What Is a Bone Void Filler? Types, Uses and Limits
A bone void filler is a material placed in a gap in bone to give new bone something to grow into. The gap might follow a fracture, the curettage of a benign cyst, or the surgery itself, such as when hardware is removed. A space left empty tends to fill with hematoma and fibrous tissue, and bone may be slow to bridge it.
The category is broad, and the materials in it behave very differently. This article explains the main types of bone void filler, where surgeons use them, and where they don't belong.
How a bone void filler works
The core job is osteoconduction. The material acts as a scaffold that blood vessels and bone-forming cells can migrate across. Almost every filler on the market does this to some degree.
Most fillers are also resorbable. The body gradually breaks them down and lays down bone in their place. The rate varies widely between materials, from calcium sulfates that are usually gone quickly to dense hydroxyapatite that can stay for a long time.
Two other properties come up when grafts are compared. Osteoinductive materials signal local cells to become bone-forming cells. Osteogenic materials bring living bone-forming cells with them. Autograft is the only option that offers both. Synthetic fillers offer neither unless they are combined with autograft or marrow aspirate.
Bone void filler or structural graft?
This is the distinction that matters most in practice. In the US, synthetic bone void fillers are generally cleared by the FDA for bony voids that are "not intrinsic to the stability of the bony structure." Many of them sit under FDA product code MQV, calcium compound bone void filler. In other words, the filler is not there to carry load while the bone heals. The plate, the screws or the surrounding bone carry it. When a defect has to bear load during healing, it needs a structural solution, and a void filler alone won't do.
Types of bone void filler
Autograft
Autograft is the patient's own bone, usually taken from the iliac crest or from the operative site. A widely cited review in the Journal of Materials Science: Materials in Medicine describes autograft as still "the gold standard for bone substitution" (Campana et al., 2014). The same review notes its drawbacks: limited supply and the morbidity of a second surgical site.
Allograft and demineralized bone matrix
Allograft is donor bone processed by a tissue bank. Campana and colleagues describe it as osteoconductive and weakly osteoinductive, with concerns about cost, availability and infection risk. Demineralized bone matrix (DBM) is allograft with the mineral removed. That exposes proteins that may support bone formation, though activity can differ between donors and processing methods.
Synthetic bone void fillers
Synthetic fillers are manufactured, so every batch has the same composition, with no harvest site and no donor tissue. On their own they provide osteoconduction only.
Material | Common forms | What to know |
Calcium sulfate | Pellets, beads, injectable paste | Generally resorbs quickly. The usual concern is that it can disappear before new bone has filled the space. |
Calcium phosphate (hydroxyapatite, β-tricalcium phosphate) | Granules, blocks, putty, self-setting cement | The most widely used synthetic family. Campana et al. describe these ceramics as resorbable but weaker than cortical bone. |
Bioactive glass | Granules, putty | Described as bonding to bone through a reactive surface layer. |
Magnesium-based | Self-setting putty or injectable paste | A newer family that sets quickly and resorbs. It has a shorter clinical history than calcium phosphate. See Magnesium Phosphate vs Calcium Phosphate Cement. |
Composites | Varies | Blends of the above, often in a collagen or polymer carrier. |
Where PMMA fits
PMMA (polymethylmethacrylate) bone cement is often mentioned in the same breath. It is a permanent, load-bearing cement used to fix arthroplasty components and in vertebral augmentation, and it does not remodel into bone. That puts it in a different category from resorbable void fillers. Read Bone Void Filler vs Bone Cement (PMMA) for the full comparison.
Clinical uses of bone void fillers
Common uses in orthopedic surgery include:
Fractures. The classic example is the metaphyseal void left after an elevated articular fragment in a tibial plateau or distal radius fracture, filled alongside plate fixation.
Benign bone lesions. Filling the cavity left after curettage of a cyst or benign tumor.
Revision surgery. Filling contained, non-structural defects left when hardware or implants are removed.
Spinal fusion. Some fillers are cleared for fusion procedures, usually combined with autograft or allograft. In the disc space they are used with a cleared interbody device.
Osteotomy and arthrodesis. Filling gaps at the surgical site.
The material type does not decide which of these uses a product can be marketed for. The product's FDA clearance does, and its Instructions for Use (IFU) is the document to check.
When a bone void filler is the wrong choice
The defect is structural. When the void is part of what keeps the bone stable, a filler alone cannot provide the support needed during healing.
The defect is too large. Synthetic fillers are generally not intended for defects that, in the surgeon's judgment, would not heal on their own.
The material can't be contained. A flowable material may escape an open defect unless the product and technique suit it.
A contraindication applies. Each product's IFU lists its contraindications and warnings.
How to choose a bone void filler
No single filler is best for every case. Start with three questions:
Is the defect structural? If it is, a void filler alone is the wrong tool.
What evidence exists for this material in this indication?
Is the product cleared for this anatomical site and this patient?
After that, the choice is mostly about handling: how you'll reach the defect, whether it's contained, whether screws will pass through it and whether you need to see it on fluoroscopy. Injectable vs Moldable Bone Void Fillers works through those questions.
Magnesium-based bone void fillers from Bone Solutions
Bone Solutions makes two magnesium-based bone void fillers. Mg OSTEOCRETE is available as a putty or paste. Mg OSTEOINJECT is a low-viscosity injectable. The FDA summaries describe both as radiopaque, drillable and osteoconductive, and both are "resorbed and replaced with bone during the healing process" (FDA 510(k) K234013).
Under the current clearance, K251522, both are indicated for adults and pediatric patients older than 6 years. Their cleared sites differ:
Mg OSTEOCRETE is cleared for the extremities, pelvis, posterolateral spine and intervertebral disc space. In the posterolateral spine it must be used with morselized autograft and/or allograft. In interbody fusion it must be used with morselized autograft and/or allograft, together with an FDA-cleared interbody fusion device cleared for use with a bone void filler.
Mg OSTEOINJECT is cleared for the extremities and pelvis. It is not cleared for use in the spine.
To compare the two side by side, see Mg OSTEOCRETE vs Mg OSTEOINJECT.
Both are intended for bony voids that are not intrinsic to the stability of the bony structure. Once set, the material acts as a temporary support medium and is not intended to provide structural support during the healing process. Neither is intended for large defects that, in the surgeon's opinion, would fail to heal spontaneously. Rx only. See each product's IFU for full indications, contraindications and warnings.
The published data behind our products is collected on the Technology page. Surgeons and hospital teams can request product information. Distributors can apply to carry our products.
Frequently asked questions
What is a bone void filler made of?
It can be the patient's own bone (autograft) or donor bone (allograft or DBM). It can also be a synthetic, such as calcium sulfate, calcium phosphate, bioactive glass or a magnesium-based cement.
Is a bone void filler the same as a bone graft?
The terms overlap. "Bone graft" usually means autograft or allograft. "Bone void filler" is the FDA term for many synthetic and processed materials placed in non-structural defects.
Does a bone void filler dissolve?
Most resorbable fillers are broken down and replaced by bone over time, at a rate that depends on the material. PMMA bone cement is not resorbed.
Can screws go through a bone void filler?
Some self-setting fillers can be drilled once set. The hardware still carries the load, because a cleared void filler is not intended to provide structural support during healing.
Is a bone void filler load-bearing?
Generally, no. Synthetic bone void fillers are cleared for voids that are not intrinsic to the stability of the bone.
Can bone void fillers be used in children?
Only if the specific product is cleared for it. Indications differ by product, so check the IFU. Mg OSTEOCRETE and Mg OSTEOINJECT are cleared for pediatric patients older than 6 years under K251522.
Comments