A PEEK implant is a medical device made from polyetheretherketone, a high-performance plastic polymer that has become one of the most widely used alternatives to metal in modern surgery. Its appeal comes from a combination of traits that are rare in a single material: it bends and flexes at rates closer to natural bone than metal does, it does not interfere with CT or MRI scans the way titanium can, and the body generally tolerates it well without toxic or allergic reactions. Surgeons now use PEEK in spinal fusion cages, skull reconstruction plates, fracture-fixation hardware, and dental prosthetics, though the material has a significant limitation that researchers are still working to solve.
What Makes PEEK Different From Metal Implants
Most surgical implants have historically been made from metals, especially titanium and stainless steel. These metals are strong and biocompatible, but they are dramatically stiffer than bone. When a metal implant bears a load, its rigidity can shield the surrounding bone from normal mechanical stress. Over time, that shielded bone can weaken and thin, a phenomenon orthopedic surgeons call stress shielding. PEEK’s stiffness sits much closer to bone’s range, which means the surrounding bone still gets loaded and stimulated after surgery. A systematic review of dental implant studies found that PEEK and its composites produced less stress shielding than titanium or zirconia, resulting in higher stress and strain in the bone around the implant, which is actually what you want for long-term bone health.
That said, the mechanical picture is not perfectly simple. Pure PEEK has a stiffness of roughly 3.7 to 4.0 gigapascals, while human cortical bone ranges from about 7 to 30 gigapascals depending on location and direction of loading.1PubMed Central. Polyetheretherketone and Its Composites for Bone Replacement and Regeneration So pure PEEK is actually softer than bone in many situations, which limits its use in areas that bear heavy loads unless the material is reinforced. This is why you will often see “CFR-PEEK” in surgical literature: carbon fiber-reinforced PEEK, where short or continuous carbon fibers are mixed into the polymer to boost stiffness and strength into a range that can handle the demands of, say, a fractured femur or a spinal rod.
Where Surgeons Use PEEK Today
PEEK’s surgical footprint has expanded considerably since it was first cleared for implant use in the late 1990s. The largest single application is in spinal surgery, where PEEK cages are placed between vertebrae during fusion procedures to maintain disc height while new bone grows through and around the cage. A systematic review of PEEK cages in cervical spine fusion noted that their radiolucency and low stiffness make them attractive compared with titanium cages and bone graft, though the authors also flagged complications such as pseudoarthrosis (failure of the bone to fuse), subsidence (the cage sinking into the vertebral body), and cage migration.2The Spine Journal. Systematic review of PEEK cages in cervical spine fusion
In craniofacial surgery, PEEK has become a go-to material for cranioplasty, the repair of skull defects left by trauma, tumor removal, or decompressive surgery. Custom-designed implants are now 3D-printed to match the exact contours of a patient’s skull using preoperative CT scans and computer-aided design software. These patient-specific implants fit with a precision that off-the-shelf plates cannot match.3Egyptian Journal of Neurosurgery. Clinical evaluation of 3D PEEK implants for skull bone defects repair: a single center case serious An additive-manufacturing study demonstrated that fused filament fabrication can produce PEEK skull implants with adjustable thickness and complex geometry at lower processing costs than traditional milling.4PubMed Central. Additively manufactured polyether ether ketone (PEEK) skull implant as an alternative to titanium mesh in cranioplasty
In orthopedic and trauma surgery, carbon fiber-reinforced PEEK plates are used to fix fractures of the arm, wrist, and leg. A review of nine clinical studies found very high bone-union rates across CFR-PEEK plate groups, ranging from about 91 percent in distal femur fractures to 100 percent in upper-limb fractures, with low complication rates and no significant difference in outcomes compared to conventional metal plates.5PubMed Central. Fracture fixation in extremity trauma with carbon fiber-reinforced polyetheretherketone (CFR-PEEK) plates: evidence today
Dentistry has embraced PEEK as well, using it in removable partial denture frameworks, clasps, implant abutments, provisional restorations, and even occlusal splints.6PubMed Central. The use of PEEK in digital prosthodontics: A narrative review For patients with metal allergies or those who want a tooth-colored framework instead of a visible metal clasp, PEEK offers a practical alternative.7PubMed Central. Clinical Applications of Polyetheretherketone in Removable Dental Prostheses: Accuracy, Characteristics, and Performance
The Imaging Advantage
One of PEEK’s most compelling selling points is something you only appreciate after the surgery is over: it barely shows up on medical scans. Titanium implants create streak artifacts on CT scans and susceptibility artifacts on MRI, which can obscure the very anatomy the surgeon needs to monitor. If a patient with a titanium spinal implant develops a new symptom, the metal hardware can make it harder to see whether the bone has fused, whether a tumor has recurred, or whether adjacent structures are in trouble.
