Interbody cage material is one of the more recurring debates in spinal procurement, and it rarely has a single right answer — it depends on the case, the surgeon's technique, and what the operating team values most between imaging clarity and subsidence resistance.
The question behind the question
Both PEEK (per ASTM F2026) and titanium (per ASTM F136) are established, widely used interbody cage materials with strong clinical track records. The real decision variables are modulus of elasticity, radiographic behaviour, and how each performs at the bone-implant interface under load.
Modulus of elasticity: closer to bone, or stronger than bone?
PEEK's elastic modulus (roughly 3–4 GPa) sits far closer to cortical and especially cancellous bone than titanium's (~110 GPa). In theory, a closer modulus match reduces stress shielding at the endplate interface. Titanium cages, by contrast, offer significantly higher compressive strength and a track record of reliable osseointegration when the surface is appropriately textured or porous-coated.
Imaging and fusion assessment
This is where the two materials diverge most visibly. PEEK is radiolucent — it does not obscure the fusion mass on X-ray or CT, which lets the surgeon assess bony fusion directly through the cage on follow-up imaging. Solid titanium cages are radiopaque and can obscure that same view, sometimes making fusion assessment more difficult without CT and specific windowing.
Subsidence risk
Cage subsidence — sinking into the vertebral endplate — is influenced by end-plate preparation, cage footprint and bone quality at least as much as by material choice. Some clinical literature has associated certain titanium cage designs with lower subsidence rates, attributed partly to surface friction and osseointegrative coatings, while other studies show comparable outcomes when footprint and endplate contact are optimised regardless of material. It remains an active area of clinical research rather than a settled question.
Titanium-coated PEEK: splitting the difference
A growing category of cages applies a porous titanium coating to a PEEK core — aiming to combine PEEK's bone-like modulus and radiolucency with titanium's favourable bone-apposition surface characteristics. Early clinical data is promising, though longer-term comparative outcomes are still accumulating.
A procurement-team view
For hospital procurement, the practical answer is to stock both material families and let surgeon preference and case-specific factors — revision surgery, deformity correction, patient bone quality — drive the selection at the point of use, rather than standardising on a single material across every spinal case.