Journal of the American Academy of Orthopaedic Surgeons 258 In 1950, Forestier and Rotes-Querol described a disorder characterized by spinal stiffness, osteophytosis, and “flowing” new-bone formation about the thoracic spine. They termed it “senile ankylosing hyperostosis” and distinguished it from ankylosing spondylitis. They documented clini- cal and radiographic findings in a series of 200 patients, as well as de- scriptions of pathologic specimens. Over the years, Forestier and various other authors have described numer- ous extraspinal findings. The con- dition is a systemic bone-forming diathesis with primary spinal and various extraspinal clinical and radio- graphic findings. 1 During this evolution of under- standing, the disorder has been given many labels. These include ankylosing hyperostosis, Forestier’s disease, generalized juxta-articular ossification of vertebral ligaments, and spondylosis hyperostotica. The most descriptive and inclusive term, and the one used in the most recent literature, is diffuse idiopathic skele- tal hyperostosis (DISH), which was introduced by Resnick. 1,2 In an effort to understand the eti- ology of DISH, investigators have sought relationships with other syn- dromes. Historically, both rheuma- toid arthritis and ankylosing spon- dylitis were thought to be related to DISH. Because the type of new- bone formation observed in DISH resembles that which occurs in sev- eral seronegative spondyloarthrop- athies, attempts have also been made to establish an association to HLA-B27; however, no convincing evidence of such an association exists. Some endocrine and metabol- ic syndromes, such as acromegaly and hypervitaminosis A, can also produce hyperostosis resembling that seen in DISH. Increased preva- lences of diabetes mellitus, glucose intolerance, hyperuricemia, and dyslipidemia have been associated with DISH. 3 HLA-B8 is common among patients with both DISH and diabetes mellitus. 2 Despite the many similarities to other syndromes that cause osseous outgrowths or anky- losis, convincing evidence linking DISH to other systemic disorders is lacking, and the cause remains unknown. 2,4-6 Dr. Belanger is Resident in Orthopaedic Sur- gery, Michigan State University, Kalamazoo Center for Medical Studies, Kalamazoo. Dr. Rowe is Professor of Surgery, Department of Orthopaedics, Michigan State University, Kalamazoo Center for Medical Studies. Reprint requests: Dr. Belanger, Michigan State University, Kalamazoo Center for Medi- cal Studies, 1000 Oakland Drive, Kalamazoo, MI 49008. Copyright 2001 by the American Academy of Orthopaedic Surgeons. Abstract Diffuse idiopathic skeletal hyperostosis (DISH) is a common disorder of unknown etiology that is characterized by back pain and spinal stiffness. There may be mild pain if ankylosis has occurred. The condition is recognized radio- graphically by the presence of “flowing” ossification along the anterolateral margins of at least four contiguous vertebrae and the absence of changes of spondyloarthropathy or degenerative spondylosis. Even in patients who present with either lumbar or cervical complaints, radiographic findings are almost uni- versally seen on the right side of the thoracic spine. Thus, radiographic exami- nation of this area is critical when attempting to establish a diagnosis of DISH. The potential sequelae of hyperostosis in the cervical and lumbar spine include lumbar stenosis, dysphagia, cervical myelopathy, and dense spinal cord injury resulting from even minor trauma. There may be a delay in diagnosis of spinal fractures in a patient with DISH because the patient often has a baseline level of spinal pain and because the injury may be relatively trivial. The incidence of delayed neurologic injury due to such fractures is high as a result of unrecog- nized instability and subsequent deterioration. Extraspinal manifestations are also numerous and include an increased risk of heterotopic ossification after total hip arthroplasty. Prophylaxis to prevent heterotopic ossification may be indicated for these patients. J Am Acad Orthop Surg 2001;9:258-267 Diffuse Idiopathic Skeletal Hyperostosis: Musculoskeletal Manifestations Theodore A. Belanger, MD, and Dale E. Rowe, MD Theodore A. Belanger, MD, and Dale E. Rowe, MD Vol 9, No 4, July/August 2001 259 Prevalence Diffuse idiopathic skeletal hyperos- tosis is a common disease, which is most prevalent in persons over 50 years of age. In an autopsy series, Boachie-Adjei and Bullough 7 re- ported that 28% of the spines of sub- jects with an average age of 65 years had evidence of DISH. Mata and co- workers 4,8 documented a frequency of 2.5% to 10% in persons over age 70, with a slight male predominance. Other authors have stated that the prevalence is as high as 15% in women and 25% in men over age 50, and 26% in women and 28% in men over 80. 