European Journal of Radiology 27 (1998) S7 – S11

Diffuse idiopathic skeletal hyperostosis

Mario Cammisa *, Antonio De Serio, Giuseppe Guglielmi

Diagnostic Imaging Department, IRCCS Casa Sollie6o della Sofferenza, V. le Cappuccini, 71013 S. Gio6anni Rotondo (FG), Italy

Abstract

Objective: To describe the axial and appendicular skeleton findings of diffuse idiopathic skeletal hyperostosis. To analyze the
role of conventional radiography, computed tomography (CT) and magnetic resonance imaging (MRI) in the diagnosis of this
condition. To discuss the differential diagnosis and diagnostic pitfalls of this disease. Material and methods: The involvement of
vertebral and extravertebral sites including the pelvis, calcaneum, ulnar olecranon, and patella is frequently found in the literature.
The lesions described are the anterior and lateral ossification of the spine, hyperostosis at sites of tendon and ligament insertion,
ligamentous ossification, and periarticular osteophytes. The criteria for the diagnosis of diffuse idiopathic skeletal hyperostosis
involving the spine are: flowing ossification along the anterior and anterolateral aspects of at least four contiguous vertebrae,
preserved intervertebral disc height, no bony ankylosis of the posterior spinal facet joints, and finally no erosion, sclerosis or bony
ankylosis of the sacroiliac joints. Results: The disease has about the same frequency in men (65%) and women (35%); it is most
common in the thoracic spine and occurs less frequently in the lumbar and cervical spine. The disease most commonly presents
in the sixth and seventh decades of life and its estimated frequency in the elderly is 5 – 15%. Signs and symptoms include stiffness
and pain in the back, dysphagia due to direct esophageal compression/distorsion, pain related to associated tendinitis, myelopathy
related to core compression associated to the ossification of the posterior longitudinal ligament, and pain related to vertebral
complications—e.g. fracture/subluxation. Conclusion: While conventional radiography clearly confirms the diagnosis of diffuse
idiopathic skeletal hyperostosis, CT and MRI better detect associated findings (e.g. ossification of the posterior longitudinal
ligament) and complications (e.g. spinal cord compressive myelomalacia). © 1998 Elsevier Science Ireland Ltd. All rights reserved.

Keywords: Diffuse idiopathic skeletal hypersostosis; Bone disorder; Joint disorder

1. Introduction hyperostosis, Forrestier, Rotes-Querol and Ott’s disease

and dysmetabolic hyperostosing spondylopathy [2–4].
Diffuse idiopathic skeletal hyperostosis or dys- No specific marker has been found in the HLA
metabolic hyperostosing polyenthesopathy is a degener- system to date, but the disease aggregates in certain
ative disorder of unknown cause affecting mostly older families. It is often associated with type II diabetes and
subjects (48–85 years old) and men (65%) more than android or sthenic obesity, which is in turn correlated
women [1]. not only with diabetes, but also with biliary stones,
In English-speaking countries this disorder is usually atheromatous vascular disorders, systemic hypertension
known as DISH, the acronym for diffuse idiopathic and other diseases of lipid and purine metabolism [5].
skeletal hyperostosis; in Italy the abbreviation PID Physiopathologically DISH is characterized by a ten-
(polientosopatia iperostosante dismetabolica) is pre- dency to ossification of ligamentous insertions (fibro-
ferred. Other, less frequent, synonyms are Wenzel and osteosis) and ossification and/or calcification of
Rokitanski’s zuckergusswirbelsaule (frosted spine), se- tendons, ligaments and fasciae in both the axial and the
nile ankylosing vertebral hyperostosis, coating vertebral appendicular skeleton.
The degenerative changes originate in cartilaginous
* Corresponding author: Tel. + 39 882 410264; fax: + 39 882 tissue: blood vessels from the subchondral bone mar-
411705. row invade the cartilage while pluripotential connective

0720-048X/98/$19.00 © 1998 Elsevier Science Ireland Ltd. All rights reserved.

PII S0720-048X(98)00036-9
S8 M. Cammisa et al. / European Journal of Radiology 27 (1998) S7– S11

Table 1 2.1. Type I

Causes of bone overproduction in the axial skeleton

DISH Ligament involvement, particularly the anterior lon-

Spondylosis gitudinal ligament which becomes irregularly calcified.
Seronegative spondyloarthritis Only the deep part of the ligament remains unaltered
Acromegaly and appears, radiologically, as a thin radiotransparent
Fluorosis
band between the calcified ligament and the anterior
Ochronosis
Neuroarthropathies vertebral body wall.
Trauma
2.2. Type II

