SYMPOSIUM: HIGHLIGHTS OF THE ISOLS/MSTS 2009 MEETING
Injection of Demineralized Bone Matrix With Bone Marrow
Concentrate Improves Healing in Unicameral Bone Cyst
Claudia Di Bella MD, Barbara Dozza PhD,
Tommaso Frisoni MD, Luca Cevolani MD,
Davide Donati MD
Published online: 22 June 2010
? The Association of Bone and Joint Surgeons1 2010
that usually spontaneously regress with skeletal maturity;
however, the high risk of pathologic fractures often justifies
treatment that could reinforce a weakened bone cortex.
Various treatments have been proposed but there is no
consensus regarding the best procedure.
We compared the healing rates and
failures of two methods of cure based on multiple injec-
demineralized bone matrix (DBM) in association with bone
marrow concentrate (BMC).
We retrospectively reviewed 184 patients who
had one of the two treatments for unicameral bone cysts
with cortical erosion. Clinical records were reviewed for
treatment failures and radiographs for healing in all
patients. The minimum followup was 12 months for the
Unicameral bone cysts are benign lesions
Steroids Group (mean, 48 months; range, 12–120 months)
and 12 months for the DBM + BMC Group (mean,
20 months; range, 12–28 months).
After one treatment we observed a lower healing
rate of cysts treated with multiple injections of steroids
compared with the healing after the first injection of
DBM + BMC (21% versus 58%, respectively). At last
followup, 38% healed with steroids and 71% with
DBM + BMC. The rate of failure after one steroid injec-
BDM + BMC (63% versus 24%, respectively). We
observed no difference in fracture rates after treatment
between the two groups.
A single injection of DBM added with
autologous bone marrow concentrate appears to provide a
higher healing rate with a lower number of failures com-
pared with a single injection of steroids.
Level of Evidence
Level III, therapeutic study. See the
Guidelines for Authors for a complete description of levels
Unicameral bone cysts (UBCs) are benign self-limited
lesions in long bones of skeletally immature individuals
often located in the proximal humerus and proximal femur
. UBCs are frequently asymptomatic [7, 8, 12, 21] and
may regress spontaneously [7, 8, 12, 21]. However, surgery
is often advised because the bone cortex is usually eroded
by the lesion and weakened, rendering the bone at risk for
pathologic fracture [1, 22]. The main goals of surgery are
therefore to decrease the risk of fracture and enhance cyst
Each author certifies that he or she has no commercial associations
(eg, consultancies, stock ownership, equity interest, patent/licensing
arrangements, etc) that might pose a conflict of interest in connection
with the submitted article.
Each author certifies that his or her institution has approved the
human protocol for this investigation, that all investigations were
conducted in conformity with ethical principles of research, and that
informed consent for participation in the study was obtained.
This work was performed at the Rizzoli Orthopaedic Institute,
C. Di Bella, T. Frisoni, L. Cevolani, D. Donati
Department of Oncology Orthopaedic, Rizzoli Orthopaedic
Institute, Bologna, Italy
C. Di Bella, B. Dozza, T. Frisoni, L. Cevolani, D. Donati (&)
Bone Regeneration Laboratory, Codivilla-Putty Research
Institute, Rizzoli Orthopaedic Institute, Via di Barbiano 1/10,
40136 Bologna, Italy
Clin Orthop Relat Res (2010) 468:3047–3055
Curettage with removal of the cyst membrane and
bone grafting has been considered for many years the
gold standard procedure [8, 27] since it provides enough
osteogenic stimulus to enhance healing. Although the
bone grafts potentially promote new bone formation
inside the cyst, the rate of recurrence is 5% to 50% by 1
to 8 years. Further, donor site morbidity has reduced the
appeal of this procedure for some surgeons [11, 26, 35].
