Systematic evaluation of a holmium:yttrium-aluminum-garnet laser lithotripsy device with variable pulse peak power and pulse duration

Objective:The Holmium:yttrium-aluminum-garnet(Ho:YAG)laser is the standard lithotrite for ureteroscopy.This paper is to evaluate a Ho:YAG laser with a novel effect function in vitro,which allows a real-time variation of pulse duration and pulse peak power.Methods:Two types of phantom calculi with four degrees of hardness were made for fragmentation and retropulsion experiments.Fragmentation was analysed at 5(0.5 J/10 Hz),10(1 J/10 Hz),and 20(2 J/10 Hz)W in non-floating phantom calculi,retropulsion in an ureteral model at 10(1 J/10 Hz)and 20(2 J/10 Hz)W using floating phantom calculi.The effect function was set to 25%,50%,75%,and 100%of the maximum possible effect function at each power setting.Primary outcomes:fragmentation(mm^3),the distance of retropulsion(cm);
5 measurements for each trial.Results:An increase of the effect feature(25%vs.100%),i.e.,an increase of pulse peak power and decrease of pulse duration,improved Ho:YAG laser fragmentation.This effect was remarkable in soft stone composition,while there was a trend for improved fragmentation with an increase of the effect feature in hard stone composition.Retropulsion increased with increasing effect function,independently of stone composition.The major limitations of the study are the use of artificial stones and the in vitro setup.Conclusion:Changes in pulse duration and pulse peak power may lead to improved stone fragmentation,most prominently in soft stones,but also lead to increased retropulsion.This new effect function may enhance Ho:YAG laser fragmentation when maximum power output is limited or retropulsion is excluded.

Urinary bladder cancer as a late sequela of traumatic spinal cord injury

Background:Traumatic spinal cord injury(SCI)is also a combat-related injury that is increasing in modern warfare.The aim of this work is to inform medical experts regarding the different course of bladder cancer in able-bodied patients compared with SCI patients based on the latest medical scientific knowledge,and to present decision-making aids for the assessment of bladder cancer as a late sequela of traumatic SCI.Methods:A study conducted between January 1998 and December 2019 in the BG Trauma Hospital Hamburg formed the basis for the decision-making aids.Urinary bladder cancer was diagnosed in 40 out of 7396 treated outpatient and inpatient SCI patients.General patient information,latency period,age at initial diagnosis,type of bladder management and survival of SCI patients with bladder cancer were collected and analysed.T category,grading and tumor entity in these patients were compared with those in the general population.Relevant bladder cancer risk factors in SCI patients were analysed.Furthermore,relevant published literature was taken into consideration.Results:Initial diagnosis of urinary bladder cancer in SCI patients occurs at a mean age of 56.4 years(SD±10.7 years),i.e.,approximately 20 years earlier as compared with the general population.These bladder cancers are significantly more frequently muscle invasive(i.e.,T category≥T2)and present a higher grade at initial diagnosis.Furthermore,SCI patients show a significantly higher proportion of the more aggressive squamous cell carcinoma than that of the general population in areas not endemic for the tropical disease schistosomiasis.Consequently,the survival time is extremely unfavourable.A very important finding,for practical reasons is that,in the Hamburg study as well as in the literature,urinary bladder cancer is more frequently observed after 10 years or more of SCI.Based on these findings,a matrix was compiled where the various influencing factors,either for or against the recognition of an association between SCI and urinary bladder cancer,were weighted according to their relevance.Conclusions:The results showed that urinary bladder cancer in SCI patients differs considerably from that in ablebodied patients.The presented algorithm is an important aid in everyday clinical practice for assessing the correlation between SCI and bladder cancer.