After a Craniectomy, Where Does the Skull Go?

When swelling threatens the brain and medicines haven’t controlled it, surgeons may remove part of the skull to give the brain room.¹ The removed bone isn’t thrown away. Most hospitals keep it so it can be put back once the swelling is gone, usually weeks to months later, in a surgery called cranioplasty. It is kept in one of two very different places, a hospital freezer or the patient’s own body. No single method is standard everywhere, and each trades one risk for another. If the stored bone becomes infected or wears away, a custom implant of titanium, acrylic, or plastic can take its place.

The Two Places Your Skull Piece Is Kept

The removed piece is often sealed and frozen in a hospital skull bone bank at about -80°C.² It is handled under sterile conditions and can stay frozen for months to years.³

For the patient and family, the freezer route is mostly invisible. The flap goes straight from the operating room to sterile packaging and storage, so there is no extra procedure, and the only wound is the scalp incision from the first operation.

Other surgeons tuck the bone into a pocket under the skin of the patient’s belly.⁴ Living tissue around it may keep the bone alive, and the method costs very little.⁵ In children, where space and freezer bone loss are concerns, the bone can even be split into pieces and stored in the belly.⁶

The surgeon makes a small cut in the abdomen, slips the bone under the skin and fat, and closes the wound. Family members will see a firm bulge and a scar on the belly, usually on one side. That wound is a second surgical site that has to heal, so there are two places to watch for problems. When the time comes, a second small surgery reopens the pocket to take the bone out, which adds a little operating time.

Is the Frozen Bone Still Safe to Use

Freezing keeps the bone’s shape but not its life. Bone frozen longer than four months had no living bone-building cells left.⁷ It can also carry bacteria: about 28% of frozen flaps grew bacteria when tested.⁸ Bone can pick up germs during removal, handling, or storage, and a contaminated flap could infect the new surgical site. So a sample is usually sent to the lab before reuse, and a positive result is a reason the surgeon may not use that piece. One hospital found so many positive cultures and so few reused flaps that it questioned whether freezing was worth it.⁹

Some surgeons heat-sterilize frozen bone in a pressure steamer before putting it back.¹⁰ The structure stays mostly intact even though the remaining cells die.¹¹ Steaming may lower infection risk while raising the chance the bone later wears away.¹² In one series of sterilized flaps, only 2% became infected and most looked good years later.¹³

“Dead” bone still works. The replaced piece acts as a scaffold rather than living tissue, and the body’s own blood vessels and cells grow in from the edges. That is why healing at the margins matters more than whether the bone itself is alive.

Which Storage Method Has Fewer Infections

In one randomized trial, 8% of patients with frozen bone got infections and none with belly-stored bone did.¹⁴ All of those infections were MRSA, a drug-resistant staph.¹⁵ Another study found more infections with frozen bone only in head-injury patients, 29% versus none.¹⁶

A larger study found infections in 18% with belly storage and 11% with freezing, a difference that could be chance.¹⁷ So neither method is clearly safer everywhere. When infection risk and bone loss are controlled, the patient’s own bone remains the lowest-complication choice.¹⁸

After the bone goes back, watch for redness, swelling, or drainage at the scalp wound, and for fever or a worsening headache in the following weeks. Call the surgical team promptly, because infected bone often must be removed.

When the Bone Wears Away After It Goes Back

Replaced bone survives only if blood vessels from the scalp, skull edges, and brain lining grow into it.¹⁹ Living bone is constantly broken down and rebuilt, and the flap needs a good blood supply to keep up. If new vessels don’t reach all of it, the parts without supply are the ones most likely to thin. Dead bone that isn’t replaced by new bone can’t keep its strength. When that balance fails, the bone can gradually wear away.²⁰

This wearing away often appears months to years later. The area may soften, sink, or feel uneven, and scans at follow-up visits check for thinning. A second repair with an implant may be offered.

Children’s replaced bone is more likely than adults’ to wear away later and need another surgery.²¹ A child’s skull is still growing, and the replaced bone doesn’t always grow along with it. Because freezing worsens this in children, belly storage may suit them better.²² Follow-up usually continues longer for children, and families should expect scans over time.

When the Bone Goes Back In

Recovery a year later was similar whether the bone went back early or later.²³ But early replacement carried about four times the risk of fluid buildup on the brain needing treatment.²⁴ Early surgery was shorter with less blood loss, while infection and overall complications showed no clear difference.²⁵ Another study found similar seizure and function results either way.²⁶

For your family member, the date depends on several things. Brain swelling must be fully down, the scalp wound must be healed with no infection, and general health must allow another operation. The surgeon then weighs fluid buildup risk against waiting longer. Expect the date to be a plan that can shift, not a promise.

If the Bone Can’t Be Used

Acrylic bone cement is the most widely used synthetic material.²⁷ But it had the highest infection rate in one large series, 28% beyond three months.²⁸ Titanium mesh had fewer infections than acrylic in another study.²⁹ Titanium more often wore through the skin, though, in 17% of cases.³⁰ That happens because the mesh is thin and sits just under the scalp, so if the skin over it is thin or damaged by earlier surgery or radiation, the metal can eventually show through. The implant may then have to be removed or covered with new tissue, which is why scalp quality is part of the decision. In one small study, acrylic patients felt less distress and anxiety than titanium patients.³¹

PEEK, a light, strong plastic, can be 3D-printed to fit the hole exactly.³² It doesn’t interfere with later scans.³³ But 11% had deep infections in one series.³⁴ Hydroxyapatite implants, made of a bone mineral, can let real bone grow into them.³⁵ How much grows in varies widely, about 37% on average in one study.³⁶ Custom implants also cost far more than reusing the patient’s own bone.³⁷

No material is best for every patient. The choice depends on the size of the defect, the patient’s age, and the infection and skin risk, and surgeons may favor what they have the most experience using.

Living Without Part of the Skull Until Then

Patients often feel restricted and avoid activities or social events.³⁸ Many fear falling and injuring the unprotected brain,³⁹ and many feel their appearance has changed dramatically.⁴⁰ The more independent patients are, the more restrictive the missing bone feels.⁴¹

The fear is grounded in something real. Where the skull is missing, only skin and muscle lie over the brain, so a knock that would normally be harmless could cause injury. The area may also look sunken, often because the swelling has gone down and outside air pressure presses the scalp in. That look is common, but a sinking that worsens, or new headache, confusion, or weakness, should be reported promptly.

A protective helmet is usually advised whenever the patient is out of bed. It should fit snugly over the unprotected area and be worn consistently while walking and during transfers. Ask the care team how long to wear it each day and whether it is needed during rest or in the car. A helmet that is uncomfortable or poorly fitted tends not to be worn, so tell the team so it can be adjusted. At home, clear trip hazards and avoid pressure on the soft spot while sleeping. Hats or scarves can help with appearance worries.