Subgroup-specific estimates revealed a modest benefit for biological augmentation (MD = 3.65) versus a non-significant deficit for structural (MD = −2.53), with the interaction test approaching significance (Q = 3.83, df = 1, p = 0.050), indicating potential superiority of biological approaches at this interval, though tempered by high within-group variability.
By the 60-month follow-up, a borderline significant reduction in progression risk emerged, with a pooled RR of 0.37 (95% CI: 0.14 to 1.02; Z = −1.93; p = 0.054; Figure 15 ).
This GLMM-based sensitivity analysis aligns closely with the primary results, reinforcing a non-significant early trend and a stronger long-term protective effect against radiological progression, with the 60-month finding achieving statistical significance in the OR model ( p < 0.001) compared to borderline significance in the RR model ( p = 0.054).
Biological augmentation maintained a positive trend (MD = 5.04), while structural augmentation showed no advantage (MD = −2.29); however, the interaction test was non-significant (Q = 1.59, df = 1, p = 0.207), indicating no robust evidence of differential efficacy between groups at this extended time point. 3.4.
GLMM-based sensitivity analysis corroborates the primary results, indicating a borderline non-significant protective effect of biological augmentation against conversion to THA.
This near-significant finding indicates emerging long-term benefits, with the lower RR indicating a potential halving of progression risk, though the upper CI approaching unity cautions against overinterpretation.