PEEK, by contrast, is radiolucent. A study comparing carbon fiber-reinforced PEEK with titanium implants in a thoracic spine phantom found a significant reduction in CT and MRI artifacts, leading to better interpretation of follow-up imaging and, for cancer patients, more precise radiation dose delivery.8PubMed Central. Carbon fiber-reinforced PEEK versus titanium implants: an in vitro comparison of susceptibility artifacts in CT and MR imaging In an oral oncology setting, titanium reconstruction plates with titanium screws caused roughly double the streak artifacts of PEEK plates on CT imaging.9Journal of Oral and Maxillofacial Surgery. Reduction of CT Artifacts Using Polyetheretherketone (PEEK), Polyetherketoneketone (PEKK), Polyphenylsulfone (PPSU), and Polyethylene (PE) Reconstruction Plates in Oral Oncology For anyone who needs ongoing surveillance after surgery, especially cancer patients requiring repeated scanning, that difference is clinically meaningful.
The Osseointegration Problem
Here is where the story gets more complicated. PEEK is biocompatible in the sense that the body does not reject it or mount a significant inflammatory response against it. But biocompatible and bioactive are two different things. Unmodified PEEK has a smooth, hydrophobic surface that bone cells do not readily latch onto. Instead of growing directly into or onto the implant surface, the body often forms a thin layer of fibrous tissue around it, a kind of scar capsule that separates the implant from living bone.10PubMed. Porous PEEK improves the bone-implant interface compared to plasma-sprayed titanium coating on PEEK This poor osseointegration is the single biggest biological limitation of PEEK as an implant material.11PubMed Central. Bioinspired Modifications of PEEK Implants for Bone Tissue Engineering
The clinical consequence shows up most clearly in spinal fusion data. A meta-analysis comparing PEEK and titanium interbody cages in lumbar fusion found that PEEK cages had about 38 percent lower odds of achieving solid fusion compared with titanium cages.12PubMed Central. Polyetheretherketone Versus Titanium Cages for Posterior Lumbar Interbody Fusion: Meta-Analysis and Review of the Literature A separate meta-analysis found higher rates of subsidence and revision surgery with PEEK cages in the lumbar spine, though in the cervical spine no difference was seen between the two materials.13PubMed. Titanium Cages versus Polyetheretherketone Cages in Interbody Fusions: A Meta-Analysis of Clinical and Radiographic Outcomes One study looking specifically at lateral lumbar interbody fusion found that while early follow-up showed similar subsidence between PEEK and titanium, statistical differences favoring titanium emerged by the eight-to-twelve-week mark and persisted at one year.14PubMed. PEEK versus titanium cages in lateral lumbar interbody fusion: a comparative analysis of subsidence
These findings do not mean PEEK spinal cages fail frequently in absolute terms; many patients do achieve successful fusion. But the gap compared to titanium is real and has driven a significant research effort to modify PEEK’s surface.
How Researchers Are Fixing the Surface
A large body of materials science work is focused on making PEEK’s surface more welcoming to bone cells. The general strategy is to coat or texture the surface with substances the body recognizes as bone-like, or to roughen the surface so cells have something to grip.