9,10 Resnick and Niwayama 2 postulated that the disorder may begin between the ages of 20 and 40 years but requires several decades to become mature enough to meet di- agnostic criteria. They also noted no difference in frequency of the disease between black and white persons. Clinical Presentation The usual presentation is a middle- aged or older patient with chronic mild pain in the middle to lower back, spinal stiffness, and the typical radiographic changes in the thoracic spine. Tendinitis may also be pres- ent in any location, but most often in the Achilles tendon. Dysphagia sec- ondary to large cervical osteophytes is an occasional complication of DISH. 4,11-15 Overall, clinical findings are mild in comparison to the dra- matic radiographic findings. The minimal pain experienced by some patients may be a consequence of the relative stabilization of spinal segments through ankylosis. In fact, many patients are asymptomatic, and DISH is discovered incidentally. Spinal Manifestations Diffuse idiopathic skeletal hyperos- tosis is predominantly a radio- graphic diagnosis with three major diagnostic criteria, as outlined by Forestier and refined by Resnick and Niwayama 2 (Table 1). The first criterion, flowing ossification along the anterolateral borders of at least four contiguous spinal segments, is the essence of DISH. The other two criteria, absence of degenerative changes and sclerosis or ankylosis of facet or sacroiliac joints, serve to eliminate the spondylosis of degen- erative spinal disorders and anky- losing spondylitis as alternative diagnoses. In practice, some patients present with involvement of fewer than four contiguous vertebrae. Exclusion of these patients is arbitrary, to avoid confusion of DISH with other syn- dromes. In fact, patients with DISH can have few radiographically evi- dent spinal manifestations and varying degrees of extraspinal symptoms and findings. 1,2 Thoracic Spine The axial manifestations of DISH are the most frequent and character- istic, forming the basis of the diag- nosis and offering an explanation for most patient complaints. The thoracic spine is the most commonly involved segment, often in isolation. Pain can be present in other areas of the spine, with isolated radiographic changes in the thorax, particularly from T7 to T11. 2 Thus, a high index of suspicion must be maintained, with a low threshold for imaging the thoracic spine, even in patients with primarily lumbar or cervical complaints. Thoracic myelopathy has been reported, but is a rare manifestation of DISH. 16,17 Radiographic imaging of the tho- racic spine in the anteroposterior (AP) and lateral planes commonly reveals large syndesmophytes and flowing, laminated new-bone for- mation along the anterolateral mar- gins of vertebral bodies, often con- tinuing across the disk spaces (Fig. 1). The syndesmophytes project hori- zontally from the vertebral bodies with the classic appearance of flow- ing candle wax, becoming confluent to form an extra-articular ankylosis. They should be distinguished from the vertically oriented “bamboo spine” outgrowths that form an intra-articular ankylosis in ankylos- ing spondylitis. The syndesmo- phytes of DISH usually appear much more prominent on the right side of the thoracic spine, whereas they are commonly symmetrical in the cervical and lumbar spine. This is postulated to be due to a protec- tive effect afforded by the pulsatile aorta on the left side of the thoracic vertebrae. Patients with DISH and situs inversus show ossification mainly on the left side of the tho- racic spine. 2,18 Ligamentous calcification may be as thick as 2 cm in some instances. Hyperostosis of posterior elements is rare, although hyperostosis of costovertebral joints may be present. Table 1 Diagnostic Criteria for DISH 2 1. Flowing ossification along the anterolateral aspect of at least four contiguous vertebrae 2. Preservation of disk height in the involved vertebral segment; the relative absence of significant degenerative changes, such as marginal sclerosis in vertebral bodies or vacuum phenomenon 3. Absence of facet-joint ankylosis; absence of sacroiliac erosion, sclerosis, or intra-articular osseous fusion Diffuse Idiopathic Skeletal Hyperostosis Journal of the American Academy of Orthopaedic Surgeons 260 Osteopenia, which is commonly seen in ankylosing spondylitis, is not typically profound in DISH. In fact, the radiodensity may appear excessive in relation to patient age. Facet articulations and disk spaces are generally preserved. The pres- ence of significant degenerative changes, such as facet hypertrophy and disk-space narrowing, should cast doubt on the diagnosis of DISH. Technetium bone scanning can show increased uptake in areas of involvement, which may be con- fused with evidence of metastatic disease. 19 Patients with diffuse complaints of back, neck, or extremity pain and/or stiffness that is worse in the morning or evening and is aggra- vated by cold weather may have objective radiographic findings lim- ited to the thoracic spine that are visualized on thoracic spine films or chest radiographs. 