Unicameral Bone Cyst with Epiphyseal Involvement

Journal of Pediatric Orthopedics
2:71-79 © 1982Raven Press, New York
Unicameral Bone Cyst with Epiphyseal Involvement:
Clinicoanatomic Analysis
*Martin M. Malawer
Departments
and tBruce
Markle
of "'Orthopedic Surgery and tRadiology,
Children's Hospital National Medical
WashingfOl7 University School of Medicine,
washington,
D.C.
Center and George
Summary:
Epiphyseal involvement of a unicameral bone cyst (UBC) is rare.
This anatomic setting represents a distinct clinical and radiographic entity. This
study reports a new case and analyzes the clinical and biological behavior of
seven additional UBCs with epiphyseal involvement
from the literature.
We
report the first successful treatment of this variant with methylprednisolone
acetate. The average age was 20.1 years with a male to female ratio of 1.3: 1.
Anatomic location: proximal femur (4), proximal humerus (2), and proximal
tibia (2). Both age and location were atypical when compared to the classic
metaphyseal
location. Radiographically,
all lesions presented a characteristic
involvement
of the epiphysis
and metaphysis
in various proportions.
The
epiphyseal
plates were judged closed versus open in 50%, respectively.
Follow-up ranged from 9 months to 3 years. Six cases healed following a single
curettage (three with and three without bone graft). There were no late complication
of fracture, deformity, shortening,
or avascular necrosis. Recurrence
was 0%. No secondary procedures
were required. We conclude the age, location, and radiographic appearance
is atypical and diagnosis is difficult, but the
biological behavior is less agressive and the prognosis more favorable than the
typical, metaphyseal
UBC. Curettage with or without bone graft has a high
success rate. We recommend aspiration and intralesional
methylprednisolone
as the initial management.
We hypothesize that epiphyseal UBCs have a better
prognosis than metaphyseal
location alone due to the older age, atypical location, and the potential of the epiphysis to reossify. Key Words: EpiphysisUnicameral
bone cyst-Methylprednisolone
acetate-Proximal
humerusProximal femur-Benign
bone tumor (childhood).
Unicameral bone cyst (UBC) is a benign lesion
found in the long tubular bones of children and adolescents. Classically,
they originate in the
metaphysis, abut the growth plate, and later may
involve the diaphysis. This results from the continued longitudinal bone growth of the epiphysis
beyond the site ofthe cyst (11). UBCs rarely involve
the epiphysis. Jaffee first decribed UBC, noting a
single example of epiphyseal involvement in a 42year-old man (11). Cohn reported three cases of
UBC that had evidence of penetration of the physis
at surgery (6). Other reports of epiphyseal involvement by UBC, including treatment and results, have
been described (2,3,7,10,18,22). We have recently
treated a solitary bone cyst with extensive epiphyseal involvement in the proximal femur of a 14year-old boy. Treatment consisted of biopsy, aspiration, and injection of methylprednisolone acetate.
Curettage or bone grafting was not performed. The
purpose of this paper is to report this case and to
review the literature.
A review of the literature has revealed a total of
Dr. Malawer is Consultant at the Surgery Branch, National
Cancer Institute, N.I.H., Bethesda, Maryland.
Address correspondence and reprint requests to Dr. MaJawer
at Department of Orthopedics/Oncology
Section, Children's
Hospital National Medical Center, III Michigan Avenue,
.W.,
Washington, D.C. 20010.
71
72
M. M. MALAWER
AND
seven cases of UBC with epiphyseal involvement
(Table I) (2,3,7,10,11,18,22).
All of these reports
have been of isolated cases (1942-1980).
To our
knowledge, this study is the first report to analyze
the overall manifestation
and behavior of unicameral bone cysts with epiphyseal involvement (EUBC).
This paper presents a retrospective
analysis of the
above cases in order to answer the following questions:
I. What are the clinical and radiographic
characteristics of UBCs with epiphyseal extension?
2. What is the clinical significance (biological behavior) regarding growth disturbance,
deformity,
recurrence,
and avascular necrosis?
3. What is the appropriate
clinical management
of this rare variant?
CASE REPORT
A 14-year-old
male complained
of exerciserelated pain in the right hip for 3 months not responsive to salicylates. There were no other musculoskeletal
or constitutional
complaints.
There
were no cutaneous abnormalities.
Physical examination showed that both legs were of equal leg
lengths without atrophy. The gait was normal; the
Trendelenburg
test was negative.
The range of
internal and external rotation on the right hip was
limited by 30°. The remainder
of the musculoskeletal
examination
was normal.
