CASE REPORT

Osteochondritis
dissecans in
adolescence

R de Villiers
MBChB (Ste/l), MMed (RadDiag) (Ste/l)

Radl%gy Practice: Van Wageningen and Partners
Med/-C/inic Verge/egen

Main Road, Somerset West, 7130
Tel: (021) 851-5595. Fax (021) 852-2697

Abstract
Osteochondritis
dissecans (00)
involves the adolescent
radio-capitellar joint
and is due to chronic,
compressive forces on
the capitellum,
ultimately causing
injuries ranging from an
articular cartilage injury
to an osteochondral
avulsion fracture. Plain
fi Ims are often negative,
while CT, MRI and MR
arthrography are the
examinations of choice.
00 should not be
confused with a
pseudodefect of the
capitellum or Panner's
disease. Staging of the
lesion is important for
its management, which
is conservative for
stages 1 and 2, while
surgery is indicated for
stages 3 and 4.
Osteoarthritis is a late
complication in 500/0 of
patients with advanced
disease.

36 SA JOURNAL OF RADIOLOGY- February 2001

Case report
A lS-year-old elite downhill

mountain-biker presented with a
painful elbow after falling off his bike
on a descent. On clinical examination
he had a suspected fracture of the
capitellum with associated soft tissue
swelling. There was also limited range
of movement, but no crepitus was
present. On further questioning, there
was a history of a few minor falls and
intermittent pain.

Plain films show defect of the lat-
eral aspect of the capitellum (Figure 1).

Figure 1: AP plain radiograph of the left elbow
showing 8 defect in the capitellum (arrowheads)

Axial CT showed a deep defect of
the capitellum and loose bodies in the
coronoid and olecranon fossae (Figure
2). MRI T2 fat saturation (Figure 3a)
and Tl coronal images (Figure 3b)
showed the capitellar defect with fluid
partially surrounding the fragment, as
well as associated rnicrotrabecular bone
marrow oedema.

The clinician decided to treat the
patient conservatively, as it was felt
that the elbow is a non-weight-bear-

topage37



Osteochondritis dissecans
in adolescence

frompage36

ing joint. Rest was
advised and fur-
ther weight-bear-
ing and com-
pressive trauma
to the elbow
discouraged.

Discussion
Repeated val-

gus stress produc-
ing lateral com-
partment com-
pression may lead
to osteochondritis
dissecans of the
capitellum 1• Os-

teochondritis dissecans repre-
sents a trans chondral fracture
secondary to a transmission of
tangential shearing forces across
the joint space. The stress com-
presses the bone and may result
in a spectrum of injury ranging
from articular cartilage injury to
an osteochondral avulsion frac-
ture. This injury is thought to be
traumatic in origin, owing to ei-
ther a single major event or re-
peated minor injuries." Abnor-
mal stress owing to
malalignment or ligamentous
laxity may be a predisposing fac-
tor. Other proposed causes in-
clude a hereditary ossification
defect, familial localised abnor-
mality in cartilage nutrition, or
micro emboli with peripheral
necrosis of bone. The age range
is four to 15 years, but patients
are predominantly within the
second decade oflife, Most chil-
dren with this condition are ac-
tive. Boys are three times more
likely to have this entity than
girls. The knee, elbow and talus
are the most common sites in-

Figure 2: Axial CT of the left elbow viewed from the eraniad aspect.
Arrowheads Indicate both the site of the capitellar defect and the loose
bodies in the olecranon fossa.

(b) T1 coronal MRI of the left elbow. Both images show
the capitellar defect (arrowheads), with joint fluid
axtending Into the lesion.

37 SA JOURNAL OF RADIOLOGY- February 2001

volved. Gymnasts, pitchers and down-
hill mountain-bikers are predisposed
to 0 D of the capitellum or radial head
due to chronic lateral impaction.'

