Treatment of Unicameral and Aneurysmal Bone Cysts by Minimally Invasive Percutaneous Injection of Grafton DBF Putty Using the Kyphon Cement Delivery System ()
1. Introduction
Unicameral Bone Cysts (UBC) are benign lesions with poorly understood etiology. They may resolve spontaneously typically after pathologic fracture and with advancing age; however they can be recalcitrant even after puberty.
Treatment is needed in symptomatic patients depending on size, location and fracture or threatened fracture.
Aneurysmal Bone Cysts (ABC) are neoplasias typically containing USP6-rearrangements. Good results and spontaneous healing can be achieved by injection of alcoholic solutions. However, often additional measures are needed for restitution of the bony defect.
We wish to communicate a minimally invasive technique to induce healing of these persistent cystic bone defects injecting the highly viscous paste of Graftonâ DBF Putty (demineralised allogenic bone containing fibers) mixed with autologous bone marrow (BM), using the Kyphonâ Cement Delivering System (Medtronic) resulting in a high rate of bone regeneration.
2. Patients and Methods
Eight consecutive patients with symptomatic large UBC (humerus, pelvis, femur, calcaneus, Table 1), recurrent after different procedures, were treated since 2016 by the technique presented. Five patients with ABC (pubic bone, femoral neck, tibia, Table 2) not showing bone remodeling at a minimum follow-up of 3 months after inactivation by Aethoxysclerol 3% were treated accordingly. Biopsies taken at filling with Graftonâ DBF Putty in these cases proved no remnants of pathologic tissue. Further details of the otherwise healthy patients aged 15 to 27 years are given in Table 1 and Table 2.
Two 8G Jamshidi needles CareFusionâ are inserted under fluoroscopy or computer tomography (CT) to have 2 portals—one for injection, the other for “ventilation”. After aspiration of the cystic fluid content radio opaque dye (Iopamiroâ) is injected to document its distribution within the cavity and to exclude extraosseous leakage as described in detail by Rougraff and Kling [1]. Graftonâ DBF Putty (3 to 40 cc) was mixed with bone marrow aspirate in the relation of about 2:1 to 1:1 (Table 1, Table 2). Bone marrow aspirate (each sample maximally 5 cc) is taken from various pelvic locations to provide sufficient osteoblastic progenitor cells [2]. The bone marrow aspirate is mixed with DBF and this highly viscous paste is then injected using the Kyphonâ Cement Delivering System providing the well controlled high pressure under image intensifier control (CT in special locations) of the extrusion of the contrast dye through the ventilation needle (Figure 1 and Figure 2).
3. Results
There was sufficient incorporation/restitution of bone in 11 patients at a minimum follow-up time of 8 months. In 2 patients a second intervention (1 UBC at 5 years, 1 ABC at 2 years following the first one) was successful. No patients
DBF—Graftonâ DBF Putty, DBM—Demineralized Bone Matrix, BM—Bone Marrow aspirate. Volume calculated based on the radii of an elliptoid body: a × b × c × d × π × 4/3.
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Figure 1. The Graftonâ DBF Putty is mixed with the aspirated autologous bone marrow and filled into the applicator of the Kyphonâ Cement Delivering System and injected into the calcaneal unicameral bone cyst.
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Figure 2. (A) Unicameral bone cyst following repeated fractures and interventions since age 6 years (December 2016); (B) Image intensifier documentation of the cyst filled with Iopamiro (a) and extrusion of the contrast medium by filling with Graftonâ DBF Putty/BM (b) (January 2017); (C) MRI at 14 months ((a), March 2018) and 21 months ((b), October 2018) after injection of Graftonâ DBF Putty/BM.
DBF—Graftonâ DBF Putty, DBM—Demineralized Bone Matrix, BM—Bone Marrow Aspirate. Volume calculated based on the radii of an elliptoid body: a × b × c × d × π × 4/3.
suffered fractures and all are pain free at present. Images of selected cases of UBCs und ABCs are presented in Figures 2-6; imaging findings at follow-up are given in Table 1 and Table 2.