Laboratory
TABLE 1. Epiphvse al unicamera!
Reference
II
42/M
10
6.5/F
221F
22
18
Malawer
Markley
and
(1982)
Distal
femur
Proximal
tibia
Proximal
femur
Radiographs of the right hip (Fig. l) demonstrated
an extensive radiolucent defect of the femoral neck
and capital femoral epiphysis, partly circumscribed
by a narrow margin of sclerosis. The cortex showed
thinning but no expansion,
cortical breakthrough,
periosteal reaction or fracture. The femoral neck
was of normal length without
deformity.
The
acetabulum,
pelvis, and joint space were normal.
A 99'J'c-MDP bone scan (Fig. 2) revealed no increased uptake in the lesion, but a subtle decrease
in the femoral neck. There was normal activity in
the growth plates (signifying an open, active growth
plate) without evidence or hyperemia or soft tissue
extension.
Computed tomography (Fig. 3) showed a lucent,
nonexpansile
lesion of the femoral head and neck
without extraosseous
extension or matrix formation, with an internal absorption coefficient of fluid.
The combined
radiographic
studies suggested
a
nonagressive
lesion. The preoperative
differential
diagnoses included atypical UBC, atypical chondroblastoma,
giant cell tumor, unusual aneurysmal
bone cyst, or eosinophilic granuloma.
bone
C.I'SI:
Status of
plate
literature
Rx
review
Status
Comment
Closed
Curettage:
bone graft
Healed 3 years,
FROM"
Closed
Curettage:
no graft
Healed
no Fx·
18 rnos,
9 mos,
Metaphyseal!
epiphyseal
No shortening,
no deformity
Open
Curettage:
bone graft
Proximal humerus
(entire VI)
Metaphyseal!
epiphyseal
Closed
(tomograms)
Curettage:
no graft
FROM
healed
241M
Proximal
humerus
Metaphyseall
epiphyseal
Closed
Curettage;
no graft
Healed (80%),
2 years
171M
Proximal
femur
Epiphyseal
Open
Curettage;
bone graft
Healing 6 mos,
asymptomatic
Initially presented
with articular collapse and
early degenerative
change
141M
Proximal
femur
Metaphyseal!
epiphyseal
Open
Intralesional
methylprednisolone
alone; no curettage
or graft
FROM
healed (80%)
2 years
Pressure,
(pulsatile)
FROM. full range of motion.
• Fx. fracture.
Orthop,
Radiographic Evaluation
MetaphyseaJ/
epiphyseal
a
J Pe-Iiatr
studies, including CBC, serum electrolytes,
calcium
phosphorus,
and serum alkaline phosphatase
were
within normal limits.
Proximal tibial
(entire ~)
15.3/F
7
Location
Age/sex
Relationship
to epiphyseal
plate
B. MARKLE
v'ol. 2. No.
I. /982
2 em shortening
16 em H20
UNICAMERAL
BONE
CYST
WITH EPIPHYSEAL
INVOLVEMENT
73
,B
FIG. 1. Initial anteroposterior (A) and
lateral (B) radiographs demonstrate an
extensive, well marginated, lytic defect of the femoral head and neck.
The cortices of the femoral neck are
thinned. The joint space and acetabulum are normal. The overall shape and
size of the femoral head are normal.
There is no pathological fracture. Note
the extensive metaphyseal and epiphyseal involvement without deformity.
Operative
Procedure
and Histology
The femoral neck was approached through an
anterolateral incision. An I8-gauge needle was inserted into the lesion, and clear, yellow fluid was
aspirated. Manometric measurements showed 16
cm H20 pressure. Pulsation of the column synchronized with the patient's pulse. A Valsalva maneuver was performed, and a direct variation of the
pressure was noted. Biopsy of the wall through a
limited 0.5 x 0.5 em window in the anterior cortex
confirmed a cystic cavity with no underlying primary neoplasm.
Histologically, the lining showed islands of acellular eosinophilic material, interspersed by a thin
fibrous stroma containing a few vessels (Fig. 4).
There were no giant cells, histiocytes, or hernosid-
R
FIG. 2. Coned down, pinhole collimator views of 99mTc-MDP
bone scan of the hips, in frontal projection, show normal
linear areas of increased activity at the open growth plates
of the femoral heads (straight arrow). greater trochanters
(small arrowhead), and at the triradiate cartilates (large
arrowhead). Despite the uncertain status of the growth plate
by radiography, this scan demonstrates an active physeal
mechanism within the lesion. Note the subtle photon deficient area of the right femoral neck corresponding to the cyst
(curved arrow).
erin. The clinical and histological diagnosis of UBC
was based on the finding of a cavity containing yellow fluid lined by a thin fibrous membrane. Curettage and bone graft were not performed. Methylprednisolone acetate, 240 mg, was instilled under
direct vision via the cortical window, and the
wound was closed. The dose was determined by the
amount required to fill the cyst cavity.