Thus, there was a need for less invasive treatments
considering the benign and self-limited nature of the
A number of alternative, less invasive methods have
been proposed in recent years . Repeated percutaneous
injection of corticosteroids was proposed by Scaglietti in
1979 . Owing to the low morbidity, the simplicity, and
the high healing rate reported by Scaglietti (90%), this
treatment has been widely used [3, 4, 41]. However,
subsequent studies reported a lower healing rate for this
procedure with only 41% to 63% healing after the first
injection [6, 13]. Sung and colleagues reported a failure
rate of 84% after the initial treatment with steroids and
76% after the second procedure . The injection of
bone marrow (BM) alone [5, 6, 9, 21, 42, 43] or in
combination with demineralized bone matrix (DBM) [17,
18, 29, 30, 35] has also been proposed as an alternative to
steroids for treating UBC. BM should provide osteopro-
genitor cells and DBM could stimulate new bone
formation thanks to its osteoinductive and osteoconductive
properties [20, 30].
We therefore (1) asked whether a single injection of
autologous bone marrow concentrate (BMC) combined
with DBM for treating UBC would produce comparable
healing rates compared with multiple injections of
corticosteroids at the first year of followup; (2) determined
the healing rate at last followup independent from the
number of treatments needed to obtain healing; and (3)
evaluated the relationship of failure in relation to the site
and the size of the cyst, the location of the cyst in relation
to the epiphysis, and the age of the patients.
Patients and Methods
We retrospectively reviewed the records of all 230
patients present in our bone tumor register for UBCs in
long bones from 1998 to 2009. Of these patients, 35 were
not surgically treated, five were treated with open surgery,
and six were lost to followup shortly after treatment. Of
the remaining 184 patients, 143 were treated with
repeatedinjections of methylprednisolone
Group) and 41 with a single injection of DBM associated
with autologous BMC (DBM + BMC Group). There
were 122 males (66%) and 62 females (34%). The mean
age was 10 years (range, 2–21 years). The cyst was
located in the humerus in 137 cases (74%), in the femur
in 42 cases (23%), and in other sites such as the radius
and tibia in five cases (3%). Clinical presentation was a
pathologic fracture in 77% of the cases (143 of 184), pain
in 5% (nine of 184), and incidental radiographic finding
in the others (12% [32 of 184]). The lesion was consid-
ered active in 78% of the cases (144 of 184). There were
no statistical differences between the two groups (steroids
versus DBM + BMC) with respect to age, gender, site of
the lesion, and clinical presentation (Table 2). The mini-
mum followup was 12 months for the Steroids Group
(mean, 48 months; range 12–120 months) and 12 months
for the DBM + BMC Group (mean, 20 months; range,
In both groups, the injection was performed under
general anesthesia with a fluoroscopy guide. In the Steroid
Group, two needles were inserted proximally and distally
inside the cyst; then after ‘‘washing’’ of the lesion with
saline solution, we injected 80 mg methylprednisolone
regardless of the cyst size. In this group, we considered as
‘‘treatment’’ a cycle of three repeated injections performed
in less than a 6 months interval. In the DBM + BCM
group, 18 to 20 mL BM was aspirated from the anterior
iliac wing and centrifuged twice to obtain 9 to 10 mL
BMC. BMC was prepared using the FIBRINET1Kit
(Cascade Medical Enterprises, LLC, Wayne, PA) accord-
ing to the manufacturer’s instructions. This procedure takes
approximately 22 minutes. At the end of the procedure, the
product included mononuclear progenitor cells, fibrin, and
platelet-rich plasma . When mixed with the deminer-
alized bone powder (Musculoskeletal Tissue Bank of the
Rizzoli Orthopaedic Institute), the marrow concentrate
remains in a semisolid phase, thus maintaining this form
also in the cystic cavity after injection. While the paste is
being made, a single needle was percutaneously inserted
inside the cyst allowing the outflow of the cystic liquid by
aspiration. Thereafter, the needle was used to scrape out the
inner wall of the cyst as well as the internal trabecular
structure. Then the mixture of BMC and DBM was injected
under pressure in the cystic cavity. The quantity of DBM
varied from 5 to 15 mL in relation to the cyst size. In both
cases, the procedure lasts from 30 to 45 minutes.
All patients were discharged the day of surgery. We
recommended restricted activities in all patients for
15 days, after which they were allowed free movement and
their usual physical activities.