20 Often, these patients have undergone extensive workup or even surgery on the lum- bar spine without a diagnosis of DISH having been established. The presence of such back complaints, even with other findings in the lum- bar spine, warrants at least one set of radiographs of the thoracic spine to rule out the presence of DISH. This may alert the physician that a lumbar or cervical fusion is not likely to ameliorate all of the patient’s axial symptoms. However, the presence of DISH is not a contraindication to an appropriate procedure for steno- sis, instability, painful degenerative spondylosis, disk herniation, or other cervical and lumbar disorders. Cervical Spine Involvement of the cervical spine is less frequent than involvement of the lumbar or thoracic spine, al- though it is by no means rare. 9 Pain and stiffness of the neck may be prominent symptoms and are occa- sionally the presenting complaints. Radiographic findings are most common in the lower segments and less prevalent at the more cephalad levels. Ossification and loss of elas- ticity occur along the anterior para- vertebral tissues, such as the anterior longitudinal ligament. Cervical hyper- ostosis may be seen to be as much as 12 mm thick on a lateral radio- graph. 2 Syndesmophytes occur symmetrically along the anterolateral vertebral bodies. Ankylosis of ver- tebral bodies occurs with secondary ankylosis of apophyseal and unco- vertebral joints, as distinguished from ankylosing spondylitis, which often fuses across these joints pri- marily. Ligamentum flavum hyper- trophy, dystrophic calcification of spinal ligaments (including ossifica- tion of the posterior longitudinal ligament), and mild cervical kypho- sis can occur, occasionally resulting in cervical spinal stenosis and mye- lopathy. 2,9,21 Diffuse idiopathic skeletal hyper- ostosis of the cervical spine can also cause complications with adjacent soft-tissue structures when large osseous excrescences are present. Dysphagia is often the result of large cervical syndesmophytes, which are present in as many as 28% of patients with DISH. 2,11,13-15 Hoarseness, sleep apnea, and diffi- culty with intubation have all been reported to be consequences of cer- vical DISH. 2,22,23 If syndesmophytes are imping- ing on anterior structures, surgical resection can be palliative. 13-15 In cases of multilevel cervical stenosis and myelopathy with preserved lor- dosis, laminoplasty or laminectomy may be indicated. In other cases, anterior decompression and stabili- zation may be necessary. Lumbar Spine Radiographic changes are com- mon in the lumbar spine, resem- bling those in the thoracic spine without the predilection for right- sided involvement (Fig. 2). How- ever, patients often complain of low back pain or stiffness without the presence of changes on lumbar radio- graphs. Radiographic evidence of A B Figure 1 AP (A) and lateral (B) thoracic spine radiographs of a 60-year-old woman show typical findings of DISH. Note the right-sided, nonmarginal syndesmophytes; the absence of disk-space narrowing; and the well-preserved bone density. Theodore A. Belanger, MD, and Dale E. Rowe, MD Vol 9, No 4, July/August 2001 261 DISH in the lumbar spine is most frequently seen in the upper levels and is less common caudally. Vertebral hyperostosis may be as much as 2 cm thick. Interspinous ligament calcification may also be seen. Degenerative changes such as disk-space narrowing and facet- joint sclerosis and narrowing, which are not considered typical of DISH, are common between the fourth lumbar and first sacral vertebrae. This is probably related to the nor- mal stress imposed on the lumbo- sacral area, exacerbated by a stiff spine superiorly. These degenera- tive changes may have been treated surgically before recognition of DISH (Fig. 3, A). Hypertrophy and ossification of the ligamentum flavum and hyperostosis of posterior spinal elements, especially around the facet joints, may result in symp- tomatic stenosis of the spinal ca- nal. 2,24,25 Significant compression of the inferior vena cava due to large anterior lumbar osseous excres- cences has been reported. 26 Traumatic Changes Patients with DISH are at high risk for fracture and instability from even minor trauma. Fractures of the spine in patients with DISH are often characterized by a delay in diagnosis and a high rate of imme- diate and delayed neurologic conse- quences. The increased incidence of fracture instability in these patients is a consequence of ankylosis of the vertebral segments proximal and distal to the fracture, which creates increased lever arms that can cause displacement of the spine even in low-energy injuries. 