Comparison of ureteoroscopy and laser stone fragmentation between Holmium: YAG laser with MOSES versus non-MOSES technology: a prospective single-center propensity score-matched analysis using similar laser settings

Abstract

Background:

In vitro studies have shown that the holmium Modulated Optics Enhancement Systems (MOSES) technology can lead to an increase in the efficacy of lithotripsy and a reduction of retropulsion, but clinical evidence comparing it to non-MOSES technology is still scarce. We did a comparison of ureteoroscopy and laser stone fragmentation (URSL) between Holmium:YAG laser with MOSES versus non-MOSES technologies.

Methods:

Patient data and outcomes were prospectively collected and analyzed regarding patient demographics, stone parameters, and clinical outcomes. Patients undergoing URSL with standard holmium laser without MOSES technology (Group 1) were compared to holmium laser with MOSES (Group 2) using the same clinical laser settings (0.4–1 J, 20–40 Hz) with dusting and pop-dusting technique. The independent t-test, Mann–Whitney U test, and Chi-squared test were used, with a p-value of < 0.05 as significant. Given the different sizes of the cohorts, we performed a propensity score 1:1 matched analysis.

Results:

A total of 206 patients (1:1 matched) with a male:female ratio of 94:112 and a median age of 56 (range: 39–68) years were analyzed. Groups 1 and 2 were matched for ureteric stones (27.7% and 22.3%, p = 0.42), pre-stenting (37% and 35%, p = 0.66), the mean number of stones (1.76 ± 1.3) and (1.82 ± 1.4, p = 0.73), and ureteral access sheath use (37% and 35%, p = 0.77) respectively.

While there was no significant statistical difference in clinical outcomes, the stone size was slightly larger in Group 2, 14.8 ± 10.8 mm vs 11.7 ± 8.0 mm, for a lower operative time 42.7 ± 30.6 min versus 48.5 ± 25 min, lower perioperative complication rates 3.9% versus 4.9% and a higher stone-free rate 90.3% versus 87.4%.

Conclusion:

While the use of MOSES technology was slightly beneficial for the treatment of stones in terms of clinical outcomes, this was not statistically significant. As this debate continues, there is a need for high-quality randomized studies to show if there is a true difference in these outcomes.

Plain language summary

We compare the outcomes of ureteroscopy and laser stone fragmentation (URSL), using Holmium:YAG laser with MOSES vs Non-MOSES technology: It is a prospective single-centre propensity score-matched analysis using similar laser settings

It is a single-centre propensity score-matched analysis using similar laser settings. While the use of MOSES technology was slightly beneficial for treatment of stones in terms of clinical outcomes, this was not statistically significant. As this debate continues, there is a need for high quality randomized studies to show if there is a true difference in these outcomes.

Introduction

Due to the high prevalence of kidney stone disease (KSD), there have been constant advances in laser technology to enhance treatment efficacy. ¹ However, Holmium:YAG laser is still considered the gold standard for laser lithotripsy in KSD.^2,3 Other than traditional Holmium:YAG lasers, the Modulated Optics Enhancement Systems (MOSES) technology uses “pulse modulation” to divide the emitted energy into two pulses. The first pulse forms microbubbles in the water, allowing the second pulse of energy to pass through these previously formed bubbles directly affecting the stone, and causing fragmentation of the stone.^4,5 In vitro studies have demonstrated that using Holmium:YAG lasers with MOSES technology, compared to conventional Holmium:YAG lasers, can enhance lithotripsy efficacy and reduce retropulsion.^6,7 However, despite these promising in vitro results, clinical studies have shown similar outcomes in stone-free rates (SFRs), operating time, safety, and efficacy between the two technologies. Nevertheless, the clinical evidence remains limited.^8–12

We compared ureteroscopy and laser stone fragmentation (URSL) with a Holmium:YAG laser with MOSES versus non-MOSES technology.

Methods

Our ureteroscopy outcomes were registered as an audit (6901) with the hospital’s “Clinical Effectiveness and Audit” department. Patient data and outcomes were prospectively collected and analyzed regarding patient demographics, stone parameters, and clinical outcomes. Patients undergoing URSL with standard high-power holmium laser (100 W) without MOSES technology (Group 1) were compared to 60 W holmium laser with MOSES (Group 2) using the same clinical laser settings (0.4–1 J, 20–40 Hz) with dusting and pop-dusting technique.

