Comparison of outcomes between 3D-printed porous titanium alloy and polyetheretherketone cages for atlantoaxial intra-articular fusion in craniovertebral malformations

OBJECTIVE: The atlantoaxial intra-articular distraction and fusion technique involves intra-articular release, distraction, and cage implantation and is commonly used to treat craniovertebral bony malformations. Polyetheretherketone (PEEK) cages for C1-2 intra-articular fusion have been in use for over a decade. Three-dimensional printing is an emerging approach in spinal surgery, and several studies have explored 3D-printed porous titanium alloy (3DPT) cages for interbody fusion. However, there is limited research on their application and comparisons for C1-2 intra-articular fusion. In this study, the authors aimed to compare the outcomes of C1-2 intra-articular PEEK cages with those of 3DPT cages. METHODS: Clinical data from patients with craniovertebral anomalies treated with C1-2 intra-articular cage implantation were retrospectively analyzed. Midsagittal parameters were compared between PEEK and 3DPT and at 3 time points: preoperatively, postoperatively, and follow-up. Other assessments included clinical remission, reduction loss, fusion failure, cage micromotion, and screw-rod failure. Univariate comparisons were conducted. RESULTS: Records of 60 patients were reviewed, with a mean age of 43.75 ± 13.48 years; basilar invagination was the most common deformity. The 3DPT and PEEK cages demonstrated comparable immediate reduction effects. However, during follow-up, the 3DPT cage exhibited superior reduction maintenance, enhanced fusion rates, and reduced cage micromotion. Fusion rates were 100% and 80.6% in the 3DPT and PEEK groups, respectively. Fusion failure was associated with clinical nonremission, PEEK cage, deformity relapse, reduction loss, and cage micromotion, but was not associated with screw-rod construct failure. CONCLUSIONS: Fusion failure significantly undermines long-term outcomes. The 3DPT cage is a viable option for improving long-term results by minimizing loss of reduction, preventing fusion failure, and reducing cage micromotion.