One approach involves coating PEEK with hydroxyapatite, the mineral that makes up much of real bone. A recent study engineered a multilayer composite by growing a hydroxyapatite coating on PEEK through a specialized chemical process and found that osteoblast adhesion improved dramatically compared with unmodified PEEK.15Polymer. Surface-engineered PEEK-HAp composites for osteoblast growth: An initial step toward the development a bone implant material Another technique uses phosphonation to change PEEK’s surface chemistry before applying the hydroxyapatite layer, improving coating adhesion and osseointegration potential.16PubMed. Surface phosphonation enhances hydroxyapatite coating adhesion on polyetheretherketone and its osseointegration potential
Titanium dioxide coatings represent another promising avenue. In a canine cervical spine model, TiOâ‚‚-coated PEEK cages achieved a 60 percent fusion rate by manual palpation and 40 percent by micro-CT imaging, compared with zero percent fusion for uncoated PEEK in both assessments. The bone-to-implant contact ratio was also tenfold higher in the coated group.17PLOS ONE. In vivo experimental study of anterior cervical fusion using bioactive polyetheretherketone in a canine model These are animal studies, and the numbers will differ in humans, but the direction of the effect is consistent across the literature: surface modification meaningfully improves PEEK’s ability to bond with living bone.
Bacterial Biofilm and Infection Risk
Whenever a foreign object is placed inside the body, there is a risk that bacteria will colonize its surface and form a biofilm, a sticky microbial community that is difficult for antibiotics and the immune system to penetrate. This matters for any implant, and the question is whether PEEK’s polymer surface handles bacteria differently from titanium.
The evidence here is mixed and depends on which bacterial species you test. One dental study found that machined PEEK was no more susceptible to bacterial colonization than commercially pure titanium or titanium alloy for most tested organisms, and one species actually grew better on titanium than on any of the other surfaces.18PubMed Central. Biofilm formation on polyetheretherketone and titanium surfaces However, a separate comparative study found that the majority of tested bacterial strains showed higher adhesion to PEEK than to titanium, with the notable exception again being one species that preferred titanium.19PubMed Central. Comparison of Titanium and PEEK Medical Plastic Implant Materials for Their Bacterial Biofilm Formation Properties
Surface texture plays a role: roughened or blasted PEEK tends to collect more bacteria than smooth machined PEEK. In clinical practice, infection rates for PEEK implants do not appear to be dramatically different from metal implants, but this is an area where the in-vitro findings suggest caution, particularly for implants placed in contaminated or infection-prone surgical fields. Researchers have explored incorporating antimicrobial agents, such as silver nanoparticles, onto 3D-printed PEEK surfaces to address this concern.20PubMed. AgNPs-decorated 3D printed PEEK implant for infection control and bone repair
3D Printing and Patient-Specific Implants
One of the developments accelerating PEEK’s adoption is the ability to 3D-print it into patient-specific shapes. Traditional manufacturing of PEEK implants involved CNC machining, carving the implant from a solid block using computer-controlled cutting tools. This works well for simple geometries but becomes expensive and wasteful for complex, one-of-a-kind shapes. Fused filament fabrication, a form of 3D printing where a PEEK filament is melted and deposited layer by layer, allows construction of nearly any geometry that a surgeon and engineer can design on a computer.21PubMed Central. Patient-Specific Surgical Implants Made of 3D Printed PEEK: Material, Technology, and Scope of Surgical Application
The workflow typically starts with a high-resolution CT scan of the patient. Software converts the imaging data into a three-dimensional model of the defect, and engineers design an implant that fills the gap while matching the surrounding anatomy. The design file goes to a PEEK-capable printer, and the finished implant is sterilized before surgery. For cranioplasty, this means a skull plate that follows the exact curves and thickness of the missing bone rather than a flat mesh that has to be bent and trimmed in the operating room.
