Titanium Mesh Versus Polyetheretherketone (PEEK) in Cranioplasty: A Systematic Review and Meta-Analysis of Complications and Clinical Outcomes

This systematic review and meta-analysis comparing titanium and PEEK cranioplasty materials concludes that while titanium offers superior operative efficiency and a lower risk of postoperative infection, PEEK demonstrates lower exposure rates, suggesting that implant selection should be tailored to individual patient factors and surgical expertise.

The Gist

Imagine your skull is a sturdy, protective helmet for your brain. Sometimes, due to a severe injury or surgery, a piece of this helmet has to be taken off to let the brain swell safely without being crushed. Once the danger passes, doctors need to put a new piece of the helmet back on. This procedure is called cranioplasty.

For decades, doctors have debated: What is the best material to use for this new helmet piece?

This paper is a massive "report card" that looked at 38 different studies to compare the two most popular modern materials: Titanium Mesh (a metal grid) and PEEK (a high-tech, custom-molded plastic). They also looked at older methods like using the patient's own bone or acrylic cement.

Here is the breakdown of their findings, explained with some everyday analogies.

The Main Characters

1. Titanium Mesh: Think of this as the "Indestructible Metal Sheet." It's strong, cheap, and surgeons can bend it to fit the hole quickly. However, it's rigid and conducts heat (you might feel the sun on your head more).
2. PEEK: Think of this as the "Custom-Made Plastic Armor." It's molded perfectly to your head using 3D printing. It feels more like real bone, doesn't conduct heat, and looks great. But, it's expensive and can sometimes trap fluid underneath it.
3. Autologous Bone: This is the "Recycled Material." They take the bone they saved from your own head earlier. It's biologically perfect, but sometimes the body eats it away (resorbs) over time, or it gets infected.

The Big Showdown: What Did the Data Say?

The researchers found that there is no single "perfect" material. It's like choosing a car: a sports car is fast but gets less gas mileage; a truck is tough but heavy. Here is how they compared:

1. The Infection Battle (The "Bacteria War")

• The Finding: Titanium won this round.
• The Analogy: Imagine a fortress. The study found that the metal fortress (Titanium) was slightly harder for bacteria to invade compared to the plastic fortress (PEEK). The data showed a lower risk of infection with Titanium.
• Why it matters: If a patient is already at high risk for getting sick, Titanium might be the safer bet.

2. The "Leak" vs. The "Hole" (Complications)

This is where things get tricky. Every material has a different way of failing.

• Titanium's Weakness: The "Skin Erosion." Because metal is hard and sharp-edged, it can sometimes rub against the skin from the inside, causing the skin to wear thin and eventually poke through (exposure). It's like wearing a stiff, heavy coat that eventually chafes your skin raw.
• PEEK's Weakness: The "Fluid Pool." Because PEEK is smooth and doesn't bond as tightly to the body as metal, fluid can sometimes get trapped between the implant and the scalp. It's like a raincoat that fits perfectly but traps sweat underneath, creating a puddle that needs to be drained.
• Autologous Bone's Weakness: The "Melting Ice." Sometimes, the body treats the saved bone like a foreign object and slowly dissolves it (resorption), leaving a hole again.

3. The Surgery Speed (Operative Metrics)

• The Finding: Titanium is the "Fast Food" option.
• The Analogy: Putting in Titanium is like assembling a pre-cut puzzle; it goes together quickly. Putting in PEEK or the patient's own bone is like baking a custom cake from scratch; it takes much longer in the kitchen (the operating room).
• Why it matters: Shorter surgery time means less time under anesthesia and less blood loss. Titanium is the speed champion here.

4. The Look and Feel (Cosmetics & Function)

• The Finding: It's a Tie.
• The Analogy: Once the surgery is done and healed, patients generally look the same and feel the same regardless of which material was used. Whether you have a metal helmet or a plastic one, your brain recovers its function, and your head looks normal. The material choice doesn't change how smart you are or how your head looks in the mirror.

