is seen, but ossification is less common in several consecutive vertebral bodies and more common in claw-like osteophytes at the upper and lower margins of the vertebral body. 5.2 External spinal X-ray manifestations The early abnormal peripheral bone changes are foci of ossification within the tendon, which may form a zone of ossification as the ossification expands, either attached to the tendon attachment bone or with a small interval. It usually involves the tibial stem, heel, patella and ulnar hawk bones bilaterally. Beard-like bone deposits are seen in the ligamentous attachments of the iliac crest of the pelvis, sciatic tuberosity, and femoral rotor. Bone redundancy was seen around the joint below the sacroiliac joint; next to the acetabulum, a bone bridge was formed at the superior pubic rim. In addition, ossification of ligaments is common in the pelvis, with a particular preference for the iliolumbar and sacral nodal ligaments. It is not a characteristic manifestation of DISH. Bone spurs on the lower posterior surface of the heel and hyperplasia of the Achilles and metatarsal tendon membranes. Specific osteophytes occur on the dorsal aspect of the talus, tarsus, dorsomedial aspect of the navicular bone, posterior aspect of the base of the dice bone and the base of the 5th metatarsal, the latter may show calcification of the metatarsal tendon membrane or a variation similar to that of the seed bone. 5.3 Associated bone alterations Osteoporosis is mainly mild in the vertebrae, but the degree of osteoporosis is not consistent with age. However, some scholars disagree with this view; bone stiffness is commonly seen in the thoracic region and less frequently in the cervical and lumbar spine. The intervertebral small joint space is narrowed and sclerotic, but no ankylosis is present. There may be bony redundancies or even bridges around the sacroiliac joints, but usually no fusion occurs. Because the intervertebral joints do not straighten, spinal motion is limited, but some mobility is maintained. DISH is associated with ossification of the posterior longitudinal ligament (OPLL), and in the late 1970s, Resnick et al. noted that DISH coexisted with OPLL in up to 40% to 50% of cases, thus suggesting that DISH and OPLL are closely related. Some scholars believe that the occurrence in the cervical spine is often combined with obvious calcification of laryngeal cartilage, which can serve as a clue to suggest the diagnosis; and once accompanied by ossification of the posterior longitudinal ligament, there is a possibility of spinal cord dysfunction caused by OPLL. 6. Treatment The treatment principles of DISH are similar to those of osteoarthritis, aiming to alleviate symptoms, reduce restrictions on joint function and slow down the progression of the disease. 6.1 Non-surgical treatment is generally appropriate, including weight loss, physical therapy, oral NSAIDs and analgesics, local closure, external fixation, etc. Treat concomitant diabetes, gout, etc. accordingly. 6.2 Surgical treatment When the spinal stenosis caused by DISH compresses the spinal cord and nerve roots, treatment should be carried out according to the spinal stenosis, and if necessary, surgical decompression and stabilization of the corresponding segment should be performed, and when traumatic fracture of the diseased segment occurs in DISH, treatment should be based on the principles of fracture treatment. Early misdiagnosis and delayed diagnosis of spinal fractures in patients with DISH often occur, with a high incidence of concurrent spinal cord injury in the thoracic spine. Fractures can be divided into two types: (1) fracture lines pass through the middle of the ankylosed segment of the spine, involving the vertebral body; (2) fractures occur at the upper or lower end of the ankylosed segment of the spine, often with intervertebral disc injury. The fracture characteristics are distinctly different from those of ankylosing spondylitis spine fractures, which are mostly transvertebral disc fractures. It is emphasized that for those with fractures in DISH, early stabilization measures should be taken to prevent bone discontinuity and deformity healing and to avoid delayed nerve damage.