Plain films may show a fracture
line, a fragment with a surrounding
lucent zone or a concave defect. The
fragment may be dense, suggesting
necrosis, or may resorb.l+' An antero-
posterior plain film of the elbow with
45% flexion is also suggested to show
the pathological process. S The use of
ultrasound is also suggested by certain
authors. Localised subchondral bone
flattening with overlying cartilaginous
thickening is seen in early disease.S CT,
MRT and MR arthrography are used
to diagnose and stage osteochondri-
tis, as the staging affects the manage-
ment.1,2,4

It is important to stress that dif-
ferent classifications for OD exist for
the elbow and the talus. This often
leads to confusion.'>

MRT Stage 1 OD of the elbow
demonstrates signal changes consist-
ent with cartilage injury, without dis-
ruption, and a normal subchondral
bone. Stage 2 shows high signal breach
of articular cartilage, but with a sta-
ble subchondral fragment. Stage 3
demonstrates a partial chondral at-
tachment associated with a thin bright
T2 signal behind the osteochondral
fragment, probably representing syno-
vial fluid around the fragment. Stage
4 represents a loose body within the
centre of the osteochondral bed or
free in the joint space.2,s

Care should be taken not to con-
fuse an osteochondral defect of the
elbow with the pseudodefect on MRI,
owing to the abrupt transition be-
tween the posterolateral margin of the
capitellum and the non-articular por-
tion of the lateral humeral condyle.'

topage38



Crstecictioridritis dissecans
in adolescence

frompage37

Osteochondritis dissecans should
also be distinguished from osteochon-
drosis of the capitellum, which is
known as Panner's disease. Age is an
important discriminator, because
Panner's disease typically occurs in
children five to Il years of age, com-
pared with the 13 to 16 years of age
for OD. Panner's disease is thought
to represent avascular necrosis of the
capitellar ossification centre that oc-
curs secondary to trauma. Plain films
may show subtle fragmentation, while
MRI shows abnormally decreased sig-
nal intensity within the ossifying
capitellar epiphysis. Subsequent scans
reveal normalisation of these changes
with little or no residual deformity of
the capitellar articular surface.'

Conservative treatment is indicated
for stages 1 and 2, as the bone fragment
may revascularise and heal. Surgery is
indicated for stages 3 and 4, where the

bone fragment is either fixed to the
parent bone or removed and the
osteochondral crater debrided or fixed.
Osteoarthritis develops in 50% of
patients with OD of the elbow.1,2,4

Conclusion
Osteochondritis dissecans of the el-

bow is a post-traumatic injury to the
radio-capitellar joint caused by either a
single major traumatic event or chronic
lateral compressive forces. Plain film
findings (in contrast to the index case)
are usually negative, while CT and MR!
show the different stages of the patho-
logical process optimally. The diagnosis
and staging are important, as the man-
agement and long-term prognosis are
dependent on accurate imaging.
Aknowledgement

I would like to thank Dr Andy du
Toit for help regarding the subject
matter in this paper.

Allied Health/Clinical Su ort
Radiologists
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38 SAJOURNAL OF RADIOLOGY. February 2001

References
1. Anderson IF, Read J, Sternweg 1. Atlas of

imaging in sports medicine. Sydney: McGraw-
Hill Companies, Inc. 1998.

2. Fritz Re. MRI of sports injuries of the elbow.
MRT Clinics of North America 1999; 7: 51-
69.

3. Beltran J, Rosenburg ZS. MRI of paediatric
elbow fractures. MRI Clinics of North
America 1997; 5: 575-577.

4. Fritz Re.MRI of osteochondral and articular
lesions. MRI Clinics of North America 1997;
5: 586-593.

5. Takahara M, Ogino T, et al. Natural
progression of osteochondritis dissecans of the
humeral capitellum: Initial observations.
Radiology 2000; 216: 207-212.

frompage30

Free intraperitonea I
air on paediatric
plain radiographs
and differentiating
this from a 'food
mound"

in the gastric fundus accumulates in a
mound instead of as the expected air-
fluid level. When faced with a surgeon
concerned about this finding, re-evalu-
ation of the patient's clinical status is
recommended together with re-assess-
ment of the radiographs for free air in
other recognised locations.We also keep
examples of previous normal patients
with the "food mound" sign, which we
show to doubtful surgeons.

If the radiologist is familiar with this
finding, such a radiograph will cause less
distress to him/herself the surgeon and
the parents of the recently fed child. May
the "food mound" be with youl

References
I. Parker BR. The abdomen and gastrointestinal

tract: The peritoneal cavity. In: Silverman FN,
Kuhn JP (eds). Caffey's paediatric X-ray diagnosis.
9th ed. St. Louis: Mosby. 1993: 906-909.

2. Buonomo C,Taylor GA, Share JC, Kirks DR. The
gastrointestinal tract. In: Kirks DR. Practical
paediatric imaging. 2nd ed. Philadelphia:
Lippencott-Raven. 1998: 828-829, 890-895.

mailto:andrew_cumming@health.qld.gov.au