Given the different sizes of the cohorts, we performed a propensity score 1:1 matching analysis to assess the effect of MOSES technology on SFR, matching 103 cases treated with MOSES technology with 103 patients of the same age and gender treated with the non-MOSES laser, using the same laser settings. Patients were allocated to the MOSES or non-MOSES groups based on the availability of technology at the time of surgery. Patients were matched for ureteric and renal stones, pre-stenting, mean number of stones, and ureteral access sheath (UAS) use.

A non-contrast computed tomography (CTKUB) was performed as a diagnostic imaging. Patients with positive preoperative urine cultures were treated appropriately according to the sensitivity analysis. All patients were pre-assessed in a dedicated anesthesiologic-led clinic. A pre-surgical brief was held on the day of the procedure as per the World Health Organization (WHO) checklist with the theater and recovery team. A protocol-based procedure was done for all patients under general anesthetic.

A rigid Ureteroscopy (URS) was performed using a 4.5F or 6F Wolf or Storz semi-rigid ureteroscope over a working wire after initial cystoscopy and safety wire placement. A UAS was employed for renal stones at the surgeon’s discretion (9F/11F or 12F/14F Cook Flexor sheath). Afterward, a flexible ureteroscopy (Storz FlexX2) and laser stone treatment (Lumenis, Ltd.) were performed either with a high-power holmium laser (100 W) without MOSES technology (Group 1) or a 60 W holmium laser with MOSES (Group 2). Both lasers were used with the same clinical laser settings (0.4–1 J, 20–40 Hz) with dusting and pop-dusting techniques. Fragments were removed using the Cook Ngage stone extractor, by Cook Medical of Bloomington, IN. Basketing was employed for stone removal in cases where it was deemed necessary by the surgeon. A 6F ureteral stent was inserted postoperatively as needed, at surgeons’ discretion.

The primary outcome of this study was the SFR. The secondary outcomes included operative time, perioperative complication rates, and the necessity of postoperative stent placement.

All patients were followed up in our stone clinic postoperatively with postoperative imaging to assess for stone-free status and symptoms. Stone-free status was defined as the absence of residual fragments >2 mm on postoperative imaging (XR KUB or non-contrast CT) performed at 2–3 months.

Inclusion criteria were patients undergoing URSL for ureteric or renal stones, with preoperative imaging confirming stone presence. Exclusion criteria were incomplete patient data or loss of follow-up.

Analysis was performed regarding patient demographics, stone location, stone size, and density as well as SFR, laser time, operating time, length of stay, perioperative, and postoperative complications. Data were collected using Microsoft Excel 2016 (Microsoft, Redmond, WA, USA).

Statistical analysis was performed with SPSS version 26 (IBM, Armonk, NY, USA). The independent t-test, Mann–Whitney U test, and Chi-squared test were used, with a p-value of <0.05 as significant.

Results

A total of 206 patients (1:1 matched) with a male:female ratio of 94:112 and a median age of 56 (range: 39–68) years were analyzed (Table 1). Groups 1 and 2 were matched for ureteric stones (27.7% and 22.3%, p = 0.42), pre-stenting (37% and 35%, p = 0.66), and mean number of stones (1.76 ± 1.3 and 1.82 ± 1.4, p = 0.73) as well as UAS use (37% and 35%, p = 0.77), respectively.

Table 1.

Comparison of non-MOSES and MOSES groups.

