Carbon fiber-reinforced PEEK surpasses subtractive manufacturing reproducibility: systematic comparison of PAEK variants in high-temperature material extrusion for patient-specific implants

Material extrusion (MEX) of high-performance polymers typically yields lower dimensional performance than subtractive manufacturing, thereby limiting clinical applications. This study systematically compared MEX across polyaryletherketone (PAEK) variants, including polyetheretherketone (PEEK), polyetherketoneketone (PEKK), and CFR-PEEK, with subtractive milling and manual casting, using identical patient-specific cranial geometries. CFR-PEEK MEX achieved manufacturing reproducibility of 0.09 ± 0.05 mm root-mean-square error (RMSE), outperforming milled PEEK at 0.16 ± 0.05 mm ( p < 0.01), with fiber reinforcement suppressing edge-localized thermal distortion and achieving ± 0.3 mm spatial uniformity across 95 % of complex surfaces. PEKK MEX demonstrated 57 % higher manufacturing reproducibility than PEEK MEX (0.21 ± 0.05 mm versus 0.49 ± 0.02 mm RMSE), attributable to narrower thermal processing windows and higher glass transition temperature. Quasi-static biomechanical testing revealed controlled linear fractures at layer interfaces in MEX materials, with PEKK MEX maintaining structural integrity beyond 10 mm displacement (>1500 N), in contrast to the brittle stellate fragmentation observed in cast PMMA. All manufacturing methods met clinically acceptable dimensional thresholds for cranial reconstruction, demonstrating that point-of-care composite CFR-PEEK MEX can achieve dimensional performance comparable to established subtractive manufacturing workflows.