27-29 They occur in the middle or at the ends of anky- losed segments, as in ankylosing spondylitis. Hyperextension inju- ries are frequent, involving either disk disruption or fracture through the middle of a vertebral body. 27,28 Patients with DISH, neck pain, and a history of trauma must be carefully evaluated for occult fracture with computed tomography (CT) or mag- netic resonance (MR) imaging. In the cervical spine, the changes in canal diameter, alignment, and mobility of motion segments not only cause neck pain and stiffness but put patients with DISH at risk for severe neurologic injury. As in the thoracic spine, hyperextension injuries are common. Odontoid A B C D Figure 2 AP (A) and lateral (B) lumbar spine radiographs of a 72-year-old man. Note the nonbridging, nonmarginal syndesmophytes; preservation of facet joints and disk spaces; and postoperative changes at L5-S1. The typical flowing ossification was also apparent along the anterolateral margins of the lower thoracic vertebrae. AP (C) and lateral (D) right elbow radiographs of the same patient show diffuse changes. He had no history of trauma, infection, or surgery affecting the elbow and had only minimally painful stiffness. On the AP view, note the preservation of joint space, with flowing ossification along the medial edge of the coronoid process. The lateral view shows large enthesophytes project- ing proximally from the coronoid, olecranon, and trochlea, as well as small osteophytes projecting distally from the radial head. Diffuse Idiopathic Skeletal Hyperostosis Journal of the American Academy of Orthopaedic Surgeons 262 fractures and atlantoaxial subluxa- tion have been reported in associa- tion with DISH, but are not consid- ered typical findings. 30 Even minor trauma can result in cervical fracture, with a high incidence of associated neurologic injury and mortality. 9 Unfortunately, the diagnosis of the fracture is often delayed and may not be made until a neurologic de- ficit occurs. 9 Treatment of fractures is similar to that of patients with other anky- losing conditions. The physician must consider the additional insta- bility caused by poor ligament integrity and increased lever arms. It is important to note that the degree of instability is likely to be underrepresented on radiographs. A thorough understanding of the pathophysiology of DISH is neces- sary to be able to adequately inter- pret radiographs of these patients and to accurately project their clin- ical course and risk. Better un- derstanding of the injury may be obtained through CT or MR imag- ing with multiplanar reconstruc- tions. Cervical traction may result in excessive distraction due to the lack of ligamentous structures and should be used cautiously. The use of open reduction and internal fixation is recommended to prevent progres- sion and delayed neurologic com- promise (Fig. 4). Instrumentation must be of sufficient length to coun- teract the increased deforming forces acting at the fracture site. Given that preoperatively the spine is relatively stiff and multiple artic- ulations may have to be fused, in- creasing the length of instrumenta- tion does not necessarily sacrifice mobile motion segments. Anterior decompression and strut grafting may be required if ventral compres- sion is present; this should be aug- mented with posterior stabilization. In a series of 20 patients with cervi- cal fractures and DISH, the mortality of those treated surgically was 15%, compared with 67% for those treated nonoperatively. 9 Extraspinal Manifestations Although Forestier’s initial descrip- tion of DISH commented on occa- sional extraspinal manifestations, many subsequent authors have since delineated findings that range from rare to commonplace. In par- ticular, tendinitis and entheso- phytes (osseous outgrowths at the sites of attachment of tendon, liga- ment, or capsule to bone) are very common findings. Many joints can be affected, and some patients have diffuse, vague aching similar to that which occurs with polymyalgia rheumatica. 2 Subtle periostitis at the site of ligament or tendon in- sertion is often seen. Each anatomic location has characteristic findings associated with DISH, which are usually bilateral and symmetrical. 1 Pelvis The most characteristic findings in the pelvis are enthesophytes involving the iliac wing and ischial tuberosity and calcification of the sacrotuberous and iliolumbar liga- ments (Fig. 3, B). 31 Periarticular osteophytes about the hip, sacroil- iac joints, and symphysis pubis can often be found. 1 The osseous ex- crescences are similar in appear- ance to those seen in the spine. Intra-articular or para-articular an- kylosis rarely occurs about a joint. Bone proliferation (“whiskering”) can be seen at sites of ligament and tendon attachment. Bone erosions in the sacroiliac joints and at the sites of ligament attachment, com- monly seen in ankylosing spon- dylitis and other disorders, are generally absent in DISH. While abnormalities of the sacroiliac joints generally exclude the diagno- sis of DISH, bridging or nonbridg- ing osteophytes about the sacroiliac joint have been reported in patients with DISH. 32 With the exception of the symptomatic hip, most pelvic findings do not require surgical in- tervention. A B Figure 3 A, Lateral radiograph of the lower lumbar spine of a 60-year-old man treated with posterior intertransverse spinal fusion