RESULTS AND FOLLOW-UP
Postoperatively,
the patient was maintained
nonweight bearing for 6 weeks. Full weight bearing
was begun at 2 months. Twenty-four months following surgery, he was fully ambulatory and participating in all activity. Examination of the hip
showed a full range of motion and a normal gait.
Radiographic
Evaluation
Radiographs
were obtained at 2 months, 6
months, 8 months, 12 months (Fig. 5), and 18
months (Fig. 6) after surgery. Serial radiographs
showed rapid thickening of the bony cortex and
secondarily progressive centripedal ossification.
Heterotopic bone formation in the abductor muscles was noted and considered secondary to the
surgery. Twelve months after surgery, 80% of the
defect had reossified. There was complete reossification of the epiphysis and remodeling of the calcar,
with premature obliteration of the epiphyseal plate
and subsequent femoral neck shortening (decrease
articular trochanteric distance) but without deformity or avascular necrosis and with maintenance of
a normal joint space (Fig. 6A).
.I Pediatr
Orthop , Vol. 2, No.
I, 1982
M. M. MALA WER AND B. MARKLE
74
3A,8
FIG. 3. Computed tomography scans at the level of the capital epiphysis (A) and at the level of the femoral neck (8). Apart from a
solitary central calcification, no osseous or cartilaginous matrix is present. There is no soft tissue mass. The cortex of the femur
is thinned but intact. The joint space and acetabulum are normal. Note the surrounding zone of reactive sclerosis indicating a
benign lesion.
Comment
In planning the treatment of this lesion, the
preoperative radiographic evaluation was important
in demonstrating the limits of the lesion and its
,
•
--
,
,
#
...
,
nonaggressive character. The unusual, extensive
involvement of the epiphysis made a specific diagnosis difficult, even though many of the lesion's
characteristics suggested a bone cyst. Additional
possible diagnoses included chondroblastoma, giant
cell tumor, eosinophilic granuloma, aneurysmal
bone cysts, or a well healed infection (21). The
"cold" character on radionuclide bone scan argued
against fibrous dysplasia (9). An intraosseous
lipoma should have shown a typical low attenuation
value by computed tomography. A bone cyst was
ultimately diagnosed by the finding of a cystic cavity, containing clear yellow fluid, and Linedby a thin
fibrous membrane.
CLINICOANATOMIC
LITERATURE
ANALYSIS
REVIEW
AND
fit
I
I
I
,
.
-,
An extensive review of the literature noted seven
cases in addition to the present case of UBC with
epiphyseal involvement (Table 1). We analyzed the
age, sex, location, treatment, rate of recurrence,
and deformity in order to determine the clinical
behavior and the appropriate management of thi
variant.
Age and Sex Distribution
FIG. 4. Histologic section of the bone cyst lining shows an
amorphous, eosinophilic extracellular material and a cellular
component composed of mature fibrocytes. No osseous or
cartilaginous matrix is present. There is no evidence of giant
cells, chondroblasts, or inflammation.
J Pediatr
Or/hop,
Vol. 2. No.
I, 1982
Age at the time of diagnosis ranged from 6.5 to 42
years with an average of 20.1 years. Males outnumbered females 4:3. The average age was notably
higher than those reported of classic metaphy eal
lesions (1,2,4,10,14-16,19).
UNICAMERAL
BONE CYST WITH EPIPHYSEAL
Location of Lesion
There were four (50%) femoral, two (25%) proximal humeral, and two (25%) proximal tibial lesions.
This is an unusual distribution. Neer reported a reverse ration of 2: 1, proximal humerus:proximal
femur, in a review of250 simple bone cysts (17). He
found the tibia to be a rare site (less than 4%). Two
of eight cases of EUBCs involved the tibia.
Radiological
Relationship
and Status of Physis
All lesions (except Case 7) involved the metaphysis and epiphysis. The degree of involvement varied
from predominantly metaphyseal to equivalent degrees of epiphyseal and metaphyseal involvement.
Four of the seven cases (Cases 1,3,5, and 6) were
in older individuals whose epiphyseal plates were
closed. Three reported cases (Cases 2, 4, and 7) in
addition to our case (Case 8) had an open physis. In
one case, the epiphyseal plate was obliterated by
the lesion and the effects of old trauma.