Patients in both groups attended the outpatient clinic to
assess cyst healing and clinical results at 2, 6, and
12 months after surgery and then annually until the end of
skeletal growth. We obtained radiographs of the cyst at
each control, and MRI assessment was performed at 12 and
3048Di Bella et al.Clinical Orthopaedics and Related Research1
Three of us (CDB, TF, LC) independently evaluated the
radiographic films using the modified Neer score system
developed by other authors [6, 34]; the senior author (DD)
confirmed all determinations. The Neer classification 
has four categories: ‘‘Neer I,’’ complete cyst resolution;
‘‘Neer II,’’ partial cyst resolution; ‘‘Neer III,’’ persistence
of the cyst with no immediate need for treatment; and
‘‘Neer IV,’’ nonresolution of the cyst with the need for
treatment to prevent fracture (Table 1).
The treatment was considered a failure when either (1) a
fracture occurred; (2) there was no evidence of healing on
radiographs after 6 months; or (3) a recurrent cyst required
subsequent treatment (Neer IV).
We determined differences between the two groups of
patients. Age was evaluated with one-way analysis of
variance expressed in terms of mean ± SD of the mean,
site of the lesion with Pearson’s chi square test, and gender
and clinical presentation with Fisher’s exact test (Table 2).
The same test was used to evaluate the results after the first
treatment (Table 3) and at the last followup (Table 4). The
differences in the two groups related to the number of
treatment and number of injections to healing were
Table 2. Descriptive baseline data*
Data Series (184) Steroid Group (143)DBM + CM Group (41)p value
Mean age 9.89 (± 3.9)9.9 (± 4) 9.88 (± 3.3) NS
Males (%) 122 (66)95 27NS
Females (%)62 (34) 48 14 NS
Site of the lesion
Humerus 137 (74.5)108 (75.5)29 (70.7) NS
Femur 42 (22.8) 31 (21.6)11 (26.8)NS
Others 5 (2.7)4 (2.7) 1 (2.4)NS
Clinical presentation (%)
Pathologic fracture143 (77) 112 (78.3)31 (75.6)NS
Pain 9 (4.8)7 (4.9)2 (4.8) NS
Incidental radiograph32 (12) 27 (18.8)5 (12.1) NS
Active cysts 144 (78.2)111 (77.6) 33 (80.4)NS
* The two groups resulted similar for age, gender, site, and clinical presentation; DBM = demineralized bone matrix; BMC = bone marrow
concentrate; NS = not significant.
Table 3. Comparison of the results after the first treatment (first year followup) in the two groups
ResultsSteroid group (143) DBM + CM group (41)p value
Cyst healing rate (Neer I, II)30 (21) 24 (58.5)
Failures 91 (63.6) 10 (24.3)
Fracture 24 (16.7)5 (12.2)
No response to treatment (Neer IV)67 (46.8)5 (12.2)
DBM = demineralized bone matrix; BMC = bone marrow concentrate; NS = not significant.
Table 1. Modified Neer classification of radiologic results
IHealedCyst filled with new bone, with or without small radiolucent
area(s)\1 cm in size
Healed with defects Radiolucent area(s)\50% of the diameter of the bone with enough
cortical thickness to prevent fracture
Radiolucent area[50% of the diameter of the bone and with a thin
cortical rim; no increase of the size of the cyst
IIIPersistent cystContinued restriction of activity, possible
repeated treatment required
Cyst reappeared in a previously obliterated area or a radiolucent area has
increased in size
Need for repeated treatment
Volume 468, Number 11, November 2010Treatment of Simple Bone Cysts3049
evaluated with analysis of variance; when the Levene test
for equality of variances was significant (p\0.05), the
Mann-Whitney test was used. We performed the survival to
failure (defined above) using the Wilcoxon (Gehan) esti-
mator of survival function . The same analysis was
performed to evaluate the influence of group, location,
localization in relation to the growth plate, age, and
dimensions to the survival. Then multivariate Cox regres-
sion with Wald backward method was performed to
identify the more predictive model for failure. The odds
ratio (OR) for each parameter with 95% confidence inter-
vals (CIs) was used to express the Cox regression results.
We used the Statistical Package for the Social Sciences
(SPSS) software, Version 15.0 (SPSS Inc, Chicago, IL) for
After the first treatment, the healing rate was higher
(p\0.001) in the DBM + BMC Group than in the Steroid
Group (24 of 41 [59%] versus 30 of 143 [21%], respec-
tively) (Fig. 1). The number of failures was higher
(p\0.001) in the Steroid Group (91 of 143 [63%]) than in
the DBM + BMC Group (10 of 41 [24%]), although the
number of fractures occurring in the first year was similar
in the two groups (Table 3).