tissue cells react by differentiating into osteoblasts. The Lesions are mainly peripheral to the annulus fibrosus
result is osteoproductive fibro-osteogenic changes which and the intervertebral disk. The disk progressively pro-
can take various forms: outgrowths, protuberances, trudes anteriorly and stretches the anterior longitudinal
needle-shaped, spur-like. These reactions are particu- ligament: anterolateral gross calcifications known as
larly important when associated with an ‘osteoblastic enthesophytes or pseudosyndesmophytes are found in
diathesis’, as in DISH, pachydermoperiostosis and a the sites of ligament enthesis.
few other diseases (Table 1). Three radiologic diagnostic criteria are used to assess
Some patients with DISH are asymptomatic but oth- vertebral column involvement and to grade the disease
ers have acute or subacute episodes of ‘periarthritis’ [11–13]:
probably due to phases of activation of the entheso- 1. Rheostotic calcifications closely adherent to the
pathic process, e.g. ‘trochanteritic’, ‘epicondylitic’, anterolateral margins of at least two contiguous
‘epitrochleitic’, ‘shoulder and/or hip periarthritic’ pain. vertebral bodies, with or without associated
Some patients complain of severe symptoms although osteophytes.
there are no objective findings, while others have really 2. Relative sparing of the width of the intervertebral
quite marked functional joint deficit (for example of the disk in the involved segments and no disk
elbow or the cervical spine) with no major subjective degeneration.
signs [6,7]. 3. No bony ankylosis of the interapophyseal joints.
The most common symptoms associated with DISH The distinctive signs of DISH are the so-called ‘pseu-
involved with the spine are rigidity, decreased mobility, dosyndesmophytes’ or ‘hyperostotic spondylophytes’
spinal column pain and dysphagia from esophageal which tend to fuse forming bony bridges [14]. These are
compression. In some, not uncommon and sometimes the consequence of enthesopathies and ossifying perios-
episodic, cases there are symptoms due to irritation toses at the insertions of the anterior longitudinal liga-
(and much more rarely, compression) of nerve roots in ment into the vertebral bodies.
the conjugate vertebral foramina. Spinal cord disorders, A less characteristic feature is the presence of macro-
although even rarer, are also possible [8 – 10]. osteophytes of deforming spondylosis. The so-called
These neurological syndromes are due to obstruction ‘drop ossifications’ are more typical. These ossifications
produced by newly formed bone arising from interapo- often occur in the middle of the disk space, anteriorly
physeal and unco-vertebral joints and ossification of or laterally, sometimes in contact with the margins of
parts of the posterior longitudinal ligament or the the vertebral body—in which case the term ‘gutta
ligamenta flava. cadens’ sign can be used. ‘Bony bridges’ or ‘bony
Radiology demonstrates the degree and extent of the coating’ are seen anteriorly and/or laterally to the verte-
enthesopathic ossification underlying the disease: bral bodies in more advanced disease stages. The entire
changes can be seen in the joints themselves, in peri- spinal column can be involved, even the first two cervi-
and para-articular structures, and in both the cal vertebrae, but the disease is more common and
mesomelic and the rhizomelic skeleton. However, al- more obvious in the middle-low cervical spine and the
though radiologic signs can be found in numerous middle-low thoracic spine. Thoracic spine involvement
peripheral joints, diagnostic certainty is reached from is characteristic, occurring in 95% of patients. Here the
the findings in the spine. hyperostosis is predominantly on the right of the verte-
bral bodies: the aorta pulsation tends to inhibit the
development of osseocalcified formations on the other
side. The whole border of the thoracic spine can be
2. The spine encircled by arches of bony tissue, up to a centimeter
thick, giving a moniliform or scalloped appearance to
Two types of anatomopathologic changes can be the thoracic spine. Lumbar spine neoformations are
found in the axial skeleton: usually more focal, although they may be gross, with
 M. Cammisa et al. / European Journal of Radiology 27 (1998) S7– S11 S9

Table 2
Distinctive signs of DISH

1. Vertebral bodies: exuberant paravertebral ossifications;

Large osteophytes
Bone ankylosis
2. Intervertebral disks: normal or slightly reduced height
3. Interapophyseal joints: normal or slightly sclerotic
4. Sacroiliac joints: para-articular osteophytes
5. Peripheral skeleton: para-articular osteophytosis
‘Whiskering’
Calcification and/or ossification of ligaments
Hyperostosis

