TREATMENT OF UNICAMERAL BONE CYST USING INJECTABLE CALCIUM PHOSPHATE MATERIAL:
PRELIMINARY RESULTS IN 11 PATIENTS
Welch, RD; Clavenna, A; Johnston, CE; Dempsey, M
Seay Center for Musculoskeletal Research, Texas Scottish Rite Hospital for Children, Dallas, TX
[email protected]
DISCUSSION: The mean follow-up in this series is only one year;
INTRODUCTION: Unicameral bone cysts (UBC’s) are benign tumorlike lesions which occur primarily within the metaphyses of growing
however, the preliminary results suggest that -BSM may be a
long bones of children (Fig 1). Although the etiology remains elusive,
beneficial treatment option for UBC’s. An important observation from
the fluid within UBC’s contains an abundance of potent osteoclastic
this study is that no patients required multiple treatments that are typical
when intra-lesional steroids are used, therefore reducing visits to the
stimulators including IL-1, TNF , PGE2, and MMPs (1, 2). Local bone
operating suite and patient morbidity. In addition, cyst persistence or
resorption is responsible for cyst enlargement resulting in thin weak
recurrence and possible pathologic fracture which often occurs with
cortices and pathological fracture through the lesion. The treatment of
other treatment modalities have not been observed The structural support
UBC’s has included intra-lesional steroid injections, bone marrow
aspirates with or without demineralized bone matrix, multiple drill
provided by the -BSM within the cyst cavity may have contributed
holes, open curettage with bone grafting, and more recently
to pain relief reported soon after injection. As the -BSM is resorbed
intramedullary rods (3). In most series, multiple treatments are
it provides an extensive osteoconductive surface supporting new bone
necessary due to recurrence or persistence of the cyst. Of all these
formation across the expanse of the cyst cavity. (4-6). Trabecular bone
treatments, only intramedullary rods provide any mechanical stability at
interconnectivity across the lesion may be important in preventing cyst
the site of the lesion. Calcium phosphate materials have become
persistence or recurrence. Although the remodeling rate of -BSM is
available which are injectable as a paste and harden in-situ (4,5). Once
not known in children, preclinical animal studies and clinical reports in
set, these materials have considerable compressive strength and appear
adults suggest that -BSM remodels and is replaced by host bone
to undergo osteoclastic resorption and replacement with host bone (4-6).
faster than other calcium phosphate materials currently available (4,6).
We hypothesized that a calcium phosphate bone substitute ( -BSM ,
The longer working time prior to the paste setting also facilitates
ETEX Corp & DePuy Orthopedics) would be a novel and effective
consistent distribution of the material within the lesion during injection.
method to treat UBC’s with a single injection, provide mechanical
These results suggest that a one time definitive treatment of UBC’s with
support to the lesion reducing patient morbidity, and decrease the
-BSM may provide a significant improvement over conventional
incidence of cyst persistence or recurrence after treatment.
therapies. Longer term follow-up in more patients will be required to
confirm this.
METHODS: This study was IRB approved. Diagnosis of the UBC was
made from radiographs and cyst aspirations at the time of injection of
-BSM . Treatment consisted of fluoroscopically placing two large bore
needles (8ga. Jamshidi cannulae) into the proximal and distal aspects of
the cyst cavity to allow for saline lavage followed by injection of the
cement. The -BSM was supplied as a powder in 2.5 to 20 gram
plastic injection bulbs. Sterile saline was added to the injection bulb at
0.8 ml per gram of powder and thoroughly mixed into a wet paste. The
-BSM was expressed into 10 ml syringes which were attached to one
of the Jamshidi cannulae. The second Jamshidi cannula was left open to
vent the cyst as the -BSM was injected. When the -BSM paste
was observed exiting the venting cannula, this cannula was closed and
injection continued to pressurize the paste to help assure complete filling
of the cyst. Postoperative fluoroscopic images were obtained to
document cyst fill with -BSM . Sterile dressings were applied over
the injection portals. Patients returned for follow-up clinical and x-ray
examinations at 3 to 6 month intervals postoperatively.
Fig 1. UBC of proximal humerus
Fig 2. BSM treatment
after one year
RESULTS: To date, eleven patients have been enrolled and treated
using -BSM with a mean follow-up of 12 months (range 4-24
ACKNOWLEDGMENT:
months). There were 6 females and 5 males with ages ranging from 5 to
Supported by the Research Fund, Texas Scottish Rite Hospital for
19 years. The UBC’s were located within the proximal humerus (n=6),
Children, Dallas, Texas
proximal femur (n=3), calcaneus, (n=1), and fibula (n=1). Eight patients
had prior or current pathological fractures involving their cyst. Three
REFERENCES:
patients had previously undergone open curettage and bone grafting, and
1.
Welch RD, et al, Trans ORS, 1998
5 patients had failed intra-lesional steroid injections. Local pain at the
2.
Shindell, R, et al, JPO, 1987
site of the UBC was often a presenting complaint. The -BSM was
3.
Cohen, J, JBJS, 2001
easily injected into the cyst cavities in most patients. In two cases
4.
Welch, RD, JBJS, 2003
showing radiographic evidence of partial consolidation of their UBC’s,
5.
Heymann, D, et al, Histol Histopathol, 2001
greater injection pressures were required. The mean volume of 6.
Lee, DD, Clin Orthop, 1999
BSM administered was 12 grams (range 3 - 25 gms). Most patients
reported pain relief post-operatively. At 3 months, radiographs
demonstrated early remodeling of the -BSM around the periphery of
the cyst wall. At six months, the radiodensity of the -BSM appeared
to decrease slightly and the cement/ cyst wall interface became less
distinguishable. By one year, the overall radiodensity of the lesions
became more homogenous and consolidated suggesting a mixture of
residual -BSM and new host bone (Fig 2). At two years post
treatment, radiographs continue to demonstrate cyst consolidation and
remodeling of residual -BSM . All pathologic fractures healed
uneventfully. There was no radiographic evidence of cyst recurrence and
all patients have returned to previous levels of physical activity.
51st Annual Meeting of the Orthopaedic Research Society
Poster No: 1014