The healing rate independent from the number of
treatments was higher (p\0.001) in the DBM + BMC
Group (29 of 41 [71%]) than in the Steroid Group (54 of
143 [38%]). Fifty-six of 143 patients (39.2%) in the Steroid
Group and seven of 41 patients (17.1%) in the DBM +
Table 4. Comparison of the results at followup in the two groups
Type of resultSteroids group (143) DBM + BMC group (41) p value
Healing rate (%) 54 (38) 29 (71)
Number of treatments* needed to obtain healing (mean ± SD)1.66 (± 0.6) 1.1 (± 0.3)
Number of injections needed to obtain healing (mean ± SD)4.3 (± 3.9) 1.1 (± 0.3)
Final Neer score (%)
I 11 (7.7) 8 (19.5)
II 43 (30)21 (51.2)
III 56 (39.2) 7 (17)
IV 33 (23)5 (12.2)
* In the DBM + BMC group, one treatment is equal to one injection; in the steroid group, one treatment can be more than one injection;
DBM = demineralized bone matrix; BMC = bone marrow concentrate.
Fig. 1A–E Radiographs of a 6-year-old female patient treated after
two fractures occurred earlier in the left proximal humerus. (A)
Intraoperative check with the needle inserted. (B) Result at 2 months;
intense periosteal reaction can be seen in the medial cortex of the cyst.
(C) 6, (D) 12, and (E) 18 months followup. From 2 months to date,
the patient was permitted to resume normal physical activity,
3050 Di Bella et al.Clinical Orthopaedics and Related Research1
BMC Group obtained incomplete healing of the cyst
(Neer III) with no immediate indication for subsequent
surgery. These patients continued to be followed up but the
cyst was not considered healed yet. The number of patients
who needed more than one injection to heal as well as the
number of treatments needed to obtain healing resulted
statistically higher in the Steroid Group than in the
DBM + BMC Group (Table 4).
The DBM + BMC Group had fewer (p = 0.001) fail-
ures than the Steroid Group during the first two year
followup (Fig. 2). Cyst size larger than 21 cm2had a higher
(p = 0.04) failure risk although we observed no difference
in failure rates among the different cyst locations (humerus,
femur, others). Cysts located less than 1.5 cm from the
growth plate had a higher (p = 0.005) failure rate than
those located more than 1.5 cm (Fig. 3). Finally, patients
younger than 8 years had a higher (p = 0.001) rate of
failure (Fig. 4). Age influenced the failure rate (Wald sta-
tistic of 0.004; OR,.0.923; 95% CI, 0.87–0.97).
UBCs are benign lesions that usually spontaneously regress
with skeletal maturity ; however, when pathologic
fractures occur with persistent radiographic signs of cyst,
Fig. 2 Lifetime table analysis of the
treatment survival in the two groups.
The end point is the failure of the
procedure. The treatment was consid-
ered failed when a fracture occurred or
when there was no response to treat-
ment after 6 months or in the presence
of recurrence of the cyst with the need
for subsequent treatment (Neer IV).
TheDBM + BMC
fewer failures compared to the Steroid
p = 0.001).
Fig. 3 Lifetime table analysis of the
treatment survival looking to the local-
ization of the cyst in relation to the
growth plate in the whole series. The
end point is the failure of the procedure.
Patients with cysts located less than
1.5 cm from the growth plate had a
higher failure rate than those located
more than 1.5 cm (Wilcoxon-Gehan
test;p = 0.005).
DBM + BMC =
matrix + bone
Volume 468, Number 11, November 2010Treatment of Simple Bone Cysts 3051
these young patients are strictly forbidden to take part in
recreational physical activities. Treatment can reinforce the
bone cortex. Numerous types of treatments have been pro-
posed such as steroids, natural bone marrow, bone matrix or
other injection materials [19, 24, 32, 36, 42, 43], curettage
there was no consensus regarding the best procedure.