	Non-MOSES group (n = 103)	MOSES group (n = 103)	p
Previous endoscopic procedures	34 (33%)	27 (26.2%)	0.29
Recurrent Urinary tract infections	18 (17.5%)	17 (16.5%)	0.85
BMI	30.3 ± 9.9	28.5 ± 6.2	0.006
Preoperative stent	39 (37.9%)	36 (35%)	0.66
Stone number	1.76 ± 1.3	1.82 ± 1.4	0.73
Total stone length	11.7 ± 8.0	14.8 ± 10.8	0.14
Stone location
Vesicoureteric junction (VUJ)	4	3	0.7
Distal ureter	10	8	0.62
Mid ureter	2	8	0.05
Proximal ureter	12	7	0.23
Pelviureteric junction (PUJ)	4	2	0.41
Lower pole	22	33	0.08
Mid pole	12	9	0.49
Upper pole	9	12	0.49
Renal pelvis	28	21	0.25
Operative time	48.5 ± 25	42.7 ± 30.6	0.13
Ureteral access sheath	38 (36.9%)	36 (35%)	0.77
Postoperative stent	60 (58.3%)	64 (62.1%)	0.57
Complications	5 (4.9%)	4 (3.9%)	0.73
	Sepsis 2	Sepsis 3
	Hematuria 1	UTI 1
	Anesthetic reaction 1
	Renal abscess 1
Stone-free	90 (87.4%)	93 (90.3%)	0.51

The independent t-test, Mann–Whitney U test, and Chi-squared test were used, with a p-value of <0.05 as significant.

MOSES, Modulated Optics Enhancement Systems.

Renal stone positions were as follows: Vesicoureteric junction (VUJ) (4 in non-MOSES, 3 in MOSES), distal ureter (10 in non-MOSES, 8 in MOSES), mid-ureter (2 in non-MOSES, 8 in MOSES), proximal ureter (12 in non-MOSES, 7 in MOSES), pelviureteric junction (PUJ) (4 in non-MOSES, 2 in MOSES), lower pole (LP) (22 in non-MOSES, 33 in MOSES), mid-pole (MP) (12 in non-MOSES, 9 in MOSES), upper pole (UP) (9 in non-MOSES, 12 in MOSES), and renal pelvis (28 in non-MOSES, 21 in MOSES).

While there was no significant statistical difference in clinical outcomes, the stone size was slightly larger in Group 2, 14.8 ± 10.8 mm versus 11.7 ± 8.0 mm (p = 0.14), for a lower operative time 42.7 ± 30.6 min versus 48.5 ± 25 min (p = 0.13), lower perioperative complication rates 3.9% versus 4.9% (p = 0.73), and a higher SFR 90.3% versus 87.4% (p = 0.51). The complications were all Clavien grade I/II and included sepsis (n = 5), urinary tract infection (n = 1), renal abscess (n = 1), hematuria (n = 1), and anesthetic reaction (n = 1).

Discussion

Since its introduction, Holmium:YAG laser lithotripsy has become the gold standard for treating renal and ureteric stones worldwide.^13,14 This development has enabled ureteroscopy to largely replace shockwave lithotripsy for the treatment of upper urinary tract stones, significantly improving SFR. ¹⁵

To further increase the effectiveness of laser lithotripsy, research is being conducted in two main areas: creating new laser sources and/or improving Holmium YAG’s ability to deliver energy. One of the most recent advancements in this field is the incorporation of laser pulse modulation into Holmium:YAG lasers using MOSES. In vitro experiments have shown that MOSES technology significantly reduces retropulsion. ³ This has led to the assumption of achieving faster stone disintegration and lesser operating times. ⁶ However, clinical data supporting this hypothesis remain controversial. A modest number of clinical studies have been conducted internationally in recent years, yielding mixed results. ⁸

We evaluated 206 cases treated by a single surgeon using Holmium:YAG laser either with or without MOSES technology using the same laser settings. A propensity score 1:1 matching analysis was performed for ureteric stones, pre-stenting, mean number of stones, and UAS use, respectively. We found no significant differences in the clinical outcomes including operative time, perioperative complication rates, SFRs, and postoperative stent, although all these metrics slightly favored the MOSES group.