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Figure 3. Aneurysmal Bone Cyst of the pubic bone/acetabulum; (A): before intervention December 2013; (B): 2 years after filling with Graftonâ DBF Putty/BM June 2016.
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Figure 4. (A) Aneurysmal Bone Cyst. MRI showing the extensive intertrochanteric cyst and the fluid sedimentation levels characteristic for Aneurysmal Bone Cysts (November 2013); (B) X-Ray documentation of the Aneurysmal Bone Cyst before treatment (November 2013); (C) The X-Ray 3 years after filling with Graftonâ DBF Putty/BM shows the well restructured intertrochanteric region (March 2017).
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Figure 5. (A) Pathologic fracture through Unicameral Bone Cyst ((a), (b) February 2012). The cyst remained unchanged during 2.8 years f/u after osteosynthesis ((c), (d) November 2014); (B) (November 2019) Reconstitution of bone 5 years after removal of implants and simultaneous filling with Graftonâ DBF Putty/BM.
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Figure 6. (A) X-Rays and corresponding MRI of calcaneal Unicameral Bone Cyst (April 2018); (B) X-Ray (a) and corresponding CT ((b), soft tissue window; (c), bone window) 2 years after filling with Graftonâ DBF Putty/BM (June 2020)-intervention shown in Figure 1. Marginal incorporation probably related to non-force-transmitting region.
No adverse reactions to the DBF/BM implant or complications related to technical aspects and the application system were observed.
4. Discussion
The cause of UBC (synonymously used for juvenile bone cysts or simple bone cysts) is poorly understood. Initially UBC was treated mostly by extensive curettage and bone transfer [3]. Since the introduction of intracystic Corticosteroid-Injection by Scaglietti et al. [4] less invasive methods are now mostly used; among them are intramedullary nailing and steroid injection [5], injection of bioabsorbable bone cement [6] and artificial bone substitutes [7]. However, so far there is no evidence to determine the best method for treatment [8]. One randomized trial comparing intralesional bone marrow and steroid injections showed superiority of the latter [9].
Good results with the injection of Demineralized Bone Matrix (DBM) mixed with autologous bone marrow aspirate into UBCs were first reported by Rougraff and Kling [1] and confirmed by several studies, e.g. Cho et al. [10] and Gundle et al. [11].
Graftonâ DBF Putty was used in our patients because of its superior osteoinductivity and osteoconductivity compared to DBM [12] [13] [14].
ABCs are lesions unrelated to UBC exhibiting USP6-rearrangement, a marker involved in the development and spontaneous regression of neoplastic processes [15]. We add our cases of ABC in this study as we use the same treatment principles as in UBC if the standard treatment with Aethoxysclerol and recently augmented by surgiflo [16] has successfully inactivated the process, but no new bone formation shows up after at least 4 months.
The Kyphonâ Cement Delivering System developed for the injection of cement in kyphoplasty proved to be a useful device to inject the pasty mixture of DBF/BM under well controlled pressure.
Drawbacks of this study are the lacking of a control group and the still relatively short f/u.
5. Conclusion
The technique of percutaneous treatment of inactive cysts appears to be effective, minimally invasive and may be considered as a primary choice instead of large open procedures. The use of Graftonâ DBF Putty with higher osteoinductive and osteoconductive potential appears to enhance the good results achieved so far with DBM. The minimally invasive injection of the highly viscous paste needs an application system as provided by the Kyphonâ Cement Delivering System (Medtronic). The presented system has been useful in other bone defects, e.g. after radiofrequency ablation and cystic degenerative changes of fibrous dysplasia.
Patient Consent
The patients were informed that data from their case would be submitted for publication, and informed consent was obtained.
Acknowledgements
We gratefully acknowledge the collaboration with Jorge J. Herrero, Sales and Therapy Manager Interventional and Biologics, who has drawn our attention to Graftonâ DBF Putty and the Kyphonâ Cement Delivering System as well as for the assistance in the surgical interventions.
No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this article.