Moreover, because the various literature reports all methods
of treatment with a wide range of healing rates, it is difficult
to derive clearcut criteria (Table 5). We therefore deter-
mined (1) whether during the first year of followup a single
injection of autologous BMC combined with DBM for
treating UBC would produce comparable healing rates than
multiple steroid injections; (2) the healing rate at last fol-
the cyst with the location of the cyst in relation to the
epiphysis and the age of the patients.
We recognize limitations to our study. First, the Steroid
Group has a considerably longer followup compared with
the DBM + BMC Group. Thus, we anticipate more fail-
ures in the DBM + BMC Group during followup. For this
reason, a future study will be necessary to confirm these
preliminary results. Second, the BMC used in our protocol
is different from that in natural bone marrow, in which
progenitor cells are diluted in a liquid media with possible
dispersion in the soft tissue outside the cyst , thus
explaining poor results reported in some studies [5, 41].
However, the study was not performed to prove different
outcomes between natural BM and BMC. Rather, the
rationale in the use of BMC in association with DBM is to
provide enough factors such as stem cells and bone mor-
phogenetic proteins, which are able to improve the
osteogenic potential in the cystic area, contrasting the
catabolic phenomena. Third, there are some differences in
the surgical technique between the two methods of cure. In
the Steroid Group we used high pressure cyst lavage
through a double needle inserted in the cortex, while in the
DBM + BMC Group we performed only one needle
insertion with internal scraping.
During the first year, the number of cysts healed with a
single injection of DBM + BMC (59%) was higher
compared with multiple injections of corticosteroids
(21%). These data are difficult to compare with data
presented in the literature due to differences in the method
of evaluation and type and number of bone marrow or
steroid injection. However, most reports that specifically
refer to the healing rate after the first treatment with bone
marrow injection show lower percentages than achieved in
our series [5, 6, 35, 41–43]. On the other hand, the per-
centage of healing rate following the first treatment with
steroid injection in our series is lower than most of other
reports [5, 6, 11, 34, 41]. Fracture of the cyst is one cause
of failure after the first treatment; Neer et al.  reported
up to 80% of fractures in patients followed without sur-
gical treatment. In patients surgically treated, fracture has
been reported in 2.6% of cases treated with curettage and
bone grafting ; from 7.7%  to 28%  and 33%
 in patients treated with marrow or steroid injection.
We observed no difference in the number of fractures that
occurred in our series in the two groups (12% in the
DBM + BMC Group versus 17% in the Steroid Group),
resulting in the average of fractures reported in series
dealing with patients treated with either steroid or bone
marrow injection. A good clinical and radiographic initial
outcome is importantto decreasethe numberof
Fig. 4 Lifetime table analysis of the
treatment survival looking to the patient
age in the whole series. The end point is
the failure of the procedure. Patients
younger than 8 years had a higher rate
of failure than those older than 8 years
(Wilcoxon-Gehan test; p = 0.001).
3052Di Bella et al.Clinical Orthopaedics and Related Research1
hospitalizations and surgeries. In some patients treated
with steroids, more than eight injections were given,
resulting in high costs for families and the healthcare
system. On the other hand, in patients with partial or
complete healing, daily activities, including sports, could
Despite the longer followup in the Steroid Group, the
final cyst healing rate was higher in the DBM + BMC
Group than the Steroid Group (71% versus 38%). The life
table analysis confirmed this difference between the two
treatments. This is particularly important considering the
smaller number of treatments (multiple injections in the
Table 5. Healing rate (after first treatment and final) in major series reported in the literature according to different methods of treatment
Neer et al./1966 45 Observation–8 1–10 1–3 refractures occurred in 80% of cases
129 Curettage/graftingNR 52 2–10 Any site and any age included
Spence et al./
144 Curettage/grafting75 NR 1–4 Underline the use of freeze-dried
cancellous bone as packing material
Scaglietti et al./1979
72 Steroid injectionNR 90 1–3 More than one steroid injection of 40 to
200 mg according to the cyst volume
Scaglietti et al./1982
163Steroid injection NR 24NR Long-term results
Capanna et al./
95 Steroid injectionNR 801–5From 2–7 injections every 2 months until
evidence of cyst response. Neer
Campanacci et al./
178Curettage/graftingNR 671–8 Same as above. Longer followup
141Steroid injectionNR 68
Farber and Stanton/
19 Curettage/grafting5395 4.1 (av)Younger age in curettage and bone
grafting than steroid group
17 Steroid injection7076 3.3 (av)
Lokiec et al./1996  10Native BMI 100 1001–4Neer modified. Injection of average 25 ml
(from 15 to 50)
Delloye et al./1998 8 Native BMI87.5100 1–4.5 Neer modified as Capanna et al. Quantity
of bone marrow not reported
Yandow et al./1998 12Native BMI 42 671–6Personal classification. 18 ml av of bone
Chang et al./2002  14 Native BMI43NR 1–9Personal classification. 12 to 24 ml of
bone marrow injection
65Steroid injection 51NR
Rougraff and Kling/
23DBM + native BMI78 70 1–7Neer classification. 5 to 32 ml of bone
marrow av 18
Kanellopoulos et al./
19DBM + native BMI NR89.51–3.8Underline the role of reaming of the cyst.