for postlaminectomy spondylolisthesis at L3-4 shows impressive syndesmophyte formation related to DISH. Note the absence of disk-space nar- rowing at L4-5 and L5-S1 and the presence of the large osseous excrescence. The patient also had classic changes in the thoracic spine and pelvis. B, AP radiograph of the pelvis of the same patient shows ossification of the sacrotuberous ligaments (arrows) with sparing of the sacrospinous ligaments, which is a pathognomonic finding in DISH. “Whiskering” of the iliac wings and ischial tuberosities and subtle osteophytosis about the pubic symphysis and superior acetabula with preservation of the sacroiliac joints are also common. Theodore A. Belanger, MD, and Dale E. Rowe, MD Vol 9, No 4, July/August 2001 263 Hip Hip involvement is variable, with some patients having few or no pathologic changes in the hip. Those with signs and symptoms may have periarticular bone proliferation with an intact joint space (Fig. 5), hyperos- tosis with a narrowed joint space, or osteonecrosis. 2 It has not been deter- mined which of these findings are related to DISH and which are age- related. Patients with DISH and a severely symptomatic degenerative hip may require total hip arthroplasty. These patients may be at increased risk for heterotopic ossification. 2,33-35 It has been suggested that this could be prevented by preoperative irradia- tion 33 or by the use of warfarin in the postoperative period. 34 The use of indomethacin, aspirin, subcuta- neous heparin, and low-molecular- weight heparin in this setting has not been investigated. The clinical significance of het- erotopic ossification in patients with DISH after total hip arthro- plasty is debated. Guillemin et al 34 retrospectively reviewed the data on 67 patients after total hip arthro- plasty, 16 of whom had DISH. That study showed a higher incidence of heterotopic ossification in patients with DISH than in those without DISH (56% [9 of 16] vs 22% [11 of 51]). The incidence of heterotopic ossifi- cation was less in patients treated with anti-vitamin K drugs (e.g., warfarin) for 3 months postopera- tively than in those treated with subcutaneous heparin over the same period (17% [5 of 29] vs 39% [15 of 38]). Fahrer et al 35 reported on a series of 204 patients who underwent total hip arthroplasty, 38 of whom had DISH. Postoperative ossifica- tion developed in 30% of the DISH patients, compared with 10% of those without DISH. The authors found low frequencies of significant pain (10%) and functional limita- tion (26% with less than 70 degrees of hip motion) as a result of ossifi- cation and did not feel that prophy- laxis was justified. Figure 4 A, Supine lateral radiograph of a 76-year-old man who fell at home demon- strates a benign-appearing fracture of the C5 vertebral body (arrow). Large anterior bridging osteophytes from C4 to C7 are pres- ent. B, Patient was immobilized in a cervi- cothoracic brace. When upright, he com- plained of severe neck pain and bilateral C6 radiculopathy, which resolved when he was supine. This upright lateral radiograph shows increased kyphosis and subluxation of the C5-6 facets to the perched position (arrow). C, Axial CT scan of C5-6 demon- strates vertebral body fracture and fracture of the lateral mass of C6 (arrows). D, Post- operative lateral radiograph following poste- rior stabilization and fusion with AO instru- mentation (an off-label use of this device). E, Postoperative anteroposterior radiograph. A B D E C 5 5 5 5 6 Diffuse Idiopathic Skeletal Hyperostosis Journal of the American Academy of Orthopaedic Surgeons 264 Knee Resnick et al 1,2 reported that pa- tients with DISH have a 29% preva- lence of knee changes, compared with 5% of control subjects. Tendi- nous ossification can occur in asso- ciation with the quadriceps mecha- nism, with patellar hyperostosis including large osseous excres- cences on the poles. A prominent tibial spine is very common. An in- creased incidence of symptomatic osteoarthritis of the knee has not been observed. Foot and Ankle At least 70% of DISH patients have manifestations involving the foot and ankle. 2,36 Any bone in the foot may exhibit hyperostosis. The numerous sites of ligament and ten- don attachment make the foot par- ticularly prone to spur formation. Calcaneal spurs are common, occur- ring in as many as 76% of patients, compared with 19% of control sub- jects. 2,36 The cortex of the calcaneus may be thickened. Calcification of the Achilles tendon or plantar fascia may be seen, with or without associ- ated symptoms of Achilles tendini- tis or plantar fasciitis. Heel pain oc- curs in an estimated 23% of patients with DISH, occasionally as the pre- senting symptom. Garber and Silver 36 suggested that the presence of large calcaneal spurs in the set- ting of Achilles tendinitis or plantar fasciitis should lead one to consider DISH as an underlying diagnosis. Enthesophytes may also be seen on the dorsal talus (talar beaking), medial navicular, lateral and plantar cuboid, and the base of the fifth metatarsal. 