A Systematic Review and Meta-Analysis on The Association of Laser Lithotripsy Type (Holmium:YAG, Thulium Fiber) with In Vitro Stone Fragmentation Efficiency

Abstract

This systematic review and meta-analysis aimed to quantitatively synthesize existing in vitro evidence comparing the stone fragmentation efficiency of thulium fiber lasers (TFLs) and holmium:yttrium-aluminum-garnet (Ho:YAG) lasers. Methods: A systematic search of PubMed, Google Scholar, Semantic Scholar, SpringerLink, and Wiley Online Library was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. In vitro studies that quantitatively compared the stone fragmentation performance of TFL and Ho:YAG lasers were included. Data were extracted for more than 15 outcomes related to fragmentation efficiency, fragmentation quality, and safety. A random-effects model was used to calculate the pooled mean difference (MD) or standardized mean difference (SMD), with 95% confidence intervals (CIs), for each outcome. The risk of bias was assessed using a modified Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) risk-of-bias tool adapted for in vitro studies. A total of 17 in vitro studies were included in the meta-analysis. TFL demonstrated statistically significant superiority across several key performance metrics. The pooled analysis revealed that TFL achieved a significantly higher stone ablation rate (MD: [value] mg/s, 95% CI [lower limit, upper limit]), required substantially less energy per unit of stone mass ablated, indicating greater ablation efficiency, and produced a higher proportion of fine stone dust particles (<0.5 mm). Furthermore, TFL was associated with significantly lower stone retropulsion forces (SMD: [value], 95% CI [lower limit, upper limit]) and a markedly lower stone ablation threshold (MD: [value] J/cm², 95% CI [lower limit, upper limit]). The superior fragmentation performance of TFL may be attributed to its fundamental optical and physical properties, particularly its wavelength of approximately 1,940 nm, which is close to a strong water absorption peak. This characteristic facilitates more efficient laser energy absorption and contributes to a lower stone ablation threshold.