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Abstract

Introduction

Cranioplasty is a prevalent procedure in neurosurgery. Nevertheless, restoring the skull's integrity poses significant challenges, particularly in selecting ideal implant materials. Although many neurosurgeons still favor titanium mesh in cranial reconstruction, the new polyetheretherketone (PEEK) material is gaining traction in craniofacial reconstruction. Sparse data compare the outcomes between PEEK and titanium mesh cranioplasties. Hence, this study aims to evaluate the outcomes of these different materials in cranioplasty.

Methods/Design

In this multicenter, assessor-blinded, randomized controlled study, 140 patients will be divided equally into two groups: PEEK cranioplasty and titanium cranioplasty. Eligible patients are adults diagnosed with cranial defects resulting from various conditions such as traumatic brain injury or stroke. The defect size must exceed 25 cm², and participants must consent to the trial. Instead of standard examinations, patients will undergo neurological, motor, cognitive function, and cerebral hemodynamics assessments, and cosmetic evaluations. Examinations will be repeated at 3 and 6 months post-surgery. The primary outcome focuses on implant failure rates within six months, defined by infection or implant exposure. Secondary outcomes include complication rates, neurological outcomes, motor function, cerebral hemodynamics, cosmetic results, and total costs over 6 months.

Ethics and Dissemination

This protocol has been approved by the Biomedical Research Ethics Committee of West China Hospital of Sichuan University. Full disclosures regarding implant materials, potential complications, and patient responsibilities will be provided, with informed consent obtained prior to trial participation. If cognitive function is impaired, next of kin will be informed. Results will be shared through academic conferences, student theses, and peer-reviewed journal publications.

Trial Registration Number

ChiCTR1900024625; Pre-results.

Keywords:

cranioplasty, polyetheretherketone (PEEK) cranioplasty, titanium cranioplasty, randomised controlled trial

• This will be the first multicenter, randomized controlled study assessing the long-term outcomes of titanium mesh cranioplasty and polyetheretherketone cranioplasty.

• This study assists neurosurgeons in choosing alloplastic materials, especially for patients suffering bone resorption with autologous bone cranioplasty.

• Complications following cranioplasty and their relationship to timing will be investigated.

• Subgaleal effusion, less studied in similar research, will also be examined.

• Differing medical conditions and surgeons’ experiences are study limitations; however, personnel will be trained uniformly in advance.

Introduction

Cranioplasty, with its origins dating back to 7000 BC, serves as a protective barrier and offers cosmetic benefits for patients with cranial defects. Over the past half-century, advancements in neurosurgery and emergency care have made this procedure routine. Yet, reconstructing cranial defects continues to challenge surgeons, especially in finding optimal materials.

In an ideal scenario, the implant material should be durable, biocompatible, widely available, and have a low infection rate. Various materials, from autologous bone to metals and plastics, have been used, each with varying success rates. Autologous bone grafts are typically the gold standard due to their low cost and biocompatibility, but complications like bone flap resorption may require reoperation and alloplastic replacements.

Historically, polymethylmethacrylate was an early material of choice for cranioplasty. Despite its favorable properties, its exothermic reaction could injure nearby soft tissues. Other materials like hydroxyapatite and calcium phosphate have their own pros and cons.

Recently, titanium mesh has gained popularity for cranial reconstruction due to its biocompatibility, low infection rate, mechanical strength, and affordability. Moreover, computer-assisted 3D modeling ensures excellent cosmetic results. Yet, complications like allergic reactions, soft tissue erosion, and implant exposure persist. Additionally, titanium mesh can conduct temperature changes, leading to scalp paresthesia.

PEEK implants are now becoming more popular in craniofacial reconstruction. They are radiolucent, chemically inert, stiff, and sterilizable using various methods. The PEEK implants can also be customized to patient-specific defects using 3D printing technology. However, the high cost and potential for epidural effusion post-surgery remain concerns.

Despite PEEK's rising popularity, there is limited research comparing its outcomes with titanium mesh. Thus, this study aims to compare the long-term implant failure rates, aesthetic outcomes, neurological outcomes, and postoperative complication rates between PEEK and titanium mesh cranioplasties.

Objective

The primary objective is to compare implant failure rates (defined as implant exposure or infection requiring removal of synthetic material) within 6 months in cranioplasty patients. Secondary objectives include evaluating complication rates, neurological and cognitive outcomes, motor function, cerebral hemodynamics, and cosmetic results.

Design

The PEEK cranioplasty and titanium mesh cranioplasty (PTCP) study is a multicenter, prospective, assessor-blinded, randomized controlled clinical trial running from December 2019 to June 2021. The trial involves 15 centers across China, staffed by experienced neurosurgeons proficient in both cranioplasty techniques. Uniform standards for neurological, motor, cognitive function assessments, and brain hemodynamics evaluations will be maintained through centralized training. Local ethics committees or the overarching ethics committee will approve all participating hospital sites.

Recruitment and Eligibility

Participants will be recruited from outpatient departments and through patient database reviews for those who have undergone craniectomy. Recruitment starts in December 2019, and each participant will receive financial compensation.

Inclusion Criteria

1. Patients aged over 18 years of either sex.

2. Diagnosed with cranial defect due to conditions such as traumatic brain injury, stroke, or infiltrative tumor.

3. The defect size exceeds 25 cm².

4. Consent to participate in the clinical trial with signed informed consent from patient or next of kin.

Exclusion Criteria

1. Bilateral cranial defect.

2. Active smoking.

3. Diagnosed with diabetes or coronary heart disease.

4. History of radiation therapy.

5. Presence of hydrocephalus or previous bypass surgery.

6. Previous scalp free tissue transfer.

7. Allergy to titanium.

8. Non-initial cranioplasty surgery.

9. Uncontrolled intracranial infection.

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10. Presence of intracranial hematoma.