1 Shoulder Irregular osseous excrescences can occur at the deltoid tubercle, as well as in the greater and lesser tuberosities. Hyperostosis can be seen in the inferior glenoid and dis- tal clavicle, as well as at the sites of attachment of the coracoclavicular ligaments. 1 These changes are vari- ably associated with pain, stiffness, and loss of motion. Primary shoulder osteoarthrosis is relatively uncom- mon; therefore, a symptomatic pa- tient should be assessed with care- ful attention to the history and physical examination, which may reveal diffuse complaints that sug- gest DISH. Treatment for DISH of the shoul- der is largely symptomatic and may include activity modification, non- steroidal anti-inflammatory medica- tion, and/or physical therapy. Sur- gery is rarely necessary, and it is often difficult to justify it solely on the basis of manifestations of DISH. Elbow Spurs on the olecranon are fre- quent findings in DISH (Fig. 2, C and D). In one study, 2 they were noted in 48% of patients with DISH, compared with 10% of control sub- jects. Hyperostosis can occur along the distal medial humerus. Patients with enthesophytes are frequently symptomatic, 2 although the clinical relevance of radiographically evi- dent elbow hyperostosis has been challenged. 37 Irregularities of the proximal radioulnar joint and epi- condylitis can be seen as well. These entities are generally treated nonop- eratively. Hand and Wrist Cortical thickening may be seen in the tubular bones, as well as hyperostosis and spur formation in periarticular sites, such as the metacarpal heads. The distal pha- langeal tufts may appear pointed (“arrowheading”). 38 Soft-tissue and cartilage hypertrophy are present in acromegaly but not in DISH. An increased incidence of osteoarthro- sis of the hand, especially in the interphalangeal joints, has been suggested. Irregularities at the in- sertion sites for the interosseous membrane and in the distal radio- ulnar joint are occasionally seen. Figure 5 AP (A) and frog-leg lateral (B) radiographs of the right hip of a 51-year-old man with DISH diagnosed on chest radiographs. He presented with right hip discomfort and stiffness that had developed over many years. Note the profound periarticular hyperosto- sis and relative preservation of the hip joint space. At the time of total hip arthroplasty, these osteophytes were found to be intra-articular, encroaching on the lesser trochanter, and impinging on the superior acetabular rim. A B Theodore A. Belanger, MD, and Dale E. Rowe, MD Vol 9, No 4, July/August 2001 265 Diagnosis The differential diagnosis of back pain and spondylophytosis in- cludes a large number of disorders (Table 2). 2 A careful history delin- eating the nature and location of back pain is necessary. Back pain that is severe or acute in onset is not likely to be related solely to DISH. The presence of extraspinal musculoskeletal symptoms should be sought. There are no diagnostic labora- tory findings, but evaluation may exclude other potential diagnoses. The erythrocyte sedimentation rate and C-reactive protein, rheumatoid factor, and antinuclear antibody levels are typically normal. If DISH is suspected in an adult, the thoracic spine should be evalu- ated radiographically to establish the diagnosis. Chest radiographs are adequate as screening tests for DISH. 20 The lumbar spine is usually evaluated radiographically, as this is the most common area of com- plaint. Including the sacroiliac joints on these films can be helpful in ruling out other entities, such as seronegative spondyloarthropa- thies. Other sites of pain should be imaged with plain radiography, es- pecially the heel, elbow, sacroiliac joints, and cervical spine. In non- traumatic situations, bone scans are not often helpful and can falsely give the appearance of multiple periarticular metastases. The recognition of DISH can be useful to patients by reassuring them that they have an objectively identifiable disorder that explains their symptoms. These patients have frequently been told that they have arthritis and often feel that they are not being taken seriously. A simple radiograph of the thoracic spine or the chest may validate their complaints and help direct therapy, which often establishes a good relationship between patient and physician. Once the diagnosis of DISH has been established, important associ- ated sequelae must be identified or ruled out. Neck discomfort after even minor trauma to the cervical spine needs to be aggressively eval- uated with radiographs supple- mented by CT, myelography with CT, or MR imaging. Suspected spinal stenosis at all levels deserves a similarly aggressive approach. Dysphagia may warrant evalua- tion with cervical spine radiographs and a swallowing study. Consulta- tion with an otorhinolaryngologist or a gastroenterologist may be appropriate to ensure that the dys- phagia is truly related to an osteo- phyte rather than a tumor or other process. Endoscopy