The Final Verdict: How to Choose?

The authors conclude that you can't just pick one material for everyone. It depends on the specific "story" of the patient:

• Choose Titanium if: You need the surgery done quickly, you are worried about infection, or the defect is in a tricky spot where speed matters. Just be aware that the skin might need extra care to prevent it from rubbing through.
• Choose PEEK if: You want the most natural look and feel, you are worried about the metal feeling cold or hot, and you are willing to pay more and accept a slightly higher risk of fluid buildup under the skin.
• Choose Your Own Bone if: It's available and healthy, but be prepared for the possibility that the body might try to "eat" it later, requiring a second surgery.

The Bottom Line

This paper tells us that Titanium is the "Infection Fighter" and "Speedster," while PEEK is the "Cosmetic Champion" with a risk of fluid traps.

There is no magic bullet. The best choice is a conversation between the surgeon and the patient, weighing the risk of infection against the risk of skin irritation, and deciding what matters most for that specific person's head.

Technical Summary

1. Problem Statement

Cranioplasty following decompressive craniectomy is essential for restoring cranial integrity, protecting the brain, and improving neurological function. However, the selection of the optimal implant material remains a subject of significant debate. While Titanium (Ti) mesh and Polyetheretherketone (PEEK) are the most widely used synthetic options, their comparative safety profiles, complication rates, and long-term clinical outcomes are inconsistent in existing literature.

• Key Issues: High complication rates (up to 40%) including infection, implant exposure, bone resorption (in autologous grafts), and subgaleal fluid collection.
• Knowledge Gap: Previous studies often lack direct head-to-head comparisons or suffer from heterogeneity in study design, preventing definitive conclusions regarding which material offers superior survival, lower infection risk, and better functional outcomes.

2. Methodology

The study adhered to the PRISMA 2020 guidelines and was registered in PROSPERO.

• Search Strategy: A comprehensive search was conducted across PubMed, Embase, Scopus, Web of Science, and the Cochrane Database of Systematic Reviews without language or date restrictions.
• Eligibility Criteria:
  • Inclusion: Comparative studies (RCTs, cohort, case-control) involving human patients undergoing cranioplasty, specifically comparing Titanium against PEEK, PMMA, autologous bone, or hydroxyapatite. Studies must report extractable data on complications, reoperation, or functional outcomes.
  • Exclusion: Case reports, reviews, animal studies, and non-comparative studies.
• Study Selection:
  • Initial records: 1,026.
  • After duplicate removal: 476 screened.
  • Full-text review: 78 articles.
  • Final Inclusion: 38 comparative studies (totaling 41 distinct cohorts/studies) were included for qualitative synthesis.
  • Meta-Analysis: Only 3 studies providing extractable dichotomous infection data for direct Titanium vs. PEEK comparison were included in the quantitative meta-analysis.
• Data Extraction & Analysis:
  • Two reviewers independently extracted data on demographics, surgical metrics, and outcomes.
  • Risk of Bias: Assessed using Joanna Briggs Institute (JBI) tools.
  • Statistical Analysis: A random-effects model (DerSimonian–Laird) was used to calculate pooled Odds Ratios (OR) for postoperative infection. Heterogeneity was assessed via $I^2$ statistics. Sensitivity analysis was performed by excluding a small-sample study (Shukla et al., 2024).

3. Key Contributions

This review provides the most comprehensive synthesis to date comparing Titanium and PEEK, while also contextualizing them against other materials (PMMA, Autologous Bone, Hydroxyapatite).

• Quantitative Synthesis: It is one of the few meta-analyses specifically quantifying the infection risk difference between Titanium and PEEK.
• Mechanism Differentiation: It clearly delineates the distinct failure mechanisms of different materials (e.g., mechanical exposure for Titanium vs. biological resorption for autologous bone vs. fluid collection for PEEK).
• Operative Efficiency: It highlights the trade-off between surgical time/efficiency and long-term complication profiles.