There are a limited number of studies comparing high-powered Holmium:YAG lasers to lasers using the MOSES technology in a clinical setting. Ibrahim et al. conducted a prospective double-blinded randomized trial for patients undergoing holmium laser lithotripsy either with regular high power or MOSES modes using the Lumenis 120W generator with 200 Moses D/F/L fibers. Both patients and surgeons were blinded to the laser mode. In total, 72 cases were analyzed. MOSES mode resulted in significantly lower fragmentation/pulverization time (21.1 min vs 14.2 min; p = 0.03), procedural time (50.9 min vs 41.1 min, p = 0.03), and retropulsion (mean grade was 1.0 vs 0.5, p = 0.01). However, there were no significant differences in laser working time (7.4 min vs 6.1 min, p > 0.05), total energy applied to the stones (11.1 kJ vs 10.8 kJ, p > 0.05), intraoperative complications (11.1% vs 8.3%, p > 0.05), and success rate after 3 months (83.3% vs 88.4%, p > 0.05). ¹⁶

Mullerad et al. compared procedures performed with the Lumenis^® High-power Holmium Laser (120H) in regular mode to the same laser using MOSES technology, using a questionnaire filled out by the surgeons immediately after surgery. In total, 5 surgeons ranked 34 procedures, 11 without, and 23 with the MOSES technology. Although the surgeons rated MOSES technology to be subjectively better, there was no statistical significance in the clinical outcomes, such as SFR, laser working time, or energy used. ⁹

Similar to our findings, Knoedler et al. found no significant difference in procedural time (43.5–32.1 min vs 39.8–24.6 min, p = 0.436), fragmentation/dusting time (20.5–25.3 min vs 17.1–16.1 min, p = 0.430), lasing time (7.5–11.1 min vs 6.7–7.9 min, p = 0.570), the total energy used (5.1–6.7 kJ vs 3.8–4.8 kJ, p = 0.093), complications (6.4% vs 6.1%, p = 0.936), or SFRs (52.3% vs 65.3%, p = 0.143) in patients treated with MOSES technology compared with the regular mode with the Lumenis Pulse P120H holmium laser, with 176 cases from a database were analyzed. MOSES was utilized in 110 cases and regular mode in 66 of the cases. ¹¹

A recent meta-analysis including one randomized controlled trial and six non-randomized studies with a total of 910 patients showed that MOSES mode was associated with significantly lower operation time (SMD = − 0.43; 95% CI − 0.79 to − 0.08, p = 0.016). ¹⁷ However, this meta-analysis also included studies comparing laser lithotripsy with MOSES technology to low-power holmium laser lithotripsy, which could explain the significant difference in operating time.

This is a single-center single-surgeon study. To our knowledge, this is the largest series comparing a high-power holmium laser to a high-power laser using MOSES technology. Patients in both groups were treated with the same laser settings, and the same instruments and equipment apart from the laser. All patients followed the same standardized pathways in terms of preoperative assessment and postoperative care. Despite the retrospective nature of this study data from consecutive patients were collected prospectively and analyzed by independent operators to prevent bias. Furthermore, prosperity matching was performed to further eliminate bias.

We acknowledge that being a single-center study might be a limitation. However, the surgeries being performed by an experienced single surgeon ensures comparability between the groups. However, one of the limitations of this study is the variability in stone characteristics and patient backgrounds. There was a slight difference in stone location and BMI, with BMI being the only statistically different variable (30.3 ± 9.9 in the non-MOSES group vs 28.5 ± 6.2 in the MOSES group, p = 0.006). When comparing stone location for renal stones (PUJ, LP, MP, UP, renal pelvis), the non-MOSES group had 75 patients, and the MOSES group had 77 patients. Specifically comparing LP stones, no significant difference in outcomes (operative time, SFR, or complications) was noted. This suggests that the trend favoring MOSES technology in certain cases may not be significantly impacted by stone location. Furthermore, this study’s descriptive nature and the lack of assessment for lasering time and total laser energy are limitations.

Another limitation of this study is its study design and its sample size. Although our study included 206 patients, this number may still be insufficient to detect small but potentially clinically meaningful differences in SFRs between the groups. The lack of significant differences in SFRs observed in this study could be attributed to the limited sample size. This limitation underscores the need for larger, prospective, multi-center randomized controlled trials to validate our findings.

Conclusion

While the use of MOSES technology was slightly beneficial for the treatment of stones in terms of clinical outcomes, this was not statistically significant. As this debate continues, there is a need for high-quality randomized studies to show if there is a true difference in these outcomes.