Abstract:
Background:Unicameral
bone cysts (UBC) are treated by several methods including
curettage and bone graft, multiple drilling, autogenous bone
marrow or corticosteroid injection into the bone cyst.UBC in
lower extremity due to weight bearing can be complicated by
pathologic fracture.
Aim:
The
aim of this study was to assess and comparison the results of
methyl prednisone injection in the UBC of the upper and lower
limbs bone cyst. And compare outcome.
Material
and methods: 30
patients (12 girls
18 boys) with age group of 4.5-19 years old (mean 11.9) were
treated by methylprednisolone injection into the bone cyst and
were followed for 26-48 months
(Average
32 months). Patients where evaluated by serial radiographs (AP
& lateral) at 2-3 months intervals.
Findings: UBC
was located in humerus (n=18), in proximal of femur (n=9) and
proximal of tibia (n=3). After
methyl prednisolone injection into the lesion between 1-3 times,
in 83 % of humerus
cases and 44% femoral and 100% tibia bone cysts
subsided and shrunk with increased bone density within 32 month.
Conclusion:Injection
of methylprednisolon into UBC is a simple therapeutic method
with a low rate of morbidity. The favorable results were seen
mostly in the UBC of the humerus and tibia a compared to the
femoral bone.
J.Orthopaedics 2008;5(1)e15
Keywords:
Unicameral
bone cyst, methyl .prednisolone
Introduction:
The
unicameral bone cyst is not a real neoplasm .It has been
described first by Virchow (1) and Bloodgood differentiated it
from other lytic bone lesions. (2) Jaffe and Lichtenstein gave
more detailed information about UBC. (3) UBC involves 30% of all
initial biopsies in bone tumors and is common in the first
decades of age especially between 4-10 years. The prevalence in
male is two folds that of female. (4)
This
lesion is principally related to metaphysic of long bones. The
common sites are humerus (50%), femur and distal and proximal
tibia. (18-27%) Rarely
this bone lesion is also seen in calcaneus fibula, ulna, radius
and talus and in older ages it can also develop within flat
bones such as pelvic and vertebra. (5)
This
simple cyst is categorized into active and non-active according
to distance to growth plate. Active cysts are less than 0.5-1cm
distance from growth plate and occur in younger ages.
The
definite cause for cyst development is not known. Mirra related
the cyst to trauma at the birth causing entrapment of synovial
tissue into bone during neonatal period. (5)
Cohen
et al believe that the cause is venous bone obstruction with
accumulation of serum-like fluid in cyst. (6).This fluid result
in cyst formation and may prevent union. Components such as
prostaglandin interlokin 1, lysosomal enzymes of cyst fluid play
a role in formation and nonamelioration of cyst. (7).
Other
possible causes are trauma (8), rapid bone turnover (9),
lymphatic blockage (10) or local growth disturbance with
fibrotic tissue formation. Patients with UBC often complain of
pain and limping. Pathologic fracture is the most common
presentation in children.
Radiographically bone cyst is seen as central lucency in medullary
shaft of long bones. Fracture
in the cyst is a pathognomonic sign (fallen fragment sign). (11)
Unicameral
bone cyst fractures easily which heals spontaneously in 5% of
cases.
Abrupt
treatment of fracture is necessary. More aggressive treatment is
required in children under 10 years due to possibility of
shortening by growth plate arrest and deformity (12).
Several
methods of treatment have been suggested with age being the
principal determining factor .Older patients have a better
outcome. Other factors include size and location of cyst.
The
final goal of treatment is bone formation in cyst to bear
imposed stress and halting bone destruction documented by
radiography. Esthetic look of bone is less important compared to
formation of a stable and functional bone structure.
Several
therapies have been used so far for unicameral bone cyst that
include bone curettage with cryotherapy (13); multiple drilling
of the wall cyst which has been associated with 12 % recurrence
(14) autogenic bone marrow injection into cyst (15);cyst
curettage and bone graft with or without internal fixation which
has been associated with 50 % recurrence. (16) And local
corticosteroid injection in bone cyst. (17)
Total
or subtotal resection of cyst with or without bone grafting is
an old method that is rarely used today. Recurrence has been
reported in all above methods. Similar success has been seen
with surgical approaches and corticosteroid injection which lead
to popularity of the latter method. Steroid injection has been
first described by Scaglietti et al in 1979 and claimed good
results in 90% of cases (17) while curettage plus Bone graft has
45% recurrence rate. (18) surgery may cause growth disturbances
while steroid injection neutralize
destructive factors in the cyst and result in bone
formation and along with low complication rate or scar
development and its simplicity makes it a more common method of
treatment.
