Cranioplasty: indications, timing, materials and outcomes

Cranioplasty is the surgical repair of a defect in the cranial vault. It most often follows a decompressive craniectomy: to let a brain injured by trauma, stroke or a surgical complication swell, the surgeon removed a large bone flap.

Other situations lead to it: head injuries, tumours of the bone or meninges, resorption or infection of a bone flap already put back ^[5]. In France, more than 1,700 cranial vault cranioplasties were recorded in hospitals in 2022 ^[5].

Closing the skull protects the brain from knocks, restores the contour of the head and eases daily life. A bone defect also exposes the patient to changes in intracranial pressure, leaks of cerebrospinal fluid and deformities with psychological and social consequences, particularly in the fronto-temporal region ^[5].

Cranioplasty can also improve neurological status. Some patients develop a “syndrome of the trephined” after a craniectomy: motor, cognitive or language disorders that improve with reconstruction. A systematic review of 58 patients found that symptoms began between 3 days and 7 years after the craniectomy, 5.1 months on average, and that cerebral blood flow increased after cranioplasty ^[4].

The international consensus on post-traumatic cranioplasty, published in 2021, distinguishes four windows according to the time elapsed since the craniectomy ^[1]:

The experts agree on several points: earlier cranioplasty may enhance neurological recovery; the patient’s clinical condition should guide timing; poor neurological status alone is not a contraindication; and complications (infection, reoperation, haemorrhage, seizures) do not differ clearly between early and late procedures ^[1].

When the patient’s bone has been stored under the skin, early cranioplasty is recommended to limit its resorption. In hydrocephalus, the consensus advises rebuilding the skull before any cerebrospinal fluid diversion when possible, then monitoring the patient closely ^[1].

In adults, the question of the best material remains open: none has proven superior across all outcomes and complications ^[1]. Each option has its strengths:

The experts acknowledge the risk of autologous bone resorption and consider that custom implants may offer a better cosmetic result ^[1]. In children, the patient’s own bone remains preferred at all ages; failing that, an osteoconductive material is favoured, and synthetic materials are acceptable after the age of 3 ^[1].

A custom implant is designed from the patient’s imaging, before surgery. The main steps:

1. 01CT scan of the whole skull in thin slices (1 mm or less), exported in DICOM format.
2. 02Segmentation: 3D reconstruction of the bone from the slices.
3. 03Design: shape obtained by mirroring the healthy side or by continuing the curvature, then thickness, perforations and fixation points.
4. 04Approval: the surgeon approves the design and placement plan before any manufacturing.
5. 05Manufacturing and inspection: 3D printing, finishing, cleaning, then inspection against the approved model.
6. 06Surgery: the implant, made for the defect, is placed without shaping in theatre.

Common as it is, cranioplasty is not a minor operation. The most closely tracked complications are infection, resorption of the patient’s bone and the need for further surgery:

• in Utrecht, among 168 patients followed for a median of 5.1 years, reimplanted bone resorbed in 36% of the patients concerned; 44% needed revision after a graft of their own bone, against 14% after an implant, and surgical site infection affected 13.5% and 7% of patients respectively, a non-significant difference ^[2];
• in an Australian randomised trial of 64 patients, no salvage cranioplasty was needed with a custom titanium implant, against 25% with the patient’s own bone, after at least 24 months ^[3];
• bifrontal defects are more prone to complications than one-sided defects ^[1].

After surgery, monitoring covers wound healing, signs of infection and, in patients at risk, the onset of hydrocephalus ^[1]. A titanium implant generally does not prevent an MRI scan: always tell the imaging department about it.

This guide summarises the literature; it does not replace the advice of the neurosurgeon, who alone can judge the right timing and technique for each patient.