Printing PEEK is technically demanding because the material has a melting point around 343°C and requires carefully controlled chamber temperatures to avoid warping and delamination between layers. Not all 3D printers can handle it, and the machines that can are considerably more expensive than standard filament printers. Still, the ability to produce implants on-site or at a nearby facility, without long lead times from a specialty manufacturer, has real advantages for surgical planning and patient turnaround.
What Happens When a PEEK Implant Needs to Come Out
One underappreciated aspect of any implant material is how it behaves during retrieval if a revision surgery becomes necessary. A study examining PEEK rods retrieved from patients who had undergone posterior spinal fusion found no cases of rod fracture or pedicle screw fracture. The rods did show surface scratching and impressions from the set screws and pedicle screw saddles, which is expected from the mechanical contact during service. In two patients, small amounts of PEEK debris were observed in adjacent tissues at the sites where scratching and burnishing were most evident.22PubMed Central. Retrieval analysis of PEEK rods for posterior fusion and motion preservation
The debris question is worth noting. Titanium implants also shed wear particles, and the biological response to those metallic particles has been studied for decades. PEEK particle generation appears to be modest in clinical practice, but very long-term data on the tissue response to polymer debris remains limited. Sterilization does not seem to degrade the material in a meaningful way: testing of carbon fiber-reinforced PEEK found that neither steam autoclaving nor gamma radiation sterilization caused significant changes to the material’s hardness, stiffness, or friction characteristics.23PubMed. The influence of sterilization processes on the micromechanical properties of carbon fiber-reinforced PEEK composites for bone implant applications
Cost Compared to Other Implant Materials
PEEK implants, especially custom 3D-printed ones, tend to cost more upfront than some alternatives. A comparative cost study of cranioplasty materials at a single center found that the average cost of a PEEK cranioplasty was roughly CAD $27,000, compared with about CAD $18,000 for manually shaped titanium and CAD $14,000 for autogenous bone flap replacement. When statistical outliers were removed, PEEK still cost about CAD $13,000 more than manually shaped titanium.24PubMed Central. Comparative Cost-Effectiveness of Cranioplasty Implants Much of this premium comes from the cost of the custom design process and the specialized printing or machining required.
Whether that premium is justified depends on the clinical situation. For a patient who needs ongoing cancer surveillance with frequent CT scans, the imaging clarity PEEK provides could reduce the need for additional imaging studies or exploratory procedures. For a patient with a known metal allergy, PEEK may be the only practical option. And for complex skull defects where surgical time matters, a perfectly fitted 3D-printed PEEK plate can reduce the hours spent in the operating room shaping a titanium mesh by hand, partially offsetting the material cost through shorter anesthesia and OR time.
Animal Studies and the Road Ahead
Much of the evidence on next-generation PEEK modifications comes from animal models, particularly canine spinal fusion studies. In one such study, PEEK connecting rods were compared to titanium rods in posterior lumbar fusion in dogs. The PEEK group showed biomechanical evidence of better bone-graft fusion, with decreased stiffness and decreased displacement at the fusion site, and histological analysis confirmed significant fusion mass in both groups.25PubMed Central. A study to compare the efficacy of polyether ether ketone rod device with titanium devices in posterior spinal fusion in a canine model These results are encouraging because they suggest that PEEK’s lower stiffness may actually promote healthier remodeling of the bone graft over time, even if early fusion rates lag behind titanium.
The broader trajectory of PEEK research is toward composite and surface-engineered versions that keep the material’s mechanical and imaging advantages while closing the osseointegration gap. If the hydroxyapatite coatings, titanium dioxide treatments, and porous surface architectures being studied in labs today translate successfully into clinical products, the next generation of PEEK implants could offer the best of both worlds: bone-friendly stiffness, clean imaging, and a surface that living bone actually wants to grow into. For now, the material occupies a well-defined and expanding niche, one where surgeons accept certain trade-offs in exchange for properties no metal can replicate.