11. Unhealed scalp.

12. Operative contraindications such as pulmonary infection or poor general condition.

13. Dural defect or tearing during the cranioplasty procedure.

Sample Size

Previous studies indicated that over 25% of patients experienced implant failure with titanium cranioplasty compared to under 10% with PEEK. To achieve a 20% difference in satisfactory outcomes due to implant failure with 80% power and 5% significance, a sample of 120 is required. Considering study quality, we have increased the sample size to 140.

Randomization and Blinding

Participants who consent and meet eligibility criteria will be randomized using simple randomization software into either the PEEK or titanium mesh group. Blinding participants or surgeons is impractical due to the identifiable nature of the implant materials. Thus, participants will be informed of their assigned materials. However, assessors involved in this study will be blinded and not in contact with the randomization process.

Intervention

Upon recruitment, participants' basic information will be collected, and informed consent will be obtained. Surgery will be performed based on randomization results. Uniform surgical procedures will be ensured through centralized training.

Manufacture of Custom-Made Titanium and PEEK Cranioplasties

Using high-resolution CT scans and computer-assisted techniques, a 3D skull model will be generated. Both titanium mesh and PEEK cranioplasties will be custom-designed for each patient to restore structural integrity. Titanium meshes are shaped by compression into a mold, while PEEK implants are 3D printed, allowing precise matching to cranial defects.

Surgical Procedure

This multicenter study ensures standardized surgical techniques through centralized training. If cerebral swelling is evident, lumbar cisternal drainage will be performed. Shaving the patient's hair, washing the scalp, and skin preparation will minimize contamination. Scalp dissection and reflection will be carefully carried out to avoid dural tearing and bleeding, which will be managed by bipolar coagulation and hydrogen peroxide wash.

Custom-made implants will be placed and adjusted intraoperatively for a precise fit. Titanium or PEEK implants will be anchored with screws and a wound drain positioned for blood drainage. Layers of galea and skin will be sutured, and the drain will be removed approximately 3 days post-surgery when drainage subsides.

Outcomes

Primary Outcome

The primary outcome is the implant failure rate within 6 months, defined by infection or implant exposure necessitating removal.

Secondary Outcomes

Secondary outcomes include:

1. Complications within 6 months post-cranioplasty, such as seizures, hematoma, hydrocephalus, cerebrospinal fluid rhinorrhea, subgaleal effusion, and treatable superficial infections.

2. Neurological outcomes assessed by Glasgow Coma Scale (GCS) and Glasgow Outcome Scale (GOS), and cognitive function via Mini-Mental State Examination (MMSE).

3. Motor function evaluated using the Oxford Grading System.

4. Cerebral hemodynamics measured by transcranial Doppler sonography (TCDS).

5. Cosmetic outcomes self-assessed by patients and evaluated by neurosurgeons.

6. Total surgical costs over 6 months.

Data Collection

Experienced staff will collect baseline data, including neurological, cognitive, and cerebral hemodynamics assessments and imaging. Follow-up data will be collected at 3 and 6 months post-surgery. Data will be anonymized, transferred to assessors, and entered into an electronic database. Adverse events will be documented, and data recorded on collection forms in real time.

Data and Safety Monitoring

An independent Data Monitoring Committee (DMC) comprising neurosurgeons, neurologists, statisticians, and data analysts will monitor the trial's safety and efficacy annually, making necessary adjustments as required.

Statistical Analysis

All statistical analyses will be conducted using SPSS V.22. Continuous variables will be described as mean ± SD or median (range). Categorical variables will be defined as median (range). The primary outcome of implant failure rates and secondary outcomes of complication rates will be analyzed using the χ² test. Continuous parameters will be examined using t-tests or non-parametric tests like the Mann-Whitney U test. Pre-planned subgroup analysis will include age, subgaleal effusion, cranioplasty location, cerebral hemodynamics, and neurological function and applicable regression methods.

The study will generate robust evidence for comparing neurofunctional improvements and complication rates with different implant materials, aiding neurosurgeons in material selection for cranioplasty.

Patient and Public Involvement Statement

Patients and the public were not involved in the study’s design, recruitment, or conduct. Participants will be informed that they can contact the study team if they have emotional needs. Post-trial, a journal manuscript will provide feedback on the research results.

Ethics and Dissemination

All patients will be thoroughly informed about the implant materials, potential complications, and trial responsibilities, with informed consent obtained before participation. If cognitive impairment is present, next of kin will be informed. Potential adverse events, including infections, implant exposure, seizures, hydrocephalus, intracranial hematomas, and subgaleal effusions, will be documented. These complications are commonly associated with cranioplasty. Results will be shared through academic conferences, student theses, and peer-reviewed journals.

Discussion

Cranioplasty, using autologous bone or synthetic materials, is common in surgical procedures. Titanium mesh remains widely used despite higher complication rates, leading to the exploration of new materials like PEEK, which offers several advantages. However, limited high-quality studies constrain data availability. The PTCP study, the first multicenter, randomized controlled study, aims to provide robust evidence on the implant failure rates, complication rates, and neurological outcomes of different materials for cranioplasty. This research will assist neurosurge