4. Key Results

A. Infection and Wound Complications (Primary Outcome)

• Meta-Analysis Finding: The pooled analysis demonstrated a significantly lower odds of postoperative infection with Titanium compared to PEEK (Random-effects model). This finding remained robust in sensitivity analysis.
• Exposure vs. Fluid:
  • Titanium: Associated with higher rates of implant exposure and skin erosion (rates reported up to 13.9–17.0%) due to mechanical pressure and scalp atrophy.
  • PEEK: Associated with significantly lower exposure rates (1.3–4.2%) but a markedly higher risk of subgaleal fluid collection (SFC) (Odds Ratio ~5.59 compared to Titanium).
• Comparison with Other Materials:
  • Autologous Bone: Highest risk of infection (up to 25.9% in some cohorts) and bone resorption, leading to high reoperation rates.
  • PMMA: Variable infection rates; some studies showed higher infection than Titanium, others lower. Generally associated with higher reoperation rates due to infection or poor contouring.
  • Hydroxyapatite (HA): Showed lower infection rates than Titanium in a specific RCT (7.7% vs. 37.5%), but data is limited.

B. Implant Survival and Revision

• Titanium: High biological stability but prone to mechanical failure (exposure).
• PEEK: Generally shows higher long-term survival rates regarding implant retention, as fluid collections rarely necessitate explantation compared to the skin breakdown seen with Titanium.
• Autologous Bone: High failure rate primarily driven by resorption rather than infection alone.

C. Operative Metrics

• Titanium: Consistently associated with shorter operative times and lower intraoperative blood loss compared to autologous bone (which requires donor site harvest) and often compared to PEEK or PMMA.
• PEEK: Custom 3D-printed PEEK can be time-efficient, but manual molding or complex fixation can extend surgery time.

D. Functional and Cosmetic Outcomes

• Neurological Recovery: Functional outcomes (GOS, mRS, GCS) were largely comparable across all materials. The restoration of cranial integrity itself appears to be the primary driver of neurological improvement, rather than the specific material.
• Cosmetic Satisfaction: Patient satisfaction and aesthetic scores were generally high and statistically similar across Titanium, PEEK, and Autologous bone.
  • Note: Titanium may be associated with long-term scalp atrophy (thinning), potentially affecting the cosmetic contour over time, whereas PEEK offers better radiolucency and thermal insulation.

5. Significance and Clinical Implications

• Individualized Selection: The study concludes that no single material is universally superior. Selection must be patient-specific:
  • Titanium may be preferred for patients with high infection risk (e.g., prior infection, compromised soft tissue) due to its lower infection rate and operative efficiency, provided the surgeon can manage the risk of exposure.
  • PEEK may be preferred for patients where wound stability is the primary concern or where radiation planning (radiolucency) is critical, accepting the risk of subgaleal fluid collection.
  • Autologous Bone is generally less favorable for large defects due to resorption and donor site morbidity, though it remains a gold standard in specific contexts.
• Future Directions: The authors emphasize the need for high-quality, prospective, multicenter RCTs with standardized outcome definitions (especially for infection and fluid collection) and longer follow-up periods to better assess time-dependent complications like exposure and resorption.

Limitations

• Heterogeneity: Significant variability in study designs (mostly retrospective), patient populations, and follow-up durations.
• Data Scarcity for Meta-Analysis: Only 3 studies were suitable for the quantitative meta-analysis of infection, limiting the statistical power for this specific comparison.
• Bias: Lack of blinding in many studies and potential publication bias.

Conclusion: Titanium cranioplasty offers superior infection resistance and operative efficiency but carries a higher risk of mechanical exposure. PEEK offers better wound stability and lower exposure rates but is associated with higher rates of subgaleal fluid collection. The choice of implant should be guided by the specific risk profile of the patient and the surgeon's expertise.