Treatment
and Results
Follow-up ranged from 9 months to 3 years. Results of the earliest case (Case I) were not reported.
Six of the remaining cases reviewed were treated
with curettage, three with and three without bone
grafting. All lesions healed. Bone grafting did not
offer any apparent advantage. There were no differences between those with open or closed epiphyses
regarding final outcome, irrespective of treatment.
There were no recurrences, late fractures, deformity, avascu lar necrosis, or secondary procedures
required. No patient developed leg-length discrepancy. Humeral shortening in Case 5 was attributed
to old trauma. Case 7, a femoral head lesion, presenting with subarticular collapse and early degenerative changes, was cured with curettage and
bone graft. This was the only case of articular collapse. Thus, open epiphyseal plates did not appear
to increase the incidence of late complications.
DISCUSSION
Unicameral bone cysts are classically metaphy eal and adjacent to the physis in origin but may
later involve the diaphysis. Seventy percent will
remain juxta-epiphyseal
(17). The epiphysis is
rarely involved. This study reports one new case of
INVOLVEMENT
75
a UBC with epiphyseal involvement and retrospectively analyzed seven cases from the literature.
Clinical Considerations
The average age of patients with UBC in tubular
bones is 9 to 15 years (1,3,4,10,14,16,19,20) with a
male to female ratio of2 to 3: 1. In the present series,
the average was older, 20 years, and the male to female ratio was decreased to 1.3: 1. The proximal
humerus and proximal femur (2: 1) are the most
common sites representing 75% of most large series. In
contrast, the present series showed four femoral
and two proximal humeral lesions, a reverse of the
expected ratio. In addition, two patients (Cases 3
and 4) had proximal tibia lesions, whereas tibial lesions were much less common in other series. Neer
noted that less frequent locations were characteristically found in adults (19). Boeseker et al. found
no proximal tibia lesion in 145 simple UBC reviewed
(3). He noted only one UBC with epiphyseal involvement in a review of the 145 UBCs seen at the Mayo
Clinic during a 47 year period. Therefore, we concluded that the age, sex, and anatomic location of
EUBCs are atypical and do not lead to a correct
diagnosis from clinical or radiographic criteria alone.
Surgery is necessary to establish the correct diagnosis. Aspiration is a simple diagnostic technique.
Biological Activity and Hemodynamic
Considerations
Biological and hemodynamic correlates of "activity" in addition to radiological location have been
described by Enneking (8) (1977). Latent cysts were
characterized by a pressure on manometric measurement equal to venous pressure (6-10 cm H20)
with a nonpulsatile column. Our hemodynamic
measurements correspond to an active cyst (16 em
H20 and pulsatile). This is the first reported pressure determination of a EUBC. Cohen (6) (1977)
briefly reported three proximal femoral lesions with
apparent perforation of the physis at surgery, but no
further clinical or hemodynamic data were given.
While one can speculate that increased cyst pressure may cause local erosion of the epiphyseal plate
with subsequent epiphyseal extension, we suspect
this is not the main determinant, since most active
cysts (therefore increased pressure) (8) do not clinically involve the epiphysis. Epiphyseal involvement
has been postulated to result from trauma to the
J Pediatr Or/hop.
Vol. 2, No. I, /982
M. M. MALAWER
76
SA,B
SC,D
SE,F
J Pediatr Or/hop,
Vol. 2, No. /, /982
AND B. MARKLE
UNICAMERAL
BONE CYST WITH EPIPHYSEAL
lNVOLVEMENT
77
5G,H
FIG. 5. Serial postoperative radiographs at 2, 3, 6, and 10 months following cyst aspiration and steroid injection demonstrate the
pattern of centripedal reossification. The initial stage shows amorphous ossification, which faintly outlines the radiolucent cyst
lining (open arrow, 3 months). Progressive ossification of this matrix provides substantial thickening of the bony cortex in both
femoral neck and in the epiphysis (arrows). This continues centrally, slowly obliterating the cavity, i.e., endosteal new bone
formation and not central ossification of the lesion.
growth plate with secondary extension (18). This
cannot be substantiated
by this review. The pulsatile, elevated pressure measurement
we obtained
may suggest a vascular etiology. Previously venous
obstruction
had been proposed
by Cohen (5,6).
Johnson suggested an etiology related to a small
angiomyxofibrillar
lipoma (12).