may be indi- cated in such cases. Treatment The treatment of DISH predomi- nantly involves nonoperative mea- sures with occasional surgical inter- vention for specific sequelae. For patients with isolated back pain or enthesopathies, activity modifica- tion, physical therapy, corset or brace wear, nonsteroidal anti- inflammatory medications, and bis- phosphonate therapy are the main- stays of treatment, but the efficacy of these modalities is not well estab- lished. Generally, surgery is not indi- cated for DISH in the absence of some other diagnosis, such as frac- ture, stenosis, tumor, infection, or painful deformity. Fortunately, debilitating pain is rare in the ab- sence of neurologic or visceral im- pingement, probably because bony ankylosis prevents painful motion. The joint reconstruction surgeon should be aware of the increased risk of heterotopic ossification after total hip arthroplasty; prophylaxis may be appropriate. Summary Diffuse idiopathic skeletal hyperos- tosis is a very common, often occult bone-forming diathesis with many musculoskeletal manifestations. The diagnosis is based on the presence of flowing ossification along the anterolateral aspects of at least four vertebrae, typically in the thoracic spine. There must be an absence of changes characteristic of degenera- tive spondylosis or spondyloar- thropathies, such as ankylosing spondylitis. A diagnosis of DISH should be suspected in adult pa- tients who present with back pain and spinal stiffness. Radiographic evaluation of the thoracic spine must be performed, even if pain is localized to the lumbar or cervical areas. All other areas of muscu- loskeletal pain should be evaluated radiographically, looking for hyper- ostosis or enthesopathy. Awareness of DISH can have important implications. In addition to suggesting therapeutic measures, establishing the diagnosis serves to reassure the patient that his or her Table 2 Differential Diagnosis of Back Pain and Spondylophytosis DISH Spondylosis deformans Ankylosing spondylitis Acromegaly Hypoparathyroidism Fluorosis Ochronosis Charcot spine Sternocostoclavicular hyperostosis Intervertebral osteochondrosis Spondylitic variants (e.g., psoriasis, Reiter’s syndrome, inflammatory bowel disease, Whipple’s disease) Pachydermoperiostosis Pseudogout X-linked hypophosphatemic osteomalacia Diffuse Idiopathic Skeletal Hyperostosis Journal of the American Academy of Orthopaedic Surgeons 266 symptoms are related to an objec- tively identifiable condition, which can establish trust between physi- cian and patient. Furthermore, it may alert the surgeon to look for certain associated problems, such as dysphagia, cervical myelopathy, spinal fracture, lumbar stenosis, het- erotopic ossification, and enthe- sopathy, that often require surgical intervention. The manifestations of DISH are numerous and vary among patients. Awareness of the disorder and a high index of suspicion can add a great deal to the clinical acumen of practitioners of nearly every ortho- paedic subspecialty. This sensitiza- tion, perhaps coupled with only a chest radiograph, often allows a cor- rect diagnosis, allaying the frustra- tions of delayed (or absent) diagno- sis and occasionally identifying and preventing a serious sequela. References 1. Resnick D, Shaul SR, Robins JM: Diffuse idiopathic skeletal hyperosto- sis (DISH): Forestier’s disease with extraspinal manifestations. Radiology 1975;115:513-524. 2. Resnick D, Niwayama G: Diffuse idio- pathic skeletal hyperostosis (DISH): Ankylosing hyperostosis of Forestier and Rotes-Querol, in Resnick D (ed): Diagnosis of Bone and Joint Disorders, 3rd ed. Philadelphia: WB Saunders, 1995, vol 3, pp 1463-1495. 3. Vezyroglou G, Mitropoulos A, Kyriazis N, Antoniadis C: A metabolic syn- drome in diffuse idiopathic skeletal hyperostosis: A controlled study. J Rheumatol 1996;23:672-676. 4. Mata S, Fortin PR, Fitzcharles MA, et al: A controlled study of diffuse idio- pathic skeletal hyperostosis: Clinical features and functional status. Medicine (Baltimore) 1997;76:104-117. 5. Daragon A, Mejjad O, Czernichow P, et al: Vertebral hyperostosis and dia- betes mellitus: A case-control study. Ann Rheum Dis 1995;54:375-378. 6. Mata S, Wolfe F, Joseph L, Esdaile JM: Absence of an association of rheuma- toid arthritis and diffuse idiopathic skeletal hyperostosis: A case-control study. J Rheumatol 1995;22:2062-2064. 7. Boachie-Adjei O, Bullough PG: Inci- dence of ankylosing hyperostosis of the spine (Forestier’s disease) at autop- sy. Spine 1987;12:739-743. 8. Mata S, Chhem RK, Fortin PR, Joseph L, Esdaile JM: Comprehensive radio- graphic evaluation of diffuse idiopath- ic skeletal hyperostosis: Development and interrater reliability of a scoring system. Semin Arthritis Rheum 1998;28: 88-96. 9. Meyer PR Jr: Diffuse idiopathic skele- tal hyperostosis in the cervical spine. Clin Orthop 1999;359:49-57. 10. Weinfeld RM, Olson PN, Maki DD, Griffiths HJ: The prevalence of diffuse idiopathic skeletal hyperostosis (DISH) in two large American Midwest metro- politan hospital populations. Skeletal Radiol 1997;26:222-225. 