Material and Methods :
30
patients (12 girls and 18 boys) with age group of 4.5-19 years
old
(Mean
11.9) were treated with methyl prednisolone injection into cyst
and were followed for 6-48 months (average 13.8
months).according to response. Patients where followed up by
serial radiographs (AP & lateral) at 2-3 months intervals.
The
time delay between previous pathologic fracture and first
injection was 1.5- 3 months (average 2.5 months).
8
patients had proximal femur cyst presented with limping and
pain. One patient with cyst in tibia presented with pain.
Pathologic fracture was the presentation in one femur cyst.
The
cysts of the femur less than one half of diameter included in
the study.
All
patients with cyst in the proximal humerus presented with
pathologic fracture.
Patients
were managed by primary casting. Patients were admitted after
union of fracture site under general anesthesia with balanced
technique patients were prepped and draped. Using
2 biopsy or size 16 needles under C-Arm control we entered the
cyst. If the cortex of cyst was thick we drilled the cortex. The
content of cyst was aspirated under pressure which resulted in
cutting and separating of internal capsule of bone cyst. Then we
measured the volume of fluid after aspiration. We then washed
cyst hole by normal saline and injected 40 mg methyl
prednisolone acetate for every milliliter aspired fluid into
cyst with maximum of 200 mg methyl prednisolone. Finally
compression bandage and sling was applied.
For
children under 6 years old we used a long leg plaster cast plus
pelvic band and for older children we recommended axillary
crutch.
Control
radiographs were taken at 2-3 months interval. The signs of
amelioration included reduction of cyst size, increase thickness
of cortex increasing
density within cyst by calcification or new bone trabecular
formations.
Findings:
In
18 patients with humerus cysts. A 10 year old girl developed
pathologic fracture after 2 injections at 6 months follow up.
Three patients had no response to treatment. 15 of patients had
favorable outcome during 6-18 months follow up.
9
patients (75%) had cyst in femur bone. All three patients had
favorable results. Only one patient developed coxa vara with 110
degree angulation. Three patient with upper third of tibia cyst
responded well to treatment. (25%) Three patients were well
treated in the first 4-6 months post injection. 5 patients of
femoral bone cyst had no response to treatment.
Table
1: Data summary and response to treatment
Sex
|
Male
18
(60%)
|
Female
12
(40%)
|
|
|
Age
(years)
|
4.5-19
( mean 11.7)
|
|
|
|
Chief
complaint on presentation
|
Pathologic
fracture
16
(53%)
|
Pain
5
(16%)
|
Limp
8
(66%)
|
|
Location
|
Proximal
humerus
15
(83%)
|
Mid
humerus 3(17%)
|
Upper
third tibia
3
(25%)
|
Proximal
femur
9
(75%)
|
No.
of injections
|
Once
N=
4 (13.3%)
|
Twice
N=
18 (60%)
|
Three
N=
8(26.6%)
|
|
Response
to injection
|
Good:
humerus15 (83%)
Femur 4
(44%)
Tibia 3
(100)
|
Poor:
Humerus
3 (19%)
Femur 5 (56%)
|
|
|
Complications
|
New
Pathologic fracture
1
(3%)
|
Coxa
vara
1
(3%)
|
|
|
Discussion :
Our
results showed satisfactory response in most of the patients
sustained humeral bone cysts, with favorable response to steroid
injection in hummers about tow folds of the femoral lesions. We
also showed a satisfactory healing rate in all of the tibial
cases. Satisfactory results obtained where at least two
injections was performed.
Steroid
have anti-prostaglandin effect and can neutralise biochemical
components in the cyst such as interlokin 1 and proteolytic
enzymes which play an important role in cyst recurrence.(19)
scaglietti et al reported success
rate are varied
between 90-95%
cases. (17)
The
success rate by Oppenhein was reported in 40% by,Galleon. H in
75% (20) and by Companocci in 50% of the cases. (21)
In
our Group we had success rate of 44% for femur cyst.wthich is
similar to Hashemi Negad W.G.Cole.
(22)
Our
results are comparable to others with success rate of 83%.for
humeral cyst that confirms the effectiveness of steroid
injection in humeus UBC cyst and has a low morbidity. Steroid
injection may need several injections and requires long time
follow up.
Conclusion:
Treatment
of UBC by injection of methylprednisolon acetate in the lesion
is a simple and effective method with a low rate of
complication; we recommend this method for treatment of UBC of
humerus, tibial and only for small cysts of femur .because of
less favorable results in the UBC of the femur, and other
therapeutic options must be considered.
During
clinical consultation parents should be informed about success
rate possibility of changing treatment plan and that patient may
need several injections.
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