Role of Methylprednisolone
Recurrence
following curettage
of UBC have
ranged from 17 to 50% (17). Specifically, UBCs of
the proximal femur are difficult to treat and often
result in growth disturbance
and pathologic fractures with subsequent
coxa vara and ischemic necrosis (J 3). Boeseker (1968) noted a 28% recurrence
rate of proximal femoral UBCs (3). Thus, we chose
to treat our patient with aspiration and methylprednisolone as described by Scaglietti et al, (19) in order
to avoid this anticipated high rate of morbidity and
recurrence.
Scaglietti et aJ. (1979) reported 72 bone cysts
treated by topical injection of methylprednisolone
(19). Seventy-two
percent of the lesions involved
6A,B
FIG. 6. Postoperative result at 18 months. Final
postoperative anteroposterior
(A) and lateral (B)
radiographs demonstrate a small residual central
radiolucency, but significant reconsitution of the
normal bony architecture
of the femoral head,
neck, and calcar has been achieved without deformity, shortening, or avascular necrosis. Note the
premature obliteration of the physis and the resultant decrease in articular trochanteric
distance
secondary to the healing (reossification)
of the
physis.
J Pediatr Orthop,
Vol. 2, No.1,
1982
M. M. MALA WER AND B. MARKLE
78
the humerus or proximal femur. Radiographic findings showed reconstitution
of the cortical bone of
the cyst wall (similar to our patient). Progressive
formation of new bone was noted at 6 months with
opacification of the cyst cavity. Complete obliteration of the cavity took 3 years. The epiphysis, unlike in our patient, usually continued normal growth,
and Scaglietti stressed that no damage to the epiphyseal cartilage resulted from injection of steroids.
We hypothesize the premature closure of the epiphyseal plate in the present case was due to the healing process, i.e., reossification
of the involved physis and epiphysis (Fig. 6).
Scaglietti
noted in all cases with a positive
radiological response that no fracture occurred. No
patient required surgical treatment. Our patient similarly showed a good response, with early thickening of the cortical walls and opacification
of the
cavity with resultant early ambulation and maintenance of a good range of motion (Fig. 5).
CONCLUSIONS
Unexpectedly,
all six reported cases in the present series healed with a single curettage (with or
without bone graft). More importantly,
there were
no late sequelae offracture,
deformity (except Case
7), or avascular necrosis. Joint destruction
and recurrence
was not a problem.
Interestingly,
the
status of the physis (open or closed) did not influence the final outcome.
EUBC is a rare lesion and may be difficult to
diagnose. The differential diagnosis should include
chondroblastoma,
giant cell tumor, eosinophilic
granuloma,
intraosseous
lipoma, and aneurysmal
bone cyst (21). We believe that the clinical behavior
of a EUBC is to heal with simple curettage. The
expected tendency for recurrence,
deformity, and
avascular necrosis is less than we anticipated.
We
hypothesize
that these lesions have a better prognosis than metaphyseal
location alone due to the
older age of these patients (a good prognosticator
in
simple UBC), their atypical locations, and the increased potential of the epiphysis to reossify. We
believe EUBCs represent a distinct clinicoanatomic
entity with a less aggressive behavior and a more
favorable prognosis than the classic, metaphyseal
UBC, although its etiology is unknown.
Further
hemodynamic
evaluation of both the metaphyseal
and epiphyseal variant is warranted and may elucidate an underlying mechanism of epiphyseal extenIOn.
SUMMARY
This paper reports a new case of a unicameral
bone cyst with epiphyseal involvement and reviews
seven cases from the literature.
The clinical and
biological behavior were analyzed.
1. An exact radiologic
diagnosis
is difficult.
Radiologic imaging aids by demonstrating
a nonaggressive, solitary osseous lesion confined to bone.
Aspiration is recommended
as a simple confirmatory diagnostic technique.
2. UBC (epiphyseal valiant) presents in an older
age group, often after epiphyseal closure, without
expansion or cortical destruction and involves both
the metaphysis and epiphysis.
3. These lesions are less aggressive
than the
metaphyseal UBC and can be expected to heal with
simple curettage, with or without bone graft.
4. There is a low morbidity following curettage.
Postoperative
fracture,
deformity,
and avascular
necrosis did not occur.
5. We recommend
intralesional
methylprednisolone acetate following aspiration with protective bracing as the initial management
and would
reserve curettage for recurrent lesions or for diagnosis when aspiration is nonconfirmatory.
Acknowledgment.
We wish to acknowledge the contribution of Karen Harris in preparation of the manuscript and Dr. Lee Haacker in patient contribution.
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