A decade after the additive manufacturing boom: separating marketing, biomechanics and clinical evidence
Walk through the exhibit hall at any spine meeting and try counting the porous titanium cages. You’ll lose track quickly. Stryker cleared its Tritanium PL through the 510(k) pathway in 2016. Ten years later most of the big spine companies have a printed cage of their own, and plenty of surgeons reach for one without thinking twice. Whether patients are better off for it is a separate question, and the field has been slow to answer it.
The engineering case was always persuasive. Solid Ti-6Al-4V has an elastic modulus of roughly 117 GPa, many times stiffer than vertebral bone, which goes a long way toward explaining why older titanium cages had a reputation for sinking. PEEK solved the stiffness problem, but bone doesn’t bond to it. Printing let manufacturers build a lattice that behaves more like cancellous bone and that bone can grow into. Laratta and colleagues tested the idea in sheep, putting ungrafted printed titanium cages up against PEEK cages filled with iliac crest autograft. At four and eight weeks the titanium had integrated far better. Around the PEEK there was little bony contact and some localized fibrosis.¹
Patients are harder to study than sheep. In a retrospective single-center series of standalone LLIF, Adl Amini et al. looked at two separate groups. Patients scanned at about eight months showed 95.8% fusion with printed titanium against 62.5% with PEEK. In those scanned at about 19 months the numbers were 94.7% and 80.0%, no longer a significant difference.² Read plainly, titanium got there sooner, not more often.
The subsidence data favor titanium too, but they are thinner than the marketing suggests. Liu et al.’s 2024 meta-analysis in LLIF found an odds ratio of 0.25 versus PEEK, drawn from three non-randomized studies with 265 patients in total.³ Against titanium-coated PEEK, the comparator many hospitals actually stock, the edge disappears. A 2026 meta-analysis of TLIF studies put fusion at 91% versus 88% and subsidence at 19% versus 20%, with no meaningful radiographic or clinical differences at intermediate follow-up.⁴
What we still don’t have is a solid set of randomized trials with patient-reported outcomes and long follow-up. Most registered trials use imaging-based fusion as the primary endpoint, and some are post-market studies run by the manufacturer. Aesculap’s trial, which pits its printed cage against its own titanium-coated PEEK, isn’t due to finish until 2028.⁵
Meanwhile, the clearest predictors of failure have little to do with the cage material. Kim et al. reviewed L5-S1 TLIFs done with porous titanium cages and found subsidence rates in line with those published for PEEK. The patients whose cages subsided badly tended to have low Hounsfield units, smaller or more vertically placed cages, or endplates damaged during preparation.⁶ Those are problems of bone quality and technique.
A few other issues get less attention than they deserve. Titanium still produces artifact on CT, so judging fusion through a printed cage isn’t easy. “Porous titanium” also covers a wide range of designs, with different pore sizes, lattice geometries and surface treatments, so results from one company’s implant say little about another’s. And where printed cages carry a price premium, someone should be asking what it buys.
Printed titanium does integrate better, and custom implants have given surgeons options in complex cases they didn’t have before. For the routine degenerative fusion, though, nobody can yet show that it has changed pain, function or reoperation rates. After ten years and a great many implants, that is the trial worth funding.
###
References
- Laratta JL, Vivace BJ, López-Peña M, et al. 3D-printed titanium cages without bone graft outperform PEEK cages with autograft in an animal model. Spine J. 2022;22. doi:10.1016/j.spinee.2021.12.004
- Adl Amini D, Moser M, Oezel L, et al. Fusion assessment in standalone lateral lumbar interbody fusion: 3D-printed titanium versus polyetheretherketone (PEEK) cages. J Spine Surg. 2022;8(3). doi:10.21037/jss-22-17
- Liu SX, Zeng TH, Chen CM, et al. 3D-printed porous titanium versus polyetheretherketone cages in lateral lumbar interbody fusion: a systematic review and meta-analysis of subsidence. Front Med. 2024;11:1389533.
- Yu Y, Cho T, Liu J. Titanium-coated PEEK versus 3D-printed porous titanium cages in transforaminal lumbar interbody fusion: a meta-analysis. J Orthop. 2026. doi:10.1016/j.jor.2026.05.013
- Aesculap AG. Clinical Outcome and Fusion Rate of 3D Printed Interbody Fusion Cages and Titanium Coated PEEK Cages. ClinicalTrials.gov: NCT05237908.
- Kim DH, Kim SD, Kim JY, Hong JT, Hur JW. Subsidence after L5-S1 transforaminal lumbar interbody fusion using 3D-printed porous titanium interbody cage: a single-institution retrospective study. Turk Neurosurg.
Legal Disclaimer:
Content published on SPINEMarketGroup (thespinemarketgroup.com) is provided for informational purposes only and on an “as is” basis, without warranties of any kind. We do not guarantee the accuracy, completeness, legality, or reliability of any information, images, videos, links, or third-party materials featured on the site. Any views or claims expressed in contributed content or press releases belong to their respective authors or sources. For copyright concerns, factual corrections, or content-related complaints, please contact us directly for review.