4D-Printed Bioactive PEEK Cranioplasty Implants: Early Clinical and Radiological Outcomes Compared With Conventional 3D-Printed PEEK

BACKGROUND: Conventional 3D-printed polyetheretherketone (PEEK) implants are widely used for cranioplasty, but postoperative subgaleal fluid collection and temporal contour deformity remain concerns. This study compared early clinical and radiological outcomes between 4D-printed bioactive PEEK implants and conventional 3D-printed PEEK implants. METHODS: This retrospective cohort study included 62 adult patients undergoing unilateral cranioplasty, including 31 treated with 4D-printed bioactive PEEK implants and 31 treated with conventional 3D-printed PEEK implants. Outcomes included drainage duration, total drainage volume, subgaleal fluid collection at follow-up, temporal muscle collapse, cosmetic satisfaction, postoperative complications, and measurement reproducibility. Multivariable linear regression was used to evaluate factors associated with 3-month subgaleal fluid collection volume. RESULTS: The 4D-PEEK group had lower total drainage volume (97 mL [82-120] vs. 314 mL [227-337], P < 0.001) and shorter drainage duration (1 day [1-1] vs. 3 days [2-3], P < 0.001). Subgaleal fluid collection was lower in the 4D-PEEK group at 1 month (0 mL [0-2] vs. 14 mL [9-21], P < 0.001) and 3 months (0 mL [0-2] vs. 7 mL [3-12], P < 0.001). Radiographically detectable fluid collection at 3 months occurred in 4 patients (13%) and 19 patients (61%), respectively (P < 0.001). Temporal muscle collapse was observed in 1 patient (3.2%) in the 4D-PEEK group and 7 patients (23%) in the 3D-PEEK group (P = 0.053). Implant type remained independently associated with 3-month fluid collection volume (adjusted B = -5.4 mL; 95% CI, -7.8 to -3.0; P < 0.001). CONCLUSIONS: 4D-printed bioactive PEEK implants were associated with reduced postoperative drainage and less persistent subgaleal fluid collection. Larger prospective studies are needed to validate these findings.