## 4 Discussion  
The independent replicates exhibited pore sizes averaging approximately 100 \(\upmu\)m, with some exceeding 400 \(\upmu\)m. Specifically, the average pore sizes for specimens S1, S2, and S3 were 95.39 \(\upmu\)m, 99.7 \(\upmu\)m, and 101.8 \(\upmu\)m, respectively. Visual inspection of sulfonated PEEK surfaces showed a uniform distribution of pores, as reflected in the histograms in Figure 3, which illustrate similar porosity patterns across replicates. Statistically significant differences in pore sizes were observed among the specimen types in the full range (Figure 4c). However, significance among the replicates decreased when the pore size range was narrowed (Figure 4a,b). Variations in average pore size are likely due to outliers from exceptionally large pores or imaging artifacts such as shadowing in ImageJ. The similarity in pore sizes between >100-400 \(\upmu\)m is particularly relevant, as pores within this range, especially those above 100 \(\upmu\)m and below 400 \(\upmu\)m, are considered optimal for promoting osteogenesis [7, 51, 54]. For context, cortical bone typically has pore sizes between 10 and 500 \(\upmu\)m, while cancellous bone ranges from 0.2 to 1 mm [57, 58]. The technique utilized for pore measurement was a 2D surface analysis only, which may overestimate or underestimate the actual functional topography. [PERSON] et al. examined osteointegration on titanium surfaces with pores of 100-200 \(\upmu\)m, 250-355 \(\upmu\)m, and 355-500 \(\upmu\)m, finding no significant differences in cell proliferation across these groups [40]. Nonetheless, all porous specimens exhibited greater ALP expression and calcium deposition than nonporous controls [40]. In a separate study, [PERSON] et al. used MC3T3-E1 cells to assess scaffolds with mean pore sizes from 85 \(\upmu\)m to 325 \(\upmu\)m, aiming to determine the effect on cell adhesion [43]. They found that scaffolds with 325 \(\upmu\)m pores had approximately 62% cell attachment after 24 and 48 h, while those with 120 \(\upmu\)m pores had 45% attachment at the same time points [43]. No significant differences were observed for scaffolds with 85 \(\upmu\)m, 164 \(\upmu\)m, or 190 \(\upmu\)m pores. Their findings suggest that larger pores enhance overall cell infiltration, whereas smaller pores promote higher initial cell attachment [43]. FTIR analysis examined the chemical changes in sfPEEK following hydrothermal treatment. As illustrated in Figure 1, the sulfonation of PEEK introduces SO3H groups onto its surface, which are subsequently removed during hydrothermal treatment. In the FTIR spectrum, a broad peak near 3400 cm\({}^{-1}\) indicates the presence of OH functional groups, while  
Figure 12: Fluorescent images of **(A)** sfPEEK with no bacteria, **(B)** sfPEEK-HT with no bacteria, **(C)** sfPEEK with bacteria, and **(D)** sfPEEK-HT with bacteria after 24 h of _S.ureus_ attachment. White circles indicate bacteria colonies. a smaller peak around 1050 cm\({}^{-1}\) corresponds to S=O vibrations [2; 29; 45]. These peaks appear with greater intensity in untreated samples than hydrothermally treated ones (Figures 5 and 6a,b), confirming the treatment's effective removal of residual sulfur groups. Contact angle measurements (Figure 7) further support this finding, as the sfPEEK-HT shows a significantly higher contact angle, indicating increased hydrophobicity due to the absence of OH groups [44]. At the same time, the literature remains divided on whether hydrophilic or hydrophobic surfaces better support protein and cellular adhesion [47; 59]. Additionally, in vivo studies will be conducted to investigate the impact of surface hydrophobicity on osseointegration. Mechanical testing showed significantly superior performance for the sfPEEK and sfPEEK-HT specimens compared to conventional smooth PEEK.