Cho et al./2007 28Native BMI 52872–15Final 2.19 injections in steroid group
versus 1.57 in the marrow injection
group. 12 – 50 ml of bone marrow
Sung et al./2008  94Steroid injection16NR 7 (av)Neer classification. Quantity of bone
marrow and steroid not specified
34Steroid injection +
DBM + native BMI
Wright et al./2008 45Steroid injection42420–2Neer classification modified. 9 to 18 ml of
bone marrow injection
39 Native BMI2323
Zamzam et al./2009 28Native BMI57822.5–3.520 ml av of bone marrow injection.
Di Bella et al.
143Steroid injection21384 (av)Neer classification. 10 cc of bone marrow
41DBM + BMC59711.8 (av)
DBM = demineralized bone matrix; Native BMI = bone marrow injection without concentration; BMC = bone marrow concentrate injection;
NR = not reported; av = average.
Volume 468, Number 11, November 2010Treatment of Simple Bone Cysts3053
Steroid Group) and injections needed to achieve this result
(4.3 average in the Steroid Group versus 1.1 in the
DBM + BMC Group). One series comparing steroid to
bone marrow injection reported a higher number of steroid
injections required to achieve the final healing rate .
However, despite the differences in the evaluation method,
most of the failures occurred within the first two years of
followup as reported by other series [11, 30], leaving a
number of patients in the Neer III grade evaluation to be
followed for a long time until evidence of definitive healing
was achieved [3, 4, 27].
When considering factors with a negative effect on the
treatment outcome, the humeral site did not score more
fractures than other sites , although size, younger age
and proximity to the growth plate confirmed their negative
effect on the final healing rate requiring, despite fracture, a
higher number of injections. These observations confirmed
previous reports with age less than 10 years old be the
major risk factor for failure in the UBC series [3–5, 11,
33–35]. As observed by Sung et al.  there is not likely
an age at which risk increases, although younger patients
are more likely to need subsequent treatments to achieve
final healing. This is also likely true for the size and
proximity of the growth plate as these are generally con-
sidered signs of active cyst [4, 16] although these
differences would likely be significant only in larger study
series. Finally, we believe it important to improve the
operative technique by opening of the medullary canal
from the diaphyseal side to reduce the pressure inside the
lesion. This has been attempted using medullary nails or
cannulated screws [2, 28]; however, in those series, the
healing rate of the cyst was not sufficiently consistent
because of the lack of osteogenic stimuli. When an ade-
quate cyst opening procedure is associated with the bone
formation enhancing agents such as BM and DBM, heal-
ing can be more consistent . A number of cysts can be
considered inactive and reasonably heal with no or mini-
mal surgery. Therefore, we need a more accurate cyst
index than previously reported  since this did not
predict fracture .
The healing rate of unicameral bone cyst after the first
treatment has been more frequently achieved with injection
of DBM + BMC than steroid injection. This is also con-
firmed by the healing rate achieved in the last followup
independent from the number of treatments required. We
believe the data support the desirability of a more effective
osteogenic material for bone regeneration in younger
patients with larger cysts or cysts located close to the
regarding statistical analysis and Enrico Lucarelli for manuscript
We thank Elettra Pignotti for contributions
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