11. Kritzer RO, Rose JE: Diffuse idiopathic skeletal hyperostosis presenting with thoracic outlet syndrome and dyspha- gia. Neurosurgery 1988;22(6 pt1):1071- 1074. 12. Davies RP, Sage MR, Brophy BP: Cer- vical osteophyte induced dysphagia. Australas Radiol 1989;33:223-225. 13. Fahrer H, Markwalder T: Dysphagia caused by diffuse idiopathic skeletal hyperostosis. Clin Rheumatol 1988;7: 117-121. 14. Burkus JK: Esophageal obstruction secondary to diffuse idiopathic skele- tal hyperostosis. Orthopedics 1988;11: 717-720. 15. Kibel SM, Johnson PM: Surgery for osteophyte-induced dysphagia. J Laryngol Otol 1987;101:1291-1296. 16. Reisner A, Stiles RG, Tindall SC: Diffuse idiopathic skeletal hyperosto- sis causing acute thoracic myelopathy: A case report and discussion. Neuro- surgery 1990;26:507-511. 17. Wilson FMA, Jaspan T: Thoracic spinal cord compression caused by diffuse idiopathic skeletal hyperostosis (DISH). Clin Radiol 1990;42:133-135. 18. Carile L, Verdone F, Aiello A, Buon- gusto G: Diffuse idiopathic skeletal hyperostosis and situs viscerum inver- sus. J Rheumatol 1989;16:1120-1122. 19. Lee S, Coel M, Ko J, Edwards J: Diffuse idiopathic skeletal hyperostosis can resemble metastases on bone scan. Clin Nucl Med 1993;18:791-792. 20. Mata S, Hill RO, Joseph L, et al: Chest radiographs as a screening test for dif- fuse idiopathic skeletal hyperostosis. J Rheumatol 1993;20:1905-1910. 21. Stechison MT, Tator CH: Cervical myelopathy in diffuse idiopathic skel- etal hyperostosis: Case report. J Neurosurg 1990;73:279-282. 22. Gay I, Elidan J: Dysphonia caused by Forestier’s disease. Ann Otol Rhinol Laryngol 1988;97(3 pt1):275-276. 23. Palmer JHM, Ball DR: Awake tracheal intubation with the intubating laryngeal mask in a patient with diffuse idio- pathic skeletal hyperostosis. Anaesthesia 2000;55:70-74. 24. Leroux JL, Legeron P, Moulinier L, et al: Stenosis of the lumbar spinal canal in vertebral ankylosing hyperostosis. Spine 1992;17:1213-1218. 25. Karpman RR, Weinstein PR, Gall EP, Johnson PC: Lumbar spinal stenosis in a patient with diffuse idiopathic skeletal hypertrophy syndrome. Spine 1982;7:598-603. 26. Scapinelli R: Compression of the infe- rior vena cava due to diffuse idiopath- ic skeletal hyperostosis. Rev Rhum Engl Ed 1997;64:198-201. 27. Paley D, Schwartz M, Cooper P, Harris WR, Levine AM: Fractures of the spine in diffuse idiopathic skeletal hyperos- tosis. Clin Orthop 1991;267:22-32. 28. Burkus JK, Denis F: Hyperextension injuries of the thoracic spine in diffuse idiopathic skeletal hyperostosis: Report of four cases. J Bone Joint Surg Am 1994;76:237-243. 29. Mody GM, Charles RW, Ranchod HA, Rubin DL: Cervical spine fracture in diffuse idiopathic skeletal hyperosto- sis. J Rheumatol 1988;15:129-131. 30. Oostveen JCM, van de Laar MAFJ, Tuynman FHB: Anterior atlantoaxial subluxation in a patient with diffuse idiopathic skeletal hyperostosis. J Rheumatol 1996;23:1441-1444. 31. Haller J, Resnick D, Miller CW, et al: Diffuse idiopathic skeletal hyperosto- sis: Diagnostic significance of radio- graphic abnormalities of the pelvis. Radiology 1989;172:835-839. 32. Durback MA, Edelstein G, Schumacher HR Jr: Abnormalities of the sacroiliac joints in diffuse idiopathic skeletal hyperostosis: Demonstration by com- puted tomography. J Rheumatol 1988; 15:1506-1511. 33. Pellegrini VD Jr, Gregoritch SJ: Preop- erative irradiation for prevention of Theodore A. Belanger, MD, and Dale E. Rowe, MD Vol 9, No 4, July/August 2001 267 heterotopic ossification following total hip arthroplasty. J Bone Joint Surg Am 1996;78:870-881. 34. Guillemin F, Mainard D, Rolland H, Delagoutte JP: Antivitamin K pre- vents heterotopic ossification after hip arthroplasty in diffuse idiopathic skeletal hyperostosis: A retrospective study in 67 patients. Acta Orthop Scand 1995;66:123-126. 35. Fahrer H, Koch P, Ballmer P, Enzler P, Gerber N: Ectopic ossification fol- lowing total hip arthroplasty: Is dif- fuse idiopathic skeletal hyperostosis a risk factor? Br J Rheumatol 1988;27: 187-190. 36. Garber EK, Silver S: Pedal manifesta- tions of DISH. Foot Ankle 1982;3:12-16. 37. Beyeler C, Schlapbach P, Gerber NJ, et al: Diffuse idiopathic skeletal hyper- ostosis (DISH) of the elbow: A cause of elbow pain? A controlled study. Br J Rheumatol 1992;31:319-323. 38. Littlejohn GO, Urowitz MB, Smythe HA, Keystone EC: Radiographic fea- tures of the hand in diffuse idiopathic skeletal hyperostosis (DISH): Com- parison with normal subjects and acromegalic patients. Radiology 1981; 140:623-629. . radiographic exami- nation of this area is critical when attempting to establish a diagnosis of DISH. The potential sequelae of hyperostosis in the cervical and lumbar spine include lumbar stenosis, dysphagia,. should be sought. There are no diagnostic labora- tory findings, but evaluation may exclude other potential diagnoses. The erythrocyte sedimentation rate and C-reactive protein, rheumatoid factor,