the body wall (Fig. 2). Furthermore, in the posterior

region of the vertebral bodies, the calcified insertions of
the posterior longitudinal ligament and the ligamenta
flava can be seen; these are possible causes of stenosis
of the spinal canal and/or conjugate foramina [8,15,16].
The bony coating, in addition, can become spongy,
Fig. 1. Diffuse idiopathic skeletal hyperostosis; cervical paravertebral with formation of medullary bone; this is easily de-
ossification which extends over several metameres. The disk space is picted with magnetic resonance imaging.
relatively well preserved. The radiotransparent bands corresponding The differential diagnoses of DISH are those of
to the disk space and between the bony coating and the anterior any other conditions causing overproduction of axial
margin of the vertebrae are important diagnostic indicators of this
disease. skeletal bone [7,17,18]; degenerative spondylosis,
seronegative spondyloarthritides, acromegaly, hyper-
‘parrot beak’ and ‘candle flame’ shaped spondylo- parathyroidism, fluorosis, ochronosis and neu-
phytes. Other sites of new bone formation are the roarthropathies (Table 3). The different features of the
costovertebral joints and the insertions of the primary bony lesion of each of the above diseases in
supraspinal and interspinal ligaments giving appear- association with the specific clinical and laboratory
ances similar to those seen in Baastrup’s disease. findings usually allow the correct diagnosis to be made
Radiographically, the apparently mild involvement without undue difficulty.
of the intervertebral disk is important: in fact, although
the insertions of the peripheral fibers of the annulus are
affected early in the disease, the intervertebral space
remains physiologically wide for a long time, thus
helping to distinguish DISH from vertebral spondylosis
and osteochondrosis. When a bone coating forms, the
‘double anterior margin’ sign may be seen along the
whole spine because a radiotransparent space represent-
ing the deep portion of the not yet completely ossified
anterior longitudinal ligament may appear between the
anterior (or lateral) margins of the vertebral bodies and
the enthesopathic ossifications (Fig. 1). Anatomopatho-
logically, radiotransparent areas at the intervertebral
disk are herniated non-calcified disk material (Table 2).
Osteoporosis signs are not constant and indeed may be
absent even in elderly subjects.
Computed tomography (CT) easily shows the charac-
teristic changes in the hyperostotic spine. The involve-
ment of interapophyseal and sacroiliac joints is
Fig. 2. Diffuse idiopathic skeletal hyperostosis; CT shows involve-
particularly clearly depicted as are calcified deposits in ment of interapophyseal joints and calcified deposits in the anterior
the anterior longitudinal ligament and the related ra- longitudinal ligament, with a related radiotransparent band between
diotransparent band between the calcified ligament and the calcified ligament and the body wall.
S10 M. Cammisa et al. / European Journal of Radiology 27 (1998) S7– S11

Table 3
DISH

A. Idiopathic DISH
B. Secondary DISH due to:
Urate depositing diseases
Pyrophosphate depositing diseases
Hydroxyapatite depositing diseases
Ochronosis
Acromegaly
Other diseases

3. Extra-axial manifestations

Signs of hyperostosing and ossifying enthesopathies

may be present in any joint, besides those of the spine.
They are particularly frequent in the pelvis where signs
of enthesopathy can be seen along the margin of the
iliac wing between the two anterior spines, at the inser-
tions of the iliotransverse, iliolumbar and sacrotuberous
ligaments (Fig. 3). A ‘hairy’ appearance of the ramus of
the ischium is found less frequently than in seronegative
spondyloarthritis. In the sacroiliac joints roundish
dense areas (like Dihlmann’s ‘circumscribed sacroiliitis’)
may occur associated with ossification of the fibrous
Fig. 4. Diffuse idiopathic skeletal hyperostosis; gross supra-acetabu-
areas of the joint capsule. These can be well docu- lar enthesophytes are demonstrated.
mented by axial projections [12,18,19]. Other sites com-
monly involved by the enthesopathy are the 1. the structure of the joint examined, remembering
coxofemoral joints, the patella, the calcaneus and the the possibility of intra-articular, but extrasynovial,
olecranon where characteristic bony spurs are fre- entheses such as that of the long head of biceps, at
quently found [4,20,21]. Furthermore, heterotopic os- the shoulder or of the cruciate ligaments of the
sifications, secondary to surgical operations, can be knee, and that some ligaments insert into the oppo-
important in DISH patients. site aspects of some joints;
Identifying the enthesopathies by radiologic imaging 2. the direction of the bundles of fibers which make up
is not difficult if three fundamental notions are kept in the ligament or the muscle tendon; in fact, newly
consideration: formed bone, visible radiographically, slowly length-
ens in that direction, according to the traction forces
exerted on the fibrous structure under consideration;
3. that the fibrocartilaginous elements of joints may
also become ossified in DISH (disks, pads of the
iliac acetabulum or of the glenoid scapular, etc.)
(Fig. 4).
The diagnosis is based essentially on diagnostic imag-
ing or radiologic findings, since information from the
clinical history is sparse and some clinical findings are
not well known such as unnoticed loss of joint mobility,
the ‘hard, bumpy knee’, the ‘hairy foot with dorsal
nodes’, etc. [18,22–27].
Finally, CT has been shown to be an excellent
method for establishing whether or not there is an
inflammatory component to the entheses; the changes
which can be noted are areas of focal bone rarefaction
with or without associated osteoproductive reaction.
Fig. 3. Diffuse idiopathic skeletal hyperostosis; calcification of the CT examination is fairly easy at the insertion of
iliolumbar ligaments. Achilles tendon: one is often surprised to find that the
 M. Cammisa et al. / European Journal of Radiology 27 (1998) S7– S11 S11

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